Bimaterial interfacial crack growth with strain gradient theory

The purpose of this paper is to investigate the effect of material heteroge neity on damage evolution and subsequent crack propagation in bimaterial sy stems. Strain gradient theory analysis reveals that a higher stress triaxia lity always occurs on the softer material side due to the material mismatch in yield capacity and the corresponding strain gradient along the interfac e. High stress triaxiality is a major condition which promotes ductile dama ge and facilitates crack growth. To investigate this link, numerical simula tions of ductile interface crack growth are performed using a damage based constitutive model. Both the numerical and experimental results show that a crack may grow along the interface or deviate into the softer material, bu t never turn into the harder material. The theoretical and numerical analys is reveal three factors which strongly affect the direction of crack growth and the resistance capacity of the bimaterial system against fracture. The se are the boundary conditions which determine the global kinematically adm issible displacement field, the stress/strain gradient near the interface d ue to the material mismatch, and the distance from the crack tip to the int erface.