The project is motivated by the issue of low adhesion in wheel-rail contacts, which can cause serious problems with traction and braking in railways. This issue is frequently connected to the ‘wet-rail’ phenomenon where the contact is naturally contaminated with a mixture of water and solid particles. At a critical particle concentration, a significant drop in the friction coefficient can be observed. Although the phenomenon is well known from railway operations, the physical relationships are not yet fully understood. The aim is to provide experimental evidence of the transient nature of the phenomenon in rolling contacts contaminated with a water-particle suspension based on optical observation of the contact and to provide a physics-based model describing this phenomenon in its full complexity. Ball-on-disc optical tribometer combined with thin-film colorimetric interferometry and fluorescence imaging will be used for fluid film thickness and flow measurement. Particle-based simulations (DEM) will be coupled with flow simulations between rough wheel-rail surfaces.

Keywords
contact;friction;wheel/rail interface;solid particles; suspension