A modified strip-yield model for prediction of plasticity-induced closure in surface flaws

A slice synthesis methodology is developed and used to construct a modified strip-yield model for the semielliptical surface flaw, enabling prediction of plasticity-induced closure along the crack front and subsequent fatigue crack growth. A mathematical description of the model is presented. Slice synthesis methodologies have previously been limited to stress intensity factor and elastic crack displacement computation. Predictions of flaw shape evolution under cyclic loading are compared with experimental data for aluminium alloy specimens under uniform constant amplitude loading with R = 0.1, 0.3 and 0.6. Model predictions are shown to correlate well with experimental data. An empirical correlation of relative crack opening stress with applied R ratio from the literature is shown to underestimate the level of closure at the deepest point of penetration when compared with the model predictions.