关键词: 电磁声传感器, 激光测振仪, 兰姆波, 离面位移, 面内位移

Abstract: Excited modes and frequency response are two key parameters of ultrasonic guided wave transducers evaluating. However, traditional transducers such as piezoelectric transducer and electromagnetic acoustic transducer (EMAT) can’t measure these two parameters efficiently because of the limit of frequency bandwidth and mode selection of themselves. Laser vibrometer can be employed to measure the raw in-plane and out-of-plane displacement of elastic waves in the structure without the limit of bandwidth. Thus it could be one of the ideal methods to identity the excited modes and measure the frequency response curve. A kind of omnidirectional lamb wave EMAT is been inspected by this method. The results show that the transducer can produce purity S0 mode in 150～200 kHz and both A0 and S0 mode in 50～150 kHz. It can be predicted that the method using laser vibrometer to detect the in-plane and out-of-plane displacement is an efficient method of evaluating the transducer and receiving Lamb waves, and can be widely used in no-contact measurement, high temperature testing and 3D visualization of elastic waves propagation.

Key words: Electromagnetic acoustic transducer (EMAT), In-plane displacement, Lamb wave, Laser vibrometer, Out-of-plane displacement