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1 - Determination of Local Constitutive Properties of Aluminum using Digital Image Correlation: A Comparative Study Between Uniform Stress and Virtual Fields
Ali Shahmirzaloo Mohammadreza FarahaniA proper understanding of material mechanical properties is important in designing and modelling of components. As a part of a study on the structural integrity, the Digital Image Correlation technique was used to obtain the full-field strain distribution during a tensi أکثرA proper understanding of material mechanical properties is important in designing and modelling of components. As a part of a study on the structural integrity, the Digital Image Correlation technique was used to obtain the full-field strain distribution during a tensile test of the specimens. The displacement maps were analyzed using Matlab scripts to compute local stress-strain variations. Consequently the local proof stress values were extracted. In this study, the local extraction of the elastic and plastic properties of Al6061 alloy has been carried out using both the uniform stress method and the virtual fields method involving digital image correlation technique. In uniform stress methodology, full range stress–strain curves are obtained using the whole field strain measurement using Digital Image Correlation. The parameters investigated are Young's modulus, Poisson's ratio, yield strength, strain hardening exponent and strength coefficient. Recently, the virtual fields method is gaining a lot of popularity in domain characterization as it is robust, accurate and faster. Young's modulus, Poisson's ratio, yield strength, strength coefficient and strain hardening exponent are the parameters extracted using both uniform stress method and virtual fields method. The parameter variation obtained by both uniform stress method and the virtual fields method compares very well. Due to various advantages associated with virtual fields method, it is generally recommended for material mechanical properties extraction. تفاصيل المقالة -
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2 - 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 -
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3 - Modelling Mechanical Properties of AISI 439-430Ti Ferritic Stainless Steel Sheet
N Brinis B Regaiguia O Chahaoui N Maatougui M.L FaresThe comprehension of the anisotropy impactson mechanical properties of the rolled steel sheets was investigated using a non-quadratic anisotropic yield function. In this study, experimental and modelling determination regardingthe behaviourof an industrial rolledsheet f أکثرThe comprehension of the anisotropy impactson mechanical properties of the rolled steel sheets was investigated using a non-quadratic anisotropic yield function. In this study, experimental and modelling determination regardingthe behaviourof an industrial rolledsheet for a ferritic stainless low-carbon steel were carried out. The parameters of the associated yield equation, derived from the three orthotropic yield functions proposed by Hill48, Yld96 and Yld2000-2d, were determined. Predictions and the evolution of normalized yield stress and normalized Lankford parameters (plastic strain ratio) obtained by the presented investigative are considered. The forecasts given by the YLD2000-2d criterion are consistent with that of the experience. In order to describe the path of strain behavior, the isotropic hardening function is described using the following four empirical standard formulae based on: Hollomon, Ludwick, Swift and Voce law.More accurately,the anisotropy coefficients of three yield functions are represented as a function of the longitudinal equivalent plastic strain. تفاصيل المقالة -
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4 - Strain Hardening Analysis for M-P Interaction in Metallic Beam of T-Section
M Hosseini H HatamiThis paper derives kinematic admissible bending moment – axial force (M-P) interaction relations for mild steel by considering strain hardening idealisations. Two models for strain hardening – Linear and parabolic have been considered, the parabolic model be أکثرThis paper derives kinematic admissible bending moment – axial force (M-P) interaction relations for mild steel by considering strain hardening idealisations. Two models for strain hardening – Linear and parabolic have been considered, the parabolic model being closer to the experiments. The interaction relations can predict strains, which is not possible in a rigid, perfectly plastic idealization. The relations are obtained for all possible cases pertaining to the locations of neutral axis. One commercial rolled steel T-section has been considered for studying the characteristics of interaction curves for different models. On the basis of these interaction curves, most significant cases for the position of neutral axis which are enough for the establishment of interaction relations have been suggested. The influence of strain hardening in the interaction study has been highlighted. The strains and hence the strain rates due to bending and an axial force can be separated only for the linear-elastic case because the principle of superposition is not valid for the nonlinear case. The difference between the interaction curves for linear and parabolic hardening for the particular material is small. تفاصيل المقالة -
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5 - On the Optimum Die Shape in Rod Drawing Process Considering Work-Hardening Effect of Material
M.M Mahdavi H HaghighatThe assessment of the influence of the work-hardening of material on the optimum die profile and drawing force in rod drawing process is the main objective of the present paper. The upper bound solution, based on the assumption of perfect plasticity, has been extended t أکثرThe assessment of the influence of the work-hardening of material on the optimum die profile and drawing force in rod drawing process is the main objective of the present paper. The upper bound solution, based on the assumption of perfect plasticity, has been extended to consider the work-hardening of the material during the rod drawing process through curved dies. Analytical results of drawing forces for rod drawing process through four different types of streamlined die profiles are compared with the finite element simulation data using the finite element code, DEFORM 2D. It is shown that as the work-hardening exponent increases, the optimum die length increases, the required drawing force decreases and maximum possible reduction in area increases. Based on this proposed modeling technique, drawing process of real materials through various curved dies can be optimized. تفاصيل المقالة -
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6 - Numerical and Experimental Study on Ratcheting Behavior of Plates with Circular Cutouts under Cyclic Axial Loading
K Kolasangiani M Shariati Kh Farhangdoost A Varvani-FarahaniIn this paper, accumulation of plastic deformation of AISI 1045 steel plates with circular cutouts under cyclic axial loading is studied. Loading was applied under force-control conditions. Experimental tests were performed using a Zwick/Roell servo hydraulic machine. U أکثرIn this paper, accumulation of plastic deformation of AISI 1045 steel plates with circular cutouts under cyclic axial loading is studied. Loading was applied under force-control conditions. Experimental tests were performed using a Zwick/Roell servo hydraulic machine. Under force-control loading with nonzero mean force, plastic strain was accumulated in continuous cycles called ratcheting. Numerical analysis was carried out by ABAQUS software using nonlinear isotropic/kinematic hardening model. The results of the numerical simulations were compared to experimental data. The results demonstrated that the ratcheting response of plates with circular cutouts could be numerically simulated with a reasonable accuracy. It was observed that the local and global plastic deformation increase with increasing the notch diameter. Also, maximum principal stress was the main parameter for initiation of crack around the notch. Based on numerical results, at notch root, both ratcheting strain and local mean stress relaxation was occur simultaneously and due to relaxation of local mean stress, plastic shakedown was occurred. تفاصيل المقالة -
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7 - Response of Qualitative Characteristics of Spring Bread Wheat (Triticum aestivum L.) to Terminal Heat and Determine Correlation Between Traits
Mani MojadamBACKGROUND: Terminal heat stress affected on qualitative characters. Identification of relation between heat tolerance and baking quality is more important. Many quality characteristics are important for the utilization of wheat, particularly flour protein concentration أکثرBACKGROUND: Terminal heat stress affected on qualitative characters. Identification of relation between heat tolerance and baking quality is more important. Many quality characteristics are important for the utilization of wheat, particularly flour protein concentration and bread-making properties. OBJECTIVES: This study was performed to evaluate the tolerance of bread wheat genotypes qualitative traits to extreme heat stress (above 40 C◦). Genotypes were evaluated in two separate experiments in 2 years. METHODS: The experiment was laid out in split- split- plot design with 3 replications at field of Safi Abad Dezful (Khuzestan province of Iran) Agricultural Research Station in 2014-2016. To study qualitative traits and seed protein, 4 genotypes (Chamran, Baj, Chamran2 and ER-92-19), 3 cultivation methods (stripe, 2 line on bed and 3 line on bed) and 3 seed rate (400, 600 and 800 seed.m-2) are selected. RESULT: Seven qualitative traits involve bread value (BV), hardening index (HI), Moisture%, Protein%, WA% (water absorbance), Zeleny and Wet gluten was measured. Correlation coefficient results seed protein% had negative with HI, BV and Zeleny. BV had positive correlation with HI and positive with flour moisture and wet gluten. Results showed that cultivation method influence on BV and seed protein. Only BV influenced by seed rate. In 600 seed.m-2 BV was the least (513.21) and in 800 seed.m-2 was the most (519.28). Genotypes in BV, HI, protein and Zeleny had significant differences. These results are so useful for preparing gluten free breads. But more research require. CONCLUSION: In hot climate such as north of Khuzestan province of Iran that spring has above temperature and multiple cropping system is usual, cultivation of tolerant and early mature genotypes had economical. In Addition with good management, seed quality is better than forecasting. So researchers can promote this project and farmers can use these results surely. تفاصيل المقالة -
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8 - بررسی تجربی ریز ساختار آلیاژ آلومینیوم درفرآیندECAP و مقایسه دو مقطع گرد و مربعی
مهدی رفیعیپرس کردن مواد در قالب های زاویه ای ECAP یکی از روش های شکل دهی است که به منظور ایجاد کرنش های بالا جهت کارسختی و بهبود ریز ساختار انجام می گردد و با استفاده از شکل دهی تحت فشار و تحت زاویه در قالب و در اثر پدیده کارسختی ایجاد شده ، بهبود ریزساختار ، خواص مکانیکی خوب و ق أکثرپرس کردن مواد در قالب های زاویه ای ECAP یکی از روش های شکل دهی است که به منظور ایجاد کرنش های بالا جهت کارسختی و بهبود ریز ساختار انجام می گردد و با استفاده از شکل دهی تحت فشار و تحت زاویه در قالب و در اثر پدیده کارسختی ایجاد شده ، بهبود ریزساختار ، خواص مکانیکی خوب و قابلیت انعطاف پذیری بالا حاصل می گردد. در این مقاله کیفیت تغییر ریز ساختار و بهبود شرایط و مقاومت مکانیکی با استفاده از روش پرس کردن برای آلیاژ آلومینیوم ( 6xxx ) در قالب زاویه ای بررسی شده است به نحوی که قالب تهیه شده دارای دو مقطع مربعی و دایره ای بوده و نمونه ها فقط یک بار پرس شدند و همچنین تفاوت های حاصل از این دو مقطع ، در تغییرات ریز ساختار بررسی شده است. نتایج حاصل از بررسی ها نشان داد که با پرس کردن نمونه ها بهبود و یکنواخت شدن ساختار حاصل گردید و در این میان نمونه های با مقطع دایره ای شرایط بهتری از آثار کار سختی و بهبود ساختار را نشان داد. تفاصيل المقالة -
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9 - Investigation of The Mechanism of Change of Concrete Modulus Matrix in Monotonic Loading and its Numerical Analysis
Farzad PeymanThe primary purpose of studying the behavior of concrete is to calculate its strength and deformation under environmental conditions and loading. In this regard, due to the structure and nature of concrete, non-isotropic in its experimental behavior at different loads i أکثرThe primary purpose of studying the behavior of concrete is to calculate its strength and deformation under environmental conditions and loading. In this regard, due to the structure and nature of concrete, non-isotropic in its experimental behavior at different loads is observed, considered in this research. Accordingly, by assuming a different linear elastic behavior in each loading increment and the experimental results, an attempt has been made to define a numerical linear-nonlinear behavior for concrete. Therefore, proportional numerical functions are defined based on the damage in the modulus of elasticity and the changes in the Poisson ratio of the concrete tested in monotonic loading types, the coefficients obtained from the related experimental results. The computational effects of these functions during the analytical method of the research cause the experimental behavior of concrete to be converted to numerical behavior. The validity of this numerical method is based on calibration and comparison with experimental results. In addition to hardening behavior, this numerical analysis can define softening behavior. تفاصيل المقالة -
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10 - Microstructure evolution and mechanical properties of Mo40/C93200 bimetal processed by compound casting process
Mohammad Honarpisheh Mobin Javaheri Hadi mansouriCompound casting refers to a process that used to produce bimetals. This study investigates the interface of Mo40/C93200 that is produced by compound casting process. In this research, molten bronze is poured around steel core, interaction between liquid and solid creat أکثرCompound casting refers to a process that used to produce bimetals. This study investigates the interface of Mo40/C93200 that is produced by compound casting process. In this research, molten bronze is poured around steel core, interaction between liquid and solid creates a diffusion zone and followed by a transition layer which leads to the creation of diffused region between the interfaces of metal layers. The results of micro-hardness and macro hardness used to complete the studies. The results of the hardness of the Mo40 alloy revealed that the micro-hardness of the alloy was almost 308 Vickers which this amount of hardness confirms the ferrite-pearlite state of microstructures. The results of metallography revealed that the boundary between steel and bronze alloys due to the difference in electric potential during etching evolved a galvanic cell and one section formed as the cathode and the other section as the anode. In this situation steel was corroding and bronze was protecting. As well as, the results of SEM show that the boundaries between two alloys have an acceptable adhesion and the strength of interface is sufficient. The result of tensile test indicates that the final yield strength was about 800 MPa and the elongation increases by 2%, which is an acceptable value. It is also observed that the failure is a soft defect type and a sufficient connection between steel and bronze is formed. تفاصيل المقالة -
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11 - Age-Hardening Behavior and the Related Changes in a Silver-Copper-Palladium Alloy
Morteza Hadi Iman Ebrahimzadeh Omid BayatAge-hardening behavior and related changes were studied to elucidate the hardening mechanism of an Ag–Cu–Pd alloyby Differential Scanning Calorimetry (DSC), hardness test, X-ray diffraction (XRD), scanning electron microscopic (SEM) observations and energy d أکثرAge-hardening behavior and related changes were studied to elucidate the hardening mechanism of an Ag–Cu–Pd alloyby Differential Scanning Calorimetry (DSC), hardness test, X-ray diffraction (XRD), scanning electron microscopic (SEM) observations and energy dispersive spectrometer (EDS). The results showed that hardness of the alloy was raised to 90% and 68% of its solution state value by isothermal aging at 300 ◦C and 400 ◦C, respectively. However, aging at 500 ◦C led to a decrease in the hardness of the alloy. Moreover, while age hardening at 300◦C occurred due to coherency strains between the (111) plane of Ag-rich and the (111) plane of Cu3Pd phases, the mechanism of aging at 400◦C was the formation ofCu3Pd superlattice with the L12-type crystal structure. In contrast, reduction of Cu3Pd phase and formation of Cu solid solution decreased hardness during aging at 500oC. تفاصيل المقالة -
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12 - An Investigation Into the Effects of Friction and Anisotropy Coefficients and Work Hardening Exponent on Deep Drawing With FEM
R Hosseini A Ebrahimi mamaghani A AsaLarge strains, anisotropy of mechanical properties of materials and Coulomb friction in contact regions are some properties in the analysis of deep drawing process. In this research, the effects of different parameters such as anisotropy coefficient, work hardening expo أکثرLarge strains, anisotropy of mechanical properties of materials and Coulomb friction in contact regions are some properties in the analysis of deep drawing process. In this research, the effects of different parameters such as anisotropy coefficient, work hardening exponent and friction coefficient on deep drawing process of drawing quality steel are studied. For this purpose, the finite element method (FEM) to simulate the process is used. A 2D finite element simulation (axis symmetric) in ABAQUS is done and the results are validated with valid appropriate reference. Then Forming Limit Diagrams (FLD) for different friction coefficients, different anisotropy coefficients and different work hardening exponents are obtained. Finally, changes in FLD are discussed and it is observed that the friction coefficient is the most effective parameter on FLD and anisotropy coefficient and work hardening exponent are the least effective parameters on FLD. تفاصيل المقالة -
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13 - Effect of Overage Hardening Heat Treatment on the Micro Structure and Hardness of Nickel-based Super Alloy Rene-80
Mahmoud Moradi Mohammad Meghdad Fallah Fallah Mahdi Kazazi Mahdi VahdatiRene-80 nickel-base superalloy as an alloy for production of the jet turbine blades shows high mechanical properties as well as microstructure stability during the high temperature engine operation. In this research, age hardening heat treatment cycle was done on the as أکثرRene-80 nickel-base superalloy as an alloy for production of the jet turbine blades shows high mechanical properties as well as microstructure stability during the high temperature engine operation. In this research, age hardening heat treatment cycle was done on the as-cast Rene-80 superalloy. In the following, microstructure, elemental analysis of phases and macro-hardness of the alloy before and after of heat treatment were compared together with scanning electron microscopy (SEM) observation, X-ray spectrometry (EDS) and hardness test, respectively. The obtained results showed that γ’ carbide particles in the as-cast alloy had cubic morphology, while these particles showed more spherical morphology after heat treatment and also the amount of this phase was reduced after heat treatment. Based on hardness test results, hardness of as-cast sample was reduce from 38.17 to 35.01 HRC after age hardening heat treatment, which can be due to the reduction of carbide particles and their morphological modification. تفاصيل المقالة -
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14 - Design of Low-Pass Filter of X-Ray Energy to Improve the Quality of Medical Imaging
Sasan Soudi Bahareh Khaksar Jalali Hossein EshghifardUsing narrow-spectrum energy bandwidth can be effective on image quality. Because while increasing the possibility of processing the attenuation coefficient, it also provides a reduction in the beam hardening artifact. For this purpose, in this paper, energy absorption أکثرUsing narrow-spectrum energy bandwidth can be effective on image quality. Because while increasing the possibility of processing the attenuation coefficient, it also provides a reduction in the beam hardening artifact. For this purpose, in this paper, energy absorption filters are used by planning absorption and attenuation curves and sudden changes in attenuation in the interaction of the beam on the edges, as well as considering the operating conditions of existing imaging devices and the best energy required for imaging a specific part of the body. Then, their images were compared with the recorded images without filters and were approved by clinical experts. The samples, on the other hand, were designed with Monte Carlo N-particle radiation transport computer code (MCNP4C), which showed an acceptable agreement with the computational cases. تفاصيل المقالة -
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15 - Study on Nut Shell Lignification Progress in Hazelnut (Corylus avellana L.) cv. Segorbe
Julien Toillon Julie Robin Maud Thomas Rachid HamidiSeed protection is a key element in plant survival and plant dispersion. In hazelnuts, shell lignification begins from the tip to the basal scar. Therefore, hardening time is a race between seed survival against environmental stress. While new pests and stochastic weath أکثرSeed protection is a key element in plant survival and plant dispersion. In hazelnuts, shell lignification begins from the tip to the basal scar. Therefore, hardening time is a race between seed survival against environmental stress. While new pests and stochastic weather events are increasing, fundamental shell lignification features are missing in the common Segorbe cultivar. In this purpose, progress of lignification was studied using hardness and morphological changes in fresh and dried Segorbe hazelnuts collected weekly in 2020 and 2021, respectively. The growing degree days (GDD) were calculated for key lignification process stages. In dried hazelnuts, the lignification process causes morphological deformation lead to belted hazelnut symptoms. Lignification increased progressively from week 22 (1353.6 GDD) to week 26 (1353.6 GDD). Shell length was 48–84% of their final size. The shell was fully lignified at week 27 with a kernel size of 4.99±0.32 mm. In fresh nuts, shell size increased from 83 to 92%, and hardening increased by a factor of 2.85, reaching 21 kgf, between weeks 25 and 26 (2272.8 GDD), with a kernel size of 4.75±2.05 mm. Lignification occurs in four weeks. When kernel size is ~5 mm, and shell growth ends, a hard wall protects the kernel from stressors. Belted hazelnut symptoms, reflected in the ratio of lignified and shriveled shell parts, and shell hardness, are discussed in the context of the susceptibility of Segorbe cultivars to environmental stressors. تفاصيل المقالة -
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16 - مشخصه یابی فازی، ریزساختاری و بازدهی سختکاری سطحی فولاد ابزار SKS3 سختکاری شده توسط لیزر دیودی توان بالا
امیرسالار دهقانی امیررضا فرنیا محمد جواد ترکمنیدر این پژوهش، سختکاری سطحی فولاد ابزار سرد کار SKS3 توسط لیزر دیودی توان بالا با توان بیشینهی 1600 وات انجامگرفته است. توان های اعمالی (1200 و 1450 وات)، سرعتهای روبش (6/1 الی 3 میلیمتر بر ثانیه) و فاصلههای 55، 70 و 75 میلیمتر بهعنوان پارامترهای آزمون اعمال شدند أکثردر این پژوهش، سختکاری سطحی فولاد ابزار سرد کار SKS3 توسط لیزر دیودی توان بالا با توان بیشینهی 1600 وات انجامگرفته است. توان های اعمالی (1200 و 1450 وات)، سرعتهای روبش (6/1 الی 3 میلیمتر بر ثانیه) و فاصلههای 55، 70 و 75 میلیمتر بهعنوان پارامترهای آزمون اعمال شدند. بررسیهای ریزساختاری، آنالیز فازی و ریز سختی سنجی به ترتیب توسط میکروسکوپهای نوری و الکترونی، پراش پرتوی ایکس و ریز سختی سنجی انجامشده است. بررسیهای ریزساختاری و فازی نشان داد که فرآیند سختکاری منجر به ایجاد ساختار دوفازی مارتنزیت و آستنیت باقیمانده شد. استفاده از لیزر هر سه حالت سختکاری سطحی، ذوب سطحی و عدم سختکاری را ایجاد کرده است. بهترین ترکیب عمق و عرض سختکاری برای نمونههایی با چگالی انرژی J/mm2 250-208 ایجاد شد. محاسبهی درصد فاز آستنیت باقیمانده و گرمای ورودی، مشخص کرد که با افزایش گرمای ورودی، درصد آستنیت باقیمانده افزایش مییابد بهگونهای که برای نمونه با بیشترین گرمای ورودی، درصد فاز آستنیت باقیمانده در حدود 37 درصد محاسبه شد، همچنین برای نمونه با بیشترین گرمای ورودی ( J/mm2/906)، کمترین میزان سختی حاصلشده است (653 ویکرز) و بیشترین سختی (760 ویکرز) برای نمونهای بوده است که دارای گرمای ورودی پایینتری ( J/mm725) بوده است. بررسیهای مقادیر بازده سختکاری1 مشخص کرد که صرفاً با افزایش چگالی انرژی لیزر، شرایط سختکاری بهبود نمییابد بلکه برای حصول بالاترین سختی و ریزساختار مناسب، مقدار بهینهی توان و سرعت اسکن موردنیاز است. تفاصيل المقالة -
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17 - شبیهسازی فرآیند پیرسازی سوپرآلیاژ Ni-Span C 902 نورد سرد شده
محمدرسول معظمی گودرزی مریم مرکباتی سید مهدی عباسی حسن بدریهدف از پژوهش حاضر بررسی و پیش بینی تغییرات سختی سوپرآلیاژ Ni-Span C 902 نورد سرد و پیرسازی شده در دماها و زمان های مختلف پیرسازی می باشد. در این راستا نمونه های آنیل شده به میزان 50 درصد نورد سرد و به مدت زمان های 105-102 ثانیه در محدوده دمایی C°750-450 تحت عملیات پ أکثرهدف از پژوهش حاضر بررسی و پیش بینی تغییرات سختی سوپرآلیاژ Ni-Span C 902 نورد سرد و پیرسازی شده در دماها و زمان های مختلف پیرسازی می باشد. در این راستا نمونه های آنیل شده به میزان 50 درصد نورد سرد و به مدت زمان های 105-102 ثانیه در محدوده دمایی C°750-450 تحت عملیات پیرسازی قرار گرفتند. تاثیر دما و زمان پیرسازی بعنوان پارامتر پیرسازی و کارسرد روی رفتار استحکام دهی آلیاژ توسط روش شبکه عصبی مصنوعی (ANNs) شبیه سازی و مورد بررسی قرار گرفت. رفتار سخت شدن، فوق پیری و نرم شدن حین پیرسازی توسط مدل ANN مشخص شد. حداکثر درصد نسبی سخت شدن برای آلیاژ نورد سرد نشده و 50 درصد نورد سرد شده به ترتیب در محدوده پارامتر پیرسازی 22 و 21 بدست آمد. تفاصيل المقالة -
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18 - Solution of Nonlinear Hardening and Softening type Oscillators by Adomian’s Decomposition Method
بهرام گل محمدی قاسم اسعدی کردشولی علیرضا وحیدیA type of nonlinearity in vibrational engineering systems emerges when the restoring force is a nonlinear function of displacement. The derivative of this function is known as stiffness. If the stiffness increases by increasing the value of displacement from the equilib أکثرA type of nonlinearity in vibrational engineering systems emerges when the restoring force is a nonlinear function of displacement. The derivative of this function is known as stiffness. If the stiffness increases by increasing the value of displacement from the equilibrium position, then the system is known as hardening type oscillator and if the stiffness decreases by increasing the value of displacement, then the system is known as softening type oscillator. The restoring force as a nonlinear polynomial function of order three, can describe a wide variety of practical nonlinear situations by proper choosing of constant multipliers. In this paper, a spring-mass system is considered by the restoring force of the introduced type. Choosing suitable values for a, b and n, a hardening and softening type oscillators are constructed and related equations of motion are introduced as second order nonlinear differential equations. The equations are solved directly, using the Adomian’s decomposition method (ADM). In another approach, the equations are converted to systems of first order differential equations and then solved using the same method. The results show that the ADM gives accurate results in both approaches, beside it shows that converting the equation to a system of equations of lower order, tends to more accurate solutions when ADM applies. تفاصيل المقالة
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