Constrained Layer Damping Research Articles

Comparative evaluation of cement-matrix composites with distributed versus networked exfoliated graphite

Cement with distributed exfoliated graphite (isotropic) is made by incorporating exfoliated graphite in the wet cement mix; cement with networked exfoliated graphite (anisotropic) is made by compressing a dry mixture of exfoliated graphite and cement particles, followed by curing with water. The graphite layers in the latter are preferentially oriented in the plane perpendicular to the compression direction; the in-plane electrical resistivity is much lower than the out-of-plane resistivity and the loss tangent, storage modulus and loss modulus are much higher for out-of-plane flexure than in-plane flexure. The latter gives higher density, lower electrical resistivity, higher compressive strength and superior vibration damping than the former. Compared to plain cement, it gives higher density and higher compressive strength. In contrast, cement with distributed exfoliated graphite gives lower density and lower compressive strength than plain cement, though it gives lower resistivity and superior damping. Distributed exfoliated graphite is detrimental when silica fume is present. The high damping of cement with networked exfoliated graphite is attributed to the effective sandwiching of the network ligaments by the cement matrix (constrained-layer damping); the high density and compressive strength are attributed to the low porosity caused by the compression of the exfoliated graphite during composite fabrication.

Vibration damping characterization of linseed oil‐based elastomers for its effectiveness to attenuate structural vibration

ABSTRACTVibration damping properties of elastomers prepared from linseed oil were characterized by dynamic mechanical analyzer in a temperature range of −50 to 100°C and frequency range of 5 Hz to 1 kHz. The maximum damping loss factor, varies from 0.78 to 1.32, the room temperature (25°C) loss factor, in the range of 0.56–1.08 and the temperature range ( ) for effective damping varies from 63°C to 74.4°C in different elastomers. The elastomers behave as a good vibration damper both in lower and higher frequency range. Thus these elastomers exhibit good damping behavior in a wide range of temperature and frequency, a primary requirement for practical damping applications. A modal constrained layer damping system constructed utilizing these elastomers exhibits its potentiality to attenuate structural vibrations with respect to mild steel bare plate resonator under laboratory fabricated testing methodology. © 2013 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 130: 3611–3623, 2013

Modeling of a hybrid semi-active/passive vibration control technique

In this paper a new hybrid vibration damping technique as a combination of the semi-active pulse switching technique and passive constrained layer damping is proposed as an effective vibration control method for all frequency ranges. The semi-active pulse switching technique is an effective method to damp any type of vibrations with no need for external energy sources. However, its performance in high-frequency ranges decreases. In addition, passive techniques are not so effective in low-frequency ranges, but have significant effects in high-frequency ranges. The proposed hybrid damping technique as a combination of these two control methods is a new effective control technique for all frequency ranges. It covers the weakness of the semi-active method and provides significant damping in both low and high-frequency vibrations.

Active Constrained Layer Damping of Smart Skew Laminated Composite Plates Using 1–3 Piezoelectric Composites

This paper deals with the analysis of active constrained layer damping (ACLD) of smart skew laminated composite plates. The constraining layer of the ACLD treatment is composed of the vertically/obliquely reinforced 1–3 piezoelectric composites (PZCs). A finite element model has been developed for accomplishing the task of the active constrained layer damping of skew laminated symmetric and antisymmetric cross-ply and antisymmetric angle-ply composite plates integrated with the patches of such ACLD treatment. 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. The analysis revealed that the vertical actuation dominates over the in-plane actuation. Particular emphasis has been placed on investigating the performance of the patches when the orientation angle of the piezoelectric fibers of the constraining layer is varied in the two mutually orthogonal vertical planes. Also, the effects of varying the skew angle of the substrate laminated composite plates and different boundary conditions on the performance of the patches have been studied. The analysis reveals that the vertically and the obliquely reinforced 1–3 PZC materials should be used for achieving the best control authority of ACLD treatment, as the boundary conditions of the smart skew laminated composite plates are simply supported and clamped-clamped, respectively.

An overview of constrained-layer damping theory and application

Beginning in the early 1930s a variety of theoretical and experimental research has been published regarding the development and use of damping. What began as an experiment to reduce noise and vibration in metals and plastics has become a common treatment in an amalgam of applications. Constrained-layer damping (CLD) is a specific method of treatment commonly used in the aerospace and military industries. CLD may be described as a type of shear-related energy dissipation achieved by interconnecting two or more structural materials using a relatively thin viscoelastic layer. Among the advantages of using CLD as a damping treatment are the ability to obtain high loss factors with relatively thin configurations and that the stiffness of the composite system is not markedly increased. The analytic development of constrained-layer damping will be presented along with a brief discussion of the applications of CLD throughout history.

Smart control of nonlinear vibrations of doubly curved functionally graded laminated composite shells under a thermal environment using 1–3 piezoelectric composites

This paper addresses the active control of geometrically nonlinear vibrations of doubly curved functionally graded (FG) laminated composite shells integrated with a patch of active constrained layer damping (ACLD) treatment under the thermal environment. Vertically/obliquely reinforced 1-3 piezoelectric composite (PZC) and active fiber composite (AFC) are used as the materials of the constraining layer of the ACLD treatment. Each layer of the substrate FG laminated composite shell is made of fiber-reinforced composite material in which the fibers are longitudinally aligned in the plane parallel to the top or bottom surface of the layer and the layer is assumed to be graded in the thickness direction by way of varying the fiber orientation angle across its thickness according to a power law. The novelty of the present work is that, unlike the traditional laminated composite shells, the FG laminated composite shells are constructed in such a way that the continuous variation of material properties and stresses across the thickness of the shell is achieved. The Golla-Hughes-McTavish (GHM) method has been implemented to model the constrained viscoelastic layer of the ACLD treatment in time domain. Based on the first-order shear deformation theory (FSDT), a finite element (FE) model has been developed to model the open-loop and closed-loop nonlinear dynamics of the overall FG laminated composite shell under a thermal environment. Both symmetric and asymmetric FG laminated composite doubly curved shells are considered for presenting the numerical results. The analysis suggests that the ACLD patch significantly improves the damping characteristics of the doubly curved FG laminated composite shells for suppressing their geometrically nonlinear transient vibrations. It is found that the performance of the ACLD patch with its constraining layer being made of the AFC material is significantly higher than that of the ACLD patch with vertically/obliquely reinforced 1-3 PZC constraining layer. The effects of variation of piezoelectric fiber orientation in both the obliquely reinforced 1-3 PZC and the AFC constraining layers on the control authority of the ACLD patch have also been investigated.

Active control of geometrically nonlinear vibrations of doubly curved smart sandwich shells using 1–3 piezoelectric composites

This paper deals with the analysis of active damping of geometrically nonlinear vibrations of doubly curved smart sandwich shells integrated with a patch of active constrained layer damping (ACLD) treatment. The substrate sandwich shell is composed of orthotropic laminated composite faces separated by a thick flexible core. The constraining layer of the ACLD treatment is made of the vertically/obliquely reinforced 1–3 piezoelectric composites (PZCs). The constrained viscoelastic layer is modeled using the Golla–Hughes–McTavish (GHM) method in the time domain. A three dimensional finite element (FE) model has been developed to study this coupled nonlinear electro-elastic problem. The numerical results indicate that the ACLD patch significantly improves the damping characteristics of the paraboloid and hyperboloid sandwich shells with laminated cross-ply and angle-ply facings for suppressing their geometrically nonlinear vibrations. Particular emphasis has been placed on investigating the effect of the variation of piezoelectric fiber orientation angle on the performance of the ACLD treatment. Unlike the doubly curved laminated composite shells, the performance of the ACLD treatment becomes maximum for causing active damping of geometrically nonlinear vibrations of doubly curved sandwich shells with laminated composite facings if the constraining layer of the treatment is made of obliquely reinforced 1–3 PZC.

A noise control package for vibrating screens.

Hearing loss was the second-most common illness reported to the Mine Safety and Health Administration (MSHA) in 2009. Furthermore, between 2000 and 2010, 30% of all noise-related injury complaints reported to MSHA were for coal preparation plant employees. Previous National Institute for Occupational Safety and Health (NIOSH) studies have shown that vibrating screens are key noise sources to address in order to reduce coal preparation plant noise. In response, NIOSH researchers have developed a suite of noise controls for vibrating screens consisting of constrained layer damping (CLD) treatments, a tuned mechanism suspension, an acoustic enclosure, and spring inserts. Laboratory testing demonstrates that this noise control suite reduces the A-weighted sound power level of the vibrating screen by 6 dB. To provide a comparison to laboratory results and prove durability, field testing of two noise controls was performed on a vibrating screen in a working coal preparation plant. The spring inserts and CLD treatments were selected due to their ease of installation and practicability. Field testing of these controls yielded reductions that were comparable to laboratory results.

Active Structural-Acoustic Control of Laminated Composite Truncated Conical Shells Using Smart Damping Treatment

This article deals with the active structural-acoustic control of composite truncated circular conical shells using active constrained layer damping (ACLD) treatment. The constraining layer of the ACLD treatment is made of vertically/obliquely reinforced 1–3 piezoelectric composite (PZC) material. A finite element model of smart laminated truncated conical shells backed by the acoustic cavity and integrated with the patches of such ACLD treatment has been developed to demonstrate the performance of these patches for active structural-acoustic control of symmetric and antisymmetric cross-ply and antisymmetric angle-ply truncated conical laminated shells. Both velocity and pressure rate feedback control laws have been implemented to activate the patches. Particular emphasis has also been placed on investigating the effect of variation of piezoelectric fiber orientation angle in the constraining layer on the performance of the patches.

Transient response of a plate with partial constrained viscoelastic layer damping

This paper deals with the analytical modeling of a plate with partial constrained layer damping (PCLD), to obtain the harmonic and transient responses due to an impact. The governing equation is obtained from the Lagrange's equations. The stiffness of the viscoelastic core is assumed to be complex and frequency dependent. Prony series is used to account for core properties. The equation of motion is converted into the frequency domain using fast Fourier transform (FFT). Once solved, the transverse displacement obtained in the frequency domain is converted to the time domain with the inverse fast Fourier transform (IFFT). Two validations are made; the first is done in harmonic motion by comparing the natural frequencies of the plate with PCLD with results available in the literature. The second validation is done in transient response by comparing displacements to the ones obtained by an experimental set-up. Excellent agreement is noted between results. Once the model is validated, graphs of the transient response are presented and discussed.

Acoustic Radiation From Stiffened Cylindrical Shells With Constrained Layer Damping

Acoustic radiation from cylindrical shells stiffened by two sets of rings, with constrained layer damping (CLD), is investigated theoretically. The governing equations of motion for the cylindrical shell with CLD are described on the basis of Sanders thin shell theory. Two sets of rings interact with the host cylindrical shell only through the normal line forces. The solutions are derived in the wavenumber domain and the stationary phase method is used to find an analytical expression of the far-field sound pressure. The effects of the viscoelastic material core, constrained layer and multiple loadings on sound pressure are illustrated. The helical wave spectra of sound pressure and the radial displacement clearly show the vibrational and acoustic characteristics of the stiffened cylindrical shell with CLD. It is shown that CLD can effectively suppress the radial vibration and reduce acoustic radiation.

An Impedance-Based Approach for Rods With Shear-Type Damping Layer Treatment

An impedance-based approach for analyzing an axial rod with shear-type damping layer treatment is proposed. The rod and shear-type damping layer are regarded as two subsystems and both impedances are calculated analytically. The system impedance can be obtained through the impedance coupling between the host rod and the damping layer. The shear-type damping layer is regarded as a shear spring with complex shear modulus. Under the traditional model, the damping coefficient diminishes with the increasing frequency. The paper develops two shear-type damping layer models, including the single degree-of-freedom (SDOF) model and continuous model to predict the behavior of the damping layer. Both damping layer models are compared with the traditional model and the system responses from these models are validated by finite element method (FEM) code COMSOL Multiphysics. Results show that the damping coefficients of both the traditional shear-spring model and SDOF model diminish as the increasing frequency so that the system responses are discrepant with that from COMSOL in the high frequency range. On the other hand, the system response from the continuous model is consistent with that from COMSOL in the full frequency range. Hence, the continuous damping layer model can predict a correct damping coefficient in the high frequency range and this property can be also employed to improve the analysis of the constrained-layer damping treated structures. Finally, the modal loss factor and fundamental frequency of the system with respect to different damping layer thicknesses are presented using the developed approach.

Theoretical and experimental vibration analysis of rotating beams with combined ACLD and Stressed Layer Damping treatment

Active constrained layer damping (ACLD) treatment increases the efficiency of passive constrained layer damping (PCLD) treatment, but in case of circuit failure, only the decreased efficiency of PCLD treatment is available. The efficiency of the ordinary PCLD treatment can be enhanced by adding a stressed poly vinyl chloride (PVC) layers on the base beam instead of using viscoelastic materials. Hamilton Principle in conjunction with finite element method is used to derive the non-linear differential equations of motion for a rotating beam. Using proportional feedback controllers, the complex closed loop eigenvalue problem is developed and solved numerically. The effect of rotational speed of the beam, initial strain and other parameters of the PVC layer is investigated. To prove the effectiveness of the new technique, experimental investigations have also been carried out.

Coupling Analysis for a Submerged Ring-Stiffened Cylindrical Shell Treated with Active Constrained Layer Damping

Based on the previous study, the coupling analysis for a submerged active constrained layer damping (i.e. ACLD) cylindrical shell with ring ribs is developed in this paper. Firstly, the governing equation for this kind of shell is proposed. Then, a multi-virtual-point-sound-source wave function superposition method combing the transfer matrix method is proposed to obtain the acoustic pressure level. Later, numerical results are given to verify the developed method. Finally, the damping effect for the ACLD treatment on the ring-stiffened cylindrical shell is discussed.

Topology Optimization of Passive Constrained Layer Damping with Partial Coverage on Plate

The potential of using topology optimization as a tool to optimize the passive constrained layer damping (PCLD) layouts with partial coverage on flat plates is investigated. The objective function is defined as a combination of several modal loss factors solved by finite element-modal strain energy (FE-MSE) method. An interface finite element is introduced to modeling the viscoelastic core of PCLD patch to save the computational space and time in the optimization procedure. Solid isotropic material with penalization (SIMP) method is used as the material interpolation scheme and the parameters are well selected to avoid local pseudo modes. Then, the method of moving asymptote (MMA) is employed as an optimizer to search the optimal topologies of PCLD patch on plates. Applications of two flat plates with different shapes have been applied to demonstrate the validation of the proposed approach. The results show that the objective function is in a steady convergence process and the damping effect of the plates can be enhanced by the optimized PCLD layouts.

Topology Optimization of Passive Constrained Layer Damping with Partial Coverage on Plate

The potential of using topology optimization as a tool to optimize the passive constrained layer damping (PCLD) layouts with partial coverage on flat plates is investigated. The objective function is defined as a combination of several modal loss factors solved by finite element-modal strain energy (FE-MSE) method. An interface finite element is introduced to modeling the viscoelastic core of PCLD patch to save the computational space and time in the optimization procedure. Solid isotropic material with penalization (SIMP) method is used as the material interpolation scheme and the parameters are well selected to avoid local pseudo modes. Then, the method of moving asymptote (MMA) is employed as an optimizer to search the optimal topologies of PCLD patch on plates. Applications of two flat plates with different shapes have been applied to demonstrate the validation of the proposed approach. The results show that the objective function is in a steady convergence process and the damping effect of the plates can be enhanced by the optimized PCLD layouts.

SMART CONTROL OF NONLINEAR VIBRATIONS OF LAMINATED PLATES USING ACTIVE FIBER COMPOSITES

This paper deals with the geometrically nonlinear dynamic analysis of smart laminated composite plates integrated with the patches of active constrained layer damping (ACLD) treatment. The constraining layer of the ACLD treatment is made of active fiber composite (AFC) materials. The Von Kármán type nonlinear strain–displacement relations and the first-order shear deformation theory (FSDT) are adopted in deriving the coupled electromechanical nonlinear finite element (FE) model. The Golla–Hughes–McTavish (GHM) method is implemented to model the constrained viscoelastic layer of the ACLD treatment in time domain. Symmetric/antisymmetric cross-ply and antisymmetric angle-ply laminated substrate plates are considered in the numerical analyses. The results indicate that the ACLD patches significantly improve the damping characteristics of the plates for suppressing the geometrically nonlinear transient vibrations of the plates. The effects of variation of piezoelectric fiber orientation in the AFC constraining layer on the control authority of the ACLD patches have also been investigated.

Active constrained layer damping of geometrically nonlinear vibration of rotating composite beams using 1-3 piezoelectric composite

In this paper, an analysis for active constrained layer damping (ACLD) of rotating composite beams undergoing geometrically non linear vibrations has been carried out. Commercially available vertically/obliquely reinforced 1-3 piezoelectric composite (PZC) material has been used as the material of the constraining layer of the ACLD treatment. A finite element (FE) model has been derived to carry out the analysis. The substrate beam is considered thin and hence, first order shear deformation theory (FSDT) and von-Karman type nonlinear strain–displacement relations are used to derive the coupled electromechanical nonlinear FE model. The rotary effect has been suitably modelled by incorporating extensional strain energy due to centrifugal force. The Golla–Hughes–McTavish method has been employed to model the constrained viscoelastic layer of the ACLD treatment in the time domain. The numerical responses revealed that the ACLD treatment with 1-3 PZC constraining layer efficiently performs the task of active damping of geometrically nonlinear vibrations of the rotating composite beams. The effects of the fibre orientation angles of the angle-ply substrate beams and the 1-3 PZC constraining layer on the ACLD of the geometrically nonlinear vibrations have been investigated. Also, the effect of the thickness variations of the 1-3 PZC layer and the viscoelastic constrained layer on the damping characteristics of the overall rotating composite beams has been studied.

Active damping of laminated cylindrical shells conveying fluid using 1–3 piezoelectric composites

In this paper, the performance of the active constrained layer damping (ACLD) treatment for active control of thin laminated cylindrical shells conveying fluid has been investigated. The constraining layer of the ACLD treatment has been considered to be made of vertically or obliquely reinforced 1–3 piezoelectric composite (PZC) materials. A three-dimensional finite element model has been developed for the laminated shells integrated with the patches of ACLD treatment to describe the coupled hydroelastic behavior of the shells. Velocity feedback control law has been implemented to activate the patches. Symmetric and antisymmetric cross-ply and antisymmetric angle-ply shells have been considered for evaluating the numerical results. Emphasis has also been placed on investigating the effect of the variation of the piezoelectric fiber orientation angle in the PZC constraining layer on the performance of the patches.

Application of level set method to optimal vibration control of plate structures

Vibration control plays a crucial role in many structures, especially in the lightweight ones. One of the most commonly practiced method to suppress the undesirable vibration of structures is to attach patches of the constrained layer damping (CLD) onto the surface of the structure. In order to consider the weight efficiency of a structure, the best shapes and locations of the CLD patches should be determined to achieve the optimum vibration suppression with minimum usage of the CLD patches. This paper proposes a novel topology optimization technique that can determine the best shape and location of the applied CLD patches, simultaneously. Passive vibration control is formulated in the context of the level set method, which is a numerical technique to track shapes and locations concurrently. The optimal damping set could be found in a structure, in its fundamental vibration mode, such that the maximum modal loss factor of the system is achieved. Two different plate structures will be considered and the damping patches will be optimally located on them. At the same time, the best shapes of the damping patches will be determined too. In one example, the numerical results will be compared with those obtained from the experimental tests to validate the accuracy of the proposed method. This comparison reveals the effectiveness of the level set approach in finding the optimum shape and location of the CLD patches.