Steering of flexural wave propagation in tunable magnetorheological elastomers metasurface by modulating magnetic field

Abstract

Metasurfaces have remarkable power for steering flexural waves, and most of the existing studies for phase modulation of the metasurface concentrate on changing the geometrical parameters of the structure. However, when the external conditions change, these parameters cannot be adjusted in real-time, which is not convenient for engineering applications. Therefore, in this paper, a tunable magnetorheological elastomers (MREs) metasurface composed of MREs and three-dimensional (3D) printing material polylactic acid (PLA) is proposed to steer the propagation of incident flexural waves arbitrarily. The phase shift in a full 2π span can be achieved by manipulating the applied magnetic field to tune the modulus of the MREs. Then, based on the Generalized Snell's Law, MREs metasurfaces with different refraction angles are designed by adjusting the applied magnetic field, including positive refraction and negative refraction. In addition, wave focusing and self-bending beam effects are also investigated. Different focal spots and self-bending beam paths can be realized by adjusting the applied magnetic field. Finally, a sample of the tunable MREs metasurface is fabricated by 3D printing technology composed of host plate and MREs units to demonstrate the focusing effect experimentally. The results show that the designed tunable MREs metasurface only requires a small magnetic field to achieve deflecting of the flexural waves (the maximum magnetic field is 66.93 mT), which is easy to implement in practical engineering. The simulated and experimental results of the elastic wave focusing effect are in good agreement. The proposed metasurface provides a guiding design for elastic wave modulation.