Influence of Internal Damping on Vibration and Acoustic Radiation Characteristics of Rectangular Plate

概要

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In this paper, the effect of internal damping on the vibration and acoustic radiation characteristics of rectangular plates is investigated. Plates are assumed to be constructed of aluminum and to be clamped along the four sides. The characteristics are studied by FEM analysis and an experiment. First of all, the internal-damping characteristics of the aluminum are investigated in an excitation experiment using a beam-shaped test specimen and are evaluated on the basis of the loss coefficient, and it is clarified that the loss coefficient increases slightly with excitation frequency. In particular, a polyolefin film, used for varying the internal-damping characteristics, causes the characteristics to depend more strongly on excitation frequency than those of the test specimen not having the film. In the case of the plate, the natural frequency is hardly affected by internal damping, whereas internal damping induces changes in the vibration mode and the amplitude of flexural displacement. In particular, the vibration mode influences not only the appearance but also the modal shape of the plate. Consequently, the acoustic radiation is affected by changes in the modal shape caused by internal damping from the point of view of the distribution characteristics.
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