به جمع مشترکان مگیران بپیوندید!

تنها با پرداخت 70 هزارتومان حق اشتراک سالانه به متن مقالات دسترسی داشته باشید و 100 مقاله را بدون هزینه دیگری دریافت کنید.

برای پرداخت حق اشتراک اگر عضو هستید وارد شوید در غیر این صورت حساب کاربری جدید ایجاد کنید

عضویت

جستجوی مقالات مرتبط با کلیدواژه « residual stress » در نشریات گروه « برق »

تکرار جستجوی کلیدواژه «residual stress» در نشریات گروه «فنی و مهندسی»
  • S. Sundriyal, Vipin Vipin, R. S. Walia *
    There are some undesired effects left in the machined products by electric discharge machining (EDM) and the most prominent among those is the residual stress. These induced residual stresses influence fatigue behavior, dimensional stability, and stress corrosion which is responsible for the failure of the machined product. It was observed that the products obtained by powder mixed near dry- EDM or (PMND-EDM) have a considerably low value of residual stress (RS). The objective of this research is to minimize the residual stresses induced in the machined workpiece (EN-31) by optimizing the process parameters which affects the machining characteristics significantly. Selected parameters were tool diameter, mist flow rate, metallic powder concentration, and mist pressure while the workpiece selected was EN-31 due to its desirable mechanical properties and immense applications in the manufacturing industry. The minimum value of residual stress at optimized values of process parameters was found to be 106.32 MPa.
    Keywords: Residual stress, EDM, Powder, Near dry, X-ray method}
  • میلاد آقایی عطار*، مجید قریشی

    شبیه سازی جوشکاری برای اتصال فلزات غیر همجنس به دلیل پیچیدگی های زیاد حین فرآیند به وسیله مدلسازی عددی توسعه چشمگیری یافته است. در این پژوهش فرآیند جوشکاری لیزر پیوسته دیسک جهت اتصال غیر همجنس فولاد زنگ نزن 304 به مس شبیه سازی شده است. برای این منظور مدلسازی جهت تخمین توزیع دما، پیش بینی هندسه و ابعاد سطح مقطع جوش شامل حوضچه جوش و ناحیه متاثر از حرارت با استفاده از توزیع شار حرارتی ترکیبی با کمک نرم افزار آباکوس و سابروتین نویسی دیفلاکس با زبان فرترن پیشنهاد میگردد. پارامتر های خروجی اتصال جوش از جمله توزیع دما، توزیع کرنش های الاستیک-پلاستیک، هندسه جوش و تنش های پسماند مورد بررسی قرار گرفتند. خروجی های شبیه سازی با مقایسه نتایج آزمایشگاهی گزارش شده سایر محققان برای سه پارامتر در سه سطح اعتبارسنجی شده است. خروجیهای مدل منبع حرارتی پیشنهادی با مقادیر اندازهگیری شده تجربی به خوبی تطابق داشته و دقت مدل عددی پیشنهادی را برای جوشکاری لیزری غیر همجنس نشان می دهد. مس به دلیل داشتن ضریب هدایت حرارتی بالاتر حین فرآیند و نیز پس از سرد شدن، حرارت بیشتری را از خود عبور داده و در نتیجه ناحیه متاثر از حرارت به دلیل پایینتر بودن دما در ناحیه مرکزی جوش، کوچکتر بوده و کرنش پلاستیک به طور میانگین در کل عرض مدل برای مس تقریبا 60 درصد یشتر از فولاد میباشد. پس از سرد شدن، تنش های پسماند طولی در ناحیه مرکزی برای هر دو جنس کششی بوده که به دلیل بالاتر بودن ضریب انبساط حرارتی فولاد نسبت به مس اندازه تنش ها نیز 23 درصد در مرکز جوش بزرگتر هستند.

    کلید واژگان: جوشکاری لیزر دیسک پیوسته, روش المان محدود, اتصال نامتجانس, تحلیل حرارتی-مکانیکی, تنش پسماند, توزیع کرنش الاستیک -پلاستیک}
    Milad Aghaee Attar *, Majid Ghoreishi

    In this study, a simulation is developed for dissimilar metal sheets followed by a numerical model for laser welding. The continuous disk laser welding process for dissimilar joining between 304 stainless steel and copper is simulated. For this purpose, double conical heat source distribution model was implemented into Abaqus/Standard solver using additional DFLUX subroutine written in the FORTRAN programming language in order to estimating the temperature distribution, prediction the geometry and dimensions of weld cross section including the fusion zone (FZ) and heat affected zone (HAZ). The weld joint output parameters such as temperature, strain distribution, residual stresses and weld geometry were examined. The validation of the simulation output results were confirmed by comparison with the experimental results by other researchers at three level with three input parameters. The results showed that copper, due to the higher thermal conductivity during cooling, passed through more heat at the same period of time, so these results lead to lower temperature in the center of FZ and a smaller HAZ in this dissimilar welding in comparison to similar welding. After cooling time, longitudinal residual stresses in the FZ for both materials were tensile also due to higher thermal expansion coefficient of steels, the quantity of stresses are 23% more than copper. The computed results are well agreed with experimentally measured values and show the robustness of the present numerical model used for dissimilar laser welding.

    Keywords: Continuous disk laser welding, finite element method, dissimilar joining, molten pool geometry, Residual Stress, thermo-mechanical analysis}
  • Himayat Ullah, Baseer Ullah *, Abdul Rauf, Riaz Muhammad
    Shot peening is one of the surface treatment processes usually used for the improvement of fatigue strength of metallic parts by inducing residual stress field in them. The evaluation of shot peening parameters experimentally is not only very complex but costly as well. An attractive alternative is the explicit dynamics finite element (FE) analysis having the capability of accurately envisaging the shot peening process parameters using a suitable material’s constitutive model and numerical technique. In this study, ANSYS/LS-DYNA software was used to simulate the impact of steel shots of various sizes on 2618-T61 aluminium alloy plate described with strain rate dependent elasto-plastic material model. The impacts were carried out at various incident velocities. The effect of shot velocity and size on the induced compressive residual stress and plastic deformation were investigated. The results demonstrated that increasing the shot velocity and size yielded in an increase in plastic deformation of the aluminium target. However, as observed, the effect of shot velocity and size was small in magnitude on the target's subsurface compressive residual stress.
    Keywords: Surface treatment, Finite Element Analysis, Residual stress, Plastic deformation}
  • Soheil Sarabandi *, Hesam Soleimani, Saeed Mahmoudi
    Variations in loadings of rolling contact components lead to a change in contact forces between surfaces. These forces are the main cause of rolling contact damages such as fatigue. Residual stresses are a major issue in railway wheel structures and it is appropriate to reduce such stresses. The aim of this paper is to estimate residual stresses in railway wheel due to hub to rim and axle to hub fitting process. a nonlinear three-dimensional model of stress is applied for analyzing stress field during press fitting process. An elastic-plastic finite element model is developed to model variable thermal loading in railway wheel. Finally, results of three dimensional finite element analysis showed a good agreement to field observations.
    Keywords: Residual stress, thermal loading, press fitting process, Finite Element, railway wheel}
  • A.T. Ozdemir *
    Cold expansion is an effective technique of inducing favorable compressive residual stresses around fastener holes essentially vital for improving fatigue performances of aircrafts. The benefit is caused by the magnitude and distribution of the compressive stress field. Stress gradients are entirely contingent on type of the cold expansion, local geometry of the hole and characteristics of the metallic structure. During cyclic loading however, initial residual stresses do not remain stable. In the present work, specimens with 4% split-sleeve cold expanded and reamed holes were cycled at the fatigue limit for short periods. Recent method of Combined Step Drilling-Fourier Series Solution ‘ATÖzdemir Method’ was employed to appraise the continual redistributions of residual hoop stresses at the side of the hole subjected to cyclic load. Some results were compared with that of diffraction methods and Artificial Neural Network (ANN) modeling where, close similarities in stress distributions were confirmed. It is clear that during early fatigue, material nearby the hole is dynamically hardening; in response compressive residual stresses along the bore are gradually increasing till the onset of cracking. Short fatigue cracks mostly initiate from the mandrel entrance side, where subsequently residual hoop stresses begin to relax considerably.
    Keywords: Fastener holes, Cold expansion, Residual stress, Fatigue}
  • M. Keikhaie, M.R. Movahhedy, J. Akbari, H. Alemohammad
    In order to improve the performance of thin lm devices, it is necessary to characterize their mechanical, as well as electrical, properties. In this work, a model is developed for analysis of the mechanical and electrical properties and the prediction of residual stresses in thin lms of silver nanoparticles deposited on silicon substrates. The model is based on inter-particle di usion modeling and nite element analysis. Through simulation of the sintering process, it is shown how the geometry, density, and electrical resistance of the thin lm layers are changed by sintering conditions. The model is also used to approximate the values of Young''s modulus and the generated residual stresses in the thin lm in the absence and presence of cracks in the lm. The results are validated through comparing them with available experimental data.
    Keywords: Thin lm, Silver nanoparticles, Nanoscale sintering, Residual stress}
  • E. Pooladi|Kh. Farhangdoost
    Cold working a hole decreases tendency of fatigue crack near the hole to initiate or growth. It is due to creation some compressive tangential residual stresses around the hole. In this paper strains recorded by strain gages mounted around the hole during cold working process has been introduced as a feature for residual stress field. Finite element modeling has been used for verifying the experimental results, which showed a good agreement. Also fatigue test has been performed on specimens with and without cold working which showed increasing of fatigue life.
    Keywords: Cold work, residual stress, strain, strain gage, fatigue}
  • رحمن سیفی، سیدمحسن موسوی ریگی، وحید آذری فر
    جوش ماهیچه ای به شکل اتصالات سپری و لب به لب در سازه های فولادی به صورت گسترده استفاده می شود. بنابراین تخمین میزان و نحوه توزیع تنش های پسماند در این اتصالات ضروری به نظر می رسد. در تحقیق حاضر توزیع تنش های پسماند مربوط به یک اتصال سپری مورد بررسی قرار گرفته است. انتهای اتصال به سه حالت مختلف ناقص، کامل با انحنا و بدون انحنا جوش کاری شده است. تحلیل عددی با روش اجزاء محدود و تحلیل تجربی با استفاده از روش سوراخ کاری مرکزی انجام شده است. نتایج عددی و تجربی مطابقت مطلوبی دارند. جوش کامل باعث کاهش تنش های پسماند طولی در ناحیه میانی اتصال و افزایش تنش های پسماند عرضی در ناحیه انتهایی می شود.
    کلید واژگان: اتصال سپری, جوش کامل و ناقص, تنش پسماند, سوراخ کاری مرکزی, روش المان محدود}
    Seifi *, Mousavi, Azari, Far
    Fillet weld is a common method of connecting various elements of the steel structures as in T- or butt joints. Thus, estimation of the amounts and distributions of residual stresses in these connections are important. Effects of complete and non-complete ends of T-joint, curvature of the ends, welding procedure, thickness ratio and welding speed on the distribution of the residual stresses were studied numerically and experimentally. The numerical analyses are done by using the finite element method. The center hole drilling method is used to measure of the residual stresses. A 3D model in Sysweld with thermo-mechanical analysis has been carried out to modeling the welding of stainless steel. There are good agreements between the results of two methods. Longitudinal residual stresses reduce in the midsection while transverse stresses increase in the end zone of the weld with complete end.
    Keywords: T, joint, Complete, Non, Complete Weld, Residual Stress, Central Hole Drilling Method, Finite Element Method}
نکته
  • نتایج بر اساس تاریخ انتشار مرتب شده‌اند.
  • کلیدواژه مورد نظر شما تنها در فیلد کلیدواژگان مقالات جستجو شده‌است. به منظور حذف نتایج غیر مرتبط، جستجو تنها در مقالات مجلاتی انجام شده که با مجله ماخذ هم موضوع هستند.
  • در صورتی که می‌خواهید جستجو را در همه موضوعات و با شرایط دیگر تکرار کنید به صفحه جستجوی پیشرفته مجلات مراجعه کنید.
درخواست پشتیبانی - گزارش اشکال