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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]

Top-of-rail (TOR) products are used in railways to reduce wear and noise by providing an intermediate friction level and a positive creep curve. In addition to these general requirements, retentivity and carry distance are important for their effectiveness on the track. This study aims to determine these track performance parameters for three commercial TOR products. A contact simulator and portable tribometer were used to simulate track conditions. The results show that carry distance is the most limiting performance parameter of TOR products, especially for water-based products. TOR lubricants, on the other hand, caused a more significant drop in friction after application. A predictive model simulating product redistribution along the track was introduced for the best-performing product. • Introduction of an innovative TOR benchmarking methodology. • Tribological testing of TOR products under conditions similar to track conditions. • Comparative analysis of three TOR products using various performance parameters. • A predictive model simulating TOR product redistribution is proposed. • Correlation with the methodology developed for small-scale tribometers. [ABSTRACT FROM AUTHOR]

Top-of-rail (TOR) products are designed to optimize adhesion, reduce wear and mitigate noise from the wheel-rail interface. Prior to testing these products in field conditions, a laboratory approach is suitable because it is not time-consuming and expensive. This study aims to design a benchmarking methodology to investigate the performance of TOR products using a standard tribometer in a ball-on-disc configuration. The resulting methodology is based on a multi-parameter approach enabling the assessment of TOR products from multiple perspectives. The core of the methodology is formed by traction tests and a robust evaluation phase resulting in a performance map dividing TOR products into four performance classes, Q1-Q4, based on which a suitable TOR product can be chosen for further testing. • A benchmarking methodology for the assessment of TOR products is introduced. • Tribological testing of TOR products using a ball-on-disc tribometer. • The multi-parametric approach is used to assess the performance of TOR products. • TOR products are classified into four performance classes Q1-Q4. • The frictional behaviour of FM and TORL is compared and contrasted. [ABSTRACT FROM AUTHOR]

Previous third body studies for wheel/rail are mainly concentrated on water or oil condition. However, friction modifiers (FMs) represent a new approach to managing adhesion coefficient in wheel/rail interface. In this paper, the position of the FM-air meniscus was given as input parameter, the thickness of FM can be solved easily with the multi-grid method. Non-Newtonian fluid model and micro-EHL analysis combined to obtain the relation between the adhesion coefficient and the quantity of FM. The results show that the quantity of FM has a significant effect on the initial adhesion coefficient within a certain range. Besides, the initial adhesion coefficient decreases gradually until it reach stable value with the increase of the quantity of FM. • A friction modifier (FM) starved EHL numerical model considering the applied amounts was established. • The accuracy of the model was verified by experiments with water and glycerol solutions. • The presented model shows a good accuracy in predicting the applied amounts of FM. • The adhesion coefficient increases with the surface roughness increases, while the film thickness increases. • The adhesion coefficient decreases with the applied amounts of FM increases in a certain range. [ABSTRACT FROM AUTHOR]