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論文
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山口, 誉夫 ; 津川, 純一 ; 榎本, 秀喜 ; 黒沢, 良夫
概要:
application/pdf<br />Journal Article<br />This paper deals with analysis for layout of sound absorbing materials in three-dimensional rooms using damping contributions with eigenvectors as weight coefficients. Elements of absorbing
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materials are modeled by 3D finite element, which having complex density and complex volume elasticity. By expanding the solution of complex eigenvalue problem with small parameter, equations of motion are derived using first order of asymptotic components. From the equations, contribution of damping elements on modal damping is derived in consideration of multiple modes. The sound absorbing materials are arranged in three-dimensional rooms according to this contribution and the components of eigenvectors at the evaluation points. The availability of this method is verified using an expansion type chamber.
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山口, 誉夫 ; 竹前, 康徳 ; 黒沢, 良夫 ; 松村, 修二
概要:
application/pdf<br />Journal Article<br />Body panels in automobiles are usually stiffened by beads and are covered with viscoelastic damping layers. In the first report, method of numerical analysis for modal loss factors of the bead
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panels were verified by experimental results. In the analysis, asymptotic method was applied to complex eigenvalue problem using three-dimensional FEM in consideration with complex material parameter. In the second report, influences of geometry (height, length, interval) of the beads on modal loss factors were clarified. In this report, layouting the viscoelastic materials on the surface of the bead panels using damping contributions of positions of the materials to modal loss factor properly, modal loss factors can be improved. Further, by investigating bead shapes which can concentrate distribution of dissipated energy on local area in the panels, effective shape of beads is proposed in consideration with modal loss factor, light weight and rigidity.
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山口, 誉夫 ; 黒沢, 良夫 ; 松村, 修二 ; 野村, 章
概要:
application/pdf<br />Journal Article<br />This paper describes vibration phenomena for stiffened elastic panels having viscoelastic damping layer. The panels are stiffened by beads. The laminated panels are modeled using
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three-dimensional finite elements in consideration with complex modulus of elasticity. Further, applying asymototic method to the discreted equations of motion, explicit expressions of modal loss factors for the laminates are derived. Consequently, the expressions have similar form to Modal Strain Energy Method, which is proposed by Jonson. Numerical code is developed related to the expressions. Vibration damping properties of the bead panels, which are calculated by the code, is consistent with experimental results. Temperature dependence of the damping properties by FEM also agreed well with the experiments. These investigations reveal that modal damping decreases due to beads of the panels.
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山口, 誉夫 ; 黒沢, 良夫 ; 松村, 修二 ; 村上, 聡 ; 澤田, 耕吉
概要:
application/pdf<br />Journal Article<br />Viscoelastic damping materials are laminated on car body panels to reduce structure borne noise. In usual, these panels are stiffened by beads. Damping properties of the panels are sensitively
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affected by their complicated configurations. In the first report, we studied about prediction methods of damping properties for both bead panels and actual vehicle models having non-constraint viscoelastic layer. Applying asymototic method to the discreted equations of FEM, explicit expressions of modal loss factors for the laminates were derived, and then were verified by experiment. In this report, sensitive effects of geometry of beads (e.g. length of beads, height of beads and so on) on modal damping were revealed in detail. Applying Inoue's method, we also analized damping phenomena on the bead panels using distribution of dissipated energy between inplane deformation and out of plane deformation.
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山口, 誉夫 ; 黒沢, 良夫 ; 松村, 修二
概要:
application/pdf<br />Journal Article<br />This paper deals with analysis for acoustic properties of three-dimensional closed sound fields having sound absorbing materials. In this analysis, the sound absorbers can have arbitrary
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shapes and can be located anywhere in the fields. The fields involve gas and sound absorbers which are modeled using Finite Element Method. A new three-dimensional element are developed for the absorbers. This element has two damping parameters which are complex density and complex volume elasticity. The elements are constructed, and then the corresponding simultaneously coupled equations are solved to obtain the frequency response. Further, a new expression is also derived to get distribution of contribution to modal damping for each element. These approachs are applied to three-dimensional rooms where the absorbers exist in different positions. The results are compared with the experiments carried out by Utsuno and are discussed.
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