Numerical Simulations of Subcritical Crack Growth by Stress Corrosion in An Elastic Solid

Abstract

A front-tracking finite element method is used to compute the evolution of a crack-like defect that propagates by stress driven corrosion in an isotropic, linear elastic solid. Depending on material properties, loading, and temperature, we observe three possible behaviors for the flaw: (i) gross blunting at the crack tip; (ii) stable, quasi-steady state notch-like growth; and (iii) unstable sharpening of the crack tip. The range of material parameters and loadings that cause each type of behavior is computed. Our results also confirm the existence of a threshold stress level (known as the fatigue limit) that leads to crack sharpening and ultimately to catastrophic fracture. Contrary to earlier predictions, however, our simulations show that the fatigue threshold is determined not only by the driving force for crack extension but also by the kinetics associated with the chemical reaction at the crack tip. Our results suggest that the fatigue threshold is likely to decrease as temperature is reduced. Finally, we have computed the steady state crack tip velocity as a function of applied load in the regime of steady state crack growth. Our predicted crack growth law is in good qualitative agreement with experiment, but uncertainties in material data make quantitative comparison difficult.