Calibration of the bauschinger effect for springback prediction in sheet metal forming

Abstract

Material parameters related to the Bauschinger effect are determined by loading/reverse loading tests. This study deals with the calibration of the Bauschinger effect on a 1.5GPa grade steel with three cyclic material tests: tension/compression test, shear/reverse shear test, and bending/reverse bending test. A rigid shear jig, in which the grip bolts are evenly positioned surrounding a specimen to prevent the specimen from slipping, and an electronic bending/reverse bending tester, which operates on a brushless DC motor and can be speed-controlled, are designed in order to conduct in-plane simple shear/reverse shear and cyclic pure bending tests. In the bending/reverse bending test, the gaps between a specimen and grips could make the specimen deform like pure bending with only four points touching. This work also performs one element simulation for the parameter calibration of tension/compression and shear/reverse shear tests and finite element simulation for that of bending/reverse bending test whose experimental condition could be sensitive to friction, stretch, and compression. The parameters identified from the different cyclic tests generate different hardening curves, which are calibrated by the Yoshida-Uemori model. The results of the material characterization suggest that different strain paths could show different stress-strain behaviors.