Showing papers on "Constrained-layer damping published in 2009"

Active constrained layer damping of geometrically nonlinear transient vibrations of composite plates using piezoelectric fiber-reinforced composite

Abstract: This paper addresses the analysis of active constrained layer damping (ACLD) of geometrically nonlinear transient vibrations of laminated thin composite plates using piezoelectric fiber-reinforced composite (PFRC) materials. The constraining layer of the ACLD treatment is considered to be made of the PFRC materials. The Golla–Hughes–McTavish (GHM) method has been used to model the constrained viscoelastic layer of the ACLD treatment in the time domain. A finite element model has been developed for the cross-ply and antisymmetric angle-ply plates integrated with the patches of ACLD treatment undergoing geometrically nonlinear vibrations. The Von Ka`rma`n-type nonlinear strain displacement relations and the first-order shear deformation theory (FSDT) are used for deriving this coupled electromechanical nonlinear finite element model. The numerical results indicate that the ACLD patches significantly improve the damping characteristics of the cross-ply and antisymmetric angle-ply plates for suppressing the geometrically nonlinear transient vibrations of the plates. Emphasis has also been placed on investigating the effect of variation of fiber orientation in the PFRC material on the control authority of the ACLD patches.

Theoretical and experimental investigations on the active structural–acoustic control of a thin plate using a vertically reinforced 1-3 piezoelectric composite

Abstract: This paper deals with investigations on the active structural–acoustic control of a thin homogeneous isotropic plate using vertically reinforced 1-3 piezoelectric composite (PZC) material. A finite element model is developed for the plate which is integrated with a patch of active constrained layer damping (ACLD) treatment and coupled with an acoustic cavity to describe the coupled structural–acoustic behavior of the plate. The constraining layer of the ACLD treatment is composed of the vertically reinforced 1-3 PZC material. Both in-plane and out-of-plane actuations by the constraining layer of the ACLD treatment have been utilized for deriving the finite element model. An experiment is also carried out to investigate the performance of the patch of the ACLD treatment in which the constraining layer of the patch is made of vertically reinforced 1-3 PZC for active structural–acoustic control of the plate. Both the finite element analysis and the experimental investigation agree with each other and reveal that the vertically reinforced 1-3 PZC material performs excellently for achieving active structural–acoustic control of the isotropic plate.

Multiscale design of a rectangular sandwich plate with viscoelastic core and supported at extents by viscoelastic materials

Abstract: This work presents a multiscale model of viscoelastic constrained layer damping treatments for vibrating plates/beams. The approach integrates a finite element (FE) model of macroscale vibrations and a micromechanical model to include effects of microscale structure and properties. The FE model captures the shear deformation of the viscoelastic core, rotary inertial effects of all layers, and viscoelastic boundaries of the plate. Comparison with analytical and FE results validates the proposed FE model. A self-consistent (SC) model makes the micro to macro scale transition to approximate the effective behavior a heterogeneous core. Modal damping resulting from the presence of voids and negative stiffness regions in the core material is modeled. Results show that negative stiffness regions in the viscoelastic core material, even at low volume fractions, yield superior macroscopic damping behavior. The coupled SC and FE models provide a powerful multiscale predictive design tool for sandwich beams and plates.

Constrained layer damping for hearing assistance devices

Abstract: Disclosed herein, among other things, is a system for constrained layer damping for hearing assistance devices. According to various embodiments, a hollow in-the-ear (ITE) hearing instrument shell is formed. The shell has an air space within a wall of the shell, in various embodiments. A port is created in the wall of the shell. The port is adapted to interface the air space to an area outside the shell, in an embodiment. A viscous fluid is dispensed into the air space via the port, and the viscous fluid is cured within the air space. The cured fluid acts as a constrained layer of mechanical damping within the wall of the ITE shell, reducing audible feedback to a wearer of the ITE.

Optimal Design of Constrained-Layer Damping Structures Considering Material and Operational Condition Variability

Abstract: of a surface treatment is highly sensitive to the variability in operational temperature. This paper proposes a statistical approachto modelthe variabilityof viscoelastic damping material in aconstrained-layer dampinglayout, to predict variability in the dynamic responses of viscoelastic damping material, and to obtain an optimal robust layout that accounts for severe variability in operational temperature. The viscoelastic damping material property can be modeled as a sum of 1) a random complex modulus due to operational temperature variability and 2) experiment/model errors in the complex modulus. The eigenvector dimension reduction method is used in probability analysis to predict the variability in the dynamic responses of the viscoelastic damping material. It is concluded that temperature variability is strongly propagated to that in the dynamic responses of the damping material. This study also performs reliability-based design optimization for an optimal robust design of the constrained-layer damping structure. It is shown that reliability-based design optimization gives a more robust and reliable damping layout design amidst severe variability in operational temperature.

Active structural-acoustic control of laminated composite plates using vertically/obliquely reinforced 1–3 piezoelectric composite patch

Abstract: This article deals with the active structural-acoustic control of thin laminated composite plates using vertically reinforced 1–3 piezoelectric fiber-reinforced composite (PFRC) material for constraining layer of active constrained layer damping (ACLD) treatment. A finite element model is developed for the laminated composite plates integrated with ACLD patches and coupled with acoustic cavity to describe the coupled structural-acoustic behavior of the plates enclosing the cavity. Both in-plane and out of plane actuation of the constraining layer of the ACLD treatment have been utilized for deriving the finite element model. The analysis revealed that the vertical actuation dominates over the in-plane actuation. The performance of PFRC layers of the patches has been investigated for active control of sound radiated from thin symmetric and antisymmetric cross-ply and antisymmetric angle-ply laminated composite plates into the acoustic cavity.

Hybrid Vibration Control of a Circular Cylindrical Shell Using Electromagnetic Constrained Layer Damping Treatment

Abstract: This paper investigates hybrid vibration control of a circular cylindrical shell through electromagnetic constrained layer damping (EMCLD) treatment, which consists of an electromagnet layer, a permanent magnet layer and a sandwiched viscoelastic damping layer. A mathematical model is developed based on the equivalent current method to calculate the electromagnetic control force produced by EMCLD. The governing equations of the shell system are established using Hamilton’s principle and then reduced with the assumed-mode method. The vibration control of a clamped-free circular cylindrical shell is simulated with velocity-proportional feedback to demonstrate the energy dissipation capability of EMCLD. Also, parametric studies are performed to examine the influences of geometry and physical properties of EMCLD on control performance. The results show the distinct energy consumption function of EMCLD in the passive way. The hybrid way provides much better control performance than the passive way in the conce...

Passive viscoelastic constrained layer damping for structural application

Abstract: The purpose behind this study is to predict damping effects using method of passive viscoelastic constrained layer damping. Ross, Kerwin and Unger (RKU) model for passive viscoelastic damping has been used to predict damping effects in constrained layer sandwich cantilever beam. This method of passive damping treatment is widely used for structural application in many industries like automobile, aerospace, etc. The RKU method has been applied to a cantilever beam because beam is a major part of a structure and this prediction may further leads to utilize for different kinds of structural application according to design requirements in many industries. In this method of damping a simple cantilever beam is treated by making sandwich structure to make the beam damp, and this is usually done by using viscoelastic material as a core to ensure the damping effect. Since few years in past viscoelastic materials has been significantly recognized as the best damping material for damping application which are usually polymers. Here some viscoelastic materials have been used as a core for sandwich beam to ensure damping effect. Due to inherent complex properties of viscoelastic materials, its modeling has been the matter of talk. So in this report modeling of viscoelastic materials has been shown and damping treatment has been carried out using RKU model. The experimental results have been shown how the amplitude decreases with time for damped system compared to undamped system and further its prediction has been extended to finite element analysis with various damping material to show comparison of harmonic responses between damped and undamped systems.

Constrained layer damping system and method of making the same

Abstract: A method of producing a constrained layer damping system including a constraining layer, a damping layer, a viscous thermally-activated decoupler (VTAD) layer and a base blank layer. The method includes the steps of blanking a constraining layer, applying a damping layer to the constraining layer to form a constraining/damping construct. A VTAD layer can be applied onto the damping layer to form a layered constraining/damping/VTAD construct in which the VTAD layer has at least one exposed surface. The exposed surface of the VTAD layer on the constraining/damping/VTAD construct is pressed onto a cleansed side of a base blank layer to form a constrained layer damping system.

The effect of visco-elastic core thickness on modal loss factors of a thick three-layer cylinder:

Abstract: Free vibrations of damped three-layer sandwich cylinders with thick layers are considered. In particular, the effect of the different thicknesses for the middle layer on the overall natural frequencies and modal damping factors are studied. The constrained-layer damping is accomplished by sandwiching a linear visco-elastic material between two isotropic elastic cylinders with the same properties. The governing equations are derived analytically by applying Newton's second law of motion for a three-dimensional elastic medium, and by employing complex elastic moduli for the sandwiched layer. Dimensionless natural frequencies and modal loss factors for the first three thickness modes associated with wave numbers of n = 0, 1, 2, 3, and 4 are tabulated for a range of thicknesses for the middle visco-elastic layer while keeping the thicknesses of inner and outer layers unchanged.

Constrained Layer Damping Treatment Design for Aircraft Landing Gear

Abstract: Aircraft design represents an optimization of structures and aerodynamics to meet weight, strength and reliability constraints. Included in this optimization is the landing gear system, which typically accounts for 3 - 7% of the total aircraft weight. For fixed gear designs, a significant amount of the total drag can be attributed to the landing gear, and so both reduction in weight and drag are priorities when designing a landing syster. The use of constrained layer visco-elastic damping on landing gear structural members is a new application since historic use of constrained layer damping has been found on thin plate-like structures. Benefits of low weight and low drag are achievable using the conformal treatment, and this paper investigates specific constrained layer damping applications for cantilever-loaded spring steel landing gear. Achievable damping levels are examined for a 386 lb. aircraft using available damping materials that have been tested to quantify loss factor. Results of the analysis show optimal constrained layer thicknesses for a variety of materials. Weight and aerodynamic drag are quantified for the landing gear with the damping treatment installed.

A matrix method for analyzing vibration of a circular cylindrical shell with partially constrained layer damping treatment

Abstract: Based on the linear theories of thin cylindrical shells and viscoelastic materials,the governing equation generally describing vibration of a sandwich circular cylindrical shell with partially constrained layer damping treatment under harmonic excitation,which can be written in a matrix differential equation of first order,is derived by considering the energy dissipation due to the shear deformation of the viscoelastic layer and the interaction between all layersAfter that a semi-analytical and semi-numerical method for solving this governing equation is presented by means of the extended homogeneous capacity precision integration approachIts essential difference from the recent works on transfer matrix method is that the state vector in governing equation is composed of the twelve displacements and internal forces of the sandwich shell rather than of the displacements and their derivativesAs a result,the present method can be applied to solve the dynamic problems of the kind of sandwich shell with various boundary conditions and partially constrained layer dampingNumerical examples show that the proposed approach is very effective and reliable,compared with the existing analytical solutionsFurthermore,the effects of PCLD coverage percents and locations on FRF are then discussed

A new integrated state transfer matrix method for coupled vibration of fluid-filled circular cylindrical containers with partially passive constrained layer damping treatment and analysis on damping effects under ground motion

Abstract: Based on the general linear elastic theory of thin shells and the potential flow theory,considering energy dissipation of passive constrained layer damping(PCLD)due to shear deformation of its viscoelastic core and fluid-solid coupled interaction,a first order integrated differential matrix equation of a circular cylindrical shell with PCLD treatment was derived firstly.Each element in the state vector of the equation had clearly physical means,so it could be convenient-ly applied to solve dynamic problems of a circular cylindrical shell with different boundary conditions.Secondly,through writing the fluid dynamic pressure as an analytical form with undetermined coefficients and applying the fluid-solid interac-tion condition,the homogenous extended capacity precision integration method and the superposition principle,a semi-an-alytical andsemi-numerical method with high efficient and precision was established.Comparing with the analytical solu-tionsof the axis-symmetrical free vibration of a cylindrical shell(no water filled)fully treated with PCLD under simply supported conditions at both ends,the results obtained by this method were effective.Finally,the dynamic responses of fluid-filled cylindrical shells with partially treated PCLD under harmonic ground motion were presented,and damping effects of different thicknesses,lengths,and locations of PCLD and the complex shear modulus model of the viscoelastic rore were studied.

Vibration analysis of beams with partial constrained layer damping treatment

Abstract: Vibration analysis of beams with sandwich constrained layer damping treatment is extended According to the elastic-viscoelastic principle and the modal strain energy method,an analytical approach for vibration response analysis of a beam with single passive constrained layer damping patch is presented Parametric studies are performed with the established analytical approach to study the effects of constrained layer damping treatment After compare between covered and uncovered beam in time domain and in frequency domain,the appears that the constrained layer damping treatment can achieve better damping and modal strain energy method for beam with damping treatment is more effective

Corrigendum to 'Vibration control of beams with active constrained layer damping'

Abstract: This note corrects two errors in our previous paper ( Li et al 2008 Smart Mater Struct 17 065036) in which the active vibration control of beams treated with active constrained layer damping (ACLD) was studied analytically The equation of motion of the whole beam/ACLD system is deduced again using Hamilton's principle with the Rayleigh–Ritz method Numerical results are recalculated and conclusions similar to those of Li et al ( 2008 Smart Mater Struct 17 065036) can also be drawn

A comparative study on vibration analysis of beams treated with active constrained layer damping using different assumed modes methods

Abstract: Recently, active constrained layer damping (ACLD) has been widely used in vibration control and noise reduction. A typical ACLD structure usually consists of three layers: the piezoelectric constraining layer, the viscoelastic damping layer, and the host structure. In present study, the assumed modes method (AMM) is used for vibration modeling of ACLD beams based on the Mead-Markus's sandwich theory. However, two cases called "case A" and "case B" arise from the different choice of modes. The former chooses modes for three displacements including the axial displacement of the active constraining layer, the axial displacement of the host beam, and the flexural displacement of the whole structure, while the later selects modes for the axial and flexural displacements of the host beam. Detailed comparisons are made on natural frequencies and modal loss factors with the results in the reference. It seems that for the same number of modes, case A and B have similar precision on the 1st natural frequency and modal loss factor, yet case B requires considerably less CPU time.