干旱区生态环境知识资源中心

In the virtual development of passenger cars, different simulation techniques can be applied at a very early stage. Besides the classical disciplines like crash and stiffness calculations, the numerical fatigue analysis is gaining more and more the attention of engineers. For this purpose, virtual prototypes of real vehicles are made to ride over digitised rugged test tracks. To reach the desired simulation quality, it is absolutely necessary that the vehicle model describes both the static arid the dynamic behaviour of the real vehicle properly. Early in the development process, the validation can be carried out by aggregate carriers. The final validation must be done by real prototypes.

This paper presents the results of a current development project where the holistic analysis of a vehicle prototype was carried out. Using the software toot ARMS and a multibody vehicle model, the forces between the suspension and the chassis of a passenger car are simulated. The digital test track is about 16 kilometres in length and consists of obstacles like belgium blocks, potholes, cleats and a handling area, where curve radii of about 10 metres are driven. Both the curvature of the track and the velocity profile are used as input data for the digital driver model. By varying these data it is possible to simulate the scattering associated with test drivers during handling manoeuvres, accelerating and braking.

In a second step, the rigid chassis model is refined and modelled as a modal flexible body. In this way, the stresses and strains in the chassis can be calculated directly and subsequently used for the fatigue analysis.

The validation of the dynamical vehicle model is based on the comparison of forces, accelerations, power density spectra and the load spectra etc., measured by an aggregate carrier on the one hand and calculated by the multibody simulation on the other hand.

For the fatigue analysis, the stress calculations are based on both the method of inertial relief and the method of modal stresses. Both the sheet metals and the spot welds are considered. Different software tools are tested. The advantages arid disadvantages of the numerical fatigue analysis are revealed by the comparison between the experimental and numerical results.