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.

Frequency Control and Its Effect on the Dynamic Response of Flexible Structures

Abstract: The effect of structural optimization on optimal control design is studied in this paper. Structural optimiza- tion was treated as a problem of mass minimization with constraint on the open-loop frequency. The quadratic performance index, involving the state and control variables, was used in the design of the control system. A control system with only full-state feedback was considered. A procedure for generating the state and control weighting matrices by structural dynamics programs was outlined. By introducing simple scaling parameters, the weighting matrices were used effectively to achieve the desired control objectives. A number of case studies using a simple truss structure were made, in which vibration suppression with only initial disturbances was considered. The conclusion was that modification of the structural parameters (stiffness and structural mass) did not significantly alter the control design in this study. IBRATION control is an important consideration in the design of dynamic systems on the ground, in the air, and in space. The disturbances in ground and air vehicles are primarily caused by rough road (runway) profiles and airflow, such as gusts and powerplants. Similarly, in large space structures the disturbances are the result of slew- ing/pointing maneuvers, thermal transients, and mechanical machinery such as coolers, generators, etc. Control of the dynamic response is essential for maintaining the ride quality and performance requirements, as well as for the safety of the structure. The response of a structure is basically governed by three sets of parameters. The mass, damping, and stiffness repre- sent the structural parameters. The second set of parameters is due to the sources of external disturbances. These are generally external to the system and are considered as fixed inputs; thus their alteration is not within the realm of the structures/controls designer. The third set represents the control system, assuming that the structure is actively con- trolled. Control of the dynamic response by modification of the structural parameters alone is considered to be passive. Passive control is most appealing from both the reliability and maintainability points of view, if it can be achieved at all economically. Basically, the stiffness and mass modifica- tions result in frequency and mode changes, while the damp- ing affects the dissipation energy of the system. The damping can be significantly altered by either viscoelastic coatings (or constrained layer damping) or the provision of discrete dashpot mechanisms. The objective of vibration control is to design the structure and its controls either to eliminate vibration completely or to reduce the mean square response of the system to a desired level within a reasonable span of time. In addition, it is im- portant that this objective be achieved in some optimal way. For a structural designer, the optimal design represents an

Vibration Control through Passive Constrained Layer Damping and Active Control

Abstract: To add damping to systems, viscoelastic materials (VEM) are added to structures. In order to enhance the damping effects of the VEM, a constraining layer is attached, creating a passive constrained layer damping (PCLD) treatment. When this constraining layer is an active element, the treatment is called active constrained layer damping (ACLD). Recently, the investigation of ACLD treatments has shown it to be an effective method of vibration suppression. In this paper, the treatment of a beam with a separate active and PCLD element will be investigated. Two new hybrid variations will be introduced. A Ritz-Galerkin approach is used to obtain discretized equations of motion. The damping is modeled using the Golla-Hughes-McTavish (GHM) method and the system is analyzed in the time domain. By optimizing on the performance and control effort for both the active and passive case, it will be shown that hybrid treatment is capable of lower control effort with more inherent damping, and is therefore a better approa...

On the Use of Vertically Reinforced 1-3 Piezoelectric Composites for Hybrid Damping of Laminated Composite Plates

Abstract: This paper deals with the analysis of vertically reinforced 1-3 piezoelectric composite materials as the material for the distributed actuator of smart laminated composite plates. A simple micromechanics model has been derived to predict the effective elastic and piezoelectric coefficients of these piezoelectric composites which are useful for the three dimensional analysis of smart structures. The main concern of this study is to investigate the performance of a layer of this vertically reinforced 1-3 piezoelectric composite material as the constraining layer of the active constrained layer damping (ACLD) treatment. A finite element model has been developed for analyzing the active constrained layer damping of laminated symmetric and antisymmetric cross-ply and angle-ply composite plates integrated with the patches of such ACLD treatment. Both in-plane and out-of-plane actuation of the constraining layer of the ACLD treatment have been utilized for deriving the finite element model. The analysis revealed...

Reduction of squeal noise from disc brake systems using constrained layer damping

Abstract: Squeal noise generation during braking is a complicated dynamic problem which automobile manufacturers have confronted for decades. Customer complaints result in significant yearly warranty costs. More importantly, customer dissatisfaction may result in rejection of certain brands of brake systems. In order to produce quality automobiles that can compete in today's marketplace, the occurrence of disc brake squeal noise must be reduced. The addition of a constrained layer material to brake pads is commonly utilized as a means of introducing additional damping to the brake system. Additional damping is one way to reduce vibration at resonance, and hence, squeal noise. The simulation of braking events in dynamometers has typically been the preferred insulator selection process. However, this method is costly, time consuming and often does not provide an insight into the mechanism of squeal noise generation. This work demonstrates the use of modal analysis techniques to select brake dampers for reducing braking squeal. The proposed methodology reduces significantly the insulator selection time and allows an optimized use of the brake dynamometer to validate selected insulators.