Beam-focused shear-horizontal wave generation in a plate by a circular magnetostrictive patch transducer employing a planar solenoid array

In recent studies, the radiation patterns of the Lamb and shear-horizontal (SH) waves in a plate generated by a circular magnetostrictive patch transducer were investigated experimentally and theoretically. As a follow-up to this research, a method of focusing SH wave beams is suggested by using a specially-configured planar solenoid array (PSA) instead of the figure-of-eight coil used in the earlier work. An SH wave is preferred in nondestructive evaluation because the first SH mode is non-dispersive. In the suggested configuration, the actuating dynamic magnetic field is produced by the solenoid that is superimposed on a static magnetic field in the perpendicular direction. Because the PSA configuration is similar to a meander coil, it is expected to better focus wave energy along a target direction. Furthermore, PSA is also expected to generate higher-power waves than a meander coil because its configuration is similar to that of the figure-of-eight coil. This paper presents the experimental results obtained with PSA, such as the wave radiation pattern. The radiation patterns obtained from the experiments are analyzed by a theory based on a two-dimensional distributed line source model