The fundamental threshold level - A new parameter for predicting cavitation erosion resistance

In order to predict and avoid cavitation erosion, it is necessary to know the resistance of materials to cavitation impacts. It is proposed that only cavitation impacts with energy larger than a certain threshold level affect the cavitation erosion of materials. Weak cavitation impacts have small impact energy, which cannot produce elastic or plastic deformation on materials. Cavitation erosion does not take place in this situation. On the other hand, strong cavitation impacts have large impact energy, which generates plastic deformation and/or causes damage with mass loss. It is proposed that only cavitation impacts that are larger than a certain threshold level affect the cavitation erosion of materials. In this paper, the existence of such a threshold level is revealed experimentally. The fundamental threshold level of the material is a new parameter suitable for the prediction of cavitation erosion rate. The erosion rates for several materials were determined by using a cavitating jet erosion test, which forms a new ASTM standard, ASTM G 134. The cavitation impacts induced by the cavitating jet were measured by means of a specially made PVDF transducer and the energy of the cavitation impacts were then calculated. The fundamental threshold levels for several materials were obtained from the relationship between the erosion rate and the energy of the cavitation impacts. A method to predict cavitation erosion quantitatively from the fundamental threshold level of the material and the measurement of cavitation impacts is proposed.