Constrained-layer damping

About: Constrained-layer damping is a research topic. Over the lifetime, 795 publications have been published within this topic receiving 15758 citations.

Computation Model for Structure-Borne Noise from Railway Bridge with CLD

Abstract: With the increase of running speed and axel load of trains, the structure-borne noise emanating from the railway bridges is more and more serious. The constrained layer damping can achieve an obvious reduction of vibration and noise of the treated structure in a wide frequency range by means of dissipating the vibration energy owing to damping layer’s shear deformation. Based on the train-track-bridge coupled vibration, modal strain energy method and statistical energy analysis, a theoretical model for calculating the vehicle-induced vibration and noise of the railway bridge with constrained layer damping is presented. The vibration and noise of the (32 + 40 + 32) m steel-concrete composite bridge before and after constrained layer damping installation is simulated. The structure-borne noise radiated by the bridge in the whole analysis frequency range is reduced significantly. The sound pressure level at the field point which is 30 m to the track centerline in horizontal direction and 1.5 m to the ground in vertical direction is reduced by 4.3 dB(A).

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

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

A novel method for analyzing vibration and damping effect of a sandwich conical shell with passive constrained layer damping

Abstract: Based on the Donnell theory of thin shells,considering the level offset of the cone vertex in all layers, the governing equations of host shell and constraining shell can be obtained . For the viscoelastic layer, only shear deformations are considered. Employing the linear viscoelastic theory, combined with the governing equations of host shell and constraining shell, as well as the normal balance equation of viscoelastic layer, the integrated first order constant differential matrix equation of a sandwich conical shell with circular passive constrained layer damping is derived. The coefficient matrix of the equation is not constant, and the expression for each element is more complex than PCLD cylindrical shell. After that, a semi-analytical, semi-numerical method is developed to analyze the vibration and damping characteristics of a sandwich conical shell by means of the transfer matrix method which is based on precise integration technology. Comparisons with literature results show that the proposed approach is effective. The effects of parameters on natural frequency and dissipative factors are also discussed.

Effectiveness of piezoelectric fiber reinforced composite laminate in active damping for smart structures

Abstract: This paper deals with the effect of ply orientation and control gain on tip transverse displacement of functionally graded beam layer for both active constrained layer damping (ACLD) and passive constrained layer damping (PCLD) system. The functionally graded beam is taken as host beam with a bonded viscoelastic layer in ACLD beam system. Piezoelectric fiber reinforced composite (PFRC) laminate is a constraining layer which acts as actuator through the velocity feedback control system. A finite element model has been developed to study actuation of the smart beam system. Fractional order derivative constitutive model is used for the viscoelastic constitutive equation. The control voltage required for ACLD treatment for various symmetric ply stacking sequences is highest in case of longitudinal orientation of fibers of PFRC laminate over other ply stacking sequences. Performance of symmetric and anti-symmetric ply laminates on damping characteristics has been investigated for smart beam system using time and frequency response plots. Symmetric and anti-symmetric ply laminates significantly reduce the amplitude of the vibration over the longitudinal orientation of fibers of PFRC laminate. The analysis reveals that the PFRC laminate can be used effectively for developing very light weight smart structures.

Sound transmission loss improvement by a viscoelastic material used in a constrained layer damping system

Abstract: A constrained layer damper is a viscoelastic material that is embedded between two parallel plates. The vibration energy in the first leaf creates shear strain in the viscoelastic material which dissipates kinetic energy into heat. A CLD is an effective way to maximize transmission loss through a partition by increasing its damping. SEA is a method for estimating the acoustic power flow through a system. The method subdivides the system into smaller elements, the so-called subsystems, that support a group of resonant modes and have a sufficient modal density and modal overlap. The measurement of the loss factors on the wall specimens with and without the viscoelastic material was done as part of a parallel paper by J.G. Richter. The reverberation method was used to measure the total loss factors on one side of the installed wall. The addition of a viscoelastic material between the leaves improves the TL significantly by more than 10 dB in the mid- and high frequency range increasing the STC rating by 8 points from 44 to 52.