The effect of single overloads on fatigue-crack propagation in steels

Abstract The effect of single overloads on room temperature fatigue crack growth has been studied in two steels (FV 520B and Ducol W30B) of markedly different yield stresses. For a given overload, the amount of retardation was greater for lower baseline alternating stress intensity. In Ducol, retardation increased with decreasing specimen thickness. The results suggest that overload retardation is primarily due to residual compressive stresses generated in the crack -tip region, and is associated with crack-closure effects. An attempt has been made to rationalize the results in terms of a fatigue crack growing through overload plastic zones of different shapes and sizes associated with plane-stress and plane-strain deformation.