Prediction of Ductile Failure in Metal Structures Based on Thermodynamics of Irreversible Process

Abstract

The objective of the work presented in this paper is to generate a thermodynamically consistent coupled thermoelastic-plastic damage model of solid media at a macroscopic level. The model is based on the thermodynamics of irreversible processes and the assumption that damage within a continuum can be represented as a damage tensor ωij [1], [4]. This allows for definition of two scalars that are ω = ωkk / 3 (the volume damage) [2], [3] and α = ωij′ωij′ (a norm of the damage tensor deviator ωij′ = ωij − ωδij [4]. The parameter ω describes the accumulation of micro-pore type damage (which may disappear under compression) and the parameter α describes the shear related damage. The parameter ω may be considered as a volume content of micropores in the material. In the damage-free material we have ω = α = 0; if damage is accumulated, ω and α increase in such a manner that they remain less than one. The prediction of void growth is based on work by Tuler-Butcher [4]. This damage evolution is then coupled to a rate and temperature dependent deviatoric plasticity model. The criterion for failure is the entropy criterion based on a critical value of a specific dissipation function [4]. Performance of the model is illustrated by few numerical examples.