A springback prediction of 1.5 GPa grade steel in roll forming process for automotive sill-side inner component

Abstract

Roll forming has been widely used to produce steel sheet with low formability such as Ultra High Strength Steel (UHSS). It allows the steel sheet to be formed through successive bending process into a desired shape which even cannot be formed by press brake forming. Although the process effectively improves the formability of UHSS, there still the remains accuracy issue such as springback, flair, bow and so on. Especially, springback of UHSS is one of the major challenges in roll forming process as much as press forming process. In this paper, the springback of 1.5 GPa grade steel in roll forming process was numerically investigated for automotive sill-side inner component. The material behavior was described by using the selected hardening models: isotropic hardening (Piecewise linear model), linear kinematic hardening (Prager model [6]), nonlinear kinematic hardening model (Yoshida-Uemori model [7]). A commercial software LS-DYNA was utilized for the analysis. Eighteen successive roll stages were modelled for the simulation. From the results, it was found that the springback prediction during roll forming process could be successfully achieved when the complicated material behaviors including Bauschinger effect, nonlinear transient hardening, and changeable unloading modulus are taken into account for the Finite Element (FE) simulation.