Numerical modelling of roughness-induced crack closure

Fatigue crack growth (FCG) in metallic materials is primarily caused by cyclic plastic deformation. However, in the near-threshold regime, wedging phenomena such as roughness induced crack closure (RICC) become pertinent crack-tip shielding processes. The interaction between RICC and plasticity induced crack closure (PICC) is complex and has received limited attention, despite being important for FCG predictions. In this study, the Greenwood and Tripp (GT) rough contact model was incorporated into an FCG model to account for the effects of RICC. This framework considers the accumulated plastic strain at the crack tip as the main damage mechanism. The crack extension is performed using a node release strategy, where PICC is naturally described due to the residual plastic deformation in the crack flanks. The GT model accounts for the effects of the faceted crack surfaces, causing premature contact between the crack flanks. This approach allows for the qualitative reproduction of RICC effects. However, accurately predicting the impact of RICC on fatigue crack propagation through numerical modelling remains a significant challenge.