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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.

This paper describes a proposal of techniques on Transfer Path Analysis (TPA) to analyze transmission of vibration among the components in a complex structure. This proposal is evolved from the previous one [1] in the dimension which dominates the quality of the analysis in automotive body structure by TPA. The proper coordinate transformation was introduced to resolve the troublesome process on the application of the body structure in the previous proposal. The complications are caused by the treatment with a lot of transfer functions and transmitted forces at the conjunctions that are complexly assembled with many adjacent nodes. Dimension of the analytical region is expanded from two to three in this study. That is, from the cross section of interface of components to the structure itself where the vibration transmits between two components.

A new method to predict low-frequency brake squeal occurrence was developed and guidelines for its elimination were formulated. First, a characteristic of the phenomenon was investigated using a simplified three-degree-of-freedom system model to obtain guidelines for squeal elimination, such as the natural frequency ratio of the brake rotor and caliper, an equivalent mass ratio of the brake rotor and caliper and the natural frequency and damping coefficient of the dynamic absorber. Then, a practical finite element model of the disk brake system was developed using Substructure Synthesis Method for design stage predictions. Finally, the usefulness of this method was confirmed by experimental validation.

Tire is a key to a good performance of road induced noise (road noise). Development of the performance would be more effective by deep consideration with suspension and wheel. Coupled vibration analysis between suspension and tire/wheel has given suggestions to understand and to improve their vibration. Next, it is applied to tire and wheel for a rumble noise around 160Hz in this paper. Successful and practical technique is developed for this analysis. It is a modal transformation of analytical degree of freedom (DOF) at their conjunction points. The DOF is reduced from seven hundreds to some tens and finally to two by transfer path analysis (TPA). By referencing results of numerical study, a set of modified tire and wheel is prepared. Its experimental results show the improvement of road noise and verify that this approach is useful practically.

A reliable finite element model (FE model) for the suspension of front-engine front-wheel-drive vehicles (FF vehicle) was developed. The model allows analysis which clarifies the role of each suspension component for road noise reduction in the 130- 160 Hz range. To analyze road noise up to 200 Hz, an accurate suspension FE model including tire FE model was developed. All suspension components are modeled in detail by shell or solid element. This saves the validation of model and enables us to use it early in the design stage. To save calculation time, some suspension components in which structure is not a concern are transformed into modal model. To acknowledge each subsystem's role to the entire suspension system a new approach was introduced. In this approach, important internal forces between subsystems are selected. These internal forces have high contribution to transmissibility forces at the body attachment point (body transmissibility force).