Modular elastic metasurfaces with mass oscillators for transmitted flexural wave manipulation

Abstract

In the present study, a modular mass oscillator elastic metasurface (MMEM) is proposed to manipulate the wavefield of flexural waves by assembling and replacing mass-oscillator-like functional units. Based on the bandgap analysis of phononic crystals, the MMEMs were found to achieve a full 2 π range of phase shift with relatively high transmission using functional unit arrangements of varying sizes (masses). According to the generalized Snell’s law, the modulation of abnormal refraction, lens focusing, and beam self-acceleration can be realized. To broaden the operating frequency domain, we present the idea of a multiple mass oscillator array design, which can control flexural waves at broadband frequencies of 13–41 kHz by adding/removing mass oscillators within a functional unit. This study presents a method to realize tunable metasurfaces and provides an innovative concept for broadening the operating frequency of elastic metasurfaces.

Reconfigurable flexural waves manipulation by broadband elastic metasurface

“…The phase shift of elastic waves can be tuned mainly by changing their velocities through a resonant or non-resonant way. Usually, the former can be achieved by introducing resonant units such as pillars or columns [13][14][15][16][17][18][19][20], zigzag units [21][22][23][24][25], and blocks [26][27][28][29][30] into the structure. The latter, however, can be realized by grooves [31], notched units [32], strips [33,34] or composite strips [35,36], etc.…”

“…In-plate [21][22][23][24] and out-of-plate [25] zigzag units were proposed to design metasurfaces for source illusion, refraction, focus, asymmetric transmission and ultrathin waveguide of A0 Lamb waves. Changing the sizes of resonant blocks added to beams was also able to manipulate the phase of the transmitted flexural wave [26]. Making slits or openings on a plate can form resonant units for the deflection of longitudinal wave [27] and broadangle modal conversion between P-and SV-waves [28] in plates.…”

Experimental Evidence of High‐Efficiency Nonlocal Waterborne Acoustic Metasurfaces

“…[ 1–10 ] Based on the generalized Snell's law (GSL), [ 11 ] broadband anomalous reflection, focusing, acoustic filter, and reflection have been achieved by different phase modulation methods. [ 12–15 ]…”

“…[1][2][3][4][5][6][7][8][9][10] Based on the generalized Snells law (GSL), [11] broadband anomalous reflection, focusing, acoustic filter, and reflection have been achieved by different phase modulation methods. [12][13][14][15] More recently, WAMs have received extensive interest. Exotic waterborne acoustic behavior has been observed successively, such as beam splitting and asymmetric transmission, [16] beam steering, [17] focusing, [18,19] carpet stealth, [20][21][22] the extraordinary reflection, [23] water-filled underground siphon, [24] and plane waves conversion.…”

Underwater Transmitted Wavefront Manipulation Based on Bubble-Arrayed Acoustic Metasurfaces

“…To modulate waves in 2D scales, the concept of metasurfaces was proposed in optics [3] based on the generalized Snell's law (GSL) [4]. With the advantage of ultrathin and lightweight compact structure, the acoustic metasurface has also attracted broad attention in the past decade [5][6][7][8][9][10]. By intriguingly designing the functional units, multiple functionalities can be realized, such as abnormal reflection [11,12], negative refraction [13,14], beam focusing [15], vortex sources and perfect absorption [16][17][18][19], and self-bending beams [20].…”