Damage Evolution in Nakajima Tests of DP800 Dual Phase Steel

Abstract

In order to extend the understanding of damage evolution in sheet metal forming, standardized Nakajima tests are carried out on a DP800 dual phase steel. Sample geometries for characteristic stress-strain states are drawn in incrementing stages and their damage states are analyzed using light and scanning electron microscopy as well as micro hardness measurements. Numerically analyzed load paths are correlated with the respective damage states to allow prediction of damage evolution in deep drawing processes. The influence of anisotropy is investigated by testing samples cut at various angles to the rolling direction of the sheet material. The result of the conducted research is the understanding of interactions between load paths and damage evolution in sheet forming. These results will later be used to optimize load paths in a deep drawing process, taking into account Lode parameter and stress triaxiality to produce damage controlled parts.