Constrained-layer damping

About: Constrained-layer damping is a(n) research topic. Over the lifetime, 795 publication(s) have been published within this topic receiving 15758 citation(s).

Distributed Piezoelectric-Polymer Active Vibration Control of a Cantilever Beam

Abstract: An active vibration damper for a cantilever beam was designed using a distributed-parameter actuator and distributed-parameter control theory. The distributed-parameter actuator was a piezoelectric polymer, poly (vinylidene fluoride). Lyapunov's second method for distributed-parameter systems was used to design a control algorithm for the damper. If the angular velocity of the tip of the beam is known, all modes of the beam can be controlled simultaneously. Preliminary testing of the damper was performed on the first mode of the cantilever beam. A linear constant-gain controller and a nonlinear constant-amplitude controller were compared. The baseline loss factor of the first mode was 0.003 for large-amplitude vibrations (± 2 cm tip displacement) decreasing to 0.001 for small vibrations (±0.5 mm tip displacement). The constant-gain controller provided more than a factor of two increase in the modal damping with a feedback voltage limit of 200 V rms. With the same voltage limit, the constant-amplitude controller achieved the same damping as the constant-gain controller for large vibrations, but increased the modal loss factor by more than an order of magnitude to at least 0.040 for small vibration levels.

The forced vibration of a three-layer, damped sandwich beam with arbitrary boundary conditions

Abstract: The sixth-order differential equation of motion is derived in terms of the transverse displacement, w, for a three-layer sandwich beam with a viscoelastic core. Mathematical expressions in terms of w are found for a variety of beam boundary conditions. The solution of the differential equation by the method of Di Taranto is shown to yield a special class of complex, forced modes of vibration which are completely uncoupled. These complex modes can only exist when the beam is externally excited by specific “damped normal loadings” which are also complex and which are proportional to the local transverse inertia loading on the beam. Use of these modes in the analysis of the forced vibration problem leads to a simple series form of solution. The orthogonality of these complex modes is briefly discussed and proved.

Damping of Flexural Waves by a Constrained Viscoelastic Layer

Abstract: For a number of years it has been known that flexural vibrations in a plate can be damped by the application of a layer of damping (viscoelastic) material that is in turn constrained by a backing layer or foil. A common example is the damping tape currently used in aircraft.This paper presents a quantitative analysis of the damping effectiveness of such a constrained layer. As in the work of H. Oberst the damping is characterized by the loss factor η, which is the normalized imaginary part of the complex bending stiffness of the damped plate.The calculated damping factor depends on the wavelength of bending waves in the damped plate, and on the thicknesses and elastic moduli of the plate, the damping layer, and the constraining layer. A complex shear modulus is assigned to the damping layer, where all of the energy dissipation is assumed to take place.Damping factors have been determined experimentally on laboratory test bars for a number of constrained‐damping‐layer applications for frequencies from abou...

Finite Element Prediction of Damping in Structures with Constrained Viscoelastic Layers

Abstract: An efficient method is described for finite element modelling of three-layer laminates containing a viscoelastic layer. Modal damping ratios are estimated from undamped normal mode results by means of the modal strain energy method. Comparisons are given between results obtained by the MSE method implemented in NASTRAN, by various exact solutions for approximate governing differential equations, and by experiment. Results are in terms of frequencies, modal damping ratios, and mechanical admittances for simple beams, plates, and rings. Application of the finite element -- MSE method in design of integrally damped structures is discussed.