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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
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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
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| 2.
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山口, 誉夫 ; 中原, 直人 ; 永井, 健一 ; 丸山, 真一 ; 藤井, 雄作
概要:
application/pdf<br />Journal Article<br />This paper describes vibration analysis using finite element method for elastic blocks connected by a nonlinear concentrated spring. The restoring force of the spring is assumed to be
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expressed by power series of the relative displacement between ends of the spring. Finite element for the nonlinear spring is expressed and is connected to the elastic blocks modeled by linear solid finite elements. 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 Young's modulus on nonlinear frequency responses for the elastic block are clarified.
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| 3.
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山口, 誉夫 ; 酒匂, 淳一 ; 永井, 健一 ; 丸山, 真一
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application/pdf<br />Journal Article<br />For chaotic vibrations involving dynamic through generated in a post-buckled beam, influences of an axial displacement on dynamic properties in chaos are clarified by numerical analysis.
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Especially, the chaotic vibrations bifurcated from 1/2 subharmonic resonance are focused on. The beam is constrained by an axial elastic support and both ends of the beam are clamped. Applying Galerkin method to the basic equation of the buckled beam in consideration with geometric nonlinearity, nonlinear cubic simultaneous equations in multi-degrees of freedom are reduced. Further, the equations are transformed into nonlinear ordinary differential equations using normal coordinates corresponding to linear natural modes. By integrating the equations numerically, time histories and Poincare sections are calculated. Moreover, Lyapunov dimension can be obtained using the evolution equations. According to the calculated results, initial axial displacements increase the number of governing modes in the chaos including dynamic snap-through.
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山口, 誉夫 ; 中本, 英良 ; 黒沢, 良夫 ; 松村, 修二
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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
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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.
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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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| 6.
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山口, 誉夫 ; 中原, 直人 ; 永井, 健一
概要:
application/pdf<br />Journal Article<br />This paper describes vibration analysis using finite element method for an elastic block supported by a nonlinear concentrated spring. This block is connected to another block by a
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linear concentrated spring. The restoring force of the nonlinear spring has cubic nonlinearity. In this system, resonance responses mainly involve nonlinearity due to two vibration modes. Finite element for the nonlinear spring is expressed. Then the nonlinear spring element and linear spring element are combined to the elastic blocks modeled by linear solid finite elements. Further, the discretized equations in physical coordinate are transformed into the nonlinear ordinary coupled differential equations using normal coordinate corresponding to linear natural modes. This transformation yields computation efficiency. Influences of Young's modulus on frequency responses are clarifed.
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山口, 誉夫 ; 永井, 健一 ; 丸山, 真一 ; 油田, 知宏
概要:
application/pdf<br />Journal Article<br />This paper describes vibration analysis using finite element method for an elastic block supported by a nonlinear concentrated spring. The restoring force of the spring has cubic
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nonlinearity. Finite element for the nonlinear spring is expressed and is connected to the elastic block modeled by linear solid finite elements. 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 Young's modulus on nonlinear frequency responses for the elastic block are clarified.
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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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| 10.
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山口, 誉夫 ; 黒沢, 良夫 ; 松村, 修二
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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
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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.
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