Analysis and experimental studies of internal voids in multi-wedge cross wedge rolling stepped shaft

Abstract

In this study, a rigid-plastic finite element method (FEM) simulation model for a multi-wedge cross wedge rolling (MCWR) was developed to analyze the generation mechanisms of internal defects. Two feature parts in MCWR, rod area and store area, were defined to analyze the internal defects mechanisms. The difference of stress states between the rod and store areas was pointed out and an insight into generation mechanism was concluded. Based on simulation, the influence of mold parameters was discussed and an optimized parameter group was achieved. The results indicate that the internal voids in the store and rod areas were extended from microcracks produced by shear stress cycle, and then develop to cracks due to the overlarge first principle tension stress caused by metal backflow. In a certain range, a smaller forming angle and a reasonable area reduction is good for avoid center voids in store area. Subsequently, the industrial test manifested the feasibility of study results.