Vibration control of flexural waves in thin plates by 3D-printed metasurfaces

Abstract

Steering flexural waves in thin plates benefits several applications, including vibration energy harvesting and micro-electro-mechanical systems (MEMS). This study proposes a technique using metasurfaces based on U-shaped phononic beams to realize the flexural wave control. This technique demonstrates the use of metasurfaces made of the same material as that of the host plates wherein the flexural waves are to be controlled, which significantly facilitates the fabrication of metasurfaces. The total height H of the U-shaped beams is selected to change the effective bending stiffness and consequently tune the effective phase velocity of flexural waves in the U-shaped phononic beams. Numerical simulations verify that the effective phase velocity of flexural waves in the U-shaped phononic beams is highly dependent on H. A macro-model is proposed to estimate the effective phase velocities. The phase shift and transmittance of flexural waves transmitted via U-shaped phononic beams with different values of H are calculated. A full 2π phase shift can be obtained by a change in H within an appropriate range while maintaining the transmittance at a relatively high level. As illustration examples, two subwavelength metasurfaces (refraction and focusing) for flexural waves in thin plates are designed, 3D-printed using VeroPureWhite, and tested. All experimental measurements support our proposed technique for the manipulation of flexural waves in thin elastic plates by metasurfaces.