Articoli di riviste: "Acoustic-elastic coupling"

1

Shin, Ye Jeong, Hong Min Seung e Joo Hwan Oh. "Fluid-like elastic metasurface". Applied Physics Letters 122, n. 10 (6 marzo 2023): 101701. http://dx.doi.org/10.1063/5.0139336.

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What makes elastic waves different from other waves is the existence of various wave modes and coupling between these modes. Accordingly, the manipulation of elastic waves suffers from many limitations due to mode coupling, which is an inherent complex physical property of elastic waves. In this study, we propose fluid-like elastic metasurfaces that act as an acoustic (fluid) surface to perfectly eliminate mode coupling. Because longitudinal and shear waves are decoupled, only reflected longitudinal (or shear) waves exist when longitudinal (or shear) waves are incident. Using a strip-type unit cell, elastic metasurfaces mimicking acoustic hard-wall and soft-wall were designed and realized. In addition, numerical analysis and experiments were conducted to prove the validity of the designed unit cells. This study presents a more versatile metasurface by solving the mode coupling of solid elastic waves. In addition, two types of designed fluid-like metasurfaces are expected to be utilized in further studies considering the opposite phase shift characteristic.

2

Chaplain, Gregory J., Dan Moore, Ian Hooper, Alastair Hibbins, John Sambles e Timothy Starkey. "Beyond-nearest-neighbour metamaterials". Journal of the Acoustical Society of America 154, n. 4_supplement (1 ottobre 2023): A156. http://dx.doi.org/10.1121/10.0023108.

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Engineering the dispersion of acoustic or elastic waves using coupling terms that spatially reach beyond the immediate local environment, or unit cell, is an “emerging topic” in Metamaterial design. In this talk, we present experimental studies in acoustic and elastic systems that realize beyond-nearest-neighbour coupling to introduce dispersion relations with extrema within the first Brilloun Zone. In acoustics, we use mixed waveguide-surfacewave coupling, while in elasticity we develop an elastic scaffold (made from meccano) with reconfigurable coupling elements and demonstrate the effects of structural symmetries on these exotic dispersion relations. Applications to enhanced energy harvesting structures are presented by leveraging zero-group-velocity modes.

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Gao, Longfei, e David Keyes. "Explicit coupling of acoustic and elastic wave propagation in finite-difference simulations". GEOPHYSICS 85, n. 5 (1 settembre 2020): T293—T308. http://dx.doi.org/10.1190/geo2019-0566.1.

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We present a mechanism to explicitly couple the finite-difference discretizations of 2D acoustic and isotropic elastic-wave systems that are separated by straight interfaces. Such coupled simulations allow for the application of the elastic model to geological regions that are of special interest for seismic exploration studies (e.g., the areas surrounding salt bodies), with the computationally more tractable acoustic model still being applied in the background regions. Specifically, the acoustic wave system is expressed in terms of velocity and pressure while the elastic wave system is expressed in terms of velocity and stress. Both systems are posed in first-order forms and are discretized on staggered grids. Special variants of the standard finite-difference operators, namely, operators that possess the summation-by-parts property, are used for the approximation of spatial derivatives. Penalty terms, which are also referred to as the simultaneous approximation terms, are designed to weakly impose the elastic-acoustic interface conditions in the finite-difference discretizations and couple the elastic and acoustic wave simulations together. With the presented mechanism, we are able to perform the coupled elastic-acoustic wave simulations stably and accurately. Moreover, it is shown that the energy-conserving property in the continuous systems can be preserved in the discretized systems with carefully designed penalty terms.

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Cui, Huaifeng, Rufu Hu e Nan Chen. "Modelling and analysis of acoustic field in a rectangular enclosure bounded by elastic plates under the excitation of different point force". Journal of Low Frequency Noise, Vibration and Active Control 36, n. 1 (marzo 2017): 43–55. http://dx.doi.org/10.1177/0263092317693488.

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The coupled acoustic field of fully elastic plate model is described by the modal analysis method. The acoustic potential energy resonance peaks of the fully elastic plate model are significantly more than that of the one elastic plate model due to the influence of the vibration of multi elastic plates. The acoustic field characteristics of the fully elastic plate model are analyzed when the primary excitation source is applied on the different elastic plates. The results show that the coupled acoustic field of the fully elastic plate model is dominated by the structural mode of the elastic plate with primary excitation, and the acoustic mode of the enclosure, and the structural-acoustic coupling between the plate and the enclosure; the structure modes of the other elastic plates have less effects on the acoustic field in the enclosure except the first ones of them.

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Dong, Kaiyuan, Yiwen Lv, Peng Wang, Wei Cheng e Han Li. "Acoustic properties of underwater acoustic metamaterials based on multi-physical field coupling model". Journal of Physics: Conference Series 2713, n. 1 (1 febbraio 2024): 012006. http://dx.doi.org/10.1088/1742-6596/2713/1/012006.

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Abstract In this paper, according to the internal structure of underwater acoustic metamaterial, a multi-physical field coupling model of underwater acoustic metamaterial is established by using finite element analysis. Based on the model, the influence of typical underwater acoustic metamaterial structure and material parameters on sound absorption performance is studied. The results show that increasing the height or radius of the local resonance mass unit in the metamaterial is beneficial to improve the low frequency sound absorption performance. With the increase of the distance between mass elements and the thickness of elastic material, the acoustic absorption performance increases first and then decreases. Increasing the elastic modulus of elastic material of the local resonance unit or matrix will lead to the decrease of low frequency sound absorption performance of the material and the improvement of high frequency sound absorption performance. Increasing the loss factor of elastic material of the local resonance unit or matrix material can broaden the sound absorption band. These rules can provide guidance for the design of underwater acoustic metamaterials.

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Norris, Andrew N., e Douglas A. Rebinsky. "Acoustic coupling to membrane waves on elastic shells". Journal of the Acoustical Society of America 95, n. 4 (aprile 1994): 1809–29. http://dx.doi.org/10.1121/1.408688.

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Yoon, Gil Ho. "Unified Analysis with Mixed Finite Element Formulation for Acoustic-Porous-Structure Multiphysics System". Journal of Computational Acoustics 23, n. 01 (16 febbraio 2015): 1550002. http://dx.doi.org/10.1142/s0218396x15500022.

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This research aims to develop a novel unified analysis method for an acoustic-porous-structure multiphysics interaction system when the porous medium is modeled by the empirical Delany–Bazley formulation. Multiphysics analysis of acoustic structure interaction is commonly performed by solving the linear elasticity and Helmholtz equations separately and enforcing a mutual coupling boundary condition. If the pressure attenuation from a porous material is additionally considered, the multiphysics analysis becomes highly intricate, because three different media (acoustic, porous, and elastic structures) with different governing equations and interaction boundary conditions should be properly formulated. To overcome this difficulty, this paper proposes the application of a novel mixed formulation to consider the mutual coupling effects among the acoustic, fibrous (porous), and elastic structure media. By combining the mixed finite element formulation with the Delany–Bazley formulation, a multiphysics simulation of sound propagation considering the coupling effects among the three media can be easily conducted. To show the validity of the present unified approach, several benchmark problems are considered.

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Di Bartolo, Leandro, Rosário Romão Manhisse e Cleberson Dors. "Efficient acoustic-elastic FD coupling method for anisotropic media". Journal of Applied Geophysics 174 (marzo 2020): 103934. http://dx.doi.org/10.1016/j.jappgeo.2019.103934.

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Hsiao, Fu-Li, Ying-Pin Tsai, Wei-Shan Chang, Chien-Chang Chiu, Bor-Shyh Lin e Chi-Tsung Chiang. "Photo-Elastic Enhanced Optomechanic One Dimensional Phoxonic Fishbone Nanobeam". Crystals 12, n. 7 (23 giugno 2022): 890. http://dx.doi.org/10.3390/cryst12070890.

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We investigated the strength of acousto-optical (AO) interaction in one-dimensional fishbone silicon nanobeam computationally. The structure can generate phononic and photonic band gaps simultaneously. We use defect cavity optical mode and slow light mode to interact with acoustic defect modes. The AO coupling rates are obtained by adding the optical frequency shifts, which result from photo-elastic effect and moving-boundary effect disturbances. The AO coupling rates are strongly dependent on the overlap of acoustic and optical mode distribution. The strength of AO interaction can be enhanced by choosing certain acoustic defect modes that are formed by the stretching of wings and that overlap significantly with optical fields.

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MAR-OR, ASSAF, e DAN GIVOLI. "A FINITE ELEMENT STRUCTURAL-ACOUSTIC MODEL OF COUPLED MEMBRANES". Journal of Computational Acoustics 12, n. 04 (dicembre 2004): 605–18. http://dx.doi.org/10.1142/s0218396x04002407.

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A simple model displaying structural-acoustic behavior is considered. The model comprises of two parallel infinitely-long flat membranes lying on elastic foundations and the acoustic medium separating them. The structural-acoustic coupling manifests itself in that a vibrational excitation of one of the membranes triggers vibrations in the other. The governing equations are stated, and the associated finite element formulation is constructed. The model is then analyzed numerically and its vibrational properties are investigated. The proposed model is especially simple, being two-dimensional and involving a small number of parameters, but at the same time it brings to light some important features associated with structural-acoustic coupling. Therefore it may serve as a benchmark for evaluating structural-acoustic numerical schemes and as an educational tool for studying structural-acoustic coupling in a simple context.

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Jiao, Ren Qiang, Jian Run Zhang e Dong Lu. "Research on Acoustic Radiation Characteristic for Cylindrical Structure with Elastic Plate Cap in Mid-Frequency Region". Key Engineering Materials 656-657 (luglio 2015): 706–11. http://dx.doi.org/10.4028/www.scientific.net/kem.656-657.706.

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An advanced method named hybrid FE-SEA method was introduced to study the acoustic radiation characteristic for cylindrical structure with elastic plate cap in medium-frequency region. This method consists of the finite element method (FEM) for low-frequency region and the statistical energy analysis (SEA) for high-frequency region, which can be employed to deal with the problem of acoustic radiation result from model coupling of elastic connection effectively. According to the FE-SEA theory, a hybrid model of cylindrical structure with elastic plate cap was built to validated whether the hybrid method was feasible to calculate the acoustic radiation in the medium-frequency region. Moreover, the acoustic radiation characteristic of such model under the single point force excitation was studied. The result of numerical calculation agreed well with that of experiment, which validated the accuracy and validity of the hybrid FE-SEA method in solving the medium-frequency acoustic radiation of the cylindrical structure with elastic plate cap.

12

Du, Xiaofei, Xin Liao, Qidi Fu e Chaoyong Zong. "Vibro-Acoustic Analysis of Rectangular Plate-Cavity Parallelepiped Coupling System Embedded with 2D Acoustic Black Holes". Applied Sciences 12, n. 9 (19 aprile 2022): 4097. http://dx.doi.org/10.3390/app12094097.

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An acoustic black hole (ABH) has the ability to concentrate and manipulate flexural waves, which can be used for structural vibration suppression and noise attenuation. In this paper, a 2D ABH rectangular plate is designed and a 2D ABH plate-cavity coupling system is constructed using the 2D ABH plate and five rectangular elastic plates of uniform thickness. Series of vibro-acoustic FEM models of the plate-cavity parallelepiped coupling system embedded with 2D ABHs are established, and the vibro-acoustic coupling simulation is conducted to analyze the effects of ABHs on the coupling modes, vibro-acoustic coupling characteristics, and mechanism of ABHs and the damping layer. It is shown that at most frequencies in the range of 3600~5000 Hz, the damping 2D ABH plate-cavity parallelepiped coupling system can significantly suppress the sound pressure and greatly reduce the peak values. It is also found that the significant reduction of the participation factor of the acoustic modes within the 100th order is the main mechanism for the obvious suppression of the sound pressure in the damping ABH plate-cavity coupling system at 3701 Hz. Finally, an experimental platform of vibro-acoustic measurement of the 2D ABH coupling system is constructed, and the accuracy of the vibro-acoustic FEM models of the 2D ABH coupling systems established in this paper and the numerical simulation calculation are verified by the vibro-acoustic measurement experiment.

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Jin, Zhong Kun, e Tong Qing Wang. "Calculation on Acoustic Scattering of Viscoelastic Layer Coupling with Elastic Shell". Applied Mechanics and Materials 248 (dicembre 2012): 107–13. http://dx.doi.org/10.4028/www.scientific.net/amm.248.107.

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This paper is devoted to numerical research on coupling between elastic spherical shell and the coated viscoelastic layer as well as the scattering of incident plane wave by the double-layer spherical shell. The scattering sound field is solved based on impedance boundary condition by boundary element method (BEM). Dynamic finite element method (FEM) is used to numerically simulate the acoustic impedance boundary condition which involved in the coupled spherical shell. Impedance distribution for elastic spherical shell and elastic spherical shell coated viscoelastic layer is calculated and its effect on the target strength (TS) is discussed finally.

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Zhou, Qi Zheng, De Shi Wang e Shu Yang. "Acoustic and Vibration Characteristics of Finite Cylindrical Shell-Circular Plate Based on Lagrange Equations". Applied Mechanics and Materials 302 (febbraio 2013): 401–5. http://dx.doi.org/10.4028/www.scientific.net/amm.302.401.

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An analysis based on Lagrange equations was presented for acoustic and vibration characteristics of finite cylindrical shell-circular plate underwater. The boundary conditions and coupling conditions between the shell and plate expressed using springs, the model of finite shell with circular plate was set up. Considering the elastic potential energy in springs and the work due to fluid loading, the vibro-acoustic equations of finite cylinder with circular plate under excitation were established by Lagrange equations. The influences of boundary conditions and coupling conditions to the acoustic and vibration characteristics were researched. The results show that . The results could be used to control the underwater vehicle’s vibration and acoustic radiation.

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Park, Jeonghoon, Dongwoo Lee e Junsuk Rho. "Recent Advances in Non-Traditional Elastic Wave Manipulation by Macroscopic Artificial Structures". Applied Sciences 10, n. 2 (11 gennaio 2020): 547. http://dx.doi.org/10.3390/app10020547.

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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.

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Metiri, W., F. Hadjoub, A. Doghmane e Z. Hadjoub. "Coupling liquids acoustic velocity effects on elastic metallic bioglass properties". Physics Procedia 2, n. 3 (novembre 2009): 1421–24. http://dx.doi.org/10.1016/j.phpro.2009.11.111.

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POBLET-PUIG, J., e A. RODRÍGUEZ-FERRAN. "THE BLOCK GAUSS–SEIDEL METHOD IN SOUND TRANSMISSION PROBLEMS". Journal of Computational Acoustics 18, n. 01 (marzo 2010): 13–30. http://dx.doi.org/10.1142/s0218396x10004036.

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Sound transmission through partitions can be modeled as an acoustic fluid–elastic structure interaction problem. The block Gauss–Seidel iterative method is used in order to solve the finite element linear system of equations. The blocks are defined, respecting the fluid and structural domains. The convergence criterion is analyzed and interpreted in physical terms by means of simple one-dimensional problems. This analysis highlights the negative influence on the convergence of a strong degree of coupling between the acoustic domains and the structure. A selective coupling strategy has been developed and applied to problems with strong coupling (e.g. double walls).

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Liu, Jinpeng, Zheng Zhu, Yongqiang Ji, Ziyang Chen, Chao Zhang e Dejiang Shang. "Prediction of Sound Scattering from Deep-Sea Targets Based on Equivalence of Directional Point Sources". Applied Sciences 11, n. 11 (2 giugno 2021): 5160. http://dx.doi.org/10.3390/app11115160.

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A fast prediction method is proposed for calculating the sound scattering of targets in the deep-sea acoustic channel by equating the sound scattering field of a complex elastic target to the acoustic field excited by a directional point source. In deep-sea conditions, the effects of the sea surface on the impedance characteristics of the elastic target surface can be ignored. Through the finite element simulation of the acoustic scattering of the target in the free field, the sound scattering field is equated to the radiation field of a directional point source. Subsequently, the point source is placed in the channel, and the acoustic ray method is used to calculate the distribution of the scattering field. On the basis of theoretical modelling, the method of obtaining the directional point source and the influence of the sea surface on the impedance of the scattering field are analysed. Subsequently, the proposed method is compared with the finite element method in terms of computational efficiency. The result shows that the method considers the multiple complex coupling effects between the elastic structure and marine environment. The influence of the boundary is approximately negligible when the distance from the ocean boundary to the elastic structure is equal to the wavelength. The method only performs finite element coupling calculation in the free field; the amount of mesh size is greatly reduced and the calculation efficiency is significantly improved when compared with the finite element calculation in the entire channel, the. The calculation time in the example can be reduced by more than one order of magnitude. This method organically combines the near-field calculation with acoustic ray theory and it can realise the rapid calculation of the large-scale acoustic scattering field in complex marine environments.

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Wang, Xin-Zhong, Dong Wang, Zhe-Wei Wang, Xiao-Juan Yin, Xue-Jun Zhou, Zhang Ru, An-Lin Zhang, Gan Feng e Ren Li. "Mechanical properties and acoustic emission characteristics of granite under thermo-hydro-mechanical coupling". Thermal Science 25, n. 6 Part B (2021): 4585–96. http://dx.doi.org/10.2298/tsci2106585w.

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Exploring the mechanical properties and thermal cracking characteristics of rock under thermo-hydro-mechanical coupling in detail is of great importance for the safe excavation and stability of deep rock engineering. The mechanical properties and thermal cracking characteristics of granite under burial depths of 1000 m (confining pressure of 25 MPa) and 1600 m (confining pressure of 40 MPa) at a temperature of 110?C and a pore water pressure of 10 MPa were studied. The results show that the elastic modulus decreases with increasing temperature under a confining pressure of 25 MPa, whereas under a confining pressure of 40 MPa, the elastic modulus increases with increasing temperature. As the pore water pressure increases, the elastic modulus decreases slightly. Poisson?s ratio increas?es with increasing temperature below 40?C but decreases from 50-110?C. Pois?son?s ratio increases as pore water pressure increases. During the heating process, acoustic emission activity is first detected at 30-40?C and is relatively stable from 40-90?C. The acoustic emission activity increases sharply at 90-110?C, and the thermal cracking threshold of granite under thermo-hydro-mechanical coupling is approximately 95?C.

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Shi, Dongyan, Wenhui Ren, Hong Zhang, Gai Liu e Qingshan Wang. "Vibro-acoustic coupling characteristics of orthotropic L-shaped plate–cavity coupling system". Journal of Low Frequency Noise, Vibration and Active Control 39, n. 4 (1 luglio 2019): 1102–26. http://dx.doi.org/10.1177/1461348419860630.

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The research object of this paper is the L-shaped plate–cavity coupling system established by a cuboid acoustic cavity with rigid-wall or impedance-wall and L-shaped plate with numerous elastic boundary conditions in view of the Fourier series method. The main research content of this paper is the vibro-acoustic coupling characteristics. In this paper, the displacements admissible functions of the L-shaped plate are generally set as the sum of two cosines’ product and two polynomials. Sound pressure admissible functions of the cuboid acoustic cavity can be considered as the sum of three cosines’ product and six polynomials. The discontinuity of coupling system at all boundaries in the overall solution domain is overcome in this way. Through the energy principle and the Rayleigh-Ritz technology, it can be got that the solving matrix equation of the L-shaped plate-cavity coupling system. Based on verifying the great numerical characteristics of the L-shaped plate–cavity coupling model, they obtained both the frequency analysis and the displacement or sound pressure response analysis under the excitation, including a unit simple harmonic force or a unit monopole source. The advantages of this method are parameterization and versatility. In addition, some new achievements have been shown, based on various materials, boundary conditions, thicknesses, and orthotropic degrees, which may become the foundation for the future research.

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Rebinsky, Douglas A., e Andrew N. Norris. "Benchmarking an acoustic coupling theory for elastic shells of arbitrary shape". Journal of the Acoustical Society of America 98, n. 4 (ottobre 1995): 2368–71. http://dx.doi.org/10.1121/1.413284.

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Čermák, Petr, Astrid Schneidewind, Benqiong Liu, Michael Marek Koza, Christian Franz, Rudolf Schönmann, Oleg Sobolev e Christian Pfleiderer. "Magnetoelastic hybrid excitations in CeAuAl3". Proceedings of the National Academy of Sciences 116, n. 14 (20 marzo 2019): 6695–700. http://dx.doi.org/10.1073/pnas.1819664116.

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Nearly a century of research has established the Born–Oppenheimer approximation as a cornerstone of condensed-matter systems, stating that the motion of the atomic nuclei and electrons may be treated separately. Interactions beyond the Born–Oppenheimer approximation are at the heart of magneto-elastic functionalities and instabilities. We report comprehensive neutron spectroscopy and ab initio phonon calculations of the coupling between phonons, CEF-split localized 4f electron states, and conduction electrons in the paramagnetic regime ofCeAuAl3, an archetypal Kondo lattice compound. We identify two distinct magneto-elastic hybrid excitations that form even though all coupling constants are small. First, we find a CEF–phonon bound state reminiscent of the vibronic bound state (VBS) observed in other materials. However, in contrast to an abundance of optical phonons, so far believed to be essential for a VBS, the VBS inCeAuAl3arises from a comparatively low density of states of acoustic phonons. Second, we find a pronounced anticrossing of the CEF excitations with acoustic phonons at zero magnetic field not observed before. Remarkably, both magneto-elastic excitations are well developed despite considerable damping of the CEFs that arises dominantly by the conduction electrons. Taking together the weak coupling with the simultaneous existence of a distinct VBS and anticrossing in the same material in the presence of damping suggests strongly that similarly well-developed magneto-elastic hybrid excitations must be abundant in a wide range of materials. In turn, our study of the excitation spectra ofCeAuAl3identifies a tractable point of reference in the search for magneto-elastic functionalities and instabilities.

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Viswanathan, K. S. "Elastic and gyrotropic anomalies and acoustic activity in lead germanate". Canadian Journal of Physics 72, n. 9-10 (1 settembre 1994): 568–73. http://dx.doi.org/10.1139/p94-072.

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The paper discusses elastic and gyrotropic anomalies as well as the acoustic activity of lead germanate during the phase transition from the space group C3h to C3. Expressions are derived for all the anomalies of the elastic constants, and relations among them have been established. We show that the elastic constants C11, C33, C12, and C13 suffer a dip at the transition temperature, in agreement with experimental results. Several invariants involving the order parameter, strain variables, and their derivatives are constructed and from these the contribution to the coupling energy of the gyrotropic energy has been calculated. Expressions are given for the anomalies of the various gyrotropic constants. We show that the system will exhibit anomalies in acoustic activity in the low symmetry phase, and an expression for the polarization angle has been obtained.

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BU, GANG, DAUMANTAS CIPLYS, MICHAEL S. SHUR, LEO J. SCHOWALTER, SANDRA B. SCHUJMAN e REMIS GASKA. "LEAKY SURFACE ACOUSTIC WAVES IN SINGLE-CRYSTAL AlN SUBSTRATE". International Journal of High Speed Electronics and Systems 14, n. 03 (settembre 2004): 837–46. http://dx.doi.org/10.1142/s0129156404002922.

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We report on the velocity V and the electromechanical coupling coefficient K2 of the first and the second leaky surface acoustic waves in various propagation directions in the a-plane AlN single-crystal. For c-propagation direction, the second leaky wave exhibited the velocity of 11016 m/s and K2 of 0.45%. For this direction, the temperature coefficient of frequency was found to be -30 ppm/°C. A near match of the velocities of the plane and leaky waves in the a-plane AlN allowed us to establish analytical relationships between the piezoelectric and elastic constants. A full set of elastic and piezoelectric constants of AlN has been evaluated by fitting the measured and calculated dependencies of velocities and electromechanical coupling coefficients on the propagation direction for both Rayleigh and leaky waves.

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Beldi, M., e Z. Lamia. "Calculation of Coupled Modes for Vibro-Acoustic Problems". Advanced Materials Research 488-489 (marzo 2012): 1691–96. http://dx.doi.org/10.4028/www.scientific.net/amr.488-489.1691.

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A new numerical method for the study of elasto-acoustic structures coupled with fluid-filled cavities has been developed. This method essentially consists of solving the eigenvalue problem for the determination of elasto-acoustic modes. The Numerical methods commonly used for its resolution is based on the mass coupling. However, this approach requires for it is resolution the inversion of a singular matrix, "the stiffness matrix of the fluid". We then propose a new numerical method based on stiffness coupling by using modal superposition techniques through a change of variable which shows a symmetric and regular problem in terms of displacement of the elastic structure and in terms of fluid pressure in the cavity.

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Soares, D., e L. Godinho. "An Overview of Recent Advances in the Iterative Analysis of Coupled Models for Wave Propagation". Journal of Applied Mathematics 2014 (2014): 1–21. http://dx.doi.org/10.1155/2014/426283.

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Wave propagation problems can be solved using a variety of methods. However, in many cases, the joint use of different numerical procedures to model different parts of the problem may be advisable and strategies to perform the coupling between them must be developed. Many works have been published on this subject, addressing the case of electromagnetic, acoustic, or elastic waves and making use of different strategies to perform this coupling. Both direct and iterative approaches can be used, and they may exhibit specific advantages and disadvantages. This work focuses on the use of iterative coupling schemes for the analysis of wave propagation problems, presenting an overview of the application of iterative procedures to perform the coupling between different methods. Both frequency- and time-domain analyses are addressed, and problems involving acoustic, mechanical, and electromagnetic wave propagation problems are illustrated.

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Li, Hong Qiu, e Guo Ping Chen. "Sound Transmission in Dual-Coupling System of Elastic Plate and Acoustic Cavity Based on Modal Superposition Method". Applied Mechanics and Materials 475-476 (dicembre 2013): 1474–78. http://dx.doi.org/10.4028/www.scientific.net/amm.475-476.1474.

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This paper presents a study on the dual-coupling characteristics between elastic plate and acoustic cavity. Modal superposition method was employed to analyze sound transmission in the plate-cavity-plate system and cavity-plate-cavity system. Impedance and mobility methods were also adopted which were easy to investigate the characteristics between the structural and acoustic systems. The expression of sound transmission between plate-cavity-plate system and cavity-plate-cavity system were given.

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Goldsberry, Benjamin M., Samuel P. Wallen e Michael R. Haberman. "Nonreciprocal acoustic scattering from an elastic plate with spatiotemporally modulated material properties". Journal of the Acoustical Society of America 151, n. 4 (aprile 2022): A156. http://dx.doi.org/10.1121/10.0010958.

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Acoustic and elastic metamaterials with space- and time-dependent material properties have received great attention recently as a means to realize nonreciprocal wave propagation. The nonreciprocal behavior of propagating waves in a spatiotemporally modulated infinite medium is usually characterized by directional bandgaps present in the frequency-wavenumber spectrum. However, less attention has been given to acoustic scattering from spatiotemporally modulated media. In this work, we consider nonreciprocal reflection and transmission from a spatiotemporally modulated, infinite elastic plate excited by a plane wave at oblique incidence. A semi-analytical approach is developed that considers the coupling between the acoustic waves and the displacement of the plate. The reflection and transmission response of the plate for each generated frequency harmonic as a function of the incident angle are reported. Finally, we find conditions on the modulation parameters that yield a large degree of nonreciprocity. The present analysis leads to potential applications in acoustic communications, such as directional wave sensing.

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Shi, Ao, Bo Lu, Dangguo Yang, Xiansheng Wang, Junqiang Wu e Fangqi Zhou. "Study on model design and dynamic similitude relations of vibro-acoustic experiment for elastic cavity". Modern Physics Letters B 32, n. 12n13 (10 maggio 2018): 1840047. http://dx.doi.org/10.1142/s021798491840047x.

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Coupling between aero-acoustic noise and structural vibration under high-speed open cavity flow-induced oscillation may bring about severe random vibration of the structure, and even cause structure to fatigue destruction, which threatens the flight safety. Carrying out the research on vibro-acoustic experiments of scaled down model is an effective means to clarify the effects of high-intensity noise of cavity on structural vibration. Therefore, in allusion to the vibro-acoustic experiments of cavity in wind tunnel, taking typical elastic cavity as the research object, dimensional analysis and finite element method were adopted to establish the similitude relations of structural inherent characteristics and dynamics for distorted model, and verifying the proposed similitude relations by means of experiments and numerical simulation. Research shows that, according to the analysis of scale-down model, the established similitude relations can accurately simulate the structural dynamic characteristics of actual model, which provides theoretic guidance for structural design and vibro-acoustic experiments of scaled down elastic cavity model.

30

Shepard, W. S., K. A. Cunefare e J. H. Ginsberg. "Identifying Critical Elastic Scales in Structural-Acoustic Models". Journal of Vibration and Acoustics 120, n. 2 (1 aprile 1998): 455–60. http://dx.doi.org/10.1115/1.2893851.

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The level of detail required for accurate structural acoustic modeling of fluid loaded structures remains an issue of significant debate. Analytical solutions are rarely available, and discrete numerical solutions are typically too complex for ready extraction of physical understanding. In addition, numerical techniques introduce their own explicit scales through the minimum mesh dimension. However, the wavenumber based formulation of the surface variational principle describes the surface pressure and displacement as a comparatively small set of interacting waves. Coupling the SVP with distributed methods of representing structural attachment features provides a means to introduce, control, and investigate features of differing scales. We present here a technique for assessing the critical resolution scales for a fluid loaded two-dimensional plate. For feature attachments, we consider a line-mass elastically suspended by a line-spring from the wetted plate. We then use a spatial expansion for the elastic attachment to the wetted plate. The excitation applied to the plate is taken as a concentrated harmonic force. With the excitation held fixed, the influence of the scale of the feature spatial representation on the radiated power is assessed.

31

Bilal, Osama R., André Foehr e Chiara Daraio. "Bistable metamaterial for switching and cascading elastic vibrations". Proceedings of the National Academy of Sciences 114, n. 18 (17 aprile 2017): 4603–6. http://dx.doi.org/10.1073/pnas.1618314114.

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The realization of acoustic devices analogous to electronic systems, like diodes, transistors, and logic elements, suggests the potential use of elastic vibrations (i.e., phonons) in information processing, for example, in advanced computational systems, smart actuators, and programmable materials. Previous experimental realizations of acoustic diodes and mechanical switches have used nonlinearities to break transmission symmetry. However, existing solutions require operation at different frequencies or involve signal conversion in the electronic or optical domains. Here, we show an experimental realization of a phononic transistor-like device using geometric nonlinearities to switch and amplify elastic vibrations, via magnetic coupling, operating at a single frequency. By cascading this device in a tunable mechanical circuit board, we realize the complete set of mechanical logic elements and interconnect selected ones to execute simple calculations.

32

Brunnhuber, Rainer, Barbara Kaltenbacher e Petronela Radu. "Relaxation of regularity for the Westervelt equation by nonlinear damping with applications in acoustic-acoustic and elastic-acoustic coupling". Evolution Equations & Control Theory 3, n. 4 (2014): 595–626. http://dx.doi.org/10.3934/eect.2014.3.595.

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Warszawski, A., D. Soares e W. J. Mansur. "A FEM–BEM coupling procedure to model the propagation of interacting acoustic–acoustic/acoustic–elastic waves through axisymmetric media". Computer Methods in Applied Mechanics and Engineering 197, n. 45-48 (agosto 2008): 3828–35. http://dx.doi.org/10.1016/j.cma.2008.03.005.

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Pei, Xi, Min Xu e Dong Guo. "Aeroelastic-Acoustics Numerical Simulation Research". Applied Mechanics and Materials 226-228 (novembre 2012): 500–504. http://dx.doi.org/10.4028/www.scientific.net/amm.226-228.500.

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The generation of aerodynamic noise of aircraft in flight is due to dynamical system and aerodynamic .The response of aircraft subjected to High acoustic loads and aerodynamic loads can produce fatigue and damage. In this paper a new Aeroelastic- Acoustics which adds acoustic loads in aeroelastic is presented. The emphasis of the study is the discipline of displacement and load of the flexible structure under the unsteady aerodynamic, inertial, elastic and aero-acoustic. The CFD/CSD/CAA coupling is used to simulate rockets cabin. Sound generated by a rocker is predicted numerically from a Large Eddy simulation (LES) of unsteady flow field. The Lighthill acoustic analogy is used to model the propagation of sound. The structural response of rocket cabin was given. The boundary-layer transition on the pressure side of the cabin is visualized, by plotting to better illustrate the essential interaction between fluctuating pressure and structure.CFD/CSD/CAA coupling compute method is validated in low and middle frequency.

35

Goldsberry, Benjamin M., Craig W. Broadman, Christina J. Naify e Michael R. Haberman. "Exact radiation boundary conditions to determine the complex wavenumber of an underwater acoustic leaky wave antenna". JASA Express Letters 3, n. 3 (febbraio 2023): 035601. http://dx.doi.org/10.1121/10.0017486.

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Underwater elastic leaky wave antennas (LWAs) steer acoustic energy as a function of frequency by exploiting fluid-solid coupling. LWAs present a modeling challenge due to complex radiation impedance on the waveguide surface that leads to changes in dynamic response. This work presents an approach to model underwater LWAs that considers an elastic unit cell surrounded by a fluid domain and includes a radiation boundary condition to simulate an open boundary. The model solves an eigenvalue problem for the complex-valued wavenumber given a specified frequency, forming an accurate representation for the free response of an elastic LWA in an underwater environment.

36

Gupta, A. K., S. Srivastava e K. B. Thapa. "Temperature Dependent Ultrasonic Study in Scandium Antimonide Semiconductor". E-Journal of Chemistry 9, n. 3 (2012): 1400–1406. http://dx.doi.org/10.1155/2012/130434.

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In this paper analysis of wave propagation of elastic wave in scandium antimonide semiconductor was investigated. In scandium antimonide semiconductor, NaCl structure was found. Ultrasonic properties like ultrasonic attenuation, sound velocities, acoustic coupling constants, and thermal relaxation time have been investigated in cubic scandium antimonide semiconductor. Second and third order elastic constant have been computed for the evaluation of above said ultrasonic properties. Second and third elastic constant was studied at the various temperatures. Longitudinal and shear velocity was calculated by using the elastic constant. Longitudinal and shear velocity increase with increase the temperature. Ultrasonic attenuation either from longitudinal or shear wave propagation in cubic materials increase with increase the temperature.

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Sayed Ahmed, Moustafa, Mehdi Ghommem e Shima Shahab. "Mode couplings in multiplex electromechanical structures". Journal of Applied Physics 132, n. 12 (28 settembre 2022): 124901. http://dx.doi.org/10.1063/5.0103146.

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Mode couplings associated with elastic wave propagation through three-dimensional multiplex structures, as manifested by asymmetric eigenmodes and dissipation, determine the efficiency of electromechanical structures. As a result, it is critical to predict electroelastic symmetric modes such as thickness expander and radial modes, as well as asymmetric flexural modes, while accounting for material losses. Multiplex electromechanical structures include multi-layered through-wall ultrasound power transfer (TWUPT) systems. Physical processes that support TWUPT include vibrations at a transmitting/acoustic source element, elastic wave propagation through a barrier and coupling layers, piezoelectric transduction of elastic vibrations at a receiving element, and spatial resonances of the transmitting and receiving elements. We investigate mode couplings in an optimized modal TWUPT system, including their physical origins, models used to describe them, and regimes of weak and strong couplings. The system layout optimization is defined in terms of size (volume), operating frequency, and matching circuit load optimization. A computational model is developed and utilized in conjunction with experimental modal characterization to highlight the impact of eigenmode features on optimization results. Several behavioral modes are identified and analyzed. The interaction of symmetric radial and asymmetric flexural modes causes the system damping to increase and the device's overall efficiency to decrease. The electromechanical coupling factor value is likewise reduced as a result of this. Such occurrences are explained by the flow of energy between modes as they interact. The present work also proposes design guidelines to improve the performance of TWUPT systems based on exploiting inherent physical phenomena.

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Bai, Wen-Chao, Yan Cao, Ben-Hu Zhou, Jian-Lin Liu, Gui-Xiang Liu, Han Zhang, Han-Zhuang Zhang e Hui Hu. "Theoretical Investigation of Magneto-Electro-Elastic Piezoelectric Phononic Crystal". Crystals 12, n. 6 (20 giugno 2022): 876. http://dx.doi.org/10.3390/cryst12060876.

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We design a magneto-electro-elastic piezoelectric phononic crystal (MPPC) using a one-dimensional piezoelectric superlattice (with a 3m point group) and split-ring resonators. The effect of the split-ring resonators is to enhance the piezoelectric effect of the piezoelectric superlattices. This effect will create elastic anomalies and generate the phononic band gaps. These are first proposed theoretically. We calculate the transmission function of the MPPC through Transfer Matrix Method of the phononic crystal. By using the transmission function, we theoretically study the propagation properties of the acoustic waves in the MPPC. The mechanism for multifield coupling is analyzed. A type of phononic band gap is created, called the multifield coupling phononic band gap. We analyze the possibility of crystals as left-handed metamaterials. We also discuss some potential applications.

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Yang, Jihyun, Jeffrey Shragge e Ge Jin. "Filtering Strategies for Deformation-Rate Distributed Acoustic Sensing". Sensors 22, n. 22 (14 novembre 2022): 8777. http://dx.doi.org/10.3390/s22228777.

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Deformation-rate distributed acoustic sensing (DAS), made available by the unique designs of certain interrogator units, acquires seismic data that are theoretically equivalent to the along-fiber particle velocity motion recorded by geophones for scenarios involving elastic ground-fiber coupling. While near-elastic coupling can be achieved in cemented downhole installations, it is less obvious how to do so in lower-cost horizontal deployments. This investigation addresses this challenge by installing and freezing fiber in shallow backfilled trenches (to 0.1 m depth) to achieve improved coupling. This acquisition allows for a reinterpretation of processed deformation-rate DAS waveforms as a “filtered particle velocity” rather than the conventional strain-rate quantity. We present 1D and 2D filtering experiments that suggest 2D velocity-dip filtering can recover improved DAS data panels that exhibit clear surface and refracted arrivals. Data acquired on DAS fibers deployed in backfilled, frozen trenches were more repeatable over a day of acquisition compared to those acquired on a surface-deployed DAS fiber, which exhibited more significant amplitude variations and lower signal-to-noise ratios. These observations suggest that deploying fiber in backfilled, frozen trenches can help limit the impact of environmental factors that would adversely affect interpretations of time-lapse DAS observations.

40

Novoselov, Artemii, Florian Fuchs e Goetz Bokelmann. "Acoustic-to-seismic ground coupling: coupling efficiency and inferring near-surface properties". Geophysical Journal International 223, n. 1 (19 giugno 2020): 144–60. http://dx.doi.org/10.1093/gji/ggaa304.

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SUMMARY A fraction of the acoustic wave energy (from the atmosphere) may couple into the ground, and it can thus be recorded as ground motion using seismometers. We have investigated this coupling, with two questions in mind, (i) how strong it is for small explosive sources and offsets up to a few tens of meters and (ii) what we can learn about the shallow subsurface from this coupling. 25 firecracker explosions and five rocket explosions were analysed using colocated seismic and infrasound sensors; we find that around 2 per cent of the acoustic energy is admitted into the ground (converted to seismic energy). Transfer coefficients are in the range of 2.85–4.06 nm Pa–1 for displacement, 1.99–2.74 μm s–1 Pa–1 for velocity, and 2.2–2.86 mm s−2 Pa–1 for acceleration. Recording dynamic air pressure together with ground motion at the same site allows identification of different waves propagating in the shallow underground, notably the seismic expression of the direct airwave, and the later air-coupled Rayleigh wave. We can reliably infer shallow ground properties from the direct airwave, in particular the two Lamé constants (λ and μ) and the Poisson ratio. Firecrackers as pressure sources allow constraining elastic parameters in the top-most layer. In this study, they provide frequency-dependent values of λ decreasing from 119 MPa for low frequencies (48 Hz) to 4.2 MPa for high frequencies (341 Hz), and μ values decreasing from 33 to 1.8 MPa. Frequency-dependent Poisson ratios ν are in the range of 0.336–0.366.

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Kruntcheva, Mariana R. "Acoustic-Structural Resonances of Thin-Walled Structure—Gas Systems". Journal of Vibration and Acoustics 128, n. 6 (10 maggio 2006): 722–31. http://dx.doi.org/10.1115/1.2345679.

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This paper summarizes a theoretical study, which is a natural continuation of approximately 50 years of research in the field of acoustoelasticity. Recently, the researchers’ interest has been directed towards considering compressible fluid in contact with thin walled structures as it was found that the acoustic-structural coupling significantly changes the dynamic behavior of the system. Despite the interesting findings the main results still need additional, numerical, or experimental verification. The present work is intended to cast more light on the acoustic-structure coupling of light fluid-shell systems using a numerical approach, namely 3-D finite element (FE) modeling. Two different acoustoelastic systems are considered. The first system is a thin circular cylindrical shell containing light fluid in a coaxial annular duct and the second system is a thin-walled vehicle passenger compartment interacting with the enclosed cavity. Both systems are studied using ANSYS finite element code. The modeling involved shell finite elements for the structure and 3-D acoustic elements for the cavity. The 3-D FE modal analysis used produced results visualizing the complex picture of acoustic-structure coupling. It was confirmed that (1) in both fluid-elastic systems the strongest acoustic-structural coupling exists if the resonances of uncoupled acoustic and mechanical systems are close and (2) the nature of the acoustic-structural coupling is identical in the two cases studied. However, it was found that strong coupling between the thin-walled structure and the acoustic cavity exists in the vicinity of any uncoupled acoustic resonance. Thus, the coupled properties of the systems were found to be dominated by the uncoupled acoustic resonances. As the focus of this study is on the mode shapes of vibration, it was found that coupled acoustic-structure modes of vibration exist in the neighborhood of an uncoupled acoustic resonance, which means that the coupled system manifests a specific type of energy exchange. These modes were termed coupled “combined” modes to differentiate from the coupled component responses. It was also found that the coupled “combined” modes are clustered around a rigid-walled cavity mode, and any acoustic-structure resonance of a given group involves this particular uncoupled acoustic mode. In conclusion, it is shown that the acoustic-structure interaction causes the appearance of coupled “combined” modes not existing in the shell in vacuo or rigid-walled acoustic spectrum. It was found also that the subsystems preserve their capability of independent vibration responses, i.e., the response at the component modes is believed to be strong at their uncoupled frequencies.

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An, Buchao, Chao Zhang, Dejiang Shang, Yan Xiao e Imran Ullah Khan. "A Combined Finite Element Method with Normal Mode for the Elastic Structural Acoustic Radiation in Shallow Water". Journal of Theoretical and Computational Acoustics 28, n. 04 (19 settembre 2020): 2050004. http://dx.doi.org/10.1142/s2591728520500048.

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A combined Finite Element Method with Normal Mode (FEM-NM) is proposed for calculation of the acoustic field radiated by a three-dimensional structural source in shallow water. The FEM is used to calculate the near range acoustic field, then the modes expansion at the vertical and azimuthal direction is performed at a certain coupling range. Hence, the true three-dimensional acoustic field at any range is obtained rapidly by the NM theory. The numerical examples show the efficiency and accuracy of this method. The coupling range and the truncation of the vertical modes hardly affect the far field results.

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Srivastav, P., A. K. Prajapati e P. K. Yadawa. "Theoretical Investigation on Thermal, Mechanical and Ultrasonic Properties of Zirconium Metal with Pressure". Physics and Chemistry of Solid State 24, n. 3 (26 settembre 2023): 549–57. http://dx.doi.org/10.15330/pcss.24.3.549-557.

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Zirconium (Zr), a metal with an hcp structure, has been investigated for the transmission of acoustic wave in the 0 to 25 GPa operating pressure. For this, the Lennard-Jones interaction potential approach has been used to estimate the higher order elastic coefficients (SOECs and TOECs). This model is used to calculate the 2nd and 3rd order elastic parameters for zirconium metal. With the help of SOECs, other elastic moduli such as bulk modulus (B), Young’s modulus (Y) and shear modulus (G) have been calculated for Zr metal using Voigt-Reuss-Hill (VRH) approximations. Later, applying SOECs as well as zirconium density under the same pressure range, three orientation dependent acoustic velocities, comprising Debye average velocities, have been studied. Basic thermal characteristics such as specific heat at constant volume, thermal conductivity associated with lattice, thermal energy density, thermal relaxation time as well as acoustic coupling coefficients of zirconium metal have been also calculated at same pressure range. The computation is also satisfactory in estimating the ultrasonic attenuation coefficients, arises due to the interaction of phonons, hardness as well as melting temperature under various pressures in this research work.

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Zhang, Hong, Yiqun Ding, Lin He, Changgeng Shuai e Chao Jiang. "The Vibro-Acoustic Characteristics Analysis of the Coupled System between Composite Laminated Rotationally Stiffened Plate and Acoustic Cavities". Applied Sciences 14, n. 3 (24 gennaio 2024): 1002. http://dx.doi.org/10.3390/app14031002.

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In order to study vibro-acoustic characteristics between composite laminated rotationally stiffened plate and acoustic cavities in the coupled system, first-order shear deformation theory (FSDT) and modified Fourier series are used to construct a unified analysis model. The involved coupled systems primarily encompass three types: the coupled system between composite laminated rotationally stiffened plate and cylindrical-cylindrical cavities, spherical-cylindrical cavities, and conical-cylindrical cavities. First, the first-order shear deformation theory and the modified Fourier series are applied to construct the allowable displacement function of the composite laminated rotationally stiffened plate and the allowable sound pressure function of the acoustic cavities. Second, the energy functionals for the structural domain and the acoustic field domain are established, respectively. According to the continuity condition of the particle vibration velocity at the coupling boundary between the composite, laminated cylindrical shell and the enclosed cavity, the coupling potential energy between the stiffened plate and two acoustic cavities is introduced to obtain the energy functional of the coupled system. Third, the Rayleigh-Ritz method is utilized to solve the energy functional and, when combined with artificial virtual spring technology, the suggested theory may be used to study the vibro-acoustic characteristics of a coupled system with arbitrary elastic boundary conditions. Finally, based on validating the fast convergence and correctness of the model, this paper will analyze the impact of crucial parameters on vibro-acoustic characteristics. Furthermore, by incorporating internal point forces and point-sound source stimulation, a steady-state response analysis of the coupled system will be conducted. This research can give a theoretical foundation for the vibration and noise reduction of a vibro-acoustic coupling system.

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Maury, Cédric, e Teresa Bravo. "Vibrational Effects on the Acoustic Performance of Multi-Layered Micro-Perforated Metamaterials". Vibration 6, n. 3 (17 settembre 2023): 695–714. http://dx.doi.org/10.3390/vibration6030043.

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Broadband noise reduction over the low–mid frequency range in the building and transportation sectors requires compact lightweight sound absorbers of a typical subwavelength size. The use of multi-layered, closely spaced (micro-)perforated membranes or panels, if suitably optimized, contributes to these objectives. However, their elasticity or modal behaviors often impede the final acoustical performance of the partition. The objective of this study is to obtain insights into the vibrational effects induced by elastic limp membranes or panel volumetric modes on the optimized sound absorption properties of acoustic fishnets and functionally graded partitions (FGP). The cost-efficient global optimization of the partitions’ frequency-averaged dissipation is achieved using the simulated annealing optimization method, while vibrational effects are included through an impedance translation method. A critical coupling analysis reveals how the membranes or panel vibrations redistribute the locations of the Hole-Cavity resonances, as well as their cross-coupling with the panels’ first volumetric mode. It is found that elastic limp micro-perforated membranes broaden the pass-band of acoustic fishnets, while smoothing out the dissipation ripples over the FGP optimization bandwidth. Moreover, the resonance frequency of the first panels mode sets an upper limit to the broadband optimization of FGPs, up to which a high dissipation, high absorption, and low transmission can be achieved.

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Hussain, Akhtar, Saleem Asghar e Tasawar Hayat. "The impulse response of an acoustic wave from coupling of absorbing-elastic plates." Journal of the Acoustical Society of Japan (E) 20, n. 5 (1999): 333–38. http://dx.doi.org/10.1250/ast.20.333.

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Göransson, Peter. "Acoustic and vibrational damping in porous solids". Philosophical Transactions of the Royal Society A: Mathematical, Physical and Engineering Sciences 364, n. 1838 (2 dicembre 2005): 89–108. http://dx.doi.org/10.1098/rsta.2005.1688.

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A porous solid may be characterized as an elastic–viscoelastic and acoustic–viscoacoustic medium. For a flexible, open cell porous foam, the transport of energy is carried both through the sound pressure waves propagating through the fluid in the pores, and through the elastic stress waves carried through the solid frame of the material. For a given situation, the balance between energy dissipated through vibration of the solid frame, changes in the acoustic pressure and the coupling between the waves varies with the topological arrangement, choice of material properties, interfacial conditions, etc. Engineering of foams, i.e. designs built on systematic and continuous relationships between polymer chemistry, processing, micro-structure, is still a vision for the future. However, using state-of-the-art simulation techniques, multiple layer arrangements of foams may be tuned to provide acoustic and vibrational damping at a low-weight penalty. In this paper, Biot's modelling of porous foams is briefly reviewed from an acoustics and vibrations perspective with a focus on the energy dissipation mechanisms. Engineered foams will be discussed in terms of results from simulations performed using finite element solutions. A layered vehicle-type structure is used as an example.

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Xu, He, e Deyi Kong. "A thin-film acoustic metamaterial absorber with tunable sound absorption characteristics". Journal of the Acoustical Society of America 153, n. 6 (1 giugno 2023): 3493–500. http://dx.doi.org/10.1121/10.0019852.

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A thin-film absorber with tunable acoustic properties over a wideband is designed based on the acoustic metamaterial theory. The thin-film acoustic metamaterial absorber (TFAMA) consists of a frame made of piezoelectric material and several flexible films with attached mass blocks (mass-spring vibration system). Based on the vibration mechanism of the mass-spring vibration system, a cellular model of local resonance form is established, and the material properties of negative effective mass are discussed. Combined with the vibration modal analysis of the coupling of mass block, elastic film, and piezoelectric material, the acoustic characteristics of the TFAMA under alternating voltage excitation are studied by finite element and experimental methods. The simulation and experimental results show that the sound wave can be well absorbed when it is incident on TFAMA to cause the membrane-cavity coupling resonance. By applying an alternating voltage to the TFAMA to excite the mass-spring vibration system to generate local resonance, the absorption of sound waves can be further enhanced in a relatively wide band near the excitation frequency. In view of the convenience of voltage parameter adjustment, the sound absorption band can be flexibly tuned in a wide range, including low frequency.

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Renping, Shao, Purong Jia e Xiankun Qi. "3-D elastic coupling vibration and acoustical radiation characteristics of cracked gear under elastic support condition". Journal of Vibration and Control 23, n. 9 (23 ottobre 2015): 1548–68. http://dx.doi.org/10.1177/1077546315596482.

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According to the actual working condition of the gear, the supporting gear shaft is treated as an elastic support. Its impact on the gear body vibration is considered and investigated and the dynamic response of elastic teeth and gear body is analyzed. On this basis, the gear body is considered as a three-dimensional elastic disc and the gear teeth are treated as an elastic cantilever beam. Under the conditions of the elastic boundary (support shaft), combining to the elastic disk and elastic teeth, the influence of three-dimensional elastic discs on the meshing tooth response under an elastic boundary condition is also included. A dynamic model of the gear support system and calculated model of the gear tooth response are then established. The inherent characteristics of the gear support system and dynamics response of the meshing tooth are presented and simulated. It was shown by the results that it is correct to use the elastic support condition to analyze the gear support system. Based on the above three-dimensional elastic dynamics analysis, this paper set up a dynamics coupling model of a cracked gear structure support system that considered the influence of a three-dimensional elastic disc on a cracked meshing tooth under elastic conditions. It discusses the dynamic characteristic of the cracked gear structure system and coupling dynamic response of the meshing tooth, offering a three-dimensional elastic body model of the tooth root crack and pitch circle crack with different sizes, conducting the three-dimensional elastic dynamic analysis to the faulty crack. ANSYS was employed to carry out dynamic responses, as well as to simulate the acoustic field radiation orientation of a three-dimensional elastic crack body at the tooth root crack and pitch circle with different sizes.

50

Lv, Hongrui, Yinglong Huang, Yujie Ai, Zhe Liu, Defeng Lin, Zhe Cheng, Lifang Jia, Bingliang Guo, Boyu Dong e Yun Zhang. "An Experimental and Theoretical Study of Impact of Device Parameters on Performance of AlN/Sapphire-Based SAW Temperature Sensors". Micromachines 13, n. 1 (28 dicembre 2021): 40. http://dx.doi.org/10.3390/mi13010040.

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The impact of device parameters, including AlN film thickness (hAlN), number of interdigital transducers (NIDT), and acoustic propagation direction, on the performance of c-plane AlN/sapphire-based SAW temperature sensors with an acoustic wavelength (λ) of 8 μm, was investigated. The results showed that resonant frequency (fr) decreased linearly, the quality factor (Q) decreased and the electromechanical coupling coefficient (Kt2) increased for all the sensors with temperature increasing from −50 to 250 °C. The temperature coefficients of frequency (TCFs) of sensors on AlN films with thicknesses of 0.8 and 1.2 μm were −65.57 and −62.49 ppm/°C, respectively, indicating that a reduction in hAlN/λ favored the improvement of TCF. The acoustic propagation direction and NIDT did not obviously impact the TCF of sensors, but they significantly influenced the Q and Kt2 of the sensors. At all temperatures measured, sensors along the a-direction exhibited higher fr, Q and Kt2 than those along the m-direction, and sensors with NIDT of 300 showed higher Q and Kt2 values than those with NIDT of 100 and 180. Moreover, the elastic stiffness of AlN was extracted by fitting coupling of modes (COM) model simulation to the experimental results of sensors along different directions considering Euler transformation of material parameter-tensors. The higher fr of the sensor along the a-direction than that along the m-direction can be attributed to its larger elastic stiffness c11, c22, c44, and c55 values.

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