Articles de revues : « Viscoelastic Layers »

1

Pshenichnov, Sergey, Radan Ivanov et Maria Datcheva. « Transient Wave Propagation in Functionally Graded Viscoelastic Structures ». Mathematics 10, n^o 23 (29 novembre 2022) : 4505. http://dx.doi.org/10.3390/math10234505.

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Transient wave processes in viscoelastic structures built from functionally graded material (FGM) still remain almost unexplored. In this article, the problem of the propagation of nonstationary longitudinal waves in an infinite viscoelastic layer of a FGM with plane–parallel boundaries is considered. The physical and mechanical parameters of the FGM depend continuously on the transverse coordinate, while the wave process propagates along the same coordinate. The viscoelastic properties of the material are taken into account employing the linear integral Boltzmann–Volterra relations. The viscoelastic layer of the FGM is replaced by a piecewise-homogeneous layer consisting of a large number of sub-layers (a package of homogeneous layers), thus approximating the continuous inhomogeneity of the FGM. A solution of a non-stationary dynamic problem for a piecewise-homogeneous layer is constructed and, using a specific example, the convergence of the results with an increase in the number of sub-layers in the approximating piecewise-homogeneous layer is shown. Furthermore, the problem of the propagation of nonstationary longitudinal waves in the cross section of an infinitely long viscoelastic hollow FGM cylinder, whose material properties continuously change along the radius, is also considered. The cylinder composed of the FGM is replaced by a piecewise-homogeneous one, consisting of a large number of coaxial layers, for which the solution of the non-stationary dynamic problem is constructed. For both the layer and the cylinder composed of a viscoelastic FGM, the results of calculating the characteristic parameters of the wave processes for the various initial data are presented. The influence of the viscosity and inhomogeneity of the material on the dynamic processes is demonstrated.

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Ungar, Eric E. « Damping by Viscoelastic Layers ». Applied Mechanics Reviews 53, n^o 6 (1 juin 2000) : R33—R38. http://dx.doi.org/10.1115/1.3097346.

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Yi, Sung, M. Fouad Ahmad et H. H. Hilton. « Dynamic Responses of Plates With Viscoelastic Free Layer Damping Treatment ». Journal of Vibration and Acoustics 118, n^o 3 (1 juillet 1996) : 362–67. http://dx.doi.org/10.1115/1.2888191.

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Dynamic transient responses of plates with viscoelastic free damping layers are studied in order to evaluate free layer damping treatment performances. The effects of forcing frequencies and temperatures on free-layer viscoelastic damping treatment of plates are investigated analytically. Young’s modulus ratio of structures to viscoelastic damping materials and the damping layer thickness effects on the damping ability are also explored.

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Hetnarski, Richard B., Ray A. West et Joseph S. Torok. « Damping of Vibrations of Layered Elastic-Viscoelastic Beams ». Applied Mechanics Reviews 46, n^o 11S (1 novembre 1993) : S305—S311. http://dx.doi.org/10.1115/1.3122651.

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A five-layer cantilever beam consisting of an elastic core, two symmetric viscoelastic layers, and two elastic constraining layers is considered. The viscoelastic effects are incorporated in the Euler-Bernoulli beam theory. If the contraction and extension of the constraining layers is neglecterd a fourth order differential equation of motion is received. Inclusion of contraction and extension of the constraining layers results in a more accurate sixth order differential equation. Appropriate boundary conditions are derived. Laplace transforms are used extensively. Both the analytical solution and the numerical results are presented.

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Hujare, Pravin P., et Anil D. Sahasrabudhe. « Effect of Thickness of Damping Material on Vibration Control of Structural Vibration in Constrained Layer Damping Treatment ». Applied Mechanics and Materials 592-594 (juillet 2014) : 2031–35. http://dx.doi.org/10.4028/www.scientific.net/amm.592-594.2031.

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The reduction of noise and vibration is a major requirement for performance of any vibratory system. Passive damping technology using viscoelastic materials is classically used to control vibrations. Viscoelastic material among the damping materials is widely used to dissipate the structural vibration energy. Three-layer sandwich beams, made of two elastic outer layers and a viscoelastic layer sandwiched between them, are considered as damping structural elements. This paper presents the effect of thickness of constrained damping material on modal loss factor of vibrating structures. Measurements are performed on sandwich beam structure. In order to understand the effectiveness of the sandwich structures, the dynamics of beam with constrained viscoelastic layers are investigated. Comparisons of the experimental and the Numerical results confirm that the damping levels and the natural frequencies of damped structures are well corroborated.

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Ioannides, E., et P. Grootenhuis. « A Finite Element Analysis of the Harmonic Response of Damped Five-Layer Plates ». Proceedings of the Institution of Mechanical Engineers, Part C : Journal of Mechanical Engineering Science 199, n^o 4 (octobre 1985) : 311–17. http://dx.doi.org/10.1243/pime_proc_1985_199_128_02.

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Solutions have been obtained for the harmonic vibrations of five-layer plates by means of a finite element method. This method is an extension of a previously developed analysis for three-layer plates. The five-layer plates contain two constrained viscoelastic layers which provide the damping. The degenerate case when the thickness of the middle elastic layer becomes zero and the plate is reduced to a four-layer one has also been included in the solution procedure. Moreover, the method allows for the study of both torsional and transverse vibrations of five (or four)-layer beams treated as vibrating plates with a large aspect ratio. As in the case of three-layer plates, triangular finite elements are used to allow for a greater variety of shapes. In the analysis damping is introduced by replacing the real moduli of the viscoelastic material by complex equivalent moduli which account for the phase difference between strain and stress. The present method allows for the non-linear stress-strain behaviour of the viscoelastic layers, the effects of the rotatory inertia and the extension within the viscoelastic layers. The finite element computations have been verified by comparison with experimental results for four-layer and five-layer beams in transverse and torsional vibrations and a five-layer square plate in transverse vibration.

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Gandhi, Farhan, et Brian Munsky. « Effectiveness of Active Constrained Layer Damping Treatments in Attenuating Resonant Oscillations ». Journal of Vibration and Control 8, n^o 6 (juin 2002) : 747–75. http://dx.doi.org/10.1177/1077546029188.

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This paper highlights the importance of considering the piezoelectric constraining layer voltage (or electric field) limits when evaluating the effectiveness of an active constrained layer damping treatment in attenuating resonant vibration. It is seen that, when position feedback is used, intermediate viscoelastic layer stiffness values are always optimal, and maximum allowable control gains and possible vibration attenuation progressively decrease with increasing excitation force levels. On the other hand, with velocity feedback, the optimal viscoelastic layer stiffness is dependent on the excitation level. For low excitation force amplitudes, stiff viscoelastic layers are most effective, with large velocity feedback gains producing substantial vibration attenuation without exceeding piezoelectric layer voltage limits. However, for higher excitation force levels, stiff viscoelastic layers result in excess voltages even at very small velocity feedback gains, and are unable to provide any vibration attenuation. In such a case, intermediate viscoelastic layer stiffness values are preferable, and maximum velocity feedback gains and possible vibration attenuation progressively decrease with increasing excitation level, as in the case of position feedback. For both position and velocity feedback, when excitation forces are beyond a certain level the allowable control gains are so limited that no additional damping is obtained beyond that already available through the passive treatment.

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Wang, Tao, Ryan Murphy, Jing Wang, Shyam S. Mohapatra, Subhra Mohapatra et Rasim Guldiken. « Perturbation Analysis of a Multiple Layer Guided Love Wave Sensor in a Viscoelastic Environment ». Sensors 19, n^o 20 (18 octobre 2019) : 4533. http://dx.doi.org/10.3390/s19204533.

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Surface acoustic wave sensors have the advantage of fast response, low-cost, and wireless interfacing capability and they have been used in the medical analysis, material characterization, and other application fields that immerse the device under a liquid environment. The theoretical analysis of the single guided layer shear horizontal acoustic wave based on the perturbation theory has seen developments that span the past 20 years. However, multiple guided layer systems under a liquid environment have not been thoroughly analyzed by existing theoretical models. A dispersion equation previously derived from a system of three rigidly coupled elastic mass layers is extended and developed in this study with multiple guided layers to analyze how the liquid layer’s properties affect the device’s sensitivity. The combination of the multiple layers to optimize the sensitivity of an acoustic wave sensor is investigated in this study. The Maxwell model of viscoelasticity is applied to represent the liquid layer. A thorough analysis of the complex velocity due to the variations of the liquid layer’s properties and thickness is derived and discussed to optimize multilayer Surface acoustic wave (SAW) sensor design. Numerical simulation of the sensitivity with a liquid layer on top of two guided layers is investigated in this study as well. The parametric investigation was conducted by varying the thicknesses for the liquid layer and the guided layers. The effect of the liquid layer viscosity on the sensitivity of the design is also presented in this study. The two guided layer device can achieve higher sensitivity than the single guided layer counterpart in a liquid environment by optimizing the second guided layer thickness. This perturbation analysis is valuable for Love wave sensor optimization to detect the liquid biological samples and analytes.

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9

Hunt, G., H. Mühlhaus, B. Hobbs et A. Ord. « Localized folding of viscoelastic layers ». Geologische Rundschau 85, n^o 1 (1996) : 58. http://dx.doi.org/10.1007/s005310050052.

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10

Handge, U. A., I. M. Sokolov et A. Blumen. « Fragmentation of viscoelastic surface layers ». Europhysics Letters (EPL) 40, n^o 3 (1 novembre 1997) : 275–80. http://dx.doi.org/10.1209/epl/i1997-00460-0.

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Birger, B. I. « Gravitational Instability in the Earth's Viscoelastic Crust ». Физика земли 2023, n^o 2 (1 mars 2023) : 49–61. http://dx.doi.org/10.31857/s0002333723020059.

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This paper studies instability of a heavy inclusion in the Earth's upper layers by the linear theory method for small perturbations. The existence of such inclusions with increased density is associated with chemical inhomogeneity or phase transitions. The viscoelasticity of the geomaterial is described by the Maxwell rheological model. Two layouts of the inclusion with increased density are considered. The heavy inclusion in the cold upper elastic layer of the crust does not change its location under small perturbations, i.e., it is stable according to the linear theory. The heavy inclusion which is located in the hot viscous crustal layer underlying the upper cold layer, is unstable (slowly sinking into the underlying viscous mantle layers).

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Yartsev, B., V. Ryabov et L. Parshina. « Dissipative properties of three-layered composite structures. 2. Solution method ». Transactions of the Krylov State Research Centre 1, n^o 399 (15 mars 2022) : 55–64. http://dx.doi.org/10.24937/2542-2324-2022-1-399-55-64.

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Object and purpose of research. This paper discusses a three-layered plate made up by two rigid anisotropic layers and soft isotropic medium layer of viscoelastic polymer. Each of the two rigid layers is an anisotropic structure formed by a finite number of arbitrarily oriented orthotropic viscoelastic composite layers. The purpose of this work is to develop a numerical solution method for decaying vibration equations of three-layered unsupported rectangular plates. Materials and methods. The system of algebraic equations is constructed as per Ritz method using Legendre polyno-mials as coordinate functions. The first step is to find real solutions. To find complex natural frequencies of the system, their initial values are taken as real natural frequencies thus found, with subsequent calculation of complex frequencies as per the method of third-order iterations. Main results. This paper discusses the results of convergence analysis for a numerical solution of differential motion equations with respect to an unsupported rectangular three-layered plate with transversally isotropic rigid layers. The material for these rigid lay-ers is unidirectional carbon-reinforced plastic (CRP) with elastic dissipation properties, within the investigated range of frequencies and temperatures, independent on its vibration frequency. For the soft isotropic medium layer of viscoelastic polymer, temperature-frequency curve governing the real part of complex elasticity modulus and mechanical loss coefficient is taken into account. Validation of the mathematical model and the numerical solution method, the comparison of calculated and experimental natural frequencies and mechanical loss coefficients for the two variants of three-layered unsupported plate has demonstrated their good correlation. Conclusion. This paper suggests and validates the numerical solution method for decaying vibration equations of three-layered unsupported rectangular plate made up by two rigid monoclinic layers and soft isotropic medium layer of viscoelastic polymer.

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Mahmoud, Fatin F., Ahmed G. El-Shafei, Amal E. Al-Shorbagy et Alaa A. Abdel Rahman. « Effect of the Material Parameters on Layered Viscoelastic Frictional Contact Systems ». Advances in Tribology 2010 (2010) : 1–14. http://dx.doi.org/10.1155/2010/258307.

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In the design process, one of the main targets is to reduce the peak values of the contact stresses. This can be attained by layering the contacting bodies by layers of different material characteristics. Viscoelastic materials are characterized by either a stress relaxation or a creep deformation; therefore, the contacting bodies can be layered with such materials to attain this target. This paper discusses effects of the material characteristics of viscoelastic layers upon the unbounded contact configuration. Three material parameters are considered: the layer/contact solids stiffness ratio, the delayed/instantaneous elasticity ratio, and the material relaxation time. The results are obtained by using a two-dimensional time-dependent nonlinear computational model, developed by the authors, capable of analyzing quasistatic viscoelastic frictional contact problems.

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Tao, Meng, Hanfeng Ye et Xuefeng Zhao. « Acoustic performance prediction of anechoic layer using identified viscoelastic parameters ». Journal of Vibration and Control 25, n^o 6 (6 décembre 2018) : 1164–78. http://dx.doi.org/10.1177/1077546318813404.

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In this work, the acoustic performance of an anechoic layer, which contains horizontally-distributed cylindrical holes, has been studied using identified viscoelastic dynamic parameters. First, the reflection coefficients of two different viscoelastic anechoic layers (one solid and the other perforated), tested in a water-filled pipe, have been used to develop the identification method for viscoelastic dynamic parameters. In the proposed method, the complex longitudinal wavenumber and the complex transverse wavenumber can be obtained by solving the characteristic equation of viscoelastic cylindrical tube. Then, simulations have been performed using COMSOL software to predict the acoustic performance of the anechoic layer. Based on the model and the identified viscoelastic parameters, the effects of different structural properties, including the radius of hole, the hole horizontal spacing, and the arrangements of holes, on the sound absorption of anechoic layer have been analyzed and discussed. Particularly, the acoustic performance of an anechoic layer under oblique incidence has also been considered.

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Tipalin, S. A., N. F. Shpun'kin et N. V. Kosachev. « Deformation determination of the layers in the axisymmetric forming a two-layer billet ». Izvestiya MGTU MAMI 7, n^o 2-2 (20 mars 2013) : 58–62. http://dx.doi.org/10.17816/2074-0530-68019.

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The paper describes the experimental study of an axisymmetric two-layer workpiece forming with viscoelastic bonding layer. It shows the distribution of thinning of layers in radial the direction is received. It is revealed that the distribution pattern of thinning of the outer and inner layers of the cross section of the billet significantly differ.

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Tran Nam, Hung, et Nga Nguyen Thi Thu. « Nonlinear interfacial contact laws in multi-layer elastic-viscoelastic structural systems ». Transport and Communications Science Journal 75, n^o 4 (15 mai 2024) : 1529–43. http://dx.doi.org/10.47869/tcsj.75.4.5.

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Layered structures are widely used in construction, such as pavement structures consisting of multiple layers of different materials or interfaces between bricks and mortar in masonry structures, etc. In analyzing such structures, understanding the properties of the interface between two layers of materials is essential. If one layer of material contains cracks and layers exhibit viscoelastic behavior, determining the properties of the interface becomes challenging. This study proposes a constitutive mechanical law to model the behavior of the interface between a microcracked viscoelastic medium and an undamaged elastic body based on the homogenization method. The interface is modeled by a layer of zero thickness. The coupling between the homogenization technique and the Griffith’s theory is used to provide the effective behavior of the micro-cracked medium. The interface is modelled as an effective medium (EF) characterized by normal and tangential stiffnesses (CN, CT ). In this work, two viscoelastic models are considered, i.e., Burger and Modified Maxwell. The formulas of CN and CT for two cases of crack distributions (isotropic and transversely isotropic) are obtained by asymptotic techniques where the thickness of the joint tends to zero

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Xu, Chao, et Song Lin. « Damping Performance of Cocured Composite I-Shaped Beams with Embedded Viscoelastic Layers ». Advanced Materials Research 79-82 (août 2009) : 1859–62. http://dx.doi.org/10.4028/www.scientific.net/amr.79-82.1859.

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Composite I-shaped beams are currently used in aerospace, ocean and civil engineering applications. Increasing the vibration damping of composite structures is a concerned need in those applications. This research is an effort to investigate the damping performance of composite I-shaped beams with cocured viscoelastic damping layers using finite element method and modal testing technique. A hybrid finite element model for a damped composite I-shaped beam was developed. Modal strain energy method was used to estimate the linear viscoelastic modal loss factors of the composite beams. A numerical parametric investigation was conducted to study the effects of various parameters on the dynamic properties of composite beams under free-free end boundary condition. Selective design parameters included inserting location and thickness of damping layers. Natural frequency and modal loss factor were also extracted by experimental modal analysis. Static tests were performed to obtain the loss of static stiffness for inserting soft viscoelastic layers. Experimental and analytical results show the inserting location of cocured damping layers has significant effects on the damping and there exists a critical damping layer thickness for optimal damping with less significant modal frequency decrease. Static tests results demonstrate a little loss of static stiffness for embedding low module damping layers. A careful selection of damping layer location and thickness is needed to optimize the damping benefits desirable and the mechanics stiffness reduction that can be tolerated for intergral damping composite structures.

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Yartsev, Boris, Viktor Ryabov et Lyudmila Parshina. « Dissipative properties of composite structures. 1. Statement of problem ». Transactions of the Krylov State Research Centre 4, n^o 398 (15 novembre 2021) : 24–34. http://dx.doi.org/10.24937/2542-2324-2021-4-398-24-34.

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Object and purpose of research. The object under study is a sandwich plate with two rigid anisotropic layers and a filler of soft isotropic viscoelastic polymer. Each rigid layer is an anisotropic structure formed by a finite number of orthotropic viscoelastic composite plies of arbitrary orientation. The purpose is to develop a mathematical model of sandwich plate. Materials and methods. The mathematical model of sandwich plate decaying oscillations is based on Hamilton variational principle, Bolotin’s theory of multilayer structures, improved theory of the first order plates (Reissner-Mindlin theory), complex modulus model and principle of elastic-viscoelastic correspondence in the linear theory of viscoelasticity. In description of physical relations for rigid layers the effects of oscillation frequencies and ambient temperature are considered as negligible, while for the soft viscoelastic polymer layer the temperaturefrequency relation of elastic-dissipative characteristics are taken into account based on experimentally obtained generalized curves. Main results. Minimization of the Hamilton functional makes it possible to reduce the problem of decaying oscillations of anisotropic sandwich plate to the algebraic problem of complex eigenvalues. As a specific case of the general problem, the equations of decaying longitudinal and transversal oscillations are obtained for the globally orthotropic sandwich rod by neglecting deformations of middle surfaces of rigid layers in one of the sandwich plate rigid layer axes directions. Conclusions. The paper will be followed by description of a numerical method used to solve the problem of decaying oscillations of anisotropic sandwich plate, estimations of its convergence and reliability are given, as well as the results of numerical experiments are presented.

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Khudoynazarov, Khayrulla. « LONGITUDINAL-RADIAL VIBRATIONS OF A VISCOELASTIC CYLINDRICAL THREE-LAYER STRUCTURE ». Facta Universitatis, Series : Mechanical Engineering 22, n^o 3 (1 octobre 2024) : 473. http://dx.doi.org/10.22190/fume231219010k.

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The paper considers a cylindrical three-layer structure of arbitrary thickness made of viscoelastic material. It consists of two external bearing layers and a middle layer, the materials of which are generally different. The problem of nonstationary longitudinal-radial vibrations of such a structure is formulated. Based on the exact solutions in transformations of the three-dimensional problem of the linear theory of viscoelasticity for a circular cylindrical three-layer body, a mathematical model of its nonstationary longitudinal-radial vibrations is developed. Equations are derived that allow, based on the results of solving the vibration equations, to determine the stress-strain state of a cylindrical structure and its layers in arbitrary sections. The results obtained allow for special cases of transition into cylindrical viscoelastic and elastic two-layer structures, as well as into homogeneous single-layer cylindrical structures and round rods.

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Würger, Alois. « Viscoelastic properties of confined molecular layers ». Journal of Physics : Condensed Matter 23, n^o 50 (9 novembre 2011) : 505103. http://dx.doi.org/10.1088/0953-8984/23/50/505103.

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Kumar, K. Kishore, Y. Krishna et P. Bangarubabu. « Damping in beams using viscoelastic layers ». Proceedings of the Institution of Mechanical Engineers, Part L : Journal of Materials : Design and Applications 229, n^o 2 (19 août 2013) : 117–25. http://dx.doi.org/10.1177/1464420713500748.

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Ray, Prasun K., et Tamer A. Zaki. « Absolute instability in viscoelastic mixing layers ». Physics of Fluids 26, n^o 1 (janvier 2014) : 014103. http://dx.doi.org/10.1063/1.4851295.

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Naghieh, G. R., Z. M. Jin et H. Rahnejat. « Contact characteristics of viscoelastic bonded layers ». Applied Mathematical Modelling 22, n^o 8 (août 1998) : 569–81. http://dx.doi.org/10.1016/s0307-904x(98)10052-5.

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Oh, J., S. Poh, M. Ruzzene et A. Baz. « Vibration Control of Beams Using Electro-Magnetic Compressional Damping Treatment ». Journal of Vibration and Acoustics 122, n^o 3 (1 janvier 2000) : 235–43. http://dx.doi.org/10.1115/1.1303004.

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A new class of structural damping treatments is introduced. This class is the electro-magnetic damping treatment (EMDT) which relies in its operation on a viscoelastic damping layer sandwiched between two magnetic layers. Interaction between the magnets generates magnetic forces that enhance the compressional damping mechanism of the viscoelastic layer. With proper tuning of the magnetic forces, in response to the structural vibration, undesirable resonances and catastrophic failures can be avoided. The fundamentals and the underlying phenomena associated with the EMDT are investigated theoretically and experimentally. A finite element model is developed to describe the interaction between the dynamics of flexible beams, the viscoelastic damping layer and the magnetic layers. The validity of the developed finite element model is checked experimentally using aluminum beams treated with EMDT patches. The beam/EMDT system is subjected to sinusoidal excitations and its multi-mode response is monitored when the magnetic layers are activated or not. Several control strategies are considered to activate the magnetic layers including simple PD controllers. The performance of the uncontrolled and controlled system is determined at various operating conditions. Attenuation of 49.4 percent is obtained for the amplitude of first mode of vibration (5.2 Hz) with control voltage of 0.2 volts. The attenuation increases to 72.56 percent for the second mode of vibration (28.6 Hz) with a control voltage of 1.68 volts. Comparisons with conventional Passive Constrained Layer Damping (PCLD) treatments emphasize the potential of the EMDT treatment as an effective means for controlling structural vibrations. [S0739-3717(00)00603-6]

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Magdenkov, Vladimir A. « The New Type of Constrained Vibration-Damping Coating ». Journal of Low Frequency Noise, Vibration and Active Control 15, n^o 3 (septembre 1996) : 107–13. http://dx.doi.org/10.1177/026309239601500301.

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Samples of new self-adhesive, constrained vibration-damping coatings (VDC) and layers for “sandwich” type plates for damping flexural waves in plates are described. These coatings consist of aluminium foil, perforated cardboard and layers of self-adhesive viscoelastic material. The results of measurements of the temperature-frequency characteristics of the loss factor of flexural waves in plates which are damped with these coatings are given. Methods of calculation of viscoelastic characteristics of multi-layer constructions are considered. The peculiarities of use of constrained and hard vibration damping coatings are investigated on the first natural frequencies while damping flexural waves of plates and beams, clamped at their edges.

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Baali, Messaoud, et Mohamed Nadir Amrane. « Effect of Insertion Viscoelastic Damping Layer with Different Thicknesses on the Dynamic Response of Multi-layered Beam in Forced Vibration ». Periodica Polytechnica Mechanical Engineering 65, n^o 1 (11 novembre 2020) : 1–9. http://dx.doi.org/10.3311/ppme.11110.

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In this work, we study the effect of the thickness variation of viscoelastic layer inserted in a laminated multi-layer beam in forced vibration on the vertical displacements and on the natural frequencies. The new structure is a sandwich structure composed by two external layers (top and bottom facesheets) of aluminum and viscoelastic core of 3M ISD112 polymers. The viscoelastic model used to describe the behavior of the core is a four-parameter fractional derivative model. The finite element method including the viscoelastic model of fractional derivatives for modeling the sandwich structure is used. The system resolution of the nonlinear equations of motion of the sandwich structure is required to use a numerical integration method as the explicit method of Newmark to obtain the transient response. Also, ANSYS finite element modeling is applied to the sandwich structure to calculate the frequency response in harmonic vibration. The increase in the thickness of the viscoelastic layer leads to a decrease in the amplitudes of vibration. The natural frequencies found by the two methods are very close to the frequencies found experimentally in the literature.

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Ortín, Jordi. « Stokes layers in oscillatory flows of viscoelastic fluids ». Philosophical Transactions of the Royal Society A : Mathematical, Physical and Engineering Sciences 378, n^o 2174 (8 juin 2020) : 20190521. http://dx.doi.org/10.1098/rsta.2019.0521.

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Oscillatory flows of viscoelastic fluids are studied from the perspective of Stokes viscoelastic layers. We identify the governing dimensionless variables, and study the flows in a general way for fluids with linear rheology. Nonlinearities can be treated perturbatively to account for reported flow instabilities. This article is part of the theme issue ‘Stokes at 200 (Part 1)’.

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Abdoun, F., L. Azrar et E. M. Daya. « Damping and Forced Vibration Analyses of a Piezoelectric/Elastic/Viscoelastic/Elastic/Piezoelectric Structures ». Advanced Materials Research 682 (avril 2013) : 1–8. http://dx.doi.org/10.4028/www.scientific.net/amr.682.1.

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A mathematical model for the forced vibration of sandwich structures with a viscoelastic and piezoelectric layers is presented. The active-passive damping is realized by adding piezoelectric sensor and actuator layers to a sandwich viscoelastic structure. The mathematical formulation is developed in a general form in order to take into account for various viscoelastic models in the frequency domain. Frequency dependent Young modulus based on various Maxwells model is used for viscoelastic materials modelling. A numerical method combining the finite element and perturbation methods called asymptotic numerical method is developed for the displacement and frequency dependent problem. Resonance curves for sandwich structures are obtained for various frequency ranges, excitation amplitudes and viscoelastic models. Only some matrix inversions and a few iterations are needed for large frequency ranges.

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Kang, Ludi, Chengpu Sun, Haosheng Liu et Bilong Liu. « Determination of Frequency-Dependent Shear Modulus of Viscoelastic Layer via a Constrained Sandwich Beam ». Polymers 14, n^o 18 (8 septembre 2022) : 3751. http://dx.doi.org/10.3390/polym14183751.

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Viscoelastic material can significantly reduce the vibration energy and radiated noise of a structure, so it is widely used in lightweight sandwich structures. The accurate and efficient determination of the frequency-dependent complex modulus of viscoelastic material is the basis for the correct analysis of the vibro-acoustic behavior of sandwich structures. Based on the behavior of a sandwich beam whose core is a viscoelastic layer, a combined theoretical and experimental study is proposed to characterize the properties of the viscoelastic layer constituting the core. In this method, the viscoelastic layer is bonded between two constraining layers. Then, a genetic algorithm is used to fit the analytical solution of the frequency¬ response function of the free–free constrained beam to the measured result, and then the frequency-dependent complex modulus is estimated for the viscoelastic layer. Moreover, by varying the length of the beams, it is possible to characterize the frequency-dependent complex modulus of the viscoelastic material over a wide frequency range. Finally, the characterized frequency-dependent complex modulus is imported into a finite element model to compute the complex natural frequencies of a sandwich beam, and a comparison of the simulated and measured results displays that the errors in the real parts are within 2.33% and the errors in the imaginary parts are within 3.31%. It is confirmed that the proposed method is feasible, accurate, and reliable. This provides essential technical support for improving the acoustic vibration characteristics of sandwich panels by introducing viscoelastic materials.

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Podile, Mpho, Daramy Vandi Von Kallon, Bingo Masiza Balekwa et Michele Cali. « Design and Modeling of Viscoelastic Layers for Locomotive Wheel Damping ». Vibration 4, n^o 4 (16 décembre 2021) : 906–37. http://dx.doi.org/10.3390/vibration4040051.

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Rail–wheel interaction is one of the most significant and studied aspects of rail vehicle dynamics. The vibrations caused by rail–wheel interaction can become critical when the radial, lateral and longitudinal loads of the vehicle, cargo and passengers are experienced while the vehicle is in motion along winding railroad paths. This mainly causes an excessive production of vibrations that may lead to discomfort for the passengers and shortening of the life span of the vehicle’s body parts. The use of harmonic response analysis (HRA) shows that the wheel experiences high vibrational amplitudes from both radial and lateral excitation. The present study describes a numerical and experimental design procedure that allows mitigation of the locomotive wheel resonance during radial and lateral excitations through viscoelastic layers. It is proven that these high frequencies can be reduced through the proper design of damping layer mechanisms. In particular, three parametric viscoelastic damping layer arrangements were analyzed (on the web of both wheel sides, under the rim of both wheel sides and on the web and under the rim of both wheel sides). The results demonstrate that the correct design and dimensions of these viscoelastic damping layers reduce the high-amplitude resonance peaks of the wheel successfully during both radial and lateral excitation.

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Wang, Tao, Song Lin, Bin Wu et Chao Xu. « Multi-Objective Optimization Design of Composite I-Beam Embedded with Viscoelastic Layers ». Advanced Materials Research 156-157 (octobre 2010) : 456–61. http://dx.doi.org/10.4028/www.scientific.net/amr.156-157.456.

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Damping capacity and stiffness loss must be considered together in the design of integral damping composite structures. In the present paper, a discrete layer beam finite element is used to model and analyze a damped composite I-beam embedded with viscoelastic layers. Two multi-objective optimization models are developed with maximum natural frequency and modal loss factor. In the first model, only one damping layer is embedded in each flange of the I-beam. Design variables consist of damping layer thickness and its inserting location. In the second model, multiple damping layers of equal thickness are embedded in the flanges. Design variables included the number of damping layers and their inserting locations. Multi-objective genetic algorithm is used to solve optimization problems. It is showed that the analysis method has acceptable accuracy for composite damped I-beams, and it is convenient for optimization design of integral damping composite structures, especially for the cases embedded with multiple damping layers.

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Chattopadhyay, A., A. K. Verma, M. S. Chaki et A. K. Singh. « Influence of Rigid, Stress-Free and Yielding Base of a Composite Structure on the Propagation of Rayleigh-Type Wave : A Comparative Approach ». Journal of Mechanics 34, n^o 6 (24 août 2017) : 733–48. http://dx.doi.org/10.1017/jmech.2017.65.

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AbstractIn this paper, case wise studies have been made to investigate the possibility of propagation of Rayleigh-type wave in a composite structure comprised of two transversely-isotropic material layers with viscoelastic effect. The common interface between the layers is considered to be rigid whereas the base has been considered as rigid, stress-free and yielding in three different cases (Case-I, II and III). Closed-form of frequency equation and damped velocity equation has been established analytically for propagation of Rayleigh-type wave in a composite structure for all three cases. In special cases, frequency equations and damped velocity equations for the case of composite structure with rigid, stress-free and yielding base have been found in well-agreement to the established standard results pre-existing in the literature. Numerical and graphical computation of phase and damped velocity of Rayleigh-type wave propagating in the composite structure comprised of double transversely-isotropic viscoelastic Taylor sandstone material layers (Model-I) and double isotropic viscoelastic material layers (Model-II) have been carried out. Significant effect of anisotropy and width ratio of layers, dilatational and volume viscoelasticity associated with viscoelasticity of layer medium and yielding parameter associated with yielding base of composite structure on phase and damped velocities of Rayleigh-type wave for the considered models have been traced out. The comparative study has been performed to unravel the effect of viscoelasticity over elasticity and anisotropy over isotropy in the present problem.

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Hosseini Hashemi, Sh, et H. Bakhshi Khaniki. « Dynamic Behavior of Multi-Layered Viscoelastic Nanobeam System Embedded in a Viscoelastic Medium with a Moving Nanoparticle ». Journal of Mechanics 33, n^o 5 (22 septembre 2016) : 559–75. http://dx.doi.org/10.1017/jmech.2016.91.

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AbstractIn this paper, dynamic behavior of multi-layered viscoelastic nanobeams resting on a viscoelastic medium with a moving nanoparticle is studied. Eringens nonlocal theory is used to model the small scale effects. Layers are coupled by Kelvin-Voigt viscoelastic medium model. Hamilton's principle, eigen-function technique and the Laplace transform method are employed to solve the governing differential equations. Analytical solutions for transverse displacements of double-layered is presented for both viscoelastic nanobeams embedded in a viscoelastic medium and without it while numerical solution is achieved for higher layered nanobeams. The influences of the nonlocal parameter, stiffness and damping parameter of medium, internal damping parameter and number of layers are studied while the nanoparticle passes through. Presented results can be useful in analysing and designing nanocars, nanotruck moving on surfaces, racing nanocars etc.

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Ursin, Bjørn, et Alexey Stovas. « Reflection and transmission responses of a layered isotropic viscoelastic medium ». GEOPHYSICS 67, n^o 1 (janvier 2002) : 307–23. http://dx.doi.org/10.1190/1.1451803.

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Transmission effects in the overburden are important for amplitude versus offset (AVO) studies and for true‐amplitude imaging of seismic data. Thin layers produce transmission effects which depend on frequency and slowness. We consider an inhomogeneous viscoelastic layered isotropic medium where the parameters depend on depth only. This takes into account both the effects of intrinsic attenuation and the effects of the layering (including changes in attenuation). The seismic wavefield is decomposed into up‐ and downgoing waves scaled with respect to the vertical energy flux. This gives important symmetry relations for the reflection and transmission responses. For a stack of homogeneous layers, the exact reflection response can be computed in a numerically stable way by a simple layer‐recursive algorithm. The reflection and transmission coefficients at a plane interface are functions of the complex medium parameters (depending on frequency) and the real horizontal slowness parameter. Approximations for weak contrast and weak attenuation are derived and compared to the exact values in two numerical examples. We derive first‐order approximations of the PP and SS transmission responses which are direct extensions of the well‐known O'Doherty‐Anstey formula. They consist of a phase shift and attenuation term from direct transmission through the layers and two attenuation terms from backscattered P‐ and S‐waves. The average of these transmission responses may be used for overburden corrections in AVO analysis. The first‐order PP and PS reflection responses have been computed for a stack of very thin layers corresponding to about 2800 m thickness. Because of a lack of data, the intrinsic attenuation was assumed to be constant in the layers. In the seismic frequency band, the intrinsic attenuation dominates the thin‐layer effects. Approximate and exact layer‐recursive modeling of the reflection responses for this layered medium are in good agreement.

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Wang, Yichuan, et Igor B. Morozov. « Macroscopic seismic responses of layered linear anelastic solids : Wave-induced internal deformations beyond the viscoelastic model ». GEOPHYSICS 85, n^o 6 (1 novembre 2020) : T343—T357. http://dx.doi.org/10.1190/geo2019-0321.1.

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Seismic wave propagation within thinly layered anelastic reservoirs is modeled by direct application of Lagrangian continuum mechanics. Instead of postulating viscoelastic Q-factors or specific microscopic mechanisms, the anelastic properties of the layers are modeled by using generalized macroscopic internal variables. These variables represent averaged measures of various types of internal deformations of the rock, such as relative movements of grains, inclusions, pores and mobile dislocations, wave-induced pore-fluid flows (WIFFs), capillary and layer-boundary effects, or temperature variations. The continuum-mechanics model reveals the existence of body-force (Darcy-type) frictional effects, which are also absent in the viscoelastic model. To implement the attenuation effects observed in laboratory studies, the mechanical properties of the layers are represented by standard linear solid (Zener) rheologies approximating a mesoscopic-scale WIFF effect known as the drained/undrained transition. Optionally, the layer rheologies also include Biot’s poroelastic effects. All compressional- and shear-wave transmission, reflection, and mode-conversion amplitudes and waveforms for primary and secondary waves are modeled at variable angles of incidence. The modeled records exhibit the expected seismic-wave attenuation and dispersion phenomena but differ from the predictions of viscoelastic modeling. The key observation is that wave-propagation effects are sensitive not only to the Q-factors of the layers but also to properties not considered in conventional models: (1) elastic coupling between the internal variables, (2) body-force friction parameters analogous to fluid mobility, and (3) mechanical properties of contact zones between different rocks, such as the effective permeabilities of layer boundaries. Although challenging, these properties of layer boundaries need to be measured for earth’s media and included in the modeling of seismic waves. Another important general observation from this modeling is that the often observed broadband or near-constant seismic Q may result from superposition of the effects of multiple heterogeneities (layers) and material-property contrasts within the medium.

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Li, Yuhang, Xiaoliang Zhou, Zuguang Bian, Yufeng Xing et Jizhou Song. « Bandgap Structures of SH-Wave in a One-Dimensional Phononic Crystal with Viscoelastic Interfaces ». International Journal of Applied Mechanics 09, n^o 07 (octobre 2017) : 1750102. http://dx.doi.org/10.1142/s1758825117501022.

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Phononic crystal is an artificial periodic structure with the ability to regulate and control the wave propagation of particular frequencies and has been widely used in many applications. The adhesive layer bonding different constituents in the periodic structure of phononic crystals is usually a viscoelastic material, which has frequency-dependent material properties. In this paper, an analytical model based on the transfer matrix method is developed to study the bandgap structures of SH-wave (a shear wave with the propagation direction normal to the motion plane) in a one-dimensional phononic crystal consisting of two different elastic constituents bonded by the viscoelastic adhesive layer. The results show that the viscosity of the adhesive layer has a significant influence on the bandgap structure at the region of high frequency. The effects of various material parameters of the viscoelastic adhesive layer such as the relaxation time, the final-state modulus and the initial-state modulus are systematically studied. These results are very helpful in the practical design of phononic crystals involving the viscoelastic adhesive layers.

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YEO, K. S., H. Z. ZHAO et B. C. KHOO. « Turbulent boundary layer over a compliant surface : absolute and convective instabilities ». Journal of Fluid Mechanics 449 (10 décembre 2001) : 141–68. http://dx.doi.org/10.1017/s0022112001006206.

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A theoretical model for the instability of two-dimensional turbulent boundary layer over compliant surfaces is described. The principal Reynolds stress is modelled by a well-established mixing-length eddy-viscosity formulation of van Driest. The perturbations of the mean velocity and Reynolds stress fields are coupled via the turbulence model. The investigation of instability is carried out from a time-asymptotic spatio-temporal perspective that classifies instabilities as being either convective or absolute. The occurrence of convective and absolute instabilities over viscoelastic compliant layers is elucidated. Compliant surfaces with low damping are susceptible to convective instability, which gives way to an absolute instability when the surfaces become highly damped. The theoretical results are compared against experimental observations of surface waves on elastic and viscoelastic compliant layers.

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Zhou, Sui Hua, Wen Cheng Zhang et An Lin Jiang. « Study on the Method of Designing Sound Absorption Model by Multiple-Layer Structures each Layer’s Natural Impedance ». Advanced Materials Research 217-218 (mars 2011) : 226–32. http://dx.doi.org/10.4028/www.scientific.net/amr.217-218.226.

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The laconic calculating formulae of arbitrary multiple-layer model’s acoustic characteristics are introduced with sound transmission theoretics in multilayer mediums. Taking properties of viscoelastic material in account, the sound absorption characteristics of multiple-layer model covered with viscoelastic material underwater are calculated using formulae deduced. By numerical analysis, the relation between absorption model and material parameters is simulated and the effect of proportion among layers’ natural impedance on acoustic characteristics of sound absorption model is analyzed. Then the method of designing sound absorption model by multiple-layer structures each layer natural impedance is studied. The result is of significance to devising sound absorption material and model.

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Melero, Miguel, Antonio J. Nieto, Angel L. Morales, Eduardo Palomares, Jose M. Chicharro, Carmen Ramiro et Publio Pintado. « Experimental Analysis of Constrained Layer Damping Structures for Vibration Isolation in Lightweight Railway Vehicles ». Applied Sciences 12, n^o 16 (17 août 2022) : 8220. http://dx.doi.org/10.3390/app12168220.

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Rolling stock manufacturers face the challenge of manufacturing lightweight high-speed trains without deteriorating comfort. One of the difficulties is to mantain or increase structural stiffness and damping as the car bodies become lighter. Leaving aside active solutions, which are expensive and generally complex to implement, increasing structural damping by means of viscoelastic patches (via Constrained Layer Damping) seems to be a viable solution which is in fact already used for acoustic insulation in automotive, aerospace and even railway applications. Although there are works in the literature that try to optimise viscoelastic panels, this work presents an experimental study with two essential contributions: (i) to analyse the influence of a broad set of design parameters such as type of the constraining layer (uniform or honeycomb), thickness of the viscoelastic layer, location, covered area and continuity between patches; and (ii) to consider absolute and specific (per unit mass) damping depending on the design scenario. To locally increase the structural damping of an existing lightweight structure without compromising its weight, partial application of thin viscoelastic and constraining layers turned out to be the best solution. To enhance structural damping from the design stages, disregarding constraining layer mass by incorporating its stiffness into the overall stiffness of the structure, full coverage with thick viscoelastic layer and a honeycomb constraining layer with a high cross-section moment of inertia turned out to be the best option, reaching modal damping ratios up to 22 times higher than structures without viscoelastic materials.

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Kuo, Chi-Wei, et C. Steve Suh. « Dispersion and Attenuation of Guided Waves in Tubular Section with Multi-Layered Viscoelastic Coating — Part II : Circumferential Wave Propagation ». International Journal of Applied Mechanics 09, n^o 02 (mars 2017) : 1750016. http://dx.doi.org/10.1142/s1758825117500168.

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In the second part of the study on guided wave motions in a hollow cylinder with epoxy layers, shear and longitudinal modes propagating in the circumferential direction are investigated. The corresponding dispersion and attenuation characteristic equations are derived by incorporating a complex, frequency-dependent constitutive law for the viscoelastic coating material. Continuous displacement boundary conditions are implemented to model perfect interfacial bonds between the tubular section and applied epoxy coatings. The presence of thin dissipative viscoelastic layers has profound impact on the propagation of both the circumferential shear and longitudinal waves. The number of admissible propagating modes increases with increasing number of viscoelastic layers and higher order modes dissipate significantly less at high frequencies than the lower order modes at low frequencies. Over the frequency range considered, all the circumferential propagating modes are significantly more attenuating than their axial propagating counterparts studied in Part 1 of the paper. Generation of the lowest shear wave mode is suppressed at approximately 0.2 MHz in the coated tubular. However, no such definitive cutoff frequencies are observed for the longitudinal modes regardless of how many viscoelastic layers are considered.

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Koohmishi, Mehdi. « Comparison of Pavement Layers Responses with Considering Different Models for Asphalt Concrete Viscoelastic Properties ». Slovak Journal of Civil Engineering 21, n^o 2 (1 juin 2013) : 15–20. http://dx.doi.org/10.2478/sjce-2013-0008.

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Abstract In this paper, a comparison between pavement responses is performed by considering two different models for the linear viscoelastic behavior of an asphalt concrete layer. Two models, the Maxwell model and the Kelvin-Voigt model, are generalized. The former is used in ABAQUS and the latter in KENLAYER. As a preliminary step, an appropriate structural model for a flexible pavement structure is developed in ABAQUS by considering linear elastic behavior for all the layers. According to this model, when the depth of a structural model is equal to 6 meters, there is a good agreement between the ABAQUS and KENLAYER results. In this model, the thickness of the pavement is equal to 30 centimeters, and the thickness of the subgrade is equal to 5.7 meters. Then, the viscoelastic behavior is considered for the asphalt concrete layer, and the results from KENLAYER and ABAQUS are compared with each other. The results indicate that the type of viscoelastic model applied to an asphalt concrete layer has a significant effect on the prediction of pavement responses and, logically, the predicted performance of a pavement.

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Zhang, Hao, Jienan Niu, Ningning Huang et Qifang Yan. « Theoretical and Numerical Analysis of Soil-Pipe Pile Horizontal Vibration Based on the Fractional Derivative Viscoelastic Model ». Advances in Civil Engineering 2021 (18 novembre 2021) : 1–17. http://dx.doi.org/10.1155/2021/4767892.

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To describe the mechanical properties of the system of pipe pile-soil reasonably and accurately, the constitutive relations of the soil around pile and pile core soil are characterized by the fractional derivative viscoelastic model. We assume that the radial and circumferential displacements of the soil around the pile and pile core soil are the functions of r, θ, and z. The horizontal dynamic control equations of soil layers are derived by using the fractional derivative viscoelastic model. Considering the fractional derivative properties, soil layer boundary condition, and contact condition of pile and soil, the potential function decomposition method is used to solve the radial and circumferential displacements of the soil layer. Then, the force of unit thickness soil layer on the pipe pile and the impedance factor of the soil layer are obtained. The horizontal dynamic equations of pipe pile are established considering the effect of soil layers. The horizontal dynamic impedance and horizontal-swaying dynamic resistance at the pile top are obtained by combining the pipe pile-soil boundary conditions and the orthogonal operation of trigonometric function. Numerical solutions are used to analyze the influence of pile and soil parameters on the soil impedance factor and horizontal dynamic impedance at pile top. The results show that the horizontal impedance factors of the soil layer and horizontal dynamic impedance of pipe pile by using the fractional derivative viscoelastic model can be degraded to those of the classical viscoelastic model and the elastic model. For the fractional derivative viscoelastic model of soil layer, the influence of soil around pile on the dynamic impedance is greater than that of pile core soil. The model parameter TOa, the inner radius of pipe pile, and the pile length have obvious effects on the horizontal impedance of the soil layer and pipe pile, while the influence of the pile core soil on the pile impedance is smaller.

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van der Linden, J. H. M., P. E. Wierenga et E. P. Honig. « Viscoelastic behavior of polymer layers with inclusions ». Journal of Applied Physics 62, n^o 5 (septembre 1987) : 1613–15. http://dx.doi.org/10.1063/1.339584.

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Koch, Herbert, et Stuart S. Antman. « Self-Sustained Oscillations of Nonlinearly Viscoelastic Layers ». SIAM Journal on Applied Mathematics 60, n^o 4 (janvier 2000) : 1357–87. http://dx.doi.org/10.1137/s0036139998337954.

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Costello, B. A., P. F. Luckham et S. Manimaaran. « The viscoelastic properties of confined polymer layers ». Colloids and Surfaces A : Physicochemical and Engineering Aspects 86 (juillet 1994) : 291–93. http://dx.doi.org/10.1016/0927-7757(94)02843-5.

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Demir, Ozgur, Demet Balkan, Rahim Can Peker, Muzaffer Metin et Aytac Arikoglu. « Vibration analysis of curved composite sandwich beams with viscoelastic core by using differential quadrature method ». Journal of Sandwich Structures & ; Materials 22, n^o 3 (22 avril 2018) : 743–70. http://dx.doi.org/10.1177/1099636218767491.

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This paper focuses on the vibration analysis of three-layered curved sandwich beams with elastic face layers and viscoelastic core. First, the equations of motion that govern the free vibrations of the curved beams together with the boundary conditions are derived by using the principle of virtual work, in the most general form. Then, these equations are solved by using the generalized differential quadrature method in the frequency domain, for the first time to the best of the authors’ knowledge. Verification of the proposed beam model and the generalized differential quadrature solution is carried out via comparison with the results that already exist in literature and the ANSYS finite element solution combined with the modal strain energy method. The effect of system parameters, i.e. layer thicknesses, the lamination angle of layers and the curvature on the vibration and damping characteristics of a curved sandwich beam with laminated composite face layers and a frequency dependent viscoelastic core is investigated in detail.

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Richter, David, Gianluca Iaccarino et Eric S. G. Shaqfeh. « Effects of viscoelasticity in the high Reynolds number cylinder wake ». Journal of Fluid Mechanics 693 (16 janvier 2012) : 297–318. http://dx.doi.org/10.1017/jfm.2011.531.

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AbstractAt $\mathit{Re}= 3900$, Newtonian flow past a circular cylinder exhibits a wake and detached shear layers which have transitioned to turbulence. It is the goal of the present study to investigate the effects which viscoelasticity has on this state and to identify the mechanisms responsible for wake stabilization. It is found through numerical simulations (employing the FENE-P rheological model) that viscoelasticity greatly reduces the amount of turbulence in the wake, reverting it back to a state which qualitatively appears similar to the Newtonian mode B instability which occurs at lower $\mathit{Re}$. By focusing on the separated shear layers, it is found that viscoelasticity suppresses the formation of the Kelvin–Helmholtz instability which dominates for Newtonian flows, consistent with previous studies of viscoelastic free shear layers. Through this shear layer stabilization, the viscoelastic far wake is then subject to the same instability mechanisms which dominate for Newtonian flows, but at far lower Reynolds numbers.

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Zhu, Xiaosong, Ningjuan Dong, Lijuan Jiao et Hui Zheng. « Uncertain sound transmission loss of composite laminated plates with embedded viscoelastic damping layer ». INTER-NOISE and NOISE-CON Congress and Conference Proceedings 268, n^o 5 (30 novembre 2023) : 3727–36. http://dx.doi.org/10.3397/in_2023_0532.

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Laminated composite structures have been widely applied in the engineering field due to their excellent capacities such as high specific stiffness, high specific strengths and tailorable anisotropic elastic properties. Embedding the viscoelastic damping layers into the laminated composites to construct co-cured composite damping structures provides an effective way to improve the sound insulation capability. In this paper, a semi-analytical model is proposed to investigate the sound transmission loss (STL) of composite laminated structure with embedded viscoelastic damping layer considering its frequency-dependent characteristic. Furthermore, Polynomial Chaos Expansion (PCE) method in conjunction with the semi-analytical model is employed for uncertainty propagation analysis of sound transmission loss of the composite laminated plates subjected to uncertain parameters of frequency-dependent interleaved viscoelastic damping layer. Moreover, numerical simulations are conducted to demonstrate the impacts of the uncertain parameters of the embedded viscoelastic damping layer on the STL of the composite laminated plate. Finally, experiments are carried out to investigate the uncertain acoustic insulation performance of composite laminated plates with embedded damping layer. Key words: Laminated composite structure; Sound transmission loss; Uncertainty analysis; Damping layer; Frequency-dependent properties

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Fang, Zhanpeng, Lei Yao, Junjian Hou et Yanqiu Xiao. « Concurrent Topology Optimization for Maximizing the Modal Loss Factor of Plates with Constrained Layer Damping Treatment ». Materials 15, n^o 10 (13 mai 2022) : 3512. http://dx.doi.org/10.3390/ma15103512.

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Damping performance of the plates with constrained layer damping (CLD) treatment mainly depends on the layout of CLD material and the material physical properties of the viscoelastic damping layer. This paper develops a concurrent topology optimization methodology for maximizing the modal loss factor (MLF) of plates with CLD treatment. At the macro scale, the damping layer is composed of 3D periodic unit cells (PUC) of cellular viscoelastic damping materials. At the micro scale, due to the deformation of viscoelastic damping material affected by the base and constrained layers, the representative volume element (RVE) considering a rigid skin effect is used to improve the accuracy of the effective constitutive matrix of the viscoelastic damping material. Maximizing the MLFs of CLD plates is employed as the design objectives in optimization procedure. The sensitivities with respect to macrodesign variables are formulated using the adjoint vector method while considering the contribution of eigenvectors, while the influence of macroeigenvectors is ignored to improve the computational efficiency in the mesosensitivity analysis. The macro and meso scales design variables are simultaneously updated using the Method of Moving Asymptotes (MMA) to find concurrently optimal configurations of constrained and viscoelastic damping layers at the macro scale and viscoelastic damping materials at the micro scale. Two rectangular plates with different boundary conditions are presented to validate the optimization procedure and demonstrate the effectiveness of the proposed concurrent topology optimization approach. The effects of optimization objectives and volume fractions on the design results are investigated. The results indicate that the optimized layouts of the macrostructure are dependent on the objective mode and the volume fraction on the meso scale. The optimized designs on the meso scale are mainly related to the objective mode. By varying the volume fraction on the macro scale, the optimized designs on the meso scale are different only in their detailed size, which is reflected in the values of the equivalent constitutive matrices.

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Sun, Tie Lin, et Hui Sun. « Research on Measurement Method for Loss Factor of Viscoelastic Material ». Applied Mechanics and Materials 303-306 (février 2013) : 529–32. http://dx.doi.org/10.4028/www.scientific.net/amm.303-306.529.

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A measurement method for loss factor of viscoelastic material was researched. When acoustic wave incident to the surface of submerged elastic plate coated with viscoelastic damping layers, according to boundary conditions of interfaces relationship between reflection acoustic wave in water and loss factor of viscoelastic material was derived. The change of loss factor as frequency goes was also simulated. Loss factor is related to frequency and other parameters of viscoelastic material.

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