SAE International Evaluation of Trim Absorption to Exterior Dynamic and Acoustic Excitations Using a Hybrid Physical-Modal Approach 2014-01-2080

The NVH study of trimmed vehicle body is essential in improving the passenger comfort and optimizing the vehicle weight. Efficient modal finite-element approaches are widely used in the automotive industry for investigating the frequency response of large vibro-acoustic systems involving a body structure coupled to an acoustic cavity. In order to accurately account for the localized and frequency-dependant damping mechanism of the trim components, a direct physical approach is however preferred. Thus, a hybrid modal-physical approach combines both efficiency and accuracy for large trimmed body analysis. Dynamic loads and exterior acoustic loads can then be applied on the trimmed body model in order to evaluate the transfer functions between these loads and the acoustic response in the car compartment. The scenario study of installing different trim components into the vehicle provides information on the acoustic absorption and dynamic damping with regard to added vehicle weight by the trim. This paper demonstrates, through an industrial example, the creation of hybrid model of a trimmed vehicle body, the weakly coupled process of calculating and applying excitation from simplified tire noise on the vehicle's exterior surface, the effect of trim components on the interior noise reduction due to the exterior noise sources. Numerical results showed significant trim effect in increasing the noise reduction in the frequency interval between 300Hz and 500Hz.