Interactions fissure-dislocations en corrosion sous contrainte. Simulation numérique

Numerical simulations of the stress corrosion crack tip-dislocations interactions

Centre SMS, URA CNRS 1884, Ecole des Mines de Saint-Etienne

Abstract

This paper deals with numerical simulations of the corrosion enhanced plasticity model proposed to describe stress corrosion cracking in FCC materials. This model is based on a softening effect at the crack tip due to corrosion. It can explain how stress corrosion cracking can be discontinuous at the scale of the micron, involving {111} planes. Numerical simulations are of great interest to estimate the parameters of the model at this scale and predict the fracture rate. They are based on the movement of dislocations at a crack tip, and introduce the effects of hydrogen and vacancies produced by the electrochemical reactions. The mathematical and mechanical tools used in the calculations are presented, based on the elastic interactions between a crack and dislocations. The presence of dislocations shielding the crack is taken into account in the propagation criterion. The presence of the free surfaces of the crack is taken into account to calculate the dislocation stress field and the force applied on each defect. The first results show the formation of a pile-up, moving with the diffusion front, and the effects of hydrogen on the dislocation interactions.