THE EFFECT OF GRAIN-SIZE ON THE STRESS AND VELOCITY-FIELDS AHEAD OF A CRACK IN A MATERIAL WHICH DEFORMS BY COBLE CREEP

The stress and velocity fields ahead of a grain-boundary crack in a material which deforms by Coble creep are investigated for a series of grain sizes using the numerical analysis technique established by Cocks [1-3]. The numerical results are compared with the linear viscous fields obtained by the boundary clement method and the finite element method. It is demonstrated that a detailed knowledge of the micromechanical processes of material transport and deformation are required to determine the stress and displacement fields for the grains which immediately surround the crack tip. But the response of the surrounding material can be adequately described from a conventional linear viscous analysis of the problem.