Effects of rigid grains separation on the diffusive growth of crack-like cavities on grain boundaries

Previous analyses of diffusive growth of grain boundary cavities in the limiting case of a crack-like mode under the rigid grain assumption have assumed that the effect of grains separation rate on the cavity growth rate is negligible. This is more valid when the cavity growth rates are very high. Here, we investigate the appropriateness of this assumption at lower cavity growth rates by incorporating the contribution of the rigid grains separation rate in the analysis. The resulting geometry of the crack-like cavity near its tip is given. This information is used to set boundary conditions for the rigid grain model. Numerical results for the applied stress versus the cavity growth rate are presented. They are compared with those given by Chuang, Kagawa, Rice and Sills (1979), whose analysis assumes the rate of separation of the grains to be small compared to the cavity growth rate. Comparison with the results of Chuang et al. (1979) for the rupture time based on cavity growth to coalescence is also made.