Exploration of a Possibility to Assess Erosive Cavitation by Acoustic Emission Technique
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- Ris (Zotero)
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In order to complement the conventional model scale cavitation erosion test methods, research is being undertaken to explore the use of an acoustic emission technique to provide a quantified measure of cavitation. The amplitude of AE signals within a structure, such as a propeller shaft, is assumed to change in proportion with the pressure impact loads from the collapse of vapour cavities. Analysis of the power spectrum of the signals should show some meaningful parameters in relation to the cavitation intensity and frequency, which can be used as a quantitative index of the cavitation erosion risk. The main results of a preliminary study are provided with illustration of some results of the experiment using a G-32 type vibratory cavitation apparatus combined with a CFD simulation. It is found that the AE power spectrum indicated two main peak frequencies from the acoustic excitation and the sub-harmonic oscillation of the acoustic cavities as reported in the other relevant literature. However, the acoustic driving frequency component appeared much stronger and the sub-harmonic oscillation frequency appeared as a band rather than a single peak. An investigation on the vibration characteristics of the sonotrode revealed the vibration amplitude could vary in the order of about 15 % of that desired. This might partly explain the reason of the frequency band formation around a central frequency of the sub-harmonic oscillation. Further investigation on the possible causes is underway. It has still a long way to go to establish a new model test methodology, but it appears the AE signal amplitude response has a certain relation with the magnitude of cavitation impact loadings.