Driveline Structure-Borne Vibration and Noise Path Analysis of an AWD Vehicle Using Finite Elements

In both rear-wheel drive and all-wheel drive vehicles, the driveline is a significant source of noise and vibration phenomena which can potentially translate into customer dissatisfaction. Special care must therefore be taken to the design of the entire powertrain mounting system, as well as to the body-in-prime sensitivities at the points to which the mounts are attached, so that acceptable vibration and noise levels are obtained. Among all the vibration and noise generation mechanisms usually present in a rotating shaft such as driveline, imbalance plays a dominant role, being often the main focus of attention by development engineers. This work presents a CAE study carried out for an all-wheel drive vehicle using finite element models for both the body-in-prime and driveline system, aiming at decreasing the vibration level at the driver's seat track. Unit imbalance masses were applied at three diferent points on the driveline and the forces on the powertrain mounts were evaluated. On the other hand, body-in-prime transfer functions from the mounts to driver's seat track were also obtained. A careful examination of both results makes it possible to identify the most critical vibration transfer paths, yielding an important piece of information to assist the choice of an optimal vibration reduction action. The paper also shows the effect on the vibration level of adding tuned dampers to the rear differential, which was identified to be the main vibration transfer path.