Bauschinger effect calibration by the different types of loading/reverse loading tests for springback prediction in sheet metal forming

Abstract

This study deals with the calibration of Bauschinger effect on DP980 and TRIP1180 sheet metals with three cyclic material tests: tension/compression, shear/reverse shear, and bending/reverse bending. An in-plane simple shear jig, in which the grip bolts are evenly positioned surrounding a specimen to prevent the specimen from slipping, is developed for shear/reverse shear test. A new concept of electronic bending/reverse bending tester, which operates on brushless DC motor and can be speed-controlled, is designed for bending/reverse bending tests. In the newly devised bending/reverse bending test, the gaps between specimen and grip make the specimen deform like pure bending with only four points touching. The material parameters of Yoshida-Uemori (YU) model are determined from tension/compression, shear/reverse shear, and bending/reverse bending tests. The calibrated material properties for the Bauschinger effect are verified with the application for U-draw bending test. The springback prediction results based on the three loading/reverse loading tests are comparatively evaluated with various blank holding forces.