Investigations of Passenger Vehicle Vibration Behaviour as Basis for a Finite-Element Representation

The problems that have until now prevented the practical application of a Finite-Element (FE) calculation in passenger vehicle acoustics are identified and their causes investigated.

First of all, measurements of vibration scatter in "bodies in white" and complete vehicles provided tolerances for the FE-Model prediction accuracy.

The investigations in the dynamic properties of the total vehicle's constituent parts and the subsequently based build up of the "body in white" FE-Model is seen to be decisive.

Measurements of a "body in white" and a complete vehicle in a vacuum changer, to determine the effect of the air vibration on the structure vibration, led to important conclusions in the FE-Model conception which strongly differ from former representations. Based on these results the validity of an uncoupled air-cavity-model excited with measured structure vibration has been tested, from which clear indications were given at which points the structure model needs to be refined. In close connection with the problem of coupling between the structure and air cavity, physical causes were sought for the high damping of the air vibrations in the interior cavity model and if possible these to harmonize with the model assumptions