On crack arrestability by a circular hole based on computational crack path prediction

Abstract

In stiffened plate structures, cracks are often formed at the intersections of the stiffeners, where severe local stress concentrations and welding residual stresses exist. Since the local stress distribution is rather complicated along the crack trajectory, crack curving is one of the essential features of this type of problems. Cracks initiated and growing in the stiffened plate structures are difficult being detected by small leakage of fluid, and the crack arrest design concept which is different from the leak before break (LBB) concept could be introduced in preventing the catastrophic failure of such structures.A computational scheme has been developed for the crack path prediction, which is performed by the step-by-step stress analysis ahead of the crack tip and the prediction of a curved increment of the crack growth by the use of analytically expressed asymptotic crack path in the neighbourhood of the crack tip. As a fracture criterion we use the locally symmetric condition which requires the Mode II stress intensity factor vanishing along the crack path.In this paper, holes are considered as crack arresters and their capability is examined by computational crack path prediction and experiments. We consider the case where a crack is approaching a circular hole. When the crack tip approaches in the neighbourhood of the hole, where the shortest distance between the crack tip and edge of the hole is within the radius of the hole, they attract with each other and the crack penetrates into the circular hole resulting arrest at the hole.