Cavitation Erosion

Abstract

Cavitation erosion is discussed through the measurements of the cavitation bubble collapse pressures and the observations of the erosion processes of various materials. The magnitude of impact pressures (impact loads) produced by the collapse of bubbles fluctuates over a wide range, but the number of bubble collapse impacts necessary to form erosion pits impulsively is remarkably small. Cavitation damage is found to be dominated by fatigue fracture due to the repetition of small impact loads as well as a small number of large impact loads. However, there is a threshold value at which impact load begins to contribute to the fatigue fracture of the surface. Comparing the distributions of impact loads with the hypothetical S-N curves of fatigue, Miner's law is followed for the incubation period and the erosion rate regardless of the testing apparatus, cavitation conditions and materials. The erosion resistances of the msterials are also discussed.