Finite element simulation of cracking from sulfur-induced dynamic embrittlement in a polycrystalline copper specimen
Résumé
The occurrence of dynamic embrittlement during tensile tests of copper alloys leads to intergranular brittle fracture. This type of failure is provoked by stress-assisted diffusion of impurities along the grain boundaries (Fig. 1). The effect of dynamic embrittlement is amplified by environmental and loading conditions, such as temperature increase and/or strain rate decrease. For simulation of the cracking process, a 3D synthetic microstructure, comprising a number of grains and grain boundaries, is considered (Fig. 2). Crystal plasticity is used to model the grain interior behaviour, while a cohesive zone model is applied to describe grain boundary decohesion. As regards to bulk diffusion of sulfur, driven by the gradient of hydrostatic stress, it is treated within Abaqus by solving the coupled transport equations. In addition, an impurity-dependent traction-separation law is considered in order to account for the negative effect of impurity coverage on the cohesive energy of grain boundaries. Based on this coupled micromechanical-diffusion-damage modeling, numerical simulations are conducted to analyze the conditions of diffusion-induced intergranular cracking.