Fundamental Studies on Cavitation Erosion

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Cavitation erosion has been considered the fatigue failure of the surface due to repeated collapse pressures of cavitation bubbles. The present paper deals with severe erosion tests using the magnetostrictive oscillator vibrating in water, and gives the results. Cavitation damages consist of pitting by impact fracture and falling off by fatigue failure of the surface. The weight loss in the initial period is due to small pits, while the large particles due to fatigue predominate in the weight loss in the stationary period. The small pit is made by a single blow of large collapse pressure of some bubbles which produces the maximum shearing stress beneath the surface, and the falling off of large particles is due to the propagation of fatigue cracks by repeated smaller collapse pressure of numerous bubbles. The frequency distribution of collapse pressure depends on the cavitation conditions and the distribution curve is obtained by using simple hypothesis. As the surface tension of water is decreased by an active agent, the distribution curve shifts toward smaller collapse pressure, and the erosion damage also decreases.
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