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.

Smart constrained layer damping of functionally graded shells using vertically/obliquely reinforced 1?3 piezocomposite under a thermal environment

Abstract: We analyze active constrained layer damping (ACLD) of functionally graded (FG) shells under a thermal environment using vertically and obliquely reinforced 1?3 piezocomposites (PZCs) and investigate the performance of PZCs as materials for the constraining layer of the ACLD treatment. The shell's deformations are analyzed by using a modified first-order shear deformation theory and the finite element method. A temperature gradient is applied across the thickness of the shell. Both in-plane and out-of-plane actuations of the constraining layer of the ACLD treatment have been utilized. Particular emphasis has been placed on ascertaining the performance of patches when the orientation angle of the piezoelectric fibers in the constraining layer is varied in two mutually orthogonal vertical planes. It is found that the vertical actuation dominates over the in-plane actuation, and distributed actuators made of vertically and obliquely reinforced 1?3 PZCs have great potential for controlling the performance of FG?shells under a thermal environment.

Damping Characteristics of Cylindrical Laminates with Viscoelastic Layer Considering Temperature- and Frequency-Dependence

Abstract: The vibration and damping characteristics of the cylindrical hybrid panels with viscoelastic layers were investigated by using a full layerwise shell finite element method which can consider temperature and frequency dependent material properties. The present layerwise shell theory can accurately represent the zig-zag in-plane and out-of-plane displacements of multilayered hybrid structures and can fully consider the transverse shear and normal strains and the perfect cylindrical geometry. The remarkable differences of the frequency response functions of cylindrical hybrid panels including constrained layer damping and co-cured sandwiched models were observed. Present results show that the damping mechanics of hybrid panels with viscoelastic layers may be greatly affected by their temperature and frequency dependent material properties and that the present full layerwise theory can be used to accurately predict the vibration and damping characteristics of hybrid shells with viscoelastic layers.

Design of a railway wheel with acoustically improved cross-section and constrained layer damping

Abstract: The rolling-noise generating characteristics of a railway wheel design have been studied theoretically. Two aspects of design for reducing noise have been investigated, optimisation of the cross-sectional shape of the wheel and addition of a constrained layer damping treatment. In this the thermo-mechanical behaviour of tread-braked wheels must be taken into account. To produce significant noise reduction, the damping achieved by the constrained layer treatment must exceed the effective ’rolling damping’. A finite element model is used to produce the modal basis of the wheel and to predict the modal damping of a wheel with visco-elastic layers a method of complex eigenvalue analysis has been used. The analysis indicates that the wheel component of rolling noise from the UIC standard tread-braked freight wheel can be reduced by more than 5 dB(A) by a combination of the two measures.

Suppression of ring vibration modes of high nodal diameter using constrained layer damping methods

Abstract: Constrained layer damping treatments utilize the energy dissipative properties of viscoelastic materials to increase the passive damping in structures. This paper investigates the performance of constrained layer damping treatments applied to a ring. An analytical model is developed to predict the behaviour of such a ring over a large number of modes. Relative motion between the ring and constraining layer in both the circumferential and radial directions are considered. Predictions of steady state dynamic behaviour obtained using the model are validated by comparison with results from experiments and finite element analysis. The model is then used to evaluate the effect of various parameters on the damping achieved. It is shown that for any particular configuration a plot of damping against mode number has two maxima. These peaks occur when optimum values for the deformation of the viscoelastic layer are achieved firstly for shear and secondly for radial extension and compression.

Improved Helicopter Aeromechanical Stability Analysis Using Segmented Constrained Layer Damping and Hybrid Optimization

Abstract: Aeromechanical stability plays a critical role in helicopter design and lead-lag damping is crucial to this design. In this paper, the use of segmented constrained damping layer (SCL) treatment and composite tailoring is investigated for improved rotor aeromechanical stability using formal optimization technique. The principal load-carrying member in the rotor blade is represented by a composite box beam, of arbitrary thickness, with surface bonded SCLs. A comprehensive theory is used to model the smart box beam. A ground resonance analysis model and an air resonance analysis model are implemented in the rotor blade built around the composite box beam with SCLs. The Pitt-Peters dynamic inflow model is used in air resonance analysis under hover condition. A hybrid optimization technique is used to investigate the optimum design of the composite box beam with surface bonded SCLs for improved damping characteristics. Parameters such as stacking sequence of the composite laminates and placement of SCLs are us...