Abstract
Carmakers are paying attention to the definition of a high comfort level that matches the development of new products.
It is possible to estimate problems of vibration insulation for passengers through a testing work which aims to obtain acceleration signals in different parts of the car during some typical manoeuvres. This testing activity is usually supported by several numerical simulations to locate each sub system contribution to total vibration response; among these special attention is paid to suspension systems, for they are an important phase of road roughness filtering.
In this research we present a new case-study in which a twist beam rear axle suspension has been investigated towards N.V.H. aspects.
Due to the particular design of the twist beam axle the commonly adopted Multi-body approach is not able to catch the influence of the structural modal response of the axle to the road excitations.
In this case we had to search the relationship between cause and effect by two different numerical methodologies reproducing respectively comfort track input on FEM model and obstacle passing input on Multi-body model.
As far as the first one is concerned, we fix the natural mode shapes of the structure in the frequency range used to define the road excitation of a comfort track, through F.E. modelling. Following this approach we finally obtain the suspension global response in terms of acceleration of its points car body attachments.
As far as the second one is concerned, we deal with a modelling of the architecture in Multi - body environment to catch possible problems pertinent to suspension elastic components bumping, through non linear analysis in the time domain.
The correlation between the results coming from the two methodologies led us to run a trade-off analysis of the possible design solutions. Finally a hydraulic bushing was introduced in the assembly design to damp undesirable vibration in a well defined range of frequency. The adopted methodology looks to be promising for future applications, the major advantages coming from the possibility to prevent N.V.H. criticality at the first steps of the design concept.