On the stress intensity factors associated with cracks interacting with an interface between two elastic media

Closed form expressions are obtained for the stresses at a crack tip when a crack is approaching a welded boundary (or a free surface) and when it has just passed through the interface. The solutions which are obtained in terms of a small parameter, the distance from or through the interface, are given in explicit form for the mode 3 situation and for some mode 1 and 2 cases. The importance of the change of stress singularity when the crack meets the interface is demonstrated.