On the ΔJ-integral to characterize elastic-plastic fatigue crack growth

Elastic-plastic fatigue crack growth is evaluated by J-integral range ΔJD based on a load-displacement hysteresis loop. However, physical meaning of ΔJD on a crack tip field is still controversial. In this study, finite element analyses were carried out on a four-point bending rectangular specimen with an edge crack under cyclic large deformation. The path-integral expression of J-integral range ΔJR was also computed, and the value of ΔJR was compared with the J-integral range ΔJD. Crack opening occurred at a slope change point in a load-displacement hysteresis loop. The values of ΔJD and ΔJR based on the slope change point were almost the same. The stress range Δσ distribution along the line ahead of a crack tip based on the slope change point was well characterized by ΔJR ( = ΔJD) as well as in the case of monotonic loading, and it was concluded that the value of ΔJD could be useful to describe elastic-plastic fatigue crack growth behavior.