DETERMINATION OF THE ASYMPTOTIC CRACK-TIP FIELDS FOR A CRACK PERPENDICULAR TO AN INTERFACE BETWEEN ELASTIC-PLASTIC MATERIALS

The singular behavior near a crack tip at the interface between two power-law hardening materials with the crack perpendicular to the interface is studied for both Mode I and Mode II loading under either plane strain or plane stress conditions. The mathematical model developed can be expressed as a fourth order ordinary differential equation with homogeneous boundary condition. A shooting method is applied to obtain the eigenvalues and to solve the differential equation with homogeneous boundary conditions. When both materials have the same hardening exponent, N, another material parameter, beta, representing the relative resistance of two materials to plastic deformation, is introduced to reflect the joint effect of the two materials on the singularity. Results indicate that if both materials have the same N, the singularity at the crack tip is reduced as beta increases; however, when beta becomes large there appears to be little change in the singularity for a fixed N. When the hardening exponents are not the same, the mathematical model assumes stress continuity across the interface. The results show that the order of the singularity depends largely on the softer material, with the largest stresses in the harder material.