PREDICTION OF DUCTILE FAILURE IN METAL STRUCTURES BASED ON THERMODYNAMICS OF IRREVERSIBLE PROCESS

摘要

The objective of the work presented in this paper is to generate a thermodynamically consistent coupled thermo-elastic-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 ω_(ij). This allows for definition of two scalars that are ω = ω_(kk)/3 (the volume damage) and α = (ω_(ij)′ω_(ij)′)~(1/2) (a norm of the damage tensor deviator ω_(ij)′ = ω_(ij) — ωδ_(ij)). 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 micro-pores 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. 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. Performance of the model is illustrated by few numerical examples.