Influence of low pressure on laser inducing leaky Lamb wave and Scholte wave at air–solid interface

Abstract

A setup with Q-switched Nd:YAG laser inducing acoustic wave at air–solid interface and air-coupled optical deflection sensor was developed to research the influences of low air pressure on laser inducing leaky Lamb and Scholte waves at air–solid interface. The solid plate is settled in an airtight vessel abounded with standard air and its pressure can be adjusted by a vacuum pump. By experiments, the waveforms of laser induced interface acoustic waves, leaky Lamb and Scholte waves, under air pressures from 0.02 to 0.08 MPa with 0.01 MPa interval were first measured comprehensively. From the waveforms, we find that with increasing air pressure, the leaky energy of Lamb waves increase linearly and the amplitude of Scholte waves increase exponentially, but the velocity of Scholte waves decreases obviously.