Simulation of multi-step sheet metal forming processes by a static explicit FEM code

Two topics related to the FEM simulation of multi-step stamping processes are discussed. They are: (1) the difficulty in simulating the springback and trimming operations, and (2) the way to select a most appropriate element. The basic nature of problems with the springback simulation can be attributed to a 'drift' from the equilibrium path due to the static explicit formulation of the ITAS3D FEM code used for the simulation. A strategy on how to minimize the 'drift' phenomenon is presented here. The second problem of the most suitable element, shell or solid, for simulation of multi-step stamping processes is of general character and can be addressed to all users of explicit and implicit FEM codes. We show that for some of the stamping processes, a solid element is superior to a shell. Finally, the entire simulation of multi-step forming processes of a car wheel disk is presented and compared with experiment data. (C) 1998 Elsevier Science S.A. All rights reserved.