Abstract: In order to find a method to reveal the deforming rules of the viscoplastic extrusion forming such as the isothermal extrusion and superplastic extrusion etc., the combined extrusion of industrial pure lead which has viscoplastic behaviour at room temperature has been simulated by viscoplastic finite element method. The calculating results bring to light the deforming rules such as the change of neutral layer position, the distribution of velocity field and the cause of folding defect etc. On the basic of calculating results, It was found that the greatest deforming zone of viscoplastic combined extrusion is at the corner of punch bottom and the gradient of deformation distribution decreases with the deformation. The improvement of lubrication condition and the raising of deforvelocity can ameliorate the deforming homogeneity. Some calculation problems such as ming the generation of initial velocity field, the treatment of folding and mesh rezoning had been treated effectively.

Key words: Deforming rule, Finite element analysis, Viscoplastic extrusion