Abstract
Compressive residual stress is qualitatively known to have a strong effect of deceleration of crack propagation rate and hence improvement of fatigue strength. In fretting fatigue a fatigue crack generally initiates in the very early stage of fatigue life, which is therefore mainly dominated by the fatigue crack propagation life. This paper investigated the quantitative effects of residual stress on fretting fatigue crack propagation and fretting fatigue strength using aluminum alloy specimens with and without WPC treatment, which can induce residual stress in the specimen surface layer. It was found that the compressive residual stress in the surface layer decelerates the crack propagation rate, while it has no obvious effect on the crack initiation. A simple quantitative method for evaluating the effect of residual stress on crack propagation has been proposed. It was found that both the effects of residual stress on fretting fatigue crack propagation and fatigue life could be quantitatively evaluated according to the proposed method. Moreover, based on the method proposed, the estimation of the increase of fretting fatigue strength due to residual stress agrees well with the experimental results.
