Hydro-forming is a fabrication process that uses a fluid medium to form a piece by using high internal pressure. In tube hydro-forming, a tubular blank is placed between two dies, sealed and pressurized water injected, deforming the tube walls in the cavity form of the dies. Exist Several typical hydro-forming processes such as T- shapes, cross-shapes and Y- shapes. Successful hydro-forming depends on selection of proper tubular blank, sound preform shape and internal pressure. In this paper, 3D model of hydro-forming process of T-shape tube has been simulated by finite element method. Two damage model, coupled with von Mises plastic criterion, have been applied to predict where and when onset of ductile and MSFLD rupture occur in the process. All studies presented in this paper have been carried out on aluminium alloy EN AW-7108 T6. تفاصيل المقالة

In this paper the nonlinear bending analysis of thick functionally graded plates subjected to mechanical loading is studied. The formulation is derived based on the third-order shear deformation plate theory and Von Kármán type non-linearity. Young’s modulus is assumed to vary according to a power law distribution in terms of the volume fractions of the constituents. The principle of virtual work is used to obtain the weak form of the governing differential equations. The most important advantage of employed numerical solution in this work is that the whole plate is considered as one element and the components of displacement field are interpolated over the entire domain, then a hierarchical finite-element scheme is developed. The validity and the accuracy of the method are verified by comparisons made with other solutions. In addition; the effect of numbers of interpolation functions on the accuracy of results is studied. It is concluded that accurate results are obtained even by few numbers of interpolation functions. تفاصيل المقالة

All the producing and assembling processes exert residual stress on the pieces that may lead to structural failure. Therefore, calculating the residual stress in such structures has been common in recent years. In this article, distribution of temperature and residual stress resulting from arc welding in three-pass butt joint in P91 austenitic stainless steel pipes is calculated and estimated using the finite element method and experimental data. Simulating the welding process has been carried out three- dimensionally using Abaqus software. Distribution of the arc thermal flux has been identified based on the Goldak two-elliptical model using DFLUX subprogram in Abaqus software. The numerical method has been employed by doing thermoelastoplastic analysis and the technique of birth and death of the elements to model the welding passes and the melted elements. Then, using central hole drilling method, residual stress gradient of the thickness at distance 3mm from the welding line on the pipe is measured. Finally, the maximum percentage of error, through the results obtained from experimental measurements and finite element method, was reported 27% which is scientifically reasonable. The results show that the residual environmental stress in the internal surface of the pipe from the welding central line to 8.7mm varies with the gradient of 610MPa from 296MPa to -314MPa. Such a drastic stress distribution leads to genesising some cracks on the welded pipes. تفاصيل المقالة