Simulation of electrohydraulic free forming of DP600 sheets using a modified Rousselier damage model

Abstract

Electrohydraulic forming (EHF) is a high-energy rate pulsed forming process in which the expansion of the plasma channel formed by the discharge of electrical energy between two electrodes immersed in water results in the high-velocity forming of the sheet material. This process is shown to have the capability of increasing the formability of sheet materials beyond conventional limits and being applicable to less ductile materials. In this work, DP600 sheet specimens were deformed in uniaxial tension, plane strain and biaxial tension using electrohydraulic free forming (EHFF). A modified Rousselier ductile damage model was then employed to predict the forming and damage behaviour of these specimens deformed along each strain path. This modified Rousselier model includes a modified Johnson-Cook hardening model as well as a void nucleation function and a void coalescence criterion. The limiting strains, the distribution of the scalar damage variable and the final damage morphology obtained from the numerical simulations were compared to the experimental results in order to evaluate the accuracy of the proposed micromechanical damage model. It is shown that predicted strains, damage accumulation and the final damage geometry of DP600 sheet specimens using the modified Rousselier model are in good agreement with experimental results as well as with those predicted by other phenomenological constitutive models.