High-Speed Observations of the Vibratory Cavitation Accompanying Hard Erosion

Abstract

In this paper, the term "hard erosion" refers to erosion which is faster than ordinary erosion by a factor of two or more. Here, we carefully observe cavitation aspects of several types and the corresponding eroded surfaces in typically accelerating vibratory erosion tests on a typical erosion-resistant material of 304 stainless steel by means of high-speed and SEM photography, under a specified condition of uniform cavitation nuclei size distributions. Hard erosion clearly results from very high shock pressures accompanied not by microjet bubbles or bubble clusters, but by collapsing massive bubbles. The massive bubbles very rapidly develop within the low-pressure region where the Hooper vortex is predominant around the test specimen, and then collapse, resulting in marked shock waves by which almost all of the tiny bubbles are destroyed.