Development of an innovative wheel-rail contact model for the analysis of degraded adhesion in railway systems

摘要

A detailed description of adhesion is crucial in tribology, vehicle dynamics and railway systems, both theoretically and practically. However, an accurate adhesion model is quite hard to develop because of the complex and non-linear behaviour of the adhesion coefficient and the external unknown contaminants which are present between the contact surfaces. The problem becomes even more complicated when degraded adhesion and large sliding between the contact bodies (for instance wheel and rail) occur. In this paper the authors describe an innovative adhesion model aimed at increasing the accuracy in reproducing degraded adhesion conditions in vehicle dynamics and railway systems; the new approach turns out to be quite suitable also for multibody applications (fundamental in this research topic). The model studied in the work considers some of the main phenomena behind the degraded adhesion: the large sliding at the contact interface, the high energy dissipation, the consequent cleaning effect on the contact surfaces and, finally, the adhesion recovery due to the external unknown contaminant removal. The new adhesion model has been validated through experimental data provided by Trenitalia S.p.A. and coming from on-track tests carried out in Velim (Czech Republic) on a straight railway track characterised by degraded adhesion conditions. The tests have been performed with the railway vehicle UIC-Z1 equipped with a fully-working Wheel Slide Protection (WSP) system. The validation showed the good performances of the adhesion model both in terms of accuracy and in terms of numerical efficiency; high computational performances are required to implement the developed model directly online within more general and complex multibody models (e.g. in Matlab-Simulink and Simpack environments). In conclusion, the adhesion model highlighted the capability of well reproducing the complex phenomena behind the degraded adhesion.