| The primary theory of the plastic forming was presented at first: the constitution of the elastic-plastic material modal, thermal conduction analysis, the thermal stress analysis, the coupled thermal-mechanical analysis and the remesh method and so on were presented in detail.the process of the cold extrusion was simulated by the coupled thermal-mechanical analysis using elastic-plastic material modal, so the stress contour and thermal contour of the workpiece and the mold were gained and did also the equivalent plastic strain contour of the workpiece and the extrusion force. These results make good agreement with the reality.The influence of the material modal ,the frictional coefficient, and the element size to the simulation, the release of the elastic deformation to the size of the workpiece were analyzed and compared ,the residual stress in the modal and the volume lost due to the remesh were also be studied.The distribution of the stress in the mold was analyzed and the reason of the stress concentration in the mold was find out. The structure of the mold was modified; the simulation of the process wad conducted again. The analysis result complies with the reality. The service life of the mold improved significantly.The fatigue theory was introduced in detail and the strain fatigue method was presented in detail especially. The linear elastic finite element modal was built according to the stress distribution,the analysis of the stress result was conducted with the fatigue analysis software and the analysis was conducted with the load history in the dangerous area was applied,the service life was predicted by the FEA,these results make good agreement with the real life of the mold.The shortcoming of the analysis was presented, the solution of the plastic foming simulation and fatigue problem was further studied. The summarization of these questions which lie in the analysis was made, the advancing trend of the problem solution was described in the end.
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