Cavitation damage on metallic plate surfaces oscillating at 20 kHz

Plates of aluminium (UNI 4507) of about 2.55 cm2 and 1.0 mm thick, of different shapes, vibrating in a liquid at a frequency of about 20 kHz and subjected to strong cavitation damage on their central parts exhibit, on the zone near the edge, a reduction of cavitative effect up to inhibition. We named this phenomenon, the "border effect". Evidence is reported which demonstrates that the border effect, depending on the plate velocity, is related to the angle between the plate surface and its direction displacement, that is to the value of the component of the liquid velocity tangent to the plate.