On the Mechanism of Cavitation Damage

Abstract

A new method for producing cavitation damage in the laboratory is described in which the test specimen has no mechanical accelerations applied to it in contrast with the conventional magnetostriction device. Alternating pressures are generated in the water over the specimen by exciting a resonance in the "water cavity." By this means the effects of cavitation have been studied for a variety of materials. Photomicrographs have been taken of several ordinary (polycrystalline) specimens and also of zinc monocrystals. The zinc monocrystal has been exposed to cavitation damage on its basal plane and also on its twinning plane. X-ray analyses have been made of polycrystalline specimens with various exposures to cavitation. The results show that plastic deformation occurs in the specimens so that the damage results from cold-work of the material which leads to fatigue and failure. A variety of materials has been exposed to intense cavitation for extended periods to get a relative determination of their resistance to cavitation damage. It is found that, roughly speaking, hard materials of high tensile strengths are the most resistant to damage. While this survey is not complete, it has been found that titanium 150-A and tungsten are the most resistant to damage of the materials tested. Cavitation-damage studies, which have been carried out in liquid toluene and in a helium atmosphere, show that chemical effects can be, at most, of secondary significance.

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