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

Elastic-plastic fatigue crack growth is evaluated by J-integral range Delta J(D) based on a load displacement hysteresis loop. However, physical meaning of Delta J(D) 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 Delta J(R) was also computed, and the value of Delta J(R) was compared with the J-integral range Delta J(D). Crack opening occurred at a slope change point in a load-displacement hysteresis loop. The values of Delta I-D and AJR based on the slope change point were almost the same. The stress range Delta sigma distribution along the line ahead of a crack tip based on the slope change point was well characterized by Delta J(R) ( = Delta J(D)) as well as in the case of monotonic loading, and it was concluded that the value of Delta I-D could be useful to describe elastic-plastic fatigue crack growth behavior. (C) 2017 Published by Elsevier Ltd.