finite element simulation
در نشریات گروه مواد و متالورژی-
This study investigates the deformation behavior of commercially pure aluminum using finite element analysis, focusing on the combined equal channel angular pressing (ECAP) and extrusion process. The objective is to analyze the effects of die angle, extrusion ratio, and friction coefficient on the process and the resulting material properties. The findings indicate that a smaller die angle, higher extrusion ratio, and increased friction coefficient all contribute to a greater required process force. While friction between the sample and die wall disrupts uniform plastic strain distribution, increasing the die angle up to 110° and using an extrusion ratio of 6.25 enhance strain uniformity.
Keywords: Severe Plastic Deformation, Extrusion, Equal Channel Angular Pressing, Finite Element Simulation -
The present research study explores the mechanical properties of poly lactic acid (PLA) composites reinforced with multi-walled carbon nanotubes (MWCNTs), focusing on their performance in triangular, inclined, and curved support bracket geometries. Tensile tests revealed that tensile stress increases with MWCNT concentrations up to 3 wt.%, but decreases at 5 wt.%. Enhanced mechanical performance at lower concentrations is attributed to uniform CNT dispersion within the PLA matrix, facilitating effective load transfer. Conversely, at 5 wt.%, MWCNT agglomeration disrupts matrix continuity, leading to weaker mechanical properties. The alignment of CNTs with the loading direction significantly influences the performance, with 0° printing angles yielding higher tensile strength due to optimized load transfer. The geometric configuration of the brackets further affects deflection behavior; maximum deflections were observed to decrease with increasing MWCNT content, particularly at 3 wt.%, but slightly increase at 5 wt.%, indicative of reduced stiffness due to aggregation. This work emphasizes the importance of both CNT concentration and geometric design in optimizing the mechanical characteristics of PLA/MWCNT composites; that revealing how to vary geometries impact stress distribution on overall performances.Keywords: 3D Printing, Poly Lactic Acid Composites, Multi-Walled Carbon Nanotubes, Finite Element Simulation, Nanocomposites
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Surface roughness significantly affects the scattering of load-displacement curves and the measurement of mechanical properties by the macro-scale indentation. Many mechanical properties such as modulus of elasticity, yield stress, strain hardening exponent, and hardness can be determined using the indentation results, which are the information obtained from the load-displacement curve. Reliable parameters of the load-displacement (P-h) curve are employed to estimate the mechanical properties. The inaccurate P-h curve leads to a misestimation of material properties. Ignoring the surface roughness might be a source of error in the indentation results. In this paper, the effects of surface roughness on the P-h curve of macro spherical indentation and Brinell hardness number (BHN) were studied. The range of roughness with minimal effect on indentation results was obtained. The surface roughness of 2 and 12 microns was created on the experimental samples using the electrical discharge machining (EDM) process. The finite element simulations were performed with different surface roughnesses. The results showed that roughness affected both the P-h curve and hardness values in different indentation depths and various indenter sizes. It was observed that with increasing the Rq roughness, the P-h curve level and hardness value decreased and that with increasing the indentation depth, the effect of roughness on hardness decreased as well. The neumerical results showed a good agreement with the results of experiments.
Keywords: Macro Spherical Indentation, Roughness, Brinell Hardness, Load-displacement Curve, Finite Element Simulation -
در این پژوهش یک روش عددی مبتنی بر المان محدود به منظور شبیه سازی توزیع تنش در پوشش سد حرارتی معمولی و درجه بندی شده NiCrAlY/YSZ(GZ) پاشش پلاسمایی شده بر روی زیرلایه اینکونل 738 توسعه یافت. معادلات انرژی و تنش- جابجایی در فضای دوبعدی به طور همزمان با استفاده از نرم افزار آباکوس حل شد. در بخش تجربی، پوشش سدحرارتی درجه بندی شده به روش پاشش پلاسمایی اعمال شد و رفتار نمونه در برابر شوک حرارتی مطالعه شد. با استفاده از روش نانوفرورونده میزان تنش پسماند اندازه گیری شد و با نتایج عددی مقایسه و صحت محاسبات با آن تایید شد. نتایج نشان داد که با افزایش دامنه فصل مشترک پوشش سد حرارتی، ماکزیمم تنش ابتدا کاهش یافته و سپس با افزایش بیشتر دامنه، افزایش می یابد. نتایج حاصل از بررسی تاثیر ضخامت پوشش سد حرارتی بر توزیع تنش نشان داد با افزایش ضخامت ماکزیمم تنش افزایش می یابد. مقایسه توزیع تنش در پوشش های YSZ و GZ نشان داد کاربرد پوشش GZ تنش پسماند را افزایش می دهد.
کلید واژگان: اندازه گیری تنش، روش نانوفرورونده، شبیه سازی، پوشش سدحرارتی درجه بندی شدهIn this study, a finite element numerical method was developed to simulate the stress distribution in the conventional and functionaly graded NiCrAlY / YSZ (GZ) plasma sprayed thermal barrier coating on the Inconel 738 substrate. Residual stress was measured using the nanoindentation method and the results used for verification of the numerical results. The results showed that with increasing the amplitude of the interface, the maximum stress decreases and then increases with further amplitude increment. The maximum residual stress increases with increasing thickness. Comparison of stress distribution in YSZ and GZ coatings showed that the use of GZ coating increases residual stress.
Keywords: Residual stress measurement, Nanoindentation method, FG-TBC, Finite element simulation -
Micro-stamping process is one of the most cost-effective methods to manufacture metallic bipolar plates (BPPs). This research investigates the forming of titanium thin sheet as a potential candidate for BPPs in proton exchange membrane fuel cell (PEMFC). In this regard, the process was first simulated using finite element (FE) code Abaqus. Afterward, experimental tests were implemented and the validation of the FE model was confirmed using the experimental results. In the simulations, the corner radius of the die, draft angle, and friction coefficient at die/sheet interface were selected as variable factors. Forming force and thickness reduction as response functions were evaluated. It is demonstrated that the die corner radius has more influence on the maximum punch force compared to the draft angle and friction coefficient. The maximum punch force decreases with increasing the die corner radius. On the other hand, in order to have a lower thickness reduction, a high die corner radius, higher draft angle, and low friction coefficient are required.Keywords: Bipolar Plates, Titanium Sheet, Finite element simulation, Micro-stamping
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تغییر شکل پلاستیک شدید یکی از روش های موثر در کاهش اندازه دانه های مواد فلزی و دست یابی به مواد فوق ریزدانه و نانوساختار می باشد. در مقاله حاضر تغییر شکل پلاستیک شدید از طریق ترکیبی از اکستروژن و پرس در کانالهای زاویه دار هم مقطع بر روی مواد مختلف مانند مس خالص تجاری، آلیاژ آلومینیم 7075، فولاد میکروآلیاژی و فولاد ساده کربنی فریتی به طور موفقیت آمیزی اعمال شد. با بررسی ریزساختار حاصل از تغییر شکل در دمای محیط از طریق میکروسکوپ نوری و پراش پرتو ایکس قابلیت این روش در فرآوری مواد نانوساختار به اثبات رسید. اندازه متوسط دانه ها در آلیاژ آلومینیم 7075 در حدود 160 نانومتر و فولاد ساده کربنی در حدود 125 نانومتر محاسبه شد. همچنین تغییر شکل از طریق این روش بر روی آلیاژ آلومینیم 7075 و فولاد ساده کربنی در دمای بالا اعمال شد. در مورد آلیاژ آلومینیم 7075 از طریق وقوع تبلور مجدد دینامیکی اندازه متوسط دانه ها تا 6 میکرومتر کاهش پیدا کرد. علاوه بر این تغییر شکل فولاد ساده کرینی با دمای پیشگرم 930 درجه سانتیگراد نشان داد که اندازه دانه ها در این فولاد را می توان از طریق وقوع استحاله تحت کرنش دینامیکی آستنیت به فریت تا 3 میکرومتر کاهش داد. مشخصه های تغییر شکل فرآیند تلفیقی اکستروژن-پرس در کانالهای زاویه دار هم مقطع از طریق شبیه سازی المان محدود مورد بررسی قرار گرفت. با استفاده از نتایج تحلیل المان محدود نحوه توزیع کرنش در نمونه های تغییر شکل یافته مطالعه شد.کلید واژگان: اکستروژن، پرس در کانالهای زاویه دار هم مقطع، تحلیل المان محدود، مواد نانوساختارSevere plastic deformation is one of the most effective methods of grain refinement which can be used for processing of ultra fine grained and nanostructured metallic materials. In the present study the combination of extrusion and equal channel angular pressing is imployed for severe plastic deformation of materials. Using this method, a severe plastic deformation was imposed succesfully on pure copper, Al7075 alloy, plain low carbon and microalloyed steels. The cabability of the proposed methode in production of nanostructured materials was approved by anallyzing the obtained microstructures of processed samples with opticaal microscopy and X-ray diffraction spectroscopy. The mean crystallite size of processed Al7075 alloy and plain low carbon steel was meassured to be 160 and 125 nm respectively. Also, the plastic deformation was applied on these materials at high temperatures. In the case of Al7075 alloy the microstructure was refined to the mean grain size of 6 µm through the occurance of dynamic recrystallization during deformation at the preheating temperature of 250 ̊C. Also, the plastic deformation of plain carbon steel at the preheating temperature of 930 ̊C demonstrated that the microstructure can be refined to 3 µm through dynamic strain induced transformation of austenite to ferrite. Moreover, the plastic deformation characteristics of combined extrusion-equal channel angular pressing was studied using finite element simultion. The formation of superficial cracks on the topside of Al7075 sample was also predicted using the FEM analysis.Keywords: Extrusion, equal channel angular pressing, finite element simulation, nanostructured material
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در این پژوهش، به منظور مشخصه یابی رفتار تغییر شکل یک فولاد ضدزنگ آستنیتی AISI 321 حین فرایند پیلگر، شبیه سازی المان محدود انجام شد و نتایج آن با مقادیر تجربی مورد مقایسه قرار گرفت. تاثیر پارامترهای فرایند، شامل نرخ تغذیه (چهار و هشت میلی متر) و زاویه چرخش (15، 30 و 60 درجه) در مقدار آسیب ایجاد شده نیز ارزیابی شد. به منظور شبیه سازی رفتار سیلان ماده از مدل جانسون-کوک استفاده شد. در ادامه با درنظر گرفتن تنش های فشاری زیربرنامه بهبود یافته ای از مدل آسیب لاتام-کاککرافت محاسبه و برای تعیین پارامترهای بهینه فرایند مورد استفاده قرار گرفت. نتایج نشان داد که کرنش های شعاعی و محیطی در تمامی شرایط فشاری و کرنش محوری کششی است. مقدار کرنش ایجاد شده (صرف نظر از حالت فشاری یا کششی آن) نیز در سطح خارجی لوله در مقایسه با سطح داخلی بیشتر است. با درنظر گرفتن تعداد سیکل های خستگی یک المان لوله حین فرایند، نرخ تغذیه هشت میلی متر، زاویه چرخش 60 درجه و کمترین ضریب اصطکاک به عنوان پارامترهای بهینه تعیین شدند.
کلید واژگان: فرایند پیلگر، شبیه سازی المان محدود، فولاد زنگ نزن 321، آنالیز تخریبFinite element (FE) simulations in conjunction with experimental analysis were carried out to characterize the deformation behavior of an AISI 321 austenitic stainless steel (ASS) during cold pilgering process. The effect of process parameters including feed rate (4 and 8 mm) and turn angle (15, 30 and 60°) on damage build-up were also evaluated. The Johnson-cook model was used to simulate the flow behavior of material. By considering compressive stresses, a new revised Latham-Cockcraft damage was calculated and used to determine the optimum process parameters. It was found that the radial and hoop strains in all friction conditions were compressive, while the axial strains were observed to be tensile. The amount of strain (whether it is compressive or tensile strain) was also higher on the outside of the tube compared to its inside. By considering fatigue cycles of a tube element during the process, the feed rate of 8mm, turn angle of 60° and the lowest coefficient of friction were determined as optimum parameters.
Keywords: Pilgering process, Finite element simulation, AISI 321 statinless steel, Damage analysis -
مجله مهندسی متالورژی، پیاپی 75 (پاییز 1398)، صص 215 -224در این تحقیق تاثیر ضریب کارسختی بر روی نحوه سیلان فلز و توزیع کرنش، فاکتور تخریب و نیروی لازم برای پرس نمونه با استفاده از تحلیل المان محدود مورد بررسی قرار گرفت. نتایج حاصل نشان داد در مورد ماده پلاستیک ایده آل منطقه پر نشده از فلز در محل تقاطع کانالها ایجاد نمی شود و کرنش اعمالی به ناحیه پایینی نمونه از سطح بالایی بیشتر است. در حالیکه با افزایش ضریب کارسختی اندازه ناحیه پر نشده افزایش یافته و کرنش کمتری به قسمت پایینی نمونه اعمال می شود. همچنین فاکتور تخریب در نمونه با رفتار پلاستیک ایده آل در سطح بالایی نمونه نسبت به نواحی دیگر بالا بوده و در این ناحیه تنشهای کششی نیز اعمال می شود. برعکس درمورد نمونه ای با رفتار کارسختی، بیشترین فاکتور تخریب مربوط به ناحیه نیمه پایینی نمونه است. از طرفی مشاهده شد با افزایش ضریب کارسختی میزان نیروی لازم برای پرس نمونه کاهش می یابد.کلید واژگان: پرس در کانالهای زاویه دار هم مقطع، تحلیل المان محدود، ضریب کارسختی، فاکتور تخریبJournal of Iranian Metallurgical and Materials Engineering Society, Volume:22 Issue: 75, 2019, PP 215 -224In the present study, the effect of srain hardening exponent os material on flow characteristics, strain and damage distribution in sample and the load requred for the execution of the deformation process was investigated using finite element simulation. Results showed that the corner gap is not formed during deformation of ideally plastic material and the amount of eauivalent strain is higher in the bottom side of sample compared with other regions. However, with increassing the work hardening exponent, the size of corner gap increases and the bottom side recieves less amount of strain. Also, damage factor in the sample of idealy plastic material is higher at the top side compared with other regions and the tensile stresses are aplliyed on this area. Whereas, in the strain hardened material the higher damage factor was observed at the lower half of the sample. Finally. it was concluded that the pressing force increases with increassing the work hardening exponent.Keywords: Equal channel angular pressing, finite element simulation, work hardening, Damage
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Since tubes have numerous industrial applications, different attempts are focused on the severe plastic deformation processes of tubes. As an illustration, tube channel pressing (TCP) is an attractive process for this purpose since it can be used for processing of different sizes of tubes. However, more attempts are needed to improve the outcomes of TCP. For example, imposing of a greater strain besides reductions of the strain heterogeneity are the challenges of this process. This work is aimed to optimize the die geometry of TCP through a finite element simulation procedure verified by experiments in order to increase the imposed strain as well as to decrease the strain heterogeneity. Results show that the increase of die curvature radius causes decrease of imposed plastic strain and increase of strain heterogeneity. In addition, the minimum amount of die convex height for imposing of a reasonable strain through TCP is calculated considering the tube thickness and the channel angle. Besides this, the optimum die geometry is recommended in order to minimize the strain heterogeneity.Keywords: Severe plastic deformation, Finite element simulation, Strain analysis
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In the present investigation, an artificial neural network (ANN) model is developed to predict the isothermal hot forging behavior of AlCuMgPb aluminum alloy. The inputs of the ANN are deformation temperature, frictional factor, ram velocity and displacement whereas the forging force, barreling parameter and final shape are considered as the output variable. The developed feed-forward back-propagation ANN model is trained with Leven berg–Marquardt learning algorithm. Since the finite element (FE) simulation of the process is a time-consuming procedure, the ANN has been designed and the outputs of the FE simulation of the hot forging are used for training the network and then, the network is employed for prediction of the behavior of the output parameters during the isothermal forging process. Experimental data is compared with the FE predictions to verify the model accuracy. The performance of the ANN model is evaluated using a wide variety of standard statistical indices. Results show that the ANN model can efficiently and accurately predict isothermal hot forging behavior of AlCuMgPb alloy. Finally the extrapolation ability and noise sensitivity of the ANN model are also investigated. It is found that the extrapolation ability is very high in the proximity of the training domain, and the noise tolerance ability very robust.Keywords: AlCuMgPb aluminum alloy, isothermal hot forging, artificial neural network, finite element simulation
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Pyroplastic deformation is a distortion of the ceramic shape during the sintering process. It occurs because the flow of the vitreous phase at high temperature and the applied stress due to the weight of the product during sintering process. The aim of this paper deals with describing a numerical-experimental method to evaluate the pyroplastic deformation, to predict the anisotropic shrinkage and heterogeneous densification for ceramic materials during the liquid phase sintering process, as a function of sintering time. For this purpose, three experimental configurations including midpoint deflection, sinter bending and free sintering test were designed; the finite element method are implemented by the CREEP user subroutine code in ABAQUS. The fair accordance between simulation results and experimental data reveals that the shear and bulk viscosity modulus as well as dynamic viscosity used in the simulation are near the real ones. The anisotropic shrinkage factor K_xy has been proposed to investigate the shrinkage anisotropy. It has been shown that the shrinkage along the normal axis of slip casting is about 1.5 times larger than that of casting direction. The inhomogeneity in Von-Misses, pressure, and principal stress intensifies the density non-uniformity in the samples.Keywords: Pyroplastic deformation, Finite element simulation, Heterogeneous densification, Sintering, Anisotropy shrinkage
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امروزه شکل دهی لوله های چندلایه با توجه به کاربرد گسترده آن در صنایع هوافضا، نفت و پتروشیمی و بررسی شکل پذیری آن توسط فرآیندهای مختلف شکل دهی مورد توجه محققان قرارگرفته است. در این پژوهش بررسی مقایسه ای شکل پذیری لوله های دولایه کامپوزیت فلزی در فرآیند شکل دهی سرد و داغ در یک الگوی هندسی بالج قالب بسته، تحت تاثیر شرایط فرآیندی آزمایش هیدروفرمینگ و دمش گاز مورد مطالعه قرارگرفته است، به طوری که نحوه عملکرد هریک از فرآیندها در شکل دهی لوله های دولایه مس (داخل)- آلمینیوم (خارج)، بر میزان چروکیدگی، پارگی، کمانش و کنترل توزیع ضخامت در محدوده پروفیل قالب بالج شکل، در حالت های مختلف مورد بررسی قرارگرفته است. فرآیند هیدروفرمینگ در دمای محیط و ماکزیمم فشار 300 بار انجام شده است. همچنین فرآیند دمش گاز در دمای 550 درجه سانتیگراد و فشار 40 بار صورت پذیرفته است. نسبت انبساط لوله دولایه در فرآیند دمش گاز، در حالت مقایسه ای با فرآیند هیدروفرمینگ به میزان 1.35 درصد افزایش و قبل از پرشدگی قالب دچار ترکیدگی شده است. نمونه سالم بالج قالب بسته در فرآیند هیدروفرمینگ با فشار شکل دهی 280 بار و الگوی بارگذاری خطی 6 میلی متر، ماکزیمم نازک شدگی به مقدار 1.65 میلی متر شکل داده شده است.کلید واژگان: شکل دهی سرد و داغ، هیدروفرمینگ لوله، شکل دهی با گاز، شبیه سازی المان محدودNowadays the formability of multi-layered tubes through different kinds of forming processes has been of interest to researchers due to its vast applications in aerospace, oil and petrochemical industries. This study compares cold forming and hot forming of bi-layered composite tubes via hydroforming and gas blow forming the tubes in geometrical model of a closed die bulge. The effect of these forming processes operational conditions on the bi-layered copper (inside) aluminum (outside) tubes forming, wrinkling, bursting, buckling and the thickness distribution controlling on the die profile region in various situations were investigated. Hydroforming process was executed at ambient temperature with the maximum pressure of 300 bar. The process of blow gas forming at 550 ° C temperature and 40 bar pressure was implemented. The expansion ratio of the bi-layered tube during the gas blow forming process exceeded 1.35 % in comparison that of hydroforming process. In addition, the die experienced burst before the fitting during the gas blow forming process. The undamaged closed die bulge was formed through 280 bar hydroforming process with the conditions of 6 mm linear loading and 1.65 mm maximum thinning.Keywords: Cold, Hot Forming, Tube Hydroforming, Gas Forming, Finite Element Simulation
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توزیع دما و تنش های پسماند در پوشش سد حرارتی سه لایه (La2Zr2O7/8YSZ/NiCrAlY) تحت یک چرخه حرارتی ترکیبی و واقعی به کمک نرم افزار تجاری اباکوس شبیه سازی شد. از تکنیک کاهش زمان حل به روش مقیاس دهی جرمی برای جلوگیری از اعوجاج بیش از حد مش-بندی، کاهش خطای عددی و واگرایی استفاده گردید. نتایج نشان داد که استفاده از روش افزایش جرم المان ها و جابجایی گره ها بصورت تطبیق پذیر باعث افزایش سرعت حل می شود که دلیل آن بزرگتر شدن نموهای حلی در فرایند است. نتایج شبیه سازی نشان داد که تنش های پسماند در منطقه پوشش محافظ و نه زیرلایه تمرکز یافته است و این به نوبه خود باعث بهبود و افزایش عمر این محصول محافظ می باشد. تحلیل عددی نشان داد که بیشترین میزان اعوجاج بصورت عمده در ناحیه پوششهای سرامیکی متمرکز شده است.کلید واژگان: پوشش سد حرارتی، تنش پسماند، شبیه سازی المان محدود، شوک حرارتیAn attempt was made to investigate the thermal and residual stress distribution in a novel three layer (La2Zr2O7/ 8YSZ/ NiCrAlY) during a real-like heating regime. The technique of reduction of solving time like mass scaling leads to a considerable reduction in running time while satisfying and not violating accuracy and converging criteria and constrains. Simulation results indicated that, most of damaging and harmful distortion and residual stress concentrate on ceramic top coats and this lead less harm and life time reduction in substrate.Keywords: Thermal barrier coating, Residual stresses, Finite element simulation, Thermal shock
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In this paper, torsion extrusion (TE) process on 1050 aluminum alloy was investigated by simulation as a severe plastic deformation (SPD) method and the effects of friction coefficient, angular velocity of the rotating die and punch speed on maximum punch force were studied. A finite element (FE) model was developed to simulate the TE process via DEFORM software. The FE results were validated compared with experimental results and then the FE model was used for implementing the set of simulations designed by Taguchis L9 orthogonal array. Maximum punch force was determined and put into signal to noise (S/N) ratio and the analysis of variance (ANOVA) techniques to specify the importance and contribution of parameters. The results indicated that the friction coefficient has the most effect on maximum punch force and effects of the angular velocity and punch speed are not sensible. Results analysis represented that maximum punch force enhances by increasing the friction coefficient. Moreover, friction coefficient of 0.18, angular velocity of 0.11 rad/s and punch speed of 0.2 mm/s lead to the minimum punch force.Keywords: Torsion Extrusion, Maximum Punch Force, Finite Element Simulation, Taguchi Method
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Kevlar is a type of aramid fibers which is characterized by high strength to low weight ratio. This material is widely used in bulletproof vests and helmets, in which it creates a barrier to projectiles to protect specific objectives, laminated tubes and pressure vessels, etc. In this study the ballistic behavior of Kevlar /epoxy composite and Kevlar fabric is investigated. The results showed that Kevlar fabrics were more resistant against projectiles. Tensile and punch tests revealed that although the Kevlar/Epoxy composite enjoys higher strength, undergoes lower deformation than Kevlar fabric. The results also indicated that the failure mechanism of Kevlar fabric was quite ductile whereas the presence of epoxy in Kevlar/epoxy changed the failure mechanism from ductile to brittle in the form of plugging in ballistic tests. Finally, the ballistic behavior of the Kevlar fabric was simulated by ABAQUS finite element software and the results were validated by the experiment.Keywords: Kevlar fiber, Finite element simulation, Kevlar, Epoxy, Ballistic
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در پژوهش حاضر، یک نوع فولاد ساده کربنی با ساختار فوق ریز دانه با اعمال یک فرایند ترمومکانیکی موثر در گستره دمایی آستنیت شبه پایدار (Ae3-Ar3) و با استفاده از روش تلفیقی اکستروژن - پرس در کانال های زاویه دار با مقاطع همسان فراوری شد. در ابتدا با استفاده از تحلیل المان محدود سه بعدی دما - جابه جایی، تاثیر دمای پیشگرم در توزیع کرنش و دما در نمونه های تغییر شکل داده شده مورد بررسی قرار گرفت. با استفاده از نتایج به دست آمده، دمای 930 درجه سانتی گراد به عنوان مناسب ترین دمای پیشگرم برای دستیابی به ساختار فوق ریز دانه از طریق وقوع دگرگونی دینامیکی آستنیت به فریت انتخاب شد. با اعمال تغییر شکل بر روی فولاد مورد نظر در این دمای پیشگرم و بررسی ریزساختار نهایی، نتایج حاصل از تحلیل المان محدود مورد تایید قرار گرفت. نتایج نشان داد که در اثر این فرایند ترمو مکانیکی اندازه دانه های فریت از 32 میکرومتر در ساختار اولیه به 1 تا 3 میکرومتر پس از اعمال فرایند کاهش پیدا می کند.کلید واژگان: تحلیل المان محدود، تغییر شکل پلاستیک شدید، فولاد فوق ریز دانهIn the present research, an effective thermo-mechanical processing route in the temperature range of metastable austenite region (Ae3Keywords: Finite element simulation, Severe plastic deformation, Ultra, fine grained steel
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The scientific importance of nanocomposites is being increased due to their improved properties. This paper is divided into two parts. First, Al-Al2O3 nanocomposite was produced by using ball milling technique followed by cold compaction and sintering. Microstructure and morphology studies were done through SEM, TEM, and EDX analyses on the produced powder. The mechanical properties of the produced composite were determined by the tensile test. Also, nano-indentation experiment was conducted on the produced composite to determine its hardness. Second, a 2-D axisymmetry model was implemented in ANSYS software to simulate the nano-indentation experiment on pure aluminum and Al-Al2O3 nanocomposite. A conical indenter with 70.3◦ was considered in simulations. The results show that, a homogenous distribution of the reinforcement in the matrix was achieved after 20 h milling. The elastic modulus, yield strength, and the hardness of the produced composite were increased compared to the pure metal. The finite element (FE) simulation results showed a good agreement with the experimental results for nano-indentation experiment. The scatter of the FE results from the experimental results in the pure metal was smaller than that observed for the nanocomposite.Keywords: Nanocomposite, Mechanical Milling, Finite Element Simulation, Hardness
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Plastic deformation of 7075 Aluminum Alloy using Integrated Extrusion-Equal Channel Angular PressingGrain refinement improves the mechanical properties and formability of metals and alloys. So far, several different grain refinement methods have been proposed and studied. Severe plastic deformation is one of the most promising and efficient methods. Therefore, in the present study the possibility of imposing a two-step severe plastic deformation (Extrusion and Equal channel angular pressing) on AA7075 alloy using a special designed die is investigated. Using this method, a very coarse grained microstructure with grain size of 94µm is refined to grain size of 7.5µm. Also, microstructural developments during severe deformation with and without preheating are investigated. Plastic strain distribution and temperature variation inside deformed samples are predicted by the use of thermal coupled displacement 3D finite element method. Results of FEM simulations clearly showes that the plastic strain distribution and temperature is non-uniform in sample and this introduces inhomogeneity in the resultant microstructure of sample at different regions.Keywords: severe plastic deformation, 7075 aluminum alloy, finite element simulation
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n this paper a finite element model has been proposed for evaluation of primary and secondary current density values on the cathode surface in nickel electroplating operation of a revolving part. In addition, the capability of presented electroplating simulation has been investigated in order to describe the electroplated thickness of the nickel sulfate solution. Nickel electroplating experiments have been carried out. A good agreement between the simulated and experimental results was found. Also the results showed that primary current density can describe the general form of thickness distribution but the relative value of current density using secondary current density can present better description of thickness distribution.
Keywords: Nickel electroforming, finite element simulation, Thickness distribution, Primary current density -
Equal channel angular pressing (ECAP) is the most promising and effective method of severe plastic deformation thechniqus. In addition, materials with low doctility show severe cracking during ECAP and back pressure has been used in some research to overcome this problem. In this paper finite element has been used for simulation of ECAP with back pressure and the possibility of using ECAP die with inclined upper channel wall instead of back pressure. Results show that inclined up channel wall with 10 mm length and 5 degree inclination needs lower pressing foece and exert 100Mpa pressure on upeer side of sample. Therefore, die with inclination is suitable substitude for ECAP whith back pressure.Keywords: Equal Channel Angular Pressing, Finite Element Simulation, Back Pressure
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