Simulation and comparison of several crack closure assessment methodologies using three-dimensional finite element analysis

Plasticity induced fatigue crack closure simulations were performed using a three-dimensional finite element analysis of a single edge-cracked tension specimen under constant amplitude loading and load ratio R = 0. Four different methodologies were considered to assess fatigue crack closure: (a) a node displacement method monitoring the first and second nodes behind the crack tip, (b) a contact stress method, (c) the traditional compliance offset method, and (d) the adjusted compliance ratio (ACR) technique. The evolution of crack driving force was compared in terms of U=ΔKeff/ΔKU=ΔKeff/ΔK, where ΔKeff and ΔK are the effective and applied stress intensity factor ranges, respectively. The node displacement method using the first node behind the crack tip and the contact stress method produced the lowest levels of U. Larger U levels were obtained from the node displacement method using the second node behind the crack tip followed by those from the compliance offset technique. The ACR methodology provided the highest U values for the range of applied loading considered in this study.