This content is not included in your SAE MOBILUS subscription, or you are not logged in.
Structural Damping by the Use of Fibrous Materials
ISSN: 0148-7191, e-ISSN: 2688-3627
Published June 15, 2015 by SAE International in United States
Annotation ability available
Because of the increasing concern with vehicle weight, there is an interest in lightweight materials that can serve several functions at once. Here we consider the vibration damping performance provided by an “acoustical” material (i.e., a fibrous layer that would normally be used for airborne noise control). It has been previously established that the vibration of panel structures creates a non-propagating nearfield in the region close to the panel. In that region, there is an oscillatory, incompressible fluid flow parallel to the panel whose strength decays exponentially with distance from the panel. When a fibrous medium is placed close to the panel in the region where the oscillatory nearfield is significant, energy is dissipated by the viscous interaction of the flow and the fibers, and hence the panel vibration is damped. The degree of panel damping is then proportional to the energy removed from the nearfield by the viscous interaction with the fibrous medium. In his paper, experiments are described that demonstrate this effect. Fibrous layers were placed next to a lightly damped panel driven by a shaker, and the vibration of the panel was quantified by using a scanning laser vibrometer. These experiments showed that it is possible to achieve a strong damping effect by using fibrous layers. In addition a new theory that can be used to predict the depth of treatment needed to achieve a damping effect is presented. The theory is based on analyzing the wave number transforms of the panel motion in terms of radiating and non-radiating components, and by using that approach to identify the spatial extent of the oscillatory nearfield, and hence the depth of the fibrous layer required to provide effective structural damping.
CitationKim, N., Lee, S., Bolton, J., Hollands, S. et al., "Structural Damping by the Use of Fibrous Materials," SAE Technical Paper 2015-01-2239, 2015, https://doi.org/10.4271/2015-01-2239.
- Lai Heng-Yi, Bolton J. Stuart and Alexander Jonathan H., “Structural damping by the use of fibrous blankets,” Proceedings of Noise-Con 98, 403-408, Ypsilanti, Michigan, April 1998.
- Gerdes Ronald W., Alexander Jonathan H., Gardner Bryce K., Lai Heng-Yi and Bolton J. Stuart, “The use of poro-elastic finite elements to model the structural damping effect of fibrous acoustical treatments,” Proceedings of Noise-Con 98, 409-414, Ypsilanti, Michigan, April 1998.
- Lai, H., Katragadda, S., Bolton, J., and Alexander, J., “Layered Fibrous Treatments for a Sound Absorption and Sound Transmission,” SAE Technical Paper 972064, 1997, doi:10.4271/972064.
- Panneton Raymond, “Comments on the limp frame equivalent fluid model for porous media,” The Journal of Acosutical Society of America, 122(6), 2007.
- Johnson D.L., Koplik J., and Dashen R., “Theory of dynamic permeability and tortuosity in fluid-saturated porous media,” Journal of Fluid Mechanics, 176, 379-402, 1987.
- Champoux Y. and Allard J.-F., “Dynamic tortuosity and bulk modulus in air-saturated porous media.” Journal of Applied Physics, 70, 1975-1979, 1991.
- Atalla N. and Sgard F., “Modeling of perforated plates and screens using rigid frame porous models,” The Journal of Sound and Vibration, 303, 195-208, 2007.