Creep failure by degradation of the microstructure and grain boundary cavitation in a tensile test

Abstract

For tensile test specimens under constant load creep failure is analysed, based on constitutive relations that account for the nucleation and growth of grain boundary cavities in polycrystalline metals at high temperatures. The material model is formulated in the context of finite strains, so that failure due to loss of cross-sectional area, as well as the possibility of necking, are incorporated in the analysis. Furthermore, the present investigation accounts for the possibility of creep acceleration induced by a gradual degradation of the microstructure. The results include cases in which the three types of failure mechanisms interact, as well as cases where any one of the mechanisms dominate. Most of the investigation is based on a simple one-dimensional model analysis; but a full axisymmetric numerical analysis is used to investigate a few cases, in which necking plays a role.