SEDL / STP / STP474-EB / STP26861S

Cavitation Damage Mechanism and Its Correlation to Physical Properties of Material

Hirotsu, M
Professor of engineering, Faculty of Engineering, Meiji University, Kawasaki,

Pages: 19    Published: Jan 1970

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Abstract

Several test surface configurations were proposed by which better reproducibilities of experimental results were achieved. There were no mechanical difficulties in machining and polishing test specimens.

Cavitation phenomena on the surface of a specimen were photographed with a special camera arrangement at adequate intervals within a cycle. These phenomena have been classified into three processes: generating, growing, and collasping. Each regime was studied closely by the aid of photographs.

Long exposure time tests, with the use of the proposed test specimens, showed mean depth penetration rate (MDPR) curves somewhat different from those previously reported. They reached the maximum MDPR in a relatively short time and decreased.

Observations of the damaged surfaces were made by means of an optical roughness meter and an ordinary microscope. The curves of maximum pit depth versus time showed a close relation to the MDPR curves.

To find a correlation between damage and physical properties of material, maximum MDPR and ultimate resilience (UR) were employed. In a very rough approximation, the correlation was (maxMDPR×area)×(UR)≑constant

The advantage of taking the maximum MDPR as a reference value was shown clearly in the results of stationary test specimen experiments. Within the limits of uniform damage patterns, the following simple relation was found. maxMDPR≑Ke-βx where x is a separation distance and β is a constant having no relation with the nature of material tested. It is assumed that K is the most characteristic value of maximum MDPR, since it is a hypothetical value when there is no vibratory motion to induce cavitation.