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

The stress and velocity fields ahead of a grain-boundary crack in a ma terial which deforms by Coble creep are investigated for a series of g rain sizes using the numerical analysis technique established by Cocks [1-3]. The numerical results are compared with the linear viscous fie lds obtained by the boundary clement method and the finite element met hod. It is demonstrated that a detailed knowledge of the micromechanic al processes of material transport and deformation are required to det ermine the stress and displacement fields for the grains which immedia tely surround the crack tip. But the response of the surrounding mater ial can be adequately described from a conventional linear viscous ana lysis of the problem.