Rigid–viscoplastic finite element analysis of the piercing process in the automatic simulation of multi-stage forging processes

In this paper, an application-oriented piercing simulation technique in automatic forging simulation by the rigid–viscoplastic finite element method is presented. In this approach, it is assumed that fracture in piercing takes place at the instant when the maximum accumulated damage around the shearing region reaches the critical damage value of the material and that separation is made along the line connecting the two die edges. A method of obtaining the critical damage value by comparing the tensile test result with that of the analysis is given, with emphasis on the effect of the strain hardening exponent on the critical damage value. The approach presented is verified by a test piercing process with a medium-carbon steel and is applied successfully to the automatic simulation of a sequence of six-stage compound forging processes.