文献类型：期刊文献

英文题名：A Lorentz Force EMAT Design with Racetrack Coil and Periodic Permanent Magnets for Selective Enhancement of Ultrasonic Lamb Wave Generation

作者：Guo, Xinfeng[1];Zhu, Wujun[1];Qiu, Xunlin[1];Xiang, Yanxun[1]

机构：[1]East China Univ Sci & Technol, Sch Mech & Power Engn, Shanghai Key Lab Intelligent Sensing & Detect Tech, Shanghai 200237, Peoples R China

年份：2023

卷号：23

期号：1

外文期刊名：SENSORS

收录：;EI(收录号：20230213369870);WOS:【SCI-EXPANDED(收录号:WOS:000908674900001)】；

基金：This work was supported by the National Key Research and Development Program of China (2021YFC3001802) and the National Natural Science Foundation of China (Grant Nos. 12025403, U1930202, 51835003, 12174102 and 12004114).

语种：英文

外文关键词：electromagnetic acoustic transducer; ultrasonic Lamb waves; selective enhancement; periodic permanent magnets; Lorentz force; antisymmetric mode

摘要：This article proposes an electromagnetic acoustic transducer (EMAT) for selectively improving the purity and amplitude of ultrasonic Lamb waves in non-ferromagnetic plates. The developed EMAT consists of a racetrack coil and a group of periodic permanent magnets (PPMs). Two-dimensional finite element simulations and experiments are implemented to analyze the working mechanism and performance of the PPM EMAT. Thanks to the specific design, the eddy currents increase with increasing wire density and the directions of the magnetic fields and Lorentz forces alternate according to the polarities of the magnet units. Wires laid uniformly beneath the magnets, and the gaps between adjacent magnets generate tangential and normal Lorentz forces, resulting in-plane (IP) and out-of-plane (OP) displacements, respectively. The constructive interference occurs when the wavelength of the generated Lamb wave is twice the spacing of the magnets, leading to large amplitudes of the targeted ultrasonic Lamb waves. Therefore, the PPM EMAT is capable of generating pure symmetric or antisymmetric mode Lamb waves at respective frequencies. The results prove that the developed PPM EMAT can generate pure either S0 or A0 mode Lamb waves at respective frequencies. The increase in wire width and wire density further increases the signal amplitudes. Compared with the case of conventional meander-line-coil (MLC) EMAT, the amplitudes of the A0 and S0 mode Lamb waves of our PPM EMAT are increased to 880% and 328%, respectively.