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.

Experimental control of sound radiation from a panel into an acoustic cavity using active compression constrained layer damping.

Abstract: The active compression constrained layer damping (ACCLD) is used for the control of sound radiation from a panel coupled with acoustic cavity. The acoustic cavity consists of five rigid walls while the sixth one is flexible aluminum plate. The plate is partially treated with ACCLD, which consists of viscoelastic material sandwiched between a permanent magnet and an electromagnet. Due to the attraction or repulsion forces generated between the two magnets, a compression or expansion of the viscoelastic layer will occur. The energy dissipation in the viscoelastic layer leads to vibration damping and automatically attenuation of sound pressure level inside the cavity. The ACCLD acts as actuator while a microphone used as semor. The ACCLD is used for controlling the first mode using a single patch at the center of the plate. With these arrangeMents, good vibration damping and good control of sound pressure level were achieved.

Reduction of vibration response and noise of oil pan using constrained layer damping

Abstract: NVH attribute has become an important issue, evolved both from legislative pressures in terms of external pass-by noise of vehicles as well as customer preferences for better noise and ride comfort in the vehicle. Major sources for vehicle pass-by noise consists of powertrain, tire and wind. The conventional method of controlling vehicle pass by noise is by enclosing the engine and gearbox assembly using some absorption materials with carrier and this leads to some practical issues like , durability and spatial constraints. In order to overcome these issues, structural noise can be controlled using damping treatment. In engine components oil pan has significant noise contribution at 2500 rpm. This is because of ratio of Sound Power Contribution to Area for oil pan is comparatively more than other engine components. The structure-borne noise of oil pan can be attenuated by using constraint layer dampening treatment. Vibration damping treatment is one of the most cost effective ways to reduce low frequency structure-borne noise with the help of Viscoelastic materials. CLD material reduces almost all high amplitude resonance frequencies of oil pan. Compared to the free-layer damping technique, CLD systems provide relatively higher performance as substrate thickness increases. Additionally, in weight-sensitive applications, CLD systems can provide lighter overall constructions than equivalent free-layer systems.

Power Flow In Beams Treated With Active Constrained Layer Damping

Abstract: This paper presents the power flow characteristics of beams treated with Active Constrained LayerDamping (ACLD). In the ACLD, a viscoelastic layer is sandwiched between two plies of activepiezoelectric material. The presence of the ACLD in a vibrating structure reduces the vibrationamplitude by dissipating the vibrational energy in shearing the viscoelastic layer. Numerical examplesshow the passive and active net power flow cantilever beams. The obtained results show the potentialof the power flow analysis in modeling ACLD element and the merits of ACLD in controlling thepower flow in structures

Optimal Configurations of ACLD/Plate for Bending Vibration Control using INSGA-II

Abstract: Active constrained layer damping (ACLD) has been demonstrated as an effective means of vibration and noise control for flexible structure. The overall performance of ACLD system is governed by the performance of the passive and the active controls on which the configurations of ACLD treatments have significant effect. In this paper, a multi-objective optimization model for ACLD treatments is established based on the finite element model of the plate partially covered with ACLD treatments. The improved non-dominated sorting genetic algorithm (INSGA-II) is developed to obtain the optimal configurations of ACLD treatments for vibration control of bending modes of the plate. In the optimization procedure, an integrated multi-objective optimization strategy is proposed, in which the passive and the active controls performance are considered simultaneously. The modal loss factors and the frequency response excited by the unit control voltage are selected as the passive and active control objectives, respectively. The location-numbering of the ACLD patches and the thickness of the viscoelastic materials (VEM) and piezoelectric material (PEM) are served as design variables. The vibration control results show that the better results of vibration control can be achieved in passive and active control when the optimal ACLD treatments are employed.

Constrained layer damping of a tennis racket

Abstract: When a tennis ball strikes a racket the impact causes vibrations which are distracting and undesirable to the player. In this work a passive damping system used to reduce vibration is described. The damping system uses a viscoelastic material along with a stiff composite constraining layer which is molded on the inner surface of the tennis racket frame. When a ball strikes a racket with this damping system the vibration causes shearing strain in the viscoelastic material. This strain energy is partially dissipated by the viscoelastic material, thereby increasing the racket damping. An analysis of the design was performed by creating a solid CAD model of the racket using Pro/Engineer. A finite element mesh was created and the mesh was then exported to ANSYS for the finite element modal analysis. The technique used to determine the damping ratio is the modal strain energy method. Experimental testing using accelerometers was conducted to determine the natural frequency and the damping ratio of rackets with and without the damping system. The natural frequency of the finite element model was benchmarked to the experimental data and damping ratios were compared. The modal strain energy method was found to be a very effective means of determining the damping ratio, and the frequencies and damping ratios correlated well with the experimental data. Using this analysis method, the effectiveness of the damping ratio to the change in key variables can be studied, minimizing the need for prototypes. This method can be used to determine an optimum design by maximizing the damping ratio with minimal weight addition.© (1996) COPYRIGHT SPIE--The International Society for Optical Engineering. Downloading of the abstract is permitted for personal use only.