Microstructure evolution and damage development in the rails of a single-track railway line after preventive grinding

Abstract

In sparsely populated areas single-track railway lines are still common. Despite the low-density traffic and low axle loads, rail damage is observed to initiate in the rails of these lines. Not only large cracks requiring repair are found, but also newly initiated, post-grinding damage is observed. Rail specimens from the track containing representative damages are extracted to identify the reasons for the damage initiation in the R260Mn steel rail. At the rail surface, three years after the preventive grinding maintenance, the characteristic grinding facets and roughness patterns are still present. White etching layers are observed to surround the residual grinding grooves, maintaining the roughness as a result of the high wear resistance of these layers. The strain orientation at the gauge side of the rail is uni-directional due to lateral creep in the wheel–rail contact while in the center of the contact surface the strain patterns evidence shear stress reversal associated with the bi-directional traffic. The damage initiation mechanism after preventive grinding is associated with low-wear conditions and stresses concentrated around long-lasting grinding grooves. The findings show that preventive grinding maintenance specifications for regional single-stock railway lines must be improved. Specific points of interest are stringent requirements on the number of facets and surface roughness, as well as directions for the removal of corrugation.