Development of an Adaptive Directional Reduced Integration Technique and its Application to Rigid-Plastic Finite-Element Analysis of Heading and Backward Extrusion

In the analysis of metal forming processes, such as, heading and backward extrusion by the rigid-plastic finite-element method, a few numerical instabilities, e.g. element and shear locking and zero energy mode, may occur. The occurrence of these instabilities is investigated in both the backward extrusion and the heading process using various numerical integration schemes and with different element types. The results obtained are compared in terms of stability and efficiency of computation, by applying some existing integration techniques and also with a somewhat different numerical technique, proposed here, and called an adaptive directional reduced integration scheme (ADRI). Using this integration scheme and applying the rigid-plastic finite-element method, no zero energy mode was found to have been generated during solution of the above problems, even with the local severe deformations occurring at high reductions, in each of these cases. These and other experimental results are given and commented upon.