-
حرية الوصول المقاله
1 - ارزیابی اقتصادی و سیاست های کنترل آلودگی هوا ناشی از حمل و نقل: مورد تهران
جمشید پژویان علی مقیمی نیاآلودگی هوا که در حال حاضر یکی از عمده ترین مشکلات شهر تهران است به عنوان یک پیامد خارجی منفی هزینه هایی را بر اقتصادکشور تحمیل می کند. این هزینه ها که بعضاً قابل محاسبه نیز نم یباشد، در بلندمدت بر مشکلات زیست محیطی کشور افزوده و شرایطرا جهت دستیابی به توسعه پایدار دشوار أکثرآلودگی هوا که در حال حاضر یکی از عمده ترین مشکلات شهر تهران است به عنوان یک پیامد خارجی منفی هزینه هایی را بر اقتصادکشور تحمیل می کند. این هزینه ها که بعضاً قابل محاسبه نیز نم یباشد، در بلندمدت بر مشکلات زیست محیطی کشور افزوده و شرایطرا جهت دستیابی به توسعه پایدار دشوار خواهد ساخت. بدین لحاظ می بایست با کنترل و کاهش آلودگی هوا، زمین ههای لازم را جهتایجاد بسترهای مناسب رشد و توسعه اقتصادی فراهم نمود. کنترل آلودگی هوا در دو محور قابل ارزیابی است. محور اول ایجاد ضابطه وکنترل از سوی سیاستگذار است و محور دوم برقراری مالیا تهای زیست محیطی را در برم یگیرد. با استفاده از برآوردهای انجام شدهتوسط الگویی که آلودگی هوای ناشی از حمل و نقل را برای تهران مورد تجزیه و تحلیل قرار م یدهد، به این نتیجه م یرسیم کهتقاضای مسافت یک کالای کم کشش است که ناشی از پایین بودن قیمت بنزین در تهران م یباشد. نتایج حاصل از برآوردهای انجامشده پس از برقراری مالیات های زیست محیطی (مالیات بر قیمت بنزین و مسافت و مالیات بر اتومبیل) نیز بیانگر این است که با توجهبه کم کشش بودن تقاضای مسافت طی شده، برقراری این نوع مالیات ها صرفاً برای اهداف درآمدی دولت مفید است، در حالی کهاهداف پیگویی یعنی کاهش آلودگی از طریق کاهش تقاضا توسط مصرف کنندگان با برقراری این نوع مالیات ها نتایج رضایت بخشی رابه دنبال نخواهد داشت. تفاصيل المقالة -
حرية الوصول المقاله
2 - Applicability of diffraction elastic constants to rationalize anisotropic broadening of X-ray diffraction line profiles from deformed metals
Debtanu Ghosh Sujay Munshi Apurba Kanti Deb Partha ChatterjeeA simple method, to rationalize anisotropic X-ray line widths of deformed FCC metallic samples is presented. The method is based on normalized Diffraction Elastic Constant ratio (DECR) within the framework of Stokes Wilson approximation and Gaussian microstrain distribu أکثرA simple method, to rationalize anisotropic X-ray line widths of deformed FCC metallic samples is presented. The method is based on normalized Diffraction Elastic Constant ratio (DECR) within the framework of Stokes Wilson approximation and Gaussian microstrain distribution. The observed dispersion in classical Williamson-Hall plot was significantly reduced if DECR based correction was applied to the integral breadths. Classical grain interaction models such as the Reuss and Reuss-Voigt average (Neerfeld-Hill) models were used to calculate the elastic constants of deformed polycrystals of Aluminium and Copper. It is observed that if non-uniform microstrains are present in the sample (mostly in the case of dislocated crystals) then the Reuss model is more appropriate than the Reuss-Voigt average model and is observed in the case of filed or ball-milled samples of Cu and Al. The non-linearity in the anisotropy corrected Williamson-Hall is indicative of line widening caused by the dislocation. تفاصيل المقالة -
حرية الوصول المقاله
3 - Elastic moduli of some rare-earth doped tellurite glasses
Raouf El-Mallawany Samir A. Yousef Abdelhamid El-Shaer Hanan A. ElabdSamarium oxide (Sm2O3) and ytterbium oxide (Yb2O3) doped tungsten-tellurite glasses (TWSm), (TWYb) in the forms of 80 (TeO2) - (20-x) (WO3) - x (Sm2O3) and 80 (TeO2) - (20-x) (WO3) - x (Yb2O3) with x = 0, 1.0, 2.0, 3.0, 4.0 and 5.0 mol% were prepared by the melt-quenchi أکثرSamarium oxide (Sm2O3) and ytterbium oxide (Yb2O3) doped tungsten-tellurite glasses (TWSm), (TWYb) in the forms of 80 (TeO2) - (20-x) (WO3) - x (Sm2O3) and 80 (TeO2) - (20-x) (WO3) - x (Yb2O3) with x = 0, 1.0, 2.0, 3.0, 4.0 and 5.0 mol% were prepared by the melt-quenching technique. The XRD analysis for the two prepared glass systems verified the samples’ amorphous nature. The glass density ( ρ ) was measured by the Archimedes method. Both ( ρ ) and the molar volume (VM) of the two prepared systems showed an increase with increasing the concentrations of dopants Sm3+ and Yb3+. Longitudinal VL and shear VS wave velocities were measured at 5 MHz frequency using the pulse-echo technique. Longitudinal (L), shear (G), bulk (K), and Young’s moduli ( E ) have been founded. Moreover, Poisson’s (σ), Debye temperature (θD), softening temperature (TS), micro-hardness (H) have been founded for every glass sample. Elastic moduli showed an increase with increasing dopants concentration of (Sm2O3) or (Yb2O3). Moreover, the bulk modulus of (TWSm) glasses was higher than (TWYb) glasses. Mechanical properties of (TWSm) and (TWYb) are crucial parameter in manufacturing optical fibers. تفاصيل المقالة -
حرية الوصول المقاله
4 - Influence of argon gas flow on mechanical and electrical properties of sputtered titanium nitride thin films
Kaykhosrow Khojier Hadi Savaloni Ebrahim Shokrai Zohreh Dehghani Naser Zare DehnaviAbstractTitanium nitrides have good mechanical, tribological, electrical, biomedical, and optical properties; therefore, they are used to harden and protect cutting and sliding surfaces, as semiconductor devices, and as a nontoxic exterior for biomedical applications. T أکثرAbstractTitanium nitrides have good mechanical, tribological, electrical, biomedical, and optical properties; therefore, they are used to harden and protect cutting and sliding surfaces, as semiconductor devices, and as a nontoxic exterior for biomedical applications. The dependence of the mechanical and electrical properties of titanium nitride thin films deposited on silicon substrates by direct-current reactive magnetron sputtering technique on argon gas flow (in the range of 8 to 20 sccm) was investigated. The crystallographic structure of the films was studied by X-ray diffraction (XRD), while surface morphology was studied using atomic force microscopy (AFM). Mechanical and electrical properties of these films were investigated by nanoindentation test and a four-point probe instrument, respectively. The XRD patterns showed titanium nitride (TiN) formation with a face-centered cubic structure for all samples. It was also observed that (111) crystallographic direction was the preferred orientation for TiN thin films which became more pronounced with increasing argon gas flow. The AFM images showed a granular structure for TiN layers. The hardness, crystallite/grain size (obtained from XRD and AFM), and surface roughness increased with the flow of argon gas, while elastic modulus and dislocation density in the films decreased. The study on electrical properties showed that the dependence of voltage with current for all samples was linear, and film resistivity was increased with argon gas flow. تفاصيل المقالة -
حرية الوصول المقاله
5 - Mechanical properties of CaN, SrN, and BaN compounds by density functional theory
Homa Sadat Sharifzadeh Sima Sadat Sharifzadeh Faramarz Kanjouri Amirhosein EsmailianAbstractUsing density functional theory, a systematic study of the elastic properties of CaN, SrN, and BaN compounds is performed. As a result, the optimized lattice parameters and independent elastic constants are calculated within the generalized gradient approximatio أکثرAbstractUsing density functional theory, a systematic study of the elastic properties of CaN, SrN, and BaN compounds is performed. As a result, the optimized lattice parameters and independent elastic constants are calculated within the generalized gradient approximation. We have also derived bulk and shear moduli, Young’s moduli, Poisson’s ratio, and brittle/ductile behavior for CaN, SrN, and BaN. The estimated anisotropy parameter, A, shows that SrN has higher degree of elastic isotropy in comparison to CaN and BaN. تفاصيل المقالة -
حرية الوصول المقاله
6 - Finite element formulation for the free vibration analysis of embedded double-walled carbon nanotubes based on nonlocal Timoshenko beam theory
Milad Hemmatnezhad Reza AnsariAbstractThe present paper is concerned with the free vibration analysis of double-walled carbon nanotubes embedded in an elastic medium and based on Eringen's nonlocal elasticity theory. The effects of the transverse shear deformation and rotary inertia are included acc أکثرAbstractThe present paper is concerned with the free vibration analysis of double-walled carbon nanotubes embedded in an elastic medium and based on Eringen's nonlocal elasticity theory. The effects of the transverse shear deformation and rotary inertia are included according to the Timoshenko beam theory. The governing equations of motion which are coupled with each other via the van der Waals interlayer forces have been derived using Hamilton's principle. The thermal effect is also incorporated into the formulation. Using the statically exact beam element with displacement fields based on the first order shear deformation theory, the finite element method is employed to discretize the coupled governing equations which are then solved to find the natural frequencies. The effects of the small scale parameter, boundary conditions, thermal effect, changes in material constant of the surrounding elastic medium, and geometric parameters on the vibration characteristics are investigated. Furthermore, our analysis includes nonlocal double-walled carbon nanotubes with different boundary conditions between inner and outer tubes which seem to be scarcely considered in the literature, and the corresponding given results for this case can be considered as a benchmark for further studies. Comparison of the present numerical results with those from the open literature shows an excellent agreement. تفاصيل المقالة -
حرية الوصول المقاله
7 - Determination of elastic constants of Inconel-625 superalloy, using laser-based ultrasonic
Anita ShuklaAbstractThis paper deals with the determination of the elastic constants of Inconel-625 from the analysis of laser-generated ultrasonic bulk waves. A pulsed Nd/YAG laser (1064 nm) is used for ultrasonic generation in a thick stepped Inconel-625 sample, and a He–Ne laser أکثرAbstractThis paper deals with the determination of the elastic constants of Inconel-625 from the analysis of laser-generated ultrasonic bulk waves. A pulsed Nd/YAG laser (1064 nm) is used for ultrasonic generation in a thick stepped Inconel-625 sample, and a He–Ne laser is used for heterodyne detection of the laser-generated signals. Ultrasonic signals obtained at epicenter and at off-epicenter position of the detection points are analyzed using wavelet transforms. Here, the identification of pressure as well as shear waves and the estimation of their velocities are done successfully. From the estimated velocities, the elastic constants (Young’s modulus, shear modulus, bulk modulus, Lames constant and Poisson’s ratio) are calculated. The agreement of these constants with the standard values confirms the identification of shear waves at off-epicenter position. The work presented in this paper brings out the applicability of the study of laser-generated bulk waves for the determination of elastic constants of any bulk material. تفاصيل المقالة -
حرية الوصول المقاله
8 - High-pressure and temperature-induced structural, elastic, and thermodynamical properties of strontium chalcogenides
Dinesh Varshney S. Jain S. Shriya R. KhenataAbstractPressure- and temperature-dependent mechanical, elastic, and thermodynamical properties of rock salt to CsCl structures in semiconducting SrX (X = O, S, Se, and Te) chalcogenides are presented based on model interatomic interaction potential with emphasis on cha أکثرAbstractPressure- and temperature-dependent mechanical, elastic, and thermodynamical properties of rock salt to CsCl structures in semiconducting SrX (X = O, S, Se, and Te) chalcogenides are presented based on model interatomic interaction potential with emphasis on charge transfer interactions, covalency effect, and zero point energy effects apart from long-range Coulomb, short-range overlap repulsion extended and van der Waals interactions. The developed potential with non-central forces validates the Cauchy discrepancy among elastic constants. The volume collapse (VP/V0) in terms of compressions in SrX at higher pressure indicates the mechanical stiffening of lattice. The expansion of SrX lattice is inferred from steep increase in VT/V0 and is attributed to thermal softening of SrX lattice. We also present the results for the temperature-dependent behaviors of hardness, heat capacity, and thermal expansion coefficient. From the Pugh’s ratio (ϕ = BT/GH), the Poisson’s ratio (ν) and the Cauchy’s pressure (C12–C44), we classify SrO as ductile but SrS, SrSe, and SrTe are brittle material. To our knowledge these are the first quantitative theoretical prediction of the pressure and temperature dependence of mechanical stiffening, thermally softening, and brittle nature of SrX (X = O, S, Se, and Te) and still await experimental confirmations. تفاصيل المقالة -
حرية الوصول المقاله
9 - Effect of temperature dependence ultrasonic velocities and attenuation of GaP nanowires
Pramod Kumar YadawaAbstractThe higher order elastic constants of the hexagonal wurtzite crystal structure of GaP nanowires have been evaluated using Lennard-Jones potential model at room temperature. The ultrasonic velocity increases with the temperature along particular orientation with أکثرAbstractThe higher order elastic constants of the hexagonal wurtzite crystal structure of GaP nanowires have been evaluated using Lennard-Jones potential model at room temperature. The ultrasonic velocity increases with the temperature along particular orientation with the unique axis of crystals. Temperature variation of the thermal relaxation time and Debye average velocities is also calculated along the same orientation. The temperature dependency of the ultrasonic properties is discussed in correlation with elastic, thermal and electrical properties. It has been found that the thermal conductivity is the main contributor to the behaviour of ultrasonic attenuation as a function of temperature and the responsible cause of attenuation is phonon–phonon interaction. The mechanical properties of GaP nanowires at low temperature are better than at room temperature, because at low temperature it has low ultrasonic velocity and ultrasonic attenuation. A particularly interesting case is GaP, which is the only (Ga, In)-V semiconductor with an indirect gap in the bulk phase, and are indispensable in modern microelectronic industries. تفاصيل المقالة -
حرية الوصول المقاله
10 - Elastic and thermodynamical properties of cubic (3C) silicon carbide under high pressure and high temperature
Dinesh Varshney S. Shriya M. Varshney N. Singh R. KhenataAbstractPressure-dependent first-order phase transition, mechanical, elastic, and thermodynamical properties of cubic zinc blende to rock-salt structures in 3C silicon carbide (SiC) are presented. An effective interatomic interaction potential for SiC is formulated. The أکثرAbstractPressure-dependent first-order phase transition, mechanical, elastic, and thermodynamical properties of cubic zinc blende to rock-salt structures in 3C silicon carbide (SiC) are presented. An effective interatomic interaction potential for SiC is formulated. The potential for SiC incorporates long-range Coulomb, charge transfer interactions, covalency effect, Hafemeister and Flygare type short-range overlap repulsion extended up to the second-neighbour ions, van der Waals interactions and zero point energy effects. The developed potential including many body non-central forces validates the Cauchy discrepancy successfully to explain the high-pressure structural transition, and associated volume collapse. The 3C SiC ceramics lattice infers mechanical stiffening, thermal softening, and ductile (brittle) nature from the pressure (temperature) dependent elastic constants behaviour. To our knowledge, these are the first quantitative theoretical predictions of the pressure and temperature dependence of mechanical and thermodynamical properties explicitly the mechanical stiffening, thermally softening, and brittle/ductile nature of 3C SiC and still awaits experimental confirmations. تفاصيل المقالة -
حرية الوصول المقاله
11 - Differential Characteristics of Efficient Frontiers in DEA with Weight Restrictions
S. SohraieeThe non-differentiability and implicit definition of boundary of production possibility set (PPS) in data envelopment analysis (DEA) are two important difficulties for obtaining directional characteristics, including different elasticity measures and marginal rates of s أکثرThe non-differentiability and implicit definition of boundary of production possibility set (PPS) in data envelopment analysis (DEA) are two important difficulties for obtaining directional characteristics, including different elasticity measures and marginal rates of substitution. Also, imposing weight restrictions in DEA models have some shortcomings and misunderstandings. In this paper we utilize the core concept of directional derivative theorem to calculate different elasticity measures in DEA models with weight restrictions. Some theorems have been proved in order to overcome the problem. تفاصيل المقالة -
حرية الوصول المقاله
12 - بررسی تاثیر مقدار رطوبت و درصد تراکم اولیه بر مقاومت فشاری و مدول الاستیسیته دو نوع خاک رسی و رس ماسه ای
جواد احدیان امین سالم‌نیا محمود کریمیاز جمله پارامترهایی که نشان دهنده رفتار خاک در برابر تنش های وارده است، مقاومت فشاری و مدول الاستیسته خاک می باشد. با افزایش مقاومت-فشاری ظرفیت باربری خاک افزایش می یابد. مدول الاستیسیته یک خاک نمایانگر میزان پتانسیل تغییر شکل خاک می باشد. در این پژوهش چگونگی تثبیت خاک أکثراز جمله پارامترهایی که نشان دهنده رفتار خاک در برابر تنش های وارده است، مقاومت فشاری و مدول الاستیسته خاک می باشد. با افزایش مقاومت-فشاری ظرفیت باربری خاک افزایش می یابد. مدول الاستیسیته یک خاک نمایانگر میزان پتانسیل تغییر شکل خاک می باشد. در این پژوهش چگونگی تثبیت خاک های رسی مسئله دار به کمک ماسه مورد مطالعه انجام گرفته است. بدین منظور نمونه های خاک رسی و رسی- ماسه ای در رطوبت و تراکم های مختلف ساخته شده و مورد آزمایش تک محوری قرار گرفتند. رطوبت ها شامل رطوبت بهینه، دو درصد کمتر، چهار درصد کمتر، دو درصد بیشتر و چهار درصد بیشتر می باشند. از طرفی این نمونه ها در تراکم های 85، 95 و 100 درصد ساخته شدند. با انجام آزمایش تک محوری، مقاومت فشاری و مدول الاستیسیته برای تمامی نمونه ها محاسبه شد. پس از بررسی و تحلیل نتایج آزمایش ها مشخص گردید که با افزایش رطوبت مقاومت فشاری در تمامی نمونه های رسی و رس- ماسه کاهش می یابد. اما باید به این نکته توجه نمود که شدت کاهش مقاومت فشاری در نمونه های رس- ماسه بیشتر از نمونه های رسی است؛ به گونه ای که، با تغییر رطوبت از چهار درصد کمتر از رطوبت بهینه به چهار درصد بیشتر از رطوبت بهینه در نمونه های رس مقدار مقاومت فشاری به طور متوسط 84 درصد و در نمونه های رس- ماسه ای 93 درصد در تمامی تراکم ها کاهش می یابد. از طرفی بر اساس نتایج به دست آمده معلوم گردید که مقدار مدول الاستیسیته در تراکم 100 درصد و در رطوبت 13 درصد با افزایش ماسه حدود 51 درصد کاهش می یابد. همچنین مشخص شد که کاهش مدول الاستیسیته با افزایش ماسه در تمامی تراکم ها روند مشابهی را به همراه دارد. تفاصيل المقالة -
حرية الوصول المقاله
13 - ویژگی های رئولوژیکی، فیزیکوشیمیایی و حسی ماست کم چرب پری بیوتیک حاوی اینولین، پلی دکستروز و کربوکسی متیل سلولز
سمیه عباسی اصل زهرا لطیفی نفیسه محمدی کرتلاییدر طی یک دهه گذشته مصرف محصولات غذایی بدون چربی و کمچرب گسترش زیادی پیدا کرده است، به این دلیل که بین مصرف چربی و بیماری‌هایی از جمله چاقی، بیماری‌های قلبی و عروقی مانند تصلب شرائین و سرطان ارتباط وجود دارد. بنابراین صنعت غذا با تقاضای روز افزونی برای کاهش مقدار چربی أکثردر طی یک دهه گذشته مصرف محصولات غذایی بدون چربی و کمچرب گسترش زیادی پیدا کرده است، به این دلیل که بین مصرف چربی و بیماری‌هایی از جمله چاقی، بیماری‌های قلبی و عروقی مانند تصلب شرائین و سرطان ارتباط وجود دارد. بنابراین صنعت غذا با تقاضای روز افزونی برای کاهش مقدار چربی در محصولات غذایی روبرو است ولی کاهش چربی، ویژگی‌های حسی و رئولوژیکی را به گونه‌ای منفی تحت تاثیر قرار میدهد. از طرف دیگر فیبرهای پری‌بیوتیک مانند اینولین و پلی‌دکستروز، علاوه بر داشتن خواص چربی‌سوزی دارای مزایای تغذیه‌ای-درمانی بالایی می‌باشند. مواد و روش‌ها: در این پژوهش ماست کم چرب پری‌بیوتیک با استفاده از اینولین (صفر، 2 و 3 درصد)، پلی‌دکستروز (صفر، 2 و 3درصد) و کربوکسی‌متیل‌سلولز (صفر و 5/0 درصد) به صورت ترکیبی اینولین-کربوکسی‌متیل‌سلولز و پلی‌دکستروز- کربوکسی‌متیل-سلولز انجام تولید شد.یافته‌ها: نتایج نشان دادند میزان آباندازی با افزایش غلظت اینولین و پلی‌دکستروز کاهش پیدا کرد. در این میان، افزودن غلظت ثابتی از کربوکسی‌متیل‌سلولز به نمونه‌های مختلف حاوی اینولین و کربوکسی متیل سلولز باعث کاهش بیشتر آباندازی شد. که بر pH و اسیدیته اثر غیرمعنی داری داشت. بررسی ویژگی‌های رئولوژیکی نشان داد که افزودن اینولین و پلی‌دکستروز سبب افزایش ویسکوزیته ظاهری، مدول ذخیره و مدول افت ماست کمچرب می‌شود و افزودن غلظت ثابتی از کربوکسی‌متیل‌سلولز باعث بهبود هرچه بیشتر ویژگی‌های رئولوژیکی می‌شود. یافته‌های آماری ارزیابی حسی ماست کمچرب نشان دادکه افزودن اینولین و پلی-دکستروز در کنار غلظت ثابتی از کربوکسی‌متیل‌سلولز باعث بهبود پذیرش کلی ماست کمچرب می‌شود. تیمار برتر ماست کم چرب حاوی پلی دکستروز 3 درصد + کربوکسی متیل سلولز 5/0 درصد بود. تفاصيل المقالة -
حرية الوصول المقاله
14 - بررسی خصوصیات ویسکوالاستیک کیک اسفنجی غنی‌شده با پودر سیب
فخرالدین صالحی مهدی کاشانی نژادمقدمه: سیب یک منبع غنی از فیبر و پلی فنول‌ها می‌باشد. به منظور بررسی اثر جایگزینی پودر سیب با آرد گندم بر خواص ویسکوالاستیک کیک اسفنجی آزمون رهایی تنشانجام گرفت. مواد و روش‌ها: ابتدا سیب زرد در شرایط بهینه خشک و آسیاب شد و سپس پودر سیب جهت غنی‌سازی کیک اسفنجی در پنج سطح أکثرمقدمه: سیب یک منبع غنی از فیبر و پلی فنول‌ها می‌باشد. به منظور بررسی اثر جایگزینی پودر سیب با آرد گندم بر خواص ویسکوالاستیک کیک اسفنجی آزمون رهایی تنشانجام گرفت. مواد و روش‌ها: ابتدا سیب زرد در شرایط بهینه خشک و آسیاب شد و سپس پودر سیب جهت غنی‌سازی کیک اسفنجی در پنج سطح 0، 5، 10، 15 و 20 درصد (وزنی/وزنی) به عنوان جایگزین آرد گندم در فرمولاسیون کیک استفاده شد. پس از آماده‌سازی نمونه، آزمایش رهایی تنش با استفاده از دستگاه بافت سنج در طی دوره نگهداری انجام و ضرایب مدل پلگ-نورمند و ماکسول تعمیم‌یافته محاسبه شد. یافته‌ها: نتایج نشان‌داد با افزایش درصد جایگزینی پودر سیب و زمان نگهداری، مقادیر نیروی اولیه و نیروی تعادلی افزایش می‌یابند. پارامترهای مدل پلگ-نورمند شامل k1 و k2 با گذشت زمان کاهش یافت که نشان از کاهش الاستیسیته کیک با گذشت زمان می‌باشد. کیک‌ها رفتار جامد ویسکوالاستیک از خود نشان داده و با افزایش درصد جایگزینی، مجموع نیروهای کاهشی (F1+F2 +F3) مدل ماکسول تعمیم‌یافته افزایش یافت که نشان‌دهنده کاهش الاستیسیته است. نتیجه‌گیری: نتایج مدلسازی داده‌های آزمایشگاهی رهایی تنش با مدلهای پلگ نورمند و ماکسول تعمیم‌یافته نشان‌داد که مدل ماکسول تعمیم‌یافته کارایی بیشتری جهت بررسی خصوصیات ویسکوالاستیک کیک اسفنجی غنی‌شده با پودر سیب دارد. تفاصيل المقالة -
حرية الوصول المقاله
15 - بررسی اثر صمغ‌های گوار و زانتان بر خصوصیات ویسکوالاستیکی کیک اسفنجی بدون گلوتن با استفاده از آزمون رهایی تنش
هادی باقری عبدالستار عوض صوفیان مهران اعلمیمقدمه: با توجه به نیاز تغذیه ای بیماران سلیاکی به یک رژیم غذایی فاقد گلوتن، مطالعه در مورد تولید و بهبود محصولات بدون گلوتن افزایش یافته است. با توجه به برخی از مشکلات کیفی مانند حجم پایین و بافت ضعیف در محصولات بدون گلوتن نظیر کیک برنجی، استفاده از ترکیبات بهبود دهنده أکثرمقدمه: با توجه به نیاز تغذیه ای بیماران سلیاکی به یک رژیم غذایی فاقد گلوتن، مطالعه در مورد تولید و بهبود محصولات بدون گلوتن افزایش یافته است. با توجه به برخی از مشکلات کیفی مانند حجم پایین و بافت ضعیف در محصولات بدون گلوتن نظیر کیک برنجی، استفاده از ترکیبات بهبود دهنده مانند هیدروکلوئیدها که خواص ویسکوالاستیک گلوتن را شبیه سازی می‌کنند، ضروری به نظر می رسد. از آنجا که گلوتن به عنوان یک ترکیب ویسکوالاستیک شناخته می شود و با توجه به عدم حضور گلوتن در کیک برنجی و استفاده از هیدروکلوئید ها که منجر به تغییر خصوصیات ویسکوالاستیک خواهد گردید، بنابراین مطالعه رفتار ویسکوالاستیک کیک برنجی بدون گلوتن حاوی هیدروکلوئید ها ضرروری به نظر می رسد. مواد و روش‌ها: دراین مطالعه اثر صمغ های گوار و زانتان بر خصوصیات ویسکوالاستیکی کیک برنجی بدون گلوتن با استفاده از آزمون رهایی تنش مورد مطالعه قرار گرفت و سپس توسط دو مدل پلک- نورمند و ماکسول تعمیم یافته مورد مدل سازی قرار گرفت. آنالیز آماری داده ها با استفاده از آنالیز واریانس یک طرفه و به منظور مقایسه میانگین ها از آزمون دانکن در سطح 5 درصد استفاده شد. یافته ها: نتایج نشان داد که با افزایش غلظت صمغ های گوار و زانتان، مقدار F0،K1،K2و پارامتر های مدل ماکسول کاهش یافت. این بدین معنی است که با افزودن صمغ گوار و زانتان نرخ کاهش نیروی اولیه افزایش یافت، بنابراین رفتار کیک حاوی صمغ، بیشتر متمایل به رفتار شبه مایع می باشد. با توجه به SSEو R2 مدل می توان بیان کرد که مدل پلگ- نورمند نیز می تواند به شکلی مناسب رفتار تنش ویسکوالاستیک کیک بدون گلوتن را در طول زمان توجیه نماید اما نسبت به مدل ماکسول از اعتبار پائین تری برخوردار است. نتیجه گیری: خصوصیات ویسکوالاستیکی کیک بدون گلوتن حاوی صمغ گوار و زانتان بهبود یافته و رفتار کیک حاوی صمغ متمایل به رفتار شبه مایع گردید. تفاصيل المقالة -
حرية الوصول المقاله
16 - Particle Size Distribution and Viscoelastic Behavior of French Dressing Containing Two Types of Commercial Waxy Maize Starches
M Mizani M. Yaghoti Moghaddam M. Alimi M. SalehifarEmulsion stability, viscoelastic rheological properties and particle size distribution of French dressing samples formulated with two types of commercial modified starch have been investigated. The product’s usual thickening agents, xanthan and guar gum, were 100% أکثرEmulsion stability, viscoelastic rheological properties and particle size distribution of French dressing samples formulated with two types of commercial modified starch have been investigated. The product’s usual thickening agents, xanthan and guar gum, were 100% substituted by (2, 2.2%) of acetylated distarch adipate (ADA) and hydroxypropylated distarch phosphate (HDP) from waxy maize starch. The samples with 2% hydroxypropylated distarch phosphate starch showed the minimum emulsion stability (<95% after three months of storage) and were eliminated from further studies and the other three samples along with the control were selected for particle size distributions and dynamic rheological properties analysis. The sample formulated with 2.2% of HDP starch showed a better storage stability (higher zero shear viscosity), deformability (γLVE) and greater texture strength (G’0) due to more structural entanglement and intermolecular hydrogen bonds as compared to the other type of commercial starch and control. In particle size distribution curve of this sample a broad and distinguished peak with higher percentage of population ranging from 10 to 100 µm was observed which might be due to the higher water absorption and more swollen/degraded starch granules. The area-based average diameter (d3,2) of the particles confirmed more similarity between this sample and control. تفاصيل المقالة -
حرية الوصول المقاله
17 - سرمایه گذاری در صنعت نفت و گاز با استفاده از تخمین مصرف نفت خام و گازطبیعی در ایران با رویکرد مدل VECM
وحید رجبیان رضا طالبلو حمیدرضا اربابهدف اصلی این پژوهش برآورد تقاضای نفت‌خام و گازطبیعی در کشور طی دوره 1367 الی 1394 و همچنین برآورد تابع تقاضای نفت‌خام و گازطبیعی و میزان سرمایه گذاری لازم در ایران طی برنامه ششم با هدف بررسی اثر متغیرهای مهم تأثیرگذار بر مصرف آنها در داخل کشور است. در عین حال، از مدل خو أکثرهدف اصلی این پژوهش برآورد تقاضای نفت‌خام و گازطبیعی در کشور طی دوره 1367 الی 1394 و همچنین برآورد تابع تقاضای نفت‌خام و گازطبیعی و میزان سرمایه گذاری لازم در ایران طی برنامه ششم با هدف بررسی اثر متغیرهای مهم تأثیرگذار بر مصرف آنها در داخل کشور است. در عین حال، از مدل خودرگرسیون-برداری (VAR) و مدل تصحیح‌خطای‌برداری (VECM) برای بررسی رابطه و میزان تأثیر متغیرها و نیز برای استخراج رابطه کوتاه‌مدت و بلندمدت بین متغیرها استفاده شده و نهایتا" پس از استخراج مدل از آن برای پیش بینی تقاضای نفت‌خام و گازطبیعی در کشور در افق 1400 استفاده گردیده است. نتایج حاکی از: 1) با توجه به روند رو به رشد مصرف انرژی طبق پیش بینی صورت گرفته در این پژوهش و محدودیت تولید در کشور به دلیل سرمایه گذاریهای بالایی که بخشهای نفت و گاز نیازمند می باشند، در صورت عدم جذب سرمایه گذاری داخلی و خارجی، در آینده نه چندان دور تاثیر منفی آن در درآمدهای حاصل از صادرات نفت و گاز دور از انتظار نخواهد بود. 2) کشش درآمدی اندک و حساسیت نه چندان مصرف نفت‌خام نسبت به تغییرات در درآمد (در اینجا درآمد سرانه) دارد. 3) نشان از عدم وجود رابطه علیت بلندمدت از جانب متغیرهای مستقل درونزا و متغیرهای مستقل برونزایی همچون قیمت نفت‌خام و قیمت گازطبیعی، به سمت مصرف گازطبیعی و درآمد سرانه دارد. 4) در کوتاه‌مدت هیچ رابطه علی از جانب مصرف گازطبیعی، قیمت گازطبیعی، قیمت نفت‌خام و درآمد‌سرانه به سمت مصرف نفت‌خام وجود ندارد. تفاصيل المقالة -
حرية الوصول المقاله
18 - Vibration Analysis of a Current-Carrying Wire in a Magnetic Field Apllying Variational Iteration Method
M. HosseiniIn the present investigation, Variational Iteration Method (VIM) is applied to solve the dynamic oscillation of a current-carrying wire in a magnetic field which is generated by a fixed current-carrying conductor parallel to the wire. Two linear springs are considered t أکثرIn the present investigation, Variational Iteration Method (VIM) is applied to solve the dynamic oscillation of a current-carrying wire in a magnetic field which is generated by a fixed current-carrying conductor parallel to the wire. Two linear springs are considered to restrict the wire to a rigid wall. In a special case, the periodic solution of the problem is obtained by VIM and compared with numerical solutions for different parameters. Results indicate high accuracy of this method which can be easily extended to solve other non-linear vibration equations, therefore can be applicable in other engineering problems. تفاصيل المقالة -
حرية الوصول المقاله
19 - The Effect of Heat Treatment on the Microstructural and Superelastic Behavior of NiTi Alloy with 58.5 wt. % Ni
M. ParyabThe effect of aging process on hardness as well as the superelastic behavior of NiTi shape memory alloy with 58.5 wt. % Ni has been investigated in this paper. The aging process has been performed at different temperatures ranging from 400 oC to 800oC and for various ex أکثرThe effect of aging process on hardness as well as the superelastic behavior of NiTi shape memory alloy with 58.5 wt. % Ni has been investigated in this paper. The aging process has been performed at different temperatures ranging from 400 oC to 800oC and for various exposure times from 30 min to 8 hours. The results showed an increase in hardness in the temperature range from 400 oC to 500 oC and then a decrease occurs. At constant temperature with prolonged aging time a gradual increase of hardness occurs. SEM observations showed that there is some precipitation in specimens aged from 600 oC to 800 oC. The decrease of hardness can be due to an increase in precipitate size. The superelastisity investigation at 25 and 60 oC showed that the maximum superelastisit results are related to specimens aged at 400 oC. The superelastisity properties of NiTi were discussed in terms of hardness and microstructure. تفاصيل المقالة -
حرية الوصول المقاله
20 - Modal and Aeroelastic Analysis of A High-Aspect-Ratio Wing with Large Deflection Capability
R. Koohi H. Shahverdi H. HaddadpourThis paper describes a modified structural dynamics model for aeroelastic analysis of high-aspect-ratio wings undergoing large deformation behavior. To gain this aim, a moderate deflection beam model is modified with some important large deflection terms and then couple أکثرThis paper describes a modified structural dynamics model for aeroelastic analysis of high-aspect-ratio wings undergoing large deformation behavior. To gain this aim, a moderate deflection beam model is modified with some important large deflection terms and then coupled with a state space unsteady aerodynamics model. Finite element method is used to discretize the equations of motion. A dynamic perturbation equation about a nonlinear static equilibrium is applied to determine the flutter boundary. The obtained results show good agreement in comparison with the other existing data such as high-altitude long-endurance (HALE) wing and Goland wing. It is found that the present aeroelastic tool have a good agreement in comparison with valid researches and also considering the effect of the geometric structural nonlinearity and higher order nonlinear terms on the flutter boundary determination is very significant. تفاصيل المقالة -
حرية الوصول المقاله
21 - Development of Boundary Layer of Highly Elastic Flow of the Upper Convected Maxwell Fluid over a Stretching Sheet
Meysam Mohamadali Nariman AshrafiHigh Weissenberg boundary layer flow of viscoelastic fluids on a stretching surface has been studied. The flow is considered to be steady and two dimensional. Flows of viscoelastic liquids at high Weissenberg number exhibit stress boundary layers near walls. These bound أکثرHigh Weissenberg boundary layer flow of viscoelastic fluids on a stretching surface has been studied. The flow is considered to be steady and two dimensional. Flows of viscoelastic liquids at high Weissenberg number exhibit stress boundary layers near walls. These boundary layers are caused by the memory of the fluid. Upon proper scaling and by means of an exact similarity transformation, the non-linear momentum and constitutive equations of each layer transform into the respective system of highly nonlinear and coupled ordinary differential equations. Effects of variation in pressure gradient and Weissenberg number on velocity profile and stress components are investigated. It is observed that the value of stress components decrease by Weissenberg number. Moreover, the results show that increasing the pressure gradient results in thicker velocity boundary layer. It is observed that unlike the Newtonian flows, in order to maintain a potential flow, normal stresses must inevitably develop in far fields. تفاصيل المقالة -
حرية الوصول المقاله
22 - Buckling Analysis of Orthotropic Annular Graphene Sheet with Various Boundary Conditions in an Elastic Medium
Hamed Vahabi Mohammad Esmaeil Golmakani Ismaeil MobasherIn this study, axisymmetric buckling of annular orthotropic graphene sheet embedded in a Winkler–Pasternak elastic medium is scrutinized for different boundary conditions based on non-local elasticity theory. With the aid of principle of virtual work, the non-loca أکثرIn this study, axisymmetric buckling of annular orthotropic graphene sheet embedded in a Winkler–Pasternak elastic medium is scrutinized for different boundary conditions based on non-local elasticity theory. With the aid of principle of virtual work, the non-local governing equations are derived based on First-order Shear Deformation Theory (FSDT). Differential Quadrature Method (DQM) is also used to solve equilibrium equations. Edges of Nano-plate might be restrained by different combinations of free, simply supported or clamped boundary conditions. To confirm results, comparison of studies is made between results obtained and available solutions in the literature. Finally, a detailed parametric study is conducted to investigate the impact of small scale effects, surrounding elastic medium, boundary conditions and geometrical parameters on critical buckling load. The main goal of this work is to study the effect of various non-local parameters on the buckling load of annular Nano-plate for different boundary conditions, Winkler and shear foundation parameters, annularity and thickness-to-radius ratios. It is seen that for Nano-plates without an elastic foundation, the impact of thickness on buckling load does not depend on values of non-local parameter and annularity. Results also show that impact of elastic basis on the buckling load is independent of small scale effects. تفاصيل المقالة -
حرية الوصول المقاله
23 - Investigation of the AFM Indenter’s Geometry Effect On Micro/Nano Biological Cells’ Indentation
Yousef Habibi Sooha Moharam Habibnejad Zahra RastegarThe elasticity modules of the micro/Nanoparticles, especially biological particles are measured using different tools such as atomic force microscopy. The tip of the atomic force microscopy as an indenter has different shapes such as spherical, conical and pyramidal. In أکثرThe elasticity modules of the micro/Nanoparticles, especially biological particles are measured using different tools such as atomic force microscopy. The tip of the atomic force microscopy as an indenter has different shapes such as spherical, conical and pyramidal. In the contact of these tips and biological cells, avoiding the cell damage is a necessity. The goal of this paper is investigation and comparison of different tips’ geometries. Different tip’s geometries and their related theories were collected and proposed. To generalize theories’ application for any kind of particle (even non-biological particles) some of simplifying assumptions used in these theories, such as tip rigidity, were removed. Simulation of the force- indentation depth was done for gold nanoparticle and observed that if simplifying assumptions were not removed there would be big errors in calculating the elasticity module of some particles. Then, simulations were done for two yeast and mouse embryo cells. For both cells, in general, the geometry of the curve group, the geometry of the pyramidal group and finally the geometry of the conical group were positioned from the highest to the lowest places. For hyperbolic, conical and pyramidal tips, the important parameter was semi vertical angel. To observe its effect, different magnitudes of this parameter were simulated. According to observed results in three investigated geometries and for both cells, bigger semi vertical angel created higher curves and this means in bigger angels the possibility of cell damage is higher. تفاصيل المقالة -
حرية الوصول المقاله
24 - Evaluating the Effect of the Second Invariant of Deformation Tensor in The Axial and Azimuthal Shear Deformations
Amir Ghafouri Sayyad Ali Imam Shahram Etemadi HaghighiThe purpose of the present paper is to investigate the effect of the second invariant of the deformation tensor on the axial and azimuthal shear deformation of an incompressible hyperelastic solid with various strain energy functions. To this end, the axial shear deform أکثرThe purpose of the present paper is to investigate the effect of the second invariant of the deformation tensor on the axial and azimuthal shear deformation of an incompressible hyperelastic solid with various strain energy functions. To this end, the axial shear deformation of an incompressible cylinder with the modified Gent-Thomas, Gent-Thomas, Gent-Gent, and Carroll strain energies subjected to an axial shear traction is considered, where the displacement field is determined analytically for the first three models and numerically for the fourth model. The phenomenon of strain hardening at large elastic deformations, predicted either by the limiting chain extensibility condition for the modified Gent-Thomas and Gent-Gent models or phenomenologically by the Carroll model, is observed and it is shown that the second invariant of deformation increases the strain hardening experienced by such materials. Next, the azimuthal shear deformation of an incompressible annular wedge with the modified Gent-Thomas, Gent-Thomas, Gent-Gent, and Carroll models is considered, where the annular wedge is subjected to a controllable azimuthal shear deformation and the angular displacement is determined analytically for all the above models. Again, the second invariant of the deformation tensor is shown to have a significant effect on the azimuthal shear deformation as reflected in the increase of the strain hardening of the material in such deformation. In addition, the annular wedge with the modified Gent-Thomas and Carroll models is shown to have a higher resistance in azimuthal shear deformation than the other models mentioned above. تفاصيل المقالة -
حرية الوصول المقاله
25 - Behavior of Lightweight Smart Sandwich Panels Subjected to Tensile and Bending Loads- An Experimental Study
sameera Khalili s. Mohammad Khalili Reza Eslami Farsani Puneet MahajanIn this research work, sandwich composite panels made by fiber metal laminate (FML) as the facesheets and polymer foams as the core material are investigated in tensile and bending loads. To change or enhance the behaviour of sandwich panels in tensile and bending loads أکثرIn this research work, sandwich composite panels made by fiber metal laminate (FML) as the facesheets and polymer foams as the core material are investigated in tensile and bending loads. To change or enhance the behaviour of sandwich panels in tensile and bending loads, shape memory alloy wires with pseudoelastic behaviour are also embedded in between FML layers in facesheets. The shape memory wires are also pre-strained in the FML facesheets of sandwich panels. To study the tensile and flexural properties of sandwich panels with smart FML facesheets three types of sandwich panels are considered and made including panels without shape memory alloy wire, panels with shape memory wires with 0% tensile pre-strain, and panels with shape memory wires with 5% tensile pre-strain for the same cross section. By placing SMA wires in the FML, the strength and stiffness of the smart sandwich specimens are increased significantly in tensile and bending loads. However, the effect of pre-straining the SMA wires is more predominant on stiffness of the specimens. The tensile and flexural toughness or energy absorption is much higher in case of the specimen with 5% pre-strained SMA wires. At the expenses of adding the SMA wires in the sandwich structures, the densities of various specimens are changed by nearly 1% to 5% for various specimens, but a significant increase in mechanical properties such as the strength and particularly the stiffness and toughness were achieved by the present lightweight smart sandwich structures. تفاصيل المقالة -
حرية الوصول المقاله
26 - Increasing the Fundamental Frequency of the Cantilever Rotating Beam by Placing the Intermediate Elastic Support with Minimum Stiffness at the Optimum Point Based on the Courant’s Maximum–Minimum Theorem using Finite-Element Analysis Software
Mehdi Asgarikia Farshad Kakavand Hasan Seidi: In this paper, the effect of the optimal position and minimum stiffness of the elastic middle support on increasing the fundamental frequency of a rotating cantilever beam is investigated based on the Courant’s maximum–minimum theorem using ABAQUS finite e أکثر: In this paper, the effect of the optimal position and minimum stiffness of the elastic middle support on increasing the fundamental frequency of a rotating cantilever beam is investigated based on the Courant’s maximum–minimum theorem using ABAQUS finite element software. First, the software analysis results are compared with the numerical analysis results for a non-rotating cantilever beam to confirm the accuracy of the software model. Next, by placing the middle elastic support at the optimal point selected based on the Courant theorem, the minimum stiffness of the elastic intermediate support for the maximum fundamental frequency of the rotating console beam was obtained. The results of this study prove that the Courant’s maximum–minimum theorem is completely valid for rotating cantilever beams and can be used to improve the vibrational behavior of rotating engineering components. Finally, the minimum diameter of damping wire for the turbomachine blade is calculated as a practical application of the minimum stiffness of the intermediate elastic support for the rotating beam. تفاصيل المقالة -
حرية الوصول المقاله
27 - Active Control of Sandwich Microbeams Vibration with FGM and Viscoelastic/ER Core
Amir Hossein Yousefi farhad kiani Esmaeil AbediThis study is devoted to analyse of free and forced vibrations and semi-active control vibrations of sandwich microbeam with Functionally Graded Materials (FGM) and viscoelastic/electrorheological (ER) core. The intended model is for top and bottom layers of functionall أکثرThis study is devoted to analyse of free and forced vibrations and semi-active control vibrations of sandwich microbeam with Functionally Graded Materials (FGM) and viscoelastic/electrorheological (ER) core. The intended model is for top and bottom layers of functionally graded materials with power law and a core model for Viscoelastic materials with complex shear modulus. Hamilton principle is used to determine the governing Equations of motion on the sandwich microbeam based on the modified couple stress theory. Mesh less method of Radial Basis Functions (RBF) is used to calculate natural frequency and the loss factor. All the effects of length scale parameter, shear modulus and changes due to variation of the electric field on the natural frequency and loss factor have been drawn. Combination of RBF method and forward difference led to evaluation of forced vibration and deflection of microbeam for length scale parameters and different electric fields under the dynamic load have been calculated and drawn. The feedback effects are analyzed for vibration amplitudes of sandwich microbeam by using Linear Quadratic Gaussian (LQG) and optimal control method. At the end, the results are compared with papers for different viscoelastic models such as Kelvin model, Bingham plastic model and complex modulus. تفاصيل المقالة -
حرية الوصول المقاله
28 - Natural Frequency and Dynamic Analyses of Functionally Graded Saturated Porous Beam Resting on Viscoelastic Foundation Based on Higher Order Beam Theory
M Babaei K Asemi P SafarpourIn this paper, natural frequencies and dynamic response of thick beams made of saturated porous materials resting on viscoelastic foundation are investigated for the first time. The beam is modeled using higher-order beam theory. Kelvin-voight model is used to model the أکثرIn this paper, natural frequencies and dynamic response of thick beams made of saturated porous materials resting on viscoelastic foundation are investigated for the first time. The beam is modeled using higher-order beam theory. Kelvin-voight model is used to model the viscoelastic foundation. Distribution of porosity along the thickness is considered in two different patterns, which are symmetric nonlinear and nonlinear asymmetric distributions. The relationship between stress and strain is based on the Biot constitutive law. Lagrange equations are used to express the motion equations. Finite element and Newark methods are used to solve the governing equations. The effect of different boundary conditions and various parameters such as porosity and Skempton coefficients, slenderness ratio as well as stiffness and damping coefficients of viscoelastic foundation on natural frequency and transient response of beam have been studied. Results show that in a drained condition, beam has smallest fundamental frequency and by increasing the Skempton coefficient, the fundamental frequency of the beam increases. تفاصيل المقالة -
حرية الوصول المقاله
29 - On Plane Waves for Mode-I Crack Problem in Generalized Thermoelasticity
kh LotfyA general model of the equations of generalized thermoelasticity for an infinite space weakened by a finite linear opening Mode-I crack is solving. The material is homogeneous and has isotropic properties of elastic half space. The crack is subjected to prescribed tempe أکثرA general model of the equations of generalized thermoelasticity for an infinite space weakened by a finite linear opening Mode-I crack is solving. The material is homogeneous and has isotropic properties of elastic half space. The crack is subjected to prescribed temperature and stress distribution. The formulation is applied to generalized thermoelasticity theories, the Lord-Şhulman and Green-Lindsay theories, as well as the classical dynamical coupled theory. The normal mode analysis is used to obtain the exact expressions for the displacement components, force stresses, temperature, couple stresses and micro-stress distribution. The variations of the considered variables through the horizontal distance are illustrated graphically. Comparisons are made with the results between the three theories. تفاصيل المقالة -
حرية الوصول المقاله
30 - A New Three-Dimensional Sector Element for Circular Curved Structures Analysis
H. E Khiouani L Belounar M Nabil HouhouIn this research paper, the formulation of a new three-dimensional sector element based on the strain approach is presented for plate bending problems and linear static analysis of circular structures. The proposed element has the three essential external degrees of fre أکثرIn this research paper, the formulation of a new three-dimensional sector element based on the strain approach is presented for plate bending problems and linear static analysis of circular structures. The proposed element has the three essential external degrees of freedom (Ur, Vθ and W) at each of the eight corner nodes. The displacements field of the present element is based on assumed functions for the different strains satisfying the compatibility equations. The effectiveness of the present element is applied through several tests related to plate bending problems and linear static analysis of circular structures. The results of the developed element have been compared with analytical and other numerical solutions available in the literature. The obtained results show the excellent performances and precision of the present element. It is found that the new three-dimensional sector element is more accurate and efficient than the three-dimensional classical element based on displacement approach. تفاصيل المقالة -
حرية الوصول المقاله
31 - An Axisymmetric Torsion Problem of an Elastic Layer on a Rigid Circular Base
B Kebli S Berkane F GuerracheA solution is presented to a doubly mixed boundary value problem of the torsion of an elastic layer, partially resting on a rigid circular base by a circular rigid punch attached to its surface. This problem is reduced to a system of dual integral equations using the Bo أکثرA solution is presented to a doubly mixed boundary value problem of the torsion of an elastic layer, partially resting on a rigid circular base by a circular rigid punch attached to its surface. This problem is reduced to a system of dual integral equations using the Boussinesq stress functions and the Hankel integral transforms. With the help of the Gegenbauer expansion formula of the Bessel function we get an infinite algebraic system of simultaneous equations for calculating the unknown function of the problem. Both the two contact stresses under the punch and on the lower face of the layer are expressed as appropriate Chebyshev series. The effects of the radius of the disc with the rigid base and the layer thickness on the displacements, contact stresses as well as the shear stress and the stress singularity factor are discussed. A numerical application is also considered with some concluding results. تفاصيل المقالة -
حرية الوصول المقاله
32 - Fundamental Solution in the Theory of Thermoelastic Diffusion Materials with Double Porosity
T KansalThe main purpose of present article is to find the fundamental solution of partial differential equations in the generalized theory of thermoelastic diffusion materials with double porosity in case of steady oscillations in terms of elementary functions.The main purpose of present article is to find the fundamental solution of partial differential equations in the generalized theory of thermoelastic diffusion materials with double porosity in case of steady oscillations in terms of elementary functions. تفاصيل المقالة -
حرية الوصول المقاله
33 - Vibration Analysis of Size-Dependent Piezoelectric Nanobeam Under Magneto-Electrical Field
M Ghadiri M Karimi Asl M NorooziThe damping vibration characteristics of magneto-electro-viscoelastic (MEV) nanobeam resting on viscoelastic foundation based on nonlocal strain gradient elasticity theory (NSGT) is studied in this article. For this purpose, by considering the effects of Winkler-Pastern أکثرThe damping vibration characteristics of magneto-electro-viscoelastic (MEV) nanobeam resting on viscoelastic foundation based on nonlocal strain gradient elasticity theory (NSGT) is studied in this article. For this purpose, by considering the effects of Winkler-Pasternak, the viscoelastic medium consists of linear and viscous layers. with respect to the displacement field in accordance with the refined shear deformable beam theory (RSDT) and the Kelvin-Voigt viscoelastic damping model, the governing equations of motion are obtained using Hamilton’s principle based on nonlocal strain gradient theory (NSGT). Using Fourier Series Expansion, The Galerkin’s method adopted to solving differential equations of nanobeam with both of simply supported and clamped boundary conditions. Numerical results are obtained to show the influences of nonlocal parameter, the length scale parameter, slenderness ratio and magneto-electro-mechanical loadings on the vibration behavior of nanobeam for both types of boundary conditions. It is found that by increasing the magnetic potential, the dimensionless frequency can be increased for any value of the damping coefficient and vice versa. Moreover, negative/positive magnetic potential decreases/increases the vibration frequencies of thinner nanobeam. Also, the vibrating frequency decreases and increases with increasing nonlocal parameter and length scale parameter respectively. تفاصيل المقالة -
حرية الوصول المقاله
34 - Influence of Viscoelastic Foundation on Dynamic Behaviour of the Double Walled Cylindrical Inhomogeneous Micro Shell Using MCST and with the Aid of GDQM
A Mohammadi H Lashini M Habibi H SafarpourIn this article, dynamic modeling of double walled cylindrical functionally graded (FG) microshell is studied. Size effect of double walled cylindrical FG microshell are investigated using modified couple stress theory (MCST). Each layer of microshell is embedded in a v أکثرIn this article, dynamic modeling of double walled cylindrical functionally graded (FG) microshell is studied. Size effect of double walled cylindrical FG microshell are investigated using modified couple stress theory (MCST). Each layer of microshell is embedded in a viscoelasticmedium. For the first time, in the present study, has been considered, FG length scale parameter in double walled cylindrical FG microshells, which this parameter changes along the thickness direction. Taking into consideration the first-order shear deformation theory (FSDT), double walled cylindrical FG microshell is modeled and its equations of motions are derived using Hamilton's principle. The novelty of this study is considering the effects of double layers and MCST, in addition to considering the various boundary conditions of double walled cylindrical FG microshell. Generalized differential quadrature method (GDQM) is used to discretize the model and to approximate the equation of motions and boundary conditions. Also, for confirmation, the result of current model is validated with the results obtained from molecular dynamics (MD) simulation. Considering length scale parameter (l=R/3) on MCST show, the results have better agreement with MD simulation. The results show that, length, thickness, FG power index, Winkler and Pasternak coefficients and shear correction factor have important role on the natural frequency of double walled cylindrical FG microshell. تفاصيل المقالة -
حرية الوصول المقاله
35 - Hygrothermal Creep and Stress Redistribution Analysis of Temperature and Moisture Dependent Magneto-Electro-Elastic Hollow Sphere
M SaadatfarIn this article, the time-dependent stress redistribution analysis of magneto-electro-elastic (MEE) thick-walled sphere subjected to mechanical, electrical, magnetic and uniform temperature gradient as well as moisture concentration gradient is presented. Combining cons أکثرIn this article, the time-dependent stress redistribution analysis of magneto-electro-elastic (MEE) thick-walled sphere subjected to mechanical, electrical, magnetic and uniform temperature gradient as well as moisture concentration gradient is presented. Combining constitutive equations of MEE with stress-strain relations as well as strain-displacement relations results in obtaining a differential equation in which there are the creep strains. At the first step, discounting creep strains in the mentioned equation, an analytical solution for the hygro-thermo-magneto-electro-elastic behavior is achieved at the initial state. After that, the creep stress rates can be achieved by keeping only the creep strains in the differential equation for the steady-state condition. The analysis is done by applying the Prandtl-Reuss equations as well as Norton’s law in creep behavior modeling. Finally, the history of stresses, displacement as well as magnetic and potential field, at any time, is achieved using an iterative method. Results show that the increase in tensile hoop stress resulted from creep progress must be considered in design progress. Also, the effect of hygrothermal loading is more extensive after creep evolution. تفاصيل المقالة -
حرية الوصول المقاله
36 - Effects of Viscosity on a Thick Circular Plate in Thermoelastic Diffusion Medium
R Kumar Sh DeviThe problem treated here is to determinethe viscosity effect on stresses, temperature change and chemical potential in a circular plate. The mathematical formulation is applied to two theories of thermoelastic diffusion developed by Sherief et al. [27] with one relaxati أکثرThe problem treated here is to determinethe viscosity effect on stresses, temperature change and chemical potential in a circular plate. The mathematical formulation is applied to two theories of thermoelastic diffusion developed by Sherief et al. [27] with one relaxation time and Kumar and Kansal [9]with two relaxation times. Laplace and Hankel transform techniques are used to obtain the expression for the displacement components, stresses, temperature change and chemical potential. The resulting quantities are computed numerically and depicted graphically by using numerical inversion technique for a particular model. Effect of viscosity is shown in the normal stress, tangential stress, temperature change and chemical potential. Some particular cases of interest are also deduced. Viscoelastic materials play an important role in many branches of engineering, technology and, in recent years, biomechanics. Viscoelastic materials, such as amorphous polymers, semicrystalline polymers, and biopolymers, can be modelled in order to determine their stress or strain interactions as well as their temporal dependencies. تفاصيل المقالة -
حرية الوصول المقاله
37 - Higher-Order Stability Analysis of Imperfect Laminated Piezo-Composite Plates on Elastic Foundations Under Electro-Thermo-Mechanical Loads
B Mirzavand M BohloolyThis article provides a fully analytical approach for nonlinear equilibrium path of rectangular sandwich plates. The core of structure is made of symmetric cross-ply laminated composite and the outer surfaces are piezoelectric actuators which perfectly bonded to inner c أکثرThis article provides a fully analytical approach for nonlinear equilibrium path of rectangular sandwich plates. The core of structure is made of symmetric cross-ply laminated composite and the outer surfaces are piezoelectric actuators which perfectly bonded to inner core. The structure is subjected to electro-thermo-mechanical loads simultaneously. One side of plate is rested on Pasternak type elastic foundation. The equilibrium equations of plate are derived based on the higher-order shear deformation theory of Reddy taking into account initial geometrical imperfection, nonlinear strain-displacement relations of von-Karman, temperature dependent properties, and different types of boundary conditions. Some numerical examples are presented to verify the accuracy of the proposed formulation. The effects of various parameters such as voltage on actuators, elastic foundation, imperfection, and pre-load condition on the buckling and postbuckling behaviors are studied. As an important finding of current research, there may be exists bifurcation point for imperfect plates by applying voltage on actuators. تفاصيل المقالة -
حرية الوصول المقاله
38 - Vibration, Buckling and Deflection Analysis of Cracked Thin Magneto Electro Elastic Plate Under Thermal Environment
Shashank Soni N.K Jain P.V. JoshiThe Magneto-Electro-Elastic (MEE) material exhibits pyroelectric and pyromagnetic effects under thermal environment. The effects of such pyroelectric and pyromagnetic behavior on vibration, buckling and deflection analysis of partially cracked thin MEE plate is presente أکثرThe Magneto-Electro-Elastic (MEE) material exhibits pyroelectric and pyromagnetic effects under thermal environment. The effects of such pyroelectric and pyromagnetic behavior on vibration, buckling and deflection analysis of partially cracked thin MEE plate is presented and discussed in this paper. The aim of the study is to develop an analytical model for the vibration and geometrically linear thermal buckling analysis of cracked MEE plate based on the classical plate theory (CPT). The line spring model (LSM) is modified for the crack terms to accommodate the effect of electric and magnetic field rigidities, whereas the effect of thermal environment is accommodated in the form of thermal moment and in-plane forces. A classical relation for thermal buckling phenomenon of cracked MEE plate is also proposed. The governing equation for cracked MEE plate has also been solved to get central deflection which shows an important phenomenon of shift in primary resonance due to crack and temperature rise. The results evaluated for natural frequencies as affected by crack length, plate aspect ratio and critical buckling temperature are presented for first four modes of vibration. The obtained results reveal that the fundamental frequency of the cracked plate decreases with increase in temperature and crack length. Furthermore the variation of the critical buckling temperature with plate aspect ratio and crack length is also established for different modes of vibration. تفاصيل المقالة -
حرية الوصول المقاله
39 - Dynamics of Love-Type Waves in Orthotropic Layer Under the Influence of Heterogeneity and Corrugation
S.A Sahu S Goyal S MondalThe present problem deals with the propagation of Love-type surface waves in a bedded structure comprises of an inhomogeneous orthotropic layer and an elastic half-space. The upper boundary and the interface between two media are considered to be corrugated. An analytic أکثرThe present problem deals with the propagation of Love-type surface waves in a bedded structure comprises of an inhomogeneous orthotropic layer and an elastic half-space. The upper boundary and the interface between two media are considered to be corrugated. An analytical method (separation of variables) is adapted to solve the second order PDEs, which governs the equations of motion. Equations for particle motion in the layer and half-space have been formulated and solved separately. Finally, the frequency relation has been established under suitable boundary conditions at the interface of the orthotropic layer and the elastic half-space. Obtained relation is found to be in good agreement with the classical case of Love wave propagation. Remarkable effects of heterogeneity and corrugation parameters on the phase velocity of the considered wave have been represented by the means of graphs. Moreover, the group velocity curves are also plotted to exhibit the profound effect of heterogeneity considered in the layer. Results may be useful in theoretical study of wave propagation through composite layered structure with irregular boundaries. تفاصيل المقالة -
حرية الوصول المقاله
40 - Analysis of Nonlinear Vibrations of Slightly Curved Tripled-Walled Carbon Nanotubes Resting on Elastic Foundations in a Magneto-Thermal Environment
M.G Sobamowo J.O Akanmu O.A Adeleye A.A YinusaIn this work, nonlocal elasticity theory is applied to analyze nonlinear free vibrations of slightly curved multi-walled carbon nanotubes resting on nonlinear Winkler and Pasternak foundations in a thermal and magnetic environment. With the aid of Galerkin decomposition أکثرIn this work, nonlocal elasticity theory is applied to analyze nonlinear free vibrations of slightly curved multi-walled carbon nanotubes resting on nonlinear Winkler and Pasternak foundations in a thermal and magnetic environment. With the aid of Galerkin decomposition method, the systems of nonlinear partial differential equations are transformed into systems of nonlinear ordinary differential equations which are solved using homotopy perturbation method. The influences of elastic foundations, magnetic field, temperature rise, interlayer forces, small scale parameter and boundary conditions on the frequency ratio are investigated. It is observed form the results that the frequency ratio for all boundary conditions decreases as the number of walls increases. Also, it is established that the frequency ratio is highest for clamped-simple supported and lowest for clamped-clamped supported. Further investigations on the controlling parameters of the phenomena reveal that the frequency ratio decreases with increase in the value of spring constant (k1) temperature and magnetic field strength. It is hoped that this work will enhance the applications of carbon nanotubes in structural, electrical, mechanical and biological applications especially in a thermal and magnetic environment. تفاصيل المقالة -
حرية الوصول المقاله
41 - An Axisymmetric Contact Problem of a Thermoelastic Layer on a Rigid Circular Base
F Guerrache B KebliWe study the thermoelastic deformation of an elastic layer. The upper surface of the medium is subjected to a uniform thermal field along a circular area while the layer is resting on a rigid smooth circular base. The doubly mixed boundary value problem is reduced to a أکثرWe study the thermoelastic deformation of an elastic layer. The upper surface of the medium is subjected to a uniform thermal field along a circular area while the layer is resting on a rigid smooth circular base. The doubly mixed boundary value problem is reduced to a pair of systems of dual integral equations. The both system of the heat conduction and the mechanical problems are calculated by solving a dual integral equation systems which are reduced to an infinite algebraic one using a Gegenbauer’s formulas. The stresses and displacements are then obtained as Bessel function series. To get the unknown coefficients, the infinite systems are solved by the truncation method. A closed form solution is given for the displacements, stresses and the stress singularity factors. The effects of the radius of the punch with the rigid base and the layer thickness on the stress field are discussed. A numerical application is also considered with some concluding results. تفاصيل المقالة -
حرية الوصول المقاله
42 - Bending Behavior of Sandwich Plates with Aggregated CNT-Reinforced Face Sheets
M Mirzaalian F Aghadavoudi R Moradi-DastjerdiThe main aim of this paper is to investigate bending behavior in sandwich plates with functionally graded carbon nanotube reinforced composite (FG-CNTRC) face sheets with considering the effects of carbon nanotube (CNT) aggregation. The sandwich plates are assumed resti أکثرThe main aim of this paper is to investigate bending behavior in sandwich plates with functionally graded carbon nanotube reinforced composite (FG-CNTRC) face sheets with considering the effects of carbon nanotube (CNT) aggregation. The sandwich plates are assumed resting on Winkler-Pasternak elastic foundation and a mesh-free method based on first order shear deformation theory (FSDT) is developed to analyze the deflection of sandwich plates. In the face sheets, volume fraction of CNTs and their clusters are considered to be changed along the thickness. To estimate the material properties of the nanocomposite, Eshelby-Mori-Tanaka approach is applied. In the mesh-free analysis, moving least squares (MLS) shape functions are employed to approximate the displacement field and transformation method is used for imposition of essential boundary conditions. The effects of CNT volume fraction, distribution and degree of aggregation, and also boundary conditions and geometric dimensions are investigated on the bending behavior of the sandwich plates. It is observed that in the same value of cluster volume, FG distribution of clusters leads to less deflection in these structures. تفاصيل المقالة -
حرية الوصول المقاله
43 - Size-Dependent Forced Vibration Analysis of Three Nonlocal Strain Gradient Beam Models with Surface Effects Subjected to Moving Harmonic Loads
K Rajabi Sh Hosseini Hashemi A.R NezamabadiThe forced vibration behaviors are examined for nonlocal strain gradient nanobeams with surface effects subjected to a moving harmonic load travelling with a constant velocity in terms of three beam models namely, the Euler-Bernoulli, Timoshenko and modified Timoshenko أکثرThe forced vibration behaviors are examined for nonlocal strain gradient nanobeams with surface effects subjected to a moving harmonic load travelling with a constant velocity in terms of three beam models namely, the Euler-Bernoulli, Timoshenko and modified Timoshenko beam models. The modification for nonlocal strain gradient Timoshenko nanobeams is exerted to the constitutive equations by exclusion of the nonlocality in the shear constitutive relation. Some analytical closed-form solutions for three nonlocal strain gradient beam models with simply supported boundary conditions are derived by using the Galerkin discretization method in conjunction with the Laplace transform method. The effects of the three beam models, the nonlocal and material length scale parameters, the velocity and excitation frequency of the moving harmonic load on the dynamic behaviors of nanobeams are discussed in some detail. Specifically, the critical velocities are examined in some detail. Numerical results have shown that the aforementioned parameters are very important factors for determining the dynamic behavior of the nanobeams accurately. تفاصيل المقالة -
حرية الوصول المقاله
44 - A Novel Method for Numerical Analysis of 3D Nonlinear Thermo-Mechanical Bending of Annular and Circular Plates with Asymmetric Boundary Conditions Using SAPM
A. R Golkarian M Jabbarzadeh Sh DastjerdiThis study is the first report of numerical solution of nonlinear bending analysis for annular and circular plates based on 3D elasticity theory with asymmetric boundary conditions using semi-analytical polynomial method (SAPM). Orthotropic annular and circular plates a أکثرThis study is the first report of numerical solution of nonlinear bending analysis for annular and circular plates based on 3D elasticity theory with asymmetric boundary conditions using semi-analytical polynomial method (SAPM). Orthotropic annular and circular plates are subjected to transverse loading and 3D bending analysis in the presence of symmetric and asymmetric boundary conditions is studied. For asymmetry cases, the plate boundaries are divided to two or three parts and various boundary conditions such as clamped, simply-supported and free edges are defined for each part. The asymmetry in one and two directions is studied. The influence of elastic foundations, mechanical and thermo-mechanical loadings are examined. Regarding this fact that no study has been done in the case of asymmetric boundary conditions, the obtained results are compared with FEM results by ABAQUS. The results show good agreement with the literatures and FEM results, which it shows that the presented method can use to analyze the 3D bending of plates under asymmetric conditions. Also, it is observed that 3D elasticity estimates some higher deflections than other theories. But, the obtained results by 3D elasticity theory and those obtained by FEM analysis in the case of asymmetric conditions are so close. تفاصيل المقالة -
حرية الوصول المقاله
45 - On Static Bending, Elastic Buckling and Free Vibration Analysis of Symmetric Functionally Graded Sandwich Beams
A.S Sayyad P.V AvhadThis article presents Navier type closed-form solutions for static bending, elastic buckling and free vibration analysis of symmetric functionally graded (FG) sandwich beams using a hyperbolic shear deformation theory. The beam has FG skins and isotropic core. Material أکثرThis article presents Navier type closed-form solutions for static bending, elastic buckling and free vibration analysis of symmetric functionally graded (FG) sandwich beams using a hyperbolic shear deformation theory. The beam has FG skins and isotropic core. Material properties of FG skins are varied through the thickness according to the power law distribution. The present theory accounts for a hyperbolic distribution of axial displacement whereas transverse displacement is constant through the thickness i.e effects of thickness stretching are neglected. The present theory gives hyperbolic cosine distribution of transverse shear stress through the thickness of the beam and satisfies zero traction boundary conditions on the top and bottom surfaces of the beam. The equations of the motion are obtained by using the Hamilton’s principle. Closed-form solutions for static, buckling and vibration analysis of simply supported FG sandwich beams are obtained using Navier’s solution technique. The non-dimensional numerical results are obtained for various power law index and skin-core-skin thickness ratios. The present results are compared with previously published results and found in excellent agreement. تفاصيل المقالة -
حرية الوصول المقاله
46 - Displacement Fields Influence Analysis Caused by Dislocation Networks at a Three Layer System Interfaces on the Surface Topology
A Boussaha R Makhloufi S MadaniThis work consists in a numerically evaluation of elastic fields distribution, caused by intrinsic dislocation networks placed at a nanometric trilayers interfaces, in order to estimate their influence on the surface topology during heterostructure operation. The organi أکثرThis work consists in a numerically evaluation of elastic fields distribution, caused by intrinsic dislocation networks placed at a nanometric trilayers interfaces, in order to estimate their influence on the surface topology during heterostructure operation. The organization of nanostructures is ensured by the knowledge of different elastic fields caused by buried dislocation networks and calculated in the case of anisotropic elasticity. The influence of elastic fields generated by induced square and parallel dislocation networks at CdTe / GaAs / (001) GaAs trilayer interfaces was investigated. By deposition, the nanostructures organization with respect to the topology was controled. تفاصيل المقالة -
حرية الوصول المقاله
47 - Effect of Temperature Dependency on Thermoelastic Behavior of Rotating Variable Thickness FGM Cantilever Beam
M.M.H Mirzaei A Loghman M ArefiThermoelastic behavior of temperature-dependent (TD) and independent (TID) functionally graded variable thickness cantilever beam subjected to mechanical and thermal loadings is studied based on shear deformation theory using a semi-analytical method. Loading is compose أکثرThermoelastic behavior of temperature-dependent (TD) and independent (TID) functionally graded variable thickness cantilever beam subjected to mechanical and thermal loadings is studied based on shear deformation theory using a semi-analytical method. Loading is composed of a transverse distributed force, a longitudinal distributed temperature field due to steady-state heat conduction from root to the tip surface of the beam and an inertia body force due to rotation. A successive relaxation (SR) method for solving temperature-dependent steady-state heat conduction equation is employed to obtain the accurate temperature field. The beam is made of functionally graded material (FGM) in which the mechanical and thermal properties are variable in longitudinal direction based on the volume fraction of constituent. Using first-order shear deformation theory, linear strain–displacement relations and Generalized Hooke’s law, a system of second order differential equation is obtained. Using division method, differential equations are solved for every division. As a result, longitudinal displacement, transverse displacement, and consequently longitudinal stress, shear stress and effective stress are investigated. The results are presented for temperature dependent and independent properties. It has been found that the temperature dependency of the material has a significant effect on temperature distribution, displacements and stresses. This model can be used for thermoelastic analysis of simple turbine blades. تفاصيل المقالة -
حرية الوصول المقاله
48 - Linear and Nonlinear Free Vibration of a Two-Dimensional Multiferroic Composite Plate Subjected to Magneto-Electro-Thermo-Aerodynamic Loading
S Razavi H Ghashochi BarghVibration response of a two-dimensional magneto-electro-elastic plate is investigated in this paper. The considered multi-phase plate is rectangular and simply-supported resting on an elastic foundation. The plate is under aerodynamic pressure and subjected to temperatu أکثرVibration response of a two-dimensional magneto-electro-elastic plate is investigated in this paper. The considered multi-phase plate is rectangular and simply-supported resting on an elastic foundation. The plate is under aerodynamic pressure and subjected to temperature change. It is also assumed that the magneto-electro-elastic body is poled along the z direction and subjected to electric and magnetic potentials between the upper and lower surfaces. The nonlinear vibrational analysis of the described plate is considered as an innovation of the present paper,which had not been done before. To model this problem, third-order shear deformation theory along with Gauss’s laws for electrostatics and magnetostatics, first-order piston theory, and Galerkin and multiple times scale methods are used. After validating the presented method, effects of several parameters on the natural frequency, time history, backbone curve, and phase plane diagram of this smart composite plate are obtained. It is found that for plates with constant a/h ratio, electric and magnetic potentials have noticeable effects on the time histories, phase plane diagrams and backbone curves of the plates with smaller thicknesses. In addition, the numerical results of this research indicate that some parameters have considerable effect on the vibration behavior of presented plate. Elastic parameters of the foundation, applied electric and magnetic potentials, and environment temperature are important parameters in this analysis. تفاصيل المقالة -
حرية الوصول المقاله
49 - Nonlocal Dispersion Analysis of a Fluid – Conveying Thermo Elastic Armchair Single Walled Carbon Nanotube Under Moving Harmonic Excitation
M Mahaveersree Jayan R Kumar R Selvamani J RexyIn this work, the nonlocal elastic waves in a fluid conveying armchair thermo elastic single walled carbon nanotube under moving harmonic load is studied using Eringen nonlocal elasticity theory via Euler Bernoulli beam equation. The governing equations that contains pa أکثرIn this work, the nonlocal elastic waves in a fluid conveying armchair thermo elastic single walled carbon nanotube under moving harmonic load is studied using Eringen nonlocal elasticity theory via Euler Bernoulli beam equation. The governing equations that contains partial differential equations for single walled carbon nanotube is derived by considering thermal and Lorenz magnetic force. The small scale interactions induced by the nano tubes are simulated by the non-local effects. The time domain responses are obtained by using both modal super position method and Newmarks’s direct integration method. The effect of nonlocal parameter, thermal load, magnetic field of the moving harmonic load on the dynamic displacement of SWCNT is discussed. The results obtained show that the dynamic displacement of fluid conveying SWCNT ratio is significantly affected by the load velocity and the excitation frequency. This type of results presented here, will provide useful information for researchers in structural nano science to understand the small scale response of elastic waves coupled with thermo elasticity and some field forces. تفاصيل المقالة -
حرية الوصول المقاله
50 - Numerical Analysis of the Effect of External Circumferential Cracks in Transition Thickness Zone of Pressurized Pipes Using XFEM – Elastic-Plastic Behavior
H Salmi Kh EL Had H EL Bhilat A HachimThe elastic-plastic behavior of the material is considered to analyze the effect of an external circumferential crack on a pipe with thickness transitionand double slopes. Using the extended finite element method (XFEM), the J-integral of 3D cracks were investigated and أکثرThe elastic-plastic behavior of the material is considered to analyze the effect of an external circumferential crack on a pipe with thickness transitionand double slopes. Using the extended finite element method (XFEM), the J-integral of 3D cracks were investigated and compared between straight pipes and pipes with thickness transition and different slopes. Considering internal pressure, this work highlighted the investigation of a 3D crack problem ina thickness transition pipe with a double slope,In the extended finite element method (XFEM), the level sets and the enrichment zone were defined. A crack is easily modeled by enrichment functions. The comparison between the values of the J-integral showed that the pipe containing thickness transition with double slopes is more sensitive to the considered cracks, more precisely, the parameters of the first thickness transition have more influence on the variation of J-integral than the parameters of the second thickness transition. The decreasing of the angle of the slopes and the increase of the ratio of the thicknesses is one effective method of reducing the J-integral. تفاصيل المقالة -
حرية الوصول المقاله
51 - Non-Linear Response of Torsional Buckling Piezoelectric Cylindrical Shell Reinforced with DWBNNTs Under Combination of Electro-Thermo-Mechanical Loadings in Elastic Foundation
M Sarvandi M.M Najafizadeh H SeyyedhasaniNanocomposites provide new properties and exploit unique synergism between materials. Polyvinylidene fluoride (PVDF) is an ideal piezoelectric matrix applicable in nanocomposites in a broad range of industries from oil and gas to electronics and automotive. And boron ni أکثرNanocomposites provide new properties and exploit unique synergism between materials. Polyvinylidene fluoride (PVDF) is an ideal piezoelectric matrix applicable in nanocomposites in a broad range of industries from oil and gas to electronics and automotive. And boron nitride nanotubes (BNNTs) show high mechanical, electrical and chemical properties. In this paper, the critical torsional load of a composite tube made of PVDF reinforced with double-walled BNNTs is investigated, under a combination of electro-thermo-mechanical loading. First, a nanocomposite smart tube is modeled as an isotropic cylindrical shell in an elastic foundation. Next, employing the classical shell theory, strain-displacement equations are derived so loads and moments are obtained. Then, the total energy equation is determined, consisting of strain energy of shell, energy due to external work, and energy due to elastic foundation. Additionally, equilibrium equations are derived in cylindrical coordinates as triply orthogonal, utilizing Euler equations; subsequently, stability equations are developed through the equivalent method in adjacent points. The developed equations are solved using the wave technique to achieve critical torsional torque. Results indicated that critical torsional buckling load occurred in axial half-wave number m = 24 and circumferential wave number n = 1, for the investigated cylindrical shell. The results also showed that with the increase in the length-to-radius ratio and in the radius-to-shell thickness ratio, the critical torsional buckling load increased and decreased, respectively. Lastly, results are compared in various states through a numerical method. Moreover, stability equations are validated via comparison with the shell and sheet equations in the literature. تفاصيل المقالة -
حرية الوصول المقاله
52 - On The Free Vibration of Doubly Clamped Single-Walled Coiled Carbon Nanotubes: A Novel Size Dependent Continuum Model
F Darvishi O RahmaniIn this paper, the size dependent vibration behavior of doubly clamped single-walled coiled carbon nanotubes (CCNTs) is investigated using nonlocal helical beam model. This model is based on Washizu’s beam theory so that all displacement components of CCNT in the أکثرIn this paper, the size dependent vibration behavior of doubly clamped single-walled coiled carbon nanotubes (CCNTs) is investigated using nonlocal helical beam model. This model is based on Washizu’s beam theory so that all displacement components of CCNT in the equations of motion are defined at the centroidal principal axis and transverse shear deformations are considered. After deriving the nonlocal free vibration equations, they are solved by the generalized differential quadrature method (GDQM). Then, the natural frequencies and corresponding mode shapes are determined for the clamped-clamped boundary conditions (BCs). After that, a parametric study on the effect of different parameters, including the helix cylinder to the tube diameters ratio , the number of pitches, the helix pitch angle, and the nonlocal parameter on the natural frequencies is conducted. It is worth noting that the results of the proposed method would be useful in the practical applications of CCNTs such as using in nanoelectromechanical systems. تفاصيل المقالة -
حرية الوصول المقاله
53 - Vibration Analysis of a Magneto Thermo Electrical Nano Fiber Reinforced with Graphene Oxide Powder Under Refined Beam Model
R Selvamani J Rexy F EbrahimiThe present article express the magneto thermo electric deformation of composite nano fiber reinforced by graphene oxide powder (GOP). To reach the governing equation of the problem a higher-order trigonometric refined beam model is utilized according to Hamilton’ أکثرThe present article express the magneto thermo electric deformation of composite nano fiber reinforced by graphene oxide powder (GOP). To reach the governing equation of the problem a higher-order trigonometric refined beam model is utilized according to Hamilton’s principle. The effect of a nonuniform magnetic and thermo piezo electric field is applied to the governing equations by combining the field relations with the displacement field equations. Then, obtained equations are solved by using Galerkin’s method to consider the influence of different boundary conditions on the vibrational responses of the fiber. The accuracy and efficiency of the presented model is verified by comparing the results with that of published researches. Further, the effects of different variant on the dimensionless frequency of GOP reinforced magneto piezo thermo elastic composite fibers are highlighted through tables and dispersion curves. The weight fraction of GOP and the magneto thermo electro effects have significant influence in the stiffness of the nano composites. تفاصيل المقالة -
حرية الوصول المقاله
54 - Free Vibration Analysis of Bidirectional Functionally Graded Conical/Cylindrical Shells and Annular Plates on Nonlinear Elastic Foundations, Based on a Unified Differential Transform Analytical Formulation
M Molla-Alipour M Shariyat M ShabanIn the present research, a unified formulation for free vibration analysis of the bidirectional functionally graded conical and cylindrical shells and annular plates on elastic foundations is developed. To cover more individual cases and optimally tailored material prop أکثرIn the present research, a unified formulation for free vibration analysis of the bidirectional functionally graded conical and cylindrical shells and annular plates on elastic foundations is developed. To cover more individual cases and optimally tailored material properties, the material properties are assumed to vary in both the meridian/radial and transverse directions. The shell/plate is assumed to be supported by a non-uniform Winkler-type elastic foundation in addition to the edge constraints. Therefore, the considered problem contains some complexities that have not been considered together in the available researches. The proposed unified formulation is derived based on the principle of minimum total potential energy and solved using a differential transform analytical method whose center is located at the outer edge of the shell or plate; so that the resulting semi-analytical solution can be employed not only for truncated conical shells and annular plates, but also for complete conical shells and circular plates. Accuracy of results of the proposed unified formulation is verified by comparing the results with those of the three-dimensional theory of elasticity extracted from the ABAQUS finite element analysis code. A variety of the edge condition combinations are considered in the results section. A comprehensive parametric study including assessment of influences of the material properties indices, thickness to radius ratio, stiffness distribution of the elastic foundation, and various boundary conditions, is accomplished. Results reveal that influence of the meridian variations of the material properties on the natural frequencies is more remarkable than that of the transverse gradation. تفاصيل المقالة -
حرية الوصول المقاله
55 - A Generalized Thermo-Elastic Diffusion Problem in a Functionally Graded Rotating Media Using Fractional Order Theory
K Paul B MukhopadhyayA generalized thermo-elastic diffusion problem in a functionally graded isotropic, unbounded, rotating elastic medium due to a periodically varying heat source in the context of fractional order theory is considered in our present work. The governing equations of the th أکثرA generalized thermo-elastic diffusion problem in a functionally graded isotropic, unbounded, rotating elastic medium due to a periodically varying heat source in the context of fractional order theory is considered in our present work. The governing equations of the theory for a functionally graded material with GNIII model are established. Analytical solution of the problem is derived in Laplace-Fourier transform domain. Finally, numerical inversions are used to show the effect of rotation, non-homogeneity and fractional parameter on stresses, displacement, chemical potential, mass distribution, temperature, etc. and those are illustrated graphically. تفاصيل المقالة -
حرية الوصول المقاله
56 - Thermoelastic Damping and Frequency Shift in Kirchhoff Plate Resonators Based on Modified Couple Stress Theory With Dual-Phase-Lag Model
S Devi R KumarThe present investigation deals with study of thermoelastic damping and frequency shift of Kirchhoff plate resonators by using generalized thermoelasticity theory of dual-phase-lag model. The basic equations of motion and heat conduction equation are written with the he أکثرThe present investigation deals with study of thermoelastic damping and frequency shift of Kirchhoff plate resonators by using generalized thermoelasticity theory of dual-phase-lag model. The basic equations of motion and heat conduction equation are written with the help of Kirchhoff-Love plate theory and dual phase lag model. The analytical expressions for thermoelastic damping and frequency shift of modified couple stress dual-phase-lag thermoelastic plate have been obtained. A computer algorithm has been constructed to obtain the numerical results. Influences of modified couple stress dual-phase-lag thermoelastic plate, dual- phase-lag thermoelastic plate and Lord-Shulman (L-S, 1967) thermoelastic plate with few vibration modes on the thermoelastic damping and frequency shift are examined. The thermoelastic damping and frequency shift with varying values of length and thickness are shown graphically for clamped-clamped and simply-supported boundary conditions. It is observed from the results that the damping factor and frequency shift have noticed larger value in the presence of couple stress for varying values of length but opposite effect are shown for varying values of thickness in case of both vibration modes and boundary conditions. تفاصيل المقالة -
حرية الوصول المقاله
57 - Considering Bending and Vibration of Homogeneous Nanobeam Coated by a FG Layer
H Salehipour M Jamshidi A ShahsavarIn this research static deflection and free vibration of homogeneous nanobeams coated by a functionally graded (FG) layer is investigated according to the nonlocal elasticity theory. A higher order beam theory is used that does not need the shear correction factor. The أکثرIn this research static deflection and free vibration of homogeneous nanobeams coated by a functionally graded (FG) layer is investigated according to the nonlocal elasticity theory. A higher order beam theory is used that does not need the shear correction factor. The equations of motion (equilibrium equations) are extracted by using Hamilton’s principle. The material properties are considered to vary in the thickness direction of FG coated layer. This nonlocal nanobeam model incorporates the length scale parameter (nonlocal parameter) that can capture the small scale effects. In the numerical results section, the effects of different parameters, especially the ratio of thickness of FG layer to the total thickness of the beam are considered and discussed. The results reveal that the frequency is maximum for a special value of material power index. Also, increasing the ratio of thickness of FG layer to the total thickness of the beam increases the static deflection and decreases the natural frequencies. These results help with the understanding such coated structures and designing them carefully. The results also show that the new nonlocal FG nanobeam model produces larger vibration and smaller deflection than homogeneous nonlocal nanobeam. تفاصيل المقالة -
حرية الوصول المقاله
58 - Fundamental Solution and Study of Plane Waves in Bio-Thermoelastic Medium with DPL
R Kumar A.K Vashishth S GhangasThe fundamental solution of the system of differential equations in bio-thermoelasticity with dual phase lag (DPL) in case of steady oscillations in terms of elementary function is constructed and basic property is established. The tissue is considered as an isotropic m أکثرThe fundamental solution of the system of differential equations in bio-thermoelasticity with dual phase lag (DPL) in case of steady oscillations in terms of elementary function is constructed and basic property is established. The tissue is considered as an isotropic medium and the propagation of plane harmonic waves is studied. The Christoffel equations are obtained and modified with the thermal as well as bio thermoelastic coupling parameters. These equations explain the existence and propagation of three waves in the medium. Two of the waves are attenuating longitudinal waves and one is non-attenuating transverse wave. The thermal property has no effect on the transverse wave. The velocities and attenuating factors of longitudinal waves are computed for a numerical bioheat transfer model with phase lag. The variation with frequency, thermal parameters, blood perfusion parameter and phase lag parameter are presented graphically. Also the reflection of plane wave from a stress free isothermal boundary of isotropic bio-thermoelastic half space in the context of DPL theory of thermoelasticity is studied. The amplitude ratios of various reflected waves are obtained and these amplitude ratios are further used to obtain the energy ratios of various reflected waves. These energy ratios are function of the angle of incidence and bio-thermoelastic properties of the medium. The expressions of energy ratios have been computed numerically for a particular model to show the effect of Poisson ratio, blood perfusion rate and phase lag parameters. تفاصيل المقالة -
حرية الوصول المقاله
59 - Analysis of Reflection Phenomena in a Fiber Reinforced Piezo-Thermoelastic Half Space with Diffusion and Two-Temperature
K Jain S Kumar S DeswalPresent work is concerned with the analysis of transient wave phenomena in a piezo-thermoelastic medium with diffusion, fiber reinforcement and two-temperature, when an elastic wave is made incident obliquely at the traction free plane boundary of the considered medium. أکثرPresent work is concerned with the analysis of transient wave phenomena in a piezo-thermoelastic medium with diffusion, fiber reinforcement and two-temperature, when an elastic wave is made incident obliquely at the traction free plane boundary of the considered medium. The formulation is applied under the purview of generalized theory of thermoelasticity with one relaxation time. The problem is solved analytically and it is found that there exists four coupled quasi waves: qp (quasi-p ), qMD (quasi mass diffusion), qT (quasi thermal) and qSV (quasi-SV ) waves propagating with different speeds in a two-dimensional model of the solid. The amplitude ratios, phase velocities and energy ratios for the reflected waves are derived and the numerical computations have been carried out with the help of MATLAB programming. Effect of presence of diffusion is analyzed theoretically, numerically and graphically. The number of reflected waves reduce to three in the absence of diffusion as qMD wave will disappear in that case which is physically admissible. Influence of piezoelectric effect, two temperature and anisotropy is discussed on different characteristics of reflected waves such as phase velocity and reflection coefficients. It has been verified that there is no dissipation of energy at the boundary surface during reflection. Thus, the energy conservation law holds at the surface. Finally, all the reflection coefficients are represented graphically through 3D plots to estimate and highlight the effects of frequency and angle of incidence. تفاصيل المقالة -
حرية الوصول المقاله
60 - Deformation Field Produced by a Doublet Source in a Half-Space Model
N Verma K SinghUsing Galerkin vector approach closed-form analytic expressions for the displacements and stresses caused by a doublet source buried in a homogenous, isotropic, perfectly elastic half-space have been obtained. Further, the viscoelastic deformation field has been obtaine أکثرUsing Galerkin vector approach closed-form analytic expressions for the displacements and stresses caused by a doublet source buried in a homogenous, isotropic, perfectly elastic half-space have been obtained. Further, the viscoelastic deformation field has been obtained by applying the correspondence principle of linear viscoelasticity, assuming the medium to be elastic in dilatation and Kelvin, Maxwell, or SLS (Standard linear solid) type viscoelastic in distortion. The effect of Poisson’s ratio on the deformation field due to a doublet source is examined in elastic half-space. The effect of relaxation time on displacement and stress fields is studied due to a doublet source in viscoelastic half-space. The variation of the displacements and stresses with the epicentral distance is studied graphically using MATLAB software. Stresses for a doublet with axis parallel to x-axis attain minimum value for Poissonian half- space. Viscoelastic displacements and stresses attain maxima for the Maxwell model and minima for the Kelvin model. تفاصيل المقالة -
حرية الوصول المقاله
61 - Vibrations of Inhomogeneous Viscothermoelastic Nonlocal Hollow Sphere under the effect of Three-Phase-Lag Model
S.R Sharma M.K Sharma D.K SharmaHerein, the free vibrations of inhomogeneous nonlocal viscothermoelastic sphere with three-phase-lag model of generalized thermoelasticity have been addressed. The governing equations and constitutive relations with three-phase-lag model have been solved by using non-di أکثرHerein, the free vibrations of inhomogeneous nonlocal viscothermoelastic sphere with three-phase-lag model of generalized thermoelasticity have been addressed. The governing equations and constitutive relations with three-phase-lag model have been solved by using non-dimensional quantities. The simple power law has been presumed to take the material in radial direction. The series solution has been established to derive the solution analytically. The relations of frequency equations for the continuation of viable modes are developed in dense form. The analytical results have been authenticated by the reduction of nonlocal and three–phase–lag parameters. To investigate the quality of vibrations, frequency equations are determined by applying the numerical iteration method. MATLAB software tools have been used for numerical computations and simulations to present the results graphically subject to natural frequencies, frequency shift, and thermoelastic damping. The numerical results clearly show that the variation of vibrations is slightly larger in case of nonlocal elastic sphere in contrast to elastic sphere. تفاصيل المقالة -
حرية الوصول المقاله
62 - Characterization of the Viscoelastic Q-Factor of Electrically Actuated Rectangular Micro-Plates
E Keykha H Rahmani H Moeinkhah M Salehi KolahiRegarding the necessity of designing high Q-resonators in micro electromechanical systems, this paper investigates the viscoelastic behavior of a rectangular micro-plate subjected to electrical actuation. Equations governing the vibrations of the homogeneous plate were أکثرRegarding the necessity of designing high Q-resonators in micro electromechanical systems, this paper investigates the viscoelastic behavior of a rectangular micro-plate subjected to electrical actuation. Equations governing the vibrations of the homogeneous plate were obtained on the basis of classical plate theory (Kirchhoff's model). The Kelvin–Voigt model was also employed to consider the viscoelastic properties. The Galerkin decomposition method was used for decomposition of the governing differential equations. Additionally, the effects of various parameters were investigated on the Q-factor. Furthermore, a Finite Element simulation is carried out using COMSOL Multiphysics. The verification of the proposed model was conducted by comparing the obtained results with those from previous studies which revealed the validity of the proposed approach and the accuracy of the assumptions made The suggested design approach proposed in this this study is expected to design high Q-factor micro resonators and may be used to improve the performance of many MEMS devices. تفاصيل المقالة -
حرية الوصول المقاله
63 - Elasticity Exact Solution for an FGM Cylindrical Shaft with Piezoelectric Layers Under the Saint-Venant Torsion by Using Prandtl’s Formulation
M. R Eslami M Jabbari A Eskandarzadeh SabetFunctionally graded materials (FGMs) belong to a noble family of composite material possess material properties varying gradually in a desired direction or orientation. In a past decade, functionally graded materials were remained in an interest of material investigator أکثرFunctionally graded materials (FGMs) belong to a noble family of composite material possess material properties varying gradually in a desired direction or orientation. In a past decade, functionally graded materials were remained in an interest of material investigators due to its prominent features, and have extensively used in almost every discipline of engineering which in turn significantly increases the number of research publication of FGM. In this paper the exact elasticity solution for an FGM circular shaft with piezo layers is analysed. piezoelectric layers are homogeneous and the modulus of elasticity for FGM varies continuously with the form of an exponential function. The shear modulus of the non-homogeneous FGM shaft is a given function of the Prandtl’s stress function of considered circular shaft when its material is homogeneous. state equations are derived. The Prandtl’s stress function and electric displacement potential function satisfy all conditions. The shearing stresses, torsional rigidity, torsional function for FGM layer and shearing stresses, electric displacements, torsional rigidity, electrical torsional rigidity ,torsional and electrical potential functions for piezoelectric layers are obtained. Exact analytical solution for hollow circular cross-section presented. At the end some graphs and conclusions are given. تفاصيل المقالة -
حرية الوصول المقاله
64 - Anisotropic and Isotropic Elasticity Applied for the Study of Elastic Fields Generated by Interfacial Dislocations in a Heterostructure of InAs/(001)GaAs Semiconductors
R Makhloufi A Boussaha R Benbouta L BarouraThis work is a study of the elastic fields’ effect (stresses and displacements) caused by dislocations networks at a heterostructure interface of a InAs / GaAs semiconductors thin system in the cases of isotropic and anisotropic elasticity. The numerical study of أکثرThis work is a study of the elastic fields’ effect (stresses and displacements) caused by dislocations networks at a heterostructure interface of a InAs / GaAs semiconductors thin system in the cases of isotropic and anisotropic elasticity. The numerical study of this type of heterostructure aims to predict the behavior of the interface with respect to these elastic fields satisfying the boundary conditions. The method used is based on a development in Fourier series. The deformation near the dislocation is greater than the other locations far from the dislocation. تفاصيل المقالة -
حرية الوصول المقاله
65 - Response of Two-Temperature on the Energy Ratios at Elastic-Piezothermoelastic Interface
R Kumar P SharmaIn the present investigation the reflection and transmission phenomenon of plane waves between two half spaces elastic and orthotropic piezothermoelastic with two-temperature theory is discussed. A piezothermoelastic solid half space is assumed to be loaded with an elas أکثرIn the present investigation the reflection and transmission phenomenon of plane waves between two half spaces elastic and orthotropic piezothermoelastic with two-temperature theory is discussed. A piezothermoelastic solid half space is assumed to be loaded with an elastic half space. Due to the phenomenon, four qausi waves are obtained; quasi longitudinal (qP) wave, quasi transverse (qS) wave, quasi thermal (qT) wave and electric potential wave (eP). It is found that the amplitude ratios of various reflected and refracted waves are functions of angle of incidence, frequency of incident wave and are influenced by the piezothermoelastic properties of media. The energy ratios are computed numerically using amplitude ratios for a particular model of graphite and cadmium selenide (CdSe). The variations of energy ratios with angle of incidence are shown graphically depicting the effect of two-temperature. The conservation of energy across the interface is justified. A particular case of interest is also deduced from the present investigation. تفاصيل المقالة -
حرية الوصول المقاله
66 - An Interval Parametric Approach for the Solution of One Dimensional Generalized Thermoelastic Problem
S Mandal S Pal Sarkar T Kumar RoyThis paper is presenting the solutions of the one dimension generalized thermo-elastic coupled equations by considering some thermo-elastic constants as interval numbers. As most of the elastic constants are obtained using the experimental methods. Thus there might be s أکثرThis paper is presenting the solutions of the one dimension generalized thermo-elastic coupled equations by considering some thermo-elastic constants as interval numbers. As most of the elastic constants are obtained using the experimental methods. Thus there might be some deficiency of exactness to obtain such constants. This kind of deficiency might cause the results on a micro-scale. L-S model has been considered to study the effect of such an interval parametric approach to generalized thermoelasticity. Laplace transform method applied to obtain a system of coupled ordinary differential equations. Then the vector-matrix differential form is used to solve these equations by the eigenvalue approach in Laplace transformed domain. The solution in the space-time domain obtained numerically. The numerical solutions obtained by using some suitable inverse transformation method. The solutions are graphically represented for different values of the parameter of interval parametric form and the significance of obtained results are described along with the behavior of the solutions. تفاصيل المقالة -
حرية الوصول المقاله
67 - Free Vibration Analysis of Elastically Connected Beams with Step
H Nayebi M.M NajafizadehIn this study, free vibration of stepped beam which is parallel to a uniform beam with same length and elastically connected to it, is considered. Euler-Bernoulli beam theory has been applied to drive equations of motion, abrupt change in height of beam considered as st أکثرIn this study, free vibration of stepped beam which is parallel to a uniform beam with same length and elastically connected to it, is considered. Euler-Bernoulli beam theory has been applied to drive equations of motion, abrupt change in height of beam considered as step and Winkler-type elastic layer model serve as connection between beams. The differential transform method (DTM) is applied to determine dimensionless frequencies and mode shapes. In the case of two uniform parallel beams accuracy of solution is verified by comparing with results reported by other methods. It is assumed all supports have one type and fully clamped and fully hinged supports considered for boundary conditions. The effects of different parameters such as: step location and ratio, connecting layer coefficient and boundary conditions on dimensionless frequencies and mode shapes investigated and discussed. This problem handled for first time in present study and results are completely new. تفاصيل المقالة -
حرية الوصول المقاله
68 - Analysis of Nanoplate with a Central Crack Under Distributed Transverse Load Based on Modified Nonlocal Elasticity Theory
M Rajabi H Lexian A RajabiIn this paper, using the complete modified nonlocal elasticity theory, the deflection and strain energy equations of rectangular nanoplates, with a central crack, under distributed transverse load were overwritten. First, the deflection of nanoplate was obtained using L أکثرIn this paper, using the complete modified nonlocal elasticity theory, the deflection and strain energy equations of rectangular nanoplates, with a central crack, under distributed transverse load were overwritten. First, the deflection of nanoplate was obtained using Levy's solution and consuming it; strain energy of nanoplate was found. As regards nonlocal elasticity theory wasn’t qualified for predicting the static behavior of nanoplates under distributed transverse load, using modified nonlocal elasticity theory, the deflection of nanoplate with a central crack for different values of the small-scale effect parameter was achieved. It was gained with the convergence condition for the complete modified nonlocal elasticity theory. To verify the result, the results for the state of the small-scale effect parameter were placed equal to zero (plate with macro-scale) and then were compared with the numerical results as well as the classical analytical solution results available in the valid references. It was shown that the complete modified nonlocal elasticity theory does not show any singularity at the crack-tip unlike the classical theory; therefore, the method presented is a suitable method for analysis of the nanoplates with a central crack. تفاصيل المقالة -
حرية الوصول المقاله
69 - Finite Crack in a Thermoelastic Transversely Isotropic Medium Under Green-Naghdi Theory
S.K Panja S.C MandalIn this paper, we have studied a model of finite linear Mode-I crack in a thermoelastic transversely isotropic medium under Green Naghdi theory. The crack is subjected to a prescribed temperature and a known tensile stress. The plane boundary surface is considered as is أکثرIn this paper, we have studied a model of finite linear Mode-I crack in a thermoelastic transversely isotropic medium under Green Naghdi theory. The crack is subjected to a prescribed temperature and a known tensile stress. The plane boundary surface is considered as isothermal and all the field variables are sufficiently smooth. The heat conduction equation is written under two temperature theory (2TT) for Green Naghdi model which contains absolute temperature as well as conductive temperature. The analytical expressions of displacement components, stress components and temperature variables are obtained by normal mode analysis and matrix inversion method. Comparisons have been made within Green Naghdi (G-N) theory of type I, type II and type III for displacement, stress and absolute temperature variables against the crack width for a transversely isotropic material (Cobalt) by virtues of graphs. Also, Comparison have been made among displacement, thermal stress and absolute temperature for different depths. تفاصيل المقالة -
حرية الوصول المقاله
70 - An Approximate Thermo-Mechanical Solution of a Functionally Graded Cylinder Using Hybrid Integral Transform and Finite Element Method
M Dehghan A Moosaie M Zamani NejadThis article introduces a novel mixed method that combines the Fast Fourier Transform technique and a conventional Finite Element Method for investigating thermo-mechanical behavior of a thick functionally graded cylinder under asymmetric loadings. Material properties a أکثرThis article introduces a novel mixed method that combines the Fast Fourier Transform technique and a conventional Finite Element Method for investigating thermo-mechanical behavior of a thick functionally graded cylinder under asymmetric loadings. Material properties are assumed to vary along the radial direction according to a power function. Thermo-elastic governing equations of the cylinder are derived using principle of virtual work in cylindrical coordinates. Plane strain assumption is considered for a long cylinder during the analysis. Fast Fourier Transform technique is utilized in circumferential direction to discretize equations and related boundary conditions. Finite element method is then applied to remaining equations. For convergence study, the results obtained from this method are compared with those extracted from exact and complete FE solutions. It is observed from the results that the method has a super algebraic convergence behavior in circumferential direction. Influence of the mesh refinement is also investigated in the radial direction. According to ability of the mixed FFT-FE method for asymmetric analyzing, two kinds of loadings are considered here and results are presented. In thermo-elastic analyzing of the long cylinder, it’s obvious that the present method benefits from some features such as fast convergence and low computational cost in comparison with FE solution. تفاصيل المقالة -
حرية الوصول المقاله
71 - Analysis of Nonlinear Vibration of Piezoelectric Nanobeam Embedded in Multiple Layers Elastic Media in a Thermo-Magnetic Environment Using Iteration Perturbation Method
M.G SobamowoIn this work, analysis of nonlinear vibration of piezoelectric nanobeam in a thermo-magnetic environment embedded in Winkler, Pasternak, quadratic and cubic nonlinear elastic media for simply supported and clamped boundary conditions is presented. With the consideration أکثرIn this work, analysis of nonlinear vibration of piezoelectric nanobeam in a thermo-magnetic environment embedded in Winkler, Pasternak, quadratic and cubic nonlinear elastic media for simply supported and clamped boundary conditions is presented. With the considerations of Von- Karman geometric nonlinearity effect and with the aids of nonlocal elasticity theory as well as Euler–Bernoulli beam model, the equation of motion for the nanobeam is derived using Hamilton’s principle. The nonlinear dynamic model is solved using Galerkin-decomposition coupled with iteration perturbation method. From the parametric studies, it is shown that the frequency of the nanobeam increases at low temperatures but decreases at high temperatures. The nonlocal parameter decreases the frequencies of the piezoelectric nanobeam. An increase in the quadratic nonlinear elastic medium stiffness causes a decrease in the first mode of the nanobeam with clamped-clamped supports and an increase in all modes of the simply supported nanobeam at both low and high temperatures. When the magnetic force, cubic nonlinear elastic medium stiffness, and amplitude increase, there is an increase in all mode frequencies of the nanobeam. An increase in the temperature change at high temperature reduces the frequency ratio but at low or room temperature, an increase in temperature change, increases the frequency ratio of the structure nanotube. The significance of this study is evident in the design and applications of nanobeams in thermal and magnetic environments. تفاصيل المقالة -
حرية الوصول المقاله
72 - Large Deformation Hermitian Finite Element Coupled Thermoelasticity Analysis of Wave Propagation and Reflection in a Finite Domain
M Mirparizi M Shariyat A.R FotuhiIn the present paper, a finite element nonlinear coupled thermoelasticity formulation is presented for analysis of the wave propagation, reflection, and mixing phenomena in the finite length isotropic solids. The governing equations are derived based on the second Piola أکثرIn the present paper, a finite element nonlinear coupled thermoelasticity formulation is presented for analysis of the wave propagation, reflection, and mixing phenomena in the finite length isotropic solids. The governing equations are derived based on the second Piola-Kirchhoff stress and the full form of Green’s strain-displacement tensors to account for the large deformations and finite strains. In contrast to the available researches, the assumption of very small temperature changes compared to the reference temperature is released in the present research. Galerkin’s method, a weak formulation, and cubic elements are employed to obtain the time-dependent non-linear finite element governing equations. The proposed solution procedure to the resulting highly nonlinear and time-dependent governing equations employs an updating algorithm and Newmark’s numerical time integration method. The wave propagation and reflection phenomena are investigated for both the mechanical and thermal shocks and time variations of distributions of the resulting displacements, temperature rises, and stresses are illustrated graphically and discussed comprehensively. Furthermore, the effects of the non-linear terms are discussed comprehensively. Results reveal that in the non-linear analysis, no fixed speed of wave propagation can be defined. تفاصيل المقالة -
حرية الوصول المقاله
73 - Buckling and Free Vibrations of a Magneto-Electro-Elastic Sandwich Panel with Flexible Core
H Talebi Amanieh S.A Seyed Roknizadeh A RezaThis paper presents the buckling and out-of-plane free vibration response of a sandwich panel with flexible core for the different boundary condition. In the desired configuration of the sandwich panel, the top and bottom plates are made of magneto-electro-elastic (MEE) أکثرThis paper presents the buckling and out-of-plane free vibration response of a sandwich panel with flexible core for the different boundary condition. In the desired configuration of the sandwich panel, the top and bottom plates are made of magneto-electro-elastic (MEE) plates. Moreover, the in-plane electric and magnetic potential fields are neglected for the derivation of the required relations. The sandwich structure is subjected to axial force in both longitudinal and transverse directions; in addition, and the top and bottom plates are exposed to electric and magnetic fields. The governing equations of motion for MEE sandwich panel with a flexible core are derived based on the first-order shear deformation theory by neglecting the displacement of the mid-plate and using the Hamilton’s principle. Furthermore, the derived partial differential equations (PDEs) are solved. According to the obtained numerical results, the core thickness, variation of electric field, variation of magnetic field and plate length are introduced as the most influential parameters on the free vibration response of the panel as well as the critical force of buckling. As one of the results, the electric potential is inversely related to the natural frequency and buckling load, so that with increasing the electric potential, the natural frequency and critical load of the structure is also increased.Moreover, the magnetic potential is directly related to the natural frequency and buckling load of the system, and increasing trends of natural frequency and critical load are observed by increasing the magnetic potential. تفاصيل المقالة -
حرية الوصول المقاله
74 - Closed-Form Formulation for Bending Analysis of Functionally Graded Thick Plates
M Shaban M. J KhoshgoftarDue to their continuous material variation and eliminating the mismatch stress field in the thickness direction, Functionally Graded Materials (FGMs) have found wide applications in aerospace and mechanical engineering. This article presents closed-form solution for thi أکثرDue to their continuous material variation and eliminating the mismatch stress field in the thickness direction, Functionally Graded Materials (FGMs) have found wide applications in aerospace and mechanical engineering. This article presents closed-form solution for thick functionally graded plate based on three-dimensional elasticity theory. To this end, first, the characteristic equation of FG plate is derived and general closed-form is obtained analytically. Both positive and negative discriminant of characteristic equation is considered and solved. The presented method is validated with finite element results by considering isotropic thick plate. Several parametric studies are carried out to investigate the effect of geometric and material parameters. The aim of this research is to present analytical solution form for thick FG plate and work out the problem of inconsistency for corresponding displacements field. The presented solution can be used to examine accuracy of various plate theories such as first-order, third order shear deformation theories and other equivalent plate theories. تفاصيل المقالة -
حرية الوصول المقاله
75 - On the Aeroelastic Stability of a Two-Directional FG GNP-Enriched Conical Shell
A.R Shahidi A DarakhshIn this article, the supersonic flutter analysis of a truncated conical shell made of polymer enriched with graphene nanoplatelets (GNPs) exposed to supersonic fluid flow is discussed. It is assumed that the mass fraction of the GNPs is functionally graded (FG) along th أکثرIn this article, the supersonic flutter analysis of a truncated conical shell made of polymer enriched with graphene nanoplatelets (GNPs) exposed to supersonic fluid flow is discussed. It is assumed that the mass fraction of the GNPs is functionally graded (FG) along thickness and length directions according to different dispersion patterns. Modeling of the shell is done using the first-order shear deformation theory (FSDT), the mechanical properties are computed according to the Halpin-Tsai model alongside the rule of the mixture, and the aerodynamic pressure is computed utilizing the piston theory. Utilizing Hamilton’s principle, the boundary conditions and the governing equations are achieved. Harmonic trigonometric functions are used to provide an analytical solution in the circumferential direction and an approximate solution is presented in the meridional direction using the differential quadrature method (DQM). The efficacy of various parameters on the aeroelastic stability are discussed such as the percentage and dispersion pattern of the GNPs and gradient indices. It is observed that to achieve higher aeroelastic stability in the GNP-enriched truncated conical shells, it is better to dispense the GNPs near the small radius and the inner surface of the shell. تفاصيل المقالة -
حرية الوصول المقاله
76 - Torsion of Poroelastic Shaft with Hollow Elliptical Section
M Jabbari M.F KhansanamiIn this paper torsion of hollow Poroelastic shaft with Elliptical section is developed. Using the boundary equation scheme. It looks for a stress function where satisfied Poisson equation and vanishes on boundary. It also analyzed stress function and warping displacemen أکثرIn this paper torsion of hollow Poroelastic shaft with Elliptical section is developed. Using the boundary equation scheme. It looks for a stress function where satisfied Poisson equation and vanishes on boundary. It also analyzed stress function and warping displacement for the hollow elliptical section in Poroelastic shaft. At the end, the result of elastic and poroelastic shaft in warping displacement and stress function is compared. تفاصيل المقالة -
حرية الوصول المقاله
77 - A Problem of Axisymmetric Vibration of Nonlocal Microstretch Thermoelastic Circular Plate with Thermomechanical Sources
R Kumar R Rani A MiglaniIn the present manuscript, we investigated a two dimensional axisymmetric problem of nonlocal microstretch thermoelastic circular plate subjected to thermomechanical sources. An eigenvalue approach is proposed to analyze the problem. Laplace and Hankel transforms are us أکثرIn the present manuscript, we investigated a two dimensional axisymmetric problem of nonlocal microstretch thermoelastic circular plate subjected to thermomechanical sources. An eigenvalue approach is proposed to analyze the problem. Laplace and Hankel transforms are used to obtain the transformed solutions for the displacements, microrotation, microstretch, temperature distribution and stresses. The results are obtained in the physical domain by applying the numerical inversion technique of transforms. The results of the physical quantities have been obtained numerically and illustrated graphically. The results show the effect of nonlocal in the cases of Lord Shulman (LS), Green Lindsay (GL) and coupled thermoelasticity (CT) on all the physical quantities. تفاصيل المقالة -
حرية الوصول المقاله
78 - Vibration Analysis of Magneto-Electro-Elastic Timoshenko Micro Beam Using Surface Stress Effect and Modified Strain Gradient Theory under Moving Nano-Particle
M Mohammadimehr H Mohammadi HooyehIn this article, the free vibration analysis of magneto-electro-elastic (MEE) Timoshenko micro beam model based on surface stress effect and modified strain gradient theory (MSGT) under moving nano-particle is presented. The governing equations of motion using Hamilton& أکثرIn this article, the free vibration analysis of magneto-electro-elastic (MEE) Timoshenko micro beam model based on surface stress effect and modified strain gradient theory (MSGT) under moving nano-particle is presented. The governing equations of motion using Hamilton’s principle are derived and these equations are solved using differential quadrature method (DQM). The effects of dimensionless electric potential, dimensionless magnetic parameter, material length scale parameter, external electric voltage, external magnetic parameter, slenderness ratio, temperature change, surface stress effect, two parameters of elastic foundation on the dimensionless natural frequency are investigated. It is shown that the effect of electric potential and magnetic parameter simultaneously increases the dimensionless natural frequency. On the other hands, with considering two parameters, the stiffness of MEE Timoshenko micro beam model increases. It can be seen that the dimensionless natural frequency of micro structure increases by MSGT more than modified couple stress theory (MCST) and classical theory (CT). It is found that by increasing the mass of nano-particle, the dimensionless natural frequency of system decreases. The results of this study can be employed to design and manufacture micro-devices to prevent resonance phenomenon or as a sensor to control the dynamic stability of micro structures. تفاصيل المقالة -
حرية الوصول المقاله
79 - Magneto-Thermo-Elastic Behavior of Cylinder Reinforced with FG SWCNTs Under Transient Thermal Field
A Ghorbanpour Arani M.R Mozdianfard V Sadooghi M Mohammadimehr R KolahchiIn this article, magneto-thermo-elastic stresses and perturbation of magnetic field vector are analyzed for a thick-walled cylinder made from polystyrene, reinforced with functionally graded (FG) single-walled carbon nanotubes (SWCNTs) in radial direction, while subject أکثرIn this article, magneto-thermo-elastic stresses and perturbation of magnetic field vector are analyzed for a thick-walled cylinder made from polystyrene, reinforced with functionally graded (FG) single-walled carbon nanotubes (SWCNTs) in radial direction, while subjected to an axial and uniform magnetic field as well as a transient thermal field. Generalized plane strain state is considered in this study. The SWCNTs are assumed aligned, straight with infinite length. Two types of variations in the volume fraction of SWCNTs were considered in the structure of the FG cylinder along the radius from inner to outer surface, namely: functionally graded increasing (FG Inc) and functionally graded decreasing (FG Dec) which are then compared with uniformly distributed (UD) layouts. The constitutive equations of this type of reinforced polymeric cylinder are derived by Mori-Tanaka method. Following the introduction of a second order partial differential equation derived from the equations of motion and stress-strain relationships and solving by a semi-analytical method, distribution of stresses and perturbation of magnetic field vector are obtained. Results indicate that maximum radial and circumferential stresses occur in FG Inc and FG Dec layouts, respectively. Maximum perturbation of magnetic field vector is not affected by UD layout. تفاصيل المقالة -
حرية الوصول المقاله
80 - Frequency Analysis of Embedded Orthotropic Circular and Elliptical Micro/Nano-Plates Using Nonlocal Variational Principle
A Anjomshoa A.R Shahidi S.H Shahidi H NahviIn this paper, a continuum model based on the nonlocal elasticity theory is developed for vibration analysis of embedded orthotropic circular and elliptical micro/nano-plates. The nano-plate is bounded by a Pasternak foundation. Governing vibration equation of the nonlo أکثرIn this paper, a continuum model based on the nonlocal elasticity theory is developed for vibration analysis of embedded orthotropic circular and elliptical micro/nano-plates. The nano-plate is bounded by a Pasternak foundation. Governing vibration equation of the nonlocal nano-plate is derived using Nonlocal Classical Plate Theory (NCPT). The weighted residual statement and the Galerkin method are applied to obtain a Quadratic Functional. The Ritz functions are used to form an assumed expression for transverse displacement which satisfies the kinematic boundary conditions. The Ritz functions eliminate the need for mesh generation and thus large degrees of freedom arising in discretization methods such as Finite Element Method (FEM). Effects of nonlocal parameter, lengths of nano-plate, aspect ratio, mode number, material properties and foundation parameters on the nano-plate natural frequencies are investigated. It is shown that the natural frequencies depend on the non-locality of the micro/nano-plate, especially at small dimensions. تفاصيل المقالة -
حرية الوصول المقاله
81 - A Nonlocal First Order Shear Deformation Theory for Vibration Analysis of Size Dependent Functionally Graded Nano beam with Attached Tip Mass: an Exact Solution
M Ghadiri A JafariIn this article, transverse vibration of a cantilever nano- beam with functionally graded materials and carrying a concentrated mass at the free end is studied. Material properties of FG beam are supposed to vary through thickness direction of the constituents according أکثرIn this article, transverse vibration of a cantilever nano- beam with functionally graded materials and carrying a concentrated mass at the free end is studied. Material properties of FG beam are supposed to vary through thickness direction of the constituents according to power-law distribution (P-FGM). The small scale effect is taken into consideration based on nonlocal elasticity theory of Eringen. The nonlocal equations of motion are derived based on Timoshenko beam theory in order to consider the effect of shear deformation and rotary inertia. Hamilton’s principle is applied to obtain the governing differential equation of motion and boundary conditions and they are solved applying analytical solution. The purpose is to study the effects of parameters such as tip mass, small scale, beam thickness, power-law exponent and slenderness on the natural frequencies of FG cantilever nano beam with a point mass at the free end. It is explicitly shown that the vibration behavior of a FG Nano beam is significantly influenced by these effects. The response of Timoshenko Nano beams obtained using an exact solution in a special case is compared with those obtained in the literature and is found to be in good agreement. Numerical results are presented to serve as benchmarks for future analyses of FGM cantilever Nano beams with tip mass. تفاصيل المقالة -
حرية الوصول المقاله
82 - Thermomechanical Response in Thermoelastic Medium with Double Porosity
R Kumar R Vohra M.G GorlaA dynamic two dimensional problem of thermoelasticity with double porous structure has been considered to investigate the disturbance due to normal force and thermal source. Laplace and Fourier transform technique is applied to the governing equations to solve the probl أکثرA dynamic two dimensional problem of thermoelasticity with double porous structure has been considered to investigate the disturbance due to normal force and thermal source. Laplace and Fourier transform technique is applied to the governing equations to solve the problem. The transformed components of stress and temperature distribution are obtained .The resulting expressions are obtained in the physical domain by using numerical inversion technique. Numerically computed results for these quantities are depicted graphically to study the effect of porosity. Results of Kumar & Rani [42] and Kumar & Ailawalia [43] have also been deduced as special cases from the present investigation. تفاصيل المقالة -
حرية الوصول المقاله
83 - Exact 3-D Solution for Free Bending Vibration of Thick FG Plates and Homogeneous Plate Coated by a Single FG Layer on Elastic Foundations
H Salehipour R Hosseini K FiroozbakhshThis paper presents new exact 3-D (three-dimensional) elasticity closed-form solutions for out-of-plane free vibration of thick rectangular single layered FG (functionally graded) plates and thick rectangular homogeneous plate coated by a functionally graded layer with أکثرThis paper presents new exact 3-D (three-dimensional) elasticity closed-form solutions for out-of-plane free vibration of thick rectangular single layered FG (functionally graded) plates and thick rectangular homogeneous plate coated by a functionally graded layer with simply supported boundary conditions. It is assumed that the plate is on a Winkler-Pasternak elastic foundation and elasticity modulus and mass density of the FG layer vary exponentially through the thickness of the FG layer, whereas Poisson’s ratio is constant. In order to solve the equations of motion, a proposed displacement field is used for each layer. Influences of stiffness of the foundation, inhomogeneity of the FG layer and coating thickness-to-total thickness ratio on the natural frequencies of the plates are discussed. Numerical results presented in this paper can serve as benchmarks for future vibration analyses of single layered FG plates and coated plates on elastic foundations. تفاصيل المقالة -
حرية الوصول المقاله
84 - Effect of Rotation and Stiffness on Surface Wave Propagation in a Elastic Layer Lying Over a Generalized Thermodiffusive Elastic Half-Space with Imperfect Boundary
R Kumar V ChawlaThe present investigation is to study the surface waves propagation with imperfect boundary between an isotropic elastic layer of finite thickness and a homogenous isotropic thermodiffusive elastic half- space with rotation in the context of Green-Lindsay (G-L model) th أکثرThe present investigation is to study the surface waves propagation with imperfect boundary between an isotropic elastic layer of finite thickness and a homogenous isotropic thermodiffusive elastic half- space with rotation in the context of Green-Lindsay (G-L model) theory. The secular equation for surface waves in compact form is derived after developing the mathematical model. The phase velocity and attenuation coefficient are obtained for stiffness and then deduced for normal stiffness, tangential stiffness and welded contact. The dispersion curves for these quantities are illustrated to depict the effect of stiffness and thermal relaxation times. The amplitudes of displacements, temperature and concentration are computed at the free plane boundary. Specific loss of energy is obtained and presented graphically. The effects of rotation on phase velocity, attenuation coefficient and amplitudes of displacements, temperature change and concentration are depicted graphically. Some Special cases of interest are also deduced and compared with known results. تفاصيل المقالة -
حرية الوصول المقاله
85 - Closed Form Solution for Electro-Magneto-Thermo-Elastic Behaviour of Double-Layered Composite Cylinder
A Loghman H ParsaElectro-magneto-thermo-elastic response of a thick double-layered cylinder made from a homogeneous interlayer and a functionally graded piezoelectric material (FGPM) outer layer is investigated. Material properties of the FGPM layer vary along radius based on the power أکثرElectro-magneto-thermo-elastic response of a thick double-layered cylinder made from a homogeneous interlayer and a functionally graded piezoelectric material (FGPM) outer layer is investigated. Material properties of the FGPM layer vary along radius based on the power law distribution. The vessel is subjected to an internal pressure, an induced electric potential, a uniform magnetic field and a temperature gradient. Stresses and radial displacement are studied for different material in-homogeneity parameters in the FGPM layer. It has been shown that the material in-homogeneity parameters significantly affect the stress distribution in both layers. Therefore by selecting a suitable material parameter one can control stress distribution in both homogeneous and FGPM layers. It has been found that under electro-magneto-thermo-mechanical loading minimum effective stress can be achieved by selecting in the FGPM layer. تفاصيل المقالة -
حرية الوصول المقاله
86 - An Exact Solution for Classic Coupled Magneto-Thermo-Elasticity in Cylindrical Coordinates
M Jabbari H DehbaniIn this paper, the classic coupled Magneto-thermo-elasticity model of hollow and solid cylinders under radial-symmetric loading condition (r, t) is considered. A full analytical and the direct method based on Fourier Hankel series and Laplace transform is used, and an e أکثرIn this paper, the classic coupled Magneto-thermo-elasticity model of hollow and solid cylinders under radial-symmetric loading condition (r, t) is considered. A full analytical and the direct method based on Fourier Hankel series and Laplace transform is used, and an exact unique solution of the classic coupled equations is presented. The thermal and mechanical boundary conditions, the body force, the heat source and magnetic field vector are considered in the most general forms, where no limiting assumption is used. This generality allows to simulate a variety of applicable problems. The results are presented for thermal and mechanical shock, separately, and compare the effect of magnetic field on temperature and displacement. تفاصيل المقالة -
حرية الوصول المقاله
87 - Rubber/Carbon Nanotube Nanocomposite with Hyperelastic Matrix
M Motamedi M Moosavi MashhadiAnelastomeris apolymerwith the property ofviscoelasticity,generally having notably lowYoung's modulusand highyield straincompared with other materials. Elastomers, in particular rubbers, are used in a wide variety of products ranging from rubber hoses, isolation bearing أکثرAnelastomeris apolymerwith the property ofviscoelasticity,generally having notably lowYoung's modulusand highyield straincompared with other materials. Elastomers, in particular rubbers, are used in a wide variety of products ranging from rubber hoses, isolation bearings, and shock absorbers to tires. Rubber has good properties and is thermal and electrical resistant. We used carbon nanotube in rubber and modeled this composite with ABAQUS software. Because of hyperelastic behavior of rubber we had to use a strain energy function for nanocomposites modeling. A sample of rubber was tested and gained uniaxial, biaxial and planar test data and then the data used to get a good strain energy function. Mooney-Rivlin form, Neo-Hookean form, Ogden form, Polynomial form, reduced polynomial form, Van der Waals form etc, are some methods to get strain function energy. Modulus of elasticity and Poisson ratio and some other mechanical properties gained for a representative volume element (RVE) of composite in this work. We also considered rubber as an elastic material and gained mechanical properties of composite and then compared result for elastic and hyperelastic rubber matrix together. تفاصيل المقالة -
حرية الوصول المقاله
88 - Fractional Order Generalized Thermoelastic Functionally Graded Solid with Variable Material Properties
A Sur M KanoriaIn this work, a new mathematical model of thermoelasticity theory has been considered in the context of a new consideration of heat conduction with fractional order theory. A functionally graded isotropic unbounded medium is considered subjected to a periodically varyin أکثرIn this work, a new mathematical model of thermoelasticity theory has been considered in the context of a new consideration of heat conduction with fractional order theory. A functionally graded isotropic unbounded medium is considered subjected to a periodically varying heat source in the context of space-time non-local generalization of three-phase-lag thermoelastic model and Green-Naghdi models, in which the thermophysical properties are temperature dependent. The governing equations are expressed in Laplace-Fourier double transform domain and solved in that domain. Then the inversion of the Fourier transform is carried out by using residual calculus, where poles of the integrand are obtained numerically in complex domain by using Laguerre’s method and the inversion of Laplace transform is done numerically using a method based on Fourier series expansion technique. The numerical estimates of the thermal displacement, temperature and thermal stress are obtained for a hypothetical material. Finally, the obtained results are presented graphically to show the effect of non-local fractional parameter on thermal displacement, temperature and thermal stress. A comparison of the results for different theories (three-phase-lag model, GN model II, GN model III) is presented and the effect of non-homogeneity is also shown. The results, corresponding to the cases, when the material properties are temperature independent, agree with the results of the existing literature. تفاصيل المقالة -
حرية الوصول المقاله
89 - Reflection and Transmission at the Boundary of Two Couple Stress Generalized Thermoelastic Solids
R Kumar K Kumar R.C NautiyalIn this paper the reflection and transmission at a plane interface between two different couple stress generalized thermoelastic solid half spaces in context of Loard-Shulman(LS)[1967] and Green-Lindsay(GL)[1972] theories in welded contact has been investigated. Amplitu أکثرIn this paper the reflection and transmission at a plane interface between two different couple stress generalized thermoelastic solid half spaces in context of Loard-Shulman(LS)[1967] and Green-Lindsay(GL)[1972] theories in welded contact has been investigated. Amplitude ratios of various reflected and transmitted waves are obtained due to incidence of a set of coupled longitudinal waves and coupled transverse waves. It is found that the amplitude ratios of various reflected and transmitted waves are functions of angle of incidence, frequency and are affected by the couple stress properties of the media. Some special cases are deduced from the present formulation. تفاصيل المقالة -
حرية الوصول المقاله
90 - A Semi-Analytical Solution for Free Vibration and Modal Stress Analyses of Circular Plates Resting on Two-Parameter Elastic Foundations
M.M Alipour M Shariyat M ShabanIn the present research, free vibration and modal stress analyses of thin circular plates with arbitrary edge conditions, resting on two-parameter elastic foundations are investigated. Both Pasternak and Winkler parameters are adopted to model the elastic foundation. Th أکثرIn the present research, free vibration and modal stress analyses of thin circular plates with arbitrary edge conditions, resting on two-parameter elastic foundations are investigated. Both Pasternak and Winkler parameters are adopted to model the elastic foundation. The differential transform method (DTM) is used to solve the eigenvalue equation yielding the natural frequencies and mode shapes of the circular plates. Accuracy of obtained results is evaluated by comparing the results with those available in the well-known references. Furthermore, effects of the foundation stiffness parameters and the edge conditions on the natural frequencies, mode shapes, and distribution of the maximum in-plane modal stresses are investigated. تفاصيل المقالة -
حرية الوصول المقاله
91 - A Semi-analytical Approach to Elastic-plastic Stress Analysis of FGM Pressure Vessels
A.T Kalali S Hadidi-MoudAn analytical method for predicting elastic–plastic stress distribution in a cylindrical pressure vessel has been presented. The vessel material was a ceramic/metal functionally graded material, i.e. a particle–reinforcement composite. It was assumed that th أکثرAn analytical method for predicting elastic–plastic stress distribution in a cylindrical pressure vessel has been presented. The vessel material was a ceramic/metal functionally graded material, i.e. a particle–reinforcement composite. It was assumed that the material’s plastic deformation follows an isotropic strain-hardening rule based on the von-Mises yield criterion, and that the vessel was under plane-stress conditions. The mechanical properties of the graded layer were modelled by the modified rule of mixtures. By assuming small strains, Hencky’s stress–strain relation was used to obtain the governing differential equations for the plastic region. A numerical method for solving those differential equations was then proposed that enabledthe prediction of stress state within the structure. Selected finite element results were also presented to establish supporting evidence for the validation of the proposed analytical modelling approach. Similar analyses were performed and solutions for spherical pressure made of FGMs were also provided. تفاصيل المقالة -
حرية الوصول المقاله
92 - Free Vibrations of Continuous Grading Fiber Orientation Beams on Variable Elastic Foundations
S Kamarian M.H Yas A PourasgharFree vibration characteristics of continuous grading fiber orientation (CGFO) beams resting on variable Winkler and two-parameter elastic foundations have been studied. The beam is under different boundary conditions and assumed to have arbitrary variations of fiber ori أکثرFree vibration characteristics of continuous grading fiber orientation (CGFO) beams resting on variable Winkler and two-parameter elastic foundations have been studied. The beam is under different boundary conditions and assumed to have arbitrary variations of fiber orientation in the thickness direction. The governing differential equations for beam vibration are being solved using Generalized Differential Quadrature (GDQ) method. Numerical results are presented for a beam with arbitrary variation of fiber orientation in the beam thickness and compared with similar discrete laminate beam. The main contribution of this work is to present useful results for continuous grading of fiber orientation through thickness of a beam on variable elastic foundation and its comparison with similar discrete laminate composite beam. The results show the type of elastic foundation plays very important role on the natural frequency parameter of a CGFO beam. According to the numerical results, frequency characteristics of the CGFO beam resting on a constant Winkler elastic foundation is almost the same as of a composite beam with different fiber orientations for large values of Winkler elastic modulus, and fiber orientations has less effect on the natural frequency parameter. The interesting results show that normalized natural frequency of the CGFO beam is smaller than that of a similar discrete laminate beam and tends to the discrete laminated beam with increasing layers. It is believed that new results are presented for vibrational behavior of CGFO beams are of interest to the scientific and engineering community in the area of engineering design. تفاصيل المقالة -
حرية الوصول المقاله
93 - Dynamic Response of an Axially Moving Viscoelastic Timoshenko Beam
H Seddighi H.R EipakchiIn this paper, the dynamic response of an axially moving viscoelastic beam with simple supports is calculated analytically based on Timoshenko theory. The beam material property is separated to shear and bulk effects. It is assumed that the beam is incompressible in bul أکثرIn this paper, the dynamic response of an axially moving viscoelastic beam with simple supports is calculated analytically based on Timoshenko theory. The beam material property is separated to shear and bulk effects. It is assumed that the beam is incompressible in bulk and viscoelastic in shear, which obeys the standard linear model with the material time derivative. The axial speed is characterized by a simple harmonic variation about a constant mean speed. The method of multiple scales with the solvability condition is applied to dimensionless form of governing equations in modal analysis and principal parametric resonance. By a parametric study, the effects of velocity, geometry and viscoelastic parameters are investigated on the response. تفاصيل المقالة -
حرية الوصول المقاله
94 - Modeling of Compression Curves of Flexible Polyurethane Foam with Variable Density, Chemical Formulations and Strain Rates
M.F Alzoubi S Al-Hallaj M Abu-AyyadFlexible Polyurethane (PU) foam samples with different densities and chemical formulations were tested in quasi-static stress-strain compression tests. The compression tests were performed using the Lloyd LR5K Plus instrument at fixed compression strain rate of 0.033 s- أکثرFlexible Polyurethane (PU) foam samples with different densities and chemical formulations were tested in quasi-static stress-strain compression tests. The compression tests were performed using the Lloyd LR5K Plus instrument at fixed compression strain rate of 0.033 s-1 and samples were compressed up to 70% compression strains. All foam samples were tested in the foam rise direction and their compression test stress results were modeled using a constitutive Polymeric or Phenomenological Foam Model (PFM). In this research, a new constitutive PFM model that consists of mechanical systems such as dashpots and springs was formulated to be used for different strain rate experiments. The experimental compression test results for different strain rates were compared to the PFM model results for all foam samples. Both modeling and experimental results showed pretty good agreement. From curve fitting of the experimental tests with the PFM model; different mechanical materials’ coefficients such as elastic and viscous parameters were computed. These mechanical parameters are indeed important characteristics for viscoelastic materials. This model can be used for constant and variable strain rates and for characterizing biomechanical material applications such as bone tissues, muscle tissues and other cellular materials. تفاصيل المقالة -
حرية الوصول المقاله
95 - A Zigzag Theory with Local Shear Correction Factors for Semi-Analytical Bending Modal Analysis of Functionally Graded Viscoelastic Circular Sandwich Plates
M Shariyat M.M AlipourFree bending vibration analysis of the functionally graded viscoelastic circular sandwich plates is accomplished in the present paper, for the first time. Furthermore, local shear corrections factors are presented that may consider simultaneous effects of the gradual va أکثرFree bending vibration analysis of the functionally graded viscoelastic circular sandwich plates is accomplished in the present paper, for the first time. Furthermore, local shear corrections factors are presented that may consider simultaneous effects of the gradual variations of the material properties and the viscoelastic behaviors of the materials, for the first time. Moreover, in contrast to the available works, a global-local zigzag theory rather than an equivalent single-layer theory is employed in the analysis. Another novelty is solving the resulted governing equations by a power series that may cover several boundary conditions. To extract more general conclusions, sandwich plates with both symmetric and asymmetric (with a bending-extension coupling) layups are considered. Results are validated by comparing some of them with results of the three-dimensional theory of elasticity, even for the thick plates. Influences of various geometric and material properties parameters on free vibration of the circular sandwich plates are evaluated in detail in the results section. تفاصيل المقالة -
حرية الوصول المقاله
96 - Analysis of Plane Waves in Anisotropic Magneto-Piezothermoelastic Diffusive Body with Fractional Order Derivative
R Kumar P SharmaIn this paper the propagation of harmonic plane waves in a homogeneous anisotropic magneto-piezothermoelastic diffusive body with fractional order derivative is studied. The governing equations for a homogeneous transversely isotropic body in the context of the theory o أکثرIn this paper the propagation of harmonic plane waves in a homogeneous anisotropic magneto-piezothermoelastic diffusive body with fractional order derivative is studied. The governing equations for a homogeneous transversely isotropic body in the context of the theory of thermoelasticity with diffusion given by Sherief et al. [1] are considered as a special case. It is found that three types of waves propagate in one dimension anisotropic magneto-piezothermoelastic diffusive body, namely quasi-longitudinal wave (QP), quasi-thermal wave (QT) and quasi-diffusion wave (QD). The different characteristics of waves like phase velocity, attenuation coefficient, specific heat loss and penetration depth are computed numerically and presented graphically for Cadmium Selenide (CdSe) material. The effect of fractional order parameter on phase velocity, attenuation coefficient, specific heat loss and penetration depth has been studied. تفاصيل المقالة -
حرية الوصول المقاله
97 - Stress Analysis of Rotating Thick Truncated Conical Shells with Variable Thickness under Mechanical and Thermal Loads
M Jabbari M Zamani Nejad M GhannadIn this paper, thermo-elastic analysis of a rotating thick truncated conical shell subjected to the temperature gradient, internal pressure and external pressure is presented. Given the existence of shear stress in the conical shell due to thickness change along the axi أکثرIn this paper, thermo-elastic analysis of a rotating thick truncated conical shell subjected to the temperature gradient, internal pressure and external pressure is presented. Given the existence of shear stress in the conical shell due to thickness change along the axial direction, the governing equations are obtained based on first-order shear deformation theory (FSDT). These equations are solved by using multi-layer method (MLM). The model has been verified with the results of finite element method (FEM). Finally, some numerical results are presented to study the effects of thermal and mechanical loading, geometry parameters of truncated conical shell. تفاصيل المقالة -
حرية الوصول المقاله
98 - A New Numerical Procedure for Determination of Effective Elastic Constants in Unidirectional Composite Plates
S Daryazadeh L Lvov Gennadiy M TajdariIn this paper a composite plate with similar unidirectional fibers is considered. Assuming orthotropic structure, theory of elasticity is used for investigating the stress concentration. Also, complex variable functions are utilized for solving the plane stress problems أکثرIn this paper a composite plate with similar unidirectional fibers is considered. Assuming orthotropic structure, theory of elasticity is used for investigating the stress concentration. Also, complex variable functions are utilized for solving the plane stress problems. Then the effective characteristicsof this plate are studied numerically by using ANSYS software. In this research a volume element of fibers in square array is considered. In order to investigate the numerical finite element modeling, the modeling of a quarter unit cell is considered. For determining the elasticity coefficients, stress analysis is performed for considered volume with noting to boundary conditions. Effective elasticity and mechanical properties of composite which polymer epoxy is considered as its matrix, are determined theoretically and also by the proposed method in this paper with finite element method. Finally, the variations of mechanical properties with respect to fiber-volume fraction are studied. تفاصيل المقالة -
حرية الوصول المقاله
99 - The Attitude of Variation of Elastic Modules in Single Wall Carbon Nanotubes: Nonlinear Mass-Spring Model
A.R Golkarian M JabbarzadehThe examination of variation of elastic modules in single wall carbon nanotubes (SWCNTs) is the aim of this paper. Full nonlinear spring-like elements are employed to simulate specific atomic structures in the commercial code ABAQUS. Carbon atoms are attached to each no أکثرThe examination of variation of elastic modules in single wall carbon nanotubes (SWCNTs) is the aim of this paper. Full nonlinear spring-like elements are employed to simulate specific atomic structures in the commercial code ABAQUS. Carbon atoms are attached to each node as a mass point using atomic mass of carbon atoms. The influence of dimensions such as variation of length, diameter, aspect ratio and chirality is explored separately on the variations of young's and shear modules. It is observed that the effect of dimensions after a critical aspect ratio in nanotubes is negligible. Also, the influence of chirality on the elastic modules for same dimensions is observable. The results are compared with experimental results and theoretical data. تفاصيل المقالة -
حرية الوصول المقاله
100 - Creep Stress Redistribution Analysis of Thick-Walled FGM Spheres
S.M.A Aleayoub A LoghmanTime-dependent creep stress redistribution analysis of thick-walled FGM spheres subjected to an internal pressure and a uniform temperature field is investigated. The material creep and mechanical properties through the radial graded direction are assumed to obey the si أکثرTime-dependent creep stress redistribution analysis of thick-walled FGM spheres subjected to an internal pressure and a uniform temperature field is investigated. The material creep and mechanical properties through the radial graded direction are assumed to obey the simple power-law variation throughout the thickness. Total strains are assumed to be the sum of elastic, thermal and creep strains. Creep strains are time temperature and stress dependent. Using equations of equilibrium, compatibility and stress-strain relations a differential equation, containing creep strains, for radial stress is obtained. Ignoring creep strains in this differential equation, a closed form solution for initial thermo-elastic stresses at zero time is presented. Initial thermo-elastic stresses are illustrated for different material properties. Using Prandtl-Reuss relation in conjunction with the above differential equation and the Norton’s law for the material uni-axial creep constitutive model, radial and tangential creep stress rates are obtained. These creep stress rates are containing integrals of effective stress and are evaluated numerically. Creep stress rates are plotted against dimensionless radius for different material properties. Using creep stress rates, stress redistributions are calculated iteratively using thermo-elastic stresses as initial values for stress redistributions. It has been found that radial stress redistributions are not significant for different material properties. However, major redistributions occur for tangential and effective stresses. تفاصيل المقالة -
حرية الوصول المقاله
101 - Generalized Thermoelastic Problem of a Thick Circular Plate with Axisymmetric Heat Supply Due to Internal Heat Generation
J.J Tripathi G.D Kedar K.C DeshmukhA two dimensional generalized thermoelastic problem of a thick circular plate of finite thickness and infinite extent subjected to continuous axisymmetric heat supply and an internal heat generation is studied within the context of generalized thermoelasticity. Unified أکثرA two dimensional generalized thermoelastic problem of a thick circular plate of finite thickness and infinite extent subjected to continuous axisymmetric heat supply and an internal heat generation is studied within the context of generalized thermoelasticity. Unified system of equations for classical coupled thermoelasticity, Lord-Shulman and Green-Lindsay theory is considered. An exact solution of the problem is obtained in the transform domain. Inversion of Laplace transforms is done by employing numerical scheme. Mathematical model is prepared for Copper material plate and the numerical results are discussed and represented graphically. تفاصيل المقالة -
حرية الوصول المقاله
102 - Levy Type Solution for Nonlocal Thermo-Mechanical Vibration of Orthotropic Mono-Layer Graphene Sheet Embedded in an Elastic Medium
M Mohammadi A Farajpour M Goodarzi R HeydarshenasIn this paper, the effect of the temperature change on the vibration frequency of mono-layer graphene sheet embedded in an elastic medium is studied. Using the nonlocal elasticity theory, the governing equations are derived for single-layered graphene sheets. Using Levy أکثرIn this paper, the effect of the temperature change on the vibration frequency of mono-layer graphene sheet embedded in an elastic medium is studied. Using the nonlocal elasticity theory, the governing equations are derived for single-layered graphene sheets. Using Levy and Navier solutions, analytical frequency equations for single-layered graphene sheets are obtained. Using Levy solution, the frequency equation and mode shapes orthotropic rectangular nanoplate are considered for three cases of boundary conditions. The obtained results are subsequently compared with valid result reported in the literature. The effects of the small scale, temperature change, different boundary conditions, Winkler and Pasternak foundations, material properties and aspect ratios on natural frequencies are investigated. It has been shown that the non-dimensional frequency decreases with increasing temperature change. It is seen from the figure that the influence of nonlocal effect increases with decreasing of the length of nanoplate and also all results at higher length converge to the local frequency. The present analysis results can be used for the design of the next generation of nanodevices that make use of the thermal vibration proper ties of the nanoplates. تفاصيل المقالة -
حرية الوصول المقاله
103 - Small Scale Effect on the Vibration of Orthotropic Plates Embedded in an Elastic Medium and Under Biaxial In-plane Pre-load Via Nonlocal Elasticity Theory
M Mohammadi M Goodarzi M Ghayour S AlivandIn this study, the free vibration behavior of orthotropic rectangular graphene sheet embedded in an elastic medium under biaxial pre-load is studied. Using the nonlocal elasticity theory, the governing equation is derived for single-layered graphene sheets (SLGS). Diffe أکثرIn this study, the free vibration behavior of orthotropic rectangular graphene sheet embedded in an elastic medium under biaxial pre-load is studied. Using the nonlocal elasticity theory, the governing equation is derived for single-layered graphene sheets (SLGS). Differential quadrature method (DQM) has been used to solve the governing equations for various boundary conditions. To verify the accuracy of the present results, a Navier’s approach is also developed. DQM results are successfully verified with those of the Navier’s approach. The results are subsequently compared with valid result reported in the literature. The effects of the small scale, pre-load, Winkler and Pasternak foundations and material properties on natural frequencies are investigated. The results are shown that with the decrease of in-plane pre-loads the curves isotropic and orthotropic non-dimensional frequency in approaches close to each other. تفاصيل المقالة -
حرية الوصول المقاله
104 - An Exact Solution for Classic Coupled Thermoporoelasticity in Axisymmetric Cylinder
M Jabbari H DehbaniIn this paper, the classic coupled poro-thermoelasticity model of hollow and solid cylinders under radial symmetric loading condition is considered. A full analytical method is used and an exact unique solution of the classic coupled equations is presented. The thermal أکثرIn this paper, the classic coupled poro-thermoelasticity model of hollow and solid cylinders under radial symmetric loading condition is considered. A full analytical method is used and an exact unique solution of the classic coupled equations is presented. The thermal and pressure boundary conditions, the body force, the heat source and the injected volume rate per unit volume of a distribute water source are considered in the most general forms and no limiting assumption is used. This generality allows simulation of several of the applicable problems. تفاصيل المقالة -
حرية الوصول المقاله
105 - Magneto-Electro-Thermo-Mechanical Response of a Multiferroic Doubly-Curved Nano-Shell
S RazaviFree vibration of a simply-supported magneto-electro-elastic doubly-curved nano-shell is studied based on the first-order shear deformation theory in the presence of the rotary inertia effect. To model the electric and magnetic behaviors of the nano-shell, Gauss’s أکثرFree vibration of a simply-supported magneto-electro-elastic doubly-curved nano-shell is studied based on the first-order shear deformation theory in the presence of the rotary inertia effect. To model the electric and magnetic behaviors of the nano-shell, Gauss’s laws for electrostatics and magneto statics are used. By using Navier’s method, the partial differential equations of motion are reduced to a single ordinary differential equation. Then, an analytical relation is obtained for the natural frequency of magneto-electro-elastic doubly-curved nano-shell. Some examples are presented to validate the proposed model. Moreover, the effects of the electric and magnetic potentials, temperature rise, nonlocal parameter, parameters of Pasternak foundation, and the geometry of the nano-shell on the natural frequencies of magneto-electro-elastic doubly-curved nano-shells are investigated. It is found that natural frequency of magneto-electro-elastic doubly-curved nano-shell decreases with increasing the temperature, increasing the electric potential, or decreasing the magnetic potential. تفاصيل المقالة -
حرية الوصول المقاله
106 - Dynamic Stability of Functionally Graded Beams with Piezoelectric Layers Located on a Continuous Elastic Foundation
N Omidi M Karami Khorramabadi A NiknejadThis paper studies dynamic stability of functionally graded beams with piezoelectric layers subjected to periodic axial compressive load that is simply supported at both ends lies on a continuous elastic foundation. The Young’s modulus of beam is assumed to be gra أکثرThis paper studies dynamic stability of functionally graded beams with piezoelectric layers subjected to periodic axial compressive load that is simply supported at both ends lies on a continuous elastic foundation. The Young’s modulus of beam is assumed to be graded continuously across the beam thickness. Applying the Hamilton’s principle, the governing dynamic equation is established. The effects of the constituent volume fractions, the influences of applied voltage, foundation coefficient and piezoelectric thickness on the unstable regions are presented. تفاصيل المقالة -
حرية الوصول المقاله
107 - Semi Analytical Analysis of FGM Thick-Walled Cylindrical Pressure Vessel with Longitudinal Variation of Elastic Modulus under Internal Pressure
M Shariati H Sadeghi M Ghannad H GharooniIn this paper, a numerical analysis of stresses and displacements in FGM thick-walled cylindrical pressure vessel under internal pressure has been presented. The elastic modulus is assumed to be varying along the longitude of the pressure vessel with an exponential func أکثرIn this paper, a numerical analysis of stresses and displacements in FGM thick-walled cylindrical pressure vessel under internal pressure has been presented. The elastic modulus is assumed to be varying along the longitude of the pressure vessel with an exponential function continuously. The Poisson’s ratio is assumed to be constant. Whereas most of the previous studies about FGM thick-walled pressure vessels are on the basis of changing material properties along the radial direction, in this research, elastic analysis of cylindrical pressure vessel with exponential variations of elastic modulus along the longitudinal direction, under internal pressure, have been investigated. For the analysis of the vessel, the stiffness matrix of the cylindrical pressure vessel has been extracted by the usage of Galerkin Method and the numerical solution for axisymmetric cylindrical pressure vessel under internal pressure have been presented. Following that, displacements and stress distributions depending on inhomogeneity constant of FGM vessel along the longitudinal direction of elastic modulus, are illustrated and compared with those of the homogeneous case. The values which have been used in this study are arbitrary chosen to demonstrate the effect of inhomogeneity on displacements and stress distributions. Finally, the results are compared with the findings of finite element method (FEM). تفاصيل المقالة -
حرية الوصول المقاله
108 - Rheological Response and Validity of Viscoelastic Model Through Propagation of Harmonic Wave in Non-Homogeneous Viscoelastic Rods
R Kakar K KaurThis study is concerned to check the validity and applicability of a five parameter viscoelastic model for harmonic wave propagating in the non-homogeneous viscoelastic rods of varying density. The constitutive relation for five parameter model is first developed and va أکثرThis study is concerned to check the validity and applicability of a five parameter viscoelastic model for harmonic wave propagating in the non-homogeneous viscoelastic rods of varying density. The constitutive relation for five parameter model is first developed and validity of these relations is checked. The non-homogeneous viscoelastic rods are assumed to be initially unstressed and at rest. In this study, it is assumed that density, rigidity and viscosity of the specimen i.e. rod are space dependent. The method of non-linear partial differential equation (Eikonal equation) has been used for finding the dispersion equation of harmonic waves in the rods. A method for treating reflection at the free end of the finite non-homogeneous viscoelastic rod is also presented. All the cases taken in this study are discussed numerically and graphically with MATLAB. تفاصيل المقالة -
حرية الوصول المقاله
109 - An Exact Solution for Kelvin-Voigt Model Classic Coupled Thermo Viscoelasticity in Spherical Coordinates
S Bagheri M JabbariIn this paper, the classic Kelvin-Voigt model coupled thermo-viscoelasticity model of hollow and solid spheres under radial symmetric loading condition is considered. A full analytical method is used and an exact unique solution of the classic coupled equations is prese أکثرIn this paper, the classic Kelvin-Voigt model coupled thermo-viscoelasticity model of hollow and solid spheres under radial symmetric loading condition is considered. A full analytical method is used and an exact unique solution of the classic coupled equations is presented. The thermal and mechanical boundary conditions, the body force, and the heat source are considered in the most general forms and where no limiting assumption is used. This generality allows simulate varieties of applicable problems. At the end, numerical results are presented and compared with classic theory of thermoelasticity. تفاصيل المقالة -
حرية الوصول المقاله
110 - Stress Analysis of Skew Nanocomposite Plates Based on 3D Elasticity Theory Using Differential Quadrature Method
M.R Nami M JanghorbanIn this paper, a three dimensional analysis of arbitrary straight-sided quadrilateral nanocomposite plates are investigated. The governing equations are based on three-dimensional elasticity theory which can be used for both thin and thick nanocomposite plates. Although أکثرIn this paper, a three dimensional analysis of arbitrary straight-sided quadrilateral nanocomposite plates are investigated. The governing equations are based on three-dimensional elasticity theory which can be used for both thin and thick nanocomposite plates. Although the equations can support all the arbitrary straight-sided quadrilateral plates but as a special case, the numerical results for skew nanocomposite plates are investigated. The differential quadrature method (DQM) is used to solve these equations. In order to show the accuracy of present work, our results are compared with other numerical solution for skew plates. From the knowledge of author, it is the first time that the stress analysis of arbitrary straight-sided quadrilateral nanocomposite plates is investigated. It is shown that increasing the skew angle and thickness of nanocomposite skew plate will decrease the vertical displacements. It is also noted that the thermal effects are also added in the governing equations. تفاصيل المقالة -
حرية الوصول المقاله
111 - Frequency Analysis of FG Sandwich Rectangular Plates with a Four-Parameter Power-Law Distribution
S Kamarian M.H Yas A PourasgharAn accurate solution procedure based on the three-dimensional elasticity theory for the free vibration analysis of Functionally Graded Sandwich (FGS) plates is presented. Since no assumptions on stresses and displacements have been employed, it can be applied to the fre أکثرAn accurate solution procedure based on the three-dimensional elasticity theory for the free vibration analysis of Functionally Graded Sandwich (FGS) plates is presented. Since no assumptions on stresses and displacements have been employed, it can be applied to the free vibration analysis of plates with arbitrary thickness. The two-constituent FGS plate consists of ceramic and metal graded through the thickness, from one surface of the each sheet to the other according to a generalized power-law distribution with four parameters. The benefit of using generalized power-law distribution is to illustrate and present useful results arising from symmetric, asymmetric and classic profiles. Using the Generalized Differential Quadrature (GDQ) method through the thickness of the plate, further allows one to deal with FG plates with an arbitrary thickness distribution of material properties. The fast rate of convergence and accuracy of the method are investigated through the different solved examples. The effects of different geometrical parameters such as the thickness-to-length ratio, different profiles of materials volume fraction and four parameters of power-law distribution on the vibration characteristics of the FGS plates are investigated. Interesting result shows that by utilizing a suitable four-parameter model for materials volume fraction, frequency parameter can be obtained more than the frequency parameter of the similar FGS plate with sheets made of 100% ceramic and at the same time lighter. Also, results show that frequencies of symmetric and classic profiles are smaller and larger than that of other types of FGS plates respectively. The solution can be used as benchmark for other numerical methods and also the refined plate theories. تفاصيل المقالة -
حرية الوصول المقاله
112 - Magneto-Thermo-Elastic Stresses and Perturbation of the Magnetic Field Vector in an EGM Rotating Disk
A Ghorbanpour Arani M Azamia H SepianiIn this article, the magneto-thermo-elastic problem of exponentially graded material (EGM) hollow rotating disk placed in uniform magnetic and temperature fields is considered. Exact solutions for stresses and perturbations of the magnetic field vector in EGM hollow rot أکثرIn this article, the magneto-thermo-elastic problem of exponentially graded material (EGM) hollow rotating disk placed in uniform magnetic and temperature fields is considered. Exact solutions for stresses and perturbations of the magnetic field vector in EGM hollow rotating disk are determined using the infinitesimal theory of magneto-thermo-elasticity under plane stress. The material properties, except Poisson’s ratio, are assumed to depend on variable of the radius and they are expressed as exponential functions of radius. The direct method is used to solve the heat conduction and Hyper-geometric functions are employed to solve Navier equation. The temperature, displacement, and stress fields and the perturbation of the magnetic field vector are determined and compared with those of the homogeneous case. Hence, the effect of in-homogeneity on the stresses and the perturbation of magnetic field vector distribution are demonstrated. The results of this study are applicable for designing optimum EGM hollow rotating disk. تفاصيل المقالة -
حرية الوصول المقاله
113 - Consolidation Around a Heat Source in an Isotropic Fully Saturated Rock with Porous Structure in Quasi-Static State
N Das Gupta N.C DasThe titled problem of coupled thermoelasticity for porous structure has been solved with an instantaneous heat source acting on a plane area in an unbounded medium. The basic equations of thermoelasticity, after being converted into a one-dimensional form, have been wri أکثرThe titled problem of coupled thermoelasticity for porous structure has been solved with an instantaneous heat source acting on a plane area in an unbounded medium. The basic equations of thermoelasticity, after being converted into a one-dimensional form, have been written in the form of a vector-matrix differential equation and solved by the eigenvalue approach for the field variables in the Laplace transform domain in closed form. The deformation, temperature and pore pressure have been determined for the space time domain by numerical inversion from the Laplace transform domain. Finally the results are analyzed by depicting several graphs for the field variables. تفاصيل المقالة -
حرية الوصول المقاله
114 - A Power Series Solution for Free Vibration of Variable Thickness Mindlin Circular Plates with Two-Directional Material Heterogeneity and Elastic Foundations
M.M Alipour M ShariyatIn the present paper, a semi-analytical solution is presented for free vibration analysis of circular plates with complex combinations of the geometric parameters, edge-conditions, material heterogeneity, and elastic foundation coefficients. The presented solution cover أکثرIn the present paper, a semi-analytical solution is presented for free vibration analysis of circular plates with complex combinations of the geometric parameters, edge-conditions, material heterogeneity, and elastic foundation coefficients. The presented solution covers many engineering applications. The plate is assumed to have a variable thickness and made of a heterogeneous material whose properties vary in both radial and transverse directions. While the edge is simply-supported, clamped, or free; the bottom surface of the plate is resting on a two-parameter (Winkler-Pasternak) elastic foundation. A comprehensive sensitivity analysis including evaluating effects of various parameters is carries out. Mindlin theory is employed for derivation of the governing equations whereas the differential transform method is used to solve the resulted equations. In this regard, both the in-plane and rotary inertia are considered. Results show that degradations caused by a group of the factors (e.g., the geometric parameters) in the global behavior of the structure may be compensated by another group of factors of different nature (e.g, the material heterogeneity parameters). Moreover, employing the elastic foundation leads to higher natural frequencies and postponing the resonances. تفاصيل المقالة -
حرية الوصول المقاله
115 - Effect of Boundary Condition on Pre-Existing Crack Under Fatigue Loading
V.K Singh P.C Gope R.K BhagatIn this paper, the present investigation has been conducted keeping in mind some of the problems concerning the crack propagation direction and growth under constant loading in an inclined crack geometry. The present studies mainly focused on the development and modific أکثرIn this paper, the present investigation has been conducted keeping in mind some of the problems concerning the crack propagation direction and growth under constant loading in an inclined crack geometry. The present studies mainly focused on the development and modifications in the crack growth criterion to account the biaxial, shear loading and number of stress terms. Existing criteria for the prediction of crack initiation direction have been modified taking higher order stress terms. The effective methods of experimentally determining the stress intensity factor for a body containing a crack is to analyze the isochromatic pattern obtained from a photoelastic model. The effect of biaxial load factor, crack angle, Crack length/width of specimen and length of specimen/width of specimen were studied and a regression model was developed for geometry correction to predict stress intensity factor for tearing mode and intensity factor for shearing mode. This approach is being used to predict crack growth trajectory under biaxial cyclic loading by assuming that the crack may grow in a number of discrete steps using the vectorial method. MTS criterion (Maximum Tangential Stress criterion) is used for prediction of crack initiating angle. The crack growth trajectory has been determined by cycle simulation procedure. تفاصيل المقالة -
حرية الوصول المقاله
116 - Wave Propagation in Mixture of Generalized Thermoelastic Solids Half-Space
R Kumar S DeviThis paper concentrates on the reflection of plane waves in the mixture of generalized thermo elastic solid half-space. There exists quasi dilatational waves i.e. qP1, qP2, qT and two rotational waves S1, S2 in a two dimensional model of the solid. The boundary conditio أکثرThis paper concentrates on the reflection of plane waves in the mixture of generalized thermo elastic solid half-space. There exists quasi dilatational waves i.e. qP1, qP2, qT and two rotational waves S1, S2 in a two dimensional model of the solid. The boundary conditions are solved to obtain a system of five non-homogeneous equations for amplitude ratios. These amplitude ratios are found to depend on the angle of incidence of incident wave, mixture and thermal parameters and have been computed numerically and presented graphically. The appreciable effects of mixtures and thermal on the amplitude ratios are obtained. تفاصيل المقالة -
حرية الوصول المقاله
117 - Propagation of Waves at an Interface of Heat Conducting Elastic Solid and Micropolar Fluid Media
R Kumar M Kaur S.C RajvanshiThe present investigation is concerned with the reflection and transmission coefficients of plane waves at the interface of generalized thermoelastic solid half space and heat conducting micropolar fluid half- space. The amplitude ratios of various reflected and transmi أکثرThe present investigation is concerned with the reflection and transmission coefficients of plane waves at the interface of generalized thermoelastic solid half space and heat conducting micropolar fluid half- space. The amplitude ratios of various reflected and transmitted waves with various angle of incidence have been computed numerically and depicted graphically. Micropolarity and thermal relaxation effects are shown on the amplitude ratios for specific model. Some special and particular cases are also deduced from the present investigation. تفاصيل المقالة -
حرية الوصول المقاله
118 - An Exact Solution for Lord-Shulman Generalized Coupled Thermoporoelasticity in Spherical Coordinates
M Jabbari H DehbaniIn this paper, the generalized coupled thermoporoelasticity model of hollow and solid spheres under radial symmetric loading condition (r, t) is considered. A full analytical method is used and an exact unique solution of the generalized coupled equations is presented. أکثرIn this paper, the generalized coupled thermoporoelasticity model of hollow and solid spheres under radial symmetric loading condition (r, t) is considered. A full analytical method is used and an exact unique solution of the generalized coupled equations is presented. The thermal, mechanical and pressure boundary conditions, the body force, the heat source and the injected volume rate per unit volume of a distribute water source are considered in the most general forms and where no limiting assumption is used. This generality allows simulate varieties of applicable problems. At the end, numerical results are presented and compared with classic theory of thermoporoelasticity. تفاصيل المقالة -
حرية الوصول المقاله
119 - Torsional Stability of Cylindrical Shells with Functionally Graded Middle Layer on the Winkler Elastic Foundation
A.H Sofiyev S AdiguzelIn this study, the torsional stability analysis is presented for thin cylindrical with the functionally graded (FG) middle layer resting on the Winker elastic foundation. The mechanical properties of functionally graded material (FGM) are assumed to be graded in the thi أکثرIn this study, the torsional stability analysis is presented for thin cylindrical with the functionally graded (FG) middle layer resting on the Winker elastic foundation. The mechanical properties of functionally graded material (FGM) are assumed to be graded in the thickness direction according to a simple power law and exponential distributions in terms of volume fractions of the constituents. The fundamental relations and basic equations of three-layered cylindrical shells with a FG middle layer resting on the Winker elastic foundation under torsional load are derived. Governing equations are solved by using the Galerkin method. The numerical results reveal that variations of the shell thickness-to-FG layer thickness ratio, radius-to-shell thickness ratio, lengths-to-radius ratio, foundation stiffness and compositional profiles have significant effects on the critical torsional load of three-layered cylindrical shells with a FG middle layer. The results are verified by comparing the obtained values with those in the existing literature. تفاصيل المقالة -
حرية الوصول المقاله
120 - Wave Propagation in Fibre-Reinforced Transversely Isotropic Thermoelastic Media with Initial Stress at the Boundary Surface
R Kumar S.K Garg S AhujaThe reflection and transmission of thermoelastic plane waves at an imperfect boundary of two dissimilar fibre-reinforced transversely isotropic thermoelastic solid half-spaces under hydrostatic initial stress has been investigated. The appropriate boundary conditions ar أکثرThe reflection and transmission of thermoelastic plane waves at an imperfect boundary of two dissimilar fibre-reinforced transversely isotropic thermoelastic solid half-spaces under hydrostatic initial stress has been investigated. The appropriate boundary conditions are applied at the interface to obtain the reflection and transmission coefficients of various reflected and transmitted waves with incidence of quasi-longitudinal (qP), quasi-thermal (qT) & quasi- transverse (qSV) waves respectively at an imperfect boundary and deduced for normal stiffness, transverse stiffness, thermal contact conductance and welded boundaries.The reflection and transmission coefficients are functions of frequency, initial stress and angle of incidence. There amplitude ratios are computed numerically and depicted graphically for a specific model to show the effect of initial stress. Some special cases are also deduced from the present investigation. تفاصيل المقالة -
حرية الوصول المقاله
121 - Wave Propagation at an Interface of Elastic and Microstretch Thermoelastic Solids with Microtemperatures
R Kumar M Kaur S.C RajvanshiIn the present paper, the problem of reflection and transmission of waves at an interface of elastic and microstretch thermoelastic solids with microtemperatureshas been studied. The amplitude ratios of various reflected and transmitted waves are functions of angle of i أکثرIn the present paper, the problem of reflection and transmission of waves at an interface of elastic and microstretch thermoelastic solids with microtemperatureshas been studied. The amplitude ratios of various reflected and transmitted waves are functions of angle of incidence and frequency of incident wave. The expressions of amplitude ratios have been computed numerically for a particular model. The variations of amplitude ratios with angle of incidence are shown graphically to depict the effect of microrotation. Some particular cases of interest have been also deduced. تفاصيل المقالة -
حرية الوصول المقاله
122 - Reflection of Waves in a Rotating Transversely Isotropic Thermoelastic Half-space Under Initial Stress
R.R Gupta R.R. GuptaThe present paper concerns with the effect of initial stress on the propagation of plane waves in a rotating transversely isotropic medium in the context of thermoelasticity theory of GN theory of type-II and III. After solving the governing equations, three waves propa أکثرThe present paper concerns with the effect of initial stress on the propagation of plane waves in a rotating transversely isotropic medium in the context of thermoelasticity theory of GN theory of type-II and III. After solving the governing equations, three waves propagating in the medium are obtained. The fastest among them is a quasi-longitudinal wave. The slowest of them is a thermal wave. The remaining is called quasi-transverse wave. The prefix ‘quasi’ refers to their polarizations being nearly, but not exactly, parallel or perpendicular to the direction of propagation. The polarizations of these three waves are not mutually orthogonal. After imposing the appropriate boundary conditions, the amplitudes of reflection coefficients have been obtained. Numerically, simulated results have been plotted graphically with respect to frequency to evince the effect of initial stress and anisotropy. تفاصيل المقالة -
حرية الوصول المقاله
123 - Nonlocal Vibration of Y-SWCNT Conveying Fluid Considering a General Nonlocal Elastic Medium
A.H Ghobanpour Arani A Rastgoo A Ghorbanpour Arani M. Sh. ZareiIn this paper, a nonlocal foundation model is proposed to analyze the vibration and instability of a Y-shaped single-walled carbon nanotube (Y-SWCNT) conveying fluid. In order to achieve more accurate results, fourth order beam theory is utilized to obtain strain-displa أکثرIn this paper, a nonlocal foundation model is proposed to analyze the vibration and instability of a Y-shaped single-walled carbon nanotube (Y-SWCNT) conveying fluid. In order to achieve more accurate results, fourth order beam theory is utilized to obtain strain-displacement relations. For the first time, a nonlocal model is presented based on nonlocal elasticity and the effects of nonlocal forces from adjacent and non-adjacent elements on deflection are considered. The Eringen’s theory is utilized due to its capability to consider the size effect. Based on Hamilton’s principle, motion equations as well as boundary conditions are derived and solved by means of hybrid analytical-numerical method. It is believed that the presented general foundation model offers an exact and effective new approach to investigate vibration characteristics of this kind of structures embedded in an elastic medium. The results of this investigation may provide a useful reference in controlling systems in nano-scale. تفاصيل المقالة -
حرية الوصول المقاله
124 - Photoelastic Determination of Mixed Mode Stress Intensity Factors
V.K Singh P.C GopeA two dimensional finite model with inclined crack at different crack angles are being analyzed in mixed mode condition using photo elasticity method for the determination of Stress Intensity Factors. The well-known Sih’s equation and three points deterministic ap أکثرA two dimensional finite model with inclined crack at different crack angles are being analyzed in mixed mode condition using photo elasticity method for the determination of Stress Intensity Factors. The well-known Sih’s equation and three points deterministic approach is used for the determination of stress intensity factors. The effects of biaxial load factor, crack angle, size factors were studied and a regression model was developed for geometry correction to predict Stress Intensity Factors. The results give a good compromise to the theoretical one. The experimental result also gives significant data for the two dimensional mixed mode loading conditions. تفاصيل المقالة -
حرية الوصول المقاله
125 - Axial and Transverse Vibration of SWBNNT System Coupled Pasternak Foundation Under a Moving Nanoparticle Using Timoshenko Beam Theory
A Ghorbanpour Arani A Karamali Ravandi M.A Roudbari M.B Azizkhani A Hafizi BidgoliIn this study, a semi analytical method for transverse and axial vibration of single-walled boron nitride nanotube (SWBNNT) under moving a nanoparticle is presented. The surrounding elastic medium as Pasternak foundation and surface stress effect are included in the for أکثرIn this study, a semi analytical method for transverse and axial vibration of single-walled boron nitride nanotube (SWBNNT) under moving a nanoparticle is presented. The surrounding elastic medium as Pasternak foundation and surface stress effect are included in the formulations of the proposed model. Using Timoshenko beam theory (TBT), Hamilton’s principle and nonlocal piezoelasticity theory, the higher order governing equation is derived. The influences of surface stress effects, spring and shear parameters of Pasternak foundation and aspect ratio are also investigated on the free and forced vibration behavior of SWBNNT under moving a nanoparticle. Through an inclusive parametric study, the importance of using surrounding elastic medium in decrease of normalized dynamic deflection is proposed. It is demonstrated that the values of shear modulus have significant role on the vibration behavior of SWBNNT. The influences of surface stresses on the amplitude of normalized dynamic deflection are also discussed. The output result's of this study has significant influences in design and production of micro electro mechanical system (MEMS) and nano electro mechanical system (NEMS) for advanced applications. تفاصيل المقالة -
حرية الوصول المقاله
126 - Reflection and Transmission of Longitudinal Wave at Micropolar Viscoelastic Solid/Fluid Saturated Incompressible Porous Solid Interface
N KumariIn this paper, the reflection and refraction of longitudinal wave from a plane surface separating a micropolar viscoelastic solid half space and a fluid saturated incompressible half space is studied. A longitudinal wave (P-wave) impinges obliquely at the interface. Amp أکثرIn this paper, the reflection and refraction of longitudinal wave from a plane surface separating a micropolar viscoelastic solid half space and a fluid saturated incompressible half space is studied. A longitudinal wave (P-wave) impinges obliquely at the interface. Amplitude ratios for various reflected and transmitted waves have been obtained. Then these amplitude ratios have been computed numerically for a specific model and results thus obtained are shown graphically with angle of incidence of incident wave. It is found that these amplitude ratios depend on angle of incidence of the incident wave as well as on the properties of media. A particular case when longitudinal wave reflects at free surface of micropolar viscoelastic solid has been deduced and discussed. From the present investigation, a special case when fluid saturated porous half space reduces to empty porous solid has also been deduced and discussed with the help of graphs. تفاصيل المقالة -
حرية الوصول المقاله
127 - Exact Solution for Electrothermoelastic Behaviors of a Radially Polarized FGPM Rotating Disk
A Ghorbanpour Arani A Jafarzadeh Jazi M Abdollahian M.R Mozdianfard M Mohammadimehr S AmirThis article presents an exact solution for an axisymmetric functionally graded piezoelectric (FGP) rotating disk with constant thickness subjected to an electric field and thermal gradient. All mechanical, thermal and piezoelectric properties except for Poisson’s أکثرThis article presents an exact solution for an axisymmetric functionally graded piezoelectric (FGP) rotating disk with constant thickness subjected to an electric field and thermal gradient. All mechanical, thermal and piezoelectric properties except for Poisson’s ratio are taken in the form of power functions in radial direction. After solving the heat transfer equation, first a symmetric distribution of temperature is produced. The gradient of displacement in axial direction is then obtained by assuming stress equation in axial direction to be zero. The electric potential gradient is attained by charge and electric displacement equations. Substituting these terms in the equations for the dimensionless stresses in the radial and circumferential directions yield these stresses and using them in the mechanical equilibrium equation a nonhomogeneous second order differential equation is produced that by solving it, the dimensionless displacement in radial direction can be achieved. The study results for a FGP rotating hollow disk are presented graphically in the form of distributions for displacement, stresses and electrical potential. تفاصيل المقالة -
حرية الوصول المقاله
128 - Damping Ratio in Micro-Beam Resonators Based on Magneto-Thermo-Elasticity
A Khanchehgardan G Rezazadeh A AmiriThis paper investigates damping ratio in micro-beam resonators based on magneto-thermo-elasticity. A unique aspect of the present study is the effect of permanent magnetic field on the stiffness and thermo-elastic damping of the micro resonators. In our modeling the the أکثرThis paper investigates damping ratio in micro-beam resonators based on magneto-thermo-elasticity. A unique aspect of the present study is the effect of permanent magnetic field on the stiffness and thermo-elastic damping of the micro resonators. In our modeling the theory of thermo-elasticity with interacting of an externally applied permanent magnetic field is taken into account. Combined theoretical and numerical studies investigate the permanent magnetic field effect on the damping ratio in clamped-clamped and cantilever micro-beams. Furthermore, the influence of the magnetic field intensity on the frequency of the micro-beams with thermo-elastic damping effect is evaluated. Such evaluations are used to determine the influence of magnetic field on the vibration amplitude of the resonators. The meaningful conclusion is that the magnetic field increases the equivalent stiffness and thermo-elastic damping and consequently the energy consumption of the resonators. تفاصيل المقالة -
حرية الوصول المقاله
129 - Effect of Magnetic Field on Torsional Waves in Non-Homogeneous Aeolotropic Tube
R Kakar S Kakar K.C Gupta K KaurThe effect of magnetic field on torsional waves propagating in non-homogeneous viscoelastic cylindrically aeolotropic material is discussed. The elastic constants and non-homogeneity in viscoelastic medium in terms of density and elastic constant is taken. The frequency أکثرThe effect of magnetic field on torsional waves propagating in non-homogeneous viscoelastic cylindrically aeolotropic material is discussed. The elastic constants and non-homogeneity in viscoelastic medium in terms of density and elastic constant is taken. The frequency equations have been derived in the form of a determinant involving Bessel functions. Dispersion equation in each case has been derived and the graphs have been plotted showing the effect of variation of elastic constants and the presence of magnetic field. The obtained dispersion equations are in agreement with the classical result. The numerical calculations have been presented graphically by using MATLAB. تفاصيل المقالة -
حرية الوصول المقاله
130 - Effect of Magnetic Field and a Mode-I Crack 3D-Problem in Micropolar Thermoelastic Cubic Medium Possessing Under Three Theories
Kh Lotfy Y YahiaA model of the equations of two dimensional problems in a half space, whose surface in free of micropolar thermoelastic medium possesses cubic symmetry as a result of a Mode-I Crack is studied. There acts an initial magnetic field parallel to the plane boundary of the h أکثرA model of the equations of two dimensional problems in a half space, whose surface in free of micropolar thermoelastic medium possesses cubic symmetry as a result of a Mode-I Crack is studied. There acts an initial magnetic field parallel to the plane boundary of the half- space. The crack is subjected to prescribed temperature and stress distribution. The formulation in the context of the Lord-Şhulman theory LS includes one relaxation time and Green-Lindsay theory GL with two relaxation times, as well as the classical dynamical coupled theory CD. The normal mode analysis is used to obtain the exact expressions for the displacement, microrotation, stresses and temperature distribution. The variations of the considered variables with the horizontal distance are illustrated graphically. Comparisons are made with the results in the presence of magnetic field. A comparison is also made between the three theories for different depths. تفاصيل المقالة -
حرية الوصول المقاله
131 - Rayleigh Waves in a Homogeneous Magneto-Thermo Voigt-Type Viscoelastic Half-Space under Initial Surface Stresses
R KakarThis paper deals with the propagation of magneto-thermo Rayleigh waves in a homogeneous viscoelastic half-space under initial stress. It has been observed that velocity of Rayleigh waves depends on viscosity, magnetic field, temperature and initial stress of the half-sp أکثرThis paper deals with the propagation of magneto-thermo Rayleigh waves in a homogeneous viscoelastic half-space under initial stress. It has been observed that velocity of Rayleigh waves depends on viscosity, magnetic field, temperature and initial stress of the half-space. The frequency equation for Rayleigh waves under the effect of magnetic field, stress and temperature for both viscoelastic and elastic medium is first obtained by using classical theory of thermoelasticity and then computed numerically. The variation of phase velocity of Rayleigh waves with respect to initial hydrostatic stress in viscoelastic and elastic half-space is shown graphically. In the absence of various parameters of the medium, the obtained results are in agreement with classical results given by Caloi and Lockett. تفاصيل المقالة -
حرية الوصول المقاله
132 - The Effect of Elastic Foundations on the Buckling Behavior of Functionally Graded Carbon Nanotube-Reinforced Composite Plates in Thermal Environments Using a Meshfree Method
Sh Shams B Soltani M Memar ArdestaniThe buckling behavior of functionally graded carbon nanotube-reinforced composite (FG-CNTRC) plates resting on Winkler-Pasternak elastic foundations under in-plane loads for various temperatures is investigated using element-free Galerkin (EFG) method based on first-ord أکثرThe buckling behavior of functionally graded carbon nanotube-reinforced composite (FG-CNTRC) plates resting on Winkler-Pasternak elastic foundations under in-plane loads for various temperatures is investigated using element-free Galerkin (EFG) method based on first-order shear deformation theory (FSDT). The modified shear correction factor is used based on energy equivalence principle. Carbon nanotubes (CNTs) are embedded in polymer matrix and distributed in four types of arrangements. The temperature-dependent material properties of an FG-CNTRC plate are assumed to be graded along the thickness direction of the plate and estimated through a micromechanical model based on the extended rule of mixture. Full transformation approach is employed to enforce essential boundary conditions. The modified shear correction factor is utilized based on energy equivalence principle involving the actual non-uniform shear stress distribution through the thickness of the FG-CNTRC plate. The accuracy and convergency of the EFG method is established by comparing the obtained results with available literature. Moreover, the effects of elastic foundation parameters are investigated for various boundary conditions, temperatures, plate width-to-thickness and aspect ratios, and CNT distributions and volume fractions. Detailed parametric studies demonstrate that the elastic foundation parameters, CNT distributions along the thickness direction of the plate and the temperature change have noticeable effects on buckling behavior of carbon nanotube-reinforced composite (CNTRC) plates. تفاصيل المقالة -
حرية الوصول المقاله
133 - Free Vibration Analysis of Micropolar Thermoelastic Cylindrical Curved Plate in Circumferential Direction
G Partap R KumarThe free vibration analysis ofhomogeneous isotropic micropolar thermoelastic cylindrical curved plate in circumferential direction has been investigated in the context of generalized themoelasticity III, recently developed by Green and Naghdi. The model has been simplif أکثرThe free vibration analysis ofhomogeneous isotropic micropolar thermoelastic cylindrical curved plate in circumferential direction has been investigated in the context of generalized themoelasticity III, recently developed by Green and Naghdi. The model has been simplified using Helmholtz decomposition technique and the resulting equations have been solved using separation of variable method. Mathematical modeling of the problem to obtain dispersion curves for curved isotropic plate leads to coupled differential equations and solutions are obtained by using Bessel functions. The frequency equations connecting the frequency with circumferential wave number and other physical parameters are derived for stress free cylindrical plate. In order to illustrate theoretical development, numerical solutions are obtained and presented graphically for a magnesium crystal. تفاصيل المقالة -
حرية الوصول المقاله
134 - Mathematical Modeling for Thermoelastic Double Porous Micro-Beam Resonators
R Kumar R Vohra M.G GorlaIn the present work, the mathematical model of a homogeneous, isotropic thermoelastic double porous micro-beam, based on the Euler-Bernoulli theory is developed in the context of Lord-Shulman [1] theory of thermoelasticity. Laplace transform technique has been used to o أکثرIn the present work, the mathematical model of a homogeneous, isotropic thermoelastic double porous micro-beam, based on the Euler-Bernoulli theory is developed in the context of Lord-Shulman [1] theory of thermoelasticity. Laplace transform technique has been used to obtain the expressions for lateral deflection, axial stress, axial displacement, volume fraction field and temperature distribution. A numerical inversion technique has been applied to recover the resulting quantities in the physical domain. Variations of axial displacement, axial stress, lateral deflection, volume fraction field and temperature distribution with axial distance are depicted graphically to show the effects of porosity and thermal relaxation time. Some particular cases are also deduced. تفاصيل المقالة -
حرية الوصول المقاله
135 - A New Finite Element Formulation for Buckling and Free Vibration Analysis of Timoshenko Beams on Variable Elastic Foundation
A Mirzabeigy M Haghpanahi R MadoliatIn this study, the buckling and free vibration of Timoshenko beams resting on variable elastic foundation analyzed by means of a new finite element formulation. The Winkler model has been applied for elastic foundation. A two-node element with four degrees of freedom is أکثرIn this study, the buckling and free vibration of Timoshenko beams resting on variable elastic foundation analyzed by means of a new finite element formulation. The Winkler model has been applied for elastic foundation. A two-node element with four degrees of freedom is suggested for finite element formulation. Displacement and rotational fields are approximated by cubic and quadratic polynomial interpolation functions, respectively. The length of the element is assumed to be so small, so that linear variation could be considered for elastic foundation through the length of the element. By these assumptions and using energy method, stiffness matrix, mass matrix and geometric stiffness matrix of the proposed beam element are obtained and applied to buckling and free vibration analysis. Accuracy of obtained formulation is approved by comparison with the special cases of present problem in other studies. Present formulation shows faster convergence in comparison with conventional finite element formulation. The effects of different parameters on the stability and free vibration of Timoshenko beams investigated and results are completely new. تفاصيل المقالة -
حرية الوصول المقاله
136 - On the Dynamic Characteristic of Thermoelastic Waves in Thermoelastic Plates with Thermal Relaxation Times
K.L VermaIn this paper, analysis for the propagation of general anisotropic media of finite thickness with two thermal relaxation times is studied. Expression of displacements, temperature, thermal stresses, and thermal gradient for most general anisotropic thermoelastic plates أکثرIn this paper, analysis for the propagation of general anisotropic media of finite thickness with two thermal relaxation times is studied. Expression of displacements, temperature, thermal stresses, and thermal gradient for most general anisotropic thermoelastic plates of finite thickness are obtained in the analysis. The calculation is then carried forward for slightly more specialized case of a monoclinic plate. Dispersion relations for symmetric and antisymmetric wave modes are obtained. Thermoelastic plates of higher symmetry are contained implicitly in the analysis. Numerical solution of the frequency equation for a representative plate of assigned thickness is carried out, and the dispersion curves for the few lower modes are presented. Coupled thermoelastic thermal motions of the medium are found dispersive and coupled with each other due to the thermal and anisotropic effects. Some special cases have also been deduced and discussed. تفاصيل المقالة -
حرية الوصول المقاله
137 - In-Plane and out of Plane Free Vibration of U-Shaped AFM Probes Based on the Nonlocal Elasticity
M Ghadiri S.A.H Hosseini M Karami M NamvarAtomic force microscope (AFM) has been developed at first for topography imaging; in addition, it is used for characterization of mechanical properties. Most researches have been primarily focused on rectangular single-beam probes to make vibration models simple. Recent أکثرAtomic force microscope (AFM) has been developed at first for topography imaging; in addition, it is used for characterization of mechanical properties. Most researches have been primarily focused on rectangular single-beam probes to make vibration models simple. Recently, the U-shaped AFM probe is employed to determine sample elastic properties and has been developed to heat samples locally. In this study, a simplified analytical model of these U-shaped AFM is described and three beams have been used for modelling this probe. This model contains two beams are clamped at one end and connected with a perpendicular cross beam at the other end. The beams are supposed only in bending flexure and twisting, but their coupling allows a wide variety of possible dynamic behaviors. In the present research, the natural frequency and sensitivity of flexural and torsional vibration for AFM probes have been analyzed considering influence of scale effect. For this purpose, governing equations of dynamic behavior of U-shaped AFM probe are extracted based on Eringen's theory using Euler–Bernoulli beam theory and an analytical method is employed to solve these equations. The results in this paper have been extracted for different values of nonlocal parameters; it is shown that for a special case, there is a good agreement between reported results in available references and our results. The obtained results show that the frequencies of U-shaped AFM decrease with increasing the nonlocal parameter. تفاصيل المقالة -
حرية الوصول المقاله
138 - Buckling Analysis of a Double-Walled Carbon Nanotube Embedded in an Elastic Medium Using the Energy Method
A Ghorbanpour Arani M Shokravi M MohammadimehrThe axially compressed buckling of a double-walled carbon nanotabe surrounded by an elastic medium using the energy and the Rayleigh-Ritz methods is investigated in this paper. In this research, based on the elastic shell models at nano scale, the effects of the van der أکثرThe axially compressed buckling of a double-walled carbon nanotabe surrounded by an elastic medium using the energy and the Rayleigh-Ritz methods is investigated in this paper. In this research, based on the elastic shell models at nano scale, the effects of the van der Waals forces between the inner and the outer tubes, the small scale and the surrounding elastic medium on the critical buckling load are considered. Normal stresses at the outer tube medium interface are also included in the current analysis. An expression is derived relating the external pressure to the buckling mode number, from which the critical pressure can be obtained. It is seen from the results that the critical pressure is dependent on the outer radius to thickness ratio, the material parameters of the surrounding elastic medium such as Young’s modulus and Poisson’s ratio. Moreover, it is shown that the critical pressure descend very quickly with increasing the half axial wave numbers. تفاصيل المقالة -
حرية الوصول المقاله
139 - Surface Effects on Free Vibration Analysis of Nanobeams Using Nonlocal Elasticity: A Comparison Between Euler-Bernoulli and Timoshenko
Sh Hosseini – Hashemi M Fakher R NazemnezhadIn this paper, surface effects including surface elasticity, surface stress and surface density, on the free vibration analysis of Euler-Bernoulli and Timoshenko nanobeams are considered using nonlocal elasticity theory. To this end, the balance conditions between nanob أکثرIn this paper, surface effects including surface elasticity, surface stress and surface density, on the free vibration analysis of Euler-Bernoulli and Timoshenko nanobeams are considered using nonlocal elasticity theory. To this end, the balance conditions between nanobeam bulk and its surfaces are considered to be satisfied assuming a linear variation for the component of the normal stress through the nanobeam thickness. The governing equations are obtained and solved for Silicon and Aluminum nanobeams with three different boundary conditions, i.e. Simply-Simply, Clamped-Simply and Clamped-Clamped. The results show that the influence of the surface effects on the natural frequencies of the Aluminum nanobeams follows the order CC تفاصيل المقالة -
حرية الوصول المقاله
140 - Static Analysis of Functionally Graded Annular Plate Resting on Elastic Foundation Subject to an Axisymmetric Transverse Load Based on the Three Dimensional Theory of Elasticity
A Behravan Rad A Alibeigloo S.S MalihiIn this paper, static analysis of functionally graded annular plate resting on elastic foundation with various boundary conditions is carried out by using a semi-‍analytical approach‍ (SSM‍-DQM). The differential governing equations are presented based on th أکثرIn this paper, static analysis of functionally graded annular plate resting on elastic foundation with various boundary conditions is carried out by using a semi-‍analytical approach‍ (SSM‍-DQM). The differential governing equations are presented based on the three dimensional theory of elasticity. The plate is assumed isotropic at any point, while material properties to vary exponentially through the thickness direction and the Poisson’s ratio remain constant. The system of governing partial differential equations can be writhen as state equations by expanding the state variables and using the state space method (SSM) about thickness direction and applying the one dimensional differential quadrature method (DQM) along the radial direction. Interactions between the plate and two parameter elastic foundations are treated as boundary conditions. The stresses and displacements distributions are obtained by solving these state equations. In this study, the influences of the material property graded index, the elastic foundation coefficients (Winkler-Pasternak), the thickness to radius ratio, and edge supports effect on the bending behavior of the FGM annular plate are investigated and discussed in details. تفاصيل المقالة -
حرية الوصول المقاله
141 - Wave Propagation and Fundamental Solution of Initially Stressed Thermoelastic Diffusion with Voids
R Kumar R. KumarThe present article deals with the study of propagation of plane waves in isotropic generalized thermoelastic diffusion with voids under initial stress. It is found that, for two dimensional model of isotropic generalized thermoelastic diffusion with voids under initial أکثرThe present article deals with the study of propagation of plane waves in isotropic generalized thermoelastic diffusion with voids under initial stress. It is found that, for two dimensional model of isotropic generalized thermoelastic diffusion with voids under initial stress, there exists four coupled waves namely, P wave, Mass Diffusion (MD) wave, thermal (T) wave and Volume Fraction (VF) wave. The phase propagation velocities and attenuation quality factor of these plane waves are also computed and depicted graphically. In addition, the fundamental solution of system of differential equations in the theory of initially stressed thermoelastic diffusion with voids in case of steady oscillations in terms of elementary functions has been constructed. Some basic properties of the fundamental solution are established and some particular cases are also discussed. تفاصيل المقالة -
حرية الوصول المقاله
142 - Vibrations of Circular Plates with Guided Edge and Resting on Elastic Foundation
L.B Rao C.K RaoIn this paper, transverse vibrations of thin circular plates with guided edge and resting on Winkler foundation have been studied on the basis of Classical Plate Theory. Parametric investigations on the vibration of circular plates resting on elastic foundation have bee أکثرIn this paper, transverse vibrations of thin circular plates with guided edge and resting on Winkler foundation have been studied on the basis of Classical Plate Theory. Parametric investigations on the vibration of circular plates resting on elastic foundation have been carried out with respect to various foundation stiffness parameters. Twelve vibration modes are presented. The location of the stepped region with respect to foundation stiffness parameter is presented. تفاصيل المقالة -
حرية الوصول المقاله
143 - Implementing the New First and Second Differentiation of a General Yield Surface in Explicit and Implicit Rate-Independent Plasticity
F Moayyedian M KadkhodayanIn the current research with novel first and second differentiations of a yield function, Euler forward along with Euler backward with its consistent elastic-plastic modulus are newly implemented in finite element program in rate-independent plasticity. An elastic-plast أکثرIn the current research with novel first and second differentiations of a yield function, Euler forward along with Euler backward with its consistent elastic-plastic modulus are newly implemented in finite element program in rate-independent plasticity. An elastic-plastic internally pressurized thick walled cylinder is analyzed with four famous criteria including both pressure dependent and independent. The obtained results are in good agreement with experimental results. The consistent/continuum elastic-plastic moduli for Euler backward method are also investigated. تفاصيل المقالة -
حرية الوصول المقاله
144 - Wave Propagation at the Boundary Surface of Inviscid Fluid Half-Space and Thermoelastic Diffusion Solid Half-Space with Dual-Phase-Lag Models
R Kumar V GuptaThe present investigation deals with the reflection and transmission phenomenon due to incident plane longitudinal wave at a plane interface between inviscid fluid half-space and a thermoelastic diffusion solid half-space with dual-phase-lag heat transfer (DPLT) and dua أکثرThe present investigation deals with the reflection and transmission phenomenon due to incident plane longitudinal wave at a plane interface between inviscid fluid half-space and a thermoelastic diffusion solid half-space with dual-phase-lag heat transfer (DPLT) and dual-phase-lag diffusion (DPLD) models. The theory of thermoelasticity with dual-phase-lag heat transfer developed by Roychoudhary [10] has been employed to develop the equation for thermoelastic diffusion with dual-phase-lag heat transfer and dual-phase-lag diffusion model. Amplitude ratios and energy ratios of various reflected and transmitted waves are obtained. It is found that these are the functions of angle of incidence, frequency of incident wave and are influenced by thermoelastic diffusion properties of media. The nature of dependence of amplitude ratios and energy ratios with the angle of incidence have been computed numerically for a particular model. The variations of energy ratios with angle of incidence are also shown graphically. The conservation of energy at the interface is verified. Some special cases are also deduced from the present investigation. تفاصيل المقالة -
حرية الوصول المقاله
145 - A Rapidly Convergent Nonlinear Transfinite Element Procedure for Transient Thermoelastic Analysis of Temperature-Dependent Functionally Graded Cylinders
M ShariyatIn the present paper, the nonlinear transfinite element procedure recently published by the author is improved by introducing an enhanced convergence criterion to significantly reduce the computational run-times. It is known that transformation techniques have been deve أکثرIn the present paper, the nonlinear transfinite element procedure recently published by the author is improved by introducing an enhanced convergence criterion to significantly reduce the computational run-times. It is known that transformation techniques have been developed mainly for linear systems, only. Due to using a huge number of time steps, employing the conventional time integration methods requires quite huge computational time and leads to remarkable error accumulation, numerical instability, or numerical damping, especially for long investigation times. The present method specially may be extended to problems where the required time steps are of the order of the round-off errors (e.g., coupled thermoelasticty problems). The present procedure is employed for transient thermoelastic analysis of thick-walled functionally graded cylinders with temperature-dependent material properties, as an example. To reduce the effect of the artificial local heat and stress shock source generation at the mutual boundaries of the elements, second order elements are used. Influences of various parameters on the temperature and stress distributions are investigated. Furthermore, results of the proposed transfinite element technique are compared with the results obtained by other references to verify the validity, accuracy, and efficiency of the proposed method. تفاصيل المقالة -
حرية الوصول المقاله
146 - Stress Analysis of Two-directional FGM Moderately Thick Constrained Circular Plates with Non-uniform Load and Substrate Stiffness Distributions
M.M Alipour M ShariyatIn the present paper, bending and stress analyses of two-directional functionally graded (FG) circular plates resting on non-uniform two-parameter foundations (Winkler-Pasternak foundations) are investigated using a first-order shear-deformation theory. To enhance the a أکثرIn the present paper, bending and stress analyses of two-directional functionally graded (FG) circular plates resting on non-uniform two-parameter foundations (Winkler-Pasternak foundations) are investigated using a first-order shear-deformation theory. To enhance the accuracy of the results, the transverse stress components are derived based on the three dimensional theory of elasticity. The solution is obtained by employing the differential transform method (DTM). The material properties are assumed to vary in both transverse and radial directions according to power and exponential laws, respectively. Intensity of the transverse load is considered to vary according to a second-order polynomial. The performed convergence analysis and the comparative studies demonstrate the high accuracy and high convergence rate of the approach. A sensitivity analysis consisting of evaluating effects of different parameters (e.g., exponents of the material properties, thickness to radius ratio, trend of variations of the foundation stiffness, and edge conditions) is carried out. Results reveal that in contrast to the available constitutive-law-based solutions, present solution guarantees continuity of the transverse stresses at the interfaces between layers and may also be used for stress analysis of the sandwich panels. The results are reported for the first time and are discussed in detail. تفاصيل المقالة -
حرية الوصول المقاله
147 - Vibration Analysis of a Rotating Nanoplate Using Nonlocal Elasticity Theory
M Ghadiri N Shafiei S Hossein AlaviThe nanostructures under rotation have high promising future to be used in nano-machines, nano-motors and nano-turbines. They are also one of the topics of interests and it is new in designing of rotating nano-systems. In this paper, the scale-dependent vibration analys أکثرThe nanostructures under rotation have high promising future to be used in nano-machines, nano-motors and nano-turbines. They are also one of the topics of interests and it is new in designing of rotating nano-systems. In this paper, the scale-dependent vibration analysis of a nanoplate with consideration of the axial force due to the rotation has been investigated. The governing equation and boundary conditions are derived using the Hamilton’s principle based on nonlocal elasticity theory. The boundary conditions of the nanoplate are considered as free-free in y direction and two clamped-free (cantilever plate) and clamped-simply (propped cantilever) in x direction. The equations have been solved using differential quadrature method to determine natural frequencies of the rotating nanoplate. For validation, in special cases, it has been shown that the obtained results coincide with literatures. The effects of the nonlocal parameter, aspect ratio, hub radius, angular velocity and different boundary conditions on the first three frequencies have been investigated. Results show that vibration behavior of the rotating nanoplate with cantilever boundary condition is different from other boundary conditions. تفاصيل المقالة -
حرية الوصول المقاله
148 - Theory of Generalized Piezoporo Thermoelasticity
M Jabbari A YooshiIn this paper, the basic constitutive equations and equations of motion are derived to describe the behavior of thermoelastic porous piezoelectric medium by using Biot’s theory and the theory of generalized thermoelasticity with on relaxation time (Lord-Shulman). أکثرIn this paper, the basic constitutive equations and equations of motion are derived to describe the behavior of thermoelastic porous piezoelectric medium by using Biot’s theory and the theory of generalized thermoelasticity with on relaxation time (Lord-Shulman). The electrical enthalpy density function is derived in the general coordinates. Also, clear definitions for the poroelastic modulus, electrical, thermal and additional mixed coefficients are embedded. The uniqueness of the solution for the complete system of equations is presented. تفاصيل المقالة -
حرية الوصول المقاله
149 - Nonlocal DQM for Large Amplitude Vibration of Annular Boron Nitride Sheets on Nonlinear Elastic Medium
A Ghorbanpour Arani R Kolahchi S.M.R AllahyariOne of the most promising materials in nanotechnology such as sensors, actuators and resonators is annular Boron Nitride sheets (ABNSs) due to excelled electro-thermo-mechanical properties. In this study, however, differential quadrature method (DQM) and nonlocal piezoe أکثرOne of the most promising materials in nanotechnology such as sensors, actuators and resonators is annular Boron Nitride sheets (ABNSs) due to excelled electro-thermo-mechanical properties. In this study, however, differential quadrature method (DQM) and nonlocal piezoelasticity theory are used to investigate the nonlinear vibration response of embedded single-layered annular Boron Nitride sheets (SLABNSs). The interactions between the SLABNSs and its surrounding elastic medium are simulated by nonlinear Pasternak foundation. A detailed parametric study is conducted to elucidate the influences of the nonlocal parameter, elastic medium, temperature change and maximum amplitude on the nonlinear frequency of the SLABNSs. Results indicate that with increasing nonlocal parameter, the frequency of the coupled system becomes lower. The results are in good agreement with the previous researches. تفاصيل المقالة -
حرية الوصول المقاله
150 - An Exact Solution for Classic Coupled Thermoporoelasticity in Cylindrical Coordinates
M Jabbari H DehbaniIn this paper the classic coupled thermoporoelasticity model of hollow and solid cylinders under radial symmetric loading condition (r, t) is considered. A full analytical method is used and an exact unique solution of the classic coupled equations is presented. The the أکثرIn this paper the classic coupled thermoporoelasticity model of hollow and solid cylinders under radial symmetric loading condition (r, t) is considered. A full analytical method is used and an exact unique solution of the classic coupled equations is presented. The thermal and pressure boundary conditions, the body force, the heat source, and the injected volume rate per unit volume of a distribute water source are considered in the most general forms, and no limiting assumption is used. This generality allows simulation of various applicable problems. تفاصيل المقالة -
حرية الوصول المقاله
151 - On the Magneto-Thermo-Elastic Behavior of a Functionally Graded Cylindrical Shell with Pyroelectric Layers Featuring Interlaminar Bonding Imperfections Rested in an Elastic Foundation
M Saadatfar M Aghaie-KhafriThe behavior of an exponentially graded hybrid cylindrical shell subjected to an axisymmetric thermo-electro-mechanical loading placed in a constant magnetic field is investigated. The hybrid shell is consisted of a functionally graded host layer embedded with pyroelect أکثرThe behavior of an exponentially graded hybrid cylindrical shell subjected to an axisymmetric thermo-electro-mechanical loading placed in a constant magnetic field is investigated. The hybrid shell is consisted of a functionally graded host layer embedded with pyroelectric layers as sensor and/or actuator that can be imperfectly bonded to the inner and the outer surfaces of a shell. The shell is simply supported and could be rested on an elastic foundation. The material properties of the host layer are assumed to be exponentially graded in the radial direction. To solve governing differential equations, the Fourier series expansion method along the longitudinal direction and the differential quadrature method (DQM) across the thickness direction are used. Numerical examples are presented to discuss effective parameters influence on the response of the hybrid shell. تفاصيل المقالة -
حرية الوصول المقاله
152 - Third Order Formulation for Vibrating Non-Homogeneous Cylindrical Shells in Elastic Medium
M Gheisari H Molatefi S.S AhmadiThird order shear deformation theory of cylindrical shells is employed to investigate the vibration characteristics of non-homogeneous cylindrical shells surrounded by an elastic medium. The kinematic relations are obtained using the strain-displacement relations of Don أکثرThird order shear deformation theory of cylindrical shells is employed to investigate the vibration characteristics of non-homogeneous cylindrical shells surrounded by an elastic medium. The kinematic relations are obtained using the strain-displacement relations of Donnell shell theory. The shell properties are considered to be dependent on both position and thermal environment. A suitable function through the thickness direction is assumed for the non-homogeneity property. The Winkler-Pasternak elastic foundation is used to model the elastic medium. Analytical solutions are presented for cylindrical shells with simply supported boundary conditions. From the numerical studies, it is revealed that, the natural frequencies are affected significantly by the elastic foundation coefficients and environmental temperature conditions. تفاصيل المقالة -
حرية الوصول المقاله
153 - Influence of the Elastic Foundation on the Free Vibration and Buckling of Thin-Walled Piezoelectric-Based FGM Cylindrical Shells Under Combined Loadings
M Mohammadimehr M Moradi A LoghmanIn this paper, the influence of the elastic foundation on the free vibration and buckling of thin-walled piezoelectric-based functionally graded materials (FGM) cylindrical shells under combined loadings is investigated. The equations of motion are obtained by using the أکثرIn this paper, the influence of the elastic foundation on the free vibration and buckling of thin-walled piezoelectric-based functionally graded materials (FGM) cylindrical shells under combined loadings is investigated. The equations of motion are obtained by using the principle of Hamilton and Maxwell's equations and the Navier's type solution used to solve these equations. Material properties are changed according to power law in the direction of thickness. In this study, the effects of Pasternak elastic foundation coefficients and also the effects of material distribution, geometrical ratios and loading conditions on the natural frequencies are studied. It is observed that by increasing Pasternak elastic medium coefficients, the natural frequencies of functionally graded piezoelectric materials (FGPM) cylindrical shell always increases. The mode shapes of FGPM cylindrical shell has been shown in this research and the results show that the distribution of the radial displacements is more significant than circumferential and longitudinal displacements. تفاصيل المقالة -
حرية الوصول المقاله
154 - Analytical Solution for Response of Piezoelectric Cylinder Under Electro-Thermo-Mechanical Fields
S Golabi J Jafari FesharakiThis paper presents an analytical solution for response of a piezoelectric hollow cylinder under two-dimensional electro thermo mechanical fields. The solution is based on a direct method and the Navier equations were solved using the complex Fourier series. The advanta أکثرThis paper presents an analytical solution for response of a piezoelectric hollow cylinder under two-dimensional electro thermo mechanical fields. The solution is based on a direct method and the Navier equations were solved using the complex Fourier series. The advantage of this method is its generality and from mathematical point of view, any type of the thermo mechanical and electrical boundary conditions can be considered without any restrictions. The thermo mechanical and electrical displacements are assumed that vary in radial and circumferential directions. Finally, three examples were considered to confirm the results and investigate the effect of in-phase and opposite-phase electro thermo mechanical boundary loads on two-dimensional electro thermo mechanical behavior of piezoelectric hollow cylinder. The results are compared with the previous work and FEM analysis. The main result of this study is that, by applying a proper distribution of thermal, electrical and mechanical fields, the distributions of electric and mechanical displacement, thermal and mechanical stresses can be controlled. تفاصيل المقالة -
حرية الوصول المقاله
155 - Wave Propagation at the Boundary Surface of Elastic Layer Overlaying a Thermoelastic Without Energy Dissipation Half-space
R Kumar V ChawlaThe present investigation is to study the surface wave propagation at imperfect boundary between an isotropic thermoelastic without energy dissipation half-space and an isotropic elastic layer of finite thickness. The penetration depth of longitudinal, transverse, and t أکثرThe present investigation is to study the surface wave propagation at imperfect boundary between an isotropic thermoelastic without energy dissipation half-space and an isotropic elastic layer of finite thickness. The penetration depth of longitudinal, transverse, and thermal waves has been obtained. The secular equation for surface waves in compact form is derived after developing the mathematical model. The components of temperature distribution, normal and tangential stress are computed at the interface and presented graphically. The effect of stiffness is shown on the resulting amplitudes and the effect of thermal is shown on the penetration depth of various waves. A particular case of interest is also deduced. Some special cases of interest are also deduced from the present investigation. تفاصيل المقالة -
حرية الوصول المقاله
156 - Optimization of Functionally Graded Beams Resting on Elastic Foundations
M.H Yas S Kamarian J.E Jam A PourasgharIn this study, two goals are followed. First, by means of the Generalized Differential Quadrature (GDQ) method, parametric analysis on the vibration characteristics of three-parameter Functionally Graded (FG) beams on variable elastic foundations is studied. These param أکثرIn this study, two goals are followed. First, by means of the Generalized Differential Quadrature (GDQ) method, parametric analysis on the vibration characteristics of three-parameter Functionally Graded (FG) beams on variable elastic foundations is studied. These parameters include (a) three parameters of power-law distribution, (b) variable Winkler foundation modulus, (c) two-parameter elastic foundation modulus. Then, volume fraction optimization of FG beam with respect to the fundamental frequency is studied. Since the optimization process is so complicated and time consuming, Genetic Algorithm (GA), a computational algorithm based on Darwinian theories that allow to solve optimization problems without using gradient-based information on the objective functions and the constraints, is performed to obtain the best material profile through the thickness to maximize the first natural frequency. A proper Artificial Neural Network (ANN) is trained by training data sets obtained from GDQ method and then is applied as the objective function in genetic algorithm by reproducing the fundamental frequency for improving the speed of the optimization process. Finally, the optimized material profile for the maximum natural frequency of a FG beam resting on elastic foundations is presented. تفاصيل المقالة -
حرية الوصول المقاله
157 - Effect of Exponentially-Varying Properties on Displacements and Stresses in Pressurized Functionally Graded Thick Spherical Shells with Using Iterative Technique
M Zamani Nejad A Rastgoo A HadiA semi-analytical iterative method as one of the newest analytical methods is used for the elastic analysis of thick-walled spherical pressure vessels made of functionally graded materials subjected to internal pressure. This method is accurate, fast and has a reasonabl أکثرA semi-analytical iterative method as one of the newest analytical methods is used for the elastic analysis of thick-walled spherical pressure vessels made of functionally graded materials subjected to internal pressure. This method is accurate, fast and has a reasonable order of convergence. It is assumed that material properties except Poisson’s ratio are graded through the thickness direction of the sphere according to an exponential distribution. For different values of inhomogeneity constant, distributions of radial displacement, radial stress, circumferential stress, and von Mises equivalent stress, as a function of radial direction, are obtained. A numerical solution, using finite element method (FEM), is also presented. Good agreement was found between the semi-analytical results and those obtained through FEM. تفاصيل المقالة -
حرية الوصول المقاله
158 - Closed-form Solution of Dynamic Displacement for SLGS Under Moving the Nanoparticle on Visco-Pasternak Foundation
A Ghorbanpour Arani A Shiravand S AmirIn this paper, forced vibration analysis of a single-layered graphene sheet (SLGS) under moving a nanoparticle is carried out using the non-local elasticity theory of orthotropic plate. The SLGS under moving the nanoparticle is placed in the elastic and viscoelastic fou أکثرIn this paper, forced vibration analysis of a single-layered graphene sheet (SLGS) under moving a nanoparticle is carried out using the non-local elasticity theory of orthotropic plate. The SLGS under moving the nanoparticle is placed in the elastic and viscoelastic foundation which are simulated as a Pasternak and Visco-Pasternak medium, respectively. Movement of the nanoparticle is considered as a linear movement with constant velocity from an edge to another edge of graphene sheet. Using the non-linear Von Kármán strain-displacement relations and Hamilton’s principle, the governing differential equations of motion are derived. The differential equation of motion for all edges simply supported boundary condition is solved by an analytical method and therefore, the dynamic displacement of SLGS is presented as a closed-form solution of that. The influences of medium stiffness (Winkler, Pasternak and damper modulus parameter), nonlocal parameter, aspect ratio, mechanical properties of graphene sheet, time and velocity parameter on dimensionless displacement (dynamic displacement to static displacement of SLGS) are studied. The results indicate that, as the values of stiffness modulus parameter increase, the maximum dynamic displacement of SLGS decreases. Therefore, the results are in good agreement with the previous researches. تفاصيل المقالة -
حرية الوصول المقاله
159 - Three-dimensional Free Vibration Analysis of a Transversely Isotropic Thermoelastic Diffusive Cylindrical Panel
R Kumar T KansalThe present paper is aimed to study an exact analysis of the free vibrations of a simply supported, homogeneous, transversely isotropic, cylindrical panel based on three-dimensional generalized theories of thermoelastic diffusion. After applying the displacement potenti أکثرThe present paper is aimed to study an exact analysis of the free vibrations of a simply supported, homogeneous, transversely isotropic, cylindrical panel based on three-dimensional generalized theories of thermoelastic diffusion. After applying the displacement potential functions in the basic governing equations of generalized thermoelastic diffusion, it is noticed that a purely transverse mode is independent of thermal and concentration fields and gets decoupled from the rest of motion. The equations for free vibration problem are reduced to four equations of second-order and one fourth-order ordinary differential equation after expanding the displacement potential, temperature change and concentration functions with an orthogonal series. The formal solution of this system of equations can be expressed by using modified Bessel function with complex arguments. The numerical results for lowest frequency have been obtained and presented graphically. The effect of diffusion on lowest frequency has also been presented graphically. Some special cases of secular equation are also discussed. تفاصيل المقالة -
حرية الوصول المقاله
160 - Thermo-elastic Damping in a Capacitive Micro-beam Resonator Considering Hyperbolic Heat Conduction Model and Modified Couple Stress Theory
M Najafi G Rezazadeh R ShabaniIn this paper, the quality factor of thermo-elastic damping in an electro-statically deflected micro-beam resonator has been investigated. The thermo-elastic coupled equations for the deflected micro-beam have been derived using variational and Hamilton principles based أکثرIn this paper, the quality factor of thermo-elastic damping in an electro-statically deflected micro-beam resonator has been investigated. The thermo-elastic coupled equations for the deflected micro-beam have been derived using variational and Hamilton principles based on modified couple stress theory and hyperbolic heat conduction model. The thermo-elastic damping has been obtained discretizing the governing equations over spatial domain and applying complex frequency approach. The effects of the applied bias DC voltage, playing simultaneously role of an external force and softening parameter, on the quality factor have been studied. The obtained results of the modified couple stress and classic theories are compared and the effects of the material internal length-scale parameter on the differences between results of two theories have been discussed. In addition, the effects of different parameters such as beam length and ambient temperature on the quality factor have been studied. تفاصيل المقالة -
حرية الوصول المقاله
161 - Magneto-Thermo-Elastic Stresses and Perturbation of Magnetic Field Vector in a Thin Functionally Graded Rotating Disk
A Ghorbanpour Arani S AmirIn this paper, a semi-analytical solution for magneto-thermo-elastic problem in an axisymmetric functionally graded (FG) hollow rotating disk with constant thickness placed in uniform magnetic and thermal fields with heat convection from disk’s surfaces is present أکثرIn this paper, a semi-analytical solution for magneto-thermo-elastic problem in an axisymmetric functionally graded (FG) hollow rotating disk with constant thickness placed in uniform magnetic and thermal fields with heat convection from disk’s surfaces is presented. Solution for stresses and perturbation of magnetic field vector in a thin FG rotating disk is determined using infinitesimal theory of magneto-thermo-elasticity under plane stress conditions. The material properties except Poisson’s ratio are modeled as power-law distribution of volume fraction. The non-dimensional distribution of temperature, displacement, stresses and perturbation of magnetic field vector throughout radius are determined. The effects of the material grading index and the magnetic field on the stress and displacement fields are investigated. The results of stresses and radial displacements for two different boundary conditions are compared with the case of a thin FG rotating disk with the same loading and boundary conditions but in the absence of magnetic field. It has been found that imposing a magnetic field significantly decreases tensile circumferential stresses. Therefore, the fatigue life of the disk will be significantly improved by applying the magnetic field. The results of this investigation can be used for optimum design of rotating disks. تفاصيل المقالة -
حرية الوصول المقاله
162 - Wave Propagation in Sandwich Panel with Auxetic Core
D Qing-Tian Y Zhi-ChunAuxetic cellular solids in the forms of honeycombs and foams have great potential in a diverse range of applications, including as core material in curved sandwich panel composite components, radome applications, directional pass band filters, adaptive and deployable st أکثرAuxetic cellular solids in the forms of honeycombs and foams have great potential in a diverse range of applications, including as core material in curved sandwich panel composite components, radome applications, directional pass band filters, adaptive and deployable structures, filters and sieves, seat cushion material, energy absorption components, viscoelastic damping materials and fastening devices etc.In this paper, the characteristic of wave propagation in sandwich panel with auxetic core is analyzed. A three-layer sandwich panel is considered which is discretized in the thickness direction by using semi-analytical finite element method. Wave propagation equations are obtained through some algebraic manipulation and applying standard finite element assembling procedures. The mechanical properties of auxetic core can be described by the geometric parameters of the unit cell and mechanical properties of the virgin core material. The characteristics of wave propagation in sandwich panel with conventional hexagonal honeycomb core and re-entrant auxetic core are discussed, and effects of panel thickness, geometric properties of unit cell on dispersive curves are also discussed. Variations of Poisson’s ratio and core density with inclined angle are presented. تفاصيل المقالة -
حرية الوصول المقاله
163 - Thermo-Viscoelastic Interaction Subjected to Fractional Fourier law with Three-Phase-Lag Effects
P Pal A Sur M KanoriaIn this paper, a new mathematical model of a Kelvin-Voigt type thermo-visco-elastic, infinite thermally conducting medium has been considered in the context of a new consideration of heat conduction having a non-local fractional order due to the presence of periodically أکثرIn this paper, a new mathematical model of a Kelvin-Voigt type thermo-visco-elastic, infinite thermally conducting medium has been considered in the context of a new consideration of heat conduction having a non-local fractional order due to the presence of periodically varying heat sources. Three-phase-lag thermoelastic model, Green Naghdi models II and III (i.e., the models which predicts thermoelasticity without energy dissipation (TEWOED) and with energy dissipation (TEWED)) are employed to study the thermo-mechanical coupling, thermal and mechanical relaxation effects. In the absence of mechanical relaxations (viscous effect), the results for various generalized theories of thermoelasticity may be obtained as particular cases. The governing equations are expressed in Laplace-Fourier double transform domain. The inversion of the Fourier transform is carried out using residual calculus, where the poles of the integrand are obtained numerically in complex domain by using Laguerre's method and the inversion of the Laplace transform is done numerically using a method based on Fourier series expansion technique. Some comparisons have been shown in the form of the graphical representations to estimate the effect of the non-local fractional parameter and the effect of viscosity is also shown. تفاصيل المقالة -
حرية الوصول المقاله
164 - Mechanical Stresses in a Linear Plastic FGM Hollow and Solid Rotational Disk
M Jabbari A Hatefkia M ShokouhfarIn this paper, an analytical solution for computing the plastic & linear plastic stresses and critical angular velocity in a FGM hollow & solid rotating disk is developed. It has been assumed that the modulus of elasticity and yield strength were varying through أکثرIn this paper, an analytical solution for computing the plastic & linear plastic stresses and critical angular velocity in a FGM hollow & solid rotating disk is developed. It has been assumed that the modulus of elasticity and yield strength were varying through thickness of the FGM material according to a power law relationship. The Poisson's ratio were considered constant throughout the thickness. In the analysis presented here the effect of non-homogeneity in FGM rotating disk was implemented by choosing a dimensionless parameter, named m, which could be assigned an arbitrary value affecting the stresses in the rotating disk. Distribution of stresses in radial and circumferential directions for FGM rotating disk under the influence of angular velocity were obtained. Graphs of variations of stress, critical angular velocity versus radius of the rotating disk were plotted. The direct method is used to solve the Navier equations. تفاصيل المقالة -
حرية الوصول المقاله
165 - Torsional Waves in Prestressed Fiber Reinforced Medium Subjected to Magnetic Field
R Kakar S KakarThe propagation of torsional waves in a prestressed fiber-reinforced half-space under the effect of magnetic field and gravity has been discussed. The problem has been solved analytically using Whittaker function to obtain the exact solution frequency equations. Numeric أکثرThe propagation of torsional waves in a prestressed fiber-reinforced half-space under the effect of magnetic field and gravity has been discussed. The problem has been solved analytically using Whittaker function to obtain the exact solution frequency equations. Numerical results for stress, gravity and magnetic field are given and illustrated graphically. Comparisons are made with the results predicted by the boundary value condition for rigid boundary and for traction free boundary in the presence and in the absence of the effect of a magnetic field, gravity and stress. It is found that the reinforcement, gravity and magnetic field have great effects on the distribution. تفاصيل المقالة -
حرية الوصول المقاله
166 - Two-dimensional Axisymmetric Electromechanical Response of Piezoelectric, Functionally Graded and Layered Composite Cylinders
T Kant P DesaiA mixed semi-analytical cum numerical approach is presented in this paper which accounts for the coupled mechanical and electrical response of piezoelectric, functionally graded (FG) and layered composite hollow circular cylinders of finite length. Under axisymmetric me أکثرA mixed semi-analytical cum numerical approach is presented in this paper which accounts for the coupled mechanical and electrical response of piezoelectric, functionally graded (FG) and layered composite hollow circular cylinders of finite length. Under axisymmetric mechanical and electrical loadings, the three-dimensional problem (3D) gets reduced to a two-dimensional (2D) plane strain problem of elasticity. The 2D problem is further simplified and reduced to a one-dimensional (1D) by assuming an analytical solution in longitudinal direction (z) in terms of Fourier series expansion which satisfies the simply (diaphragm) supported boundary conditions exactly at the two ends z = 0, l. Fundamental (basic) dependent variables are chosen in the radial direction (thickness coordinate) of the cylinder. The resulting mathematical model is cast in the form of first order simultaneous ordinary differential equations which are integrated through an effective numerical integration technique by first transforming the BVP into a set of initial value problems (IVPs). The cylinder is subjected to internal/external pressurized mechanical and an electrical loading. Finally, numerical results are obtained which govern the active and sensory response of piezoelectric and FG cylinders. Numerical results are compared for their accuracy with available results. New results of finite length cylinders are generated and presented for future reference. تفاصيل المقالة -
حرية الوصول المقاله
167 - Transversely Isotropic Magneto-Visco Thermoelastic Medium with Vacuum and without Energy Dissipation
R Kumar P Kaushal R SharmaIn the present investigation the disturbances in a homogeneous transversely isotropic magneto-Visco thermoelastic rotating medium with two temperature due to thermomechanical sources has been addressed. The thermoelasticity theories developed by Green-Naghdi (Type II an أکثرIn the present investigation the disturbances in a homogeneous transversely isotropic magneto-Visco thermoelastic rotating medium with two temperature due to thermomechanical sources has been addressed. The thermoelasticity theories developed by Green-Naghdi (Type II and Type III) both with and without energy dissipation has been applied to the thermomechanical sources. The Laplace and Fourier transform techniques have been applied to solve the present problem. As an application, the bounding surface is subjected to concentrated and distributed sources (mechanical and thermal sources). The analytical expressions of displacement, stress components, temperature change and induced magnetic field are obtained in the transformed domain. Numerical inversion techniques have been applied to obtain the results in the physical domain. Numerical simulated results are depicted graphically to show the effect of viscosity on the resulting quantities. Some special cases of interest are also deduced from the present investigation. تفاصيل المقالة -
حرية الوصول المقاله
168 - Plane Strain Deformation of a Poroelastic Half-Space Lying Over Another Poroelastic Half-Space
A Miglani N KumariThe plane strain deformation of an isotropic, homogeneous, poroelastic medium caused by an inclined line-load is studied using the Biot linearized theory for fluid saturated porous materials. The analytical expressions for the displacements and stresses in the medium ar أکثرThe plane strain deformation of an isotropic, homogeneous, poroelastic medium caused by an inclined line-load is studied using the Biot linearized theory for fluid saturated porous materials. The analytical expressions for the displacements and stresses in the medium are obtained by applying suitable boundary conditions. The solutions are obtained analytically for the limiting case of undrained conditions in high frequency limit. The undrained displacements, stresses and pore pressure in poroelastic medium are plotted and discussed to draw the conclusions. تفاصيل المقالة -
حرية الوصول المقاله
169 - Response of GN Type II and Type III Theories on Reflection and Transmission Coefficients at the Boundary Surface of Micropolar Thermoelastic Media with Two Temperatures
R Kumar M Kaur S.C RajvanshiIn the present article, the reflection and transmission of plane waves at the boundary of thermally conducting micropolar elastic media with two temperatures is studied. The theory of thermoelasticity with and without energy dissipation is used to investigate the proble أکثرIn the present article, the reflection and transmission of plane waves at the boundary of thermally conducting micropolar elastic media with two temperatures is studied. The theory of thermoelasticity with and without energy dissipation is used to investigate the problem. The expressions for amplitudes ratios of reflected and transmitted waves at different angles of incident wave are obtained. Dissipation of energy and two temperature effects on these amplitude ratios with angle of incidence are depicted graphically. Some special and particular cases are also deduced. تفاصيل المقالة -
حرية الوصول المقاله
170 - Analysis of Five Parameter Viscoelastic Model Under Dynamic Loading
R Kakar K Kaur K.C GuptaThe purpose of this paper is to analysis the viscoelastic models under dynamic loading.A five-parameter model is chosen for study exhibits elastic, viscous, and retarded elastic response to shearing stress. The viscoelastic specimen is chosen which closely approximates أکثرThe purpose of this paper is to analysis the viscoelastic models under dynamic loading.A five-parameter model is chosen for study exhibits elastic, viscous, and retarded elastic response to shearing stress. The viscoelastic specimen is chosen which closely approximates the actual behavior of a polymer. The module of elasticity and viscosity coefficients are assumed to be space dependent i.e. functions of in non-homogeneous case and stress-strain are harmonic functions of time The expression for relaxation time for five parameter viscoelastic model is obtained by using constitutive equation. The dispersion equation is obtained by using Ray techniques. The model is justified with the help of cyclic loading for maxima or minima. تفاصيل المقالة -
حرية الوصول المقاله
171 - Displacement Field Due to a Cylindrical Inclusion in a Thermoelastic Half-Space
K Singh M RenuIn this paper, the closed form analytical expressions for the displacement field due to a cylindrical inclusion in a thermoelastic half-space are obtained. These expressions are derived in the context of steady-state uncoupled thermoelasticity using thermoelastic displa أکثرIn this paper, the closed form analytical expressions for the displacement field due to a cylindrical inclusion in a thermoelastic half-space are obtained. These expressions are derived in the context of steady-state uncoupled thermoelasticity using thermoelastic displacement potential functions. The thermal displacement field is generated due to differences in the coefficients of linear thermal expansion between a subregion and the surrounding material. Further, comparison between displacement field in a half-space and in an infinite medium has been discussed. The variation of displacement field in a half-space and its comparison with an infinite medium is also shown graphically. تفاصيل المقالة -
حرية الوصول المقاله
172 - Variational Principle, Uniqueness and Reciprocity Theorems in Porous Piezothermoelastic with Mass Diffusion
R Kumar P SharmaThe basic governing equations in anisotropic elastic material under the effect of porous piezothermoelastic are presented. Biot [1], Lord & Shulman [4] and Sherief et al. [5] theories are used to develop the basic equations for porous piezothermoelastic with mass di أکثرThe basic governing equations in anisotropic elastic material under the effect of porous piezothermoelastic are presented. Biot [1], Lord & Shulman [4] and Sherief et al. [5] theories are used to develop the basic equations for porous piezothermoelastic with mass diffusion material. The variational principle, uniqueness theorem and theorem of reciprocity in this model are established under the assumption of positive definiteness of elastic, porousthermal, chemical potential and electric field. تفاصيل المقالة -
حرية الوصول المقاله
173 - Elastic-Plastic Transition of Pressurized Functionally Graded Orthotropic Cylinder using Seth’s Transition Theory
S Sharma R PanchalIn this paper the radial deformation and the corresponding stresses in a functionally graded orthotropic hollow cylinder with the variation in thickness and density according to power law and rotating about its axis under pressure is investigated by using Seth's transit أکثرIn this paper the radial deformation and the corresponding stresses in a functionally graded orthotropic hollow cylinder with the variation in thickness and density according to power law and rotating about its axis under pressure is investigated by using Seth's transition theory. The material of the cylinder is assumed to be non-homogeneous and orthotropic. This theory helps to achieve better agreement between experimental and theoretical results. Results has been mentioned analytically and numerically. From the analysis, it has been concluded that cylinder made up of orthotropic material whose thickness increases radially and density decreases radially is on the safer side of the design as circumferential stresses are high for cylinder made up of isotropic material as compared to orthotropic material. This paper is based on elastic-plastic behavior which plays important role in practical design of structures for safety factor. تفاصيل المقالة -
حرية الوصول المقاله
174 - Vibration Analysis of FG Nanoplate Based on Third-Order Shear Deformation Theory (TSDT) and Nonlocal Elasticity
M.M Najafizadeh M Raki P YousefiIn present study, the third-order shear deformation theory has been developed to investigate vibration analysis of FG Nano-plates based on Eringen nonlocal elasticity theory. The materials distribution regarding to the thickness of Nano-plate has been considered based o أکثرIn present study, the third-order shear deformation theory has been developed to investigate vibration analysis of FG Nano-plates based on Eringen nonlocal elasticity theory. The materials distribution regarding to the thickness of Nano-plate has been considered based on two different models of power function and exponential function. All equations governing on the vibration of FG Nano-plate have been derived from Hamilton’s principle. It has been also obtained the analytical solution for natural frequencies and corresponding mode shapes of simply supported FG Nano-plates. In addition, the general form of stiffness and mass matrix elements has been expressed based on this theory. The effect of different parameters such as power and exponential indexes of targeted function , nonlocal parameter of Nano-plate, aspect ratio and thickness to length ratio of Nano-plate on non-dimensional natural frequencies of free vibration responses have been investigated. The obtained analytical results show an excellent agreement with other available solutions of previous studies. The formulation and analytical results obtained from proposed method can be used as a benchmark for further studies to develop this area of research. تفاصيل المقالة -
حرية الوصول المقاله
175 - Thermoelastic Analysis of Rotating Thick Truncated Conical Shells Subjected to Non-Uniform Pressure
M Jabbari M Zamani Nejad M GhannadIn the present work, a study of thermoelastic analysis of a rotating thick truncated conical shell subjected to the temperature gradient and non-uniform internal pressure is carried out. The formulation is based on first-order shear deformation theory (FSDT), which acco أکثرIn the present work, a study of thermoelastic analysis of a rotating thick truncated conical shell subjected to the temperature gradient and non-uniform internal pressure is carried out. The formulation is based on first-order shear deformation theory (FSDT), which accounts for the transverse shear. The governing equations, derived using minimum total potential energy principle, are solved, using multi-layered method (MLM). The model has been verified with the results of finite element method (FEM) for several tapering angles of the truncated cone. The numerical results obtained are presented graphically and the effects of thermal and mechanical loading, tapering angle of truncated cone, and profile of internal pressure are studied in detail. تفاصيل المقالة -
حرية الوصول المقاله
176 - Influences of Small-Scale Effect and Boundary Conditions on the Free Vibration of Nano-Plates: A Molecular Dynamics Simulation
S.F Asbaghian Namin R PilafkanThis paper addresses the influence of boundary conditions and small-scale effect on the free vibration of nano-plates using molecular dynamics (MD) and nonlocal elasticity theory. Based on the MD simulations, Large-scale Atomic/Molecular Massively Parallel Simulator (LA أکثرThis paper addresses the influence of boundary conditions and small-scale effect on the free vibration of nano-plates using molecular dynamics (MD) and nonlocal elasticity theory. Based on the MD simulations, Large-scale Atomic/Molecular Massively Parallel Simulator (LAMMPS) is used to obtain fundamental frequencies of single layered graphene sheets (SLGSs) which modeled in this paper as the most common nano-plates. On the other hand, governing equations are derived using nonlocal elasticity and the first-order shear deformation theory (FSDT). Afterwards, these equations solved using generalized differential quadrature method (GDQ). The small-scale effect is applied in the governing equations of motion by nonlocal parameter. The effects of different side lengths, boundary conditions, and nonlocal parameter are inspected for the aforementioned methods. The results obtained from the MD simulations are compared with those of nonlocal elasticity theory to calculate appropriate values for the nonlocal parameter. As a result, for the first time, the nonlocal parameter values are suggested for graphene sheets with various boundary conditions. Furthermore, it is shown that nonlocal elasticity approach using classical plate theory (CLPT) assumptions overestimates the natural frequencies. تفاصيل المقالة -
حرية الوصول المقاله
177 - Response of Two Temperatures on Wave Propagation in Micropolar Thermoelastic Materials with One Relaxation Time Bordered with Layers or Half Spaces of Inviscid Liquid
R Kumar M Kaur S.C RajvanshiThe present study is concerned with the propagation of Lamb waves in a homogeneous isotropic thermoelastic micropolar solid with two temperatures bordered with layers or half spaces of inviscid liquid subjected to stress free boundary conditions. The generalized theory أکثرThe present study is concerned with the propagation of Lamb waves in a homogeneous isotropic thermoelastic micropolar solid with two temperatures bordered with layers or half spaces of inviscid liquid subjected to stress free boundary conditions. The generalized theory of thermoelasticity developed by Lord and Shulman has been used to investigate the problem. The secular equations for symmetric and skew- symmetric leaky and nonleaky Lamb wave modes of propagation are derived. The phase velocity and attenuation coefficient are computed numerically and depicted graphically. The amplitudes of stress, microrotation vector and temperature distribution for the symmetric and skew-symmetric wave modes are computed analytically and presented graphically. Results of some earlier workers have been deduced as particular cases. تفاصيل المقالة -
حرية الوصول المقاله
178 - 3D Thermoelastic Interactions in an Anisotropic Lastic Slab Due to Prescribed Surface Temparature
Gh Debkumar L Abhijit R Kumar R SurathThe present paper is devoted to the determination of displacement, stresses and temperature from three dimensional anisotropic half spaces due to presence of heat source. The normal mode analysis technique has been used to the basic equations of motion and generalized h أکثرThe present paper is devoted to the determination of displacement, stresses and temperature from three dimensional anisotropic half spaces due to presence of heat source. The normal mode analysis technique has been used to the basic equations of motion and generalized heat conduction equation proposed by Green-Naghdi model-II [1]. The resulting equation are written in the form of a vector –matrix differential equation and exact expression for displacement component, stresses, strains and temperature are obtained by using eigen value approach. Finally, temperature, stresses and strain are presented graphically and analyzed. تفاصيل المقالة -
حرية الوصول المقاله
179 - Reflection and Transmission of Plane Waves at Micropolar Piezothermoelastic Solids
R Kumar M KaurThe present investigation analysis a problem of r eflection and transmission at an interface of two micropolar orthotropic piezothermoelastic media. The basic equations and constitutive relations for micropolar orthotropic piezothermoelastic media for G-L theory are d أکثرThe present investigation analysis a problem of r eflection and transmission at an interface of two micropolar orthotropic piezothermoelastic media. The basic equations and constitutive relations for micropolar orthotropic piezothermoelastic media for G-L theory are derived. The expressions for amplitude ratios corresponding to reflected and transmitted waves are derived analytically. The effect of angle of incidence, frequency, micropolarity, thermopiezoelectric interactions on the reflected and transmitted waves are studied numerically for a specific model. Some special cases of interest one are also deduced. تفاصيل المقالة -
حرية الوصول المقاله
180 - Free Vibration Analysis of Microtubules as Orthotropic Elastic Shells Using Stress and Strain Gradient Elasticity Theory
F Mokhtari Y Tadi BeniIn this paper, vibration of the protein microtubule, one of the most important intracellular elements serving as one of the common components among nanotechnology, biotechnology and mechanics, is investigated using stress and strain gradient elasticity theory and orthot أکثرIn this paper, vibration of the protein microtubule, one of the most important intracellular elements serving as one of the common components among nanotechnology, biotechnology and mechanics, is investigated using stress and strain gradient elasticity theory and orthotropic elastic shells model. Microtubules in the cell are influenced by internal and external stimulation and play a part in conveying protein substances and taking medications to the intended targets. Therefore, in order to control the biological cell functions, it is important to know the vibrational behavior of microtubules. For this purpose, using the cylindrical shell model which fully corresponds to microtubule geometry, and by considering it as orthotropic which is closer to reality, based on gradient elasticity theory, frequency analysis of the protein microtubule is carried out by considering Love’s thin shell theory and Navier solution. Also, the effect of size parameter and other variables on the results are investigated. تفاصيل المقالة -
حرية الوصول المقاله
181 - Effects of Hall Current and Rotation in Modified Couple Stress Generalized Thermoelastic Half Space due to Ramp-Type Heating
R Kumar Sh Devi V SharmaThe objective is to study the deformation in a homogeneous isotropic modified couple stress thermoelastic rotating medium in the presence of Hall current and magnetic field due to a ramp-type thermal source. The generalized theories of thermoelasticity developed by Lord أکثرThe objective is to study the deformation in a homogeneous isotropic modified couple stress thermoelastic rotating medium in the presence of Hall current and magnetic field due to a ramp-type thermal source. The generalized theories of thermoelasticity developed by Lord Shulman (L-S, 1967) and Green Lindsay (G-L, 1972) are used to investigate the problem. Laplace and Fourier transform technique is applied to obtain the solutions of the governing equations. The displacements, stress components, temperature change and mass concentration are obtained in the transformed domain. Numerical inversion technique has been used to obtain the solutions in the physical domain. Effects of Hall current and rotation are shown in a resulting quantities. Some special cases of interest are also deduced. تفاصيل المقالة -
حرية الوصول المقاله
182 - Extraction of Nonlinear Thermo-Electroelastic Equations for High Frequency Vibrations of Piezoelectric Resonators with Initial Static Biases
M.M Mohammadi M Hamedi H DaneshpajoohIn this paper, the general case of an anisotropic thermo-electro elastic body subjected to static biasing fields is considered. The biasing fields may be introduced by heat flux, body forces, external surface tractions, and electric fields. By introducing proper thermod أکثرIn this paper, the general case of an anisotropic thermo-electro elastic body subjected to static biasing fields is considered. The biasing fields may be introduced by heat flux, body forces, external surface tractions, and electric fields. By introducing proper thermodynamic functions and employing variational principle for a thermo-electro elastic body, the nonlinear constitutive relations and the nonlinear equation of motion are extracted. The equations have the advantage of employing the Lagrangian strain and second Piola-Kirchhoff stress tensor with symmetric characteristics. These equations are used to analyze the high frequency vibrations of piezoelectric resonators under finite biasing fields. A system of three dimensional equations is derived for initial and incremental fields on the body. Capability of the equations in numerical modelling of temperature-frequency and force-frequency effects in quartz crystal is demonstrated. The numerical results compare well with the data from experiments. These equations may be used in accurate modelling of piezoelectric devices subjected to thermo electro mechanical loads. تفاصيل المقالة -
حرية الوصول المقاله
183 - A Contact Problem of an Elastic Layer Compressed by Two Punches of Different Radii
K Seghir M Bendaoui R BenboutaThe elasticity mixed boundary values problems dealing with half-space contact are generally well resolved. A large number of these solutions are obtained by using the integral transformation method and methods based the integral equations. However, the problems of finit أکثرThe elasticity mixed boundary values problems dealing with half-space contact are generally well resolved. A large number of these solutions are obtained by using the integral transformation method and methods based the integral equations. However, the problems of finite layer thicknesses are less investigated, despite their practical interests. This study resolves a quasi-stationary problem of an isotropic elastic layer compressed by two rigid cylinders with flat ends. Hankel transformation and auxiliary functions with boundary conditions reduce the differential equation to an algebraic equations system, which can be solved in a numerical way. The contact efforts equations are established. From the general method, solutions of particular cases are also resolved. A particular case is studied, the contact zone pressure and stresses distribution curves are presented. تفاصيل المقالة -
حرية الوصول المقاله
184 - Generalized Thermoelastic Problem of a Thick Circular Plate Subjected to Axisymmetric Heat Supply
J.J Tripathi G.D Kedar K.C DeshmukhThe present work is aimed at analyzing the thermoelastic disturbances in a circular plate of finite thickness and infinite extent subjected to constant initial temperature and axisymmetric heat supply. Integral transform technique is used. Analytic solutions for tempera أکثرThe present work is aimed at analyzing the thermoelastic disturbances in a circular plate of finite thickness and infinite extent subjected to constant initial temperature and axisymmetric heat supply. Integral transform technique is used. Analytic solutions for temperature, displacement and stresses are derived within the context of unified system of equations in generalized thermoelasticity in the Laplace transform domain using potential functions. Inversion of Laplace transforms is done by employing a numerical scheme. Temperature, displacement and stresses developed in the thick circular plate are obtained and illustrated graphically for copper (pure) material. تفاصيل المقالة -
حرية الوصول المقاله
185 - Torsion in Microstructure Hollow Thick-Walled Circular Cylinder Made up of Orthotropic Material
S Yadav S SharmaIn this paper, a numerical solution has been developed for hollow circular cylinders made up of orthotropic material which is subjected to twist using micro polar theory. The effect of twisting moment and material internal length on hollow thick-walled circular cylinder أکثرIn this paper, a numerical solution has been developed for hollow circular cylinders made up of orthotropic material which is subjected to twist using micro polar theory. The effect of twisting moment and material internal length on hollow thick-walled circular cylinder made up of micro polar orthotropic material is investigated. Finite difference method has been used to exhibit the influence of shear moduli and material internal length on shear stresses and couple stresses. It is found that the effect of small characteristic length on shear stresses is negligible and couple stresses present its significance when characteristic length is large in solid particle. The behavior of couple stresses are nonlinear for large internal length while for small internal length couple stresses are linear in nature except near the free boundaries. Torsion in hollow cylinder made up of micro polar orthotropic play vital role in the presence of cracks and holes. Therefore, torsional analysis of hollow cylinder plays important role in the field of biomechanics. تفاصيل المقالة -
حرية الوصول المقاله
186 - Analytical and Numerical Modelling of the Axisymmetric Bending of Circular Sandwich Plates with the Nonlinear Elastic Core Material
A Kudin S Choporov Yu Tamurov M.A.V Al OmariHerein paper compares the analytical model with the FEM based numerical model of the axisymmetric bending of circular sandwich plates. Also, the paper describes equations of the circular symmetrical sandwich plates bending with isotropic face sheets and the nonlinear el أکثرHerein paper compares the analytical model with the FEM based numerical model of the axisymmetric bending of circular sandwich plates. Also, the paper describes equations of the circular symmetrical sandwich plates bending with isotropic face sheets and the nonlinear elastic core material. The method of constructing an analytical solution of nonlinear differential equations has been described. The perturbation method for differential equations with small parameters is used to represent nonlinear differential equations as a sequence of linear equations. Linear differential equations are reduced to Bessel’s equation. It is compared results of analytical model with results of other researches using two problems: 1) the problem of axisymmetric transverse bending of a circular sandwich plate, 2) the problem of axisymmetric transverse bending of an annular sandwich plate. The effect of accounting nonlinear elastic core material on the strain state of the sandwich plate is described. تفاصيل المقالة -
حرية الوصول المقاله
187 - Problem of Rayleigh Wave Propagation in Thermoelastic Diffusion
R Kumar V GuptaIn this work, the problem of Rayleigh wave propagation is considered in the context of the theory of thermoelastic diffusion. The formulation is applied to a homogeneous isotropic thermoelastic half space with mass diffusion at the stress free, isothermal, isoconcentrat أکثرIn this work, the problem of Rayleigh wave propagation is considered in the context of the theory of thermoelastic diffusion. The formulation is applied to a homogeneous isotropic thermoelastic half space with mass diffusion at the stress free, isothermal, isoconcentrated boundary. Using the potential functions and harmonic wave solution, three coupled dilatational waves and a shear wave is obtained. After developing mathematical formulation, the dispersion equation is obtained, which results to be complex and irrational. This equation is converted into a polynomial form of higher degree. The roots of this polynomial equation are verified for not satisfying the original dispersion equation and therefore are filtered out and the remaining roots are checked with the property of decay with depth. Phase velocity and attenuation coefficient of the Rayleigh wave are computed numerically and depicted graphically. Behavior of particle motion of these waves inside and at the surface of the thermoelastic medium with mass diffusion is studied. Some particular cases are also deduced from the present investigation. تفاصيل المقالة -
حرية الوصول المقاله
188 - Damping and Frequency Shift in Microscale Modified Couple Stress Thermoelastic Plate Resonators
S Devi R KumarIn this paper, the vibrations of thin plate in modified couple stress thermoelastic medium by using Kirchhoff- Love plate theory has been investigated. The governing equations of motion and heat conduction equation for Lord Shulman (L-S) [1] theory are written with the أکثرIn this paper, the vibrations of thin plate in modified couple stress thermoelastic medium by using Kirchhoff- Love plate theory has been investigated. The governing equations of motion and heat conduction equation for Lord Shulman (L-S) [1] theory are written with the help of Kirchhoff- Love plate theory. The thermoelastic damping of micro-beam resonators is analyzed by using the normal mode analysis. The solutions for the free vibrations of plates under clamped-simply supported (CS) and clamped-free (CF) conditions are obtained. The analytical expressions for thermoelastic damping of vibration and frequency shift are obtained for couple stress generalized thermoelastic and coupled thermoelastic plates. A computer algorithm has been constructed to obtain the numerical results. The thermoelastic damping and frequency shift with varying values of length and thickness are shown graphically in the absence and presence of couple stress for (i) clamped-simply supported, (ii) clamped-free boundary conditions. Some particular cases are also presented. تفاصيل المقالة -
حرية الوصول المقاله
189 - Shear Waves Through Non Planar Interface Between Anisotropic Inhomogeneous and Visco-Elastic Half-Spaces
B Prasad P Chandra Pal S KunduA problem of reflection and transmission of a plane shear wave incident at a corrugated interface between transversely isotropic inhomogeneous and visco-elastic half-spaces is investigated. Applying appropriate boundary conditions and using Rayleigh’s method of ap أکثرA problem of reflection and transmission of a plane shear wave incident at a corrugated interface between transversely isotropic inhomogeneous and visco-elastic half-spaces is investigated. Applying appropriate boundary conditions and using Rayleigh’s method of approximation expressions for reflection and transmission coefficients are obtained for the first and second order approximation of the corrugation. Further, closed form formulae of these coefficients are presented for a corrugated interface of periodic shape (cosine law interface). Numerical computations for this particular type of corrugated interface are performed and a number of graphs are plotted to illustrate the effect of different parameters of the both half-spaces on the reflection and transmission coefficients. It is found that these coefficients depend upon the amplitude of corrugation of the boundary, angle of incidence and frequency of the incident wave and are strongly influenced by the anisotropy, inhomogeneity and visco-elasticity of the half-spaces. Some special cases are also derived. تفاصيل المقالة -
حرية الوصول المقاله
190 - Nonlocal Bending Analysis of Bilayer Annular/Circular Nano Plates Based on First Order Shear Deformation Theory
Sh Dastjerdi M JabbarzadehIn this paper, nonlinear bending analysis of bilayer orthotropic annular/circular graphene sheets is studied based on the nonlocal elasticity theory. The equilibrium equations are derived in terms of generalized displacements and rotations considering the first-order Sh أکثرIn this paper, nonlinear bending analysis of bilayer orthotropic annular/circular graphene sheets is studied based on the nonlocal elasticity theory. The equilibrium equations are derived in terms of generalized displacements and rotations considering the first-order Shear deformation theory (FSDT). The nonlinear governing equations are solved using the differential quadrature method (DQM) which is a highly accurate numerical method and a new semi-analytical polynomial method (SAPM). The ordinary differential equations (ODE’s) are converted to the nonlinear algebraic equations applying DQM or SAPM. Then, the Newton–Raphson iterative scheme is applied. The obtained results of DQM and SAPM are compared. It is concluded that although, the SAPM’s formulation is considerably simple in comparison with DQM, however, the results of two methods are so close to each other. The results are validated with available researches. The effects of small scale parameter, the value of van der Waals interaction between the layers, different values of elastic foundation and loading, the comparison between the local and nonlocal deflections and linear to nonlinear analysis are investigated. تفاصيل المقالة -
حرية الوصول المقاله
191 - Elastic Analysis of Functionally Graded Variable Thickness Rotating Disk by Element Based Material Grading
A.K Thawait L Sondhi Sh Sanyal Sh BhowmickThe present study deals with the elastic analysis of concave thickness rotating disks made of functionally graded materials (FGMs).The analysis is carried out using element based gradation of material properties in radial direction over the discretized domain. The resul أکثرThe present study deals with the elastic analysis of concave thickness rotating disks made of functionally graded materials (FGMs).The analysis is carried out using element based gradation of material properties in radial direction over the discretized domain. The resulting deformation and stresses are evaluated for free-free boundary condition and the effect of grading index on the deformation and stresses is investigated and presented. The results obtained show that there is a significant reduction of stresses in FGM disks as compared to homogeneous disks and the disks modeled by power law FGM have better strength. تفاصيل المقالة -
حرية الوصول المقاله
192 - Elastic Wave Propagation at Imperfect Boundary of Micropolar Elastic Solid and Fluid Saturated Porous Solid Half-Space
V Kaliraman R.K PooniaThis paper deals with the reflection and transmission of elastic waves from imperfect interface separating a micropolar elastic solid half-space and a fluid saturated porous solid half-space. Longitudinal and transverse waves impinge obliquely at the interface. Amplitud أکثرThis paper deals with the reflection and transmission of elastic waves from imperfect interface separating a micropolar elastic solid half-space and a fluid saturated porous solid half-space. Longitudinal and transverse waves impinge obliquely at the interface. Amplitude ratios of various reflected and transmitted waves are obtained and computed numerically for a specific model and results obtained are depicted graphically with angle of incidence of incident waves. It is found that these amplitude ratios depend on angle of incidence of the incident wave, imperfect boundary and material properties of half-spaces. From the present study, a special case when fluid saturated porous half-space reduces to empty porous solid is also deduced and discussed graphically. تفاصيل المقالة -
حرية الوصول المقاله
193 - Time-Dependent Hygro-Thermal Creep Analysis of Pressurized FGM Rotating Thick Cylindrical Shells Subjected to Uniform Magnetic Field
A Bakhshizadeh M Zamani Nejad M Davoudi KashkoliTime-dependent creep analysis is presented for the calculation of stresses and displacements of axisymmetric thick-walled cylindrical pressure vessels made of functionally graded material (FGM). For the purpose of time-dependent stress analysis in an FGM pressure vessel أکثرTime-dependent creep analysis is presented for the calculation of stresses and displacements of axisymmetric thick-walled cylindrical pressure vessels made of functionally graded material (FGM). For the purpose of time-dependent stress analysis in an FGM pressure vessel, material creep behavior and the solutions of the stresses at a time equal to zero (i.e. the initial stress state) are needed. This corresponds to the solution of the problem considering linear elastic behavior of the material. Therefore, using equations of equilibrium, stress–strain and strain–displacement, a differential equation for displacement is obtained and subsequently the initial elastic stresses at a time equal to zero are calculated. Assuming that the Magneto-hygro-thermoelastic creep response of the material is governed by Norton’s law, using the rate form of constitutive differential equation, the displacement rate is obtained and then the stress rates are calculated. Once the stress rates are known, the stresses at any time are calculated iteratively. The analytical solution is obtained for the plane strain condition. The pressure, inner radius and outer radius are considered to be constant and the magnetic field is uniform. Material properties are considered as power law function of the radius of the cylinder and the poisson’s ratio as constant. Following this, profiles are plotted for different values of material exponent for the radial, circumferential and effective stresses as a function of radial direction and time. The in-homogeneity exponent have significant influence on the distributions of the creep stresses. تفاصيل المقالة -
حرية الوصول المقاله
194 - Vibration Analysis of Orthotropic Triangular Nanoplates Using Nonlocal Elasticity Theory and Galerkin Method
A.R Shahidi S.H Shahidi A Anjomshoae E Raeisi EstabraghIn this article, classical plate theory (CPT) is reformulated using the nonlocal differential constitutive relations of Eringen to develop an equivalent continuum model for orthotropic triangular nanoplates. The equations of motion are derived and the Galerkin’s a أکثرIn this article, classical plate theory (CPT) is reformulated using the nonlocal differential constitutive relations of Eringen to develop an equivalent continuum model for orthotropic triangular nanoplates. The equations of motion are derived and the Galerkin’s approach in conjunction with the area coordinates is used as a basis for the solution. Nonlocal theories are employed to bring out the effect of the small scale on natural frequencies of nano scaled plates. Effect of nonlocal parameter, lengths of the nanoplate, aspect ratio, mode number, material properties, boundary condition and in-plane loads on the natural frequencies are investigated. It is shown that the natural frequencies depend highly on the non-locality of the nanoplate, especially at the very small dimensions, higher mode numbers and stiffer edge condition. تفاصيل المقالة -
حرية الوصول المقاله
195 - Viscous Fluid Flow-Induced Nonlocal Nonlinear Vibration of Embedded DWBNNTs
A Ghorbanpour Arani Z Khoddami Maraghi R Kolahchi M MohammadimehrIn this article, electro-thermo nonlocal nonlinear vibration and instability of viscous-fluid-conveying double–walled boron nitride nanotubes (DWBNNTs) embedded on Pasternak foundation are investigated. The DWBNNT is simulated as a Timoshenko beam (TB) which inclu أکثرIn this article, electro-thermo nonlocal nonlinear vibration and instability of viscous-fluid-conveying double–walled boron nitride nanotubes (DWBNNTs) embedded on Pasternak foundation are investigated. The DWBNNT is simulated as a Timoshenko beam (TB) which includes rotary inertia and transverse shear deformation in the formulation. Considering electro-mechanical coupling, the nonlinear governing equations are derived using Hamilton’s principle and discretized based on the differential quadrature method (DQM). The lowest four frequencies are determined for clamped-clamped boundary condition. The effects of dimensionless small scale parameter, elastic medium coefficient, flow velocity, fluid viscosity and temperature change on the imaginary and real components of frequency are also taken into account. Results indicate that the electric potential increases with decreasing nonlocal parameter. It is also worth mentioning that decreasing nonlocal parameter and existence of Winkler and Pasternak foundation can enlarge the stability region of DWBNNT. تفاصيل المقالة -
حرية الوصول المقاله
196 - Analysis of Viscoelastic Functionally Graded Sandwich Plates with CNT Reinforced Composite Face Sheets on Viscoelastic Foundation
A Ghorbanpour Arani M Emdadi H Ashrafi M Mohammadimehr S Niknejad A.A Ghorbanpour Arani A HosseinpourIn this article, bending, buckling, and free vibration of viscoelastic sandwich plate with carbon nanotubes reinforced composite facesheets and an isotropic homogeneous core on viscoelastic foundation are presented using a new first order shear deformation theory. Accor أکثرIn this article, bending, buckling, and free vibration of viscoelastic sandwich plate with carbon nanotubes reinforced composite facesheets and an isotropic homogeneous core on viscoelastic foundation are presented using a new first order shear deformation theory. According to this theory, the number of unknown’s parameters and governing equations are reduced and also the using of shear correction factor is not necessary because the transverse shear stresses are directly computed from the transverse shear forces by using equilibrium equations. The governing equations obtained using Hamilton’s principle is solved for a rectangular viscoelastic sandwich plate. The effects of the main parameters on the vibration characteristics of the viscoelastic sandwich plates are also elucidated. The results show that the frequency significantly decreases with using foundation and increasing the viscoelastic structural damping coefficient as well as the damping coefficient of materials and foundation. تفاصيل المقالة -
حرية الوصول المقاله
197 - Quasi-Static Deformation of a Uniform Thermoelastic Half –Space Due to Seismic Sources and Heat Source
A.K Vashishth K RaniThis paper investigates the quasi-static plane deformation of an isotropic thermoelastic half-space due to buried seismic sources and heat source. Governing equations of thermo-elasticity are solved to obtain solutions for seismic sources in a thermoelastic half-space. أکثرThis paper investigates the quasi-static plane deformation of an isotropic thermoelastic half-space due to buried seismic sources and heat source. Governing equations of thermo-elasticity are solved to obtain solutions for seismic sources in a thermoelastic half-space. The general solutions are acquired with the aid of Laplace and Fourier transforms and with the use of boundary conditions. The case of dip-slip line dislocation is studied in detail along with line heat source. Analytical solutions for two limiting cases: adiabatic and isothermal, are obtained. The solutions for displacement, stresses and temperature in space-time domain are obtained by using a numerical inversion procedure. The accuracy of the proposed method is verified through a comparison of the results obtained with the existing solutions for elastic medium. In addition, numerical results for displacements, stresses and temperature function, induced by a vertical dip-slip dislocation and line heat source, are presented graphically to illustrate the effect of inclusion of thermal effect in simulation of the problem. تفاصيل المقالة -
حرية الوصول المقاله
198 - Mechanical Stresses in a Linear Plastic FGM Hollow Cylinder Due to Non-Axisymmetric Loads
M Shokouhfar M JabbariIn this paper, an analytical solution for computing the linear plastic stresses and critical pressure in a FGM hollow cylinder under the internal pressure due to non-Axisymmetric Loads is developed. It has been assumed that the modulus of elasticity was varying through أکثرIn this paper, an analytical solution for computing the linear plastic stresses and critical pressure in a FGM hollow cylinder under the internal pressure due to non-Axisymmetric Loads is developed. It has been assumed that the modulus of elasticity was varying through thickness of the FGM material according to a power law relationship. The Poisson's ratio was considered constant throughout the thickness. The general form of mechanical boundary conditions is considered on the inside surfaces. In the analysis presented here the effect of non-homogeneity in FGM cylinder was implemented by choosing a dimensionless parameter, named m, which could be assigned an arbitrary value affecting the stresses in the cylinder. Distribution of stresses in radial, circumferential and shear directions for FGM cylinders under the influence of internal pressure were obtained. Graphs of variations of stress versus radius of the cylinder were plotted. The direct method is used to solve the Navier equations. تفاصيل المقالة -
حرية الوصول المقاله
199 - Nonlocal Piezomagnetoelasticity Theory for Buckling Analysis of Piezoelectric/Magnetostrictive Nanobeams Including Surface Effects
A Ghorbanpour Arani M Abdollahian A.H RahmatiThis paper presents the surface piezomagnetoelasticity theory for size-dependent buckling analysis of an embedded piezoelectric/magnetostrictive nanobeam (PMNB). It is assumed that the subjected forces from the surrounding medium contain both normal and shear components أکثرThis paper presents the surface piezomagnetoelasticity theory for size-dependent buckling analysis of an embedded piezoelectric/magnetostrictive nanobeam (PMNB). It is assumed that the subjected forces from the surrounding medium contain both normal and shear components. Therefore, the surrounded elastic foundation is modeled by Pasternak foundation. The nonlocal piezomagnetoelasticity theory is applied so as to consider the small scale effects. Based on Timoshenko beam (TB) theory and using energy method and Hamilton’s principle the motion equations are obtained. By employing an analytical method, the critical magnetic, electrical and mechanical buckling loads of the nanobeam are yielded. Results are presented graphically to show the influences of small scale parameter, surrounding elastic medium, surface layers, and external electric and magnetic potentials on the buckling behaviors of PMNBs. Results delineate the significance of surface layers and external electric and magnetic potentials on the critical buckling loads of PMNBs. It is revealed that the critical magnetic, electrical and mechanical buckling loads decrease with increasing the small scale parameter. The results of this work is hoped to be of use in micro/nano electro mechanical systems (MEMS/NEMS) especially in designing and manufacturing electromagnetoelastic sensors and actuators. تفاصيل المقالة -
حرية الوصول المقاله
200 - Two-Dimensional Elasticity Solution for Arbitrarily Supported Axially Functionally Graded Beams
A Singh P KumariFirst time, an analytical two-dimensional (2D) elasticity solution for arbitrarily supported axially functionally graded (FG) beam is developed. Linear gradation of the material property along the axis of the beam is considered. Using the strain displacement and constit أکثرFirst time, an analytical two-dimensional (2D) elasticity solution for arbitrarily supported axially functionally graded (FG) beam is developed. Linear gradation of the material property along the axis of the beam is considered. Using the strain displacement and constitutive relations, governing partial differential equations (PDEs) is obtained by employing Ressiner mixed variational principle. Then PDEs are reduced to two set of ordinary differential equations (ODEs) by using recently developed extended Kantorovich method. The set of 4n ODEs along the z-direction has constant coefficients. But, the set of 4n nonhomogeneous ODEs along x-direction has variable coefficients which is solved using modified power series method. Efficacy and accuracy of the present methodology are verified thoroughly with existing literature and 2D finite element solution. Effect of axial gradation, boundary conditions and configuration lay-ups are investigated. It is found that axial gradation influence vary with boundary conditions. These benchmark results can be used for assessing 1D beam theories and further present formulation can be extended to develop solutions for 2D micro or Nanobeams. تفاصيل المقالة -
حرية الوصول المقاله
201 - Finite Difference Method for Biaxial and Uniaxial Buckling of Rectangular Silver Nanoplates Resting on Elastic Foundations in Thermal Environments Based on Surface Stress and Nonlocal Elasticity Theories
M karimi A.R ShahidiIn this article, surface stress and nonlocal effects on the biaxial and uniaxial buckling of rectangular silver nanoplates embedded in elastic media are investigated using finite difference method (FDM). The uniform temperature change is utilized to study thermal effect أکثرIn this article, surface stress and nonlocal effects on the biaxial and uniaxial buckling of rectangular silver nanoplates embedded in elastic media are investigated using finite difference method (FDM). The uniform temperature change is utilized to study thermal effect. The surface energy effects are taken into account using the Gurtin-Murdoch’s theory. Using the principle of virtual work, the governing equations considering small scale for both nanoplate bulk and surface are derived. The influence of important parameters including, the Winkler and shear elastic moduli, boundary conditions, in-plane biaxial and uniaxial loads, and width-to-length aspect ratio, on the surface stress effects are also studied. The finite difference method, uniaxial buckling, nonlocal effect for both nanoplate bulk and surface, silver material properties, and below-mentioned results are the novelty of this investigation. Results show that the effects of surface elastic modulus on the uniaxial buckling are more noticeable than that of biaxial buckling, but the influences of surface residual stress on the biaxial buckling are more pronounced than that of uniaxial buckling. تفاصيل المقالة -
حرية الوصول المقاله
202 - Dynamic Behavior of Anisotropic Protein Microtubules Immersed in Cytosol Via Cooper–Naghdi Thick Shell Theory
M.R Ghorbanpour Arani Z Khoddami Maraghi E HaghparastIn the present research, vibrational behavior of anisotropic protein microtubules (MTs) immersed in cytosol via Cooper–Naghdi shell model is investigated. MTs are hollow cylindrical structures in the eukaryotic cytoskeleton which surrounded by filament network. Th أکثرIn the present research, vibrational behavior of anisotropic protein microtubules (MTs) immersed in cytosol via Cooper–Naghdi shell model is investigated. MTs are hollow cylindrical structures in the eukaryotic cytoskeleton which surrounded by filament network. The temperature effect on vibration frequency is also taken into account by assuming temperature-dependent material properties for MTs. To enhance the accuracy of results, strain gradient theory is utilized and the motion equations are derived based on Hamilton’s principle. Effects of various parameters such as environmental conditions by considering the surface traction of cytosol, length scale, thickness and aspect ratio on vibration characteristics of anisotropic MTs are studied. Results indicate that vibrational behavior of anisotropic MTs is strongly dependent on longitudinal Young’s modulus and length scale parameters. The results of this investigation can be utilized in the ultrasonic examine of MT organization in medical applications particularly in the treatment of cancers. تفاصيل المقالة -
حرية الوصول المقاله
203 - Influence of Temperature Change on Modal Analysis of Rotary Functionally Graded Nano-beam in Thermal Environment
E Shahabinejad N Shafiei M GhadiriThe free vibration analysis of rotating functionally graded (FG) nano-beams under an in-plane thermal loading is provided for the first time in this paper. The formulation used is based on Euler-Bernoulli beam theory through Hamilton’s principle and the small scal أکثرThe free vibration analysis of rotating functionally graded (FG) nano-beams under an in-plane thermal loading is provided for the first time in this paper. The formulation used is based on Euler-Bernoulli beam theory through Hamilton’s principle and the small scale effect has been formulated using the Eringen elasticity theory. Then, they are solved by a generalized differential quadrature method (GDQM). It is supposed that, according to the power-law form (P-FGM), the thermal distribution is non-linear and material properties are dependent to temperature and are changing continuously through the thickness. Free vibration frequencies are obtained for two types of boundary conditions; cantilever and propped cantilever. The novelty of this work is related to vibration analysis of rotating FG nano-beam under different distributions of temperature with different boundary conditions using nonlocal Euler-Bernoulli beam theory. Presented theoretical results are validated by comparing the obtained results with literature. Numerical results are presented in both cantilever and propped cantilever nano-beams and the influences of the thermal, nonlocal small-scale, angular velocity, hub radius, FG index and higher modes number on the natural frequencies of the FG nano-beams are investigated in detail. تفاصيل المقالة -
حرية الوصول المقاله
204 - Biaxial Buckling Analysis of Symmetric Functionally Graded Metal Cored Plates Resting on Elastic Foundation under Various Edge Conditions Using Galerkin Method
M Rezaei S Ziaee S ShojaIn this paper, buckling behavior of symmetric functionally graded plates resting on elastic foundation is investigated and their critical buckling load in different conditions is calculated and compared. Plate governing equations are derived using the principle of minim أکثرIn this paper, buckling behavior of symmetric functionally graded plates resting on elastic foundation is investigated and their critical buckling load in different conditions is calculated and compared. Plate governing equations are derived using the principle of minimum potential energy. Afterwards, displacement field is solved using Galerkin method and the proposed process is examined through numerical examples. Effect of FGM power law index, plate aspect ratio, elastic foundation stiffness and metal core thickness on critical buckling load is investigated. The accuracy of this approach is verified by comparing its results to those obtained in another work, which is performed using Fourier series expansion. تفاصيل المقالة -
حرية الوصول المقاله
205 - Thermomechanical Interactions Due to Hall Current in Transversely Isotropic Thermoelastic with and Without Energy Dissipation with Two Temperatures and Rotation
R Kumar N Sharma P LataThe present paper is concerned with the investigation of disturbances in a homogeneous transversely isotropic thermoelastic rotating medium with two temperatures, in the presence of the combined effects of Hall currents and magnetic field due to thermomechanical sources أکثرThe present paper is concerned with the investigation of disturbances in a homogeneous transversely isotropic thermoelastic rotating medium with two temperatures, in the presence of the combined effects of Hall currents and magnetic field due to thermomechanical sources. The formulation is applied to the thermoelasticity theories developed by Green-Naghdi Theories of Type-II and Type-III. Laplace and Fourier transform technique is applied to solve the problem. As an application, the bounding surface is subjected to concentrated and distributed sources (mechanical and thermal sources). The analytical expressions of displacement, stress components, temperature change and current density components are obtained in the transformed domain. Numerical inversion technique has been applied to obtain the results in the physical domain. Numerical simulated results are depicted graphically to show a comparison of effect of Hall current on the two theories GN-II and GN-III on resulting quantities. Some special cases are also deduced from the present investigation. تفاصيل المقالة -
حرية الوصول المقاله
206 - Non-Linear Analysis of Asymmetrical Eccentrically Stiffened FGM Cylindrical Shells with Non-Linear Elastic Foundation
A.R Shaterzadeh K ForoutanIn this paper, semi-analytical method for asymmetrical eccentrically stiffened FGM cylindrical shells under external pressure and surrounded by a linear and non-linear elastic foundation is presented. The proposed linear model is based on two parameter elastic foundatio أکثرIn this paper, semi-analytical method for asymmetrical eccentrically stiffened FGM cylindrical shells under external pressure and surrounded by a linear and non-linear elastic foundation is presented. The proposed linear model is based on two parameter elastic foundation Winkler and Pasternak. According to the von Karman nonlinear equations and the classical plate theory of shells, strain-displacement relations are obtained. The smeared stiffeners technique and Galerkin method, used for solving nonlinear problem. To finding the nonlinear dynamic response of fourth order Runge-Kutta method is used. The effect of parameters asymmetrical eccentrically stiffened on the nonlinear dynamic buckling response of FGM cylindrical shells have been investigated. تفاصيل المقالة -
حرية الوصول المقاله
207 - Non-Local Thermo-Elastic Buckling Analysis of Multi-Layer Annular/Circular Nano-Plates Based on First and Third Order Shear Deformation Theories Using DQ Method
Sh Dastjerdi M JabbarzadehIn present study, thermo-elastic buckling analysis of multi-layer orthotropic annular/circular graphene sheets is investigated based on Eringen’s theory. The moderately thick and also thick nano-plates are considered. Using the non-local first and third order shea أکثرIn present study, thermo-elastic buckling analysis of multi-layer orthotropic annular/circular graphene sheets is investigated based on Eringen’s theory. The moderately thick and also thick nano-plates are considered. Using the non-local first and third order shear deformation theories, the governing equations are derived. The van der Waals interaction between the layers is simulated for multi-layer sheets. The stability governing equations are obtained according to the adjacent equilibrium estate method. The constitutive equations are solved by applying the differential quadrature method (DQM). Applying the differential quadrature method, the ordinary differential equations are transformed to algebraic equations. Then, the critical temperature is obtained. Since there is not any research in thermo-elastic buckling analysis of multi-layer graphene sheets, the results are validated with available single layer articles. The effects of non-local parameter, the values of van der Waals interaction between the layers, third to first order shear deformation theory analyses, non-local to local analyses, different values of Winkler and Pasternak elastic foundation and analysis of bi-layer and triple layer sheets are investigated. It is concluded that the critical temperature increases and tends to a constant value along the rise of van der Waals interaction between the layers. تفاصيل المقالة -
حرية الوصول المقاله
208 - An Investigation of Stress and Deformation States of Rotating Thick Truncated Conical Shells of Functionally Graded Material
A Thawait L Sondhi Sh Bhowmick Sh SanyalThe present study aims at investigating stress and deformation behavior of rotating thick truncated conical shells subjected to variable internal pressure. Material prpperties of the shells are graded along the axial direction by Mori-tanaka scheme, which is achieved by أکثرThe present study aims at investigating stress and deformation behavior of rotating thick truncated conical shells subjected to variable internal pressure. Material prpperties of the shells are graded along the axial direction by Mori-tanaka scheme, which is achieved by elemental gradation of the properties.Governing equations are derived using principle of stsionary total potential (PSTP) and shells are subjected to clamped- clamped boundary conditions. Aluminum-zirconia, metal-ceramic and ceramic-metal FGM is considered and effects of grading index of material properties and pressure distribution are analyzed. Distribution of Radial displacement and circumferential stress in both radial and axial direction is presented. Further a comparison of behaviors of different FGM shells and homogeneous shells are made which shows, a significant reduction in stresses and deformations of FGM shells as compared to homogeneous shell. FGM shell having value of grading parameter n = 2 is most suitable for the purpose of rotating conical shells having variable pressure distribution as compared to homogeneous shell and shell having other values of grading parameter n. تفاصيل المقالة -
حرية الوصول المقاله
209 - A Kurganov-Tadmor numerical method for option pricing under the constant elasticity of variance model
Sakineh Ghiasi Nouredin ParandinThe primary goal of option pricing theory is to calculate the probability that an option will be exercised at expiration and assign a dollar value to it. Options pricing theory also derives various risk factors or sensitivities based on those inputs, since market condit أکثرThe primary goal of option pricing theory is to calculate the probability that an option will be exercised at expiration and assign a dollar value to it. Options pricing theory also derives various risk factors or sensitivities based on those inputs, since market conditions are constantly changing, these factors provide traders with a means of determining how sensitive a specific trade is to price fluctuations, volatility fluctuations, and the passage of time. In this study, we derive a new exact solution for pricing European options using Kurganov-Tadmor when the underlying process follows the constant elasticity of variance model. This method was successfully applied to nonlinear convection-diffusion equations by Kurganov and Tadmor. Also, we provide computational results showing the performance of the method for European option pricing problems. The results showed that the proposed method is convenient to calculate the option price for K=3,β=(-3)/4,and N=200. تفاصيل المقالة -
حرية الوصول المقاله
210 - Developing a Measurement Model for the Sensitivity Analysis of Asset Returns with Regard to Beta Index of Exchange Rate in the Context of the Modified Capital Asset Pricing Model
Reza Alizadeh Farhad Dehdar Mohammadreza AbdoliWith increasing trade among different countries The exchange rate fluctuations, consumption, inflation, and market portfolios are considered as major risk factors in financial markets. Hence this study aimed to examine the relationship between the exchange rate fluctuat أکثرWith increasing trade among different countries The exchange rate fluctuations, consumption, inflation, and market portfolios are considered as major risk factors in financial markets. Hence this study aimed to examine the relationship between the exchange rate fluctuations and asset returns within a theoretical and empirical model, i.e. Consumption-based Capital Asset Pricing Model (CCAPM). To this end, a basic CCAPM was extended and imported consumables were included in Epstein and Zin’s recursive utility function. The research sample encompassed eight portfolios and monthly data from 2003 to 2014. The pricing model parameters were estimated using Euler's equations and Hansen and Singleton’s generalized method of moments (GMM). An estimation of the parameters of Euler's equations indicates the risk aversion and tolerance of economic factors, low elasticity of substitution for domestic consumables and imported consumables, and high elasticity of intertemporal substitution. In the next step, using Euler’s linearized equations as asset pricing model and Fama and Macbeth's two-step regression method, the effects of exchange rate risk premium, inflation, market efficiency, and consumption growth on return premium on assets were investigated. The results indicated the positive impact of the exchange rate risk premium, inflation, and market returns on the return premium on assets. تفاصيل المقالة -
حرية الوصول المقاله
211 - An Algorithm for Modeling and Interpretation of Seismoelectric Data
Ehsan Golmakani Torghabeh Mohammad Ebrahimi Dabbagh Hooman LatifiGenerally speaking, seismoelectric modeling is a prospecting method based on seismic and electromagnetic waves, in which waves generated by a seismic source at the boundary of the two environments generate a relative fluid-solid motion formed as a result of antagonism b أکثرGenerally speaking, seismoelectric modeling is a prospecting method based on seismic and electromagnetic waves, in which waves generated by a seismic source at the boundary of the two environments generate a relative fluid-solid motion formed as a result of antagonism between the elastic properties of the environment with the saturated fluid. This research has as its objective, a study of the effect of an electric field due to DC current on the propagation of seismic waves by pseudo spectral time domain method, or the more general concept of seismoelectric coupling effect. In this research, poroelastic equations were used for seismic waves and Maxwell’s equations for lectromagnetic waves. Additionally, the seismoelectric effect or charge density, electrical conductivity, dielectric permittivity function, fluid viscosity and zeta potential were determined. DC electric field variations were compared with results of a physical experiment conducted in a modeled environment. The results revealed that DC electric significantly affected the propagation of elastic energy through seismoelectric coupling in a wide range of seismic frequency widths. Additionally, the boundaries of the substrata were specified using the horizontal component of the electric field of the magnetic wave تفاصيل المقالة -
حرية الوصول المقاله
212 - تحلیل سازه‌ای و شبیه‌سازی عددی تیر کامپوزیت تحت بار متحرک نوسانی بر روی بستر ویسکوالاستیک پسترنک
محمد جواد رضوانی روح الله رضاییدر این مقاله، پاسخ دینامیکی تیر تیموشنکو با طول بینهایت تحت اثر بار متحرک نوسانی با استفاده از تئوری مرتبه اول برشی مطالعه می‌شود. تیر مورد نظر از جنس ماده مرکب ساخته شده و .روی بستر ویسکوالاستیک تعمیم یافته پسترنک قرار دارد. خصوصیات مکانیکی تیر در جهت ضخامت تغییر می‌کن أکثردر این مقاله، پاسخ دینامیکی تیر تیموشنکو با طول بینهایت تحت اثر بار متحرک نوسانی با استفاده از تئوری مرتبه اول برشی مطالعه می‌شود. تیر مورد نظر از جنس ماده مرکب ساخته شده و .روی بستر ویسکوالاستیک تعمیم یافته پسترنک قرار دارد. خصوصیات مکانیکی تیر در جهت ضخامت تغییر میکند ولی در جهت محور تیر ثابت فرض می‌شود. ابتدا با توجه به لایه‌گذاری ضربدری میدان جابجایی مناسب انتخاب می‌شود. سپس توسط اصل مینیمم کل انرژی پتانسیل معادلات دیفرانسیل حرکت استخراج گشته و با اعمال تبدیل فوریه مختلط نامتناهی حل می‌گردند. در این مطالعه، با استفاده از شبیه‌سازی عددی اثر پارامترهایی مختلف از قبیل سرعت بار متحرک، فرکانس بار متحرک، سفتی قائم بستر و ضریب ویسکوزیته بستر بر روی خیز تیر، نیروی برش و تنش برحسب فاصله از بار متحرک رسم شده است. نتایج نشان دادند که با افزایش سفتی قائم بستر، ضریب ویسکوزیته لایه برشی بستر و فرکانس بار متحرک باعث کاهش خیز، نیروی برش و تنش خمشی تیر می‌شود. همچنین، نتایج حاصل از تئوری مرتبه اول برشی با نتایج شبیه سازی عددی مقایسه شده و تطابق خوبی حاصل شده است. بنابراین شبیه سازی عددی می تواند پاسخ دینامیکی تیر کامپوزیت تحت بار متحرک را به خوبی بدست آورد. تفاصيل المقالة -
حرية الوصول المقاله
213 - توسعه مدل آیروالاستیسیته پره کامپوزیتی و تحلیل اثر چرخش و افزایش طول بر فرکانس‌های طبیعی
رضا اثباتی لواسانی شاهرخ شمسدر این پژوهش معادلات آیروالاستیسیته خطی پره توربین بادی با روش گسسته سازی المان محدود جهت درنظر گرفتن اثر چرخش و افزایش طول بر فرکانس‌های طبیعی استخراج شده است. پره یک تیر یکسر گیردار اویلر-برنولی کامپوزیتی در نظر گرفته شده و با روش المان محدود مدل شده است. با بکارگیری أکثردر این پژوهش معادلات آیروالاستیسیته خطی پره توربین بادی با روش گسسته سازی المان محدود جهت درنظر گرفتن اثر چرخش و افزایش طول بر فرکانس‌های طبیعی استخراج شده است. پره یک تیر یکسر گیردار اویلر-برنولی کامپوزیتی در نظر گرفته شده و با روش المان محدود مدل شده است. با بکارگیری روش همیلتونین معادلات حرکت را بدست آمده است. ماتریس‌های المان محدود با تعیین جابجایی گره‌ها و فرض رابطه خطی در جابجایی محوری و تابع هرمیشن در جهات عرضی و پیچشی محاسبه می‌شوند. اعتبار سنجی معادلات به صورت عددی بر روی پره با شبیه سازی سیستم معادلات و بررسی فرکانس‌های طبیعی و شکل مدها انجام شده است. همچنین اثر افزایش طول پره و چرخش پره در پره کوتاه و بلند کامپوزیتی بررسی شده است. بررسی فرکانس‌های طبیعی نشان میدهد فرکانس‌های اول و دوم پره‌های بلند تحت تاثیر افزایش طول و چرخش هستند. اما در فرکانس‌های بالا و همچنین در پره کوتاه اثر افزایش طول و چرخش کمتر از یک درصد است. تفاصيل المقالة -
حرية الوصول المقاله
214 - آنالیز ارتعاش آزاد نانولوله‌های ویسکوالاستیک تحت میدان مغناطیسی طولی بر اساس گرادیان کرنش غیرموضعی مدل تیر تیموشنکو
پرویز قزوینیاندر این مقاله ارتعاش آزاد نانولوله‌های ویسکوالاستیک تحت میدان مغناطیسی طولی مورد بررسی قرار گرفته است. معادله حاکم با استفاده از مدل تیر تیموشنکو و مدل کلوین-ویت بر اساس تئوری گرادیان کرنش غیرموضعی فرمول‌بندی شده است. در رویه آنالیز از روش تربیع دیفرانسیلی تطبیقی موضعی ( أکثردر این مقاله ارتعاش آزاد نانولوله‌های ویسکوالاستیک تحت میدان مغناطیسی طولی مورد بررسی قرار گرفته است. معادله حاکم با استفاده از مدل تیر تیموشنکو و مدل کلوین-ویت بر اساس تئوری گرادیان کرنش غیرموضعی فرمول‌بندی شده است. در رویه آنالیز از روش تربیع دیفرانسیلی تطبیقی موضعی (LADQM) استفاده شده است. همچنین اثر پارامترهای غیرموضعی، ضریب استهلاک سازه‌ای، پارامتر مقیاس طول ماده و میدان مغناطیسی طولی بر فرکانس‌های طبیعی سیستم مورد بررسی قرار گرفته است. ممکن است نتایج این تحقیق برای درک کاربرد بالقوه نانولوله‌ها در سیستم نانو الکترومکانیکی مفید باشد. تفاصيل المقالة -
حرية الوصول المقاله
215 - تحلیل دینامیکی تیر تیموشنکو از جنس ماده مرکب روی بستر ویسکوالاستیک تحت تاثیر بار متمرکز متحرک و نیروی محوری
محمدجواد رضوانی محمدحسین کارگرنویندر این مقاله، تحلیل دینامیکی تیر تیموشنکو از جنس ماده مرکب روی بستر ویسکو الاستیک تعمیم یافته پسترنک تحت اثر بار متمرکز متحرک و نیروی محوری از دیدگاه تئوری مرتبه اول برشی مطالعه شده است. اصولاً تیرهای تحت نیروی محوری ستون نامیده می‌شوند که برای از بین بردن اثر مرزی تیر أکثردر این مقاله، تحلیل دینامیکی تیر تیموشنکو از جنس ماده مرکب روی بستر ویسکو الاستیک تعمیم یافته پسترنک تحت اثر بار متمرکز متحرک و نیروی محوری از دیدگاه تئوری مرتبه اول برشی مطالعه شده است. اصولاً تیرهای تحت نیروی محوری ستون نامیده می‌شوند که برای از بین بردن اثر مرزی تیر متناهی، فرض می‌شود که تیر تا بینهایت گسترده شده باشد. سرعت حرکت بار و خصوصیات هندسی و مکانیکی تیر در طول آن ثابت می‌باشد. بستر در نظر گرفته شده شامل سه عامل استهلاک اعم از میرایی قائم، میرایی دورانی و ویسکوزیته لایه برشی و دو عامل سفتی شامل سفتی قائم و دورانی می‌باشد. با استفاده از نرم‌افزارMathematica روند تحلیل در قالب یک برنامه کامپیوتری درآمده و نتایج به صورت نمودار‌های خیز، نیروی برشی و تنش برحسب فاصله از بار متحرک و تغییر پارامترهای ذکر شده در فوق رسم گردیده‌اند. نتایج حاصل از تحلیل، با نتایج موجود در دیگر مراجع مقایسه شده است. تفاصيل المقالة -
حرية الوصول المقاله
216 - Optimization of the Ductile Properties of an Arc Welded Plate Based on the Yield Strength, Elongation and Modulus of Elasticity.
Samuel Sada Joseph AcheboAs a means of controlling the setback associated with the ductile properties of the welded joint, the optimal ductile properties of a mild steel weld were studied based on empirical data generated using the metal inert gas (MIG) welding process with specific references أکثرAs a means of controlling the setback associated with the ductile properties of the welded joint, the optimal ductile properties of a mild steel weld were studied based on empirical data generated using the metal inert gas (MIG) welding process with specific references to the yield strength, percentage elongation, poisson ratio and modulus of elasticity using the Response Surface Methodology (RSM) and Genetic Algorithm (GA). The results judging from the remarkable quality of the ductility of the weld reveals the adequacy of the yield strength, poisson ratio, and percentage elongation as key determinant in ascertaining the ductility of a weld as against the tensile strength which have been widely used in previous studies. Further analysis to determine the optimal ductile properties using the optimization techniques generated two different results which were further compared by means of a confirmatory test. The GA results recorded a more accurate optimal responses compared to the RSM having a yield strength of 270.28N/mm2, 31.01% percentage elongation, 0.359 poisson ratio, and modulus of elasticity of 1660.3N/mm2. The results not withstanding their differences reveals that manufacturers can obtain the optimal ductile weld properties using the GA and RSM techniques if the right combination of process parameters is made. تفاصيل المقالة -
حرية الوصول المقاله
217 - Examining the Mixing Plan and the Results of the Plastic Concrete
Abolfazl Ostovarzijerdi Akbar Ghanbari Mohammad KarkonIn order to control seepage from the dam, various methods are used to reduce water seepage. One of the methods of reducing the permeability of the water according to its material is building cut-off walls and filling them with plastic concrete materials. In this study, أکثرIn order to control seepage from the dam, various methods are used to reduce water seepage. One of the methods of reducing the permeability of the water according to its material is building cut-off walls and filling them with plastic concrete materials. In this study, it has been tried to study the mixing plan of the plastic concrete in the main body of the Nargesi dam’s cutoff wall and to determine the results of compressive strength and elasticity modulus of 108 panels of cut-off wall in different ages in this project. Due to the individual concreting of each panel from the cutoff wall, the results of the plastic concrete panels at runtime are somewhat different. Due to the sensitivity of the plastic concrete to the dispersion of the results, considering that the cutoff wall should have a seamless function as well as the sensitivity of the concrete over time, it seems necessary to address this issue in an operational project. The results indicate that the growth rate of elastic modulus in a period of time is less than the growth rate of the compressive strength, and in other words, the plasticity of the concrete is changed less over time. تفاصيل المقالة -
حرية الوصول المقاله
218 - Performance Evaluation of Viscoelastic and Friction Passive Damping System in Steel Structures
Mohammad Taghi Kazemia Hosein HoseiniAdditional dampers are employed in order to decrease the dynamic response of structure against the earthquake and wind loading recently. In this study, two types of systems related to waste of inactive energy, i.e. frictional damper which is categorized in dampers depen أکثرAdditional dampers are employed in order to decrease the dynamic response of structure against the earthquake and wind loading recently. In this study, two types of systems related to waste of inactive energy, i.e. frictional damper which is categorized in dampers dependent on movement and viscoelastic damper which is categorized in dampers dependent on velocity, in making steel structures resistant are investigated and evaluated. Results of structures with dampers (viscoelastic damper, friction damper and combination of both dampers) were compared with the results of structures without damper. Increasing trend in dissipating energy was observed. Then, the behavior of these dampers in frames of 4, 8 and 12 stories was studied by modeling the damper directly. The analyses were conducted via nonlinear time history technique and by using earthquake records (near fault and far fault) scaled with peak acceleration and SAP 2000 14.2.2 software. The results indicate the appropriate function of the selected dampers in controlling and decreasing the seismic responses of the structure. Given that in frictional dampers the maximum force created in the damper is specified, the use of this damper in resistance building of structures is very effective especially by considering the limitation of structure capacity. تفاصيل المقالة -
حرية الوصول المقاله
219 - Numerical Investigation of Subgrade Reaction Coefficient in Sand Soils of Bandar Abbas City
Adel Asakereh Masood MossafaThe soil-foundation interaction is one of the most important issues in geotechnical engineering that deals with studying the soil behavior subjected to the side loading. Winkler’s model is the first and simplest method for consideration of the soil-foundation inte أکثرThe soil-foundation interaction is one of the most important issues in geotechnical engineering that deals with studying the soil behavior subjected to the side loading. Winkler’s model is the first and simplest method for consideration of the soil-foundation interaction. It is vitally important to determine the coefficient of subgrade reaction of the soil. Since several methods have been provided to estimate the coefficient of subgrade reaction up to now, this research is conducted to choose a ground characteristic in Bandar Abbas (IRAN). To do so, the obtained results from the proposed experimental formulas are compared with corresponding values of the behavioral models to determine the coefficient of subgrade reaction. In addition finite element analysis is performed using Plaxis software. The result of this paper shows that the finite element method is more compatible than Biot's method. Results also showed an increasing footing diameter which leads to the decrease of the Ks. This fact is because of an increasing load area which concluded to the increasing of the settlement. It is found that with increasing each of the strength parameters of the soil ( ) can be expected an effect on increasing the subgrade reaction; although this increase depends on footing diameter. Also, in sand soils, the cohesion of the soil is more effective on the increase of the subgrade reaction coefficient than the internal friction angle. تفاصيل المقالة -
حرية الوصول المقاله
220 - The effect of discrete lateral and torsional bracings stiffness on the elastic lateral-torsional buckling of mono-symmetric I beam, under the concentrated moment
E. Mohammadi J. Asgari Marnani S. Tavousi M.S. RohanimaneshWhen the out-of-plane stiffness of a beam is remarkably lower than the in-plane stiffness, the lateral-torsional buckling occurs. In this study, the behavior of mono-symmetric I-beams with discrete torsional and lateral bracings under the concentrated moment is investig أکثرWhen the out-of-plane stiffness of a beam is remarkably lower than the in-plane stiffness, the lateral-torsional buckling occurs. In this study, the behavior of mono-symmetric I-beams with discrete torsional and lateral bracings under the concentrated moment is investigated using the finite element analyses. Then, based on the numerical analyses, equation for the stiffness requirement is proposed. The results show that the location and the type of the bracing have an important role on the stiffness requirement and buckling strength. تفاصيل المقالة -
حرية الوصول المقاله
221 - Investigation of Stress-Strain Behavior of Plastic Concrete Using Monotonic Triaxial Compression Tests
y. Pashang pisheh seyed majddin Mir mohammad hosseinibIn this paper, the mechanical behavior of plastic concrete being used in the cut-off walls of earth dams has been studied. To do the task, triaxial compression tests on the specimens in various ages and mix designs under different confining pressures have been done and أکثرIn this paper, the mechanical behavior of plastic concrete being used in the cut-off walls of earth dams has been studied. To do the task, triaxial compression tests on the specimens in various ages and mix designs under different confining pressures have been done and the stress-strain behavior of such materials and their strength parameter changes has been experimentally investigated. It has been observed that increasing the confining pressures applied on the specimens causes the material behavior to be alike the more ductile materials and the compressive strength increases considerably as well. Moreover, a parametric study has been carried out to investigate the influence of essential parameters affecting the shear strength parameters of these materials. According to the research, increasing the coarse to fine aggregates ratio leads to the increase of compressive strength of the specimens as well as the increase of the cohesion and internal friction angle of the materials. Furthermore, the bentonite content decrease and the cement factor increase results in an increase of the cohesion parameter of plastic concretes and decrease of the internal friction angle of such materials. تفاصيل المقالة -
حرية الوصول المقاله
222 - Investigation of Failure Mechanism in Earth Dam upon Triggered Liquefaction
Farzad PeymanThe behavior of the earth-dam body as a soil structure made of cohesive soil in the core and non-cohesive soil as the core supports, including water interaction upstream through earthquake upon multi-line constitutive equations, is the aim of this paper. A multi-plane m أکثرThe behavior of the earth-dam body as a soil structure made of cohesive soil in the core and non-cohesive soil as the core supports, including water interaction upstream through earthquake upon multi-line constitutive equations, is the aim of this paper. A multi-plane mechanism-based approach is successfully employed for assigning post-liquefaction displacement of earth-dam structures. This approach is derived from total stress procedures with two major advantages:1) the triggering and post-liquefaction responses have been multi-lined into one analysis.2) the modeling of post-liquefaction element behavior is greatly improved.To sum up, a multi-plane-based framework is employed. The strength effects on integrated sampling planes and the resultant of this simulated multi-lined behavior are implemented for each finite element gauss point. This multi-plane-based model can also predict the effects of induced and inherent anisotropy plus the rotation of principal stress/strain axes through the plastic behavior of both cohesive and non-cohesive soils.The approach is presented through the simulation of the case history as the response of the lower San Fernando dam to the 1971 San Fernando earthquake. The magnitude and pattern of the predicted displacements are shown to be in good agreement with the measured values تفاصيل المقالة -
حرية الوصول المقاله
223 - Elastic characterization of porous bone by ultrasonic method through Lamb waves
lahcen Mountassir Touriya Bassidi Hassan NounahThe object of this research is to characterize the porous bones by an ultrasonic method using Lamb waves. In recent years, the characterization of such materials has attracted many authors and takes a perfect place in the field of medicine. It requires the development o أکثرThe object of this research is to characterize the porous bones by an ultrasonic method using Lamb waves. In recent years, the characterization of such materials has attracted many authors and takes a perfect place in the field of medicine. It requires the development of more efficient technology for getting the necessary quality and security. This paper aims to exploits the dispersion curves of the Lamb wave, as a new originate alternative, to characterize the porous bone. The method used in this work is modeled using the Schoch theory for the measurement of the ultrasonic parameters, namely the longitudinal and transversal velocities, and densities, then we deduce the mechanical properties of samples with different porosity in a theoretical way. The theoretical results were compared with experimental data, and it is found that the predicted values were of the same order of measurement as experimental measurements. The correlation coefficient between the experimental ultrasound velocities and the theoretical velocities predicted by Schoch theory was R=0.96. تفاصيل المقالة -
حرية الوصول المقاله
224 - A Study on the Quasi-static Compression Behavior of 5056 Aluminum Alloy Foams
Sadegh Soltani Hamed Deilami Azodi Seyed Hossein ElahiIn this paper, 5056 aluminum alloy foams with different percentages of calcium carbonate as foaming agents have been produced, and the physical and mechanical properties of the foams have been studied. Quasi-static compression tests have been carried out to determine th أکثرIn this paper, 5056 aluminum alloy foams with different percentages of calcium carbonate as foaming agents have been produced, and the physical and mechanical properties of the foams have been studied. Quasi-static compression tests have been carried out to determine the mechanical properties of foamed material. The effects of the amount of calcium carbonate on the size of the pores, the minimum thickness of the walls, density, compressive strength and energy absorption capacity of foams have been investigated. The uniform structure of the pores has been observed in foam specimens with 1.5, 1.8 and 2.1 wt% CaCO3. Increasing the amount of CaCO3 foaming agent from 1.5% to 2.1% has increased the average size of the pores by more than 180% and reduced the thickness of cell walls by 90%. So, the density and the relative density of the aluminum foams have been reduced by 28.6%. The results also show that increasing the amount of CaCO3 foaming agent decreases compressive strength, the absorbed energy and the elastic modulus of 5056 aluminum foams. By increasing the amount of foaming agent from 1.5% to 2.1%, the elastic modulus has reduced by about 16%, and a decrease of 21% has been seen in the energy absorbed by the foam at the strain of 0.4. تفاصيل المقالة -
حرية الوصول المقاله
225 - Molecular Dynamics Investigation of The Elastic Constants and Moduli of Single Walled Carbon Nanotubes
Mohammad Mahdi Zaeri Saeed Ziaei-RadDetermination of the mechanical properties of carbon nanotubes is an essential step in their applications from macroscopic composites to nano-electro-mechanical systems. In this paper we report the results of a series of molecular dynamics simulations carried out to pre أکثرDetermination of the mechanical properties of carbon nanotubes is an essential step in their applications from macroscopic composites to nano-electro-mechanical systems. In this paper we report the results of a series of molecular dynamics simulations carried out to predict the elastic constants, i.e. the elements of the stiffness tensor, and the elastic moduli, namely the Young’s and shear moduli, of various single walled carbon nanotubes. Poisson’s ratios were also calculated. Three different methods were used to run the simulations: applying a predetermined strain and reading the resulted stress, applying forces and constraints to the end atoms and calculating the moduli by assuming an equivalent continuum tube, and lastly applying a predetermined stress and reading the consequent deformation. In each case, the effect of nanotube chirality and diameter was studied. In addition, loading conditions were altered in each method to study the effect of nonlinearity of interatomic interactions. The result of the three methods are compared, with each other as well as with the literature, and discussed to obtain reasonable concluding remarks. تفاصيل المقالة -
حرية الوصول المقاله
226 - ارزیابی توان تعمیق سرمایه و اثر کشش جانشینی عوامل تولید بر ظرفیت اشتغال‌زایی صنایع کارخانه‌ای ایران
حمید شیرازی محمد شریف کریمی علی فلاحتیهدف مقاله، بررسی تأثیر تعمیق سرمایه و کشش جانشینی عوامل تولید بر ظرفیت اشتغال‌زایی بخش صنایع کارخانه‌ای ایران طی دوره سالیانه 1368-1398 با استفاده از تکنیک خودرگرسیونی با وقفه‌های گسترده (ARDL) بود. نتایج حاکی از تأثیر معنادار معکوس آنی و مستقی أکثرهدف مقاله، بررسی تأثیر تعمیق سرمایه و کشش جانشینی عوامل تولید بر ظرفیت اشتغال‌زایی بخش صنایع کارخانه‌ای ایران طی دوره سالیانه 1368-1398 با استفاده از تکنیک خودرگرسیونی با وقفه‌های گسترده (ARDL) بود. نتایج حاکی از تأثیر معنادار معکوس آنی و مستقیم تأخیری عامل تعمیق سرمایه در هر‌دو دوره و نیز تأثیر معنادار مستقیم تأخیری عامل کشش جانشینی عوامل تولید در دوره کوتاه‌مدت و تأثیر معنادار معکوس تأخیری تغییرات کشش جانشینی عوامل در بلندمدت بر ظرفیت اشتغال‌زایی بخش یادشده طی دوره یادشده است. همچنین، طبق مدل تصحیح خطا (ECM)، الگوی پویای کوتاه‌مدت ظرفیت اشتغال‌زایی بخش صنایع کارخانه‌ای به‌سمت الگوی تعادل بلندمدت، هم‌گرایی و گرایش دارد. براساس نتایج، انتخاب تکنولوژی سازگار در بخش صنایع کارخانه‌ای (صنعت ساخت) ایران در راستای امکان جانشینی آسان عوامل و تعمیق سرمایه، بهره‌گیری بیشتر از تجارب بین‌المللی، بومی‌سازی دانش فنی و انتقال فن‌آوری‌های نوین از طریق راهبرد تعمیق سرمایه درجهت افزایش سطح رقابت‌پذیری محصولات بخش صنعت ساخت و ارتقای توان استفاده از دانش فنی در تولید محصولات صنعتی و انتخاب مدبرانه راهبرد تعمیق سرمایه درجهت افزایش و یا حداقل، حفظ وضع موجود اشتغال بخش صنایع کارخانه‌ای پیشنهاد می‌گردد. تفاصيل المقالة -
حرية الوصول المقاله
227 - تحلیل سیستماتیک اثر تغییرات مخارج واقعی خانوارهای شهری بر سهم خودرو سواری نو در سبد مصرفی خانوار
پروانه سلاطین آزادمهر کهرام مریم جوادیدر این مقاله با به کارگیری سیستم تقاضای تقریباً ایده‌ال، تاثیر متغیرهای موثر بر سهم خودروسواری نو در سبد مصرفی‌خانوار‌های شهری در دوره زمانی 1386-1370 مورد بررسی و تجزیه وتحلیل قرار گرفته است. نتایج حاصل ازبرآورد به روش رگرسیون‌های به ظاهر نامرتبط نشان میدهد که تغییر أکثردر این مقاله با به کارگیری سیستم تقاضای تقریباً ایده‌ال، تاثیر متغیرهای موثر بر سهم خودروسواری نو در سبد مصرفی‌خانوار‌های شهری در دوره زمانی 1386-1370 مورد بررسی و تجزیه وتحلیل قرار گرفته است. نتایج حاصل ازبرآورد به روش رگرسیون‌های به ظاهر نامرتبط نشان میدهد که تغییر مخارج واقعی خانوار، بعد خانوار وتغییرات قیمتی سایر کالاها این سهم را تحت تاثیر قرار داده است. بررسی نتایج حاصل از برآورد کشش مخارجی وکشش قیمتی خودی خودرو به ترتیب نشان دهنده لوکس بودن و با کشش بودن خودرو در اقتصاد ایران می‌باشد. همچنین نتایج برآورد کشش‌های قیمتی متقاطع خودرو با سایر گروهها نشان میدهد که خودرو کالایی جانشین با سه گروه (خوراک، غیر خوراک، مسکن) می‌باشد بدین مفهوم که افزایش قیمت خودرو سبب افزایش سهم هر سه گروه در سبد هزینه ای خانوارمی شود. تفاصيل المقالة -
حرية الوصول المقاله
228 - واکنش صنایع اروپایی واردکننده نفت ایران به قیمت‌های انرژی: تحلیل بین عاملی و بین سوختی
سمیه اعظمی کیومرث سهیلی مرجان قاسمیچکیده هدف این مقاله بررسی واکنش صنایع کارخانه‌ای کشورهای اروپایی واردکننده نفت ایران نسبت به قیمت‌های انرژی در فاصله زمانی 2005-1970 است. از یک مدل ترانسلوگ دو مرحله‌ای برای تخمین کشش‌های تقاضای عوامل تولید و تقاضای سوخت استفاده شد. نتایج تحلیل بین عاملی نشان داد در غال أکثرچکیده هدف این مقاله بررسی واکنش صنایع کارخانه‌ای کشورهای اروپایی واردکننده نفت ایران نسبت به قیمت‌های انرژی در فاصله زمانی 2005-1970 است. از یک مدل ترانسلوگ دو مرحله‌ای برای تخمین کشش‌های تقاضای عوامل تولید و تقاضای سوخت استفاده شد. نتایج تحلیل بین عاملی نشان داد در غالب کشورها، انرژی یک نهاده تولیدی کم کشش است. نتایج تحلیل بین سوختی نشان داد گاز طبیعی سوخت جایگزین برای گازوییل در صنایع اروپایی است. با افزایش قیمت برق و گاز طبیعی، پیش‌بینی می‌شود نفت در بیشتر کشورها سوخت جایگزین برای این حامل‌های انرژی باشد. حساسیت تقاضای انواع حامل‌های انرژی (به استثنای گازوییل) کوچک برآورد شده است. این مطالعه نتایج مهمی برای تأمین‌کنندگان انرژی این صنایع و سیاست‌گذاران مسایل زیست محیطی دارد. تفاصيل المقالة -
حرية الوصول المقاله
229 - تقاضای غذای خارج از خانه خانوارهای ایرانی: کاربردی از الگوی دابل- هاردل با تبدیل باکس- کاکس
حسن فرازمند حمیدرضا حلافیچکیده هدف این مقاله ارزیابی عوامل اقتصادی و دموگرافیکی موثر بر احتمال مشارکت و میزان مصرف خارج از خانه در چارچوب نظریه تولید - مصرف خانگی بکر(1965) است. در این راستا از الگوی دابل هاردل با تبدیل باکس- کاکس و داده‌های آماری درآمد- هزینه خانوار شهری و روستایی کشور در سا أکثرچکیده هدف این مقاله ارزیابی عوامل اقتصادی و دموگرافیکی موثر بر احتمال مشارکت و میزان مصرف خارج از خانه در چارچوب نظریه تولید - مصرف خانگی بکر(1965) است. در این راستا از الگوی دابل هاردل با تبدیل باکس- کاکس و داده‌های آماری درآمد- هزینه خانوار شهری و روستایی کشور در سال 1391 بهره‌برداری شده است. یافته‌ها نشان میدهد اثرات متغیرهای توضیحی بر احتمال مشارکت و هزینه غذای خارج از خانه گاه همسو و گاه متناقض بوده است. در حالی که بعد خانوار و سطح تحصیلات آن به ترتیب با کشش‌های منفی و مثبت، اثرات همسو دارند. متوسط سن خانوار، اثر دوگانه‌ای در کشش‌های احتمال مشارکت و مصرف غذای خارج از خانه بر جای می‌گذارد. تفاصيل المقالة -
حرية الوصول المقاله
230 - احتساب کشش‌های قیمتی و درآمدی مواد غذایی خانوارهای شهری استان تهران
ویدا ورهرامی زهره هوشمند رضا یوسفی حاجی آبادچکیده هدف این مقاله محاسبه کشش‌های قیمتی، متقاطع و درآمدی مواد غذایی خانوارهای شهری استان تهران است. برای این منظور، داده‌های اقلام مواد غذایی خانوارهای شهری استان تهران، به تفکیک گروه‌های مختلف کالاهای مصرفی خانوار، جمع‌‌آوری و با استفاده از سیستم تقاضای تقریباً ایده أکثرچکیده هدف این مقاله محاسبه کشش‌های قیمتی، متقاطع و درآمدی مواد غذایی خانوارهای شهری استان تهران است. برای این منظور، داده‌های اقلام مواد غذایی خانوارهای شهری استان تهران، به تفکیک گروه‌های مختلف کالاهای مصرفی خانوار، جمع‌‌آوری و با استفاده از سیستم تقاضای تقریباً ایده‌آل ترکیبی، بر اساس روش رگرسیون‌های به ظاهر نامرتبط (SUR)، طی دوره زمانی 1391-1383، رفتار مصرفی خانوارها و کشش‌های مختلف درآمدی، متقاطع و قیمتی محاسبه شده است. نتایج نشان میدهد گروه‌های غلات، لبنیات و گروه روغن‌ها جزء کالاهای ضروری و گروه‌های گوشت و ماهی جزء کالاهای لوکس محسوب می‌شوند. کشش‌های قیمتی متقاطع در اغلب موارد ازلحاظ قدر مطلق کمتر از یک است. همچنین کشش خود قیمتی گروه ماهی بیشتر از واحد است و به عبارت دیگر، جزء کالاهای پرکشش می‌باشد. تفاصيل المقالة -
حرية الوصول المقاله
231 - جداسازی و محاسبه ریسک‌گریزی نسبی و کشش جانشینی بین دورهای (رویکرد ترجیحات بازگشتی و برنامه‌ریزی پویا)
رضا روشنچکیده هدف این مقاله جداسازی و محاسبه ریسک‌گریزی نسبی و کشش جانشینی بین دورهای با استفاده از ترکیب ترجیحات بازگشتی و قید بودجه مصرف‌کننده است. بدین منظور، ابتدا پرتفوی دارایی‌های خانوارهای ایرانی تشکیل شد و سپس، به کمک روش گشتاورهای تعمیم‌یافته و تابع مطلوبیت، معادلات أکثرچکیده هدف این مقاله جداسازی و محاسبه ریسک‌گریزی نسبی و کشش جانشینی بین دورهای با استفاده از ترکیب ترجیحات بازگشتی و قید بودجه مصرف‌کننده است. بدین منظور، ابتدا پرتفوی دارایی‌های خانوارهای ایرانی تشکیل شد و سپس، به کمک روش گشتاورهای تعمیم‌یافته و تابع مطلوبیت، معادلات اولر طی دوره 1393-1357 مورد بررسی قرار گرفت. نتایج برآورد مدلهای مختلف نشان داد رابطه دوسویه معکوس بین دو پارامتر یاد شده وجود ندارد و خانوارهای ایرانی، تمایل به تثبیت و هموارسازی مصرف در شرایط و زمانهای مختلف دارند. بر اساس نتایج، پیشنهاد می‌شود توسعه و شفاف‌سازی بیشتر بازارهای مالی در دستور کار برنامه‌ریزان قرار گیرد تا سرمایه‌های خرد خانوارها از طریق چنین بازارهایی به سمت بازسازی زیرساخت‌های کشور هدایت شود. تفاصيل المقالة -
حرية الوصول المقاله
232 - تاثیر شش هفته تمرین مقاومتی با کش تراباند بر شاخص های عملکردی بازیکنان جوان
هامون دلدار سیاوش رحمتی بهزاد طاعتیزمینه و هدف : شاخص های عملکردی و به طور خاص ، تعادل ، انعطاف پذیری و قدرت عضلات همسترینگ می تواند تاثیر بسزایی در عملکرد رقابتی بازیکنان فوتبال داشته باشد ، به گونه ای که حتی می تواند از آسیب دیدگی فوتبالیستها نیز تا حدودی بکاهد . هدف از پژوهش حاضر بررسی تاثیر استفاده ا أکثرزمینه و هدف : شاخص های عملکردی و به طور خاص ، تعادل ، انعطاف پذیری و قدرت عضلات همسترینگ می تواند تاثیر بسزایی در عملکرد رقابتی بازیکنان فوتبال داشته باشد ، به گونه ای که حتی می تواند از آسیب دیدگی فوتبالیستها نیز تا حدودی بکاهد . هدف از پژوهش حاضر بررسی تاثیر استفاده از کش های تراباند در کنار تمرینات معمول فوتبال بر شاخص های عملکردی بازیکنان فوتبال بود. مواد و روش ها : 16 فوتبالیست شاغل در لیگ های استان تهران در این پژوهش شرکت کرده و به طور تصادفی در دو گروه هشت نفری شامل گروه تراباند(تمرینات معمول فوتبال و تمرینات تراباند) و گروه کنترل( تمرینات معمول فوتبال) تقسیم شدند . پروتکل تمرینی شامل شش هفته تمرینات 90 دقیقه ای فوتبال و هفته ای 3 جلسه بود . تفاوت تمرینات دو گروه در 20 دقیقه هسته مرکزی تمرینات بوده و گروه تراباند در این زمان 20 دقیقه ای به تمرینات ویژه با کش تراباند اقدام نمود. پیش آزمون و پس آزمون های هر دو گروه به صورت یکسان و در یک زمان واحد اخذ شد.تعادل بازیکنان به وسیله آزمون رومبرگ سنجیده شد و انعطاف پذیری بازیکنان توسط آزمون ولز (نشستن و رساندن دستها) ، قدرت عضلات همسترینگ نیز توسط دینامومتر بایودکس مدل سه ساخت کشور آمریکا اندازه گیری شد. تفاصيل المقالة -
حرية الوصول المقاله
233 - Numerical Simulation of the Effect of Elastic Deformation of work rolls on the rolling force and Comparison with the Results obtained by the Slab Method during the reciprocating cold rolling
Mohammad Heydari ViniCold rolling process of a major transformation in the form of sheet metal and a wide range of steel products are produced in this way. Elastic deformation during cold rolling working rollers and the inevitable increase in the rolling force. In this study, the effect of أکثرCold rolling process of a major transformation in the form of sheet metal and a wide range of steel products are produced in this way. Elastic deformation during cold rolling working rollers and the inevitable increase in the rolling force. In this study, the effect of elastic deformation during cold rolling mill rollers working on the reciprocating back and forth in tandem with the presence of tensile stresses two cages will be discussed. In this system, rolling, sheet by passing between two shelves inreciprocating motion to achieve the desired final thickness (almost three passes reciprocating 2 shelves). One of the most important factors during the cold rolling process, determine the force and pressure rolling. By writing equations deformed sheet Slab Method software MATLAB, as well as a passer by reciprocating rolling process simulation software ABAQUS, force and pressure of the rolling mill for the entire process and shelves, with or without the effects of disruption flat work rollers were calculated. Finally three different passes into the shelf rolled on a coil of cold rolled steel products took place. The results showed a sharp increase in the working rollers are rolling in the flat disruption. تفاصيل المقالة -
حرية الوصول المقاله
234 - A New Temper Rolling Force Model for Dry Thick Strip Considering Fully Elastic Contact
Pedram Farhadipour Mohammad Heydari Vini Sayed Mohammad Reza LoghmanianTemper rolling or skin pass rolling is one of cold rolling processes composed of a horizontal pass cold rolling mill stand. In this process, the thick strip is subjected to very light reduction (0.5–4%) in thickness in the presence of high friction amplitudes. One أکثرTemper rolling or skin pass rolling is one of cold rolling processes composed of a horizontal pass cold rolling mill stand. In this process, the thick strip is subjected to very light reduction (0.5–4%) in thickness in the presence of high friction amplitudes. One of the basic parameters of strip rolling processes is temper rolling force. A new rolling force model has been proposed for temper rolling strip mill considering the inhomogeneous stress distribution along the thickness of the strip. The contact between rolls and thick strip is totally elastic. The deformation field consists of an elastic (actually elastic) zone and that is highly non-homogeneous across the thickness of the strip. Totally elastic formulation can be used to predict the roll force. It can be used to study the stress distribution along the thickness of strip. The computing results from this model coincide the similar presented results in previous investigations done. تفاصيل المقالة -
حرية الوصول المقاله
235 - Numerical and Analytical Investigation of a Cylinder Made of Functional Graded Materials under Thermo-Mechanical Fields
Javad Jafari Fesharaki Seyed Ghasem Madani Sa’id GolabiThis research develops thermo-elastic analysis of a functionally graded cylinder under thermo-mechanical loadings. Heat conduction equation in cylindrical coordinate system is solved. Thermal conductivity coefficient is graded along the radial direction. By considering أکثرThis research develops thermo-elastic analysis of a functionally graded cylinder under thermo-mechanical loadings. Heat conduction equation in cylindrical coordinate system is solved. Thermal conductivity coefficient is graded along the radial direction. By considering a symmetric distribution of temperature, loading and boundary conditions, strain-displacement and stress-strain relations can be developed. Material properties such as modulus of elasticity are graded along the radial direction. For validation of the obtained results; a complete numerical analysis using finite element approach is presented. تفاصيل المقالة -
حرية الوصول المقاله
236 - کنترل کننده تطبیقی-عصبی در جراحی رباتیک قلب در حال تپش بر اساس مدل ارتجاعی-چسبندگی بافت
ستاره رضاخانی مهدی علیاری شوره دلی اعظم قاسمیدر این مقاله، مشکل جبران حرکات قلب در سه راستا با استفاده از طراحی کنترل کننده‌ی موازی نیرو و موقعیت حل می‌گردد. کنترل کننده موقعیت با استفاده از روش تطبیقی-موجک جهت جبران حرکات سه بعدی بافت و مواجهه با نامعینی‌های ساختاری در معادلات ربات، طراحی می‌گردد و کنترل نیرو نیز أکثردر این مقاله، مشکل جبران حرکات قلب در سه راستا با استفاده از طراحی کنترل کننده‌ی موازی نیرو و موقعیت حل می‌گردد. کنترل کننده موقعیت با استفاده از روش تطبیقی-موجک جهت جبران حرکات سه بعدی بافت و مواجهه با نامعینی‌های ساختاری در معادلات ربات، طراحی می‌گردد و کنترل نیرو نیز به صورت ضمنی، انجام می‌شود. مدل برهم کنش بافت قلب و ابزار نهائی ربات، به صورت ارتجاعی- چسبندگی در نظر گرفته شده است. در اثبات پایداری کنترل کننده، از قانون لیاپانف و لم باربالت استفاده می‌شود. بدین منظور یک تابع لیاپانف مثبت معین در نظر گرفته شده و در اثبات پایداری استفاده شده است. شبیه سازی‌ها بر روی ربات D2M2 صورت گرفته و نشان‌دهنده کارایی کنترل کننده می‌باشد. تست مقاوم بودن عملکرد نیز در مواجه با بافت‌های مختلف انجام و نتایج ارائه گردیده است. تفاصيل المقالة -
حرية الوصول المقاله
237 - نقش فاصله مابین و کاربرد میراگر ویسکوالاستیک برای کاهش اثرضربه‌ای زلزله در ساختمان های بتنی کوتاه مجاور
سیدمهدی زهرائی سید محمد خاتمیرشد چشمگیر ساختمان‌ها در اشکال و ارتفاع های مختلف در حوزه شهرنشینی و عدم توجه به وابستگی آنها در مجاورت یکدیگر به هنگام بروز زلزله، مشکلات ناشی از اثرات نامطلوب بارهای لرزه‌ای را افزایش داده است. ساختمانهای ساخته شده هر یک به تنهایی در برابر بارهای لرزه‌ای محاسبه و سا أکثررشد چشمگیر ساختمان‌ها در اشکال و ارتفاع های مختلف در حوزه شهرنشینی و عدم توجه به وابستگی آنها در مجاورت یکدیگر به هنگام بروز زلزله، مشکلات ناشی از اثرات نامطلوب بارهای لرزه‌ای را افزایش داده است. ساختمانهای ساخته شده هر یک به تنهایی در برابر بارهای لرزه‌ای محاسبه و ساخته شده‌اند. اما عدم توجه به ضربات ساختمانهای مجاور به یکدیگر در هنگام زلزله، کمتر مورد توجه و بررسی قرار گرفته است. این امر باعث می‌شود هر ساختمان به صورت واحد طراحی شده و در تعداد طبقات متنوع و ارتفاعات مختلف ساخته شوند. ضربات عنوان شده بر دو نوع سقف به سقف و سقف به ستون است که در این مقاله حالت اول بررسی شده است.تفاوت در سختی دو ساختمان باعث ایجاد نیروی نابرابری به سقف ساختمان‌ها می‌شود که موجبات تخریب ساختمان را به همراه دارد. برای مطالعه عددی از نرم‌افزارهای SAP و ANSYS استفاده شده است تا جابجایی جانبی و نیروی ضربه به صورت غیرخطی نشان داده شده و همچنین میزان ترک‌خوردگی در ضربه نشان داده شود.در این مطالعه و برای بررسی میزان نیروی ضربات ساختمان‌ها به یکدیگر و نحوه کاهش آن، از دو ساختمان بتن مسلح 2 و 3 طبقه استفاده شده است و نیروی ضربه بین آنها، مورد مطالعه قرار گرفته است. برای کاهش اثرات ضربه، نقش میزان فاصله مابین دو سازه مجاور و کاربرد میراگرویسکوالاستیک در مهاربندی آنها بررسی شده است. نتایج این تحلیل‌ها نشان میدهد که قرارگیری میراگر و افزایش فاصله دو سازه میتواند با کاهش تغییرمکان جانبی رو به رو بوده و اثرات ضربه‌ای را کاهش دهد. به طور مثال، فاصله 3 سانتی‌متری دو ساختمان مجاور، 7 ضربه را به همراه داشته است که افزایش این فاصله به 5/4 سانتی متر، تعداد این ضربات را به 2 ضربه کاهش میدهد. همچنین قرارگیری میراگر ویسکوالاستیک در طبقات ساختمان باعث کنترل جابجایی جانبی شده و ضربات ساختمان‌ها را به یک ضربه کاهش داده است. تفاصيل المقالة -
حرية الوصول المقاله
238 - بررسی آزمایشگاهی مدول‌الاستیسیته بتن قلیافعال براساس آزمون XRF و SEM
محمدحسین منصورقناعی مرتضی بیک لریان علیرضا مردوخ پوردر این مقاله، ابتدا سه طرح اختلاط از بتن قلیافعال ساخته شد که به ترتیب حاوی 92، 96 و 100 درصد سرباره کوره آهنگدازی و 8، 4 و 0 درصد نانوسیلیس بودند. پس از انجام آزمون مقاومت فشاری و مدول الاستیسیته و انتخاب یک طرح به عنوان طرح بهینه به لحاظ برتری خواص مکانیکی، با افزودن أکثردر این مقاله، ابتدا سه طرح اختلاط از بتن قلیافعال ساخته شد که به ترتیب حاوی 92، 96 و 100 درصد سرباره کوره آهنگدازی و 8، 4 و 0 درصد نانوسیلیس بودند. پس از انجام آزمون مقاومت فشاری و مدول الاستیسیته و انتخاب یک طرح به عنوان طرح بهینه به لحاظ برتری خواص مکانیکی، با افزودن 1 و 2 درصد الیاف پلی اولفین به طرح بهینه، دو طرح دیگر از بتن قلیافعال ساخته شد. تمام نمونه های بتنی تحت آزمون های مقاومت فشاری و مدول الاستیسیته، XRF و SEM، قرار گرفتند. نتایج حاصل از آزمون های این پژوهش نشان از برتری در خواص مکانیکی و ریزساختاری بتن قلیافعال نسبت به بتن معمولی را در تمام سنین عمل آوری داشت. در سن عمل آوری 90 روزه (به عنوان بهترین سن در عملکرد با توجه پیشرفت فرایند شیمیایی)، پیرو آزمون مقاومت فشاری کمترین (94/49 مگاپاسکال) و بیشترین (36/66 مگاپاسکال) مقدار مقاومت فشاری به ترتیب برای طرح 1 شامل بتن معمولی و طرح 4 شامل بتن قلیافعال حاوی 8 درصد نانوسیلیس کسب گردید. در همین سن عمل آوری، کمترین (44/32 گیگاپاسکال) و بیشترین (51/42 گیگاپاسکال) مقدار مدول الاستیسیته بتن به ترتیب در طرح 1 و 6 شامل بتن قلیافعال حاوی 8 درصد نانوسیلیس و 2 درصد الیاف پلی اولفین، به دست آمد. در این سن، افزودن 8 درصد نانوسیلیس و 2 درصد الیاف در بتن قلیافعال طرح 6 موجب افت 49/22 درصدی در مقاومت فشاری و بهبود 05/7 درصدی در مدول الاستیسیته گردید. تفاصيل المقالة -
حرية الوصول المقاله
239 - بررسی آثار حرارت بالا بر مقاومت فشاری، کششی و مدول‌الاستیسیته بتن قلیافعال
محمدحسین منصورقناعیدر سال های اخیر، بهبود خواص مکانیکی در بتن قلیافعال با هدف برتری نسبت به خواص مکانیکی بتن معمولی و کاهش مخاطرات زیست محیطی ناشی از کمبود منابع معدنی و انتشار گاز سمی دی اکسیدکربن در هوا (در راستای تولید سیمان)، مورد توجه محققین حوزه عمران قرار گرفت. در این پژوهش آزمایشگ أکثردر سال های اخیر، بهبود خواص مکانیکی در بتن قلیافعال با هدف برتری نسبت به خواص مکانیکی بتن معمولی و کاهش مخاطرات زیست محیطی ناشی از کمبود منابع معدنی و انتشار گاز سمی دی اکسیدکربن در هوا (در راستای تولید سیمان)، مورد توجه محققین حوزه عمران قرار گرفت. در این پژوهش آزمایشگاهی، یک طرح اختلاط از بتن معمولی حاوی سیمان پرتلند با عیار 500 کیلوگرم بر متر مکعب و یک طرح اختلاط از بتن قلیافعال بر پایه سرباره کوره آهنگدازی ساخته شد. به منظور بررسی خواص مکانیکی، آزمون های مقاومت فشاری، مقاومت کششی و مدول الاستیسیته بتن تحت دمای 21 و 600 درجه سلسیوس در سن عمل آوری 90 روزه انجام شد. در بخش نتایج، اعمال حرارت بالا (600 درجه سلسیوس) به نمونه های بتنی موجب افت 42 و 15 درصدی در مقاومت فشاری، افت 56 و 21 درصدی در مقاومت کششی و افت 63 و 49 درصدی در مدول الاستیسیته به ترتیب برای بتن معمولی و بتن قلیافعال گردید. مقاومت فشاری بتن قلیافعال نسبت به بتن معمولی در دمای 21 و 600 درجه سلسیوس به ترتیب 11 و 64 درصد برتری را نشان داد. مقاومت کششی بتن قلیافعال نسبت به بتن معمولی در دمای 21 و 600 درجه سلسیوس به ترتیب 9 درصد کاهش و 63 درصد برتری را نشان داد. مدول الاستیسیته بتن قلیافعال نسبت به بتن معمولی در دمای 21 و 600 درجه سلسیوس به ترتیب 16 و 62 درصد برتری را کسب کرد. نتایج حاصل از آزمون تصاویر میکروسکوپ الکترونی روبشی در هماهنگی و همپوشانی با سایر نتایج آزمون های این پژوهش قرار دارد. تفاصيل المقالة -
حرية الوصول المقاله
240 - بررسی رفتار چرخه‌ای دیوارهای برشی فولادی سخت شده با اتصالات نیمه صلب به قاب فولادی
سینا شیرجنگ احمد ملکیبا افزایش تحقیقات روی عملکرد لرزه‌ای دیوارهای برشی فولادی و افزایش اطمینان از عملکرد آنها استفاده از این دیوارها به‌خصوص در آمریکا و ژاپن به نحو محسوسی گسترش یافته است. باتوجه به شناخت نسبتاً جامعی از رفتار این دیوارها اکنون آیین‌نامه‌های طراحی شروع به ارائه ضوابط طرا أکثربا افزایش تحقیقات روی عملکرد لرزه‌ای دیوارهای برشی فولادی و افزایش اطمینان از عملکرد آنها استفاده از این دیوارها به‌خصوص در آمریکا و ژاپن به نحو محسوسی گسترش یافته است. باتوجه به شناخت نسبتاً جامعی از رفتار این دیوارها اکنون آیین‌نامه‌های طراحی شروع به ارائه ضوابط طراحی برای این دیوارها نموده‌اند. اساس عملکرد این سازه‌ها مبتنی بر بهره‌گیری از عملکرد میدان کششی قطری پس از کمانش ورق فولادی می‌باشد. در این تحقیق قبل از بررسی عملکرد دیواربرشی‌‌های فولادی با اتصالات مفصلی، جهت اطمینان از نتایج عددی، به صحت سنجی نمونه آزمایشگاهی پرداخته و بعد از ارزیابی نتایج، به مدلسازی 12 نمونه دیواربرشی فولادی با نرم افزار آباکوس پرداخته شده است. در این نمونه‌ها به بررسی پارامترهایی از قبیل ضخامت ورق دیواربرشی، مشخصات هندسی تیر‌ها و ستون‌ها و میزان بازشدگی گوشه‌های ورق پرداخته شده است. نتایج حاصل از این تحقیق مشخص کرد که با افزایش سطح مقطع ستون‌ها توزیع تنش به صورت یکنواختی در سطح ورق گسترده شده و کل سطح ورق به سمت خارج از صفحه کمانش کرده، این در حالی است که در صورت افزایش مقطع تیر کمانش اغلب به صورت قطری در ورق‌ها دیده می‌شود. این در حالی است که در صورت افزایش ضخامت ورق دیواربرشی مقدار کرنش غیر‌الاستیک ایجاد شده کمتر شده و تقریبا محدود به قسمت‌های تحتانی ورق طبقه اول بوده است. با افزایش 20 درصدی ضخامت ورق دیواربرشی ظرفیت باربری و سختی نمونه‌ها به طور متوسط در حدود 18 درصد افزایش یافته و همچنین با افزایش میزان بازشدگی از 5 به 15 درصد ظرفیت باربری در حدود 20 درصد کاهش یافته و مقدار کرنش پلاستیک به صورت قطری در ورق‌ها ایجاد شده است. تفاصيل المقالة -
حرية الوصول المقاله
241 - بررسی اثر اندرکنش خاک و سازه بر پاسخ سازه‌های با میراگر ویسکوالاستیک تحت میرایی‌های مختلف
مسعود پوربابا سعید جواهرزاده فریبا سیدی محمدیکاهش انرژی ورودی به سازه‌ها با استفاده از میراگرهای الحاقی،روشی مؤثر در میرا نمودن انرژی ورودی به سازه است. از جمله ابزارهای مناسب برای میرا نمودن انرژیورودی سازه، میراگر ویسکوالاستیک است.با توجه به این که عموماً در تحلیل سازه‌ها خاک واقع در زیر سازه‌ها صلب فرض می‌شود و أکثرکاهش انرژی ورودی به سازه‌ها با استفاده از میراگرهای الحاقی،روشی مؤثر در میرا نمودن انرژی ورودی به سازه است. از جمله ابزارهای مناسب برای میرا نمودن انرژیورودی سازه، میراگر ویسکوالاستیک است.با توجه به این که عموماً در تحلیل سازه‌ها خاک واقع در زیر سازه‌ها صلب فرض می‌شود و از اثر اندرکنش خاک و سازه صرفنظر می‌شود ولی در واقعیت این خاک صلب نیست و وجود خاک در زیر سازه باعث تغییر خصوصیات دینامیکی سازه و در نتیجه پاسخ آن می‌گردد.پاسخ سازه و عملکرد میراگرها به مؤلفه‌های گوناگونی از جمله نوع حرکت زمین و مشخصات خاک بستگی دارد.در این پژوهشچند قاب بتنی خمشی ویژه دو بعدی مورد بررسی قرار گرفته است، که در آن برای مدلسازی قاب با میراگر الحاقی از روش Kelvin در قابها استفاده شده و برای مدلسازی اثر اندرکنش خاک بر روی سازه‌ی با میراگر الحاقی از روش فنر و میراگر معادل در نرم‌افزار OpenSees استفاده شده است. قابهای مورد مطالعه پس از بهسازی با میراگر، تحت تحلیل دینامیکی تاریخچه زمانی غیرخطی قرار گرفته‌اند و این تحلیل در سه میرایی 5%، 10% و 15% انجام گرفته است. در پایان نتایج حاصل از تأثیر میراگر ویسکوالاستیک با وجود اندرکنش خاک و سازه تحت میرایی‌های مختلف مورد بررسی قرار گرفته است. تفاصيل المقالة -
حرية الوصول المقاله
242 - مطالعه آزمایشگاهی مدول الاستسیته دینامیکی گروت‌های پایه سیمانی با استفاده از تکنولوژی نانو و میکرو مواد
میثم شیرزاد شهریور امین قلی زادروش اندازه گیری سرعت گذر امواج اولتراسونیک بعنوان ابزاری برای آزمایش مصالح و به منظور تعیین کیفیت و مقاومت مورد استفاده قرار می گیرد. سرعت گذر امواج اولتراسونیک از جامدات به دانسیته و مشخصات الاستیسیته آنها بستگی دارد. کیفیت برخی از مواد در بعضی موارد بستگی به میزان سخت أکثرروش اندازه گیری سرعت گذر امواج اولتراسونیک بعنوان ابزاری برای آزمایش مصالح و به منظور تعیین کیفیت و مقاومت مورد استفاده قرار می گیرد. سرعت گذر امواج اولتراسونیک از جامدات به دانسیته و مشخصات الاستیسیته آنها بستگی دارد. کیفیت برخی از مواد در بعضی موارد بستگی به میزان سختی و الاستیسیته آنها دارد، بنابراین اندازه گیری سرعت گذر امواج در چنین مصالحی می تواند برای تعیین کیفیت و خصوصیات الاستیکی این مواد مورد استفاده قرار گیرد. با توجه به کاربرد گروت های پایه سیمانی در صنعت سازه در پر کردن فاصله بین اعضای سازه ای و فونداسیون های بتنی و نیاز به توانایی جذب و انتقال انواع بارهای استاتیکی و دینامیکی توسط گروت به فونداسیون، همواره مهندسین سازه نیازمند گروتی با کیفیت، مقاومت و دوام بالا هستند. برای دست یابی به این مهم گروت باید دارای ساختار درونی مستحکم و با حداقل خلل و فرج و حفرات داخلی باشد تا بخوبی در شرایط مختلف جوی اعم از ذوب و انجماد های متوالی و سایر شرایط نامساعد که در طول دوران سرویس، سلامت و کیفیت آن را تهدید می کند انجام وظیفه کند. جهت بررسی این ویژگی ها یکی از بهترین راه کارها تست سرعت عبور امواج اولتراسونیک از داخل نمونه های گروت هست که در این مقاله انجام شده و نتایج آن در قالب نمودار ها و جداول برپایه سرعت عبور امواج و مدول الاستیسسته دینامیکی مقایسه شده است. نتایج در بسیاری از موارد حاکی از افزایش مدول الاستیسیته دینامیکی بر اثر اصلاح ترکیب گروت با پودر نانوسیلیس و میکروسیلیس است بطوری که با جایگزینی نانوسیلیس و میکروسیلیس به ترتیب با 1 و 20 درصد وزنی سیمان در ترکیب گروت، افزایش 64 درصدی مدول الاستیسیته دینامیکی حاصل گردیده است. تفاصيل المقالة -
حرية الوصول المقاله
243 - مطالعه عددی رفتار اتصالات کاهش یافته تیرهای متصل به ستون‌های صلیبی شکل در قابهای خمشی
امین فلاحی مطلق احمد ملکیمطالعات گسترده‌ای که پس از این زلزله نورثریج انجام شد، نشان داد که فاکتورهای متعددی در بروز این شکست موثر بوده‌اند. تمرکز تنش بالا در جوش‌های بال و آسیب‌پذیری اتصال در برابر نیاز شکل‌پذیری بالا دو عامل اصلی بروز این گسیختگی تشخیص داده شدند. راه منطقی برای حل این مشکل کا أکثرمطالعات گسترده‌ای که پس از این زلزله نورثریج انجام شد، نشان داد که فاکتورهای متعددی در بروز این شکست موثر بوده‌اند. تمرکز تنش بالا در جوش‌های بال و آسیب‌پذیری اتصال در برابر نیاز شکل‌پذیری بالا دو عامل اصلی بروز این گسیختگی تشخیص داده شدند. راه منطقی برای حل این مشکل کاهش دادن نیاز شکل‌پذیری در نواحی جوش شده و پایین آوردن تراز تمرکز تنش در آن‌هاست. روش‌های اصلاحی متعددی برای ساخت و ساز بعد از زلزله نورثریج و نیز مقاوم‌سازی سازه های فولادی گیردار موجود پیشنهاد شد. یکی از این روش‌ها پیکربندی تیر کاهش‌یافته است. در این تحقیق بعد از اطمینان از نتایج مدلسازی با استفاده از نرم افزار اباکوس، به مدلسازی 9 نمونه اتصال تیر با بال کاهش یافته به ستون صلیبی در سه گروه مدلسازی شده است. نتایج حاصل شده از این تحقیق به این شرح می‌باشد: کاستن از طول پیوند بیشترین اثر نیروی برشی را بر عملکرد غیر الاستیک دارد. مکانیزم تسلیم برشی پیوند کوتاه‌تر بهتر از مکانیزم تسلیم خمشی پیوندهای بلند است و دلیل اصلی آن این است که در پیوندهای برشی، نیروهای برشی در تمام طول پیوند ثابت است لذا کرنش‌های غیر الاستیک به طور یکنواخت در طول پیوند توزیع خواهند شد. همچنین در نمونه با فاصله مقطع پیوند 0.6b که دارای ضعیف‌ترین عملکرد بوده است در سیکل‌های ابتدایی (سیکل سوم) افت مقاومت شروع شده است. به طوری که مقدار جذب انرژی پایینی نسبت به سایر نمونه‌ها دارد. نمونه بدون مقطع کاهش یافته با جذب انرژی 9272 کیلونیوتن در متر نسبت به نمونه با فاصله 0.75b و 0.6b به ترتیب 11/5 درصد و 66/6 درصد دارای جذب انرژی و قابلیت استهلاک بیشتری نسبت به سایر نمونه‌ها می‌باشد. در نمونه با شکل هندسی استخوانی در سیکل‌های ابتدایی (سیکل سوم) افت مقاومت شروع شده است. به طوری که مقدار جذب انرژی پایینی نسبت به سایر نمونه‌ها دارد. نمونه با مقطع دایره‌ای با جذب انرژی 8875 کیلونیوتن در متر نسبت به نمونه با شکل هندسی استخوانی و بیضی به ترتیب 6/18 درصد و 54/1 درصد دارای جذب انرژی و قابلیت استهلاک بیشتری نسبت به سایر نمونه‌ها می‌باشد. تفاصيل المقالة -
حرية الوصول المقاله
244 - بررسی رفتارلرزه ای غیرخطی ساختمانهای بلندمرتبه بتن آرمه وبهسازی آنها به وسیله میراگرهای ویسکوالاستیک
فراز کاظمی اشکان خدابنده لوباتوجه به تخریب ساختمان های بلندمرتبه درطی زلزله های اخیر، بکارگیری سیستم سازه ای قاب خمشی بتن آرمه بامیراگرویسکوالاستیک باعث اتلاف انرژی لرزه ای وبه تبع آن کاهش تغییرمکان جانبی می شود.دراین پژوهش یک قاب ساختمانی بلندمرتبه بتن آرمه سه بعدی20طبقه با8 مدل، که4 مدل باسیستم أکثرباتوجه به تخریب ساختمان های بلندمرتبه درطی زلزله های اخیر، بکارگیری سیستم سازه ای قاب خمشی بتن آرمه بامیراگرویسکوالاستیک باعث اتلاف انرژی لرزه ای وبه تبع آن کاهش تغییرمکان جانبی می شود.دراین پژوهش یک قاب ساختمانی بلندمرتبه بتن آرمه سه بعدی20طبقه با8 مدل، که4 مدل باسیستم سازه ای قاب خمشی و 4مدل باسیستم سازه ای قاب خمشی+میراگرویسکوالاستیک دردوامتداد X,Yواقع درمنطقه با لرزه خیزی زیاد(g3/0=A)برروی خاک نوع IIIدرنظرگرفته می شود. هدف از پژوهش حاضربررسی تغییرمکان جانبی افقی (مطلق ونسبی) طبقات، برش پایه قاب ها تحت بارهای ثقلی و بار جانبی زلزله می باشد. برای مدل سازی مواد ویسکوالاستیک ازمدل کلوین-ویت وجهت تعیین نسبت میرایی (ζ)قاب هابامیراگرویسکو الاستیک، ضریب سختی(KV)وضریب میرایی(CV)میراگرهای ویسکوالاستیک ازروش انرژی کرنشی مودال وجهت تحلیل لرزه ای مدل های بدون وبا میراگربه ترتیب ازتحلیل دینامیکی تاریخچه زمانی غیرخطی به روش انتگرال گیری مستقیم ومودال(FNA) استفاده ومدلسازی هندسی کلیه قاب ها درنرم افزار SAP2000-V15انجام شده است .نتایج حاکی ازآن است باافزایش طول دهانه(مدل2نسبت به مدل1ومدل4 نسبت به مدل3) وافزایش ارتفاع طبقات (مدل3نسبت به مدل1ومدل4نسبت به مدل2)، حداکثرتغییرمکان جانبی مطلق، نسبی طبقات و برش پایه درامتداد(X,Y)بدون و با میراگرروندی افزایشی دارد. همچنین حداکثردرصد افزایش مدلهای مذکوربا میراگرنسبت به بدون میراگردرامتداد (X,Y) کاهش یافته است. تفاصيل المقالة -
حرية الوصول المقاله
245 - Comparing Estimations of Return to Scale in Mechanized and Semi-Mechanized Broiler Chick Farms Located in Gorgan City
N. Alazmani A.R. Yazdani A. DarijaniQuantitative analysis of production through evaluation of inputs consumption quantity is of main principles in agricultural policies, which is followed by increasing in production through optimal use of resources. This study has been conducted to estimate different type أکثرQuantitative analysis of production through evaluation of inputs consumption quantity is of main principles in agricultural policies, which is followed by increasing in production through optimal use of resources. This study has been conducted to estimate different types of production functions in mechanized farms of broiler chicks located in Gorgan city. Cross-section survey data were gathered in spring of 2009 via filling in 71 questionnaires and also interviews with managers of broiler chicks farms located in Gorgan were made. Then, according to viewpoints of experts, mechanization level of each broiler chick farm was assigned and grouped into two mechanized and semi-mechanized groups. Afterward, Linear, Cobb-Douglas and Transcendental production functions were estimated and analyzed for the mentioned groups. Results showed that the best functions for mechanized and semi-mechanized farms are linear and Cobb-Douglas models, respectively. Also, return to scale in mechanized and semi-mechanized broiler chick farms showed diminishing and ascending trends, respectively. تفاصيل المقالة -
حرية الوصول المقاله
246 - بررسی شاخص های مهم در افزایش ظرفیت باربری خاک های مشکل دار برای اجرای سازه های هیدرولیکی با استفاده از سیمان
امیرعباس کمان بدست روزبه آقا مجیدینیاز روز افزون به خاک به عنوان اصلی‌ترین مصالح در پروژه‌های آبی و کانال‌های انتقال آب و عدم وجود خصوصیات کیفی و ژئوتکنیکی لازم در تمامی خاک‌ها، امروزه بهسازی خاک را با استفاده از مصالح و مواد افزودنی مورد توجه قرار داده است. مدول الاستیسیته خاک نشانگر مقدار کرنش خاک در أکثرنیاز روز افزون به خاک به عنوان اصلی‌ترین مصالح در پروژه‌های آبی و کانال‌های انتقال آب و عدم وجود خصوصیات کیفی و ژئوتکنیکی لازم در تمامی خاک‌ها، امروزه بهسازی خاک را با استفاده از مصالح و مواد افزودنی مورد توجه قرار داده است. مدول الاستیسیته خاک نشانگر مقدار کرنش خاک در برابر مقدار مشخصی از تنش است. هر چه مقدار این پارامتر بیشتر باشد، خاک در برابر تنش‌های وارده تغییر شکل کمتری خواهد داشت. هدف این تحقیق، بررسی تأثیر سیمان و تغییرات تراکم بر مدول الاستیسیته و مقاومت فشاری خاک‌های رسی مسئله‌دارمیباشد.. در این تحقیق نمونه‌های خاک رسی تنها و خاک رسی با درصد اختلاط سیمان 10 درصد و در رطوبت‌های بهینه، در تراکم‌های 85، 95 و 100 درصد مورد آزمایش تک محوری قرار گرفتند. نتایج حاصل از آزمایش‌ها دلالت بر این دارد که مدول الاستیسیته با اضافه کردن سیمان تا 420 برابر بیشتر می‌شود و با افزایش زمان ماندگاری سیمان، مدول الاستیسیته تا چند برابر (بسته به میزان تراکم) افزایش مییابد. هرچه تراکم نمونه بیشتر باشد، این شدت افزایش هم بیشتر است. همچنین سیمان باعث افزایش مقاومت فشاری تا 20 برابر حالت عادی می گردد. واژه‌های کلیدی: مدول الاستیسیته، سیمان، رطوبت، تراکم، کرنش تفاصيل المقالة -
حرية الوصول المقاله
247 - تحلیل کارکردهای شهری در توسعه روستایی (مطالعه موردی: شهرستان رودبار)
منوچهر نصیری مقدم تیمور آمار پرویز رضائیچکیدهمقدمه: نقش شهرهای کوچک در حوزه‌های روستایی و توسعه این مناطق بر کسی پوشیده نیست. کارکرد شهرها در عرصه-هایی چون خدمات رسانی،تبادل عوامل تولید و ایفای نقش مکمل در توسعه مناطق روستایی بروز می یابد.در این راستا برنامه‌ریزان در کشورهای در حال توسعه به مسائلی چون تمرکززد أکثرچکیدهمقدمه: نقش شهرهای کوچک در حوزه‌های روستایی و توسعه این مناطق بر کسی پوشیده نیست. کارکرد شهرها در عرصه-هایی چون خدمات رسانی،تبادل عوامل تولید و ایفای نقش مکمل در توسعه مناطق روستایی بروز می یابد.در این راستا برنامه‌ریزان در کشورهای در حال توسعه به مسائلی چون تمرکززدایی فضایی، کاهش نابرابری‌های منطقه‌ای، دوگانگی شهری - روستایی توجه ویژه داشته و به دنبال اتخاذ راهبردهایی برای برون رفت از این مشکلات هستند. هدف پژوهش: تحلیل کارکردهای شهری در توسعه روستایی شهرستان رودبار است.روش شناسی تحقیق: داده‌های مورد استفاده در تحقیق شامل شاخص جمعیتی نظیر تعداد، خانوار و نرخ رشد در طول دوره های سرشماری 1345 تا 1395 است . در این پژوهش با استفاده ازمدل‌های کمی آنتروپی و کشش‌پذیری به ارزیابی نقش7 شهر: رودبار، منجیل، لوشان، جیرنده، بره‌سر و توتکابن در توسعه روستاهای مجاور آن پرداخته شده است. قلمرو جغرافیایی پژوهش: محدوده مورد مطالعه در این تحقیق شهرستان رودبار در استان گیلان است.نتایج: نتایج حاصل از تحلیل داده‌ها در این تحقیق نشان می دهد که شهر بره‌سر، توانسته است تاثیر مطلوبی در توزیع متعادل و متوازن جمعیت و استقرار سکونتگاه‌های روستایی حوزه نفوذ خود داشته باشد و حوزه نفوذ خود را به سوی تعادل در سلسله مراتب شهری و توزیع فضایی سوق دهد. شهر توتکابن و منجیل نیز تا حدودی توانسته است تعادل را در سلسله مراتب شهری بوجود آورد. ولی شهرهای رستم‌آباد، رودبار، لوشان و جیرنده عامل ایجاد تمرکز جمعیت شده‌اند. همچنین مشخص گردید که در شهرهای شهرستان، تمرکز جمعیت به واسطه وجود خدمات اقتصادی – اجتماعی بیشتر است. واژگان کلیدی: کارکرد شهر، توسعه روستا، شهرستان رودبار، مدل آنتروپی، مدل‌کشش‌پذیری تفاصيل المقالة -
حرية الوصول المقاله
248 - Transmission of International Prices of Corn to Iranian Domestic Markets
یعقوب زراعت کیش هانیه متقاعدMarket volatility remains one of the most important research fields in agricultural economics.Interestingly, price transmission mechanism seems to be symmetric in sectors that are likely to be of high political power.This paper analyzes the price transmission effects fr أکثرMarket volatility remains one of the most important research fields in agricultural economics.Interestingly, price transmission mechanism seems to be symmetric in sectors that are likely to be of high political power.This paper analyzes the price transmission effects from international markets to domestic markets for corn in Iran. For this purpose, we estimate the elasticity of substitution between imported and domestically produced goods. Annual data (1996-2012) are analyzed with an econometric framework based on the Maximum Entropy. The result shows that there is a substitution relationship between imported and domestic corn and in the end; domestic prices areaffected from world price more than the short run. تفاصيل المقالة -
حرية الوصول المقاله
249 - Analysis of the Structure and Savings of the Potato Production Scale Using the Translog Cost Function (Ardabil County)
جلال خیرخواه مقدم ابوالفضل محمودی غلامرضا یاوری امین دلاورThe present study aimed at investigating the production costs and economic benefits of the potato production in Ardabil country, Iran. To do so, 183 potato producers were randomly selected and were asked to present their ideas concerning the production costs and benefit أکثرThe present study aimed at investigating the production costs and economic benefits of the potato production in Ardabil country, Iran. To do so, 183 potato producers were randomly selected and were asked to present their ideas concerning the production costs and benefits through a questionnaire and an interview. A field study was also taken into consideration to enrich the data. The collected data were analyzed through measures of Chi-square, Wald test, and Translog cost function. The results revealed that the cost function structure was non-hemotetic with respect to the Chi-square statistics (36.8) and results of the constant non-returns and non-homogeneous Wald test to the scale’s F- statistics (17.04) were non-cobb Douglas. Allen cross replacement relationship was positive for the dichotomies such as workforce and machinery, machine and seed, workforce and seed, workforce and water, and finally seed and water. However, it was negative for machinery and land inputs, machinery and water, land and machinery, land and labor force, land and seeds, and land and water. The calculated cost elasticity was -1.5044 which indicated a decrease in the average costs for an output increase as the production cost was found in the downstream part of the cost curve. The economies of scale of 2.504 indicated a 2.5 percent increase in the yield for one-percent increase in the cost. تفاصيل المقالة -
حرية الوصول المقاله
250 - Economic Analysis of Water Demand in Greenhouses of Khash Township
Javad Shahraki Neda AliAhmadiThe main goal of this study was to investigate the way of affecting of water in production of cucumber. From aspect of econometrics, mutual relationships of production function and expenses have been analyzed in which Translog cost function has been used. This function أکثرThe main goal of this study was to investigate the way of affecting of water in production of cucumber. From aspect of econometrics, mutual relationships of production function and expenses have been analyzed in which Translog cost function has been used. This function has been estimated using the conditional input demand functions, the shefard theorem, chemical fertilizer, animal fertilizer, labour force, seed, and pesticide in the framework of a system of equations by taking advantage of the irrelevant regression method. Applied inputs is for 151 cucumber Beneficiaries in Khash in farming year of 2011-12 that insider and crossing tendency of input demand for this product has been investigated through collecting questionnaires and using obtained coefficients. The results show that the translog cost model is a good fit compared to the data of research. According to the reviews, demand for water has a minor Insider- succession tendency more than one which shows possible stretch of demand function rather than the price of the inputs. Hence, appropriate pricing policies can be used to take a positive step in preventing the extreme usage of this input and directing beneficiaries for optimum use of these inputs. تفاصيل المقالة -
حرية الوصول المقاله
251 - Analysis of the Effects of Agricultural Inputs Price Liberalization on the Production of Sunflower in Khoy Zone
Ali Bagherzadeh Fatemeh kazemzadehSunflower is one of four main annual oil plants that cultivated in oil and nut varieties. This plant as an important and industrial food product and because of nutritional features and the potential for earning exchange has become a valuable product in foreign and inner أکثرSunflower is one of four main annual oil plants that cultivated in oil and nut varieties. This plant as an important and industrial food product and because of nutritional features and the potential for earning exchange has become a valuable product in foreign and inner markets and has a special position in agricultural sector. Khoy, by producing 40 percent of sunflower productions of country annually, is the greatest sunflower producer in Iran. The main purpose of this study is the analysis of the effects of inputs price liberalization on production of sunflower producers in this city. This study is according to a field research and cross-sectional data of 2009 have been used for it. Results show input price liberalization policy by increasing inputs prices and decreasing demand amounts of inputs, increases the production costs and decreases the production and totally it’s harmful for sunflower producers. For preventing negative effects of liberalization on production, adopting necessary policies such as merging small farms and making big ones to profit by economies of scale and increasing production and productivity with the resulted incomes from liberalization and spending them in scientific researches to produce with low costs are suggested. تفاصيل المقالة -
حرية الوصول المقاله
252 - Application of Artificial Neural Networks (ANN) to Predict Geomechanical Properties of Asmari Limestones
Mahdi Razifard Mashallah Khamechiyan Mohammad Reza Amin‐NaseriA number of common laboratory rock mechanics tests are carried out in all geotechnical projects such as dams, to determine parameters such as porosity, density, water absorption, sonic velocity, Brazilian tensile strength, uniaxial compressive strength, and triaxial com أکثرA number of common laboratory rock mechanics tests are carried out in all geotechnical projects such as dams, to determine parameters such as porosity, density, water absorption, sonic velocity, Brazilian tensile strength, uniaxial compressive strength, and triaxial compressive strength. In this paper, data obtained from two dams in Asmari Formation including Khersan 1 and Karun 4 - both located in Chahar-Mahal Va Bakhtiari Province, Iran - have been subjected to a series of statistical analyses. Then, using Multivariate Linear Regression (MLR) and Artificial Neural Networks values of UCS, E, C, and φ were predicted using the input parameters including depth, compression ultrasonic velocity, porosity, density, and Brazilian tensile strength. The designed ANN in this research was a feedforward backpropagation network which is powerful tool to solve prediction problems. Designed network had two hidden layer (hidden layer 1: 18 neurons and hidden layer 2: 20 neurons). Via comparing designed MLR and ANN models, it was revealed that ANNs (R2 UCS= 0.91, R2 = 0.87, R2 =0.78, R2 EC phi = 0.61) are more efficient than MLR models (R2 UCS= 0.69, R = 0.69, R = 0.66, and R2 22 EC phi = 0.50) in predicting strength and shear parameters of the intact rock. Also, to enhance the credibility of this study, some extra tests were carried out to evaluate the efficiency of network designed for prediction of strength parameters. The results obtained from this network were as: R2 UCS= 0.85, R2E = 0.81. تفاصيل المقالة -
حرية الوصول المقاله
253 - An Analytical Solution for Cylindrical Concrete Tank on Deformable Soil
Shirish Vichare Mandar M. InamdarCylindrical concrete tanks are commonly used in wastewater treatment plants. These are usually clarifier tanks. Design codes of practice provide methods to calculate design forces in the wall and raft of such tanks. These methods neglect self-weight of tank material and أکثرCylindrical concrete tanks are commonly used in wastewater treatment plants. These are usually clarifier tanks. Design codes of practice provide methods to calculate design forces in the wall and raft of such tanks. These methods neglect self-weight of tank material and assume extreme, namely ‘fixed’ and ‘hinged’ conditions for the wall bottom. However, when founded on deformable soil, the actual condition at the wall bottom is neither fixed nor hinged. Further, the self-weight of the tank wall does affect the design forces. Thus, it is required to offer better insight of the combined effect of deformable soil and bottom raft stiffness on the design forces induced in such cylindrical concrete tanks. A systematic analytical method based on fundamental equations of shells is presented in this paper. Important observations on variation of design forces across the wall and the raft with different soil conditions are given. Set of commonly used tanks, are analysed using equations developed in the paper and are appended at the end. تفاصيل المقالة -
حرية الوصول المقاله
254 - Nonlinear Analysis of Reinforced Concrete Columns with Fiber Reinforced Polymer Bars
Ehab M LotfyIn this paper, the results of an analytical investigation on the behavior of RC columns reinforced with fiber reinforced polymer bars FRP are presented and discussed. Nonlinear finite element analysis on 10-column specimens was achieved by using ANSYS software. The nonl أکثرIn this paper, the results of an analytical investigation on the behavior of RC columns reinforced with fiber reinforced polymer bars FRP are presented and discussed. Nonlinear finite element analysis on 10-column specimens was achieved by using ANSYS software. The nonlinear finite element analysis program ANSYS is utilised owing to its capabilities to predict either the response of reinforced concrete columns in the post-elastic range or the ultimate strength of a reinforced concrete columns reinforced by FRP bars. An extensive set of parameters is investigated including different main reinforcement ratios, main reinforcement types (GFRP, Steel), the transverse reinforcement ratios, and the characteristic compressive strength of concrete.A comparison between the experimental results and those predicted by the existing models are presented. Results and conclusions may be useful for designers, have been raised, and represented. تفاصيل المقالة -
حرية الوصول المقاله
255 - Evaluation of the Performance of Visco-elastic Dampers in Near-fault Earthquakes using Nonlinear Time-history Analysis
Rasoul Sabe-ahd Kolsum Jafarzadeh Mohammad Ali Lotfollahi-YaghinRecords from near-fault earthquakes to close the distance where the wave propagation source is a special property that their behavior makes them different from other records. Mostly near-fault earthquakes have strong pulse velocity (pulsatile wave) with great period acc أکثرRecords from near-fault earthquakes to close the distance where the wave propagation source is a special property that their behavior makes them different from other records. Mostly near-fault earthquakes have strong pulse velocity (pulsatile wave) with great period accompanied with permanent deformation of earth. Velocity pulse occurs in horizontal component perpendicular to the motion surface of fault which is resultant of directionality effect of fault rupture. The properties of pulse such as velocity record in near-fault earthquakes cause the response spectrum to show non-ordinary behavior in pulse period. Also, due to imposing much energy to structure in during short period by these pulses, most of earthquake energy is absorbed in first made hinges instead of extension of non-linear behavior and plastic hinges in height of structure and the extension of non-linear behavior is not observed. This absorption of energy causes large relative inter-story displacements. Considering today’s using energy dissipation systems is current due to reducing earthquake vibrations of structures, which one of these energy dissipation systems are passive viscoelastic dampers. In these dampers which their energy dissipation mechanism depends on velocity of motion or in other words, on loading frequency and to be active these dampers there is no need to determined level of external excitation and they act in every earthquake. For this purpose, a number of structural models have been modeled in 2D form in "OpenSees" software for different damping ratios due to the added viscoelastic damper, non-linear dynamic analysis has been done under acceleration of horizontal earthquake and the amount of reduction of displacement response and base shear have been studied. تفاصيل المقالة -
حرية الوصول المقاله
256 - برآورد کشش واردات کالاهای واسطه ای با سایر عوامل تولید در ایران
سید یحیی ابطحی مهرجردی مهدی غلامی زارعیکی از بخشهای مهم هر اقتصاد، بخش تجارت خارجی است. از دوران انقلاب صنعتی به بعد و حتی پیش از آن،تجارت همواره اهمیت روزافزونی یافته و بر نقش آن در رشد و توسعه اقتصادی افزوده شده است. ایران نیز بهعنوان یک کشور صادر کننده نفت و واردکننده مواد اولیه، ماشین آلات، کالاهای سرما أکثریکی از بخشهای مهم هر اقتصاد، بخش تجارت خارجی است. از دوران انقلاب صنعتی به بعد و حتی پیش از آن،تجارت همواره اهمیت روزافزونی یافته و بر نقش آن در رشد و توسعه اقتصادی افزوده شده است. ایران نیز بهعنوان یک کشور صادر کننده نفت و واردکننده مواد اولیه، ماشین آلات، کالاهای سرمایهای وکالاهای واسطهایدر اقتصاد جهانی مطرح است. کشورمان به عنوان یک کشور در حال توسعه تاثیرپذیری زیادی از تجارت خارجیخود داشته است. در این مقاله سعی خواهد شد تا به بررسی واردات کالای واسطهای و تاثیر آن بر عوامل پرداختهشود. بنابراین با توجه به نقشی که واردات کالاهای واسطهای میتواند در ساختار تولید ایفا کند، در این تحقیق،تقاضای واردات کالای واسطهای به عنوان یکی از عوامل تولید در کنار سایر عوامل تولید در سیستم اقتصادیبرآورد شده است. در این راستا با استفاده از تابع ترانسلوگ برای محاسبه کششها به تخمین سهم هر یک ازعوامل تولید طی دورهی 7931 7931 پرداخته شد. نتایج حاکی از آن است که رابطهای جانشینی بین عوامل - تولید، یعنی واردات کالای واسطهای و سرمایه، واردات کالای واسطهای و نیرویکار، نیروی کار و سرمایه برقرار است. این مطلب نشان میدهد که با افزایش قیمت واردات واسطه )به عنوان یک عامل تولید( تقاضا برای آن کاهش مییابد و تولیدکننده داخل برای تولید آن کالا، اقدام نموده و سرمایه و نیروی کار بیشتری را تقاضا میکند. تفاصيل المقالة -
حرية الوصول المقاله
257 - Estimating an appropriate plastic concrete mixing design for cutoff walls to control leakage under the earth dam.
A Pashazadeh M Khosravi N GanjianMaking use of concrete materials in cut-off walls, because of their low permeability and standing high Hydraulic Gradient caused by underground drainage, has attracted great amount of attention. Using ordinary concrete with high elasticity modulus, compared to other mat أکثرMaking use of concrete materials in cut-off walls, because of their low permeability and standing high Hydraulic Gradient caused by underground drainage, has attracted great amount of attention. Using ordinary concrete with high elasticity modulus, compared to other materials may accompany with problems including brittleness of cutoffs due to dynamic stresses.To solve this problem, adding a certain percentage of clay (Bentonite) to plastic concrete materials reduces the concrete hardness as well as its elasticity coefficient, resulting in better ductility. Adding Ebonite (clay and excavation mud) decreases the possibility of hydraulic failure and cracking.In this article components of the plastic concrete and parameters which affect in properties and manners of its mixing design is analyzed. Based on the results that have been obtained from experiments on plastic concrete samples which have various mixing plans, diagrams have been presented to obtain a mixing plan of ideal plastic concrete with different characteristics which result in determining a key relationship in order to estimate mixing plan of an appropriate plastic concrete of cutoffs to control leakage under the dam. While under current situation, not using these relationships to estimate mixing plan of an appropriate plastic concrete of cutoffs in order to control leakage under the dam is costly and time consuming with considerable amount of errors. تفاصيل المقالة -
حرية الوصول المقاله
258 - Torsion of cylindrically poroelasic circular shaft with radial inhomogeneity .some exact solutions for extruder
mohammad farid khansanami Faranak KhansanamiTorsion of elastic and poroelastic circular shaft of radially inhomogeneous, cylindrically orthotropic materials is studied with emphasis on the end effects example for extruder. To examine the conjecture of Saint-Venant’s torsion, we consider torsion of circular s أکثرTorsion of elastic and poroelastic circular shaft of radially inhomogeneous, cylindrically orthotropic materials is studied with emphasis on the end effects example for extruder. To examine the conjecture of Saint-Venant’s torsion, we consider torsion of circular shaft with one end fixed and the other end free on which tractions that results in a pure torque are prescribed arbitrarily over the free end surface. Exact solutions that satisfy the prescribed boundary conditions point by point over the entire boundary surfaces are derived in a unified manner for cylindrically orthotropic shafts with or without radial inhomogeneity and for their coun- terparts of Saint-Venant’s torsion. Stress diffusion due to the end effect is examined in the light of the exact solutions.The present study enables us to assess Saint-Venant’s principle as applied to anisotropic, non-homogeneous poroelastic bodies in general and to evaluate the stress diffusion in torsion of radially inhomogeneous, cylindrically orthotropic cylinders in particular. The following conclusions can be drawn from the analysis. تفاصيل المقالة -
حرية الوصول المقاله
259 - Torsion of cylindrically poroelasic circular shaft with radial inhomogeneity .some exact solutions for extruder
محمد فرید خان سمنی فرانک خان سمنیTorsion of elastic and poroelastic circular shaft of radially inhomogeneous, cylindrically orthotropic materials is studied with emphasis on the end effects example for extruder. To examine the conjecture of Saint-Venant’s torsion, we consider torsion of circular s أکثرTorsion of elastic and poroelastic circular shaft of radially inhomogeneous, cylindrically orthotropic materials is studied with emphasis on the end effects example for extruder. To examine the conjecture of Saint-Venant’s torsion, we consider torsion of circular shaft with one end fixed and the other end free on which tractions that results in a pure torque are prescribed arbitrarily over the free end surface. Exact solutions that satisfy the prescribed boundary conditions point by point over the entire boundary surfaces are derived in a unified manner for cylindrically orthotropic shafts with or without radial inhomogeneity and for their coun- terparts of Saint-Venant’s torsion. Stress diffusion due to the end effect is examined in the light of the exact solutions.The present study enables us to assess Saint-Venant’s principle as applied to anisotropic, non-homogeneous poroelastic bodies in general and to evaluate the stress diffusion in torsion of radially inhomogeneous, cylindrically orthotropic cylinders in particular. The following conclusions can be drawn from the analysis تفاصيل المقالة -
حرية الوصول المقاله
260 - The Effect of Parameters of Winkler-Pasternak Elastic Foundations on Stress Analysis of Rectangular Plates Subjected to a Moving Load
احمدرضا خورشیدوند علی خیری امیر مسعود الله قلیIn this study, the stress analysis of rectangular plates resting on Winkler Pasternak model of elastic foundations under a movingconcentrated load with constant velocity and the impact of parameters related to the elastic foundations on normal stresses areinvestigated. أکثرIn this study, the stress analysis of rectangular plates resting on Winkler Pasternak model of elastic foundations under a movingconcentrated load with constant velocity and the impact of parameters related to the elastic foundations on normal stresses areinvestigated. The strain components are assumed to be linear and the Poisson’s ratio is kept constant. Based on first order sheardeformation theory (FSDT) and by employing Hamilton’s principle, the theoretical equations of motion and boundary conditionsare derived. Dimensionless discrete equations and boundary conditions have been achieved by using two dimensional generalizeddifferential quadrature method (DQM) and Newmark procedure. The convergence and accuracy of the present formulation andmethod of the solution, where possible, are demonstrated by comparing with the work of other investigators. With these results,the effect of Winkler foundation modulus and stiffness of Pasternak shear layer foundations on normal stresses of plates havebeen investigated. The analysis provides for both simply supported and clamped boundary conditions at edges. It is discoveredthat the Pasternak shear layer has a predominant influence over Winkler elastic modulus on the plates. تفاصيل المقالة -
حرية الوصول المقاله
261 - Non-Linear Analysis of Viscoelastic Rectangular Plates Subjected to In-Plane Compression
منوچهر صالحی امین صفی جهان شاهیGeometrically nonlinear governing equations for a plate with linear viscoelastic material are derived. The material model is of Boltzmann superposition principle type. A third-order displacement field is used to model the shear deformation effects. For the solution of أکثرGeometrically nonlinear governing equations for a plate with linear viscoelastic material are derived. The material model is of Boltzmann superposition principle type. A third-order displacement field is used to model the shear deformation effects. For the solution of the nonlinear governing equations the Dynamic Relaxation (DR) iterative method together with the finite difference discretization technique is used. Finally, the numerical results for the critical buckling load for simply supported edge constraints are reported. In order to justify the accuracy of the results, the elastic plate critical buckling loads are obtained and compared with the existing results. The correlations are very satisfactory. The numerical results are presented for Classical Plate Theory (CPT), First order- Shear Defonmation Plate Theory (FSDT) and Higher Order- Shear Deformation Plate Theory (HSDT). In the case of thick plate the differences among the three theories are highlighted, however, for thin plate the variations are very small. تفاصيل المقالة -
حرية الوصول المقاله
262 - Nonlinear Deformation Analysis and Modeling of Composite with Aluminum Layers
حبیب اسفندیار سعید ادیب نظری وحید منفرد علی خطیبFiber metal laminates (FMLs) are new composite materials consisting of thin metal layers and high strength composite layers. ARALL (Aramid aluminum laminate) is a family of the FML that consists of thin aluminum sheets along with Kevlar/epoxy composite layers. This mate أکثرFiber metal laminates (FMLs) are new composite materials consisting of thin metal layers and high strength composite layers. ARALL (Aramid aluminum laminate) is a family of the FML that consists of thin aluminum sheets along with Kevlar/epoxy composite layers. This material has many advantages such as light weight, excellent corrosion, fatigue and impact resistance. Since, ARALL is a new material, therefore presentation of a model for nonlinear behavior analysis is important. This paper presents the elastic– plastic behavior of ARALL under in- plane tensile loading. For this purpose, the orthotropic plasticity theory and modified classical laminated plate theory are used. In the orthotropic plasticity model, a three parameter plastic potential function is used. In the second theory, the Kevlar/epoxy composite layers and aluminum sheets are assumed to be linearly elastic and orthotropic elastic– plastic solids, respectively. Good agreement is obtained between results of two models. The results show that the case study behavior is almost bilinear under tensile loading and it has more strength in longitudinal direction in comparison to transverse direction. Variation of the Poisson’s ratio is considered in longitudinal and transverse loading too. تفاصيل المقالة -
حرية الوصول المقاله
263 - Load Controlled Fatigue of AZ31B
E. کلاته مولایی ح. جاهدWith the expanding demand on application of magnesium alloys in automotive and aerospace industries, robust methods in fatigue characterization of commercially available magnesium alloys with high specific strength is anticipated. In this paper, rotating bending load co أکثرWith the expanding demand on application of magnesium alloys in automotive and aerospace industries, robust methods in fatigue characterization of commercially available magnesium alloys with high specific strength is anticipated. In this paper, rotating bending load controlled tests has been studied on specimens machined from an extrusion piece of AZ31B. Due to asymmetric and anisotropic behavior of AZ31B, methods of transferring the load controlled results into stress-life results are lacking. Using the approach of variable material property (VMP), the load-stress relation in fully reversed test is derived. To apply the proposed method to AZ31B, the cyclic behavior of the material is required. Fully reversed step-loading of AZ31B over a wide range of strain amplitude was carried out on a servo hydraulic fatigue rig and was reported in the literature. The stabilized cyclic behavior at half-life was obtained for different load levels. Also, the cyclic tension and the cyclic compression curves were obtained. Using the proposed load-stress model and the actual cyclic behavior of AZ31B, an elastic-plastic solution over the whole domain of cross section was obtained. An energy based fatigue model was then employed to predict the life. The predicted and experimental lives agree well. The proposed method is recom-mended for correlating the load controlled test with stress and/or strain controlled tests. تفاصيل المقالة -
حرية الوصول المقاله
264 - Extraction of the governing equations for steady state and axisymmetric behavior of a porous piezoelectric circular solid plate
علی ابجدی محسن جباری احمد رضا خورشیدوندBased on the available evidence, porous piezoelectric materials have great potential for the development of smart (active) structures with high strength, high stiffness and light weight such as ceramics and composites. Among the ceramic materials with porous piezoelectr أکثرBased on the available evidence, porous piezoelectric materials have great potential for the development of smart (active) structures with high strength, high stiffness and light weight such as ceramics and composites. Among the ceramic materials with porous piezoelectric compounds, can be mentioned Lead-zirconate-titanate (PZT), Lead-titanate (PbTiO2), Lead-zirconate (PbZrO3), Barium-titanate (BaTiO3), Cadmium-selenide (CdSe), etc. This study extracts the governing partial differential equations for steady- state and axisymmetric behavior of a circular solid plate is made of an undrained saturated porous piezoelectric hexagonal material symmetry of class 6 mm. The porosities of the plate vary through the thickness; thus, material properties, except poisson’s ratio, are assumed as exponential functions of axial variable z in cylindrical coordinates. Additionally, piezothermoelastic behavior of a circular plate subject to external thermal, mechanical and electrical loads is considered, so various concepts including three-dimensional linear elasticity theory and dielectric theory are used in combination to create a linear piezoelectric model. The extraordinary and special industrial properties of porous piezoelectric materials, their increasing use and the need to know the behavior of these materials, doubles the importance of this research. تفاصيل المقالة -
حرية الوصول المقاله
265 - برآورد کشش‌های قیمتی و درآمدی گروه‌های مصرفی خانوارهای شهری با استفاده از سیستم تقاضای تقریباً ایده‌آل مبتنی بر داده‌های تابلویی
جمشید پژویان سید محمد مهدی احمدیهدف اصلی در این مقاله بررسی مخارج مصرفی خانوارهای شهری در ایران با استفاده از الگوی تقریب خطی سیستم تقاضای تقریباً ایده آل[i] (LA-AIDS) بر مبنای روش داده‌های تابلویی و استخراج کشش های قیمتی و درآمدی گروه‌های مدنظر است. برای این منظور 7 گروه از کالاها و خدمات شامل خوراکی أکثرهدف اصلی در این مقاله بررسی مخارج مصرفی خانوارهای شهری در ایران با استفاده از الگوی تقریب خطی سیستم تقاضای تقریباً ایده آل[i] (LA-AIDS) بر مبنای روش داده‌های تابلویی و استخراج کشش های قیمتی و درآمدی گروه‌های مدنظر است. برای این منظور 7 گروه از کالاها و خدمات شامل خوراکیها و آشامیدنیها، کفش و پوشاک، حمل و نقل، ارتباطات، هتل و رستوران و آب، برق، گاز و سایر سوختها و سایر گروهها در نظر گرفته شد و سهم هر یک با استفاده از روش رگرسیون به ظاهر نامرتبط و اطلاعات سالهای 1380 الی 139 برای 10 دهک هزینه‌ای در منطقه شهری برآورد شده است. نتایج حاکی از این است که کشش قیمتی این گروه‌های مصرفی مبتنی بر انتظارات تئوریکی و منفی است و شدت حساسیت این گروهها نسبت به تغییرات قیمت در دهک‌های بالای هزینه‌ای بیشتر است. کشش درآمدی بیانگر این است که گروه‌های خوارکیها و آشامیدنیها، کفش و پوشاک جزء کالاهای نرمال و ضروری و سایر گروه کالاهای نرمال و لوکس هستند Linear Approximate of Almost Ideal Demand System تفاصيل المقالة -
حرية الوصول المقاله
266 - امنیت غذایی در راستای ارتقای مصرف سرانه پروتئین حیوانی در برنامه چهارم توسعه کشور
محمد بخشوده فاطمه فتحیدر این پژوهش اثر تغییرات قیمت مصرفی و درآمد خانوارهای شهری را بر میزان دریافت پروتئین و کالری حیوانی به منظور ارتقای شاخصهای مربوط در برنامه چهارم توسعه مورد بررسی قرار می دهیم.با استفاده از روش تابع تقاضای تقریبا ایده آل درجه دو (QAIDS) در سالهای 1360-1386 کشش های خود أکثردر این پژوهش اثر تغییرات قیمت مصرفی و درآمد خانوارهای شهری را بر میزان دریافت پروتئین و کالری حیوانی به منظور ارتقای شاخصهای مربوط در برنامه چهارم توسعه مورد بررسی قرار می دهیم.با استفاده از روش تابع تقاضای تقریبا ایده آل درجه دو (QAIDS) در سالهای 1360-1386 کشش های خود قیمتی ،متقاطع درآمدی را محاسبه کرده و با استفاده از این نتایج کشش دریافت پروتئین و کالری خانوار شهری در اثر تغییر قیمت و درآمد را محاسبه قرار می دهیم.یافته ها نشان میدهد که تغییر قیمت گوشت مرغ بیشترین اثر را در دریافت پروتئین حیوانی دارد،همچنین کشش کالری گوشت مرغ بالاتراز محصولات پروتئینی دیگر است.کشش درآمدی پروتئین و کالری برای گروه کالاهای پروتئینی مثبت و برابر با 0.87 و 0.86 است،از این رو گروه کالاهای پروتئین به عنوان کالای نرمال به حساب می ایند. تفاصيل المقالة -
حرية الوصول المقاله
267 - مکانیزم انتقال قیمت و اثر آن بر حاشیه بازار ماهیان آب‌های جنوب ایران
مهدی سراوانی نظر دهمرده قلعه نونوسان و بی ثباتی قیمت محصول های شیلاتی یکی از مشخصات ناکارآمدی بازار این قبیل محصولات است. مطالعه حاضر به بررسی اثر انتقال قیمت بر حاشیه بازار ماهیان آب‌های جنوب کشور طی دوره زمانی ۱۳۸۳ تا ۱۳۹۳ با ترکیب متدولوژی هاک و فریگون و همکاران (۱۹۹۹) می پردازد. نتایج نشان می دهد أکثرنوسان و بی ثباتی قیمت محصول های شیلاتی یکی از مشخصات ناکارآمدی بازار این قبیل محصولات است. مطالعه حاضر به بررسی اثر انتقال قیمت بر حاشیه بازار ماهیان آب‌های جنوب کشور طی دوره زمانی ۱۳۸۳ تا ۱۳۹۳ با ترکیب متدولوژی هاک و فریگون و همکاران (۱۹۹۹) می پردازد. نتایج نشان می دهد برای ماهیان قباد، حلوا سفید، هامور، هور، راشکو، سنگسر، شیر، سرخو و حلوا سیاه فرضیه انتقال کامل افزایش قیمت ها از عمده‌فروشی به خرده‌فروشی رد شده است. در مورد ماهیان حلوا سفید، هور، سنگسر و سرخو تقارن کوتاه مدت و بلندمدت در انتقال قیمت رد شده لذا عدم تقارن در انتقال قیمت‌ها با افزایش حاشیه بازار سودهای نامتعارفی را نصیب واسطه ها می کند. نتایج کشش‌های انتقال قیمت ماهی‌های هور، سنگسر، سرخو و حلوا سفید نشان میدهد که افزایش قیمت در عمده‌فروشی این محصول ها با شدت بیشتری به سطح خرده‌فروشی منتقل می‌شوند درحالی‌که کاهش قیمت به کندی به سطوح بالاتر بازار انتقال می یابند. تفاصيل المقالة -
حرية الوصول المقاله
268 - عوامل موثر بر تقاضای گردشگری در ایران
تیمور محمدی مجتبی کریمی نگین نجارزاده معصومه شاه کرم اوغلیبا توجه به اهمیت درامد توریسم برای اقتصادهای فعلی در سطح جهان ،تحلیل تقاضای گردشگری و برآورد تابع تقاضای ان از اهمیت وافر برخوردار است.لذا در این مطالعه ضمن یررسی عوامل موثر بر تقاضای گردشگری به طور نظری بر اساس مدل تعدیل جزئی توابع کوتاه مدت و بلند مدت تقاضای توریسم در أکثربا توجه به اهمیت درامد توریسم برای اقتصادهای فعلی در سطح جهان ،تحلیل تقاضای گردشگری و برآورد تابع تقاضای ان از اهمیت وافر برخوردار است.لذا در این مطالعه ضمن یررسی عوامل موثر بر تقاضای گردشگری به طور نظری بر اساس مدل تعدیل جزئی توابع کوتاه مدت و بلند مدت تقاضای توریسم در ایران مورد برآورد قرار می گیرد.دوره مورد برآورد سالهای 1370-88 می باشد که به وسیله روش OLS تخمین ضرایب صورت گرفته است.نتایج حکایت از معنا داری تاثیر تولید ناخالص ملی جهانی و نرخ ارز حقیقی می باشد.کشش کوتاه مدت و بلند مدت تقاضای گردشگری نسبت به شاخص قیمت 0.59 و0.72 محاسبه شده است.از جمله نتایج این تحقیق عدم تاپیر هزینه حمل و نقل و تاثیر معنا دار تعداد گردشگران وارد شده به ایران و تولید ناخالص ملی جهانی و نرخ ارز حقیقی است. تفاصيل المقالة -
حرية الوصول المقاله
269 - A Novel Market Optimization Model in order to Minimizing Environmental Cost Caused by Plants
Mehdi Nourinezhad Soodabeh Soleymani Hosein Mohammadnezhad ShourkaeiNowadays generation capacity in traditional grid depends on fossil fuels and contributes significantly to the increase of pollution emission. In deregulated grids in addition to using demand response programs (DRPs) to reducing the cost of electricity production, peak c أکثرNowadays generation capacity in traditional grid depends on fossil fuels and contributes significantly to the increase of pollution emission. In deregulated grids in addition to using demand response programs (DRPs) to reducing the cost of electricity production, peak clipping and improve reliability use of green Plants such as hydro plant, wind plant become widespread. In a smart grid, end users according to their consumption, use one of the DRPs in reduction the cost of energy consumption as well as leads improvement in social welfare. DRPs change the normal pattern of end users consumption that these changes modeled in price elasticity matrix (PEM). The framework of this paper is reducing the cost of pollution generated by plants with a view to minimizing the overall system cost. The objective function presented in this paper is the overall system cost that presented a new method for modeling the DRPs in PEMs, cost of energy produced by independent power producers units and pollution contribute to the plants. The numerical calculation of this paper calculated in a Low voltage residential network and consumers use time of use program (TOU) for load management. The Load Serving Entities (LSEs) aggregate the reduced load compared to normal pattern and participate in the pay as bid (PAB) Stackelberg competition market that called demand side bidding. تفاصيل المقالة -
حرية الوصول المقاله
270 - A NOTE ON THE UNSTEADY FLOW OF A VISCO-ELASTIC MAXWELL FLUID THROUGH A RECTILINEAR PIPE
R. DubeThe unsteady flow of a visco-elastic Maxwell fluid through a rectilinear pipe having its cross-section as a parallelogram under the influence of a axial pressure gradient (I) varying linearly with time , and (II) decreasing exponentially with time has been discussed in أکثرThe unsteady flow of a visco-elastic Maxwell fluid through a rectilinear pipe having its cross-section as a parallelogram under the influence of a axial pressure gradient (I) varying linearly with time , and (II) decreasing exponentially with time has been discussed in the present paper. Variables separable and Laplace transform methods have been used to solve the problem. تفاصيل المقالة -
حرية الوصول المقاله
271 - PLANE WAVE PROPAGATION THROUGH A PLANER SLAB
Rajneesh KakarAn approximation technique is considered for computing transmission and reflection coefficients for plane waves propagating through stratified slabs. The propagation of elastic pulse through a planar slab is derived from first principles using straightforward time-depen أکثرAn approximation technique is considered for computing transmission and reflection coefficients for plane waves propagating through stratified slabs. The propagation of elastic pulse through a planar slab is derived from first principles using straightforward time-dependent method. The paper ends with calculations of enhancement factor for the elastic plane wave and it is shown that it depends on the velocity ratio of the wave in two different media but not the incident wave form. The result, valid for quite arbitrary incident pulses and quite arbitrary slab inhomogeneities, agrees with that obtained by time-independent methods, but uses more elementary methods تفاصيل المقالة -
حرية الوصول المقاله
272 - تحلیل ساختار هزینه گندم آبی با استفاده از تابع ترانسلوگ (مطالعه موردی استان کردستان)
الهامر پورمختار حامد قادرزادهمطالعه حاضر به بررسی ساختار ریاضی تابع هزینه و تولید محصول گندم آبی در استان کردستا می پردازد و اساس متدولوژی آن بر فرضیه دوگانگی استواراست. لذا ضمن اشاره به مزایای استفاده از تابع هزینه به جای تابع تولید در تجزیه و تحلیل تکنولوژی تولید، با انتخاب تابع هزینه ترانسلوگ، أکثرمطالعه حاضر به بررسی ساختار ریاضی تابع هزینه و تولید محصول گندم آبی در استان کردستا می پردازد و اساس متدولوژی آن بر فرضیه دوگانگی استواراست. لذا ضمن اشاره به مزایای استفاده از تابع هزینه به جای تابع تولید در تجزیه و تحلیل تکنولوژی تولید، با انتخاب تابع هزینه ترانسلوگ، طبق قضیه شفارد توابع تقاضای شرطی نهاده ها درچارچوب معادلات سیستمی به روش رگرسیون های به ظاهر نامرتبط تکراری به صورت مقید برآورد شدند. اندازه نمونه بالغ بر 257 بهره بردار گندم آبی است. داده ها برای سال زراعی91-90به صورت، پیمایشی و از طریق مصاحبه با کشاورزان و تکمیل پرسش نامه جمع آوری شده است. نمونه ها به روش نمونه گیری خوشه ای تصادفی چندمرحله ای انتخاب گردیدند. نتایج به دست آمده نشان می‌دهند که تابع هزینه ترانسلوگ برازش خوبی نسبت به داده های مورد تحقیق داشته است و فرضیه‌های ساختاری از جمله بازدهی ثابت نسبت به مقیاس، همگن بودن و هموتتیک بودن تکنولوژی تولید هیچ کدام از نظر آماری معنی دار نیستند. نهاده زمین بیشترین سهم ازهزینه تولیدرا به خود اختصاص می دهند. با توجه به نتایج حاصل از کشش های جانشینی آلن به جز نهاده های نیروی کار با سم و آب با کود بقیه از نوع جانشینی می باشد. همه کشش های قیمتی خودی تقاضا،کوچک تراز یک بوده، لذا می توان گفت تقاضا برای همه نهاده ها بی کشش است.همچنین برآورد معیار بازدهی نسبت به مقیاس بیان گر آن است که بازدهی نسبت به مقیاس فزاینده درمزارع مورد مطالعه، وجوددارد. تفاصيل المقالة -
حرية الوصول المقاله
273 - A Simulation Study on Impact of Climate Factors on Production and Requirements of Rice in Bangladesh
Md.AbuBakr Siddique Jun Furuya Shinataro Kobayashi M Abdus SalamMd. AbuBakr Siddique1*, Jun Furuya2, Shinataro Kobayashi2 ,M Abdus Salam1 1-Agricultural Economics Division, BRRI, Bangladesh 2-Development Research Division, Japan International Research Center for Agricultural Sciences *Corresponding author Email: abs_63@yaho أکثرMd. AbuBakr Siddique1*, Jun Furuya2, Shinataro Kobayashi2 ,M Abdus Salam1 1-Agricultural Economics Division, BRRI, Bangladesh 2-Development Research Division, Japan International Research Center for Agricultural Sciences *Corresponding author Email: abs_63@yahoo.com Received: 20 June 2013 Accepted:12 November 2013 Abstract Bangladesh is a disaster prone developing country, where people's staple food is rice. Numerous natural calamities visits here round the year, and impeded the crusade of development. This study was designed to evaluate the impact of climate change on supply and demand, as well as predict the future scenario of rice in Bangladesh. The findings of the study revealed that although, production of local varieties in aus, aman and boro season is decreasing owing to lower yield and shrinking of planted area aggregated production of rice is increasing due to higher production of modern varieties. As the total rice production increases quantity of imports is decreased in one hand and on the other hand, the bulk of stock is increased gradually. Higher level of per capita income growth rate leads to the diversification of consumers' food habit. Along with negative income elasticity of demand, decreased per capita consumption of rice including other food items in dietary system. However, total demand of rice will increase eventually as the population increasing. The enumerated results of simulation based on past trend and performance of data was very precise and reliable, and could be useful for future policy implications. تفاصيل المقالة -
حرية الوصول المقاله
274 - تاثیر مصرف کوتاه مدت مکمل کراتین مونوهیدرات به همراه تمرینات الاستیک بر عملکرد بازیکنان والیبال
فرحناز امیرشقاقی محسن میرعالی حمیدرضا رضائیهدف از پژوهش حاضر بررسی تاثیر مصرف کوتاه مدت مکمل کراتین مونوهیدرات به همراه تمرینات الاستیک بر بازیکنان والیبال بود. در یک کارآزمایی میدانی تعداد 50 نفر والیبالیست 30 تا 40 سال از جامعه آماری بعد از تکمیل پرسشنامه سلامتی به طور داوطلبانه به عنوان نمونه در پژوهش شرکت کر أکثرهدف از پژوهش حاضر بررسی تاثیر مصرف کوتاه مدت مکمل کراتین مونوهیدرات به همراه تمرینات الاستیک بر بازیکنان والیبال بود. در یک کارآزمایی میدانی تعداد 50 نفر والیبالیست 30 تا 40 سال از جامعه آماری بعد از تکمیل پرسشنامه سلامتی به طور داوطلبانه به عنوان نمونه در پژوهش شرکت کردند. آزمودنی‌ها به طور تصادفی به پنج گروه تمرین الاستیک و مکمل کراتین مونوهیدرات، تمرین الاستیک و دارونما، مکمل به تنهایی، گروه تمرین الاستیک و گروه کنترل تقسیم شدند. پروتکل تمرینی به مدت هشت هفته و هفته ای 3 جلسه انجام شد. مکمل سازی کراتین مونوهیدرات نیز هر روز 4 وعده به میزان 5 گرم در هر وعده بود. اندازه‌گیری توان هوازی با استفاده از آزمون 1 مایل (1609 متر) دویدن و توان بی هوازی با آزمون RAST مورد ارزیابی قرار گرفت. برای تجزیه و تحلیل داده های این پژوهش برای مقایسه میانگین های درون گروهی از روش آماری T وابسته و برای مطالعۀ اثر هشت هفته تمرین در پنج گروه از آزمون کوواریانس استفاده شد. برای تحلیل داده ها از نرم افزار SPSS 21 و برای رسم نمودارها از نرم افزار Exell 2010 استفاده شد. نتایج نشان داد که هشت هفته تمرین الاستیک همراه با مکمل دهی کراتین مونوهیدارت باعث بهبود معنادار توان هوازی و توان بی هوازی بازیکنان والیبال شده است (05/0 p ≤). با توجه به تاثیر مثبت مصرف مکمل کراتین و تمرین الاستیک بر عملکردهای هوازی و توانی که در منابع دیگر نیز به آن اشاره شده است به مربیان و ورزشکاران و مسئولان تغذیه تیم های ورزشی پیشنهاد می شود این ماده را با احتیاط در رژیم غذایی ورزشکاران بگنجاند .بویژه اینکه برای مصرف کوتاه مدت ان عوارض جانبی نیز گزارش نشده است. تفاصيل المقالة -
حرية الوصول المقاله
275 - Asymmetric buckling analysis of the circular FGM plates with temperature-dependent properties under elastic medium
علیرضا نداف اسکویی هادی محمدی هویه وحید علایی خداداد واحدیIn this paper, Asymmetric buckling analysis of functionally graded (FG) Circular plates with temperature dependent property that subjected to the uniform radial compression and thermal loading is investigated. This plate is on an elastic medium that simulated by Winkler أکثرIn this paper, Asymmetric buckling analysis of functionally graded (FG) Circular plates with temperature dependent property that subjected to the uniform radial compression and thermal loading is investigated. This plate is on an elastic medium that simulated by Winkler and Pasternak foundation. Mechanical properties of the plate are assumed to vary nonlinearly by temperature change. The equilibrium equations are obtained using the classical plate theory (CPT), Von Karman geometric nonlinearity and virtual displacement method. Existence of bifurcation buckling is examined and stability equations are obtained by means of the adjacent equilibrium criterion. The effects of elastic foundation coefficient, thickness to radius, power law index, and temperature-dependency of the material properties on critical buckling load of FG plates are presented. The results of the present work have been compared with the results of other investigator and the results of the comparison are very good. It is found that by increasing temperature, critical buckling load decreases. It is also concluded that the critical buckling load of (FG) Circular plates increases with an increase in the Winkler and Pasternak constants of elastic foundation. تفاصيل المقالة -
حرية الوصول المقاله
276 - Structural Analysis of Unsymmetric Laminated Composite Timoshenko Beam Subjected to Moving Load
Mohammad Javad RezvaniThe structural analysis of an infinite unsymmetric laminated composite Timoshenko beam over Pasternak viscoelastic foundation under moving load is studied. The beam is subjected to a travelling concentrated load. Closed form steady state solutions, based on the first-or أکثرThe structural analysis of an infinite unsymmetric laminated composite Timoshenko beam over Pasternak viscoelastic foundation under moving load is studied. The beam is subjected to a travelling concentrated load. Closed form steady state solutions, based on the first-order shear deformation theory (FSDT) are developed. In this analysis, the effect of bend-twist coupling is also evaluated. Selecting of an appropriate displacement field for deflection of the composite beam and using the principle of total minimum potential energy, the governing differential equations of motion are obtained and solved using complex infinite Fourier transformation method. The dynamic response of unsymmetric angle-ply laminated beam under moving load has been compared with existing results in the literature and a very good agreement is observed. The results for variation of the deflection, bending moment, shear force and bending stress are presented. In addition, the influences of the stiffness, shear layer viscosity of foundation, velocity of the moving load and also different thicknesses of the beam on the structural response are studied. تفاصيل المقالة -
حرية الوصول المقاله
277 - Free Vibration Analysis of Sandwich Micro Beam with Piezoelectric Based on Modified Couple Stress Theory and Surface Effects
Mohammad khajekhabaz Ali Eftekhari Mohammad HashemianIn this paper, the free vibration analysis of sandwich micro beam with piezoelectric layers based on the modified couple stress and surface elasticity theories are investigated. The Hamilton’s principle is employed to derive the sandwich micro beam with piezoelect أکثرIn this paper, the free vibration analysis of sandwich micro beam with piezoelectric layers based on the modified couple stress and surface elasticity theories are investigated. The Hamilton’s principle is employed to derive the sandwich micro beam with piezoelectric based on modified couple stress theory incorporating with Gurtin- Murdoch surface theory. The generalized differential quadrature method is used to discretize the partial differential equation into the ordinary differential equation. The effect of various parameters such as thickness to material length scale parameter ratio, the surface residual stress, Young's modulus of surface layer, surface mass density and surface piezoelectric constant are investigated by comparing the results obtained using the modified couple and classical theories. Numerical results of this problem evaluate the effect of micro length scale parameters on natural frequency. The results show that surface parameter effects are significant when the model is small, but can be neglected with increasing model size. تفاصيل المقالة -
حرية الوصول المقاله
278 - Dynamic stability analysis of functionally graded Euler-Bernoulli nanobeams under a sequence of moving nanoparticle based on nonlocal elasticity theory
Rahman Khanahmadi Mohammad Hashemian Mostafa PirmoradianThis study investigates the dynamic stability of the Euler-Bernoulli functionally graded (FGM) nanobeam based on the nonlocal elasticity theory while considering surface effects. Nanoparticles pass over nanobeam sequentially with a constant velocity, and the nanoparticl أکثرThis study investigates the dynamic stability of the Euler-Bernoulli functionally graded (FGM) nanobeam based on the nonlocal elasticity theory while considering surface effects. Nanoparticles pass over nanobeam sequentially with a constant velocity, and the nanoparticle inertia is also considered. A thermal gradient with constant temperature changes is applied to this nanobeam. The functionally graded nanobeam properties, including Young’s modulus, density, surface residual stress, and surface modulus are taken by the power law. The classical equations of motion are obtained by applying the Hamilton’s principle according to the energy method. The governing equations are extracted using nonlocal elasticity theory, and the surface effects are taken by Gurtin-Murdoch theory. The dynamic stability graphs will be presented on nanoparticle mass-velocity coordinates. This article investigated the small scale effect parameter, temperature changes, Pasternak environment shearing and elastic constants, and the volume fraction parameter in power law. The results show that increasing Pasternak foundation constants increase the functionally graded nanobeam stability, and increasing small scale parameter reduces its stability. Increasing nanobeam temperature shifts the functionally graded stability region of nanobeam towards faster nanoparticle velocity, which indicates a higher dynamic stability for the nanobeam. تفاصيل المقالة -
حرية الوصول المقاله
279 - The influence of various boundary conditions on dynamic stability of a beam-moving mass system
Ramin Motiei Mostafa Pirmoradian Hossein KarimpourIn this paper, the effect of different boundary conditions on dynamic stability of a beam located on a viscoelastic medium stimulated by moving masses and periodic axial force is studied. Partial differential equations governing the system are derived using Hamilton's m أکثرIn this paper, the effect of different boundary conditions on dynamic stability of a beam located on a viscoelastic medium stimulated by moving masses and periodic axial force is studied. Partial differential equations governing the system are derived using Hamilton's method and based on Euler-Bernoulli beam theory. Then, equations are converted into a set of ordinary differential equation with time-varying coefficients using Galerkin method along with trigonometric shape functions. The time-varying position of moving loads causes these time-varying coefficients in the governing equations. By applying Floquet's theory to the obtained equations, the conditions of parametric resonance are analyzed for different values of mass and velocity of passing loads. The results obtained from this research show that the stiffness and viscosity of the elastic medium have positive effects on the stability of the beam under moving and fluctuating axial loads. So, with a suitable choice for these values in practical applications, it is possible to prevent unexpected vibrations of the structure. In addition, the use of fixed supports for the two ends of the beam exposed to the mentioned loadings has high reliability in the discussion of dynamic stability. تفاصيل المقالة -
حرية الوصول المقاله
280 - Molecular simulation for prediction of mechanical properties of polylactic acid polymer for biotechnology applications
Amin Mansouri Ali Heidari Fatemeh Karimian Amir Mohammad Gholami Mehran Latifi Sheyda ShahriariDevelopment of materials for use in medicine and industries is one of the biggest challenges in research in materials science. Today, absorbable, biocompatible and biodegradable polymers have been identified to be used as alternative materials for biomedical application أکثرDevelopment of materials for use in medicine and industries is one of the biggest challenges in research in materials science. Today, absorbable, biocompatible and biodegradable polymers have been identified to be used as alternative materials for biomedical applications. Among the biomaterials used in medical fields, polylactic acid (PLA) have been considered widely. This polymer obtained from completely renewable sources and due to their good physicochemical properties in various industries it is highly recommended. The purpose of this study was to introduce PLA mechanical properties using molecular dynamics (MDs) simulation. The special advantage of PLA over other polymers is its biodegradation, which is generally degraded by a single-step process involving a bacterial attack on the polymer itself. It is easily degraded in atmospheres with high humidity and temperatures of 50-70°C. However, at lower temperatures or lower humidity, the stability of PLA products is higher. The MD analysis indicates that the density value corresponds well to the experimental values. Based on the molecular model, the elastic modulus properties of the model were investigated. In this study, the average elastic modulus of the molecular PLA model was calculated to be about 2.2 GPa. تفاصيل المقالة -
حرية الوصول المقاله
281 - Stabilized crack-opening stresses as a function of R-ratios and stress levels
Rahi Chermahini Majid JabbariAn elastic-perfectly plastic middle crack tension aluminum 2024-T3 alloy was used under plane stress, plane strain and 3D analysis to determine stabilized crack-opening stresses for different R-ratios and stress levels. The stabilized crack-opening stresses of a 3D anal أکثرAn elastic-perfectly plastic middle crack tension aluminum 2024-T3 alloy was used under plane stress, plane strain and 3D analysis to determine stabilized crack-opening stresses for different R-ratios and stress levels. The stabilized crack-opening stresses of a 3D analysis locate between those values of plane stress and plane strain conditions. Using the above strategy, one can determine crack-opening stresses for any desired thickness value using interpolating scheme. Two and three dimensional programs were developed based on small strain elasticity theory incorporating linear strain isoparametric elements. The plasticity part of the analysis uses initial stress approach. The crack was extended one element size as the applied load reached the maximum value of each load cycle. Crack opening and closure stresses of nodes on the crack surface plane after some cyclic crack extensions are demonstrated. Based on the obtained results, for the three-dimensional finite-element analysis, the calculated stabilized crack opening stresses always locate between those of plane stress and plane strain conditions. تفاصيل المقالة -
حرية الوصول المقاله
282 - Mathematical Analysis of Shearing Viscoelastic Beam Subjected to Continuous Moving Load
محمد طهرانی حمیدرضا ایپک‌چیIn this paper, the dynamic response of a viscoelastic beam subjected to a moving distributed load has been studied. The viscoelastic properties of the beam have been considered as linear standard model in shear and incompressible in bulk. The stress components have been أکثرIn this paper, the dynamic response of a viscoelastic beam subjected to a moving distributed load has been studied. The viscoelastic properties of the beam have been considered as linear standard model in shear and incompressible in bulk. The stress components have been separated to the shear and dilatation components and as a result the governing equations in viscoelastic form has been obtained using direct method. These equations have been solved by the eigenfunction expansion method. In this research, according to the introduced dimensionless coefficients, a parametric study has been presented and the effects of the load velocity and viscoelastic materials have been investigated. The obtained results show the maximum decay corresponds to the cases that the first natural period equals totimes that the relaxation time. تفاصيل المقالة -
حرية الوصول المقاله
283 - Vibration Analysis of Timoshenko Beam reinforced with Boron-Nitride Nanotube on Elastic Bed
ایلدا عبداللهی محمدحسین یاسIn this paper, free vibration analysis of a polymer-based nano-composite beam reinforced by boron-nitride nanotubes and subjected on elastic foundation, is studied. Smooth and defect-free nanotubes with uniform and directly- orientated in matrix are intended. Also, nano أکثرIn this paper, free vibration analysis of a polymer-based nano-composite beam reinforced by boron-nitride nanotubes and subjected on elastic foundation, is studied. Smooth and defect-free nanotubes with uniform and directly- orientated in matrix are intended. Also, nanotubes’ distribution in the thickness direction of beam is regarded as a uniform distribution of the three different targeted ones. The properties of nano-beam are obtained by using a micromechanical model. The governing equations based on Timoshenko beam theory are derived by using the Hamilton principle. The equations are solved by the extended differential Quadrature and the natural frequencies are obtained. The effect of various parameters such as volume fraction of nanotubes, carbon-nanotube (CNT) distribution in the thickness direction of the beam, elastic media, boundary conditions and the aspect ratio is investigated on the natural frequency. The results show that a change on these parameters has a significant impact on the natural frequency. تفاصيل المقالة -
حرية الوصول المقاله
284 - Modified Fixed Grid Finite Element Method to Solve 3D Elasticity Problems of Functionally Graded Materials
محمد جواد کاظم زاده پارسی فرهنگ دانشمندIn the present paper, applicability of the modified fixed grid finite element method in solution of three dimensional elasticity problems of functionally graded materials is investigated. In the non-boundary-fitted meshes, the elements are not conforming to the domain b أکثرIn the present paper, applicability of the modified fixed grid finite element method in solution of three dimensional elasticity problems of functionally graded materials is investigated. In the non-boundary-fitted meshes, the elements are not conforming to the domain boundaries and the boundary nodes which are used in the traditional finite element method for the application of boundary conditions no longer exist. Therefore, special techniques are needed for computation of the stiffness matrix of boundary intersecting elements and application of boundary conditions.The stiffness matrix of boundary intersecting elements are calculated via integration of strain energy over the internal parts of these elements. Essential boundary conditions are applied using penalty function method. To examine the effectiveness of the proposed method, some numerical examples are solved and results are compared with those obtained using the standard finite element method. تفاصيل المقالة -
حرية الوصول المقاله
285 - Free Vibration of Annular Plate Reinforced with Multi-walled Carbon Nanotubes Resting on an Elastic Foundation Using Refined Theory
مسعود رضایی حمید محسنی منفرد سید علیرضا مهاجرانیIn this paper, an attempt is made for solution of free vibration analysis of annular plate reinforced with carbon nanotubes for Uniformly Distribution (UD), resting on an elastic foundation using a refined theory presented. In this theory, a parabolic distribution of sh أکثرIn this paper, an attempt is made for solution of free vibration analysis of annular plate reinforced with carbon nanotubes for Uniformly Distribution (UD), resting on an elastic foundation using a refined theory presented. In this theory, a parabolic distribution of shear stress and strain in the thickness direction and satisfies the boundary conditions of zero shear stress on the upper and lower crust cut without using a correction factor to be considered. The equations of motion are obtained using Hamilton's principle. And then these equations are solved by GDQ method .Factors affecting the frequency such large radius to small radius, the ratio of thickness to the radius of the annular plate, the length of the radius is obtained. To check the compatibility equations and solving method is used, a comparison between the present work has been done with papers تفاصيل المقالة -
حرية الوصول المقاله
286 - Study of the Effects of Various Boundary Conditions on the Acoustical Treatments of Double-Panel Structures Lined with Poroelatic Materials
محمدحسن شجاعی فرد روح ا... طالبی رضا احمدی مائده امیرپور ملاIn this paper, the acoustical treatment of double-panel structures lined with poroelatic materials is predicted using analytical method in order to study the effective usage of the various boundary conditions of porous layer and to identify the effective parameters on t أکثرIn this paper, the acoustical treatment of double-panel structures lined with poroelatic materials is predicted using analytical method in order to study the effective usage of the various boundary conditions of porous layer and to identify the effective parameters on the transmission loss of the multilayer systems. Therefore, inertia and viscous coupling along with thermal and elastic coupling should be considered in transfer stress dynamic and stress-strain relationships for an elastic porous material based on Biot theory. Then, the governing equations of the wave propagation in an elastic porous material are briefly considered and the general forms for the stresses and displacements within the porous material are given. Applying various boundary conditions and solving these equations with Matlab code simultaneously, the transmission loss of these structures is calculated. The results from the analytical method are compared with the SEA madel and the experimental data with excellent agreement is observed. Finally, the influence of effective parameters of this structure with various boundary conditions on the transmission loss of the multilayer systems is studied. The results have been shown that the transmission loss of double-panel structures lined with a layer of porous material can depend critically on the method of mounting the porous layer to the facing panel. تفاصيل المقالة -
حرية الوصول المقاله
287 - Resolution composite shell with a layer of piezoelectric vibration analysis
اکبر علی بیگلو عبدالمجید کنیIn this paper, the vibration of composite cylindrical shell with piezoelectric layers in the interior and exterior surfaces is investigated. The composite shell without piezoelectric layers can be studied and compared the results with the results of other researchers, t أکثرIn this paper, the vibration of composite cylindrical shell with piezoelectric layers in the interior and exterior surfaces is investigated. The composite shell without piezoelectric layers can be studied and compared the results with the results of other researchers, the cylindrical shell laminated with layers of piezoelectric vibration checked. The result is a three-dimensional elasticity equations relationships because they do not apply any approximate gain are quite analytical. Shells intended, is closed and has restricted the mainstays in the end it was simple, and the results for the ratio of the radius and the radius of the different thickness are obtained تفاصيل المقالة -
حرية الوصول المقاله
288 - Applying Differential Transform Method on the Effect of the Elastic Foundation on the out - Plane Displacement of the Functionally Graded Circular Plates
سمیه عباسی فاطمه فرهت نیا سعید رسولی جزیIn this paper, the effect of elastic foundation on the out of plane displacement of functionally graded circular plates using differential transform method is presented. Differential transform method is a semi-analytical-numerical solution technique that is capable to s أکثرIn this paper, the effect of elastic foundation on the out of plane displacement of functionally graded circular plates using differential transform method is presented. Differential transform method is a semi-analytical-numerical solution technique that is capable to solve various types of differential equations. Using this method, governing differential equations are transformed into recursive relations and boundary conditions are changed into algebraic equations. Since the problem of plates on elastic foundation have a great practical importance in modern engineering structures and Winkler foundation model is widely used, plate is assumed on Winkler elastic foundation. In this article functionally graded plate is considered in which material properties vary through the thickness direction by power-law distribution. Analysis results of out of plane displacement of plate on elastic foundation under uniform transverse loads are obtained in different terms of foundation stiffness, material properties and boundary conditions. In order to validate the solution technique, results obtained are compared with the results of the finite element method (FEM). تفاصيل المقالة -
حرية الوصول المقاله
289 - Thermal Effect on the Torsional Buckling of Double Walled Carbon Nanotube Embedded in Pasternak Foundation
علی قربانپور آرانی محمد شریف زارعی مهدی محمدی‌مهرIn this study the effect of thermal stress on the torsional buckling of double walled carbon nanotubes is investigated. Moreover based on nonlocal continuum mechanic the buckling governing equations are obtained and equilibrium of Equations is generalized to double wall أکثرIn this study the effect of thermal stress on the torsional buckling of double walled carbon nanotubes is investigated. Moreover based on nonlocal continuum mechanic the buckling governing equations are obtained and equilibrium of Equations is generalized to double wall nanotubes. Also in this study the elastic medium, small scale effect and van der Walls force are considered. Also for simulation of the interaction between the polymer matrix and external tube Pasternak model is used. The numerical results indicate that critical buckling load occurs in the middle modes. Moreover for the Winkler related the Pasternak model the buckling occurs earlier. Results show that for rigid elastic medium in both case of Pasternak and Winkler models the buckling load is independent of their values Moreover from the result it can be seen that the buckling load has been increase as the thermal effect change. تفاصيل المقالة -
حرية الوصول المقاله
290 - A Survey on Buckling and Vibrations of a Viscoelastic Beam under Distributed Lateral and Axial Loads
حمید رضا ایپک چی حمیده صدیقیIn this paper, based on Kelvin and Linear Standard Solid models, dynamic response and the buckling load of a viscoelastic beam under lateral and axial loads have been determined. The governing equations have been extracted using Euler and Timoshenko theories and their a أکثرIn this paper, based on Kelvin and Linear Standard Solid models, dynamic response and the buckling load of a viscoelastic beam under lateral and axial loads have been determined. The governing equations have been extracted using Euler and Timoshenko theories and their analytical solutions have been obtained by using the eigenfunctions expansion method. Buckling load have been calculated by using the Euler and Timoshenko beam theories based on Kelvin and standard models. The results have been compared with the elastic case. The results show that the simulation of a viscoelastic beam with an elastic case, is not a reasonable approximation for moderately high damping. Also, the damping parameter has not been appeared explicitly in the buckling load determination, even though the buckling load of a viscoelastic beam is 50% more than an elastic beam. تفاصيل المقالة -
حرية الوصول المقاله
291 - Non-linear Static Modeling of Moderately Thick Functionally Graded Plate Using Dynamic Relaxation Method
محمدجواد محمودی وحید محلوجیIn this paper, nonlinear static analysis of moderately thick plate made of functionally graded materials subjected to mechanical transverse loading is carried out using dynamic relaxation method. Mindlin first order shear deformation theory is employed to consider thick أکثرIn this paper, nonlinear static analysis of moderately thick plate made of functionally graded materials subjected to mechanical transverse loading is carried out using dynamic relaxation method. Mindlin first order shear deformation theory is employed to consider thick plate. Discretized equations are extracted for geometrically nonlinear behavior analysis.Loading Conditions and boundary conditions of the plate are uniformly distributed transverse load and simply supported at the four edges of the thick plate, respectively. In order to generalize the obtained results, the equations are solved by applying dynamic relaxation method based on central finite deference discretization in the non-dimensional form. The effects of problem parameters such as gradient constant of the functionally graded material and the side to thickness ratio of plate on the results are investigated. According to the obtained results, the need of including elastic large deflection and applying the theory which considers the effects of plate thickness on the plate bending response and also finally the need of employing dynamic relaxation solution method despite the non-linear terms resulted from large deflection of the functionally graded thick plate are discussed. تفاصيل المقالة -
حرية الوصول المقاله
292 - Investigation of Linear and Nonlinear Buckling of Orthotropic Graphene Sheets with Nonlocal Elasticity Theories
مصطفی صادقیان مهرداد جبارزادهIn this paper, analysis of linear and nonlinear buckling of relatively thick orthotropic graphene sheets is carried out under mechanical load based on elasticity theories. With the help of nonlocal elasticity theory, the principle of virtual work, first order shear theo أکثرIn this paper, analysis of linear and nonlinear buckling of relatively thick orthotropic graphene sheets is carried out under mechanical load based on elasticity theories. With the help of nonlocal elasticity theory, the principle of virtual work, first order shear theory and Von-Karman nonlinear strain, the dominant relationship in terms of obtained displacements has been obtained, and the method of differential quadrature (DQ) with non-uniform distribution points (Chebyshev -Gauss-Lobato) has been used. To check the validity, the obtained results have been compared with other resources, and the effects of nonlocal coefficient, thickness, radius and elastic base on the dimensionless buckling loads were calculated and investigated. Moreover, the results of analysis using nonlocal and local theory were compared together. It can be noticed that the dimensionless buckling loads on graphene sheets increased more with a decrease in flexibility as far boundary condition is concerned. Additionally, with an increase in the sheet radius, the variation between nonlocal and local analysis results will be more. تفاصيل المقالة -
حرية الوصول المقاله
293 - Nonlocal Mechanical Buckling Analysis of Nano Single Layer Sheets Using Differential Quadrature method
M. Sadeghian M. JabbarzadehThe following article investigates buckling of moderately thick circular Nano plates with an orthotropic property under uniform radial compressive in-plane mechanical load. Taking into account nonlocal elasticity theory (Eringen), principle of virtual work, first order أکثرThe following article investigates buckling of moderately thick circular Nano plates with an orthotropic property under uniform radial compressive in-plane mechanical load. Taking into account nonlocal elasticity theory (Eringen), principle of virtual work, first order shear deformation plate theory (FSDT) and nonlinear Von-Karman strains, the governing equations are obtained based on displacements. The stability equations are derived from the neighbor equilibrium estate. The differential quadrature method (DQM) as a numerical procedure is applied to discretize the derivatives equations with a non-uniform mesh point distribution (Chebyshev-Gauss-Lobatto). The accuracy of the present results is validated by comparing the solutions with those reported by the available literatures. The effect of nonlocal parameter, thickness and radius are investigated on non-dimension buckling loads. From the results, it can be seen that the non-dimension buckling load of Graphene sheets increases by decreasing flexibility of boundary condition and increasing the rate of nonlocal parameter. It can be observed that with increasing the non-dimensional thickness of plate, the non-dimension buckling loa reduces تفاصيل المقالة -
حرية الوصول المقاله
294 - Influence of Elastic Support on the Energy Absorption in Front Crash Ductile Failure Criterion
حسین خانجانی احمد کشاورزیThin-walled structures like crash boxes may be used as energy absorption members in automotive chassis. There have been many studies addressing the behaviors of energy absorption members on frontal crash. These researches have attempted to predict the energy absorption أکثرThin-walled structures like crash boxes may be used as energy absorption members in automotive chassis. There have been many studies addressing the behaviors of energy absorption members on frontal crash. These researches have attempted to predict the energy absorption and maximum impact load in shell structures. The energy absorption and maximum impact load depend on many parameters including boundary condition, strain rate, history of plastic deformation during metalworking, geometry; and material and impact energy (i.e. mass and velocity of the striker). This study examined the crash behavior of tube made of the extruded aluminum alloy EN AW-7108 T6 using an elastic boundary condition instead of rigid boundary condition- on the bottom of a crash box. Analytical, Numerical analytical methods is used in this study to simulated crash box behavior, Results showed that using elastic boundary could change the deformation mode and decrease the maximum impact load تفاصيل المقالة -
حرية الوصول المقاله
295 - Bending Analysis of Carbon Nanotubes with Small Initial Curvature Embedded on an Elastic Medium Based on Nonlocal Elasticity and Galerkin Method
اعظم عارفی محمود سلیمیCarbon nanotubes have an important role in reinforcing nanocomposits. Many experimental observations have shown that in the most nanostructures such as nanocomposites, carbon nanotubes (CNTs) are often characterized by a certain degree of waviness along their axial dire أکثرCarbon nanotubes have an important role in reinforcing nanocomposits. Many experimental observations have shown that in the most nanostructures such as nanocomposites, carbon nanotubes (CNTs) are often characterized by a certain degree of waviness along their axial direction. In the present paper, the effects of initial curvature, influence of surrounding medium that is modeled as Winkler elastic foundation on behavior of slightly curved carbon nanotubes are investigated. To capture the small size effects, nonlocal elasticity theory is implemented. Bending governing equations are derived using the principle of minimum total potential energy and these nonlinear equations are solved by Newton Raphson method. It is shown that the larger the initial curvature, the higher deflection can occur. Furthermore, neglecting the effect of initial curvature of CNTs can lead to incorrect results. تفاصيل المقالة -
حرية الوصول المقاله
296 - Bending Sector Graphene Sheet Based on the Elastic Winkler-Pstrnak with the Help of Nonlocal Elasticity Theory Using Developed Kantorovich Method
شهریار دستجردی مهرداد جبارزادهIn this study, the elastic bending of sector graphene sheet has been studied based on elasticity using Eringen Nonlocal Elasticity Theory. In order to do this, the balance equations governing the sector graphene sheet have been solved in terms of displacements with rega أکثرIn this study, the elastic bending of sector graphene sheet has been studied based on elasticity using Eringen Nonlocal Elasticity Theory. In order to do this, the balance equations governing the sector graphene sheet have been solved in terms of displacements with regard to nonlocal relationship of stress, shear theory of the first order, and obtained linear strains using developed Kantorovich method. In this method, the obtained partial differential equations are converted into two categories that can be solved using analytical and numerical methods. Developed Kantorovich method is a method with a high rate of convergence, in which the expected convergence is achieved with just three to four repetitions. With regard to the fact that no research has yet been conducted in this regard, the results, considering the nonlocal coefficient equal to zero, have been compared with other articles in order to check the validity. In the end, the effect of nonlocal coefficient variations on the results in terms of thickness, boundary conditions, hardness of elastic base and difference between nonlocal and local elasticity analysis has been studied. تفاصيل المقالة -
حرية الوصول المقاله
297 - Stress Analysis of Magneto Thermoelastic and Induction Magnetic Filed in FGM Hallow Sphere
حسن خادمی زاده علی قربان پور آرانی محمد سالاریIn this paper a closed form solution for one-dimensional magnetothermoelastic problem in a functionally graded material (FGM) hollow sphere placed in a uniform magnetic field and temperature field subjected to an internal pressure is obtained using the theory of magneto أکثرIn this paper a closed form solution for one-dimensional magnetothermoelastic problem in a functionally graded material (FGM) hollow sphere placed in a uniform magnetic field and temperature field subjected to an internal pressure is obtained using the theory of magnetothermoelasticity. Hyper-geometric functions are employed to solve the governing equation. The material properties through the graded direction are assumed to be nonlinear with an exponential distribution. The nonhomogeneity of the material in the radial directions is assumed to be power-exponential. The temperature, displacement and stress fields and the perturbation of magnetic field vector are determined and compared with those of the homogeneous case. Hence, the effect of inhomogeneity on the stresses and the perturbation of magnetic field vector distributions are demonstrated. The results of this study are applicable for designing optimum FGM hollow spheres. تفاصيل المقالة -
حرية الوصول المقاله
298 - Nonlinear Finite Element Analysis of Thermoelastic Stresses of FGM Rotating Disk Considering Temperature-Dependency of Material Properties
مهرنوش دمیرچلی محمد آزادیIn the present paper, nonlinear radial and hoop thermoelastic stresses analysis of a disk made of FGMs material is investigated. According to this purpose, finite element method is used. In the present method, second-order one-dimensional element (with three node points أکثرIn the present paper, nonlinear radial and hoop thermoelastic stresses analysis of a disk made of FGMs material is investigated. According to this purpose, finite element method is used. In the present method, second-order one-dimensional element (with three node points) is proposed. The geometrical and stress boundary conditions are defined in the state of non-existence of external pressure and then zero radial stress in the outer layer of the disk, and zero displacement in the center of the disk. Also the temperature distribution is assumed as linear. The material properties changes including temperature-dependency are modeled. Finally, a numerical example is proposed to show the radial displacements, radial and hoop thermoelastic stresses versus radius of the disk for different power (N) from Power-law and different angular velocities. The results show that by increasing both two parameters, N and angular velocity of the disk, the amounts of displacement and stress are increased. At last, temperature-dependency and temperature-independency of material properties is investigated. تفاصيل المقالة -
حرية الوصول المقاله
299 - Analysis of Bending and Buckling of Circular Porous Plate Using First-Order Shear Deformation Theory
A.R. Yadegari Naeini Yadegari Naeini A. GhasemiPorous materials are lightweight, flexible and resistant to hairline cracks, so today with the development of technology porous structure produced for use in various industries. This structure widely use in beams, plates and shells. The purpose of this paper is to inves أکثرPorous materials are lightweight, flexible and resistant to hairline cracks, so today with the development of technology porous structure produced for use in various industries. This structure widely use in beams, plates and shells. The purpose of this paper is to investigate the effect of porosity in axial symmetry in bending and buckling load sheet for analysis. For this purpose, a circular plate with simply supported edges under uniform radial pressure and vertical pressure distribution is investigated. Mechanical properties of porous sheet are isotropic and variable in thickness direction is considered. Right movement is extended in accordance with the first order shear deformation theory. Then, using the principle of virtual work and applying the calculus of variations, differential equations, and equations for bending sheet stability are achieved, continue using these equations and Galerkin method, bending and buckling of the sheet is calculated. Buckling load is calculated for all types of porosity can be observed with increasing porosity, critical buckling load decreases. Buckling load is calculated for all types of porosity can be observed with increasing porosity, critical buckling load decreases. The distribution of bending stress and deflection analysis sheet was obtained. To verify the results of bending and buckling of the sheet, the results were compared with homogeneous sheet with classical theory. تفاصيل المقالة -
حرية الوصول المقاله
300 - Nonlinear Vibration Analysis of Composite Plates with SMA Wires, Considering Instantaneous Variations of the Martensite Volume Fraction
محمد شرعیات سارا سمایی مجتبی مرادیIn the past few years, extensive improvements have been accomplished in reinforcing the structures through using shape memory alloys (SMAs). These materials absorb or dissipate energy through establishing a reversible hysteresis loop during a cyclic mechanical loading. أکثرIn the past few years, extensive improvements have been accomplished in reinforcing the structures through using shape memory alloys (SMAs). These materials absorb or dissipate energy through establishing a reversible hysteresis loop during a cyclic mechanical loading. This unique characteristic of the SMAs has made them appropriate for sensing, actuation, absorbing the impact energy, and vibration damping applications. Instantaneous and local variations of the phases of the SMA wire in the successive loading and unloading events of the vibration have not been accurately investigated by the works published so far. In the present paper, vibrations of composite plates reinforced by SMA wires are investigated, by employing an algorithm that overcomes the mentioned shortcomings. Governing equations are derived based on the Hamilton’s principle and the first-order shear-deformation plate theory. Furthermore, Brinson’s constitutive equations are used to model material properties of the SMA and the time-dependent partial deferential equations are solved using Newmark’s numerical time integration method. The governing equations are solved by a finite element code written in MATLAB software. In the present research, the influence of the instantaneous variations of the volume fraction of the Martensite volume fraction due to variations of the stress components on the material properties of the SMA, hybrid composite, and the recovery load is considered for the first time. Finally, effect of the volume fraction of the SMA wires of each layer and the influence of the amplitude of the abruptly applied load on the vibration behavior of the composite plate is investigated, too. تفاصيل المقالة -
حرية الوصول المقاله
301 - Vibration Analysis of Thick Functionally Graded Beam under Axial Load Based on Two-Dimensional Elasticity Theory and Generalized Differential Quadrature
حسین فراهانی فرزان براتی محمد نجاتی حمید باتمانیIn this paper, vibration analysis of thick functionally graded beam with simply supported boundary condition under constant axial load is studied. The beam has a uniform cross-sectional area and the mechanical properties of the fungtionally graded beam are assumed to be أکثرIn this paper, vibration analysis of thick functionally graded beam with simply supported boundary condition under constant axial load is studied. The beam has a uniform cross-sectional area and the mechanical properties of the fungtionally graded beam are assumed to be vary through the thickness of the beam. Fundamental relations, the equilibrium and stability equations based on the displacement components are derived using the two-dimensional elasticity theory and hamilton's principle. Generalized differential quadrature (GDQ) method is used to solve the system of coupled differential equations at equilibrium and moving condition. In this paper, the influences of axial loads, dimensionless geometric parameter, functionally graded index and ratio of thickness to length on the vibration of beam is presented. To study the accuracy of the present analysis, a compression is carried out between the present results and published results and also results obtained from ABAQUSE program. Results showed that the generalized differential quadrature method is quite good. Based on the results obtained by increasing the volume fraction of fibers in the functional graded beam, the natural frequency of the beam increases and for high volume fraction, it is not possible to see much change in the natural frequency. Also, by increasing the ratio of thickness to length in the absence of the critical load the natural frequency decreased. تفاصيل المقالة -
حرية الوصول المقاله
302 - Nonlinear Vibration Analysis of an Euler-Bernoulli Beam Resting on a Nonlinear Elastic Foundation under Compressive Axial Force
احمد مامندی محمدحسین کارگرنوینThis paper studies the nonlinear vibration analysis of a simply supported Euler-Bernoulli beam resting on a nonlinear elastic foundation under compressive axial load using nonlinear normal modes concept in the case of three-to-one (3:1) internal resonance. The beam&rsqu أکثرThis paper studies the nonlinear vibration analysis of a simply supported Euler-Bernoulli beam resting on a nonlinear elastic foundation under compressive axial load using nonlinear normal modes concept in the case of three-to-one (3:1) internal resonance. The beam’s governing nonlinear PDE of motion and also its boundary conditions are derived and then solved using the method of Multiple Time Scales. Under three to-one-internal resonance condition applying nonlinear normal modes the steady state stability analysis of the beam’s vibrations is performed. Then the effect of changing the value of different parameters on the beam’s dynamic response and the steady state stability analysis is investigated. تفاصيل المقالة -
حرية الوصول المقاله
303 - Nonlinear Vibration Analysis of a Cylindrical FGM Shell on a Viscoelastic Foundation under the Action of Lateral and Compressive Axial Loads
احمد مامندیIn this paper, the nonlinear vibration analysis of a thin cylindrical shell made of Functionally Graded Material (FGM) resting on a nonlinear viscoelastic foundation under compressive axial and lateral loads is studied. Nonlinear governing coupled partial differential e أکثرIn this paper, the nonlinear vibration analysis of a thin cylindrical shell made of Functionally Graded Material (FGM) resting on a nonlinear viscoelastic foundation under compressive axial and lateral loads is studied. Nonlinear governing coupled partial differential equations of motions (PDEs) for cylindrical shell are derived using improved Donnell shell theory. The equations of motions (EOMs) then are solved using the Galerkin method, Volmir’s assumption and the forth-order Runge-Kutta method to obtain dynamic response of the shell including nonlinear frequencies, frequency-amplitude curves and nonlinear radial deflection for the shell of revolution. Afterward, the effect of changing the value of different parameters on the nonlinear dynamic response of the FGM cylindrical shell considering compressive axial and lateral loads, geometric characteristics of the shell, FGM material distribution along direction of the thickness of the shell and coefficients of the viscoelastic foundation are all investigated تفاصيل المقالة -
حرية الوصول المقاله
304 - ارزیابی پارامتری گود پایدار شده به روش میخ‌کوبی در خاک‌های چسبنده و غیرچسبنده
مجمد نجفی صالحی نجفی صالحی سینا فرد مرادی نیا روزبه دبیریامروزه ترافیک سنگین و مشکلات حمل و نقل شهری از مهمترین مشکلات شهرهای بزرگ است. به نظر می‌رسد که یکی از بهترین روش‌ها در جهت کاهش این مشکلات استفاده از حمل و نقل زیرزمینی و تونل‌های شهری است. مطالعات ژئوتکنیک از عوامل مهم در تعیین نوع، شکل و هزینه ساخت سازه‌های زیرزمینی أکثرامروزه ترافیک سنگین و مشکلات حمل و نقل شهری از مهمترین مشکلات شهرهای بزرگ است. به نظر می‌رسد که یکی از بهترین روش‌ها در جهت کاهش این مشکلات استفاده از حمل و نقل زیرزمینی و تونل‌های شهری است. مطالعات ژئوتکنیک از عوامل مهم در تعیین نوع، شکل و هزینه ساخت سازه‌های زیرزمینی به حساب می‌آید. به عبارت دیگر نوع، طراحی و ساخت آنها به شرایط زمین‌شناسی و ژئوتکنیکی وابسته است. باید توجه داشت که در بسیاری موارد اختیار زمین مناسب برای حفاری‌های زیرزمینی جهت احداث سازه‌های زیرزمینی وجود ندارد که بر این اساس ایستگاه‌های شهری اجبارا باید در محدوده معینی احداث شوند و این امکان وجود ندارد که برای دستیابی به زمین مناسبتر، مسیر آنها تغییر داده شود. در این تحقیق با کمک نرم‌افزار PLAXIS به بررسی متغیر گود دیواره در ورودی شمالی ایستگاه شماره 6 متروی تهران پرداخته شده است. اثر متغیرهای خاک (متغیرهای مدول موهر-کولمب)، متغیرهای ساختمان (عرض ساختمان، فاصله ساختمان) و متغیرهای گود (عرض و عمق گود) مورد بررسی قرار گرفته اند. نتایج حاصله نشان داد که جابجایی در راستای طولی دیواره گود در حالت تحلیل تحکیم نسبت به مقدار جابجایی در راستای طولی دیواره گود در حالت تحلیل پلاستیک افزایش یافته است. همچنین حداکثر نیروی داخلی در میخ‌های ناحیه یک سوم پایینی بوجود می‌آید. تفاصيل المقالة -
حرية الوصول المقاله
305 - Micro1
حسین دهبانیThe origin of the modern theories of a continuum with microstructure goes back to papers by Ericksen and Truesdell (1958), Mindlin (1964), Eringen and Suhubi (1964) and Green and Rivlin (1964). Green (1965) has established the connection of the theory of multipolar co أکثرThe origin of the modern theories of a continuum with microstructure goes back to papers by Ericksen and Truesdell (1958), Mindlin (1964), Eringen and Suhubi (1964) and Green and Rivlin (1964). Green (1965) has established the connection of the theory of multipolar continuum mechanics and the other theories. Much of the theoretical progress in the field is discussed in the books of Kunin (1983), Ciarletta and Iesan (1993) and Eringen (1999). In the theory of micromorphic bodies formulated by Eringen and Suhubi (1964, 1999) the material particle is endowed with three deformable directors and the theory introduces nine extra degrees of freedom over the classical theory. On the basis of the theory of bodies with inner structure, Grot (1969) has established a theory of thermodynamics of elastic bodies with microstructure whose microelements possess microtemperatures. The Clausius–Duhem inequality is modified to include microtemperatures, and the firstorder moment of the energy equations are added to the usual balance laws of a continuum with microstructure. The theory of micromorphic fluids with microtemperatures has been studied in various papers (see, e.g., Koh, 1973; Riha, 1975, 1977; Verma et al., 1979). Riha (1976) has presented a study of heat conduction in materials with microtemperatures. Experimental data for the silicone rubber containing spherical aluminium particles and for human blood were found to conform closely to predicted theoretical thermal conductivity. تفاصيل المقالة -
حرية الوصول المقاله
306 - تحلیل میکروپالر پیزوترمواالستیسیته
حسین دهبانیThe origin of the modern theories of a continuum with microstructure goes back to papers by Ericksen and Truesdell (1958), Mindlin (1964), Eringen and Suhubi (1964) and Green and Rivlin (1964). Green (1965) has established the connection of the theory of multipolar co أکثرThe origin of the modern theories of a continuum with microstructure goes back to papers by Ericksen and Truesdell (1958), Mindlin (1964), Eringen and Suhubi (1964) and Green and Rivlin (1964). Green (1965) has established the connection of the theory of multipolar continuum mechanics and the other theories. Much of the theoretical progress in the field is discussed in the books of Kunin (1983), Ciarletta and Iesan (1993) and Eringen (1999). In the theory of micromorphic bodies formulated by Eringen and Suhubi (1964, 1999) the material particle is endowed with three deformable directors and the theory introduces nine extra degrees of freedom over the classical theory. On the basis of the theory of bodies with inner structure, Grot (1969) has established a theory of thermodynamics of elastic bodies with microstructure whose microelements possess microtemperatures. The Clausius–Duhem inequality is modified to include microtemperatures, and the firstorder moment of the energy equations are added to the usual balance laws of a continuum with microstructure. The theory of micromorphic fluids with microtemperatures has been studied in various papers (see, e.g., Koh, 1973; Riha, 1975, 1977; Verma et al., 1979). Riha (1976) has presented a study of heat conduction in materials with microtemperatures. Experimental data for the silicone rubber containing spherical aluminium particles and for human blood were found to conform closely to predicted theoretical thermal conductivity. تفاصيل المقالة -
حرية الوصول المقاله
307 - Neural network in predicting the mechanical strength of Al6061/SiC composites used in aerospace industries
سید رحیم کیاحسینیIn this research, the effect of three parameters, the percentage and type of SiC reinforcing material and the type of thermal cycle of composite manufacturing on the elastic modulus, yield strength and ultimate strength of Al/SiC composite have been investigated. For th أکثرIn this research, the effect of three parameters, the percentage and type of SiC reinforcing material and the type of thermal cycle of composite manufacturing on the elastic modulus, yield strength and ultimate strength of Al/SiC composite have been investigated. For this purpose, the information related to composite with Al6061alloy reinforced with SiC particles was extracted. After normalizing the input and output information, the perceptron recurrent network was designed and it was tried to extract the optimal parameters by changing different parameters of the network such as the frequency of network training, changing the learning coefficient of the network and weight and bias coefficients and comparing the sum of squared errors in different conditions. Finally, by defining the adaptive learning coefficient in the network, it was tried to improve the speed and accuracy of the network. The results showed that by repeating the network training 10000000 times, the sum of squares of error was reduced to the range of 7-10. Also, the lowest error sum of squares is related to the learning coefficient α=0.002. The results related to the definition of the adaptive learning coefficient showed that if the network is trained 100,000 times, the training speed decreases to 60,000 times with the same error for the adaptive learning coefficient and the constant learning coefficient. In other words, if the adaptive learning coefficient is used, the training speed and error reduction will be higher than using the constant learning coefficient. تفاصيل المقالة -
حرية الوصول المقاله
308 - thermoelasticity FGM
حسین دهبانیThe origin of the modern theories of a continuum with microstructure goes back to papers by Ericksen and Truesdell (1958), Mindlin (1964), Eringen and Suhubi (1964) and Green and Rivlin (1964). Green (1965) has established the connection of the theory of multipolar co أکثرThe origin of the modern theories of a continuum with microstructure goes back to papers by Ericksen and Truesdell (1958), Mindlin (1964), Eringen and Suhubi (1964) and Green and Rivlin (1964). Green (1965) has established the connection of the theory of multipolar continuum mechanics and the other theories. Much of the theoretical progress in the field is discussed in the books of Kunin (1983), Ciarletta and Iesan (1993) and Eringen (1999). In the theory of micromorphic bodies formulated by Eringen and Suhubi (1964, 1999) the material particle is endowed with three deformable directors and the theory introduces nine extra degrees of freedom over the classical theory. On the basis of the theory of bodies with inner structure, Grot (1969) has established a theory of thermodynamics of elastic bodies with microstructure whose microelements possess microtemperatures. The Clausius–Duhem inequality is modified to include microtemperatures, and the firstorder moment of the energy equations are added to the usual balance laws of a continuum with microstructure. The theory of micromorphic fluids with microtemperatures has been studied in various papers (see, e.g., Koh, 1973; Riha, 1975, 1977; Verma et al., 1979). Riha (1976) has presented a study of heat conduction in materials with microtemperatures. Experimental data for the silicone rubber containing spherical aluminium particl تفاصيل المقالة -
حرية الوصول المقاله
309 - Synthesis of polymer matrix nanocomposite with carbon fibers and analysis of its strength properties
S.M.M. ShafieiIn polymer-based nanocomposites, carbon nanofibers have been used to improve mechanical properties in various applications. In this research, the tensile properties of carbon nanofibers have been used to create carbon-epoxy nanocomposite and improve the mechanical prope أکثرIn polymer-based nanocomposites, carbon nanofibers have been used to improve mechanical properties in various applications. In this research, the tensile properties of carbon nanofibers have been used to create carbon-epoxy nanocomposite and improve the mechanical properties of epoxy nanocomposite, and the effect of the weight percentage of carbon nanofibers on the mechanical properties of epoxy nanocomposite has been investigated. Epoxy with weight percentages of 1.0, 5.0 and 1.5 carbon nanofibers were produced and their mechanical properties were investigated. The results showed that the use of even a small percentage of carbon nanofibers can lead to the improvement of mechanical properties. تفاصيل المقالة -
حرية الوصول المقاله
310 - ساختار تولید صنعت پرورش ماهی قزل آلا در استان چهارمحال و بختیاری
رویا اشراقی سامانی سعید یزدانی سید مهریار صدرالاشرافی غلامرضا پیکانیدر این مطالعه ساختار تولید صنعت پرورش ماهی قزل آلا در استان چهارمحال و بختیاری مورد بررسی قرار گرفته است. برای این منظور با بهره گیری از تئوری دوگان و با استفاده از آمار ترکیبی سری زمانی- مقطع عرضی، تابع هزینه ترانسلوگ و توابع تقاضای مشتق شده از آن در قالب یک سیستم معاد أکثردر این مطالعه ساختار تولید صنعت پرورش ماهی قزل آلا در استان چهارمحال و بختیاری مورد بررسی قرار گرفته است. برای این منظور با بهره گیری از تئوری دوگان و با استفاده از آمار ترکیبی سری زمانی- مقطع عرضی، تابع هزینه ترانسلوگ و توابع تقاضای مشتق شده از آن در قالب یک سیستم معادلات به ظاهر نامرتبط تکراری به طور هم زمان برآورد شد. بر اساس نتایج به دست آمده، تکنولوژی تولید صنعت پرورش قزل آلا در منطقه مورد مطالعه غیر هموتتیک بوده و در اثر تغییر مقیاس تولید، سهم هزینه عوامل تولید تغییر می یابد. تکنولوژی تولید این محصول کار اندوز و سرمایه اندوز بوده و سهم هزینه نهاده های غذا و بچه ماهی در اثر افزایش مقیاس تولید افزایش می یابد. هم چنین بازده نسبت به مقیاس تولید در این صنعت فزاینده می باشد. کشش های جانشینی آلن محاسبه شده حاکی از آن است که به استثنای رابطه مکملی نهاده بچه ماهی با نهاده های نیروی کار و غذا، رابطه میان سایر نهاده ها جانشینی می باشد. مقادیر عددی مربوط به کشش های خود قیمتی نیز نشان دهنده کشش ناپذیری تقاضای نهاده های نیروی کار، سرمایه و غذا در برابر تغییر قیمت آن ها در صنعت پرورش ماهی قزل آلای پرورشی است. هم چنین براساس کشش های قیمتی متقاطع محاسبه شده، کشش متقاطع غذا در برابر تغییر قیمت سایر نهاده ها کمتر از کشش متقاطع سایر نهاده ها نسبت به تغییر قیمت نهاده غذا است. تفاصيل المقالة
سند
Sanad is a platform for managing Azad University publications
الروابط
المراكز ذات الصلة
دعامة
الصفحات الرسمية
حقوق هذا الموقع الإلكتروني مملوكة لنظام SANAD Press Management. © 1442-1446