Design and Characteristics of Electromagnetic Acoustic Transducers with Controllable Magnetic Force

doi:10.3901/JME.2021.02.046

Abstract

Abstract: Electromagnetic acoustic transducers(EMATs) is usually made of rare earth permanent magnet,which has the characteristics of super strong magnetic force. In actual testing,due to the uncontrollable magnetic force,there are some problems. Such as low energy conversion efficiency due to the insufficient bias magnetic field and inconvenient operation due to the excessive magnetic force. An electromagnetic ultrasonic transducer which can control the bias magnetic field and the magnetic force is presented. The proposed transducer can provide basic magnetic when electromagnetic is power off. In the reinforced or weakened mode,the average vertical flux on the lower surface of the transducer increased by 78.58% and decreased by 19.36% at most respectively and the average vertical flux of the steel plate under the transducer increased by 52.99% and decreased by 38.02% at most respectively when the steel plate is lifted 2 mm away. The experimental curves of probe magnetic force increasing with the decrease of lifting distance in three modes has been drawn. In the reinforced mode,the signal amplitude of thickness measurement for aluminum plate and steel plate is increased by 46.91% and 62.01% respectively. Based on the above research,the EMAT with controllable magnetic field not only has the function of controlling the magnetic force,but also can improve the amplitude of detection signal.

Key words: electromagnetic acoustic transducers(EMATs), bias magnetic field, controllable magnetic force, electromagnet, permanent magnet

CLC Number:

TB552

TU Jun, CAI Zhuoyue, ZHANG Xu, SONG Xiaochun. Design and Characteristics of Electromagnetic Acoustic Transducers with Controllable Magnetic Force[J]. Journal of Mechanical Engineering, 2021, 57(2): 46-52.

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