A thermodynamic framework to predict ductile damage in thermoviscoplastic porous metals

Abstract

In this work, we develop and study a ductile damage model for thermoviscoplastic metallic materials taking into account void growth, thermal softening and heat conduction. The novel feature of the study is the extension of a Gurson-type dilatational plasticity yield surface, to include the combined effect of void shearing, thermoviscoplasticity and thermal conductivity. Several complex phenomena, such as plastically-induced void growth and nucleation, coalescence, shearing void growth, strain hardening, strain-rate dependence, heat generation by plastic work and diffusive thermal softening, are considered. Numerical examples considering 2D plates are presented to validate the proposed formulation. The influence of the strain rate on the material response is investigated in detail and the results are shown to be consistent with data reported in the scientific literature. The present formulation can reproduce shear banding coupled with damage for a range of strain rates, including the stress collapse due to porosity growth and temperature rise. The importance of the proposed model is also highlighted to other well known simplified models.