NEW IMPROVEMENTS IN THE MULTI-STEP INVERSE FEM FOR THE FAST FORMABILITY PREDICTION OF MULTI-STEP AUTOBODY STAMING PROCESS

In the paper, the multi-step inverse finite element method (FEM) has been introduced to improve the accuracy of simulation in sheet metal stamping. The multi-step inverse FEM can be used to obtain the strain/thickness distribution and shape of blank in the intermediate configurations. An efficient walk-through point location algorithm is used to deal with contact searching problem and restrain the movement of corresponding nodes of intermediate configurations. A constitutive equation based on pseudo deformation theory of plasticity is proposed in order to preserve the computational efficiency of inverse FEM. The presented algorithms are applied to a 2-step cylinder cup deep drawing product. The numerical results compared with explicit dynamic solver LS-DYNA3D confirm its validity in formability prediction of intermediate shapes and final workpiece.