Effect of path-dependent plasticity on springback in reverse bending and its application to roll forming

Abstract

This study investigates springback behavior in martensitic advanced high-strength steels (AHSS) undergoing pure bending and reverse bending sequences. The comparison between a conventional isotropic hardening model and the Homogeneous Anisotropic Hardening (HAH20) model had been made, which accounts for non-isotropic hardening effects. Both models were calibrated using uniaxial tensile, cyclic, and loading-unloading tests. The results show that the HAH20 model predicts a higher initial springback compared to the isotropic model. However, reverse bending significantly reduces the overall springback for both models due to a minimized recovery moment. In scenarios with reverse bending, a specific strain exists where both models predict identical springback due to the secondary Bauschinger effect in tensile stress. This phenomenon is also observed in roll forming, a sequential bending process that incorporates reverse bending steps. Experimental findings from roll forming confirm a decrease in springback after the reverse bending stage. Furthermore, the study explores the impact of non-isotropic hardening on the part crashworthiness with the calibration of cross-loading effects. The Bauschinger effect and cross-loading contraction were found to reduce the maximum crash load by 6.2%.