THE EFFECT OF BLANKHOLDING FORCE TRAJECTORY ON SPRINGBACK PREDICTION IN DUAL PHASE 590 STEEL

Advanced high strength steel (AHSS) alloys are being introduced in the manufacture of automotive sheet metal products due to their desirable combination of high strength, good ductility and high stiffness. These properties allow for weight reduction while maintaining the structural characteristics of the sheet panel compared with traditionally used steels. Regardless of the type of material used for the manufacture of automotive sheet products, springback is an issue that is of great importance. Accordingly, this paper presents the findings of study on the effect of blankholding force (BHF) trajectory on springback for Dual Phase (DP) 590 steel. In the study, the split ring test was used to assess residual stress in the walls of deep-drawn cylindrical cups as a function of the applied BHF. Additionally, finite element analysis of the deep drawing process and the split ring test are used to predict the residual stress in the formed cup. The paper shows that best springback (minimum residual stress) can be achieved with a pulsating BHF during the cup forming process, and that numerical models of the split ring can be used at the process design stage to assess and identify means to control springback.