Torsional Vibration Analysis of Powertrain and Driveline Using Finite Element Method

Among the lower frequency vehicle NVH problems, booming noise is one of the most concerned issues. One of the most common booming noise sources is the torsional vibration of the powertrain and driveline for rear-wheel drive and four-wheel drive vehicles. The solutions for this problem are either to use a torsional dynamic absorber or to use a lower stiffness clutch. Both solutions require the modal frequency of the torsional vibration mode of the powertrain and driveline. At early design stages, vehicle prototype is not available for measuring this frequency. Analytical method is usually used to calculate this frequency. Currently, mostly used method is the so-called 1D method in which the whole powertrain and driveline are represented by one-dimensionally connected disks (lumped inertia) and shaft (lumped stiffness). However, those lumped parameters are not always available at early design stage. In this paper, a method using finite element models is presented. In this method, all components in the powertrain and driveline are modeled by either three-dimensional solid mesh or two-dimensional shell mesh. The component FE models are connected together to construct the model for the whole powertrain and driveline based on the physical connections between them. The constructed FE model is used for modal analysis by MSC/Nastran. The results of the modal analysis will have the information of the torsional mode. To demonstrate this method, a rear-wheel drive vehicle will be included in the paper as a case study. Results of the modal testing and noise measurements will also be presented.