Yoshio Kurosawa

High Frequency Vibration Analysis of Automotive Bodies With Panels That Have Attached Viscoelastic Layers

A technique has been developed for estimating vibrations of an automotive body structures with viscoelastic 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 the viscoelastic damping materials on the automotive body panels, and it enables the more efficient layout of the viscoelastic damping materials. Further, we clarified damping properties of the automotive body structures under coupled vibration between frames and panels with the viscoelastic damping materials.Copyright

716 Dynamic Analysis of Dissipated Energy for Automotive Sound-proof Structures Including Elastic body, Viscoelastic body and Porous body using FEM in Sound Bridge Phenomena

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.

Fast finite‐element analysis for damping of automotive structures having elastic bodies, viscoelastic bodies, porous media, and gas

A numerical method is proposed to calculate damping properties for automotive soundproof structures involving solid bodies, porous media, and air in two‐dimensional regions. Both effective density and bulk modulus have a complex quantity to represent damped sound fields in the porous media. Particle displacements in the media are discretized using a finite‐element method. For damped solid bodies, displacements are formulated using conventional finite elements including complex modulus of elasticity. Displacement vectors as common unknown variables are solved under coupled condition between solid bodies, porous media, and gas. Further, by applying an asymptotic method to a complex eigenvalue problem, explicit expressions of modal loss factor for the mixed structures are derived. The proposed methods yield appropriate results for some typical problems and this method diminishes computational time for large‐scaled finite‐element models. Moreover, it is found that damping can be coupled in the mixed structure...