Effects of ambient pressure and fluid temperature in ultrasonic cavitation machining

One of the prevalent material removal mechanisms in vibratory ultrasonic machining (USM) is cavitation erosion. The slurry-used USM process contains a mixture of water and abrasive particles-hence, strictly not pure cavitation. Cavitation erosion is the process of surface modification by generation and collapse of vapor bubbles on the workpiece surface inside a liquid medium. Although considerable research has been devoted in finding the material removal mechanism, rather less attention has been paid on the effect of pressure and temperature in cavitation erosion. Hence, efforts have been taken in this investigation to identify the mechanism of cavitation collapse at various ambient pressures and fluid temperatures and to investigate their effects in machining using AISI 304 stainless steel and aluminum 6061-T4 with wire EDM surface. Ambient pressure and temperature were varied from 100 to 400 kPa and 10 to 90 A degrees C respectively. The outcomes showed that mass loss increased until 400 kPa and 50 A degrees C and then declined with increase in liquid temperature. Scanning electron microscope (SEM) images showed that most of the test surface deformed plastically with surface undulations and material removal was by micro-pitting. Further, suggestions are provided to control the machining conditions from the identified cavitation collapse mechanism. Optimal conditions to accelerate the machining process were found to be 50 A degrees C and 400 kPa.