The numerical investigation of the material behavior of high strength sheet materials in incremental forming

Springback is an inevitable phenomenon in sheet metal forming and has been found to reduce with an increasing number of forming steps. In this study the effect of incremental forming on springback is analyzed for DP780 steel. The cyclic hardening characteristics of the DP780 steel are determined by fitting the experimental moment curvature data of a cyclic pure bending test using Abaqus Standard. The change in elastic modulus with pre-strain is also considered in the material model. Using the developed material model a V- die forming process is numerically analyzed for single and multiple-step forming, and the effect on springback determined. The numerical results show that there is a reduction in springback with an increasing number of forming steps, and that this may be due to the plastic strain accumulated in the blank during the sequential loading steps in the bending region. A very good agreement has been achieved between the simulation and the experimental results. The present study seems to offer an effective approach to increase the accuracy of the springback prediction and provide a greater insight into the nature of the springback in the incremental forming process.