FINITE-ELEMENT ANALYSIS OF SPECIMEN GEOMETRY-EFFECTS ON FATIGUE-CRACK CLOSURE

Elastic-plastic finite element analysis is used to study fatigue crack closure at three different crack length to width ratios for three plane stress specimen geometries: center-cracked plate, single-edge-cracked plate (tension), and single-edge-cracked plate (bend). The maximum stress to flow stress ratio, S(max)/sigma0, which successfully describes closure results in many center-cracked plate configurations, does not correlate the effect of different geometries on the normalized opening stress, S(open)/S(max). Crack opening stresses for different geometries and crack lengths are successfully correlated by a normalized stress intensity parameter, K(max)/K0, where K0 = sigma0 square-root pia. The quality of the correlation is very high at small K(max)/K0, and gradually deteriorates as K(max)/K0 increases beyond the small-scale yielding regime.