Stress redistribution during Nabarro-Herring and superplastic creep

Abstract

The creep resistance of a two-dimensional system of hexagonal grains is analysed for both Nabarro-Herring and grain-boundary sliding rate-controlling mechanisms. Both mechanisms are shown to operate sequentially. When one is much faster than the other the shear and normal stresses on the boundaries are shown to differ from those in an elastic body. The creep rate is related to the boundary stresses and is shown to be independent of orientation of the uniaxial applied stress to the hexagonal array. The grains are allowed to roll over neighbouring grains and it is shown that this can increase the creep rate. The conditions under which grains can exchange neighbours are discussed, and also the effect of the resulting irregular shapes on the creep rate.