Reflective elastic metasurface for flexural wave based on surface impedance model

Abstract

Inspired by the recent advance of acoustic metasurface in achieving wave manipulation, a surface impedance matched method rather than Generalized Snell's Law for designing a reflective elastic metasurface is presented to redirect the flexural waves without much loss in thin plates. The designed elastic metasurface that is simply fabricated by regularly arranged structural beams allows nearly arbitrary control of reflected waves, including extraordinary reflection, normal incidence and negative reflection. Obtained results show that the designed metasurface has a high accuracy of redirecting reflected waves into desired way and simultaneously the scattering waves in other directions are efficiently suppressed. We also demonstrate the elastic metasurfaces with free and fixed boundary conditions which all show electromagnetic and acoustic analogies of anomalous reflection response. Based on the surface impedance matched method, the theoretical prediction of redirecting reflection waves has an agreement with numerical simulation and experiments, and we think that the minimum characteristic scale of a non-resonant reflective elastic metasurface is confined to the first period of input impedance. This work provides an effective strategy for designing an elastic metasurface, and it is potentially useful for the functionalities of flexural wave manipulation.