On creep fracture by void growth

The growth of void-like creep damage is analysed. Voids can grow by mechanisms controlled by grain-boundary diffusion, by surface diffusion, by power-law creep, and by any combination of two of these Approximate analytical equations for the growth rate by each mechanism, under multiaxial stress states, are developed, and related to a number of published analyses. The growth equations are integrated to give times and strains to fracture under constant (multiaxial) stress, constant load and two simple load histories. Both quasi-uniform and non-uniform distributions of voids are considered. The formulation can be related to the continuum damage method of Kachanov and suggests modifications to this method. It leads to a new prescription for extrapolating creep data. A unified picture of void growth appears possible, embracing most aspects of previously published models.