Study of Adhesion Recovery phenomenon using a Multi-axle Roller-rig

When a railway vehicle is running on a contaminated track, the available friction is reduced, and large creep values arise at the wheel-rail interface. However, the work of the friction forces of the leading wheelsets produces a cleaning effect on both the track and the wheels, so that the contaminant layer is partially removed, and adhesion increases on the leading as well as on the trailing wheelsets. The investigation of these adhesion recovery phenomena is the key to develop new solutions aiming to improve the vehicle dynamic behaviour in degraded adhesion conditions. Since on-field tests are usually expensive and time-consuming, roller-rigs are the typical apparatus used to simulate the vehicle dynamic behaviour in laboratory conditions. The paper describes the mechanical design of an innovative roller rig specifically designed to study adhesion recovery phenomena, consisting of four wheelsets running over the same pair of rollers. Experimental tests are performed on the test bench to obtain adhesion characteristics under dry and contaminated conditions

Development of numerical and experimental tools for the simulation of train braking operations

L'abstract è presente nell'allegato / the abstract is in the attachmen

A Novel Analytical Method to Calculate Wheel-Rail Tangential Forces and Validation on a Scaled Roller-Rig

The study of railway dynamic strongly depends on the estimation of the tangential forces acting between wheel and rail. Simulation of the dynamical behaviour of railway vehicles is often performed using multibody codes, and the calculation of the contact forces must be efficient and accurate, even if the contact problem is strongly nonlinear. Therefore, the contact problem is still of great interest for researchers. This work proposes an analytical and efficient algorithm to calculate wheel-rail tangential forces. The proposed method is compared with the most commonly used algorithms under different conditions. In addition, experimental tests are performed on a scaled prototype on roller-rig to demonstrate that the method can be easily adjusted using experimental results. The benefit of the proposed method is to provide an analytical and fast solution, able to obtain accurate results and to allow corrections based on empirical evidence