STRESS INTENSITY FACTORS FOR LOW-ASPECT-RATIO SEMIELLIPTIC SURFACE CRACKS IN FINITE-THICKNESS PLATES SUBJECTED TO NONUNIFORM STRESSES

Three-dimensional finite element analyses have been conducted to calcu late the stress intensity factors for low aspect ratio semi-elliptic c racks. The stress intensity factors are presented for the deepest and surface points on semi-elliptic cracks with low aspect ratios of 0.05 and 0.1, and a/t values of 0.2, 0.4, 0.6 and 0.8. Uniform, linear, par abolic or cubic stress distributions were applied to the crack face. T he results for uniform and linear stress distributions were combined w ith corresponding results for higher aspect ratio surface cracks and e dge cracks to derive the weight function over the entire range of 0 le ss than or equal to a/c less than or equal to 1 and 0 less than or equ al to a/t less than or equal to 0.8. The weight function is then verif ied against finite element data for the parabolic or cubic stress dist ributions. Differences were less than 3% for the surface point and 5% for the deepest point.