Unveiling contribution of overload-induced residual stress to fatigue retardation pertinent to crack closure and stress intensity

Abstract

Although residual stress (RS) and crack closure (CC) are generally accepted as predominant factors affecting post-overload fatigue crack growth (FCG), they cannot explain many peculiarities of FCG variation. Understanding overload mechanisms is essential to life prediction in variable amplitude fatigue load. In this study, the RS contribution behind and ahead of a crack tip and its relation to CC and stress intensity of fatigue cycling is clarified through combination of different stress ratios, heat treatment, overloads, and removals of crack wake and crack-tip plastic zone. Results indicate that overload-induced RS contribution is a single decisive factor for post-overload FCG rate without initial acceleration, and exhibits CC dependence behind crack tip and applied stress-intensity dependence ahead of crack tip.