Liquid impact on a bilinear elastic-plastic solid and its role in cavitation erosion

The collapse of cavitation bubbles generates microjets which can cause local plastic deformation on neighbouring solid materials. This deformation takes the form of pitting which will eventually lead to large-scale material erosion. A model is presented which predicts the relative dimensions of the pits as a function of bubble collapse pressure, the shape of the microjet and the mechanical properties of the solid. The high pressures required to cause material deformation are generated by a water hammer mechanism and the solid is taken to have a simple bilinear elastic-plastic response. Measurements on pits produced by both flow and spark-generated cavitation are found to lie within the bounds predicted by the model. Both the measurements and the model suggest that there is a threshold microjet velocity below which no damage occurs, although such behaviour is masked, in practice, by statistical variations.