Abstract
The stress intensity concept is important in terms of crack extension as critical values of the stress intensity factors govern crack initiation. Therefore, the present work determines stress intensity factors for semielliptical shallow and deep surface cracks as a function of parametric angle, crack depth, and aspect ratio for tension and bending loads. The stress intensity factors are obtained from a threedimensional finite-element analysis of semielliptical surface cracks in finite plates subjected independently to tension and bending loads under elastic conditions. The obtained stress intensity factor is used to predict the crack growth under linear elastic conditions. Results show that the stress intensity factor varies along the crack front for shallow and deep cracks. At the deepest point in bending and tension the stress intensity factor increases as the ratio of the crack depth to the crack length at surface decreases. However, at the free surface the stress intensity factor becomes maximum when the crack depth equals crack length. A surface crack in tension loading is predicted to break the wall thickness with a relatively small amount of crack growth at surface. While in bending the crack breaks through with large amount of crack growth in the width direction.