Abstract: The large time step static implicit finite element method (FEM) for sheet metal forming simulation is presented to alleviate the convergence problem of the traditional implicit incremental FEM, and the simulation process of sheet metal forming is divided into bending deformation and tensile deformation. According to constraints of positions between the blank and mold, the shape of bending deformation which is called intermediate configuration is calculated. Meanwhile, a method based on pre-stress membrane element for constructing an intermediate configuration is also proposed in this paper. In this method, the contact states of the blank nodes are determined by the contact algorithm. The contact zone of blank is determined by the shape of mold, the non-contact zone is calculated with iterations for equilibrium equations by the pre-stress membrane element. The result shows that the proposed algorithm could obtain the appropriate intermediate configurations quickly and provide precise surface sliding constraint for tensile deformation.

Key words: sheet metal forming simulation; intermediate configuration; pre-stressed membrane element; finite element method