2020 Volume 61 Issue 708 Pages 20-25
The strength differential (SD) effect, i.e., the difference in flow stress between tension and compression, of a high-strength cold-rolled steel sheet with a tensile strength of 980 MPa is measured using an in-plane tension-compression test apparatus. Biaxial tensile stress tests are also performed to measure the contours of plastic work of the test material. From the experimental results, a material model that can reproduce the SD effect is determined. Furthermore, this material model is implemented into the commercial FEM code LS-DYNA using a user-subroutine function. To validate the accuracy of this material model, curved hat panel forming without a blank holder is carried out. By comparing the experimental and forming simulation results, we validated the influence of the SD effect on the enhancement of the predictive accuracy of springback.