Search Results

Tip-in/Tip-out of the accelerator pedal generates transient torque oscillations in the driveline. These oscillations may be amplified by P/T, suspension and body modes and will eventually be sensible at the receiver side in the vehicle, for example at the seat or at the steering-wheel. The forces that are active during this transient excitation are influenced by non-linear effects in both the suspension and the power train mounts. In order to understand the contribution of each of these forces to the total interior target response (e.g. seat rail vibration) a detailed investigation is performed. Traditional force identification methods are not suitable for low-frequent, transient phenomena like tip-in/tip-out. Mount stiffness method can not be used because of non-linear effects in the P/T and suspension mounts. Application of matrix inversion method based on trimmed body vibration transfer functions is not possible due to numerical condition problems.

Finite elements have been successfully used over the past decade to predict the vibro-acoustic behavior of complex large systems as encountered in the transportation industry. Nevertheless, some challenges are still not completely solved as for instance the modeling of multilayer porous materials used to reduce the noise in cavities. A simple model based on local impedance and added mass has been widely used in the past to model those acoustic trim materials at low frequency but shown limitations when the frequency range increases. To circumvent this limitation, approaches based on finite element formulations have been developed to model the poroelastic materials. They range from simple equivalent fluid models to complex models involving a solid phase and a fluid phase. However, those approaches require important modeling effort, computer memory and solution time. A unique approach to model acoustic trim material is presented in this paper.