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This paper presents a modeling method for prediction of low-frequency road noise in a steady-state condition where rotating tires are excited by actual road profile undulation input. The proposed finite element (FE) tire model contains not only additional geometric stiffness related to inflation pressure and axle load but also Coriolis force and centrifugal force effects caused by tire rotation for precise road noise simulation. Road inputs act on the nodes of each rib in the contact patch of the stationary tire model and move along them at the driving velocity. The nodes are enforced to displace in frequency domain based on the measured road profile. Tire model accuracy was confirmed by the spindle forces on the rotating chassis drum up to 100Hz where Coriolis force effect should be considered. Full vehicle simulation results showed good agreement with the vibration measurement of front/rear suspension at two driving velocities.

This paper presents progressive techniques based on the previous SAE papers [1], [2] for vibration transmission analysis (VTA) on finite element (FE) model using Transfer Path Analysis (TPA). The techniques are: 1) a contribution calculation technique for structure with manifold and continuous transfer paths: 2) a visualization technique of the influence degree for efficient derivation of measures for response reduction. In VTA, influence degree of each DOF is calculated based on TPA. In order to understand characteristics of vibration transmission (VT) easily and visually by engineers, magnitude of influence degree is expressed by replacement to magnitude of displacement in the diagram of FE vibration shape. This visualization technique is applied to an automotive body structure. The proposed techniques are applied to automotive body structure consisting of members and panels. The members are such as pillars, cross members and side members, which are the main VT paths.

This paper describes a proposal of techniques to analyze transmission of vibration among the parts or components of an automotive body structure using Transfer Path Analysis (TPA) [1]. TPA has not been applied to automotive body structure itself. One of the reasons is troublesome processes on the application to be treated with a lot of transfer functions and transmitted forces at the conjunctions which are complexly assembled with many adjacent nodes. Therefore it would be difficult to detect highly contributed parts or components in the structure. Difficulties were resolved by introduction of a proper coordinate transformation of analytical degree of freedom (DOF) at the cross-section of parts or components in this study. These describe the transmission of vibration using physical aspects of vibration transmission theories familiar to engineers like those of beam or shell. Contribution analysis of vibration was carried out for its upper side and under side of the body structure.

An approach to efficiently analyze many modes for forced vibration by mode grouping is proposed. This is an evolutionary application of the previous study [1] to automotive body with high mode density. Ongoing progress of simulation technology on noise and vibration (NV) by Computer Aided Engineering (CAE) has extended frequency range. Although this progress is welcomed by NV engineers and is desirable for automobile development, it requires engineers to spend much time for examining many mode shapes and so on. Usage of a concept of mode grouping was proposed to break the deadlock [1]. This concept was based on similarity of the effects of modifications, which were made on the noticed portions of the structure. However this approach was insufficient to actual automotive body structure because of inadequate estimation of frequency response sensitivity in high mode density et cetera. In this study, practical techniques are added to improve the insufficiencies.