Effect of tension-compression testing strategy on kinematic model calibration and springback simulation of advanced high strength steels

Abstract

Various studies show that application of kinematic hardening models significantly improves the accuracy of springback simulation in sheet metal forming. The springback simulation using kinematic hardening models, e.g., the Yoshida-Uemori (YU) model, is highly dependent on the testing strategy and the calibration of model parameters. In this study, the effect of tension-compression (T-C) testing strategy on calibration of YU model parameters and springback simulation of advanced high strength steels was investigated. A single-element model with T-C conditions was built in LS-OPT to determine YU model parameters on the basis of T-C tests. U-bending tests of two 980 MPa grade steels were performed to evaluate the springback prediction. Results indicate that T-C strategies, including tension-compression sequence and prestrain level show little effect on the calibrated YU model parameters as well as springback simulation of a dual phase steel DP980. However, for a TRIP-assisted high strength steel QP980, T-C strategy significantly affects both the YU model parameters and springback simulation, which is related to the complex loading-path-dependent retained austenite transformation in the QP980. A compromise strategy of T-C testing is proposed to calibrate the YU model parameters of the steel QP980, which are capable to accurately simulate its springback in U-bending.