Subharmonic Wave Generation at Interfaces of a Thin Layer between Metal Blocks

Subharmonic waves were significantly generated at the interfaces of aluminum blocks and an aluminum foil subjected to a 6 MHz burst incident wave. Although the fundamental wave amplitude was linearly varied with input voltage, the subharmonic waves generated at the interfaces indicated strong nonlinearity. Analyzing the relationship of the subharmonic wave generation, the applied contact pressure, and the stress of the ultrasonic wave has revealed that subharmonic components can be generated when the incident ultrasonic wave has sufficiently large stress to separate the contacting interfaces. At rough surfaces, the subharmonic peak could not be observed because a large true contact pressure prevented the interfaces from separating. (c) 2013 The Japan Society of Applied Physics