Experimental demonstration of extremely asymmetric flexural wave absorption at the exceptional point

Li, Xiaopeng; Yu, Ziqi; Iizuka, Hideo; Lee, Taehwa

doi:10.1016/j.eml.2022.101649

Cited by 14 publications

(12 citation statements)

References 38 publications

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“…Another identical cube functions as a support connected to the other end but on the bottom surface of this beam strip. In our previously investigated coupled mechanical resonators on a two-port system [27], we demonstrated that the coupling distance and the mechanical damping played essential roles in achieving perfect absorption due to the scattering toward the two ports as well as the neighboring resonators. Here, in the one port system as shown in Figure 1, we consider a general case where the scatterer is placed at x = d away from the free end.…”

Section: Designmentioning

confidence: 99%

“…An artificial absorbing layer made with high damping materials is carefully placed on the surface of the left end of the host beam to suppress the reflected waves from that boundary. A laser vibrometer is used to scan the pointwise velocity responses of the host beam in the highlighted orange region with 21 points and a point distance of 5 mm [27]. The measured responses are processed to calculate the wave reflection (r) and absorption (α = 1 − r) coefficients.…”

Section: Sample Fabrication and Experimental Setupmentioning

confidence: 99%

“…Similar to optics [31], by placing a scatterer at or near a waveguide boundary, i.e., a perfect reflecting mirror, in a one-port system, the perfect absorption is observed, through the tuning of loss. The one-port and twoport near perfect flexural wave absorbers on 1D structures have also been reported using acoustic black hole (ABH) [30], Willis coupling [27,29,32], coated strip-like beam [26,28], etc. However, most of the existing passive perfect absorbers achieve perfect absorption only at a single frequency point, which hinders their practical applications.…”

Section: Introductionmentioning

confidence: 99%

“…Most recently, efforts are more paid to the design of elastic metasurfaces [14][15][16][17][18][19], which are a new kind of planar metamaterials, to manipulate wavefronts via a suitable arrangement of discontinuities on a material interface or boundary. Perfect wave absorption, an exceptional wave control ability to totally absorb incoming waves, has been demonstrated in 1-dimensional (1D) or 2-dimensional (2D) acoustic and elastic metamaterials/ metasurfaces using passive [20][21][22][23][24][25][26][27][28] or active [18,29] approaches. Examples of the perfect absorption demonstrated in optics, acoustics, as well as elastic waves, were achieved by satisfying the critical coupling condition [23-27, 30, 31], in which the balance between the energy leakage and the inherent losses of the resonator was fulfilled.…”

Section: Introductionmentioning

confidence: 99%

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Experimental study of a tunable perfect flexural wave absorber with a piezoelectric shunted resonator

Yu²,

Lee³

2022

Front. Phys.

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Metamaterials and metasurfaces have been widely developed recently for extraordinary acoustic and elastic wave control at a deep subwavelength scale. Perfect wave absorption as an extreme case to totally absorb the impinged waves has gained great attention, whereas most existing designs based on local resonance lack tunabilities, making perfect absorption be observed at a single frequency. To overcome this drawback, in this work, we design and fabricate a tunable inductance-resistance (LR) shunted mechanical resonator via a bonded piezoelectric patch for perfect flexural wave absorption at low frequency. The LR shunted absorber could be reconfigured to a broad frequency range for perfect flexural wave absorption. The tunable perfect absorption performances are validated through experiments and unit absorption is achieved in experiments. In the end, to further highlight the advantages of shunted damping we numerically demonstrate that the absorption spectrum could be enhanced to broadband absorption with a negative capacitance and an inductance-resistance circuit (NC-LR) connected in parallel. The approach proposed provides an alternative solution to achieve perfect wave absorption in the low-frequency range and enables practical application in complex engineering structures.

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Section: Designmentioning

confidence: 99%

Section: Sample Fabrication and Experimental Setupmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Experimental study of a tunable perfect flexural wave absorber with a piezoelectric shunted resonator

Yu²,

Lee³

2022

Front. Phys.

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“…The EP not only can be used for the UZR but also can achieve the unidirectional perfect absorption (UPA), which provides convenience for designing dynamic control devices [27]. To obtain the UPA, Li et al [28] constructed an asymmetrical metabeam with a pair of loss-induced asymmetrical resonators to find the EP and the critical coupling condition for extremely asymmetric flexural wave absorption based on the intrinsic viscosity loss. However, the EP and the UPA were determined and found to be not tunable for their fabricated asymmetrical metabeam.…”

Section: Introductionmentioning

confidence: 99%

Versatile non-Hermitian piezoelectric metamaterial beam with tunable asymmetric reflections

Xia

et al. 2022

Front. Phys.

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Non-Hermitian systems have been widely utilized to achieve specific functions for manipulating abnormal wave motion, such as asymmetric mode switching, unidirectional zero reflection (UZR), and unidirectional perfect absorption (UPA). In this paper, a novel non-Hermitian piezoelectric metamaterial beam is proposed to realize the tunable UZR of flexural waves. The unit cell of this non-Hermitian metamaterial beam consists of a host beam and two pairs of piezoelectric patches shunting different resistor–inductor circuits. Based on the flexural wave theory, the transfer matrix method is introduced to analyze the influence of electrical boundary conditions on the UZR and further clarify the relationship between the UZR and the exceptional point. The exceptional point depends only on the dissipative circuit, and it has no need for the balanced gain and loss like parity–time symmetric metamaterial. Furthermore, the UZR for the desired frequency is realized by applying a genetic algorithm, and its effectivity is experimentally validated. In addition, the non-Hermitian metamaterial beam is designed to realize the UPA of flexural waves. Results indicate that the proposed metamaterial beam is versatile and can achieve tunable manipulations of asymmetric wave propagations and has widely promising applications in many fields, such as non-destructive testing, enhanced sensing, wave isolation and vibration attenuation.

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Reconfigurable metamaterial for asymmetric and symmetric elastic wave absorption based on exceptional point in resonant bandgap

Xia

et al. 2022

Appl. Math. Mech.-Engl. Ed.

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Elastic wave absorption at subwavelength scale is of significance in many engineering applications. Non-Hermitian metamaterials show the ability in high-efficiency wave absorption. However, the single functionality of metamaterials is an important limitation on their practical applications for lack of tunability and reconfigurability. Here, we propose a tunable and reconfigurable non-Hermitian piezoelectric metamaterial bar, in which piezoelectric bars connect with resonant circuits, to achieve asymmetric unidirectional perfect absorption (UPA) and symmetric bidirectional perfect absorption (PA) at low frequencies. The two functions can be arbitrarily switched by rearranging shunted circuits. Based on the reverberation-ray matrix (RRM) method, an approach is provided to achieve UPA by setting an exceptional point (EP) in the coupled resonant bandgap. By using the transfer matrix method (TMM) and the finite element method (FEM), it is observed that a non-Hermitian pseudo-band forms between two resonant bandgaps, and the EP appears at the bottom of the pseudo-band. In addition, the genetic algorithm is used to accurately and efficiently design the shunted circuits for desired low-frequency UPA and PA. The present work may provide new strategies for vibration suppression and guided waves manipulation in wide potential applications.

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Experimental demonstration of extremely asymmetric flexural wave absorption at the exceptional point

Cited by 14 publications

References 38 publications

Experimental study of a tunable perfect flexural wave absorber with a piezoelectric shunted resonator

Experimental study of a tunable perfect flexural wave absorber with a piezoelectric shunted resonator

Versatile non-Hermitian piezoelectric metamaterial beam with tunable asymmetric reflections

Reconfigurable metamaterial for asymmetric and symmetric elastic wave absorption based on exceptional point in resonant bandgap

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