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دسترسی آزاد مقاله
1 - Analysis of FGM Cylindrical Shell under Impact Loading of Explosion
reza azarafza puya pirali Ali JavadiDue to the increasing application of Functionally Graded Materials (FGM) shells, it seems necessary to investigate their behaviour under different loads. Therefore, in this paper, the dynamic response of functionally graded materials cylindrical shells under explosive l چکیده کاملDue to the increasing application of Functionally Graded Materials (FGM) shells, it seems necessary to investigate their behaviour under different loads. Therefore, in this paper, the dynamic response of functionally graded materials cylindrical shells under explosive load has been investigated with analytical and simulation methods. LS-DYNA software is used in the simulation method. In analytical solution, vibration of composite circular cylindrical shells is investigated based on the first-order deformation shell theory. The boundary conditions are assumed to be fully simply supported. The dynamic response of composite shells is studied under blast loading. The modal technique is used to develop the analytical solution of composite shell. The solution for the shell under the giving loading condition can be found using the convolution integral. Material properties are assumed to be graded in the thickness direction according to Reddy function. A FGM cylindrical shell is made up of a mixture of ceramic and metal. Results show that the effect of explosion is such that it has the greatest effect on the inner layer and with increasing thickness to the outside of the shell this effect decreases and when the maximum deflection occurs, the dynamic velocity is zero. Also, it was observed that with increasing length, the radial deflection increases due to increasing the distance from the support to the center of the shell. پرونده مقاله -
دسترسی آزاد مقاله
2 - 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 چکیده کاملVibration 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. پرونده مقاله -
دسترسی آزاد مقاله
3 - 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 چکیده کاملThe 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. پرونده مقاله -
دسترسی آزاد مقاله
4 - بررسی ضربه پذیری لوله های استوانه‌ای شیاردار تحت بارگذاری دینامیکی به عنوان جاذب انرژی
مجتبی کرمعلی محمد جواد رضوانیدر این مقاله، ضربه پذیری لوله‌های استوانه‌ای جدارنازک شیاردار با استفاده از شبیه سازی عددی در نرم افزار ال. اس. داینا 1 تحت بارگذاری دینامیکی بررسی می شود. برای این منظور، شیارهای داخلی و خارجی با فاصله یکسان بر روی لوله استوانه‌ای ایجاد شده تا تغییر شکل پلاستیک از محل چکیده کاملدر این مقاله، ضربه پذیری لوله‌های استوانه‌ای جدارنازک شیاردار با استفاده از شبیه سازی عددی در نرم افزار ال. اس. داینا 1 تحت بارگذاری دینامیکی بررسی می شود. برای این منظور، شیارهای داخلی و خارجی با فاصله یکسان بر روی لوله استوانه‌ای ایجاد شده تا تغییر شکل پلاستیک از محل شیار شکل گرفته و چین‌هایی به صورت متقارن بوجود آید. هدف از این مطالعه، بررسی تاثیر شیار بر جذب انرژی، نیروی بیشینه لهیدگی و راندمان نیروی لهیدگی می‌باشد. نتایج حاصل از شبیه‌سازی عددی نشان می‌دهد که با افزایش تعداد شیار تغییر محسوسی در نحوه چین خوردگی نمونه ها مشاهده نمی‌شود. همچنین، با افزایش تعداد شیار جذب انرژی و نیروی ماکزیمم لهیدگی کاهش یافته و نوسانات منحنی نیرو-جابجایی به صورت یکنواخت تر ایجاد می‌شود. نتایج حاصل از این تحقیق می‌تواند در صنایع مختلف از جمله خودروسازی، صنایع ریلی، هوافضا و آسانسور جهت جذب انرژی ضربه مورد استفاده قرار گیرد. پرونده مقاله -
دسترسی آزاد مقاله
5 - Comparison of Geotextile Layers Effects on Static and Dynamic behavior of Pavement
Reza Nazari Rouzbeh DabiriOne of the methods for the improvement of soil against the tensile stresses is using the artificial supplements in soil such as metal belts or nets, polymer materials and natural fibers. Technically this method is called the reinforced of soil. When a pavement is locate چکیده کاملOne of the methods for the improvement of soil against the tensile stresses is using the artificial supplements in soil such as metal belts or nets, polymer materials and natural fibers. Technically this method is called the reinforced of soil. When a pavement is located on soft soil, great deformations can occur as a result of the crossing of traffic load in superstructure layers of the body. This can finally lead to the increase in the cost of maintenance and traffic pause in transportation. The main purpose of this study is to explore the effect of geotextile layers place in various depths of the body of pavement layers located on soft soil. For this purpose, models with the identical geometry from the transection of road using Finite Element Method software, PLAXIS were analyzed in two dimensions in which the location and the number of geotextile layers were considered in various depths. In continue, these models have been under static and dynamic loadings due to vehicles and the settlement rate and the lateral deformation of pavement in section has been evaluated. The results show that in static loading, the maximum safety factor of stability is that of layers in which the geotextile exists in the partition between subgrade and embankment layers. Also, between dynamic loading and increasing number of geotextile layers favorable result is not achieved. Although more studies need to be carried out in this area. پرونده مقاله -
دسترسی آزاد مقاله
6 - بررسی رفتار تیرهای مختلط با دهانه‌های بزرگ با نرم‌افزار آباکوس
نگین عیسی زاده امین قنادی اصلاستفاده از بتن به همراه فولاد در سازه‌ها می‌تواند نقش مؤثری در بهبود رفتار سازه یعنی افزایش مقاومت و شکل‌پذیری، ایفا نماید. در بسیاری از موارد در سازه‌های فولادی که ضوابط شکل پذیری قابل ملاحظه را ارضا نمی‌کنند . تیرهای مختلط فولادی بتنی شامل یک تیر فولادی هستند که بر رو چکیده کاملاستفاده از بتن به همراه فولاد در سازه‌ها می‌تواند نقش مؤثری در بهبود رفتار سازه یعنی افزایش مقاومت و شکل‌پذیری، ایفا نماید. در بسیاری از موارد در سازه‌های فولادی که ضوابط شکل پذیری قابل ملاحظه را ارضا نمی‌کنند . تیرهای مختلط فولادی بتنی شامل یک تیر فولادی هستند که بر روی آن بلوک بتنی با استفاده از اتصالات برشی نصب می‌شود. در ساخت و ساز سنتی تیرهای مرکب، بلوک‌های بتنی بدون اتصالات خاص روی تیر فولادی قرار می‌گیرد و توسط آن حمایت می‌شود. از آنجا که در این حالت هیچ اتصالی بین بلوک بتنی و تیر فولادی قرار ندارد، تحت اثر بارهای مختلف، هرکدام به شکل مستقل واکنش عمل می‌کنند. در این تحقیق تیر مختلط با رویی بتنی و تیر فولادی ثابتی را مدل سازی با نرم افزار المان محدود ABAQUS مدل و صحت‌سنجی با مدل آزمایشگاهی انجام یافته است و در ادامه شش دسته ( میلگرد – اصطکاکی – نبشی – میلگرد L شکل- ناودانی – دو ردیف میلگرد – دو ردیف نبشی ) که تفاوت نمونه‍ها فقط در نحوه اتصال بتن به فولاد بوده مدل‌سازی و برای هر شش سری پنج ضخامت متفاوت در نظر گرفته شده و تحقیق گردیده است که در نتیجه مطالب زیر نتیجه‌گیری شده است . افزایش تعداد برشگیرها باعث افزایش مقاومت در تیرهای مرکب می‌شود . با افزایش تعداد برشگیرهای ساده به دو ردیف میزان ده درصد مقاومت نهایی خمشی تیرهای مرکب را افزایش می‌دهد. تاثیر بین برشگیرهای ناودانی و نبشی تفاوت چندانی نشان نمی‌دهد. تاثیر بین برشگیرهای ساده و L شکل در حدود 2 درصد فرق کرده است پرونده مقاله -
دسترسی آزاد مقاله
7 - Numerical modeling of FRP reinforcements in concrete frames under dynamic loading
Hadi Gourijan Seyed Ali RazaghiSpecial concrete frames are designed to withstand the bending loads caused by earthquakes, and how to reinforce them is debatable. In this study, the effect of a type of these frames that are reinforced with FRP composite reinforcements was discussed. The research was c چکیده کاملSpecial concrete frames are designed to withstand the bending loads caused by earthquakes, and how to reinforce them is debatable. In this study, the effect of a type of these frames that are reinforced with FRP composite reinforcements was discussed. The research was conducted by finite element method and after validation with a real sample and checking the convergence of the results, permission to use this method was issued. The result was that the loads caused by earthquakes, which affect the structures in the form of bending and shear, despite the need for proper resistance to repel the effect, need a little flexibility in movement so that such loads do not cause material fatigue. FRP reinforcements, due to their good flexibility, provide limited movement of the frame, so fewer loads is applied to it and proper connection between the members also eliminates danger. Thus, structures with a suitable safety factor and bending and shear loads will not be able to pose a hazard. A comparison was made between the effects of metal reinforcement and composite reinforcement, which proved to be positive. Special concrete type also showed good resistance to severe seismicity and was considered suitable for construction in seismic areas. پرونده مقاله -
دسترسی آزاد مقاله
8 - The analysis of failure for a stud bolt with reduced shank under dynamic loading
Mahdi Ghayuri Mohammad Rahim TorshizianIn this research, the failure of a stud bolt was studied. This bolt is under periodic loading, in a multi-stage compressor. The undesired vibration of the system causes vibration load on the bolt. The bolt was modeled in Abaqus software and the generated stress was calc چکیده کاملIn this research, the failure of a stud bolt was studied. This bolt is under periodic loading, in a multi-stage compressor. The undesired vibration of the system causes vibration load on the bolt. The bolt was modeled in Abaqus software and the generated stress was calculated. To determine the dynamic load on the bolt, the vibration of the system was measured by a digital vibration sensor and this load was simulated in Abaqus software. The boundary condition and loading were considered similar to the real working condition. The failure and fatigue of the bolt was investigated in the periodic loading. The factors such as the shank diameter, chamfer radius and material were changed and the corresponding response of sample and change in stress was studied. The most probable points of the bolt for failure were found and the effected of the reduced shank diameter on its life was considered. In the initial design, the shank diameter was considered 12 mm. The results shown that by decreasing the shank diameter, the stress first decreases and then increases and the minimum of stress occur at the shank with a diameter of 11.47 mm. Also, by increasing the chamfer radius, the stress first increases and then decreases and the minimum of stress occurs at the chamfer radius of 33 mm. پرونده مقاله
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