Identifying elastic wave attenuation bandgaps: Does sweeping the wave vector over the irreducible Brillouin zone boundaries provide the complete picture?

2020 ◽  
Author(s):  
Bhisham Sharma
Keyword(s):  
Elastic Wave ◽  
Brillouin Zone ◽  
Wave Vector ◽  
Wave Attenuation ◽  
Complete Picture

scholarly journals Numerical Modelling and Optimization of Two-Dimensional Phononic Band Gaps in Elastic Metamaterials with Square Inclusions

2021 ◽  
Vol 11 (7) ◽  
pp. 3124
Author(s):  
Alya Alhammadi ◽  
Jin-You Lu ◽  
Mahra Almheiri ◽  
Fatima Alzaabi ◽  
Zineb Matouk ◽  
...  
Keyword(s):  
Elastic Wave ◽  
Tungsten Carbide ◽  
Composite Structure ◽  
Elastic Waves ◽  
Wave Attenuation ◽  
Low Frequency ◽  
Filling Fraction ◽  
Carbide Composite ◽  
Elastic Metamaterials ◽  
Tungsten Carbide Composite

A numerical simulation study on elastic wave propagation of a phononic composite structure consisting of epoxy and tungsten carbide is presented for low-frequency elastic wave attenuation applications. The calculated dispersion curves of the epoxy/tungsten carbide composite show that the propagation of elastic waves is prohibited inside the periodic structure over a frequency range. To achieve a wide bandgap, the elastic composite structure can be optimized by changing its dimensions and arrangement, including size, number, and rotation angle of square inclusions. The simulation results show that increasing the number of inclusions and the filling fraction of the unit cell significantly broaden the phononic bandgap compared to other geometric tunings. Additionally, a nonmonotonic relationship between the bandwidth and filling fraction of the composite was found, and this relationship results from spacing among inclusions and inclusion sizes causing different effects on Bragg scatterings and localized resonances of elastic waves. Moreover, the calculated transmission spectra of the epoxy/tungsten carbide composite structure verify its low-frequency bandgap behavior.

A waveform inversion technique for measuring elastic wave attenuation in cylindrical bars

Geophysics ◽  
1992 ◽  
Vol 57 (6) ◽  
pp. 854-859 ◽  
Author(s):  
Xiao Ming Tang
Keyword(s):  
Elastic Wave ◽  
Wave Attenuation ◽  
Waveform Inversion ◽  
Finite Size ◽  
Low Frequency ◽  
Frequency Range ◽  
Multiple Reflections ◽  
Low Frequencies ◽  
The Time Domain ◽  
Attenuation Values

A new technique for measuring elastic wave attenuation in the frequency range of 10–150 kHz consists of measuring low‐frequency waveforms using two cylindrical bars of the same material but of different lengths. The attenuation is obtained through two steps. In the first, the waveform measured within the shorter bar is propagated to the length of the longer bar, and the distortion of the waveform due to the dispersion effect of the cylindrical waveguide is compensated. The second step is the inversion for the attenuation or Q of the bar material by minimizing the difference between the waveform propagated from the shorter bar and the waveform measured within the longer bar. The waveform inversion is performed in the time domain, and the waveforms can be appropriately truncated to avoid multiple reflections due to the finite size of the (shorter) sample, allowing attenuation to be measured at long wavelengths or low frequencies. The frequency range in which this technique operates fills the gap between the resonant bar measurement (∼10 kHz) and ultrasonic measurement (∼100–1000 kHz). By using the technique, attenuation values in a PVC (a highly attenuative) material and in Sierra White granite were measured in the frequency range of 40–140 kHz. The obtained attenuation values for the two materials are found to be reliable and consistent.

Group Theoretical Analysis of Lattice Vibrations in GaSe Polytypes

1974 ◽  
Vol 52 (24) ◽  
pp. 2454-2458 ◽  
Author(s):  
S. Jandl ◽  
J. L. Brebner
Keyword(s):  
Theoretical Analysis ◽  
Raman Scattering ◽  
Brillouin Zone ◽  
Wave Vector ◽  
Lattice Vibrations ◽  
Group Theoretical Analysis

We present here a group theoretical analysis of the lattice vibrations of the ε and γ polytypes of GaSe for different directions of the wave vector in the Brillouin zone. The effect of the interlayer interactions and the assignment of the modes observed in Raman scattering is discussed.

Elastic wave propagation in metamaterial rods with periodic shunted piezo-patches

2021 ◽  
Vol 263 (2) ◽  
pp. 4303-4311
Author(s):  
Edson J.P. de Miranda ◽  
Edilson D. Nobrega ◽  
Leopoldo P.R. de Oliveira ◽  
José M.C. Dos Santos
Keyword(s):  
Wave Propagation ◽  
Elastic Wave ◽  
Wave Attenuation ◽  
Periodic Structures ◽  
Band Gaps ◽  
Low Frequencies ◽  
Periodic Arrays ◽  
Extended Plane ◽  
Elastic Metamaterials ◽  
Piezoelectric Structures

The wave propagation attenuation in low frequencies by using piezoelectric elastic metamaterials has been developed in recent years. These piezoelectric structures exhibit abnormal properties, different from those found in nature, through the artificial design of the topology or exploring the shunt circuit parameters. In this study, the wave propagation in a 1-D elastic metamaterial rod with periodic arrays of shunted piezo-patches is investigated. This piezoelectric metamaterial rod is capable of filtering the propagation of longitudinal elastic waves over a specified range of frequency, called band gaps. The complex dispersion diagrams are obtained by the extended plane wave expansion (EPWE) and wave finite element (WFE) approaches. The comparison between these methods shows good agreement. The Bragg-type and locally resonant band gaps are opened up. The shunt circuits influence significantly the propagating and the evanescent modes. The results can be used for elastic wave attenuation using piezoelectric periodic structures.

Elastic wave attenuation and velocity of Berea Sandstone measured in the frequency domain

1993 ◽  
Vol 20 (5) ◽  
pp. 391-394 ◽  
Author(s):  
T. J. Shankland ◽  
P. A. Johnson ◽  
T. M. Hopson
Keyword(s):  
Elastic Wave ◽  
Frequency Domain ◽  
Wave Attenuation ◽  
Berea Sandstone

Plate-type elastic metamaterials for low-frequency broadband elastic wave attenuation

Ultrasonics ◽  
2017 ◽  
Vol 73 ◽  
pp. 34-42 ◽  
Author(s):  
Yinggang Li ◽  
Ling Zhu ◽  
Tianning Chen
Keyword(s):  
Elastic Wave ◽  
Wave Attenuation ◽  
Low Frequency ◽  
Elastic Metamaterials ◽  
Plate Type

Elastic wave attenuation in composite laminates with cracks

2005 ◽  
Author(s):  
David Miller ◽  
Santanu Das ◽  
Xu Zhou ◽  
Aditi Chattopadhyay
Keyword(s):  
Elastic Wave ◽  
Composite Laminates ◽  
Wave Attenuation
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