Constrained Layer Damping Research Articles

Multiobjective optimization for vibration reduction in composite plate structures using constrained layer damping

This paper presents a multiobjective optimization approach to minimize weight and maximize modal damping in laminated composite panels with Constrained Layer Damping (CLD) treatments. The design variables are the number and position of the CLD patch treatments on the surface of the laminated plate. The Direct MultiSearch (DMS) solver for multiobjective optimization problems is used in this work. DMS is a solver which does not use any derivatives of the objective functions. A previously developed finite element model for sandwich plates with viscoelastic core and anisotropic laminated face layers is adapted to model the plate with the CLD treatments. Applications for L-shaped and T-shaped plates are presented and both trade-off Pareto optimal fronts and the respective treatment configurations are obtained and the results are analyzed and discussed.

Control of large amplitude vibrations of doubly curved sandwich shells composed of fuzzy fiber reinforced composite facings

This paper is concerned with the analysis of active constrained layer damping (ACLD) of geometrically nonlinear vibrations of doubly curved sandwich shells with facings composed of fuzzy fiber reinforced composite (FFRC). FFRC is a novel composite where the short carbon nanotubes (CNTs) which are either straight or wavy are radially grown on the periphery of the long continuous carbon fiber reinforcements. The plane of waviness of the CNTs is coplanar with the plane of carbon fiber. The constraining layer of the ACLD treatment is composed of the vertically/obliquely reinforced 1–3 piezoelectric composites (PZCs) while the constrained viscoelastic layer has been sandwiched between the substrate and the PZC layer. The Golla–Hughes–McTavish (GHM) method has been implemented to model the constrained viscoelastic layer of the ACLD treatment in time domain. A three dimensional finite element (FE) model of smart doubly curved FFRC sandwich shells integrated with ACLD patches has been developed to investigate the performance of these patches for controlling the geometrically nonlinear vibrations of these shells. This study reveals that the performance of the ACLD patches for controlling the geometrically nonlinear vibrations of the doubly curved sandwich shells is better in the case of the facings composed of laminated FFRC than that in the case of the facings made of conventional orthotropic laminated composite. The research carried out in this paper brings to light that even the wavy CNTs can be properly utilized for attaining structural benefits from the exceptional elastic properties of CNTs.

Analysis of smart damping of laminated composite beams using mesh free method

This paper is concerned with the development of mesh free model for the performance analysis of active constrained layered damping (ACLD) treatments on smart laminated composite beams. The overall structure is composed of a substrate laminated composite beam integrated with a viscoelastic layer and a piezoelectric layer attached partially or fully at the top surface of the substrate beam. The piezoelectric layer acts as the active constraining layer of the smart beam and the viscoelastic layer acts as the constrained layer. A layer wise displacement theory has been used to derive the models. Both symmetric cross-ply and antisymmetric angle-ply laminated beams are considered for the numerical analysis. It is observed that ACLD treatment significantly improves the active damping properties of the substrate beam. The numerical results also reveal that the triangular ACLD treatment is more effective than the rectangular ACLD treatment of same thickness and volume for active damping of smart composite beams.

Formulating a numerically low-cost method of a constrained layer damper for vibration suppression in thin-walled component milling and experimental validation

Due to its low stiffness and time-varying modal parameters, thin-walled workpiece milling is still a challenging problem. In order to reveal the influence of the relative position between the cutter and workpiece on the dynamic response of the flexible thin-walled component, and optimize the parameters of the constrained layer damper applied to suppress the machining vibration in thin-walled workpiece peripheral milling process, with assumption of chatter-free milling operation, a dynamic model of thin plate peripheral milling with constrained layer damper subjected to moving cutting force using Lagrange equation is proposed based on the first shear deformation theory. Considering the complexity and variability of the boundary conditions of workpiece in practical machining processes, a mixed Rayleigh-Ritz solution together with Courant's penalty method and differential quadrature method is presented to evaluate the damping performance and dynamic response. Courant's penalty method is used to handle the complex and changing boundary conditions, Rayleigh-Ritz method is employed to deal with the spatial partial derivatives, and differential quadrature method is applied to treat the temporal derivatives. The influence of the relative position between cutter and workpiece on dynamic response is investigated, and the response of milling position are calculated using presented technique and compared with the results measured through milling tests. The results show that an acceptable agreement between numerical and experimental results can be obtained and the present technique is efficient to estimate the dynamic response of thin plate milling. Additionally, the parametric study of constrained layer damper is performed through evaluating the root-mean-square of response, and the results can be used to optimize the parameters of the constrained layer damper for suppressing machining vibration and improving surface finish accuracy.

Experimental investigations on a light-weight aerogel layer in gypsum wallboards for increased sound transmission loss

It has long been considered challenging to increase sound transmission loss of gypsum wallboards without significantly increasing the board thickness and weight. Low-density highly porous solid monolithic macroscopic objects consisting of hierarchical mesoporous three-dimensional assemblies of nanoparticles (aerogels) are pursued mainly for their low thermal conductivity. Unlike classical aerogels of the most common kind based on silica being fragile materials, structural fragility issue has been addressed successfully with materials referred to as polymer-crosslinked (or X-) aerogels. X-aerogels are very low-density materials, yet their mechanical strengths have been significantly increased. This work explores ductile aerogels in potential uses as constrained damping layers integrated into gypsum wallboards. Due to their ductility and mechanical strength, light weight X-aerogel panels of less than 1 cm in thickness can be conveniently integrated into gypsum wallboards. The objective of this work is to develop integrated wallboards to achieve significantly increased sound transmission loss without significantly increasing thickness and weight of integrated wallboard system. This paper discusses preliminary test results carried out in chamber-based random-incident measurements, and further exploration on broadband dynamic properties of X-aerogels for better understanding of its excellent effect in drastically increased sound transmission loss.

Inverse Identification of the Frequency-Dependent Mechanical Parameters of a Viscoelastic Core Layer Based on the Vibration Response

The identification of the mechanical parameters of the viscoelastic core layer is of great significance for the modeling and damping design of the constrained layer damping (CLD) composite structure. In this study, based on the measured frequency vibration response of a CLD plate, an inverse approach was developed to identify the aforementioned parameters. Then, on the basis of considering both the viscoelastic material damping and the remaining equivalent viscous damping, the equation of motion of the CLD plate under base excitation was established and a method to obtain the vibration response was also presented. Further, a matching calculation based on sensitivity was proposed, to achieve the identification of the mechanical parameters. Finally, a CLD aluminum plate with a ZN_1 viscoelastic core layer was chosen to demonstrate the proposed method. In addition, the identification results were also introduced into the vibration response analysis and the rationality of the identified parameters were verified by comparing the vibration responses obtained by theoretical calculations and the experiment.

Flexural wave attenuation in a sandwich beam with viscoelastic periodic cores

The flexural-wave attenuation performance of traditional constraint-layer damping in a sandwich beam is improved by using periodic constrained-layer damping (PCLD), where the monolithic viscoelastic core is replaced with two periodically alternating viscoelastic cores. Closed-form solutions of the wave propagation constants of the infinite periodic sandwich beam and the forced response of the corresponding finite sandwich structure are theoretically derived, providing computational support on the analysis of attenuation characteristics. In a sandwich beam with PCLD, the flexural waves can be attenuated by both Bragg scattering effect and damping effect, where the attenuation level is mainly dominated by Bragg scattering in the band-gaps and by damping in the pass-bands. Affected by these two effects, when the parameters of periodic cores are properly selected, a sandwich beam with PCLD can effectively reduce vibrations of much lower frequencies than that with traditional constrained-layer damping. The effects of the parameters of viscoelastic periodic cores on band-gap properties are also discussed, showing that the average attenuation in the desired frequency band can be maximized by tuning the length ratio and core thickness to proper values. The research in this paper could possibly provide useful information for the researches and engineers to design damping structures.

Vibration and damping analysis of aerospace pipeline conveying fluid with constrained layer damping treatment

The constrained layer damping materials are thoroughly used to control the vibration duo to their high capacity to dissipate vibration energy. Researchers have handled the vibration and damping behavior of the constrained layer damping structures accurately. However, for the constrained layer damping pipeline conveying fluid, there are few works on the investigation of the vibration characteristics. This paper is aimed to investigate the vibration and damping characteristics of the constrained layer damping pipeline conveying fluid under elastic boundary supports. Considering the fluid–structure interaction, the developed finite element method is employed to establish the motion equations of the constrained layer damping pipeline. The influence of the support stiffness, the fluid velocity and pressure, the thickness and the elasticity modulus of viscoelastic, and constraining layer parameters are all considered. The results indicate that an appropriate selection of the boundary support stiffness, the viscoelastic, and constraining layer parameters can obtain desirable modal properties, which can provide an efficient tool in the design and maintenance of aerospace pipeline for passive vibration control.

Dynamic Optimization of Constrained Layer Damping Structure for the Headstock of Machine Tools with Modal Strain Energy Method

Dynamic stiffness and damping of the headstock, which is a critical component of precision horizontal machining center, are two main factors that influence machining accuracy and surface finish quality. Constrained Layer Damping (CLD) structure is proved to be effective in raising damping capacity for the thin plate and shell structures. In this paper, one kind of high damping material is utilized on the headstock to improve damping capacity. The dynamic characteristic of the hybrid headstock is investigated analytically and experimentally. The results demonstrate that the resonant response amplitudes of the headstock with damping material can decrease significantly compared to original cast structure. To obtain the optimal configuration of damping material, a topology optimization method based on the Evolutionary Structural Optimization (ESO) is implemented. Modal Strain Energy (MSE) method is employed to analyze the damping and to derive the sensitivity of the modal loss factor. The optimization results indicate that the added weight of damping material decreases by 50%; meanwhile the first two orders of modal loss factor decrease by less than 23.5% compared to the original structure.

Optimization of Constrained Layer Damping Parameters in Beam Using Taguchi Method

This paper presents a study in which an attempt has been made to find out the maximum damping capacity of passive constrained layer damping treatments by optimizing the parameters of the treatment using the Taguchi method. Passive constrained layer damping treatment is one where two layers such as viscoelastic layer and constraining layer are attached on the surface of the structure so as to enhance the damping capacity of the structure. The performance of the constrained layer damping (CLD) parameters is evaluated in terms of its thickness of viscoelastic, constraining layer and coverage of the treatment over the surface of the beam. An orthogonal array, main effect, signal-to-noise ratio and analysis of variance are employed to analyze the effect of CLD parameters on the damping behavior and first natural frequency. The analysis of the results gives the optimal combination of thicknesses of different layers and coverage area of the treatment. Finally, it is demonstrated by conducting confirmation experiments that the predicted results obtained using regression equations are consistent with experimental observations.

Free Vibration Analysis of various Viscoelastic Sandwich Beams

Background/Objectives: Constrained Layer Damping (CLD) is an effective passive damping technique to suppress the vibrations using to analyze the vibration behaviour of viscoelastic sandwich beams. A Sandwich beam contains two face layers at top and bottom, one core layer of viscoelastic material. Methods/Statistical Analysis: In this paper free vibration analysis has been carried out on various viscoelastic sandwich beams likes Al-NR-Al, Al-NeR-Al, MS-NRMS and MS-NeR-MS under four edge conditions viz., clamped-free, clamped - clamped, clamped-simply supported and simply supported-simply supported. Analytical solutions are to be carried out using Euler-Bernoulli’s theory and Newton- Raphson method has to be adopted to investigate the natural frequencies of various sandwich beams. Findings: The beam’s natural frequencies for different mode numbers with face material as aluminium and core as polyurethane rigid for analysis of fixed free sandwich beam and observed that as mode number increases natural frequencies increases due to non dimensional number increases. And found that the higher natural frequencies obtained for clamped-clamped condition of Al-NR-Al sandwich model for various edge conditions such as conditions like clamped-free, clamped - clamped, clamped -SS and SS-SS. As mode numbers increase the modal behaviour shows diverging nature because of the effect of eigenvalue. The maximum percentage variation in natural frequency from fixed-fixed and fixed-free condition is 26.35. Improvements: The higher natural frequencies are obtained when mild steel is used as face material. The natural frequencies were reduced when neoprene rubber was used as core material.

Highly efficient continuous bistable nonlinear energy sink composed of a cantilever beam with partial constrained layer damping

This paper focuses on the transient nonlinear dynamics and targeted energy transfer (TET) of a Bernoulli–Euler beam coupled to a continuous bistable nonlinear energy sink (NES). This NES comprises a cantilever beam with the partial constrained layer damping (PCLD) and an end mass controlled by a nonlinear magnetostatic interaction force. The theoretical model of the nonlinear system is built based on the Lagrange equations and assumed-modes expansion method. A new parameter system damping ratio is proposed to evaluate the TET efficiencies. Impact experiments are carried out to verify the theoretical model and mechanisms. The results show that the bistable NES can achieve high and strongly robust TET efficiencies under broad-range impacts. The shear modulus of the viscoelastic layer, the length of the PCLD and the end mass have significant influences on TET efficiencies. Analyses of the TET mechanisms in the bistable NES show the following: steady transition of the stable state is an important reason for maintaining high TET efficiencies; nonlinear beatings can occur in high-frequency, fundamental and long-period subharmonic branches; and resonance captures featuring fundamental and subharmonic also help achieve rapid energy dissipation.

Smart damping of geometrically nonlinear vibrations of composite shells using fractional order derivative viscoelastic constitutive relations

ABSTRACTIn this article, a three-dimensional fractional order derivative model has been developed for the constrained viscoelastic layer of the active constrained layer damping (ACLD) treatment of laminated composite shells undergoing geometrically nonlinear vibrations. The constraining layer of the ACLD treatment is made of vertically/obliquely reinforced 1–3 piezoelectric composites and acts as the distributed actuator. A three-dimensional smart nonlinear finite element model has been developed. Several numerical results are presented to check the accuracy of the present three-dimensional fractional derivative model of the constrained viscoelastic layer for smart damping of geometrically nonlinear vibrations of laminated composite shells.

Multiobjective optimization of constrained layer damping treatments in composite plate structures

ABSTRACTThe optimal design of laminated composite panels with constrained layer damping (CLD) treatments is addressed in this article. The objectives are simultaneously to minimize weight and maximize modal damping. The design variables are the number and position of CLD patch treatments on the surface of the laminated plate. The problem is solved using Direct MultiSearch solver, which does not use any derivatives of the objective functions. A finite element model for sandwich plates with viscoelastic core and laminated face layers is used. Trade-off Pareto optimal fronts and the respective treatment configurations are obtained and the results are analyzed and discussed.

A design of active constrained layer damping treatment for vibration control of circular cylindrical shell structure

A new 1-3 viscoelastic composite material (VECM) layer is designed for improved active constrained layer damping (ACLD) treatment of vibration of a functionally graded (FG) circular cylindrical shell. Besides this improved active damping treatment, another objective of this study is to control all the modes of vibration of the shell effectively using the treatment (active constrained layer damping) in layer-form throughout the outer shell-surface. In this design of active constrained layer damping treatment in layer-form, its (active constrained layer damping) necessary conformability with the curved host shell-surface is ensured by the use of a vertically reinforced 1-3 piezoelectric composite (PZC) constraining layer, whereas the effective control of several modes of vibration of the shell is achieved by the use of electrode-patches over the surfaces of the constraining layer. A fruitful strategy in the arrangement of electrode-patches is proposed for effective control of several modes of vibration of the shell using one configuration of the electrode-patches. An electric potential function is assumed for this use of electrode-patches and a geometrically nonlinear coupled electro-visco-elastic incremental finite element model of the overall shell is developed for its analysis in the frequency-domain. The analysis reveals significant improvement of active damping characteristics of the active constrained layer damping layer for the use of the present 1-3 viscoelastic composite material layer instead of the traditional monolithic viscoelastic material (VEM) layer. The analysis also reveals the suitability of the present strategy of arrangement of electrode-patches for achieving aforesaid control-activity of the ACLD layer. The effects of temperature in the host functionally graded shell and different geometric parameters in the design of the 1-3 viscoelastic composite material layer on the damping characteristics of overall shell are also presented.

Experimental study on the influence of modal parameters of thin cylindrical shell coated with constrained layer damping

This research has experimentally investigated on the influence on modal parameters of thin cylindrical shell coated with constrained layer damping (CLD). Firstly, based on vibration behavior of thin walled shell structure, an experiment system is established to measure modal parameters of the shell with high accuracy and efficiency, and the corresponding test methods and identification techniques which are suitable for the shell coated with CLD are proposed. Then, the shell is coated with different numbers and sizes of CLD pieces or in different coating positions of CLD rings, and modal parameters are obtained by the proposed test method. Finally, based on the accurate measured data, the influence on natural frequencies, mode shapes and damping ratios of TCS coated with CLD are analyzed and discussed in details. This research can provide technical support for CLD application on thin walled shell structure.

Design of a 1-3 viscoelastic composite layer for improved free/constrained layer passive damping treatment of structural vibration

Abstract A new 1-3 viscoelastic composite material (VECM) layer is designed in order to achieve improved passive damping characteristics of the unconstrained (UCLD)/constrained (PCLD) layer damping treatment of structural vibration. The present 1-3 VECM layer is used instead of traditional monolithic viscoelastic material (VEM) layer within the UCLD/PCLD treatment. The corresponding change in damping is studied through the static as well as dynamic finite element (FE) analyses of a substrate beam integrated with the UCLD/PCLD treatment. The static analysis reveals augmentations of damping in the use of 1-3 VECM layer. The dynamic analysis quantifies improvement in the passive unconstrained/constrained layer damping through the present design.

Transient and harmonic response of a sandwich with partial constrained layer damping: A parametric study

The aim of this paper is to present a parametric study of PCLD (partial constraining layer damping) characteristics on the response of a rectangular plate. Both harmonic and transient regimes are considered. In harmonic response, natural frequencies and loss factors are studied, while in transient response, where the external force is an impact, displacement and acoustic pressure are analyzed. The governing equation is obtained from Lagrange's equations. The viscoelastic behaviour of the core, which depends on frequency, is represented by Prony series. Once obtained, the governing equation is solved in frequency domain using Fast Fourier Transform (FFT). The solution is then converted back into time domain with the Inverse Fast Fourier Transform (IFFT). The model was validated in our previous paper, Ref. [B. Khalfi and A. Ross, “Transient Response of A Plate With Partial Constrained Viscoelastic Layer Damping,” International Journal of Mechanical Sciences, http://dx.doi.org/10.1016/j.ijmecsci.2013.01.032, 2013] with experimental results, in this paper other validation with literature using a plate with PCLD is also made. The simulation results show that patch geometry has a significant effect on the vibration behaviour of the sandwich. Several conclusions were obtained: (a) Identification of the proportions of different layer thickness for optimal damping, (b) Definition of areas in the plate promoting maximum shear in the viscoelastic layer, (c) Existence of a relationship between loss factor and deformation mode. The originality of this work comes from the capacity of the model to study the influence of any input parameter on the behaviour of the sandwich in harmonic response as well as in transient response.

Smart damping of geometrically nonlinear vibrations of functionally graded sandwich plates using 1–3 piezoelectric composites

ABSTRACTGeometrically nonlinear dynamic analysis of smart functionally graded (FG) sandwich plates integrated with the patches of active constrained layer damping (ACLD) treatment has been carried out by the finite element method. The constraining layer of the ACLD treatment is considered to be made of vertically/obliquely reinforced 1–3 piezoelectric composite while the constrained layer is made of a viscoelastic material, which is modeled using the Golla–Hughes–McTavish method in the time domain. The top and bottom faces of the substrate sandwich plate are composed of the FG isotropic material whose mechanical properties are assumed to vary according to a standard power-law distribution in terms of the volume fractions of the constituents while the core layer may be either a soft honeycomb material or a hard ceramic material. Several FG sandwich plates with different core configurations are studied to evaluate the numerical results. The numerical results indicate that the ACLD patches significantly improve the damping characteristics of the FG sandwich plates for suppressing their geometrically nonlinear vibrations. Effects of metal- or ceramic-rich top and bottom surfaces, the variation of power-law index on the control authority of the ACLD patches have been investigated. Emphasis has also been placed on investigating the effect of the variation of piezoelectric fiber orientation angle on the performance of the ACLD patches.

Vibration Characteristics of Journal Bearing with Various Damping Materials

This paper presents an overview of the vibration problems which are experienced in running journal bearing. High vibration levels in machinery and components are usually undesirable as they often generate excessive noise and can lead to cyclic fatigue damage. The drive to reduce component mass, particularly in the aerospace and automotive industries, makes items more susceptible to vibration problems. In addition, many new high strength/high stiffness designs rely on ‘single piece’ welded metallic or fibrous composite constructions that have very little inherent damping. Damping materials have long been used to reduce vibration levels - examples vary from optimized constrained layer dampers on aircraft panels to bitumen spread on the underside of a metallic kitchen sink. Initially, most damping materials used were polymers with viscoelastic characteristics. In this work, a bearing testing apparatus is used for experimental studies to obtain displacement, velocity and acceleration from a journal bearing. Journal bearings are widely used to support the shaft of industrial machinery with heavy loads, such as compressors, turbines and centrifugal pumps. Vibration as a consequence of improper damping materials in journal bearing results in economic loss and creates high safety risks. So, it is necessary to reduce vibrations by selecting appropriate damping materials to the journal bearing and to achieve cost benefits to industry. Plywood, fibre, butadiene rubber and mud flap rubber was used to dampen the vibrations in the journal bearing. From the results, it is shown that the mud flap rubber possesses very good damping characteristics for journal bearing applications.