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This paper presents a modeling technique to study the vibroacoustics of multiple-layered viscoelastic laminated beams using the Biot damping model. In this work, a complete simulation procedure for studying the structural acoustics of the system using a hybrid numerical model is presented. The boundary element method (BEM) was used to model the acoustical cavity, whereas the finite element method (FEM) was the basis for vibration analysis of the multiple-layered beam structure. Through the proposed procedure, the analysis can easily be extended to another complex geometry with arbitrary boundary conditions. The nonlinear behavior of viscoelastic damping materials was represented by the Biot damping model taking into account the effects of frequency, temperature, and different damping materials for individual layers. The curve-fitting procedure used to obtain the Biot constants for different damping materials for each temperature is explained. The results from structural vibration analysis for selected beams agree with published closed-form results, and results for the radiated noise for a sample beam structure obtaine dusing a commercial BEM software are compared with the acoustical results of the same beam by using the Biot damping model. [ABSTRACT FROM AUTHOR]

The viscoelastic damping treatment is a very popular method for attenuating vibration and noise problems. It provides the designer much flexibility in adjusting the system damping to eliminate resonances in the structures. A survey of the previous research on material damping models found inadequacies in developing the numerical models of multiple-layer constrained layers and the introduction of the combination of different viscoelastic damping materials through advanced frequency domain damping models. In this paper, a detailed numerical analysis and design of a multiple-layer constrained damping structure using the Biot damping model are presented to investigate the vibration performance. The nonlinear curve fitting of the complex shear modulus and the transient response solution of the numerical viscoelastic damping structure are also discussed. By the proposed approach, the simple beam problem that is presented can be easily extended to the industrial problem with arbitrary geometries and boundary conditions. The validation of this numerical approach is proven by comparison with the previous closed-form results. [ABSTRACT FROM AUTHOR]

Viscoelastic layered systems provide a simple and flexible solution for damping vibration of sheet metal panels. They also help to effectively eliminate noise from resonant structures and surfaces. This article presents an analytical formulation to predict the stiffness and damping of three layered beams with two different viscoelastic materials adjacent to each other. The complex modulus approach is used to model the elastic and shear moduli of the viscoelastic material and closed-form equations are derived for predicting system stiffness and damping. The model is derived for unsymmetrical setups using variational methods. Experiments are conducted on simply supported three-layered beams at different temperatures to validate theoretical results. Similar results are obtained from both the theoretical model and the experiments. A procedure for the optimization of structural and material parameters for maximizing the damping and minimizing the system mass for a given temperature and frequency range is also presented. [ABSTRACT FROM AUTHOR]

This paper describes a comparison, both analytically and experimentally, between two widely used loss factor estimation techniques frequently used in statistical energy analysis. Analytical models of simple spring/mass/damper systems were created to compare frequency-averaged loss factor values from the single subsystem power injection method and the impulse response decay method. The parameters of the analytical models were varied to study the effects of the total number of modes, amount of damping, location of modes within frequency bands, and the width of the frequency bands on loss factor estimation. The analytical study shows that both methods give accurate loss factor values as long as the damping values remain realistic for linear systems and at least one modal resonance is present in each frequency band. These analytical results were verified experimentally by measuring the loss factors of simple steel plates, with and without damping treatments applied. © 2005 Acoustical Society of America. [ABSTRACT FROM AUTHOR]

An analytical formulation Is presented for predicting the stiffness and damping of constrained layered beams that have multiple viscoelastic damping layers. A model is derived for symmetrical setups using variational methods. The equations to evaluate the stiffness and damping are derived in closed form and can be evaluated for different boundary conditions. The complex modulus approach is used to model the elastic and shear moduli of the viscoelastic material. A parametric analysis has been conducted to study the effects of different parameters on the damping and stiffness of the system under simply supported boundary conditions. The optimization process to obtain structural and material parameters maximizing system damping for a given temperature and frequency range is also presented. [ABSTRACT FROM AUTHOR]

In this paper, the application of passive damping technology using viscoelastic materials to control noise and vibration in vehicles and commercial airplanes is described. Special damped laminates and spray paints suitable for mass production and capable of forming with conventional techniques are now manufactured in a continuous manner using advanced processes. These are widely used in the automotive and aerospace industry in a variety of applications to reduce noise and vibration and to improve interior sound quality. Many of these recent applications are not readily available for dissemination in academe and archival literature. It is hoped that the material presented in this paper will be useful for instruction and further research in developing new and innovative applications in other industries. [Copyright &y& Elsevier]