Micromechanics of creep fracture: simulation of intergranular crack growth

A computational model is presented to analyze intergranular creep crack gro wth in a polycrystalline aggregate in a discrete manner and based directly on the underlying physical micromechanisms. A crack tip process zone is use d in which grains and their grain boundaries are represented discretely, wh ile the surrounding undamaged material is described as a continuum. The con stitutive description of the grain boundaries accounts for the relevant phy sical mechanisms, i.e. viscous grain boundary sliding, the nucleation and g rowth of grain boundary cavities, and microcracking by the coalescence of c avities. Discrete propagation of the main crack occurs by linking up of nei ghbouring facet microcracks. Assuming small-scale damage conditions, the mo del is used to simulate the initial stages of crack growth under C* control led, model I loading conditions. Initially sharp or blunted cracks are cons idered. The emphasis in this study is on the effect of the grain microstruc ture on crack growth. (C) 1998 Elsevier Science B.V. All rights reserved.