Influence analysis of area reduction for necking in twice-stage cross wedge rolling

Abstract

A symmetric twice-stage cross wedge rolling (CWR) model was developed to analyze the generation mechanisms of necking by using rigid-plastic finite element method (FEM), and particular attention has been paid on the effect of area reduction on necking. After a brief summarize of necking criteria in single-stage CWR, the distribution coefficient of area reduction was presented to analyze the laws of necking in twice-stage CWR. The influences of area reduction on the field variables, including the effective strain, displacement, and damage, have been investigated to explain the laws of necking. With the necking behavior deteriorates, the displacement and damage increase. The traditional idea about distribution of area reduction is that the main deformation, which occurs in first stage, can effectively prevent necking in twice-stage CWR, but in this study, it has been found that the optimal state was achieved when the distribution coefficient of area reduction is close to 1. The production experiment on connecting rod preforming process was given to validate the simulation results. The results show that the law is desirable and gives a good guide for CWR die design.