The migration kinetics of point defects near to a slowly moving brittle crack were studied under conditions of pure drift. In this approximation, it was assumed that the point-defect flow in the vicinity of a crack tip was dominated by elastic interactions between the stress field of the crack and a point defect. Concentration gradient effects were neglected. This pure-drift approach was shown to be useful for calculating the short-term diffusion kinetics of impurity-induced sub-critical crack growth. Previous applications had been based upon drift solutions for a stationary crack. The first-order drift diffusion equation, for a slowly moving crack at uniform velocity, was solved here. This yielded the flow lines of the point defects, and the impurity segregation rate, directly in terms of the crack growth rate. The flow-line patterns offered important insights into point-defect migration kinetics near to a steadily advancing crack. The calculation was entirely elastic, but the present drift model still had some relevance to the case of a plastic zone ahead of the crack tip.

The Stress-Driven Migration of Point Defects to a Slowly Moving Crack. P.Streitenberger: Philosophical Magazine, 2004, 84[23], 2455-70