Material characterisation for reliable and efficient springback prediction in sheet metal forming

In this paper, a novel experimental-numerical methodology for an accurate prediction of springback after sheet forming is presented. An advanced phenomenological material model is implemented in the FE-code ABAQUS. It includes the Bauschinger effect, the apparent reduction of the elasticity modulus at load reversal after plastic deformation, the strain rate dependence and the elastic-plastic anisotropy and its evolution during the forming process. The required material parameters are determined from stress-strain curves measured in tension-compression tests. These tests are carried out with a special test rig designed to avoid buckling of the specimens during compression. The benefits of this procedure for springback prediction are demonstrated. Additionally, parameters for the phenomenological models are determined from texture simulations.