Physical constraints on lossy acoustic metamaterials with complex effective properties

2014 ◽  
Vol 135 (4) ◽  
pp. 2223-2223
Author(s):  
Caleb F. Sieck ◽  
Michael R. Haberman ◽  
Andrea Alù
Keyword(s):  
Effective Properties ◽  
Acoustic Metamaterials ◽  
Physical Constraints

scholarly journals Gradient index phononic crystals and metamaterials

Nanophotonics ◽  
2019 ◽  
Vol 8 (5) ◽  
pp. 685-701 ◽  
Author(s):  
Yabin Jin ◽  
Bahram Djafari-Rouhani ◽  
Daniel Torrent
Keyword(s):  
Refractive Index ◽  
Wave Propagation ◽  
Acoustic Waves ◽  
Effective Properties ◽  
Periodic Structures ◽  
Phononic Crystals ◽  
Ray Theory ◽  
Acoustic Metamaterials ◽  
Propagation Of Waves ◽  
At Will

AbstractPhononic crystals and acoustic metamaterials are periodic structures whose effective properties can be tailored at will to achieve extreme control on wave propagation. Their refractive index is obtained from the homogenization of the infinite periodic system, but it is possible to locally change the properties of a finite crystal in such a way that it results in an effective gradient of the refractive index. In such case the propagation of waves can be accurately described by means of ray theory, and different refractive devices can be designed in the framework of wave propagation in inhomogeneous media. In this paper we review the different devices that have been studied for the control of both bulk and guided acoustic waves based on graded phononic crystals.

scholarly journals Shear-mediated contributions to the effective properties of soft acoustic metamaterials including negative index

2015 ◽  
Vol 5 (1) ◽  
Author(s):  
Derek Michael Forrester ◽  
Valerie J. Pinfield
Keyword(s):  
Effective Properties ◽  
Acoustic Properties ◽  
Double Negative ◽  
Acoustic Metamaterials ◽  
Viscous Losses ◽  
Backward Propagation ◽  
Phase Angles ◽  
Lossy Materials ◽  
Selection Of ◽  
Sub Wavelength

Abstract Here we show that, for sub-wavelength particles in a fluid, viscous losses due to shear waves and their influence on neighbouring particles significantly modify the effective acoustic properties and thereby the conditions at which negative acoustic refraction occurs. Building upon earlier single particle scattering work, we adopt a multiple scattering approach to derive the effective properties (density, bulk modulus, wavenumber). We show,through theoretical prediction, the implications for the design of “soft” (ultrasonic) metamaterials based on locally-resonant sub-wavelength porous rubber particles, through selection of particle size and concentration and demonstrate tunability of the negative speed zones by modifying the viscosity of the suspending medium. For these lossy materials with complex effective properties, we confirm the use of phase angles to define the backward propagation condition in preference to “single-” and “double-negative” designations.

Retrieving continuously varying effective properties of non-resonant acoustic metamaterials

2019 ◽  
Vol 12 (5) ◽  
pp. 052008 ◽  
Author(s):  
Dongwoo Lee ◽  
Jungho Mun ◽  
Choonlae Cho ◽  
Namkyoo Park ◽  
Junsuk Rho
Keyword(s):  
Effective Properties ◽  
Acoustic Metamaterials

Applicability of Dynamic Homogenization for Acoustic Metamaterials

2014 ◽  
Author(s):  
Ankit Srivastava ◽  
Sia Nemat-Nasser
Keyword(s):  
Negative Refraction ◽  
Effective Properties ◽  
Dynamic Properties ◽  
Low Frequency ◽  
Bloch Wave ◽  
Acoustic Metamaterials ◽  
Infinite Domain ◽  
True Negative ◽  
Periodic Composite ◽  
Frequency Regime

Dynamic homogenization seeks to define frequency dependent effective properties for heterogeneous composites for the purpose of studying wave propagation in them. These properties can be used to predict and design for metamaterial behavior. However, there is an approximation involved in replacing a heterogeneous composite with its homogenized equivalent. In this paper we propose a quantification to this approximation. By way of explicit examples we show that a comprehensive homogenization scheme proposed in earlier papers is applicable in a finite composite setting and in the low frequency regime. We also show that there exist good arguments for considering the second branch of a locally resonant composite a true negative branch. Furthermore, we note that infinite-domain homogenization is more applicable to finite cases of locally resonant metamaterial composites than it is to 2-phase composites. We also study the effect of the interface location on the applicability of homogenization. The results open intriguing questions regarding the effects of replacing a semi-infinite periodic composite with its Bloch-wave (infinite domain) dynamic properties on such phenomenon as negative refraction.

Method for retrieving effective properties of locally resonant acoustic metamaterials

2007 ◽  
Vol 76 (14) ◽  
Author(s):  
Vladimir Fokin ◽  
Muralidhar Ambati ◽  
Cheng Sun ◽  
Xiang Zhang
Keyword(s):  
Effective Properties ◽  
Acoustic Metamaterials

Bloch-Theory-Based Analysis of Damped Phononic Materials

2011 ◽  
Author(s):  
Michael J. Frazier ◽  
Mahmoud I. Hussein
Keyword(s):  
Band Structure ◽  
Wave Attenuation ◽  
Effective Properties ◽  
The Novel ◽  
Acoustic Metamaterials ◽  
Mass Model ◽  
Acoustic Metamaterial ◽  
Optical Branch ◽  
Lumped Parameter ◽  
Impact Vibration

In this paper, we combine Bloch theory with familiar techniques of structural dynamics to study the effects of energy dissipation (i.e., damping) in an acoustic metamaterial. The formulation we present has the novel feature of incorporating a temporal component to wave attenuation in addition to the standard spatial component. The frequency band structure reflects the metamaterial response to the damping intensity. In the context of a lumped parameter nested mass model, increasing the magnitude of damping is shown to cause the band structure to descend the frequency range and reveal an intriguing phenomenon: branch overtaking. This effect occurs as dissipation causes the optical branch to descend below the acoustical branch. The resulting decrease in the width of the band gap would impact vibration minimization and isolation. We also examine the effective properties of the metamaterial, specifically, the effective mass and effective stiffness, and the conditions for these quantities to become negative. Finally, the aforementioned material results are shown to be related to their finite counterpart. For ease of exposition, we consider a special form of Rayleigh damping in which the damping is proportional to the stiffness. The intrinsic presence of dissipation in acoustic metamaterials and the limited scientific literature addressing damped wave propagation in periodic media in general motivates our present study.

scholarly journals Enhancement of Deep-Subwavelength Band Gaps in Flat Spiral-Based Phononic Metamaterials Using the Trampoline Phenomena

2020 ◽  
Vol 87 (7) ◽  
Author(s):  
Osama R. Bilal ◽  
André Foehr ◽  
Chiara Daraio
Keyword(s):  
Effective Properties ◽  
Band Gaps ◽  
Two Dimensional ◽  
Bragg Scattering ◽  
Acoustic Metamaterials ◽  
Resonance Frequencies ◽  
Unit Cells ◽  
Gap Opening ◽  
Operational Frequency ◽  
Flat Spiral

Abstract Elastic and acoustic metamaterials can sculpt dispersion of waves through resonances. In turn, resonances can give rise to negative effective properties, usually localized around the resonance frequencies, which support band gaps at subwavelength frequencies (i.e., below the Bragg-scattering limit). However, the band gaps width correlates strongly with the resonators’ mass and volume, which limits their functionality in applications. Trampoline phenomena have been numerically and experimentally shown to broaden the operational frequency ranges of two-dimensional, pillar-based metamaterials through perforation. In this work, we demonstrate trampoline phenomena in lightweight and planar lattices consisting of arrays of Archimedean spirals in unit cells. Spiral-based metamaterials have been shown to support different band gap opening mechanisms, namely, Bragg-scattering, local resonances and inertia amplification. Here, we numerically analyze and experimentally realize trampoline phenomena in planar metasurfaces for different lattice tessellations. Finally, we carry out a comparative study between trampoline pillars and spirals and show that trampoline spirals outperform the pillars in lightweight, compactness and operational bandwidth.

Mathematical Model of the Effective Properties of a Fiber Reinforced Composite with a Linearly Graded Transition Zone

2010 ◽  
Vol 38 (4) ◽  
pp. 286-307
Author(s):  
Carey F. Childers
Keyword(s):  
Mathematical Model ◽  
Transition Zone ◽  
Effective Properties ◽  
Local Stress ◽  
Stress And Strain ◽  
Fiber Reinforced ◽  
Strain Fields ◽  
Shear Moduli ◽  
Fiber Reinforced Composite ◽  
Reinforced Composite

Abstract Tires are fabricated using single ply fiber reinforced composite materials, which consist of a set of aligned stiff fibers of steel material embedded in a softer matrix of rubber material. The main goal is to develop a mathematical model to determine the local stress and strain fields for this isotropic fiber and matrix separated by a linearly graded transition zone. This model will then yield expressions for the internal stress and strain fields surrounding a single fiber. The fields will be obtained when radial, axial, and shear loads are applied. The composite is then homogenized to determine its effective mechanical properties—elastic moduli, Poisson ratios, and shear moduli. The model allows for analysis of how composites interact in order to design composites which gain full advantage of their properties.

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