Numerical simulation of grain-size effects on creep crack growth by means of grain elements

The effect of grain size on creep crack growth is investigated by means of a numerical technique in which the actual crack growth process is simulated in a discrete manner by grain elements and grain boundary elements. The gr ain elements account for the creep deformation of individual grains, while grain boundary cavitation and sliding are accounted for by grain boundary e lements between the grains. This grain-element technique allows for an inde pendent study of multiple grain size effects: a (direct) size effect relate d to the specimen size/grain size ratio or an (indirect) effect related to the effect of grain size on nucleation rate and creep resistance. Prelimina ry numerical results are presented concerning the direct effect of grain si ze, which predict that the crack growth rate and brittleness increase with grain size.