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The need of lightweight vehicle design is motivated by the recent global trend of less fuel consumption and lower emission in vehicle. However in NVH development of vehicle, it becomes more difficult for the lightweight vehicle to reach low vibro-acoustic sensitivity than, for the heavy weight one to do so. Inthis environment, this paper describes about the practical finite element (FE) modeling of vehicle structure and acoustics, in order to predict "boom" response to powertrain excitation. The FE modeling process through validation and updating with experimental mode makes, the accumulation of considerable expertise for improving prediction accuracy, possible. FE analysis based on this modeling process is so useful for predicting "boom" levels up to 200 Hz. Using the result of FE analysis, structural optimization is executed in order to improve "boom" level of 80 Hz.

A new method for analyzing idle shake is discussed. A primary design technique of engine mount systems and vehicle bodies in the early development stage is proposed. In general, specifications for the engine mount system, which is composed of several insulator rubbers, are determined by certain criteria of transmissibilities of engine excitation forces to the rigid foundation. However, when the transmitted forces are applied to a flexible body, the resultant response of the body depends not only on the transmissibilities of the isolation system, but on vibratory characteristics of the flexible body. Therefore, the body needs to be taken into account for antivibration design as well as the engine mount system. Besides, the engine mount and the body cannot be evaluated by simple criteria due to the several insulator rubbers which feature many transmissibilities and transfer functions.

An analysis of the static behavior of T-shaped joint is presented. Advanced testings by laser holography and infrared ray stress wave analyzers verified the surface deformation and the stress concentration of joint area, which are very important factors of thin-walled joint stiffness. The definition of structural joint stiffness is attempted, and the relationship between structural joint stiffness and sizes(dimension) of the constructing members is obtained in case of a thin-walled T-shaped member with rectangular cross section. The parametric study to accomplish weight reduction, while maintaining the necessary structural joint stiffness, is described in case of Rocker to Center pillar. The numerical analysis of body structure considering the structural joint stiffness shows better accuracy as compared with the analysis with the joint assumed rigid.