Three-dimensional effects on fatigue crack closure under fully-reversed loading

For extension of fatigue cracks at engineering length-scales, the increase in crack opening loads (Kop) caused by plasticity-induced closure plays a key role in estimates of growth rates in structural metals. Under conditions of small-scale yielding, our prior work reveals the existence of a similarity scaling parameter, K¯=Kmax/σ0B, that scales the effects of differing peak load (Kmax), specimen thickness (B), and material yield stress (σ0) on Kop/Kmax across varying materials and loading levels. This work explores the applicability of the scaling parameter to specimens under fully-reversed (i.e. R = −1) cyclic fatigue loading. Numerical results again show that the magnitude of Kop/Kmax at each location along the crack front remains unchanged when Kmax, thickness, and material yield stress all vary to maintain a fixed value of K¯.