An assessment of geometry effects on plane stress fatigue crack closure using a modified strip-yield model

Using a modified strip-yield model, plane stress constant-amplitude fatigue crack growth simulations under conditions of small-scale yielding were performed for the edge-cracked strip in tension, the edge-cracked strip in bending, and the compact tension specimen with load ratios R = 0.5, 0.0, −1.0and−2.0. From these simulations, fatigue crack opening loads were predicted as a function of crack length. Geometry, loading type and crack length were observed to affect crack opening loads. The geometry-loading dependence was particularly evident for extended fatigue crack growth. Geometry-loading dependence was observed to increase for R < 0. Reductions in the crack opening loads following extended crack growth were also observed. These reductions were demonstrated to occur in the absence of large-scale plasticity in the remaining ligament. A normalized maximum applied stress intensity factor Kmax/σo√W, where σo and W represent the flow stress and specimen width respectively, was demonstrated to represent an approximate measure of small-scale yielding crack closure response similitude under plane stress conditions with R ⩾ 0. When crack opening loads were correlated in terms of this parameter, little geometry-loading dependence was observed.