Formulation of Cavitation Erosion Behavior based on Logistic Analysis

Cavitation erosion tests were carried out using vibratory apparatus to obtain the volume loss curve and the volume loss rate curve for aluminum oxide and pure copper. When the aluminum oxide was exposed to cavitation, the erosion originated at defects such as pores and holes. Particles were removed granule by granule, and the erosion pits spread throughout the speciment surface. The number of erosion pits increased exponentially. By the analyses of multiplication and annihilation process of the erosion pits, the model of the volume loss curve was established. The volume loss rate curve u and the volume loss curve V with exposure time were expressed by three parameters α, β and c in the following equation. u=α/β 1/(1+e^<-αt>), V=α/βt-1/βln((1+C)/(1+ce^<-αt>)) Especially, the parameter c relates to a reciprocal of the initial volume loss rate, and was estimated to be low for the material with high initial defect density. As was expected, the value of c is lower for aluminum oxide than that for pure copper, and the value is lower for a roughened specimen of copper than that for a smooth specimen. It was concluded that the calculation based on this model corresponds well with volume loss curve and volume loss rate curve due to cavitation