A scheme for volume loss recovery and incremental volume control in non-steady state metal forming analyses by rigid-plastic finite element method

摘要

One of the major advantages of rigid-plastic FEM is that it can use a relatively large increment and thus the computation efficiency is high. But, when a large time increment is used, a large volume change is induced and thus the volume constancy is disturbed. This causes a serious problem in the prediction of the proper filling of metal in a die cavity and produces some defects in the process design, though it is the main purpose of the numerical simulation. Therefore it is strongly desired to suppress such volume changes to be the allowable limit. In this paper, we propose a simple computational scheme recovering the volume change. It includes both the volume change accumulated over all the incremental calculation steps and that caused during a single step. Simple cylindrical billets in upsetting and extrusion are considered. From these it is confirmed that the volume change is significantly reduced and the accuracy of the calculated processing load is also improved. It should be noted that the proposed scheme is quite simple and can be easily implemented into any existing code.