Transformation Method to Control Shear Horizontal Waves

2015 ◽  
Vol 07 (03) ◽  
pp. 1550049 ◽  
Author(s):  
Yongquan Liu ◽  
Wei Liu ◽  
Bing Li ◽  
Xianyue Su
Keyword(s):  
Elastic Waves ◽  
Acoustic Waves ◽  
Electromagnetic Waves ◽  
Effective Medium Theory ◽  
Transformation Method ◽  
Sh Waves ◽  
Medium Theory ◽  
Out Of Plane ◽  
Linear Transformation Method ◽  
Shear Horizontal

The transformation method is of great interest to control electromagnetic waves and acoustic waves in recent years, but it does not always work to manipulate elastic waves. In this paper, a detailed analysis of controlling the shear horizontal (SH) wave, which is a special form of elastic waves, is presented by employing the transformation method. Two scenarios of setting needed materials are provided, and the equivalence of them is proved theoretically. To reduce the complexity of required material parameters, the case of a changing out-of-plane coordinate is studied. The linear transformation method and the effective medium theory are introduced to control SH waves by using homogeneous and isotropic materials. Moreover, numerical simulations confirm the validity of this approach even in the cases of anisotropic and inhomogeneous background media, which are rarely investigated before. Finally, the multiple transformations method is proposed as a strategy of designing multi-domain and multi-function devices.

scholarly journals A proof that multiple waves propagate in ensemble-averaged particulate materials

2019 ◽  
Vol 475 (2229) ◽  
pp. 20190344 ◽  
Author(s):  
Artur L. Gower ◽  
I. David Abrahams ◽  
William J. Parnell
Keyword(s):  
Acoustic Waves ◽  
Volume Fraction ◽  
Effective Medium Theory ◽  
Effective Medium ◽  
Inhomogeneous Material ◽  
Ensemble Averaging ◽  
Reflection And Transmission ◽  
Medium Theory ◽  
Transmission Coefficients ◽  
Cylindrical Inclusions

Effective medium theory aims to describe a complex inhomogeneous material in terms of a few important macroscopic parameters. To characterize wave propagation through an inhomogeneous material, the most crucial parameter is the effective wavenumber . For this reason, there are many published studies on how to calculate a single effective wavenumber. Here, we present a proof that there does not exist a unique effective wavenumber; instead, there are an infinite number of such (complex) wavenumbers. We show that in most parameter regimes only a small number of these effective wavenumbers make a significant contribution to the wave field. However, to accurately calculate the reflection and transmission coefficients, a large number of the (highly attenuating) effective waves is required. For clarity, we present results for scalar (acoustic) waves for a two-dimensional material filled (over a half-space) with randomly distributed circular cylindrical inclusions. We calculate the effective medium by ensemble averaging over all possible inhomogeneities. The proof is based on the application of the Wiener–Hopf technique and makes no assumption on the wavelength, particle boundary conditions/size or volume fraction. This technique provides a simple formula for the reflection coefficient, which can be explicitly evaluated for monopole scatterers. We compare results with an alternative numerical matching method.

scholarly journals Recent Advances in Non-Traditional Elastic Wave Manipulation by Macroscopic Artificial Structures

2020 ◽  
Vol 10 (2) ◽  
pp. 547 ◽  
Author(s):  
Jeonghoon Park ◽  
Dongwoo Lee ◽  
Junsuk Rho
Keyword(s):  
Elastic Wave ◽  
Elastic Waves ◽  
Acoustic Waves ◽  
Electromagnetic Waves ◽  
Gradient Index ◽  
Bragg Scattering ◽  
Elastic Materials ◽  
Artificial Structures ◽  
Elastic Metamaterials ◽  
Gradient Index Lens

Metamaterials are composed of arrays of subwavelength-sized artificial structures; these architectures give rise to novel characteristics that can be exploited to manipulate electromagnetic waves and acoustic waves. They have been also used to manipulate elastic waves, but such waves have a coupling property, so metamaterials for elastic waves uses a different method than for electromagnetic and acoustic waves. Since researches on this type of metamaterials is sparse, this paper reviews studies that used elastic materials to manipulate elastic waves, and introduces applications using extraordinary characteristics induced by metamaterials. Bragg scattering and local resonances have been exploited to introduce a locally resonant elastic metamaterial, a gradient-index lens, a hyperlens, and elastic cloaking. The principles and applications of metasurfaces that can overcome the disadvantages of bulky elastic metamaterials are discussed.

DISORDERING MECHANISMS OF THE Cu(110) SURFACE

1994 ◽  
Vol 08 (23) ◽  
pp. 3175-3204 ◽  
Author(s):  
J. MERIKOSKI ◽  
H. HÄKKINEN ◽  
M. MANNINEN ◽  
J. TIMONEN ◽  
K. KASKI
Keyword(s):  
Lattice Gas ◽  
Surface Defects ◽  
Effective Medium Theory ◽  
Plane Surface ◽  
Theoretical Work ◽  
Medium Theory ◽  
Recent Theoretical Work ◽  
Out Of Plane ◽  
Surface Vibrations ◽  
Many Body Interactions

We review recent theoretical work on the various disordering mechanisms of the Cu(110) surface. In these studies the properties of the surface, from the onset of enhanced anharmonicity in surface vibrations up to bulk melting point T M , have been studied using molecular dynamics and lattice-gas Monte Carlo methods with many-body interactions derived from the effective medium theory. Well after the onset of enhanced out-of-plane surface vibrations, clustering of surface defects is found to induce a roughening transition at T≈0.81T M , and surface premelting is found to occur at T≈0.97T M . These results suggest, that these transitions can both appear at Cu(110). The general picture of disordering as reported here for Cu(110), is expected to be valid also for other unreconstructed (110) surfaces of fcc metals.

scholarly journals Effective-medium theory of elastic waves in random networks of rods

2012 ◽  
Vol 85 (6) ◽  
Author(s):  
J. I. Katz ◽  
J. J. Hoffman ◽  
M. S. Conradi ◽  
J. G. Miller
Keyword(s):  
Elastic Waves ◽  
Effective Medium Theory ◽  
Effective Medium ◽  
Random Networks ◽  
Medium Theory

scholarly journals On Discovery of the Twelfth and Thirteenth New Nondispersive SH-SAWs in 6 mm Magnetoelectroelastics

Acoustics ◽  
2019 ◽  
Vol 1 (4) ◽  
pp. 749-762
Author(s):  
Zakharenko
Keyword(s):  
Acoustic Waves ◽  
Surface Acoustic Waves ◽  
Normal Component ◽  
Transversely Isotropic ◽  
Coupling Mechanism ◽  
Sh Waves ◽  
Magnetoelectroelastic Materials ◽  
Open Case ◽  
Coupling Mechanisms ◽  
Shear Horizontal

This report acquaints the reader with an extra two new shear-horizontal surface acoustic waves (SH-SAWs). These new SH-SAWs can propagate along the free surface of the transversely isotropic (6 mm) magnetoelectroelastic materials. These (composite) materials can simultaneously possess the piezoelectric, piezomagnetic, and magnetoelectric effects. Some competition among these effects can lead to suitable solutions found for the following three possible coupling mechanisms: eα – hε, eµ – hα, εµ – α2. Here, the mechanically free interface between the solid and a vacuum was considered. This report discovers the twelfth (thirteenth) new SH-SAW for the magnetically closed (electrically open) case and continuity of both the normal component of the electrical (magnetic) displacement and the electrical (magnetic) potential when the coupling mechanism eα – hε (eµ – hα) works. The propagation velocities were obtained in explicit forms that take into account the contribution of the vacuum material parameters. The discovered waves were then graphically studied for the purpose of disclosing the dissipation phenomenon (the propagation velocity becomes imaginary) caused by the coupling with the vacuum properties. The obtained results can be useful for further investigations of interfacial and plate SH-waves, constitution of technical devices, nondestructive testing and evaluation, and application of some gravitational phenomena.

scholarly journals Characterization of Shear Horizontal Waves Using a 1D Laser Doppler Vibrometer

Sensors ◽  
2021 ◽  
Vol 21 (7) ◽  
pp. 2467
Author(s):  
Alaa Elhady ◽  
Eihab M. Abdel-Rahman
Keyword(s):  
Acoustic Waves ◽  
Surface Deformation ◽  
Plane Surface ◽  
Poisson Ratio ◽  
Surface Acoustic Waves ◽  
Laser Doppler Vibrometer ◽  
Element Analysis ◽  
Out Of Plane ◽  
Plane Displacement ◽  
Shear Horizontal

We developed a new technique for the detection of shear horizontal surface acoustic waves (SH-SAW) using a one-dimensional laser-based Doppler vibrometer. It measures the out-of-plane surface deformation at the fingertip of an interdigitated transducer (the boundary of the wave aperture) and uses it to estimate the instantaneous in-plane displacement field given the substrate Poisson ratio. It can also estimate the degree of surface confinement (wave decay rate). The proposed approach was first verified using finite element analysis (FEA) and demonstrated experimentally using a Bleustein–Gulyaev resonator.

Design and assessment of an acoustic ground cloak with layered structure

2015 ◽  
Vol 29 (27) ◽  
pp. 1550191 ◽  
Author(s):  
Jie Xiong ◽  
Tianning Chen ◽  
Xiaopeng Wang ◽  
Jian Zhu
Keyword(s):  
Layered Structure ◽  
Acoustic Waves ◽  
Effective Medium Theory ◽  
Incident Angle ◽  
Multilayered Structure ◽  
Assessment System ◽  
Cosine Similarity ◽  
Acoustic Beam ◽  
Medium Theory ◽  
Transformation Acoustics

In this paper, a two-dimensional acoustic ground cloak with alternating layered structure composed of mercury and water is designed on the basis of transformation acoustics and effective medium theory. The cloak exhibits excellent cloaking performance to hide an object from the detection of acoustic waves. Cosine similarity is proposed to precisely quantize and evaluate the cloaking performance, which turns out to be succinct and effective. Numerical simulations confirm that the cloak could work well in a broad frequency band in which the cloaking performance displays an oscillatory decrease with increasing frequency. In addition, the omnidirectional property, larger incident angle of the acoustic beam has the better cloaking performance, is analyzed. This multilayered structure of cloak may offer an access to fabrication simplicity and experimental demonstration. The concept of cosine similarity may be an enrichment of the assessment system for acoustic cloaks.

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