Focused ultrasound induced free-surface breakup and damage in acrylic plates

This paper deals with water-surface breakup, spray formation and material damage caused by ultrasonic waves with the frequency of 1 MHz which were focused at the free surface in the cases where a 3 mm thick acrylic plate was present or not. From the observations by means of high-speed photography with the maximum rate of 50,000 frames/sec, together by taking plenty of snapshots, it was found that when nothing was present in a fluid a variety of surface responses took place depending on the acoustic properties of ultrasound, especially acoustic intensity. When an acrylic plate existed in a fluid, wave interaction played an important role to cumulative damage in an acrylic plate.