Optimization of the blank holder stiffness in deep drawing processes by using FEA

When deep drawing the parts with complex geometry, changeable thickening can occur in the flange area. Extreme thickening of the part flange will cause pressure peaks at the contact surface between blank holder and part. This undesired occurrence during deep drawing will reduce process window and process robustness as well. In this paper, an approach to optimize the blank holder stiffness in deep drawing process is presented. The blank holder in this case consists from one plate which is supported with the appropriate elastic elements. Stiffness of the blank holder as well as pressure distribution during deep drawing was optimized by variation of the elasticity and order of the supporting elements. For this purpose simulation and experimental investigation for one car fender geometry were accomplished. Blank holder plate and corresponding supporting elements were meshed with solid elements and in the simulation considered as elastic bodies. Deep drawing was simulated systematically with different FE-Models for FEA with LS-Dyna. Simulation results were compared with measurements obtained by experiment, and they showed a good matching. Simulation and experimental results showed that with the optimized blank holder stiffness, the wrinkles of the second order as well as crack tendency in deep drawing process can be significantly reduced. Due to that, the process window can be enlarged.