A study of combined roughness and plasticity induced fatigue crack closure for long cracks using a modified strip-yield model

Combined roughness- and plasticity-induced crack closure for long cracks is studied using a Design and Analysis of Computer Experiments approach. A newly developed modified strip-yield model which has been adapted to incorporate the mode I effects of roughness induced crack closure is used for the study. The effects of maximum stress, load ratio, roughness asperity angle, and roughness periodicity are quantified. In addition, conditions affecting the benefit of roughness-induced crack closure are investigated.

► We study roughness- and plasticity-induced crack closure via a geometrical model.
► We study maximum stress, load ratio, roughness period, and asperity angle.
► Closure oscillated about an average value due to the sawtooth crack face.
► The closure is controlled by the asperity angle, load ratio, and their interaction.
► While closure is enhanced in all cases, negative load ratios decrease the benefit.