Understanding robustness of springback in high strength steels

The rapid uptake of high strength steels (HSS) to help reduce vehicle weight has caused some concerns for increased springback in many automotive stamping plants. The variation in springback, caused by subtle changes in the forming process and material conditions, is even more complex and has received little attention. This paper investigates the effect of typical control parameters, such as blank holder pressure, friction coefficient, punch radii and die radii, on the springback robustness when forming a semi-cylindrical channel from Dual Phase steel through finite element method. Results show that the springback response is heavily influenced by two factors; the process response window, governed by the process conditions, and the plastic modulus of the materials flow curve. In particular, the characteristics of the materialʹs flow curve significantly influence the robustness of the system. This study highlights the reason for increased variability in high strength steels such as TRIP steels.