Investigating the Influence of Design Frequency on the Ultrasonic Signal of PFSV-EMATs

The point-focusing shear vertical wave electromagnetic acoustic transducer (PFSV-EMAT) with a concentric meander line (CML) coil has been developed to detect and size micro defection concealed within a certain depth of materials. It is proved to be sensitive to the design frequency, which is associated with the spacing of CML coil. In this work, the relationship between the design frequency and characteristic of PFSV-EMATs, such as the particle displacement and focal offset, is studied quantitatively. First, the configuration and working principle of PFSV-EMATs are introduced comprehensively. Then, a finite element model is established to simulate the incentive and propagation process of ultrasonic waves. In addition, the relationship between magnet-to-coil radius ratio and the signal amplitude generated by the PFSV-EMATs is explored to ensure the consistency of transducer parameters at different frequencies. Furthermore, under the optimal magnet-to-coil radius ratio, the influence of design frequency on the characteristic of PFSV-EMATs is studied. Finally, the experimental results show good agreement with the simulation results and indicate that the signal amplitude and point-focusing performance of PFSV-EMATs employing CML coils could be improved by carefully choosing the design frequency.