DEM simulation of single sand grain crushing in sanded wheel–rail contacts

In railways, low adhesion conditions lead to problems in braking and traction. Sanding increases adhesion by blasting sand grains towards the wheel–rail contact. Which physical mechanisms increase adhesion during sanding is poorly understood, as research in this field has been almost exclusively experimental. This work is the first step in developing a DEM model describing the sanding process. Previous experimental studies involve single grain crushing tests focusing on initial breakage and repeated breakage under realistic wheel–rail contact pressures of 900 MPa. Tests on two types of rail sand under dry and wet contact conditions, showed different spread of fragments as well as the formation of clusters of solidified fragments at high stresses. The developed DEM model captures the observed behaviour for both types of sand, and both contact conditions. Combining experimental research and DEM modelling aims to improve the understanding of adhesion increasing mechanisms in sanded wheel–rail contacts.