A MOVING COHESIVE INTERFACE MODEL FOR FRACTURE IN CREEPING MATERIALS

We present a new cohesive interface model for quasi-static creep crack growth that is implemented within a moving-grid finite element model. A pseudo crack tip separates the cohesive process zone from the free surfaces of the crack. The moving-grid formulation models continuous c rack advance by describing relative motion between the pseudo crack ti p and the material. This eliminates the need for extensive mesh refine ment away from the current crack-tip location and supports both transi ent and direct steady-state solutions. A traction-separation law deter mines the energetic properties of the decohesion process and generates a simple criterion for crack advance. The new formulation remedies a problem in earlier models which permit a crack to heal on unloading. N umerical examples demonstrate the moving cohesive interface model in s tudies of steady-state crack growth. Adaptive grid refinement is used to control the accuracy of the solution.