※一部利用できない機能があります
| 1.
論文 |
論文
|
山口, 誉夫 ; 永井, 健一 ; 丸山, 真一 ; 斉藤, 友明
概要:
application/pdf<br />Journal Article<br />This paper describes vibration analysis using finite element method for two viscoelastic blocks connected by a nonlinear concentrated spring. One of the blocks is supported by another linear
…
concentrated spring. The restoring force of the nonlinear concentrated spring has cubic nonlinearity and linear hysteresis damping. Finite element for the nonlinear spring is expressed and is connected to the viscoelastic blocks modeled by linear solid finite elements in consideration with complex modulus of elasticity. Further, the discretized equations in physical coordinate are transformed into the nonlinear ordinary coupled equations using normal coordinate corresponding to linear natural modes. This transformation yields computation efficiency. Influences of share of dissipated energy on nonlinear frequency responses for the viscoelastic blocks are clarifi
続きを見る
|
||
| 2.
論文 |
論文
|
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
…
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.
続きを見る
|
||
| 3.
論文 |
論文
|
山口, 誉夫 ; 津川, 純一 ; 岡部, 雅哉 ; 榎本, 秀喜 ; 黒沢, 良夫
概要:
application/pdf<br />Journal Article<br />This paper deals with analysis for positioning of sound absorbing materials in a muffler having expansion chamber. Elements of absorber 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 absorber is arranged in muffler according to this contribution. It proposed a positioning method of sound absorbers within the limits of design feasible region and it applied to the expansion type muffler and availability of this method is verified.
続きを見る
|
||
| 4.
論文 |
論文
|
金, 哲紅 ; 三輪, 卓 ; 陳, 志超 ; 長屋, 幸助
概要:
application/pdf<br />Journal Article<br />The new sealant layer is presented, which is easier to include into the manufacture process of the tire in comparison with the previous research. The performance of the present tire was
…
investigated, and it was clarified that there was no air leak when nails broke it. Vibration characteristics of the present tire were analyzed theoretically and experimentally, and the effects of the sealant on the road-ability and the road noise were investigated. Using the analysis, it is shown that vibration transmissibility decreases in the present. The impact characteristics are also discussed. The transmissibility is also decrease when the impact load applies to the tire, and load noise is also decreased.
続きを見る
|
||
| 5.
論文 |
論文
|
山口, 誉夫 ; 中本, 英良 ; 黒沢, 良夫 ; 松村, 修二
概要:
application/pdf<br />Journal Article<br />A numerical method is proposed to calculate dynamic dissipated energy for mixed structures including elastic body, viscoelastic body and porous body. A expression to calculate share of dissipated
…
energy for an each element in mixed structures is derived. Using this expression, vibration transmition properties are analyzed for mixed structures composed of porous media sandwiched between steel beam and plastic sheet. Further, a spacer is installed between the steel beam and the plastic sheet in the structures, to analyze deterioration of vibration by the sound bridge phenomena.
続きを見る
|
||
| 6.
論文 |
論文
|
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
…
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.
続きを見る
|
||
| 7.
論文 |
論文
|
黒沢, 良夫 ; 山口, 誉夫 ; 榎本, 秀喜 ; 松村, 修二
概要:
application/pdf<br />Journal Article<br />We have developed a technique for estimating vibrations of vehicle body struct
…
ures with damping materials using large-scale finite element (FE) model, which will enable us to grasp and to reduce high-frequency road noise (200～500Hz). In the new technique, first order solutions for modal loss factors are derived applying asymptotic method. This method saves calculation time to estimate modal damping as a practical tool in the design stages of the body structures. Frequency responses were calculated using this technique and the results almost agreed with the test results. This technique can show the effect of damping materials on automotive body panels, and it enables the more efficient layout of the damping materials. Further, we clarified damping properties of car structures under coupled vibration between frames and panels with viscoelastic layers.
続きを見る
|
||
| 8.
論文 |
論文
|
赤松, 克児 ; 山口, 誉夫
概要:
application/pdf<br />Journal Article<br />The acoustic radiation from baffled finite plates with free visco-lastic damping layers excited by a random point force have been studied in order to evaluate damping treatment performances
…
under the condition of neglecting fluid loading due to the back reaction of the radiated acoustic pressure. The plates are rectangular and clamped at the boundaries. The vibration responses of plates with damping layers are obtained by the finite element method. Modal damping ratios are estimated from undamped normal mode results by means of the modal strain energy method.The expressions for the surface acoustic intensity and the radiated sound power are derived in the transform formulation and evaluated numerically from the discrete Fourier transform of the vibration velocity responses of the plates in the spatial co-ordinates. An experimental study is carried out to measure the surface intensity distributions and to compare them with the analytical results.
続きを見る
|
||
| 9.
論文 |
論文
|
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
…
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.
続きを見る
|
||
| 10.
論文 |
論文
|
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
…
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.
続きを見る
|
||
| 11.
論文 |
論文
|
山口, 誉夫 ; 黒沢, 良夫 ; 松村, 修二
概要:
application/pdf<br />Journal Article<br />A numerical method is proposed to calculate damping properties for sound-proof structures involving solid body, porous media and air in two dimensional regions. Both effective density and bulk
…
modulus have complex quantities to represent damped sound fields in the porous media. Particle displacements in the media are discretised using finite element method. For solid body, displacements are modeled using conventional finite elements including complex modulus of elasticity. Displacement vectors at common unknown varriables, are solved under coupled condition between solid body, porous media and air. Further, explicit expressions of modal loss factor for the mixed structures are derived using asymptotic method. The proposed methods yield appropriate results for some sample problems. Moreover, it is found that damping can be coupled in the mixed structures.
続きを見る
|
||
| 12.
論文 |
論文
|
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
…
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.
続きを見る
|
||
| 13.
論文 |
論文
|
赤松, 克児 ; 山口, 誉夫 ; 金澤, 純一
概要:
application/pdf<br />Journal Article<br />The effects of structural damping and wavenuwmber ratio on the acoustic power radiated by point-excited damped infinite beams and simply supported finite beams with same cross sections have
…
been studied. The numerical calculations of the acoustic power were carried out using Keltie's equations based on the Heckl's power integral. The acoustic medium is assumed to be air, and the effect of the back reaction of the sound field is neglected in the beam response equation. Non-dimensional acoustic power, sound radiation efficiency, and acoustic power conversion efficiencies are presented as functions of wavenumber ratio and beam loss factors. It is shown that the power conversion efficiency of the infinite beam is inversely proportional to the wavenumber ratio and independent of the loss factor below coincidence, and is approximately proportional in inverse to the loss factor above coincidence. The power conversion efficiency of the finite beam has dull peaks with values roughly inverse-proportional to the loss factor at nonresonant frequencies. The similarity of acoustic power radiation between infinite beams and finite beams has been observed when the length and loss factor of beams is increased.
続きを見る
|
