Broadband tunable elastic metastructure based on one-dimensional phononic crystal

Abstract

Considering the manufacturing difficulty and tunability, a one-dimensional phononic crystal-type metastructure is proposed in this paper. By adjusting the distance between the mass oscillators installed on the connecting bar, that is, changing the length of the phononic crystal unit, the phase shift of the flexural wave can span over a full range of 0–2π and then the phenomena such as abnormal refraction, beam focusing, and self-acceleration can be realized based on the generalized Snell’s law. In addition, the method of multiple mass oscillator array design is used to broaden the operating frequency domain by increasing or decreasing the number of mass oscillators. This proposed method provides an innovative concept for realizing broadband tunable metastructures and has potential applications in the fields of vibration control, energy harvesting, and noise isolation.

A broadband tunable asymmetric transmission structure design

“…Figure 2(b), on the other hand, shows a geometric model of the one-dimensional phononic crystal metastructure, consisting of a set of six single-strip models for a group of cells. When the flexural wave is incident forward, for each functional cell, the phase shift characteristics are consistent with those of the reference [21], i.e., a force in the z-direction is applied at the left side of the geometric model as the initial excitation of the flexural wave. At this point, anomalous refraction will occur and prepare for re-transmission across the metasurface.…”

“…Here we take the width L 1 =0.04 m for metasurface 1 and L 2 =0.12 m for metastructure 2. In particular, we choose the metastructure 2 to consist of nine mass oscillators, which means that the operating frequencies will be reduced accordingly [21]. Combined l = c f p / and equation (3) one can calculate the wavelengths of the flexural waves at the frequencies of 19 kHz, 21 kHz and 22 kHz as m 0.0556 , m 0.0529 , and m 0.0517 , respectively.…”

“…They also proposed the concept of multiple mass oscillator array design (MMAD), and the operating frequency range of the metasurface can be further broadened by increasing or decreasing the number of mass oscillators. Based on this, Xuan [21] et al proposed a one-dimensional phononic crystal-type metastructure, which can achieve the phase coverage of flexural waves by simply moving the mass oscillators, i.e., changing the distance between the mass oscillators, just like adjusting the weights on a balance. Wang et al [22] further designed a simple mass oscillator metasurface with an approximately linear phase shift with respect to the number of oscillators.…”

“…In this paper, we propose a tunable broadband asymmetric transmission structure based on our previous work [21,22]. The structure consists of a mass oscillator metasurface and a one-dimensional phononic crystal metastructure.…”

A simple mass oscillator metasurface design with linear phase shift

“…The concept of multiple mass oscillator array design is also proposed, that is, by increasing or decreasing the number of mass oscillators, the working frequency range of the metasurface can be further expanded. Xuan et al [27] designed a one-dimensional phonon crystal type metastructure, in which the distance between the mass oscillators can be varied to achieve arbitrary modulation of the wave beam. This structure also uses the concept of multiple mass oscillator array design, which can significantly broaden the operating frequency range of the metastructure.…”