Measurement of the Bauschinger behavior of sheet metals by three-point bending springback test with pre-strained strips

In this paper, a novel approach is proposed to measure the Bauschinger effect, transient behavior and permanent softening of metallic sheet subjected to reverse loading. The hardening parameters related to the Bauschinger effect, transient behavior and permanent softening are optimized from the springback profiles of three-point bending tests with pre-strained sheets. Taking the dual phase steel sheet DP780 as an example, its Bauschinger effect, transient behavior and permanent softening determined from the new approach are compared with those of the cyclic simple shear method. Finite element simulations are also performed for three-point bending and U-draw/bending of base (as-received) and pre-strained DP780 steel sheets to validate the suggested approach. The results show that the aforementioned hardening behavior determined from the new approach shows good agreements with those of cyclic simple shear tests. Moreover, reasonable springback predictions for three-point bending and U-draw/bending tests are obtained as well. In particular, the proposed approach is quite suitable for the industrial applications because only uni-axial tension and three-point bending tests are required.