Simulation of railway braking tests under degraded adhesion conditions

The simulation of the railway braking under degraded adhesion conditions is very important concerning the safety of the railway network; unfortunately a realistic adhesion law is not so easy to be implemented because of the complex and non-linear behaviour of the adhesion coefficient. Particularly under degraded adhesion conditions very high slidings occur and they usually produce a high dissipation of energy which has a cleaning effect on the rolling surfaces, increasing the adhesion coefficient. In this work this energetic criteria has been studied and the authors suggest to implement an innovative adhesion law to the simulation of railway multibody models with 3D multi-point contact algorithms. A benchmark case, the braking of a coach with WSP System is simulated and compared with experimental data available from previous testing activities by Trenitalia; the new adhesion law allows to match the experimental reference results and to carry out simulated braking tests, with working WSP system, that comply with the current regulations.