Predicting microfracture in ceramics via a microcontact model

The. point of view is taken that for ceramics, cone cracking on the microscale assumes the same role as plastic asperity deformation in metal materials, namely, as the agent causing stress raising micropits which precipitate surface fatigue. Empirical fracture data are interpreted in the context of published fracture mechanics analyses of cone cracking in static and sliding contact and used within the Greenwood- Williamson stochastic microcontact model to predict the relative likelihood of cone cracking when a rough flat ceramic contacts a smooth ceramic flat of the same material. The Greenwood-Williamson model is reviewed and its predictions are shown, for the steel and ceramic surfaces considered, to compare favorably to the more general anisotropic microcontact model ASPERSIM. A microfracture index analogous to the Greenwood-Williamson plasticity index, is shown to be a determinant of the ability of a surface to resist cone cracking.