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PROCEEDINGS OF THE SECOND INTERNATIONAL CONFERENCE ON RAILWAY TECHNOLOGY: RESEARCH, DEVELOPMENT AND MAINTENANCE
Edited by: J. Pombo
An Innovative Adhesion Model for Railway Applications
B. Allotta, E. Meli, L. Pugi and A. Ridolfi
Department of Industrial Engineering, University of Florence, Florence, Italy
B. Allotta, E. Meli, L. Pugi, A. Ridolfi, "An Innovative Adhesion Model for Railway Applications", in J. Pombo, (Editor), "Proceedings of the Second International Conference on Railway Technology: Research, Development and Maintenance", Civil-Comp Press, Stirlingshire, UK, Paper 187, 2014. doi:10.4203/ccp.104.187
Keywords: wheel-rail adhesion, degraded adhesion conditions, wheel-rail contact, multibody modelling, railway vehicles.
The accurate modelling of the adhesion plays a fundamental role in tribology, vehicle dynamics and railway systems, both from a theoretical and a practical point of view. However, a realistic adhesion law is quite difficult to obtain because of the complex and non-linear behaviour of the adhesion coefficient and the presence of external unknown contaminants; this is especially true when degraded adhesion and large sliding between the contact surfaces (for instance wheel and rail) occurs. In this paper the authors present an adhesion model particularly developed for describing degraded adhesion conditions in vehicle dynamics and railway systems; the new approach is also quite suitable for multibody applications (very important in the considered research areas). The model analysed in this paper is based on some of the main phenomena characterising the degraded adhesion, such as large sliding at the contact interface, high energy dissipation, the consequent cleaning effect on the contact surfaces and the final adhesion recovery due to the removal of external unknown contaminants. The adhesion model has been validated thanks to experimental data provided by Trenitalia S.p.A. coming from on-track tests performed in Velim (Czech Republic) with the railway vehicle UIC-Z1. The tests have been carried out on a straight railway track under degraded adhesion conditions with a vehicle equipped with a fully-working wheel slide protection system. The validation highlighted the good performances of the adhesion model in terms of accuracy and numerical efficiency; in this case high computational performances are essential to implement the developed model directly online within more general multibody models (e.g. in Matlab-Simulink and Simpack environments). In conclusion, the adhesion model turned out to be able to well reproduce the complex phenomena behind the degraded adhesion.
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