STRESS-PROMOTED INTERFACE DIFFUSION AS A PRECURSOR OF FRACTURE

Stress-modulated surface mass transport offers a possible path to the ultimate fracture of brittle solids. A positive feedback between the l ocal geometry, stress concentration, and chemical potential on a rough surface results in the formation of fracture precursor. Starting from general kinetic equations, we propose a reduced two-parameter descrip tion of a growing concavity. A suggested interpolation enables us to o btain an ordinary differential equation describing the precursor evolu tion; it starts from a smooth boundary and under certain conditions ge nerates a cusp singularity. This sharp notch becomes a stress concentr ator and facilitates direct brittle fracture. The diffusion-limited pr efracture mechanism, though slow, circumvents a crack nucleation barri er and can be a determining factor for the durability of materials.