Keywords: virtual homologation, damper models.

The accuracy and reliability of virtual homologation are not only affected by the use of a proper numerical process to virtually reproduce a line test, but also greatly depend on the accuracy of the multi-body (MB) model used in the virtual homologation process. This is clearly one major issue with exploring the possibilities for virtual homologation, since the accuracy of MB models based on the most updated techniques could be easily hindered by the use of inadequate models for suspension components.

This paper investigates the importance of component modelling when dealing with virtual homologation. The damper component is considered in this paper, being one of the most important components in the vehicle dynamic. Comfort, safety and stability issues generally involve the performance of dampers, mainly the component is critical when referring to stability behaviour.

An additional key issue, highlighted in the paper, in the definition of a reliable virtual homologation process is the identification of the model parameters, which can be carried out either based on suppliers' data, or on laboratory measurements. Infact sometimes unfortunately the use of data coming from suppliers is not sufficient to guarantee the model a good level of accuracy.

In this paper, firstly a characterisation of the oil damper is proposed by means of experimental tests. General information on this component in the design stage is often incomplete, i.e. component stiffness associated with damper flexibility is frequently unknown. Experiments, carried out accounting for the component working conditions and standard requirements, are demonstrated to be extremely useful at the design stage because they are able to provide useful information on the component performances.

Subsequently two different types of models (i.e. a linear Maxwell model and a non-linear Maxwell model) are defined in order to account both for a frequency dependent behaviour identified during testing and for non-linearities in the component behaviour (e.g. lamination valve). Additionally the proposed models are contemporarily efficient from a computational point of view as well as numerically robust.

The models are compared and differences quantified and evaluated. A procedure for model parameter identification based on experimental data is proposed and tested. Finally based on the experimental force-velocity diagram the non-linear Maxwell model is adopted to replicate the behaviour of a secondary vertical damper, the results are compared with experiments and show a good agreement.

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