Abstract: Equal Channel Angular Extrusion (ECAE) has become a very popular tool for studying the evolution of microstructure and properties under severe plastic deformation. It is believed that the stress-strain characteristics are uniform in a cross-section of the billet and this uniformity of the stress-strain distribution ensures the uniformity of microstructure and mechanical properties in ECAE processed billet. However, some experimental data such as the fracture of the extruded billet, which is initiated at the inner surface of the sample, has caused doubts about uniformity of stress-strain distribution. This non-uniformity has been proved recently by Finite Element Simulation.
In this paper the studies of the positive role of the applied back-pressure during ECAE are reviewed and the influence of a back-pressure on the uniformity of the stress-strain distribution, strain localisation, die corner filing, and the prevention of fracture is shown. The effect of back-pressure on grain refinement and improvement in mechanical properties is emphasized. The paper summarises our results from over seven years of work using a unique machine for ECAE with computer-controlled back-pressure and velocity of the backward punch.
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Authors: Shu Huang, Jian Zhong Zhou, Yi Bin Chen, C.D. Wang, X.D. Yang, Y.C. Dai
Abstract: An appropriate finite element analytical model for laser compound forming (LCF) was established with ABAQUS code, and then some key technical issues in the simulations were studied and solved. Numerical simulation of LCF for V-shape was carried out to study bending deformation, residual stress distribution and micro-profile of AISI-1008 steel plate. After the corresponding experiments of LCF, the bending deformation, forming precision as well as the variation of surface integrities were mainly measured and analyzed. The results indicated that anticipated shape of V-plate could be precisely formed, meanwhile distribution of surface residual stress and surface qualities on plate were under good control.
3857
Authors: Jun Zhan, Gui Min Chen, Xiao Fang Liu, Qing Jie Liu, Qian Zhang
Abstract: Gyroscope is the core of an inertia system and made by machining process. Machining process imports large residual stress. The residual stress will be released and induces large deformation of gyroscope frame. In this paper, the effects of residual stress on deformation of gyroscope frame were simulated by finite element method. Different stress distribution leads different deformation. Compressive stress can make sample long and tensile stress make sample short. The stress released in deformation process which reduced about 90%.
838
Abstract: When machining multi-frame complex components, more than 90% of the materials would be removed, resulting in severe distortion of the parts due to the weakened rigidity and the release of residual stress. This might also lead to stress concentration and damage of the parts. The effect of material removal from residually stressed billet is simulated using FEA software ANSYS, and the causations of distortion is analyzed. To verify the finite element simulation, a high speed milling test on aluminum alloy 7050T7351 is carried out. The results show that the simulation result is consistent with the experimental one. It included that the original residual stress in the blocks of aero-aluminum component is one of key factors to cause machining distortion.
143
Authors: Wei Shin Lin, Bean Yin Lee, Yuan Chuan Hsu, Jui Chang Lin
Abstract: In multi-wire flat rolling process, the error of the rolled wires in thickness was due to the roller deflection and the spring back of the rolled wire. In order to control the dimension accuracy, to know the quantity of thickness error precisely is very important. In this study, the DEFORM-3D finite element analysis software was used to simulate the multi-wire flat rolling process with the elastic-plastic deformation model, supposed the rollers as elastic body and the wires as elastic-plastic body through the rolling process. From the computer simulation results, it can be found that, the deflection of roller has the biggest effect on the dimension accuracy of wire. To control the deflection value of roller, besides roller material and the roller length, the choice of roller diameter is also very important.
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