A metasurface for suppressing mode conversion and achieving directional reflection of shear horizontal wave

The lowest-order shear horizontal (SH 0 ) guided wave in a plate is crucial for nondestructive testing and structural health monitoring due to its nondispersive nature. However, mode conversion at the interface for the SH 0 wave complicates the received information and increases the difficulty of signal analysis. In this work, an elastic metasurface is proposed to suppress mode conversion at the interface and to reflect the SH 0 wave directionally. The metasurface comprises a series of rectangular elements with a specific phase gradient covering the 2 π phase range. The effectiveness of the proposed metasurface is confirmed through finite element simulations and experimental validation. The results indicate that the metasurface can significantly reduce the amplitude of the reflected lowest-order symmetric Lamb wave when compared to the reflection without the metasurface, while simultaneously allowing the reflected SH 0 wave to propagate at the designed angle. Furthermore, the metasurface maintains its functionality for SH 0 wave with incident angles varying from 0° to 25°. This study provides a viable approach for suppressing mode conversion and modulating the reflection behavior of SH 0 wave, which is expected to find applications in nondestructive testing and structural health monitoring.