Enhancement of Rayleigh Wave Generated by Electromagnetic Acoustic Transducer Based on New Magnetic Configuration

摘要

Electromagnetic acoustic transducers (EMATs) are widely used to evaluate and detect metal. The ultrasonic signal may be masked by noise for the poor conversion efficiency, which is one of the main obstacles hindering the development of electromagnetic acoustic technique. A type of magnet configuration is utilized to enhance the conversion efficiency in this paper. The magnetic field generated by new EMAT is enhanced. Both the horizontal and vertical magnetic fields are improved. Compared with the conventional configuration EMAT, simulation results show that the amplitude of ultrasonic produced by new EMAT is increased significantly. To further enhance the amplitude of ultrasonic, the effect of magnet parameters on the magnetic field distribution is investigated. Increasing the magnet width and height, and decreasing the distance between the two magnets will improve the magnetic field. Decreasing the distance between magnets allows a stronger magnetic field to participate in the reaction, and the vertical magnetic flux density becomes larger as well. The effect of increasing the width and length of the magnet is similar. The vertical and horizontal magnetic flux density will increase at the same time. It is impossible to enhance the amplitude of the Rayleigh wave unlimitedly by optimizing the parameters. After considering the volume of electromagnetic acoustic transducer and manufacturing, the parameters are determined. Finally, the EMATs corresponding to the conventional and new parameters are used to carry out the experiments whose results indicate that the conversion efficiency is increased by 84% with the new EMAT.