Affiliations: [a] State Key Laboratory of High Performance Complex Manufacturing, Central South University, Changsha 410083, Hunan, China | [b] School of Mechanical and Electrical Engineering, Central South University, Changsha 410083, Hunan, China | [c] Nonferrous Metal Oriented Advanced Structural Materials and Manufacturing Cooperative Innovation Center, Changsha 410083, Hunan, China
Correspondence:
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Corresponding author: Yunxin Wu, School of Electrical and Mechanical Engineering, Central South University, Changsha 410083, Hunan, China. Tel.: +86 731 8866 0476; E-mail: wuyunxin@csu.edu.cn.
Abstract: The application of Electromagnetic Acoustic Transducers (EMATs) into metal materials has been hard to implement for the technical problems of low transduction efficiency and high sensitivity of lift-off variation. The process of transmission and detection of a shear wave in a spiral coil EMAT is established based on a 2-D axisymmetric model using finite element method. A new equivalent reception circuit for an EMAT receiver is provided, and it takes the open-circuit voltage of a receiving coil, the coil equivalent impedance, impedance matching network, and the input impedance of a preamplifier into consideration. On this basis, the conversion efficiency and lift-off performance of the EMAT transmitter and receiver are investigated with respect to coil equivalent impedance, coil conductor diameter, impedance matching parameters, plate-to-coil distance and backplate thickness. Results indicate that compared with the specified EMAT without a backplate at a lift-off of 2 mm, the conversion efficiency and lift-off performance of the transmitting EMAT with a plate-to-coil distance of 1.5 mm can be respectively improved by 103.5% and 2.4 dB/mm, and the conversion efficiency and lift-off performance of the receiving EMAT with a plate-to-coil distance of 1.5 mm can be respectively enhanced by 85.5% and 1.6 dB/mm.
