Simultaneous velocity measurement of multi mode's Lamb waves with two-beam laser interferometer

摘要

Multi-mode Lamb waves in an aluminum plate of 2.0 mm in thickness were excited by a Q-switched Nd: YAG laser. The Lamb waves were received at two different positions by a laser interferometer. With the phase spectrum method and the moving average, we have measured the dispersion curves of the group velocities of various modes. The measured dispersion curves (S_0, A_0, A_2, A_3, A_4, A_5) agree well with the theoretical dispersion curves in velocity range of 2000 - 3000 m/s and in the frequency x thickness range of 2.0～18.0 MHz mm.