Study of Effect of Varying Clearances on the Springback of Advanced High Strength Steel Sheets

Abstract

The springback of metal sheets shows a significant effect on the forming results of automotive structural parts. The components of new vehicles often have complex shapes, for which more precise forming procedures are required in order to achieve their desired geometries. Such springback occurrence is highly critical in the case of advanced high strength (AHS) steels. In this work, a V-shape stamping test was carried out for the AHS steel sheets grade 980 with an initial thickness of 1 mm. In parallel, the corresponding finite element (FE) simulations were conducted. Hereby, the Yoshida-Uemori (Y-U) kinematic hardening model was applied for describing the plastic deformation and elastic recovery of material. The parameters of the Y-U model were obtained from a tension-compression test and afterwards verified by using the 1-element model. The predicted bend angles of the formed samples fairly agreed with the experimentally measured results. Furthermore, the effect of defined die clearance at the corner of the formed sample on the magnitude of springback was numerically studied. It was found that the reduction of clearance of 10% led to obviously decreased shape deviations in the V-shape forming test.