Constrained Layer Damping Research Articles

Rolling noise minimization for railway wheels with constrained layer damping treatments

The present work analyses the reduction of the radiated rolling noise by a Constrained Layer Damping (CLD) mounted on the railway wheel. For this purpose, a methodology has been developed combining the use of viscoelastic models that consider the dependence of the material properties on frequency with an integral vibroacoustic model of the wheel. The CLD device, composed by a layer made of a viscoelastic material constrained towards the web by a steel layer positioned on the top, is characterised by design parameters considered relevant for sound radiation. The sound power level (SWL) is computed for different configurations of CLDs on the wheel to find the optimal designs for rolling noise minimisation.

Sound transmission loss of constrained layer damping composites featuring elastic plates embedded with acoustic black hole

This paper preliminarily investigates the influence of an elastic layer with an acoustic black hole (ABH) on the airborne sound insulation of a constrained layer damping (CLD) composite plate. ABHs represent a continuous impedance reduction in a local area of the structure, achieved by reducing material thickness. They efficiently dampen structure-borne sound in plate-like structures, resulting in excellent airborne sound attenuation performance. In the CLD composite structure, a damping layer is inserted between the elastic layers. This configuration achieves noise reduction and provides excellent airborne sound attenuation performance. By incorporating an ABH on one side of the elastic layer within the constrained damping composite structure and utilizing the damping layer as the terminal damping material for ABH, we achieve a lightweight structure with outstanding airborne sound insulation performance. Using finite element numerical calculations, we assess the airborne sound transmission loss of ABHs embedded within the CLD plate. Our analysis compares their transmission losses within the frequency range of 10 to 4000 Hz under normal-incidence and random incidence acoustic field excitations. While the ABH does not enhance the overall sound isolation performance of the CLD plate, it significantly improves the sound isolation dip at the resonance frequency.

Iterative eigenvalue method coupled with RSM for structural acoustic analysis and optimization of the CLD-damped orthotropic steel deck

In the present work, an iterative eigenvalue method (IEM) is proposed and combined with the boundary element method (BEM) to perform the structural acoustical analysis of the orthotropic steel deck (OSD) damped with constrained layer damping (CLD), through which the frequency-dependent properties of the viscoelastic core can be accurately considered. Then, a series of hammer tests are carried out in a semi-anechoic chamber to verify the acoustic prediction method. It shows that the simulated structural noises basically agree with the test results, and the overall deviations at the field points M2 and M8 are merely 2.4 and 2.3 dB, respectively. Subsequently, taking the thicknesses of the damping layer and the constraining layer, as well as the material properties of the constraining layer as design variables, a central composite experiment is designed and combined with response surface methodology (RSM) to fit the relationship between analysis objectives and design variables. With the objective of minimizing the acoustic radiation power, a program for finding the optimal values of design variables is developed based on the interior penalty function method. Through iterative computations, the optimal points are numerically determined as t 1 = 2.3 mm and t 2 = 0.3 mm for the thicknesses of the damping layer and the constraining layer, respectively. Steel alloy is found to be the optimal material for the constraining layer. After optimizing CLD treatment, the overall acoustical power level can be reduced from 97.7 dB to 93.1 dB and the overall sound pressure levels (SPLs) at the field points M2 and M8 can be reduced from 89.2 dB to 83.5 and 76.9 dB to 70.3 dB, respectively, indicating that the optimization of CLD design parameters can significantly improve acoustic performance of the CLD-damped structures.

Active Vibration Control and Parameter Optimization of Genetic Algorithm for Partially Damped Composites Beams.

The paper partially covered Active Constrained Layer Damping (ACLD) cantilever beams' dynamic modeling, active vibration control, and parameter optimization techniques as the main topic of this research. The dynamic model of the viscoelastic sandwich beam is created by merging the finite element approach with the Golla Hughes McTavish (GHM) model. The governing equation is constructed based on Hamilton's principle. After the joint reduction of physical space and state space, the model is modified to comply with the demands of active control. The control parameters are optimized based on the Kalman filter and genetic algorithm. The effect of various ACLD coverage architectures and excitation signals on the system's vibration is investigated. According to the research, the genetic algorithm's optimization iteration can quickly find the best solution while achieving accurate model tracking, increasing the effectiveness and precision of active control. The Kalman filter can effectively suppress the impact of vibration and noise exposure to random excitation on the system.

Damping optimization of a fully viscoelastic structure with enforced mass reduction

Current damping methods employed in industry, such as Constrained Layer Damping (CLD), all require the introduction of additional mass and a secondary material to the structure. In transportation industries, this weight addition is often correlated with an increase in operational costs. Additionally, in applications with large temperature changes, such as in space, the secondary material introduces an additional source of stress during thermal expansion and contraction. This work presents a methodology to significantly improve the damping performance of a fully viscoelastic, single material structure while also enforcing a mass reduction. The work expands upon the modal strain energy (MSE) method to calculate the damping performance of a fully viscoelastic structure and develops a novel weighting scheme to make the optimization more robust. The methodology is then implemented on a technology demonstration thermoplastic lunar rover. This implementation demonstrates the ability to optimize a fully viscoelastic structure to significantly improve the damping performance while also achieving a large decrease in mass. The implementation also demonstrates the robustness of the weighting scheme as it allows the natural frequencies to shift between iterations. The skin thickness of the rover’s base panel was optimized. After optimization, the base panel of the rover achieved a 20% damping improvement for Mode 1 with a 9% mass reduction. The skin thickness of the full rover was optimized and achieved a 15% damping improvement for Mode 2 with an 11% mass reduction.

Active Constrained Layer Damping of Beams with Natural Fiber Reinforced Viscoelastic Composites

Abstract Viscoelastic composite reinforced with natural fibers is proposed here for the damping treatment of structures for vibration attenuation. The constrained layer damping (CLD) method is found a prominent structural vibration damping method and as a result of the inclusion of natural fiber, substantial damping could be achieved due to the development of shear as well as extensional strains in the viscoelastic material. Finite element analysis of a substrate beam combined with CLD treatment is used to investigate the corresponding improvement in damping. The influence of various geometry of presently considered natural viscoelastic composite layers on the CLD treatment's damping performance has been evaluated and discussed. Damping performances of natural as well as synthetic fibers have been assessed and compared for using natural fibers in viscoelastic composite for various structural applications. The addition of natural fiber has resulted from enhanced damping capacity due to substantial friction at the natural fiber-matrix interface compared to the case of interface with synthetic fiber. Natural fiber attributes less stiffness and a higher loss factor as compared to synthetic fiber and the insertion of stiff fibers affects the polymer chain's movements, decreasing the matrix phase's damping behavior. The dynamic mechanical analysis test is performed to evaluate the damping characteristics in the form of loss factor, storage, and loss modulus over the temperature range from frozen state to melting state.

Substructure-based topology optimization design method for passive constrained damping structures

Abstract This work presents a generalized substructure-based topology optimization method for passive constrained layer damping (PCLD) structures. Here, the model of PCLD structure is obtained by the Kirchhoff–Love thin plate formulation, and the whole structure is assumed to be composed of substructures with different yet connected scales and artificial lattice geometry features. Each substructure is condensed into a super-element to obtain the associated density-related matrices under the different geometry feature parameters, and the surrogate model for the stiffness and mass matrix of PCLD substructures with different densities has been particularly built. Using cubic spline interpolation, the derivatives of super-element matrices to the associated densities can be evaluated efficiently and accurately. The modal loss factor is defined as objective functions and topology optimization for the PCLD structures is formulated based on the model for PCLD plates that are described by combining the condensed substructures. Numerical examples under two lattice patterns of substructures and their corresponding physical tests show that the correctness and superiority of this substructure-based topology optimization approach for PCLD plates are verified.

Experimental Investigation of Damping Properties of Selected Polymer Materials.

This paper presents the results of an experimental modal analysis of a beam covered by polymer materials used as a passive vibration isolation. The main aim of this study was to determine the damping properties of selected viscoelastic materials. In order to check the damping properties of tested materials, an experimental modal analysis, with the use of an electrodynamic vibration system, was performed. In this study, four kinds of specimens were considered. In the first step of the work, the beam made out of aluminum alloy was investigated. Afterwards, a cantilever beam was covered with a layer of bitumen-based material acting as a damper. This method is commonly known as a free layer damping treatment (FLD). In order to increase the damping capabilities, the previous configuration was improved by fixing a thin aluminum layer directly to the viscoelastic core. Such a treatment is called constrained layer damping (CLD). Subsequently, another polymer (butyl rubber) in the CLD configuration was tested for its damping properties. As a result of the performed experimental modal analysis, the frequencies of resonant vibrations and their corresponding amplitudes were obtained. The experimental results were used to quantitatively evaluate the damping properties of tested materials.

Dynamic topology optimization of two-phase viscoelastic composite structures considering frequency- and temperature-dependent properties under random excitation

This article proposes an efficient optimum design method of constrained layer damping (CLD) plates characterized by non-proportional damping subjected to random excitation. Considering frequency and temperature dependence, a two-phase viscoelastic composite material composed of stiffness-phase and damping-phase materials is used as the damping layer. The pseudo excitation and hybrid expansion methods are adopted to compute the random responses at the specified frequency intervals as the objective functions. The sensitivity analysis is performed through the adjoint vector method. The similarity index is defined to distinguish the various optimal layouts quantitatively. Several numerical examples clearly demonstrate the robustness and effectiveness of the proposed method, highlighting a remarkable improvement of over 60% in computational efficiency. Furthermore, it is proved that, when subjected to broadband random excitation, the damping materials' temperature- and frequency-dependent properties are critical factors in obtaining accurate vibration responses and desirable optimal layouts. The effects of the layer thicknesses and volume fractions of composite structures on topology optimization are also discussed. The results indicate that both layer thickness and volume fraction can change the mechanical properties of the composite structure and further affect the distribution characteristics of the damping material.

Enhancing sound insulation performance with active constrained layer damping plates at low frequencies

In this paper, the normal incident sound transmission loss characteristics of active constrained layer damping (ACLD) plates are investigated numerically and experimentally. The sound insulation performance of the ACLD plate configuration with a centrally positioned 30 mm × 30 mm patch is initially examined in both passive and active control states. The analog feedback control strategy is employed to physically demonstrate that the ACLD treatment can effectively improve airborne sound insulation performance at low frequencies. To enhance control efficiency and mitigate control spillover effects, an edge-enhanced ACLD (EACLD) plate configuration is proposed, which enables a direct electrical connection between the PZT layer and base plate. Control mechanism is further analyzed from the perspectives of mean quadratic normal velocity and deformed modal shapes. Results show that, in the passive state, the formation of sound insulation peaks of the ACLD and EACLD plate configurations are attributed to structural anti-resonance effects. By applying active control, the shear deformation degree of the viscoelastic layer can be further increased, and the advantages of active and passive hybrid damping are formed. Therefore, the sound insulation performance of the EACLD plate configuration in the first-order resonance region around 190 Hz can be enhanced by approximately 20 dB. The proposed EACLD plate configuration demonstrates a broad low-frequency sound insulation bandwidth and holds strong potential for engineering applications.

Effect of metallic substrate and rubber elastic materials over passive constrained layer damping on tool vibration during boring process

Tool vibration is a key factor that affects surface finish, generates noise, and reduces the tool life during conventional boring because of the excessive overhanging length of the tool holder. The interaction between the dynamics of the machine tool and the boring process led to progressive vibration. The creation of appropriate mechanisms in reducing tool vibration will help manufacturing industries to become more productive. In this research, in order to control vibration in the overhanging boring bar, a passive vibration control method was employed. Constrained layer dampers consist of boring bar, substrate, and elastic materials and it is used to minimize tool vibration produced during boring operation. The investigation utilized computational analysis through the ANSYS Workbench platform, employing key parameters such as the overhanging length of the tool holder (100, 150, and 200 mm), substrate material (aluminum, brass, and copper), and elastic material (Nitrile rubber, Natural rubber, and polyurethane). A comprehensive series of 27-run boring experiments were conducted to assess the impact of the constrained layer damper on tool vibration and cutting properties. The results of the study revealed remarkable improvements in various performance metrics. The constrained layer damper demonstrated an impressive 98% reduction in tool vibration, signifying its efficacy in dampening vibrational forces during the boring operation. Furthermore, a substantial 83% decrease in surface roughness was observed, indicating enhanced machining precision and surface finish. The constrained layer damper also exhibited a noteworthy 97.5% reduction in tool wear, highlighting its ability to significantly prolong tool life under challenging machining conditions.

A rapid prediction model for the radiation efficiency of baffled constrained layer damping plate

It’s well-known that constrained layer damping (CLD) can effectively reduce the vibration and radiation noise from the (plate-like or shell-like) thin-walled structures under various of dynamic excitations. As one of the key properties deciding the CLD’s performance, the CLD’s acoustic radiation characteristics has always been a focus of researchers. In this study, an analytical model based on equivalent principle is proposed to predict the acoustic radiation efficiency of the CLD plate. In this model, a laminated CLD plate is equivalent to a single-layer plate and the equivalent stiffness and loss factor are obtained using the strain energy method. The vibration velocity of the plate is calculated using mode-superposition method and the sound pressure on the plate surface is calculated using Rayleigh integral formula. Variable mesh sizes and frequency steps are employed to improve the calculation efficiency. The difference between the base and CLD plates in sound radiation characteristics is investigated using this model. The results indicate that CLD involving a damping layer with a low Young’s modulus can mitigate more vibration at low frequencies. A higher Young’s modulus of the damping layer results in a higher radiation efficiency of the CLD plate between the fundamental and critical frequencies. By increasing the loss factor, the spatially averaged mean square velocity would decrease, more modes would contribute to the response, and the CLD plate can consequently achieve a higher radiation efficiency below the critical frequency. Moreover, the simplified formulae for the average radiation efficiency of the CLD plate is developed to achieve the rapid calculation. Its accuracy is then validated by comparing the results to the more comprehensive model.

Enhancing Structural Vibration Damping in Marine Machinery: A Comprehensive Numerical Investigation with Modal and Harmonic Analysis

This article presents a comprehensive study on the damping of vibrations in a motor-pump assembly using viscoelastic and constrained layer damping treatments. The assembly's structural model, designed using SolidWorks software, is subjected to modal and harmonic analyses in ANSYS. The primary goal is to mitigate vibration amplitudes originating from the motor and pump to enhance the assembly's operational performance. Three damping treatments are investigated: Free Layer Damping (FLD), Sandwich Constrained Layer Damping (CLD), and a novel Multilayer CLD approach. The viscoelastic material is modeled using the Prony series method, and its properties are incorporated into the finite element analysis Results demonstrate that the application of damping treatments significantly reduces vibration amplitudes compared to the untreated structure. Among the treatments, the Multilayer CLD approach exhibits the highest damping efficiency, reducing the maximum amplitude by approximately 52% compared to the base structure. The study showcases the advantages of utilizing viscoelastic and constrained layer damping techniques for enhancing vibration control and operational stability in industrial assemblies. The research findings contribute to the field of structural dynamics and vibration control, offering valuable insights into the design and optimization of mechanical systems subjected to dynamic loads. This study opens avenues for further research and practical applications aimed at improving the performance and reliability of motor-pump assemblies and similar industrial equipment.

Vibration Properties of Submerged Sandwich Cylindrical Shell Based on Wave Propagation Approach: Analytical and Experimental Investigation

The vibration properties of the submerged sandwich cylindrical shell with a viscoelastic core are investigated in this paper. Considering the acoustic-structure coupling, the analytical model of the submerged sandwich cylindrical shell that can handle three medium conditions including fluid-filled, fluid-loaded, and fluid-filled and -loaded is derived based on the wave propagation approach and the Flügge thin-shell theory. The vibration properties of the sandwich cylindrical shell under different medium and boundary conditions are analyzed, followed by a comparison of the damping effect of the constrained damping layer. Finally, an analysis is conducted on the influence of thicknesses of viscoelastic and constrained layers on vibration spectrum and natural frequency under fluid-filled and -loaded conditions. An experimental platform was established to conduct relevant experiments. Several important conclusions can be drawn.

Natural frequencies and stability for Z-shaped fluid-conveying pipes with constrained-layer damping – Semi-analytic modeling with experimental validation

As the common fluid-conveying component, pipe structures are susceptible to excessive vibration due to internal fluid and external excitation. Constrained-layer damping (CLD) is commonly applied to suppress structural vibrations. However, effective modeling and vibration suppression analysis for Z-shaped fluid-conveying pipes are lacking to explore novel dynamic behaviors. This paper presents a dynamic model for analyzing the three-dimensional vibration of Z-shaped fluid-conveying pipes treated by partial CLD based on the semi-analytical method. Utilizing Timoshenko beam theory and calculating the centrifugal, Coriolis, and inertial force of fluids, the energy of straight and curved fluid-conveying pipes treated by CLD is derived. Based on the Lagrangian energy function, the equation of motion is obtained by using the Rayleigh-Ritz method. The improved artificial spring set is deployed to model the interaction of pipe sections and the non-uniform constraint distribution of clamps. Modal parameters are obtained by solving characteristic equations. The proposed method is verified by comparisons with references and modal experiment results. Frequency parameters, damping effects, and stability are analyzed under various fluid, geometric, and CLD parameters. In conclusion, a novel dynamic model is provided for analyzing the vibration and stability of the Z-shaped fluid-conveying pipe treated by CLD, which lays a foundation for vibration suppression research of fluid-conveying pipe systems.

Vibration control of piezoelectric beams with active constrained layer damping treatment using LADRC algorithm

Active constrained layer damping (ACLD) treatment has become an important smart structure for vibration suppression due to its ability to achieve enhanced damping effects through real-time control. The control algorithm is a critical factor that determines the damping performance of the ACLD treatment. In this work, we utilize the linear active disturbance rejection control (LADRC) algorithm for the first time in the vibration suppression of beams with the ACLD treatment by compensating for the disturbance. To optimize vibration suppression, we also propose an efficient parameter tuning approach by analyzing the effects of controller bandwidth, control gain, and observer bandwidth on vibration suppression performance. Firstly, the dynamic model of elastic beams with the ACLD treatment is established and the LADRC algorithm is designed. Subsequently, the accuracy of the model is verified by comparing it with open literature and experiments. Then, the influences of the control parameters and different positions of the ACLD treatment on the vibration suppression performance are studied. Finally, the vibration suppression effects of LADRC and traditional PID algorithms are compared. The results indicate that the vibration suppression performance of the ACLD treatment is better than that of the passive constrained layer damping (PCLD) treatment. Setting the controller bandwidth to a small value and then adjusting other control parameters can effectively reduce the difficulty of parameter tuning while achieving superior vibration suppression performance. Appropriately increasing the observer bandwidth or reducing the control gain is beneficial for enhancing the suppression efficiency. The parameter tuning approach in this study provides vital guidance for the application of the LADRC algorithm in structural vibration suppression.

On the influence of low-velocity impact damage on constrained-layer damping in hybrid CFRP-elastomer-metal laminates

Following the principle of constrained-layer damping (CLD), fiber-metal-elastomer laminates (FMELs) offer a high potential for damped lightweight structures, overcoming the undesirable vibration characteristics of conventional lightweight materials. While proven to be versatile and efficient, the damage-tolerance of such laminates is unexplored. This study for the first time in literature addresses the damage-tolerance of this efficient damping mechanism using a combined experimental and numerical approach. Results of experimental low-velocity impact tests on different configurations of FMELs are presented. In subsequent numerical modal analyses, different types of damage, namely delaminations, intra-ply damage and permanent deformation, are modeled and their influence on the vibrational behavior is investigated. While all types of damage influence the natural frequencies and modal damping ratios with a strong mode dependency, all laminates retain a high amount of modal damping with losses typically not higher than 15%. The results obtained reveal, that CLD is an efficient intrinsic damping measure in FMELs even in the presence of different types of damage. The key contributions of this paper include the thorough experimental characterization of low-velocity impact damages in different configurations of FMELs as well as the numerical assessment of those in frequency-domain simulations.

Spectral collocation method for free vibration of sandwich plates containing a viscoelastic core

Viscoelastic constrained layer damping is a simple and efficient method for reducing noise, vibration, and fatigue in metal structures. In this work, a spectral collocation method utilizing a layer-wise plate theory was established to inspect the vibration characteristics of a sandwich plate with a viscoelastic core. The displacements of each layer satisfied the Mindlin plate theory. The core's transverse shear stress remained constant. The three layers’ transverse displacements were assumed to be identical. The displacement fields were reduced to nine variables by utilizing the interfaces’ continuity of the displacements. The equations of motion were obtained by utilizing Hamilton’s principle. The viscoelastic core’s material properties were considered as frequency-dependent. To address the complex eigenvalue problem, an iterative algorithm was used. The theoretical results were compared with published theoretical and experimental data for fully clamped rectangular sandwich plates to validate the proposed method. The modified Oberst beam method was applied by fitting the impulse response function to obtain the adhesive’s frequency-dependent storage modulus and loss factor. The natural frequencies and corresponding loss factors of three sandwich plates with different adhesives were measured by conducting impact tests. The numerical results from the present theoretical method agreed well with the measured results.

A nonlinear vibration model of fiber metal laminated thin plate treated with constrained layer damping patches

This paper explores the nonlinear vibration characteristics of fiber metal laminated thin plate(FMLTP) treated with constrained layer damping(CLD) patches. Additionally, based on the Jones-Nelson nonlinear material theory and the von Kármán geometric nonlinear theory, a theoretical model for FMLTP with CLD patches is established, considering material nonlinearity. Using the energy method, an energy equation is formulated and the nonlinear natural frequencies and vibration responses of the studied structure are iteratively determined through the Newton-Raphson method under various excitation amplitudes. Additionally, the modal damping ratios are calculated utilizing the complex modulus method. To validate the effectiveness of the model, a corresponding testing system is constructed, and tests are conducted on a 5-layer TA2/TC500 FMLTP treated with two pieces of CLD patches. The test results show excellent agreement with the theoretical results. Finally, the influences of different CLD patches treatment methods on the vibration characteristics of the FMLTP are discussed.

Efficacious constrained layer damping of carbon black‐reinforced nitrile butadiene rubber‐polyvinyl chloride blend vulcanizates: A comprehensive study

AbstractWe report efficacious vibration damping of carbon black reinforced nitrile butadiene rubber‐polyvinyl chloride blend (NVC) vulcanizates in a constrained layer damping (CLD) configuration. The objective is to compare numerical simulations using finite element method (FEM) and the widely used Ross‐Kerwin‐Ungar (RKU) model with the experimental results. NVC blend (50:50 by weight), was compounded with carbon black as reinforcing filler and vulcanized using a sulfur‐based curative system. Significant reinforcement and toughening were observed for the carbon black reinforced vulcanizates compared to the pristine blend. The viscoelastic properties of the vulcanizates were assessed using dynamic mechanical analysis (DMA), exploring their behavior concerning temperature variations and different frequencies to generate the Prony series coefficients for input in FEM analysis. Vibration damping experiments were conducted using the Oberst beam method in a single cantilever mode, with steel as the vibrating substrate, aluminum as the constraining layer, and the NVC vulcanizates as viscoelastic materials (VEM). Numerical simulations were performed using FEM to analyze mode shapes and frequency response function (FRF), and the RKU model was employed to quantify CLD system loss factors (SLF). The salient finding of this study was the observed SLF values in the range of 0.08–0.20 in the frequency regime of 200–2000 Hz. These values qualify the studied material as effective VEMs for CLD treatment of structural vibrations. This study supports design optimization efforts in a wide range of engineering applications where effective vibration damping is critical.Highlights Enhancement of NVC blend properties through carbon black reinforcement. Detailed analysis of viscoelastic behavior using DMA. Validation of findings through experimental modal analysis. Promising results in terms of system loss factors for CLD applications.