Study on the optimization of solid particle additives in top-of-rail friction modifiers based on a twin-disc testing apparatus

Top-of-rail friction modifiers are used to manage the friction on the top-of-rail and help alleviate corrugation, reduce noise, decrease material wear, etc. In this paper, five series of FM samples were prepared and tested using a twin-disc testing apparatus to optimize the solid particle parameters in the FM, aiming to achieve an intermediate adhesion level and a positive creep curve at the wheel-rail interface. The roles of every composition were explored and further the mass content of solid particles, the mass content ratio of lubrication to modifying particles, and the hardness and size of modifying particles were optimized. The possible influence mechanism of FM third body layer shear strength on the wheel-rail adhesion behaviour was discussed based on the Coulomb-Mohr theory. The FM sample containing 76.31 wt% of water, 2.77 wt% of carboxymethyl cellulose (CMC), 10.46 wt% of resin, 3.04 wt% of graphite particles, and 9.13 wt% of kaolin particles can reduce adhesion coefficient to 0.129 and generate an obvious positive creep curve in the wheel-rail interface.