Showing papers on "Constrained-layer damping published in 2020"

Nonlinear vibration analysis of fiber reinforced composite cylindrical shells with partial constrained layer damping treatment

Abstract: This research proposes a novel analytical model capable of accurately predicting the strain-dependent characteristics of fiber reinforced composite shells (FRCSs) with partial constrained layer damping (CLD) treatment by considering the nonlinearities of fiber reinforced composite and viscoelastic materials simultaneously. The nonlinear material properties are represented based on Jones-Nelson nonlinear theory, energy-based strain energy method, and complex modulus method. Then, the governing equations of motion for FRCSs are developed via Ritz method, and the identification procedure of nonlinear fitting parameters is also presented. By taking a T300 carbon fiber/epoxy resin cylindrical shell with partial CLD patches as an example, a series of experiments are carried out to validate the proposed modeling approach. Finally, the effects of material properties on nonlinear vibration behaviors of FRCSs covered with partial CLD patches are evaluated. Comparisons show that the proposed nonlinear model is more accuracy than that without considering strain dependence, where the maximum errors between the proposed model and measured data for natural frequencies, damping ratios and resonant response are 6.9%, 11.3%, and 11.2%, respectively.

Applying constrained layer damping to reduce vibration and noise from a steel-concrete composite bridge: An experimental and numerical investigation:

Abstract: Structure-borne noise from railway bridges has become increasingly severe due to increased train speeds and axle loads. Constrained layer damping can suppress structural vibration and noise conside...

General Homogenised Formulation for Thick Viscoelastic Layered Structures for Finite Element Applications

Abstract: Viscoelastic layered surface treatments are widely used for passive control of vibration and noise, especially in passenger vehicles and buildings. When the viscoelastic layer is thick, the structural models must account for shear effects. In this work, a homogenised formulation for thick N-layered viscoelastic structures for finite element applications is presented, which allows for avoiding computationally expensive models based on solids. This is achieved by substituting the flexural stiffness in the governing thin beam or plate equation by a frequency dependent equivalent flexural stiffness that takes shear and the properties of the different layers into account. The formulation is applied to Free Layer Damping (FLD) and Constrained Layer Damping (CLD) beams and plates and its ability to accurately compute the eigenpairs and dynamic response is tested by implementing it in a finite element model and comparing the obtained results to those given by the standard for the application—Oberst for the FLD case and RKU for the CLD one—and to a solid model, which is used as reference. For the cases studied, the homogenised formulation is nearly as precise as the model based on solids, but requires less computational effort, and provides better results than the standard model.

Effects of material parameters on the transient dynamics of an impacted plate with partial constrained layer damping treatment

Abstract: Due to their dynamic properties, viscoelastic materials are largely used in different sectors of industry to reduce noise and vibration in mechanical structures. In particular, partial constrained layer damping (PCLD) treatments have been used and studied in order to lessen stationary vibration and ringing noise. In the present work, simulations are performed to predict the effect of PCLD on the initial transient dynamic response of a planar impacted structure. The structure is a simply supported, rectangular aluminum plate impacted at its center with a small steel sphere. A parametric study is carried out based on a finite element model using ABAQUS 6.5 [Dassault Systemes (ABAQUS Inc., Silicon Valley, CA)], whose results are well correlated with previous experiments. The model reflects the effects of several PCLD parameters on the initial transient response of the padded plate. The results from the parametric study show that the stiffness of the viscoelastic layer is a crucial parameter in the initial transient dynamic response of the impacted plate. It is also shown that the pads locally modify the dynamic properties of the plate thus causing changes in the time evolution of the deformation field. The combined use of PCLD to reduce both the initial transient response of the impacted structure and the ensuing flexural vibration could open the way for a better reduction of impact noise.

Microstructural Topology Optimization of Constrained Layer Damping on Plates for Maximum Modal Loss Factor of Macrostructures

Abstract: This paper presents microstructural topology optimization of viscoelastic materials for the plates with constrained layer damping (CLD) treatments. The design objective is to maximize modal loss factor of macrostructures, which is obtained by using the Modal Strain Energy (MSE) method. The microstructure of the viscoelastic damping layer is composed of 3D periodic unit cells. The effective elastic properties of the unit cell are obtained through the strain energy-based method. The density-based topology optimization is adopted to find optimal microstructures of viscoelastic materials. The design sensitivities of modal loss factor with respect to the design variables are analyzed and the design variables are updated by Method of Moving Asymptotes (MMA). Numerical examples are given to demonstrate the validity of the proposed optimization method. The effectiveness of the optimal design method is illustrated by comparing a solid and an optimized cellular viscoelastic material as applied to the plates with CLD treatments.

The analysis of vibration characteristics of fiber metal laminated thin plate with partial constrained layer damping patches treatment

Abstract: This study focuses on vibration characteristics analysis of fiber metal laminated thin plate (FMLTP) with partial constraint layer damping (CLD) patches treatment. Firstly, the overall stress–strain relationships of the viscoelastic layer, the constraint layer and the covered FMLTP are deduced to establish the theoretical model. Then, the classical laminates theory, orthogonal polynomial method, complex modulus method and energy method are employed to solve the natural frequencies, modal shapes, vibration responses and modal damping ratios. As an example to demonstrate the feasibility of the developed model, the experimental test of TA2/TC500 laminated thin plate treated with different sizes and shapes of stainless steel/Zn-33 CLD patches is implemented. The calculated and measured results show a good consistency. Moreover, the influences of different CLD treating positions and shapes on the vibration characteristics of FMLTP are investigated here.

Active damping of geometrically nonlinear vibrations of smart composite shells using elliptical smart constrained layer damping treatment with fractional derivative viscoelastic layer

Abstract: In this article, the performance of elliptical smart constrained layer damping treatments on active damping of geometrically nonlinear vibrations of doubly curved smart laminated composite shells i...

Sound Transmission Loss of a Sandwich Plate with Adjustable Core Layer Thickness.

Abstract: Compressible Constrained Layer Damping (CCLD) is a novel, semi-active, lightweight-compatible solution for vibration mitigation based on the well-known constrained layer damping principle. The sandwich-like CCLD set-up consists of a base structure, a constraining plate, and a compressible open-cell foam core in between, enabling the adjustment of the structure's vibration behaviour by changing the core compression using different actuation pressures. The aim of the contribution is to show to what degree, and in which frequency range the acoustic behaviour can be tuned using CCLD. Therefore, the sound transmission loss (TL), as an important vibro-acoustic index, is determined in an acoustic window test stand at different actuation pressures covering a frequency range from 0.5 to 5 kHz. The different actuation pressures applied cause a variation of the core layer thickness (from 0.9 d0 to 0.3 d0), but the resulting changes of the stiffness and damping of the overall structure have no significant influence on the TL up to approximately 1 kHz for the analysed CCLD design. Between 1 kHz and 5 kHz, however, the TL can be influenced considerably well by the actuation pressure applied, due to a damping-dominated behaviour around the critical frequency.

Acoustic Radiation and Dynamic Study of a Steel Beam Damped with Viscoelastic Material

Abstract: Steel structures subject to dynamic loads are prior to generate excessive vibration and noise. Viscoelastic treatment is an effective measure to mitigate the vibration and noise from thin-walled structures in a broad frequency range. H-shaped steel beams are widely used in civil engineering. So an experiment system is established and a series of impact hammer tests are conducted to assess the modal parameters, dynamic response and acoustic behaviour of an H-shaped steel beam coated with various viscoelastic treatments. Firstly, the spectra of the velocity response and acoustic radiation of the bare beam are analysed based on the tested data. Secondly, the resonance frequencies and modal loss factors of the beam with various viscoelastic treatments derived from the frequency response function are compared. Finally, the effect of the layout and thickness of viscoelastic patches on the mitigation of vibration and noise is discussed experimentally. It is shown that the modal loss factor of the first mode increases from 0.012 to 0.191 when the web is treated with 5 mm thick constrained layer damping (CLD). The viscoelastic patches on the web of the H-shaped beam are more effective to control the vibration and noise of the beam than the patches on the flanges. The viscoelastic treatment has distinct effect on the reduction of structural vibration and noise owing to the different dominant frequencies of vibration and noise as well as the frequency-dependent radiation efficiency. The normal velocity level of the H-shaped beam with an 8 mm thick web can be reduced by more than 10 dB and the sound pressure level around the beam about 8 dB when the web is partially covered with the constrained layer damping composed of 2.0 mm thick damping layer and 3.0 mm thick constraining layer.

Modal damping behavior of plane and 3D curved constrained layer damping CFRP-elastomer-metal laminates

Abstract: The persistent trend of investigations in lightweight design materials also leads to a high interest in suitable applications of damping concepts to those materials. Usually, lightweight materials show low damping. The resulting structures are often prone to vibrations and additional damping material has to be added to meet modern comfort and fatigue requirements. Hybrid carbon fiber reinforced plastics-elastomer-metal laminates offer adaptable damping properties by adjusting the properties of the individual constituents or their hybrid layup. The proposed hybrid laminates dissipate flexural vibrations according to the constrained layer damping mechanism. The influence of the elastomer modulus and thickness and the fiber orientation of the carbon fiber reinforced plastics constraining layers on the vibration and damping behavior is investigated. Therefore, modal analysis on cantilever beams, panel sized specimens and three dimensionally curved structures are conducted. Temperature dependent modal analysis on coupon level are performed to investigate the influence of the glass transition of the elastomer layers on the vibration damping behavior. An analytical model, which takes into account the viscoelastic behavior of the elastomer and the CFRP is used to model the damping behavior. The influence of the additional damping of the CFRP layers in off axis directions, is characterized at various temperatures. The results obtained with different specimen geometries are compared among each other and good accordance to the analytical model is observed.