Multibody Syst Dyn DOI 10.1007/s11044-013-9400-9 An innovative degraded adhesion model for multibody applications in the railway field E. Meli · L. Pugi · A. Ridolfi Received: 26 June 2012 / Accepted: 13 September 2013 © Springer Science+Business Media Dordrecht 2013 Abstract The simulation of the braking maneuver of a railway vehicle under degraded ad- hesion conditions is very important concerning the safety of railway operation. However, the implementation of a realistic friction law is comparatively difficult because of the com- plex and nonlinear behavior of the wheel-rail contact. Particularly under degraded adhesion conditions, very high creepages occur, which cause sliding in the contact. This sliding pro- duces a high dissipation of energy, which has a cleaning effect on the rolling surfaces, and thereby strengthens the influence of the adhesion. In this work, this energetic criterion has been studied. The authors suggest implementing an innovative friction law to the simulation of railway multibody models with 3D multi-point contact detection algorithms. As a bench- mark case, the braking of a coach equipped with a Wheel Slide Protection (WSP) system is simulated. The results are compared with experimental data available from previous testing activities by Trenitalia. The new friction law provides to match the experimental reference results and to carry out simulated braking tests, including the working WSP system, which comply with the current regulations (Railway applications, braking, wheel slide protection, UNI EN 15595, 2009). Keywords Degraded adhesion conditions · WSP system · Friction recovery by energy principles · Multibody modelling of railway vehicles 1 Introduction The simulation of degraded adhesion conditions is fundamental in order to analyze the com- plex interactions, which often arise between different mechatronic on-board subsystems and E. Meli · L. Pugi · A. Ridolfi (B ) Department of Industrial Engineering, University of Florence, Via S. Marta n. 3, 50139 Florence, Italy e-mail: a.ridolfi@unifi.it E. Meli e-mail: enrico.meli@unifi.it L. Pugi e-mail: luca.pugi@unifi.it