Viscoelastic damping materials are laminated on car body panels to reduce structure borne noise. Properties of simple structures(e.g. flat plates, straight beams) with the damping layer have already been clarified by many researchers. However the damped properties of body structures have not yet been investigated in detail, because panels in the structures have three-dimensional complicated configurations by their beads and curvatures. Moreover, the panels are complexly connected to the body frames, which affects on the vibration behaviors significantly. Prediction methods have been studied using large scaled FEM (finite element method) and MSE(modal strain energy method). The calculated damping properties of these structures are compared with those of experimental results. Both results are consistent. We also report that modal damping is sensitively varied by the geometry of the body panels. We describe the effects on damping concerning geometry(length and height) of the beads, rise in the curved plates with no constant radius, and rigidity in connection between panels and frames.
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