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Top–of–rail friction modifiers (FMs) represent an up–to–date approach to managing adhesion in the wheel–rail interface. The aim of this study was to investigate the role of typical water–based FM constituents in terms of adhesion and film formation. The ball–on–disc apparatus was employed to reach a rolling–sliding contact. The friction behaviour of various complex substances with different compositions was investigated in terms of adhesion and wear. The results showed that less complex substances, e.g. free of particles for friction modification, can provide required adhesion. Moreover, adhesion was not markedly decreased when the contact was overdosed. The performance of water–based substance/FM is greatly affected by evaporation of water. Surface analyses showed that substances are able to reduce wear and surface damage. [ABSTRACT FROM AUTHOR]

The wheel-rail contact is subjected to various environmental contaminations, while one of the most common is water. A numerical model has been used to evaluate friction in water-contaminated contact. The Greenwood and Tripp theory is used to calculate the load carried by asperities and liquid film. This model uses Kalker's simplified theory with an implemented third body layer to determine the frictional values of asperity contact and elastohydrodynamic theory for friction generated by liquid. The results are compared with experiments on two types of surface roughness. The results show the difference between elastic and plastic asperity deformation model, where the plastic model predicts more accurate transition in mixed lubrication regime. The plastic deformation model was used to predict traction curves. • Numerical model for prediction of friction in water-contaminated contact was proposed. • Film thickness of water was measured and compared with prediction. • Model accounting for plastic deformations compared well with experimental data. • Traction curves for different speed were measured and compared with the model. [ABSTRACT FROM AUTHOR]

The friction properties of the wheel-rail contact are characterized by a coefficient of traction (CoT), which can be affected by many contaminants. Numerous devices for assessing CoT are available; however, only a small number of them are capable of recording creep curves. This work introduced a rail-mounted tribometer that uses controlled changes in braking torque on a measuring wheel to induce creep in the contact. A methodology for assessing creep curve parameters was proposed, utilizing both analytical and numerical models of the contact. The experiments were performed both in the field and in the laboratory to investigate the effect of railhead conditions under various contact pressures and to track the evolution of the CoT during a measurement. • The new portable rail tribometer can record entire creep curve within one pass. • Modified FASTSIM and Polach's model are used to evaluate creep curve parameters. • Proposed approach was verified for various contact conditions. • Solvent significantly reduces the durability of the real 3rd body layer. [ABSTRACT FROM AUTHOR]