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, -1.0 and -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 K-max/sigma(o) root W, where sigma(o) 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 greater than or equal to 0. When crack opening loads were correlated in terms of this parameter, little geometry-loading dependence was observed. Copyright (C) 1996 Elsevier Science Limited