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.

Spectral finite element modeling of beams treated with active constrained layer damping with consideration of thickness deformation

Abstract: As we all know, the damping layer in the structures treated with active constrained layer damping (ACLD) is much softer than the other layers. So thickness deformation in the damping layer may occur under flexural loads, which may consequently change the dynamic characteristic and affect active control efforts. Thus, a new model for ACLD structures is built with consideration of the thickness deformation as well as the shear deformation in the damping layer. Both the differential equations and the boundary conditions are derived for the ACLD beams. The novel spectral finite element method (SFEM) is used to model the ACLD structure in the frequency domain. And a special method called "frequency-time conversion" is firstly proposed, which uses the eigenvalues and the eigenvectors to reconstruct the control equation in the time domain. Then the linear quadratic regulator with a prescribed degree of stability based on output feedback is used, which optimizes control energy and guarantees big damping simultaneously. And some comparisons are made between the new model and the conventional Mead-Markus model.

An Experimental Study on the Use of Active Constrained Layer Damping for Thin Curved Smart Shell Structures

Abstract: Thin Open Curved Shell Structures constitute the major building block of many critical structures such as Aircraft Cabins, Ship Hulls and bodies of rockets and missiles. In the present work, an open thin curved shell made of Aluminium material has been chosen to investigate the potential of ACLD effectiveness with MFC Actuator. The shell ACLD system has been modelled using system identification method and converted into state space form for designing the control law of the LQR controller. Finite Element Analysis of the bare structure has been performed in ANSYS. Using modal solution results, the best possible location for the placement of patches has been found out for combined vibration control of first three modes using Modal Strain Energy (MSE) approach. The FEA Modal Solution results have been correlated with the experimental modal analysis results obtained with the help of ICATS (Imperial College’s Modal Analysis and Testing Software). Significant vibration attenuation resulted for partially covered PCLD and ACLD treatments on open curved shell. Thus, ACLD provides a practical means for controlling the vibration of complex structures such as an open curved shell with currently available piezoelectric (MFC) actuators without the need for excessively large actuation voltages.

Identification of viscoelastic material properties based on Big Bang-Big Crunch optimization method

Abstract: An efficient identification method of the dynamic properties of viscoelastic damping materials using an optimization technique is proposed. A Zener fractional derivative model is used to describe the frequency-dependent dynamic characteristics of materials. In this study, the viscoelastic material is used in a Passive Constrained Layer Damping (PCLD) configuration in order to increase the shear deformation in the material. Mean Square Velocities (MSVs) of a clamped-free beam covered with a PCLD patch are measured in an environmental chamber at different frequencies and used as reference MSVs. The excitation force is performed thinks to a low mass magnet fixed on the beam and placed inside a coil subjected to an electrical current. Numerical MSVs are calculated using an equivalent single layer plate model with warping functions chosen to ensure continuity of transverse shear stresses and displacements layer's interfaces.

Constrained layer damping system

Abstract: A constrained layer damping system that reduces noise and electro-magnetic interference emitted from an engine. The constrained layer damping system comprises a wiring harness (22) coated with an encapsulant; a first layer (14) of formed material on a first side of the wiring harness (22); and a second layer (28) of formed material attached to a second side of the wiring harness (22) such that the wiring harness is between the first and the second layers (14,28). A wiring harness (22) may extend from a control module (12), with the first layer (14) of formed material being on a first side of the control module (12) and the second layer (28) of formed material being on a second side of the control module (12). The constrained layer damping system permits a powertrain control module to be mounted on an air intake manifold plenum cover (14) without being negatively affected by noise, vibration, or electro-magnetic interference from the engine.

Enhancement of the Dynamic Buckling Load and Analysis of Active Constrained Layer Damping with Extension and Shear Mode Piezoceramic Actuators

Abstract: (ABSTRACT) We consider geometric and material nonlinearities when studying numerically, by the finite element method, transient three-dimensional electroelastic deformations of a graphite-epoxy square plate sandwiched between two piezoceramic (PZT) layers. Points on the four edges of the bottom surface of the plate are restrained from moving vertically. The two opposite edges of the plate are loaded by equal in-plane compressive loads that increase linearly with time and the other two edges are kept traction free. The plate material is modeled as orthotropic and neoHookean. For the transversely isotropic PZT the second Piola-Kirchhoff stress tensor and the electric displacement are expressed as second degree polynomials in the Green-St. Venant strain tensor and the electric field. Both direct and converse piezoelectric effects are accounted for in the PZT. The plate is taken to have buckled when its centroidal deflection equals three times the plate thickness. The dynamic buckling load for the plate is found to strongly depend upon the rate of rise of the applied tractions. With the maximum electric field limited to 1kV/mm, the buckling load is enhanced by 18.3± when the PZT elements are activated. For a peak electric field of 30kV/mm, the buckling load increased by 58.5±. When more than 60± of the surface area of the top and the bottom surfaces of the plate are covered by the PZT layers, then square PZT elements placed symmetrically about the plate centroid provide a larger enhancement in the buckling load than rectangular shaped or cross-shaped PZT elements. An increase in the plate thickness relative to that of the PZT actuators decreases the effectiveness of the PZT in enhancing the buckling load for the plate. The finite element code was modified to also analyze, in time domain, transient deformations of a viscoelastic material for which the second Piola-Kirchhoff stress tensor is expressed as a linear functional of the strain history of the Green-St. Venant strain tensor. It was used to analyze three-dimensional deformations of a thick laminated plate with layers made of aluminum, a viscoelastic material and a PZT. The following two arrangements of layers are considered. In one case a central PZT layer is surrounded on both sides by viscoelastic layers and aluminum layers are on the outside surfaces. The PZT is poled in the longitudinal direction and an electric field is applied in the thickness direction. Thus shearing deformations of the PZT layer are dominant. In the second arrangement, …