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Recent trend towards the lighter car body and the higher performance of powertrain makes NVH engineers do much work. The vibrations at idle, engine starting and gear shift are critical because those are easily perceptible phenomena of car at idle. The enhancement can be obtained through the optimization of engine mount system because those are mainly caused by engine torque fluctuation. To shorten the development period, automotive engineers are willing to do extensive cooperated application of CAE with experiment in the process of car development. In this paper the strategy of integration of CAE and experiment is introduced to develop engine mount system efficiently at initial design stage.

Key on/off vibration on the vehicles comes from many characteristics of powertrain (P/T) system. It is the combination of source and transfer system. So, vibration can be refined by either source reduction or transfer system redesign. In this study, critical factors affecting the key on/off vibration have been identified. An improved example case will be presented from the source and transfer viewpoint. Engine mounting stiffness has been changed by simulation and experiment. The simulation method has been used to assist in the identification of the key design factors of engine mounting system. By determining the rotation angle of an engine mount that is critical factors to powertrain mode and movement, we have reduced key on/off vibration level. The experiment has been performed using an engine mount sample to build the confidence of simulation model. The test results have shown significant improvement of vehicle vibration in key on/off situation.

Identification of structure borne sound sources induced by the structural vibration of an automotive powertrain has been studied. Based on the principal component analysis which uses singular value decomposition of a matrix consisting of the auto- and cross-spectra, the operating vibrational analysis is performed. The quantitative description of the output power due to intrinsic incoherent source is addressed. The applicability of the technique is tested both numerically and experimentally. First, the coherence analysis is numerically carried out with a simple structure which is modeled as multi-input and single output to identify the structure borne noise generation process. Second, the actual vibrational behavior of a powertrain structure and the interior noise analysis of a car under the running condition are carried out. The technique is shown to be very effective in the identification of the structure borne noise sources.