The ASTM G32 test is used to estimate the relative resistance of a given material to cavitation erosion that could be encountered. Pumps, hydraulic turbines, dams, valves, ship propellers and hydorfoils are some examples where cavitation erosion can be significant. For the ASTM G32 test, cavitation damage is produced on the face of a specimen specimen vibrated while immersed in a luquid. Although the mechanism for generating cavitation with a vibratory apparatus is fundamentally different than that ocurring in hydraulic machines or cavitating flows, the nature of the material damage is believed to be basically similar. (www.astm.org)
Disruptor horns (probes) transmit ultrasonic energy into a solution. The Branson Sonifier ultrasonic disruptor horn available at SAFL is capable of transmitting ultrasonic vibrations greater than 20 kHz into a solution. When applied to water, this creates a periodic pressure field which induces the growth and collapse of a cloud of cavitation bubbles.
The disruptor horn has been used to illustrate the effects of cavitation on different types of stone over long periods of time (Scablands in North America). Over long periods of time and under the correct conditions, cavitation will contribute to erosion during cataclysmic floods.
Figure 1: Schematic of ASTM Vibratory Apparatus
Video 1: Erosion of St. Petersburg sandstone due to cavitation generated by an ASTM vibratory apparatus.