Fatigue crack propagation behaviour of a Ni−Cr−Mo steel due to rest period and overload

Abstract

The aim of this study is to investigate the effects of an intermittent rest period at 300°C, overload in tension, and the combination of an overload and a subsequent rest period on fatigue crack growth in AISI 4340 steel. The intermittent rest period was found to stop fatigue crack growth completely near threshold level of ΔK. The alleviation effect of a rest period on crack growth was more distinct at the lower level of ΔK. In overload, the greater overload ratio (OLR=3) caused more alleviated effect on crack growth rate. The reduced stress intensity factor by crack branching and enhanced roughness of crack surface are proposed to contribute to the retardation and arrest of fatigue crack growth. The most distinct retardation of fatigue crack growth was found after the combined treatment of a overload and a subsequent rest period.