scholarly journals Experimental validation of the band-gap and dispersive bulk modulus behaviour of locally resonant acoustic metamaterials

2013 ◽  
Author(s):  
Matthew Reynolds ◽  
Yan Gao ◽  
Steve Daley
Keyword(s):  
Bulk Modulus ◽  
Band Gap ◽  
Experimental Validation ◽  
Acoustic Metamaterials

Wave propagation in acoustic metamaterials with resonantly shunted cross-shape piezos

2018 ◽  
Vol 29 (13) ◽  
pp. 2744-2753 ◽  
Author(s):  
Shengbing Chen
Keyword(s):  
Wave Propagation ◽  
Band Gap ◽  
Vibration Isolation ◽  
Band Gaps ◽  
Acoustic Metamaterials ◽  
Resonant Frequencies ◽  
Piezoelectric Patch ◽  
Transmission Properties ◽  
Gap Width ◽  
Band Gap Width

Cross-shape piezoelectric patches were originally proposed to improve the band-gap properties of acoustic metamaterials with shunting circuits. The dispersion curves are characterized through the application of finite element method. Also, the theoretical band-gap predictions are verified by simulation results obtained from COMSOL. The investigation results show that the proposed scheme distinguishes itself from the conventional square patches by broader band gaps, whose bandwidth is almost doubled. The inherent capacitance of the piezoelectric patch is strongly related to the boundary conditions, so the local resonant band gap is strongly affected by the shape of piezoelectric patches as well. As a result, the band-gap width and location of metamaterials with different shape patches are rather different, even with the same size patches. Also, negative modulus (NM) and Poisson’s ratio were observed around the resonant frequencies. The transmission properties of finite periods agree well with band-gap predictions. An obvious attenuation zone (AZ) is produced around the band-gap location, in which the wave propagation is decayed strongly. Similarly, the width of AZ of the proposed metamaterial is much larger than that of the conventional one. Hence, the proposed scheme demonstrates more advantages in the application to vibration isolation when compared with the conventional.

scholarly journals Evaluation of uncertainty effects to band gap behavior of circuitry-integrated piezoelectric metamaterial using order-reduced analysis

2018 ◽  
Vol 29 (12) ◽  
pp. 2677-2692 ◽  
Author(s):  
Wangbai Pan ◽  
Guoan Tang ◽  
Jiong Tang
Keyword(s):  
Band Gap ◽  
Parameter Uncertainty ◽  
Good Accuracy ◽  
Integrated System ◽  
Acoustic Metamaterials ◽  
Type Analysis ◽  
Design And Synthesis ◽  
Unit Cells ◽  
Geometry Configuration ◽  
Reduced Modeling

Acoustic metamaterials with unit cells that are integrated with piezoelectric transducer circuitry exhibit interesting band gap behaviors that can be used for wave/vibration manipulation. This research reports the evaluation of uncertainty effects to a typical piezoelectric metamaterial, where uncertainties in geometry/configuration and in circuitry elements are taken into consideration. Monte Carlo–type analysis is performed to assess the band gap features under these uncertainties. In order to facilitate tractable computation in uncertainty analysis, order-reduced modeling of the electro-mechanically integrated system is formulated. The component mode synthesis–based order-reduced modeling increases the computational efficiency significantly while maintaining good accuracy. Results show that the band gap behavior is generally less sensitive to configuration uncertainty but can be greatly affected by circuitry parameter uncertainty. These results can be used to guide the design and synthesis of piezoelectric metamaterials, and the method developed can be applied to the uncertainty quantification of other types of metamaterials.

scholarly journals Novel III-V Nitride Polymorphs in the P42/mnm and Pbca Phases

Materials ◽  
2020 ◽  
Vol 13 (17) ◽  
pp. 3743 ◽  
Author(s):  
Qingyang Fan ◽  
Xin Ai ◽  
Junni Zhou ◽  
Xinhai Yu ◽  
Wei Zhang ◽  
...  
Keyword(s):  
Shear Modulus ◽  
Bulk Modulus ◽  
Band Gap ◽  
Density Functional ◽  
Mechanical Stability ◽  
Elastic Anisotropy ◽  
Wide Band ◽  
Light Emitting ◽  
Ultraviolet Detectors ◽  
Direct Band

In this work, the elastic anisotropy, mechanical stability, and electronic properties for P42/mnm XN (XN = BN, AlN, GaN, and InN) and Pbca XN are researched based on density functional theory. Here, the XN in the P42/mnm and Pbca phases have a mechanic stability and dynamic stability. Compared with the Pnma phase and Pm-3n phase, the P42/mnm and Pbca phases have greater values of bulk modulus and shear modulus. The ratio of the bulk modulus (B), shear modulus (G), and Poisson’s ratio (v) of XN in the P42/mnm and Pbca phases are smaller than those for Pnma XN and Pm-3n XN, and larger than those for c-XN, indicating that Pnma XN and Pm-3n XN are more ductile than P42/mnm XN and Pbca XN, and that c-XN is more brittle than P42/mnm XN and Pbca XN. In addition, in the Pbca phases, XN can be considered a semiconductor material, while in the P42/mnm phase, GaN and InN have direct band-gap, and BN and AlN are indirect wide band gap materials. The novel III-V nitride polymorphs in the P42/mnm and Pbca phases may have great potential for application in visible light detectors, ultraviolet detectors, infrared detectors, and light-emitting diodes.

scholarly journals Two-Dimensional Composite Acoustic Metamaterials of Rectangular Unit Cell from Pentamode to Band Gap

Crystals ◽  
2021 ◽  
Vol 11 (12) ◽  
pp. 1457
Author(s):  
Qi Li ◽  
Ke Wu ◽  
Mingquan Zhang
Keyword(s):  
Wave Propagation ◽  
Acoustic Wave ◽  
Band Gap ◽  
Unit Cell ◽  
The Other ◽  
Two Dimensional ◽  
Acoustic Metamaterials ◽  
Acoustic Wave Propagation ◽  
Theoretical Support ◽  
Unit Cells

Pentamode metamaterials have been receiving an increasing amount of interest due to their water-like properties. In this paper, a two-dimensional composite pentamode metamaterial of rectangular unit cell is proposed. The unit cells can be classified into two groups, one with uniform arms and the other with non-uniform arms. Phononic band structures of the unit cells were calculated to derive their properties. The unit cells can be pentamode metamaterials that permit acoustic wave travelling or have a total band gap that impedes acoustic wave propagation by varying the structures. The influences of geometric parameters and materials of the composed elements on the effective velocities and anisotropy were analyzed. The metamaterials can be used for acoustic wave control under water. Simulations of materials with different unit cells were conducted to verify the calculated properties of the unit cells. The research provides theoretical support for applications of the pentamode metamaterials.

scholarly journals First Principles Study on the Structural, Elastic, Electronic and Optical Properties of Cubic ‘Half-Heusler’ Alloy RuVAs Under Pressure

2020 ◽  
pp. 51-63 ◽  
Keyword(s):  
Optical Properties ◽  
Band Structure ◽  
Bulk Modulus ◽  
Band Gap ◽  
Elastic Constants ◽  
First Principles ◽  
Theoretical Data ◽  
Lattice Parameter ◽  
Electronic Band ◽  
Electronic And Optical Properties

The pressure effect (0 to 40 GPa) on the structural, elastic, electronic, and optical properties of half-metallic compound RuVAs has been investigated employing the DFT based on the first-principles method. The CASTEP computer code is used for this investigation. The calculated lattice parameter show slide deviation from the synthesized and other theoretical data. The normalized lattice parameter and volume are decreased with increasing pressure. The zero pressure elastic constants and also the pressure-dependent elastic constants are positive up to 40 GPa and satisfy the Born stability condition which ensured that the compound RuVAs is stable in nature. At zero pressure, the electronic band gap of 0.159 eV is observed from the band structure calculations which ensured the semimetallic nature of RuVAs. No band gap is observed in the electronic band structure at 40 GPa which indicates the occurrence of phase transition of compound RuVAs at this pressure. We have calculated the value of bulk modulus B, shear modulus G, Young’s modulus E, Pugh ratio B/G, Poisson’s ratio ν and anisotropy factor A of this compound by using the Voigt-Reuss-Hill (VRH) averaging scheme under pressure. The bulk modulus shows a linear response to pressure so that the hardness of this material is increased with increasing pressure. Furthermore, the optical properties such as reflectivity, absorptivity, conductivity, dielectric constant, refractive index, and loss function of RuVAs were evaluated and discussed under pressure up to 40 GPa.

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