Constrained Layer Damping Research Articles

Topology Optimization for Constrained Layer Damping Plates Using Evolutionary Structural Optimization Method

The evolutionary structural optimization (ESO) is used to optimize constrained damping layer structure. Considering the vibration and energy dissipation mode of the plate with constrained layer damping treatment, the elements of constrained damping layers and modal loss factor are considered as design variable and objective function, while damping material consumption is considered as a constraint. The sensitivity of modal loss factor to design variable is further derived using modal strain energy analysis method. Numerical example is used to demonstrate the effectiveness of the proposed topology optimization approach. The results show that vibration energy dissipation of the plates can be enhanced by the optimal constrained layer damping layout.

Damping Analysis of Multilayer Passive Constrained Layer Damping on Cylindrical Shell Using Transfer Function Method

Based on the Donnell assumptions and linear viscoelastic theory, the constitutive relations for the multilayer passive constrained layer damping (PCLD) cylindrical shell are described. In terms of energy, the motion equations and boundary conditions of the cylindrical shell with multilayer PCLD treatment are derived by the Hamilton principle. After trigonometric series expansion and Laplace transform, the state vector is introduced and the dynamic equation in state space is established. The transfer function method is used to solve the state equation. The dynamic performance including the natural frequency, the loss factor, and the frequency response of the multilayer PCLD cylindrical shell is obtained. The results show that with more layers, the more effective in suppressing vibration and noise, if the same amount of visco-elastic and constrained material is applied. It demonstrates a potential application of multilayer PCLD treatment in some critical structures, such as cabins of aircrafts, hulls of submarines, and bodies of rockets and missiles.

Topology optimization of microstructures of viscoelastic damping materials for a prescribed shear modulus

Damping performance of a passive constrained layer damping (PCLD) structure mainly depends on the geometric layout and physical properties of the viscoelastic damping material. Properties such as t...

Nonlinear finite element analysis of smart laminated composite sandwich plates

This paper deals with the nonlinear dynamic analysis of smart laminated composite sandwich plates. A three dimensional energy based finite element (FE) model has been developed for the composite sandwich plates integrated with the patches of active constrained layer damping (ACLD) treatment. Von Kármán type nonlinear strain–displacement relations and the first-order shear deformation theory (FSDT) are adopted individually for each layer of the sandwich plate in developing the FE model. The constraining layer of the ACLD treatment is considered to be made of active fiber composite (AFC) material. The Golla–Hughes–McTavish (GHM) method is used to model the constrained viscoelastic layer of the ACLD treatment in the time domain. Sandwich plates with symmetric and antisymmetric laminated faces separated by HEREX core are considered for evaluation of the numerical results. The numerical results indicate that the ACLD patches significantly improve the damping characteristics of the composite sandwich plates for suppressing their geometrically nonlinear transient vibrations. The effect of variation of piezoelectric fiber orientation angle in the AFC material on the control authority of the ACLD patches is also investigated.

Constrained Layer Damper Modelling and Performance Evaluation for Eliminating Squeal Noise in Trams

This paper presents the modelling and design of a constrained layer damper to eliminate squeal noise in a particular tram. Even though resilient wheels are installed in every bogie, squeal noise is generated at the frequency of 780–800 Hz due to the small radius curves that the tram has to draw. Tuned constrained layer dampers provide a solution to this particular problem. Butyl rubber is chosen as the viscoelastic material for the damper, and conventional steel is used for the metallic sheets. The modelling approach and the final design of the damper are presented, together with evaluation of its performance in a real application. Experimental measurements on track have demonstrated that the constrained layer damper is properly tuned to the squealing frequency and that there is a significant reduction in noise when the proposed damper is attached to the wheels.

Vibration Suppression of a Large Beam Structure Using Tuned Mass Damper and Eddy Current Damping

For a few decades, various methods to suppress the vibrations of structures have been proposed and exploited. These include passive methods using constrained layer damping (CLD) and active methods using smart materials. However, applying these methods to large structures may not be practical because of weight, material, and actuator constraints. The objective of the present study is to propose and exploit an effective method to suppress the vibration of a large and heavy beam structure with a minimum increase in mass or volume of material. Traditional tuned mass dampers (TMD) are very effective for attenuating structural vibrations; however, they often add substantial mass. Eddy current damping is relatively simple and has excellent performance but is force limited. The proposed method is to apply relatively light-weight TMD to attenuate the vibration of a large beam structure and increase its performance by applying eddy current damping to a TMD. The results show that the present method is simple but effective in suppressing the vibration of a large beam structure without a substantial weight increase.

Experimental Investigation of Damping Performance of Viscoelastic Material Using Constrained Layer Damping Treatment

The purpose of this paper is to determine the performance of damping provided by different viscoelastic materials (VEM). The damping performance of the viscoelastic material is investigated using constrained layer damping (CLD) treatment. Using the viscoelastic material as the core layer in the CLD structures, significant amount of damping can be obtained with minimum impact on the total mass of the structure. Viscoelastic polymeric materials have been used to damp vibrations for many years. Energy is dissipated through relaxation processes in the long chain molecular networks when a polymeric material is subjected to vibrations.In the current study, experimental investigation of the different viscoelastic materials is performed using Oberst beam test specimens and an impulse technique as per ASTM Standard E 756(05). The amount of damping of structure is measured by half- power bandwidth method.

Acoustic Modeling of a 3-Layered Panel Incorporating Electro-Rheological/ Magneto-Rheological (EMR) Fluids

Applications of Electro-Rheological (ER) or Magneto-Rheological (MR) fluids as typical smart materials have been widely investigated over the past decades (since their introduction in 40’s). The special applications of these materials as a means of noise suppression are not yet investigated. Constrained Layer Damping (CLD) sheets can be realized by incorporating EMR (ER/MR) materials. In this way, a multilayered damping sheet is obtained with adaptive (tunable) stiffness and damping characteristics. These properties are easily changed in proportion to the electric (magnetic) field applied upon the EMR layer. This notion has been introduced for semi-active vibration control problems. Herein, such panels incorporating EMR material are proposed for adaptive acoustic treatments. Modeling (simulation) of a 3-layered panel with the middle layer being EMR with adjustable properties is carried out in this paper. The tunability of transmission/absorption characteristics of these composite sheets enables us making smart panels for adaptive noise and acoustic treatments. An adaptive performance can be achieved via changing the properties of such panels, on line, according to some sensor outputs. The main objective is to develop proper models to predict the Transmission Loss (TL) of such panels. Also, the TL of this panel is compared with the middle layer of a Newtonian fluid.

On the Use of Active Fiber Composites for Smart Control of Nonlinear Vibrationsof Sandwich Shells

This paper deals with the control of nonlinear vibrations of smart sandwich shallow shells using active fiber composites. For this purpose, a finite element model is developed for the sandwich shells integrated with the patches of active constrained layer damping treatment. The constraining layer of the patch is considered to be ofactive fiber compositematerial.Five sets of displacement fields describing the kinematics of deformation and satisfying the boundary conditions are used along with the Von Kármán nonlinear strain-displacement relations.To model the constrained viscoelastic layer of the patch,Golla–Hughes– McTavish method is used. Sandwich shallow shells with symmetric laminated faces are considered for presenting the numerical results.

Interface-derived extraordinary viscous behavior of exfoliated graphite

Exfoliated graphite is obtained by the rapid heating of acid-intercalated graphite flakes. It exhibits a cellular microstructure, with about 60 graphite layers in the cell wall. The recently reported extraordinarily strong viscous behavior of the exfoliated graphite and its cement-matrix composite has been explained in this paper in terms of an interface-derived viscous mechanism, which is in contrast to the well-known bulk viscous deformation mechanism that rubber exhibits. The interfacial mechanism is associated with the dynamic sliding at low amplitudes between the graphite layers in the cell wall of exfoliated graphite during dynamic loading in the elastic regime. The ease of sliding is enabled by the loosening of the interlayer interface that has occurred during exfoliation, in which the cell wall extends greatly like a balloon due to extensive sliding between the graphite layers in the cell wall. The viscous behavior is consistent with the well-known resiliency of flexible graphite, which is a sheet made by greatly compressing exfoliated graphite without a binder. In the cement-matrix composite, the exfoliated graphite is sandwiched with sufficient tightness by the cement matrix in the microstructure of the composite, thereby providing constrained-layer damping in the microscale.

Analysis and active control for wind induced vibration of beam with ACLD patch

The structural vibration suppression with active constrained layer damping (ACLD) was widely studied recently. However, the literature seldom concerned with the vibration control on flow-induced vibration using active constrained layer. In this paper the wind induced vibration of cantilevered beam is analyzed and suppressed by using random theory together with a velocity feedback control strategy. The piezoelectric material and frequency dependent viscoelastic layer are used to achieve effective active damping in the vibration control. The transverse displacement and velocity in time and frequency domains, as well as the power spectral density and the mean-square value of the transverse displacement and velocity, are formulated under wind pressure at variable control gain. It is observed from the numerical results that the wind induced vibration can be significantly suppressed by using a small outside active voltage on the constrained layer.

Vibration Power Flow Analysis of a Submerged Constrained Layer Damping Cylindrical Shell

The vibration power flow in a submerged infinite constrained layer damping (CLD) cylindrical shell is studied in the present paper using the wave propagation approach. Dynamic equations of the shell are derived with the Hamilton principle in conjunction with the Donnell shell assumptions. Besides, the pressure field in the fluid is described by the Helmholtz equation and the damping characteristics are considered with the complex modulus method. Then, the shell-fluid coupling dynamic equations are obtained by using the coupling between the shell and the fluid. Vibration power flows inputted to the coupled system and transmitted along the shell axial direction are both studied. Results show that input power flow varies with driving frequency and circumferential mode order, and the constrained damping layer will restrict the exciting force inputting power flow into the shell, especially for a thicker viscoelastic layer, a thicker or stiffer constraining layer (CL), and a higher circumferential mode order. Cut-off frequencies do not exist in the CLD cylindrical shell, so that the exciting force can input power flow into the shell at any frequency and for any circumferential mode order. The power flow transmitted in the CLD cylindrical shell exhibits an exponential decay form along its axial direction, which indicates that the constrained damping layer has a good damping effect, especially at middle or high frequencies.

Modeling and dynamics analysis of shells of revolution by partially active constrained layer damping treatment

A new model for a smart shell of revolution treated with active constrained layer damping (ACLD) is developed, and the damping effects of the ACLD treatment are discussed. The motion and electric analytical formulation of the piezoelectric constrained layer are presented first. Based on the authors' recent research on shells of revolution treated with passive constrained layer damping (PCLD), the integrated first-order differential matrix equation of a shell of revolution partially treated with ring ACLD blocks is derived in the frequency domain. By virtue of the extended homogeneous capacity precision integration technology, a stable and simple numerical method is further proposed to solve the above equation. Then, the vibration responses of an ACLD shell of revolution are measured by using the present model and method. The results show that the control performance of the ACLD treatment is complicated and frequency-dependent. In a certain frequency range, the ACLD treatment can achieve better damping characteristics compared with the conventional PCLD treatment.

Damping ratios of pristine composite beam and constrained layer damped composite beam of equal stiffness

Constrained layer damping is one of the passive techniques to control amplitude of vibration of structural components. In the present work an attempt has been made to quantify and compare damping ratios of composite-rubber-composite sandwich beam with that of pristine composite beam having nearly the same flexural stiffness and range of frequency of vibration from 20 Hz to 100 Hz. Length and thickness of sandwich and pristine beams in order to have the same flexural stiffness and desired frequency range of vibration were specifically designed. The damping ratio of each sandwich and pristine composite beams were measured experimentally using logarithmic decay and half-power bandwidth techniques.

Improved Transfer Matrix Method in Analysis of Cylindrical Shell with Partially Covered Constrained Layer Damping

The transfer matrix method in analysis of cylindrical shell with partially covered ring-shape constrained layer damping is improved. In this new method, state vector and boundary condition vectors are independent, so the computation of state vectors first derivative is simplified. An association matrix is introduced to connect state vectors and boundary condition vectors. In the uncovered section, the parameters of damping layer and constrained layer are considered as constant and leaded into state vectors and boundary condition vectors, so the transfer matrixs dimension of uncovered and covered section are same and the total transfer matrix can be obtained easily. The validity of this method is proved by an example.

Topology Optimization of Passive Constrained Layer Damping on Plates with Respect to Noise Control

The square of normal surface velocity of a thin plate with a harmonic excitation is minimized by optimizing the topologies of attached passive constrained layer damping (PCLD) treatments. An extended solid isotropic material with penalization model for topology optimization is introduced based on a simple interface finite element modeling for viscoelastic layer of PCLD patch. For the purpose of illustrating the proposed method, a clamped square plate is used in the numerical study. Significant reductions of the objective functions are achieved by the optimal distributions.

Smart damping of laminated fuzzy fiber reinforced composite shells using 1–3 piezoelectric composites

This paper deals with the investigation of active constrained layer damping (ACLD) of smart laminated continuous fuzzy fiber reinforced composite (FFRC) shells. The distinct constructional feature of a novel FFRC is that the uniformly spaced short carbon nanotubes (CNTs) are radially grown on the circumferential surfaces of the continuous carbon fiber reinforcements. The constraining layer of the ACLD treatment is considered to be made of vertically/obliquely reinforced 1–3 piezoelectric composite materials. A finite element (FE) model is developed for the laminated FFRC shells integrated with the two patches of the ACLD treatment to investigate the damping characteristics of the laminated FFRC shells. The effect of variation of the orientation angle of the piezoelectric fibers on the damping characteristics of the laminated FFRC shells has been studied when the piezoelectric fibers are coplanar with either of the two mutually orthogonal vertical planes of the piezoelectric composite layer. It is revealed that radial growth of CNTs on the circumferential surfaces of the carbon fibers enhances the attenuation of the amplitude of vibrations and the natural frequencies of the laminated FFRC shells over those of laminated base composite shells without CNTs.

Control of geometrically nonlinear vibrations of skew laminated composite plates using skew or rectangular 1–3 piezoelectric patches

This paper deals with the analysis of active constrained layer damping (ACLD) of geometrically nonlinear transient vibrations of skew laminated composite plates using skew or rectangular patches of the ACLD treatment. The constraining layer of the patch of the ACLD treatment is composed of the vertically/obliquely reinforced 1–3 piezoelectric composite material. The Golla–Hughes–McTavish method has been used to model the constrained viscoelastic layer of the ACLD treatment in the time domain. A coupled electromechanical nonlinear three dimensional finite element model of skew laminated thin composite plates integrated with the skew or rectangular patches of ACLD treatment has been derived. The performance of the patches is investigated for different configurations of their placements on the top surface of the skew substrate plates. The analysis reveals that the ACLD treatment significantly improves the active damping characteristics of the skew laminated composite plates over the passive damping for suppressing their geometrically nonlinear transient vibrations. It is found that even though the substrate laminated plates are skew, a rectangular patch of the ACLD treatment located at the centre of the top surface of the substrate should be used for optimum damping of geometrically nonlinear vibrations of skew laminated composite plates irrespective of their skew angles and boundary conditions. The effects of piezoelectric fiber orientation angle and the skew angles of the substrate plates on the control authority of the ACLD patches have been emphatically investigated.

Influence of partial constrained layer damping on the bending wave propagation in an impacted viscoelastic sandwich

This paper presents a parametric model to study the transient bending wave propagation in a viscoelastic sandwich plate due to impact loading. The effect of partial constrained layer damping (PCLD) geometry on wave propagation is investigated by comparing with propagation in single layer elastic plate. Several boundary conditions are also considered, and their effect on wave propagation is highlighted.The equation of motion is obtained from Lagrange’s equations. For the single layer plate, the governing equation is solved in time domain using Newman and Wilson method. For the plate with PCLD, the frequency dependant viscoelastic behavior of the core is represented by Prony series; the equation of motion is converted into frequency domain using Fourier transform the displacement is obtained in the frequency domain and is converted into time domain with the Inverse Fast Fourier Transform.The model was validated in our previous paper (Khalfi and Ross (2013)) with experimental results, additional validation is carried in this paper with literature, and good agreement is recorded. The results show that the plate covered with PCLD remains a dispersive medium. The shape of the wave is mainly related to the sandwich stiffness while the viscoelastic layer contributes in reducing the amplitude and speed of propagation. The particularity of this transient model lies in its ability to follow the shape of the bending wave at all times to observe formation, propagation and disappearance. With this model, the influence of any structural input parameters on the bending wave can be studied. The findings presented will also serve as a research base for more advanced horizons.

Transfer function method for frequency response and damping effect of multilayer PCLD on cylindrical shell

Based on the Donnell assumptions and linear visco-elastic theory, the constitutive equations of the cylindrical shell with multilayer Passive Constrained Layer Damping (PCLD) treatments are described. The motion equations and boundary conditions are derived by Hamilton principle. After trigonometric series expansion and Laplace transform, the state vector is introduced and the dynamic equations in state space are established. The transfer function method is used to solve the state equation. The dynamic performance including the natural frequency, the loss factor and the frequency response of clamped-clamped multi-layer PCLD cylindrical shell is obtained. The results show that multi-layer PCLD cylindrical shell is more effective than the traditional three-layer PCLD cylindrical shell in suppressing vibration and noise if the same amount of material is applied. It demonstrates a potential application of multi-layer PCLD treatments in many critical structures such as cabins of aircrafts, hulls of submarines and bodies of rockets and missiles.