Fracture behavior investigation on an arbitrarily oriented sub-interface Zener-Stroh crack

The general solution of an arbitrarily oriented sub-interface Zener-Stroh crack is derived with the aid of distributed dislocation methods. The crack problem is formulated as a set of singular integral equations and solved numerically so that the stress intensity factor can be evaluated for any orientation angle. To make the facture analysis more accurate, the plastic zone size (PZS) and the crack tip opening displacement (CTOD) are examined by the generalized Irwin model. The plastic zone area is assumed to follow the von Mises yielding criterion and can be related to the stress intensity factors at the crack tips. Numerical examples are given to demonstrate the influence of various parameters, such as material properties, crack-interface distance and loading ratios, on the normalized PZS and CTOD for vertical and parallel crack cases. It is found that the Zener-Stroh crack becomes easier to propagate when it is located in the "softer" phase of the bi-material structure and parallel to the material interface. If the crack is perpendicular to the interface, it would be much easier for the crack to propagate into the "softer" side of the structure.