Study for the prediction of damping and sound radiation characteristics due to structural shape changes

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Ji Woo Yoo Jin-Kwan Suh Sang Woo Lee Jong Won Park Jun Hong Park

ABSTRACT

Applying damping sheets or dampers (dynamic or mass) can reduce noise from vibrating structure as well as vibration. However, this approach requires increases of weight and cost. If one can reduce structural noise by only modifying the structural shape, which would be the best practice. It is natural that the noise characteristics change when the structure is modified, but the recent experiment on the sunroof frame showed that the modification of the frame beads results in change of the structural damping, so that the corresponding noise can be reduced. In this context, the reason why the structural damping and the related noise upon an impact excitation is changed is theoretically investigated. The change of dynamic and damping characteristics of the strip panels when their shapes are modified is experimentally found and it is shown that such behaviours can be predicted by computer simulation. Some experimental specimen, mainly strip-type panels, are examined for the numerical verification, and especially damping ratios are investigated. Key Word : damping( ), noise( ), vibration( ), sound radiation( ), FEM, BEM, sunroof( ), structure( ), bead ( )

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; , E-mail : j.w.yoo@hyundai.com

Tel : 031-368-0394, Fax : 031-368-2733 **

한국소음진동공학회 2014년 추계학술대회

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Fig.1 KH Sunroof frame (Frame B as a noise source)

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Fig.3 Vibration decay times obtained by experiment and

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Fig.4 Shapes of simplified specimens for the identification of

damping and noise characteristics

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Fig.5 Experimental set-up of a simplified specimen to identify

noise and vibration characteristics

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right, elastic bolting by inserting elastic foam

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Fig. 8 Simulation process for the prediction of damping

characteristics (improved simulation technique)

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radiation from a structure in vibration Fig. 10 .

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Fig.10 Noise level obtained by experiment (upper) and improved

simulation (lower)

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Fig. 11 Vibration decay times by experiment (left) and improved

simulation (right)

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(1) , 2011, KH Sunroof P1

, . (2) Park, J., Mongeau, L., Siegmund, T., 2003, Influence of

support properties on the sound radiated from the vibrations of rectangular plates, Journal of Sound and Vibration, 264, pp.775-794..

(3) Cremer, L., Heckl, M., Ungar, E. E., 1988, Structure-Borne Sound 2nd ed., pp. 215-242.

(4) Danilov, O., Sgard, F., Olny, X., 2002, Oberst beam as a tool for complex Young's modulus measurement of porous materials, Forum Acousticum, Sevilla.

(5) VA One 2014 Tutorials Guide, ESI group.

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