Development of seat side frame by sheet forming of DP980 with die compensation

In recent years, ultra-high-strength steels (UHSS) are increasingly used in the automotive industry to manufacture lightweight car bodies with high crash performance. However, sheet metal forming of UHSS leads to a phenomenon called springback that involves the elastic recovery of the formed part and thereby results in shape errors in the final product. Therefore, accurate springback prediction is important, and an efficient die compensation method is necessary for the same. In this study, a seat side frame was developed by sheet forming of DP980 with die compensation. The Yld2000-2d yield function and the Yoshida-Uemori hardening model were implemented into the finite element analysis to consider the anisotropy, nonlinear kinematic hardening behavior, and changes in the elastic modulus of DP980. The material constants of the constitutive equations were determined using experimental results and a mathematical optimization technique. Springback was predicted by finite element analysis, and the results were applied for die compensation. Die compensation was accomplished by considering the differences between the springback analysis results and the target shape. The seat side frame was manufactured by cold stamping with the compensated die. The manufactured part was compared with the target shape to demonstrate the feasibility of die compensation in sheet forming for DP980.

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