The braking and traction performances in railway transportation are deeply connected with the concept of the wheel-rail adhesion. In degraded condition, when the rail contamination reduce the available adhesion, the attempt to transfer traction/braking effort to the rail could lead the wheelset in slip/slide condition. During the transition between pure-rolling regime and sliding regime, the adhesion value assumes the threshold value called adhesion limit. How this value changes according to the wheelset setup (train speed, axle load) and in different environmental conditions (uncontaminated, contaminated) cannot be rigorously studied through field tests due to the lack of controllability of several quantities, e.g. axle load, and for this reason laboratory tests using test rig simulators are needed.

Matteo Frea, Faiveley Transport Wabtec; Salvatore Perna, Roberto Tione