Simulation of the sheet metal extrusion process by the enhanced assumed strain finite element method

The extrusion process of a steel plate has been simulated by the geometrica lly non-linear enhanced assumed strain finite element method. An enhanced s train field has been added to the conventional axisymmetric four nodes elem ent to avoid volumetric locking in the plastic range. In order to achieve v olume constraint closely, the enhanced deformation gradient has been constr ucted in the rate form. The standard Newton-Raphson iteration method togeth er with the corresponding consistent tangent operator have been used to sol ve the incremental equilibrium equations. The local integration of the fini te strain J(2)-flow theory has been carried out by the elastic predictor an d plastic corrector return mapping algorithm. The material constitutive equ ation used takes the effects of strain hardening and damage softening into account. In the solution process, a line search technique has been used to ensure computational convergence. The computed profile of the protruded wor kpiece has been found to be in good agreement with the actual profile. The results also show that damage softening has a remarkable influence on the l imit strain of the extrusion process. It may be concluded that the enhanced assumed strain finite element method can be used to analyze sheet metal ex trusion. (C) 1999 Elsevier Science S.A. All rights reserved.