Damage-induced changes in elastic stiffness of DP800 sheets at large strains

Damage is associated with the performance of formed components. Quantifying its influence is challenging due to interactions with other product properties such as strain hardening, texture and residual stresses. To isolate the effect of damage on the elastic stiffness after large plastic strain, a modified extrusion process for DP800 sheets is employed. The sheet specimens are positioned between two half-cylindrical billets and cold-extruded with varying superposed counter pressures to control damage evolution. Subsequently, tensile tests on specimens extracted from the extruded sheets are conducted to quantify the effect of ductile damage on the apparent elastic stiffness. The experiments indicate that damage in the form of voids affects the apparent elastic stiffness, however, this effect is relatively small compared to the influence of plasticity-related effects on the apparent elastic stiffness.