Proceedings of the Institution of Mechanical Engineers, Part F: Journal of Rail and Rapid Transit

A field methodology to assess the performance of rail cleaning, using a new portable tribometer

B White 1, 2
, 
Michael Watson 2
, 
JOSEPH JAFFE 1
, 
R. A. Lewis 1
1
 
Department of Mechanical Engineering, The University of Sheffield, Sheffield, United Kingdom of Great Britain and Northern Ireland
2
 
Rivelin Rail, Sheffield, United Kingdom of Great Britain and Northern Ireland
Publication type: Journal Article
Publication date: 2025-02-14
scimago Q2
wos Q3
SJR: 0.644
CiteScore: 4.8
Impact factor: 1.7
ISSN: 09544097, 20413017
Abstract

Low adhesion between wheel and rail can be caused by autumn leaf fall, reacting and adhering with the steel, resulting in signals passed at danger, station overruns or in worst cases derailments and collisions. Various methods to remove this layer or increase friction have been developed including water jetting, abrasive cleaning, traction gels and chemical treatments, new interventions are trialled each year. However, representative low friction conditions are difficult to generate repeatedly and measure, as such the efficacy of these interventions remains difficult to establish. Twenty years ago British Rail Research stated “Paradoxically it has been the lack of low adhesion that has hindered the development of low adhesion remedies”. This still remains largely true today. In this paper a method is proposed to form a representative organic layer, by placing powdered leaf material on the railhead and rolling with a vehicle until it has blackened and bonded to the underlying steel. The layers were visually inspected using industry guidelines and their friction was measured using the new Rivelin Rail PRT300 tribometer. The method was found to be capable of reliably producing contamination levels from light to heavy as required for testing by varying the quantity of leaves added. Friction coefficients for medium and heavily contaminated rails were all below 0.05, these would typically be described as ultra-low adhesion. As an illustration of the method, a trial of a new (anonymised) railhead cleaning technique is included in this work as a case study. The layer formation and measurement methodology proposed could be adopted by the wider rail industry to provide a more data-driven approach to understanding friction enhancer and railhead cleaning technology performance, through optimising current treatments and assessing the performance of novel technology.

Found 17
By date By citations
The Royal Society
Pressure induced transformation of biomass to a highly durable, low friction film on steel
Lanigan J.L., Faas L., Butcher T., Skipper W.A., Silva M.P., Lewis R., Gomez L.D.
Proceedings of the Royal Society A: Mathematical, Physical and Engineering Sciences scimago Q1 wos Q1 Open Access , 
2024-02-14,  citations by CoLab: 2 ,  Abstract  
Herein the authors report a detailed insight into the tribological and chemical mechanisms that take place when leaf matter is present at the wheel/rail interface. The approach used enables further insight into the formation and subsequent effects on friction from leaf derived layers. Results shed insight on the process that facilitates the formation of leaf derived layers, their structure and chemical make-up. Our analysis indicates that polyphenols, a chemical family that include tannins, have an important role in layer formation and hypothesis on the layer's stability, when formed under high pressures. The data indicate that the high pressure found at the wheel/rail interface facilitates conversion of biomass into a tenacious, thin film. This is shown by the increase in the amount of phenolic compounds present. Phenolic compounds are typically rich in oxygen functional groups that have the ability to bind to metal ions. This insight into the composition of the film is expected to enable the development of novel remediation strategies. It highlights the potential for cleaning agents to be used as tools for restoring friction to safe values. This should lead to improvements in the operational performance and safety of rail transport for passengers and train operators.
SAGE
“A novel methodology for developing ultra-low adhesion leaf layers on a full-scale wheel/rail rig”
Jaffe J., White B., Lanigan J., Lewis R.
Proceedings of the Institution of Mechanical Engineers, Part F: Journal of Rail and Rapid Transit scimago Q2 wos Q3 , 
2023-12-06,  citations by CoLab: 2 ,  Abstract  
This paper explores a novel method for creating an ultra-low adhesion leaf layer on a rail using a full-scale wheel/rail rig. Ultra-low adhesion layers were generated using leaf powder for the first time on a linear full-scale rig. The layers are compared chemically and physically to other layers from the laboratory and field. Testing of the adhesion evolution of the leaf contaminated layers over 50 cycles is explored, and compared to dry and wet rails.
Elsevier
Quantifying the effect of particle characteristics on wheel/rail adhesion & damage through high pressure torsion testing
Skipper W.A., Nadimi S., Watson M., Chalisey A., Lewis R.
Tribology International scimago Q1 wos Q1 , 
2023-01-01,  citations by CoLab: 9 ,  Abstract  
Low adhesion in the wheel/rail contact is a problem for the rail industry in Great Britain as it causes significant scheduling and safety issues. Applying sand to the wheel/rail contact is used to mitigate against low adhesion however, there is not a consensus on what makes a “good” particle for restoring adhesion, especially with regards to when the particle has entered the wheel/rail contact. The aim of this work was to investigate what particle characteristics had the greatest effect on wheel/rail adhesion and surface conditions, using a process of particle characterisation, tribological testing and statistical modelling. Particle size, shape, and hardness were all found to affect tribological performance. This knowledge can help guide future changes to sanding operations.
SAGE
Effects of temperature and humidity on railhead friction levels
Folorunso M.O., Lewis R., Lanigan J.L.
Proceedings of the Institution of Mechanical Engineers, Part F: Journal of Rail and Rapid Transit scimago Q2 wos Q3 , 
2022-12-26,  citations by CoLab: 4 ,  Abstract  
This paper explores the research gap involving the links between railhead temperature, relative humidity, and coefficient of friction (adhesion level) at the wheel/rail interface as found on track across the UK. Existing work done in this field has mostly been carried out in laboratories which limits variation of environmental conditions. Weather and friction data were collected from different sites across England, generating a real representation of the railhead conditions. Correlations were established between the environmental dataset and the railhead friction to give a greater insight into the mechanisms of low adhesion and when low adhesion can be expected to take place. This can provide an avenue to better predict the occurrence of low adhesion in the wheel/rail interface, therefore improving safety within the rail network. Results from the data analysis showed that high humidity conditions, independent of the railhead temperature, reduces the adhesion level on the railhead. Showing that low adhesion can occur in warmer temperatures, such as those typically experienced in early autumn where there is high relative humidity.
Thomas Telford
Vehicle-based cryogenic rail cleaning: an alternative solution to ‘leaves on the line’
Krier P., White B.T., Ferriday P., Watson M., Buckley-Johnstone L., Lewis R., Lanigan J.L.
Proceedings of the Institution of Civil Engineers: Civil Engineering scimago Q4 wos Q4 Open Access , 
2021-07-16,  citations by CoLab: 4 ,  Abstract  
Contamination of rail lines with leaves and other organic matter and oxides can affect the traction of train wheels and cause safety issues, delays and schedule changes. The main solution in the UK is to use specialist rail-head-treatment trains that clean rails with high-pressure water jets. But these trains cannot cover all UK mainline infrastructure due to limited availability and gauging issues. As such, there is a need for a rapid-response mobile solution to expand this capability. This paper reports on successful field trials of a small road-to-rail vehicle fitted with dry-ice blasting equipment, and the effect this has on both cleaning rails and improving train braking.
SAGE
Field trials of a methodology for locomotive brake testing to assess friction enhancement in the wheel/rail interface using a representative leaf layer
Lanigan J.L., Krier P., Johnstone L.B., White B., Ferriday P., Lewis R.
Proceedings of the Institution of Mechanical Engineers, Part F: Journal of Rail and Rapid Transit scimago Q2 wos Q3 , 
2020-11-16,  citations by CoLab: 9 ,  Abstract  
There are two options for testing the performance of rail vehicles and the application of material to the wheel/rail interface to influence friction, and therefore braking performance, in a low adhesion environment: laboratory work which is not representative of conditions in the field, and expensive track tests using fully instrumented modern vehicles largely using low adhesion simulants that are not representative of those that occur in the real world and usually applied over great lengths of track. This paper presents a third option: low-cost track tests. We determined the minimum of equipment and resources needed to produce low adhesion using a method more representative on Autumn conditions on rail and monitor the performance of rail vehicles when braking on it. This was mainly targeted at use for testing products applied to the wheel/rail interface to enhance traction, hence the need for real low adhesion causes. We present the methodology that we have developed, and some initial results showing that using it we can generate a low adhesion scenario when braking from 10 mph. This can be used to develop mitigation solutions for low adhesion in a more cost effective manner.
The Royal Society
The composition and friction-reducing properties of leaf layers
Watson M., White B., Lanigan J., Slatter T., Lewis R.
Proceedings of the Royal Society A: Mathematical, Physical and Engineering Sciences scimago Q1 wos Q1 Open Access , 
2020-07-29,  citations by CoLab: 7 ,  Abstract  
Every autumn rail networks across the world suffer delays, accidents and schedule changes due to low friction problems caused by leaves landing on the rails. These leaves form a layer that can reduce the friction between the wheel and the rail to a similar level as that between ice and an ice-skate ( μ = 0.01 – 0.05 ). Previous works have generated several hypotheses for the chemical reactions and low friction mechanism associated with these layers. In this work, the reaction between an aqueous extract of sycamore leaves and metallic iron is investigated. This reaction has been shown to produce a black precipitate, which matches field observations of leaf layers, while friction tests with these extracts produce characteristic ultra low friction. The reaction is investigated through FTIR, XPS, CHNS and ICP-MS analysis as well as wet chemical testing. The impact of the reaction on friction is investigated through three rounds of tribological testing. The results indicate that the black precipitate produced is iron tannate, formed by complexation of tannins with dissolved iron ions. Friction testing showed that eliminating tannins from the leaf extract resulted in a significant increase in the friction coefficient compared with the control.
Elsevier
Wheel slip/Slide and low adhesion caused by fallen leaves
Chen H., Furuya T., Fukagai S., Saga S., Ikoma J., Kimura K., Suzumura J.
Wear scimago Q1 wos Q2 , 
2020-04-01,  citations by CoLab: 20 ,  Abstract  
On the sloping section of a train service line located in mountainous areas, idling and skidding of the wheels caused by leaves that fall on the railhead in autumn often occurs, and this hinders the scheduled operation of the train. Although countermeasures such as spraying sand or ceramic particles onto the contact zone of wheel/rail are adopted, the effect is insufficient in late autumn. For clarifying the mechanism of the decrease in the adhesion between the wheel and the rail based on fallen leaves and acquiring information useful for practical implementation of countermeasures, the authors conducted a vehicle running test with driving and braking operations on a test line to investigate the occurrence of wheel slipping/sliding under various railhead states such as dry/wet leaves and dry/wet black accretion films, as well as the adhesion coefficient between the wheel and the rail when dry/wet black accretion films exist on the railhead. The results clarified that the wheel slipping/sliding was likely to occur under wet conditions, in particular frequently occur while wet black accretion films exist on the railhead, and then a low adhesion coefficient was recognized under the same conditions. Regarding the black accretion film formation process, the authors reproduced by a rail cooling device which can simulate atmospheric temperature in mountain area, and clarified that the tannin contained in the crushed fallen leaves has a reaction with steel comment of rail under wet (condensation, frost, light rain etc.) conditions and then black tannin iron was generated and adhere to the railhead. The countermeasure of wheel slip/slide should be focused on how to prevent the formation of the black accretion films or remove the black accretion films in the future work.
Royal Society of Chemistry (RSC)
Chemistry of black leaf films synthesised using rail steels and their influence on the low friction mechanism
Ishizaka K., Lewis S.R., Hammond D., Lewis R.
RSC Advances scimago Q1 wos Q2 Open Access , 
2018-09-19,  citations by CoLab: 18 ,  PDF,  Abstract  
Fallen leaves are the main issues for train operations in the autumn season due to their low friction coefficient (COF), leading to signals being passed dangerously and amended timetables. The main aim of this study was to elucidate the mechanism of low friction due to black leaf films, which are often seen on leaf-contaminated rails. A black material was successfully synthesised in the laboratory with water extracts from sycamore leaves and a plate of R260 rail steel. The black powder made from the extracts of brown leaves (BBP) was identified as the key material of low friction by the pin-on-flat tribological test, giving a COF between 0.08 and 0.14, which was lower than the COF of commercial engine oil (approximately 0.14). X-Ray fluorescence showed that the black material was a mixture of iron and leaf-organics. Laser Raman spectroscopy revealed that graphite-like carbon was likely to be formed on iron oxides. Fourier transform infrared spectroscopy showed that the formation of iron carboxylate was likely in bulk, which possibly transformed into iron oxides on the surface. Moreover, X-ray photoelectron spectroscopy detected a relatively high concentration of phosphates only in BBP. Hence, the low friction is presumably due to graphitic carbon, iron oxides and phosphate compounds in the black leaf films, as well as mechanical separation effects of bulk leaves. This black material could be a product of the Maillard reaction or reaction between iron and organic acids, such as tannic acids.
Elsevier
Material concepts for top of rail friction management – Classification, characterisation and application
Stock R., Stanlake L., Hardwick C., Yu M., Eadie D., Lewis R.
Wear scimago Q1 wos Q2 , 
2016-11-01,  citations by CoLab: 52 ,  Abstract  
The concept of managing and adjustment of friction between the wheel and rail has a long history within the operation of railways systems. In the past, adjustment/management has been limited to gauge face lubrication and the use of sanding equipment. The introduction of the top of rail (TOR) friction modifier (FM) over the last 20 years now allows for the modification of the friction at the top of rail–wheel tread interface. This paper focusses on the concept of TOR friction adjustment. Recent developments have led to a new generation of products, defined here as, TOR lubricants (oil and/or grease-based) and hybrid materials (oil/water mixtures), which are non-drying or slow drying. Definitions and functional difference are detailed and contrasted with that of the water-based drying FM. The water-based TOR-FM once applied rapidly dries, mixes with the existing third-body layer, and allows for the accommodation of shear displacement. TOR lubricants and hybrid materials rely on mixed boundary layer lubrication, contrary to application of the water-based TOR-FM. It has been shown that the adhesion level is highly influenced by the lubricant application rates. The risks and benefits (lateral force reduction, corrugation mitigation, and impact on energy consumption and influence on rolling contact fatigue) are discussed for all product classifications. However, a lack of data exists for the TOR lubricants especially in the area of rolling contact fatigue where laboratory studies have identified the possibility of crack interaction. Whilst it can be seen that TOR lubricants have the ability to provide similar benefits to that of a water-based FM, they exhibit a strong dependency on the application rate which may lend itself to adhesion and RCF issues. Further work is recommended in this area.
Elsevier
A new method for the assessment of traction enhancers and the generation of organic layers in a twin-disc machine
Lewis S.R., Lewis R., Cotter J., Lu X., Eadie D.T.
Wear scimago Q1 wos Q2 , 
2016-11-01,  citations by CoLab: 21 ,  Abstract  
Low adhesion presents a major concern for many rail operators. Railway vehicles under these circumstances can experience a serious loss of braking capability giving rise to dangerous situations such as platform overruns and signals passed at danger. One cause of adhesion loss is autumn leaf fall, Fulford C.R. (2004) [1] . Leaves are run over by the wheels of a train and a chemical reaction occurs between the leaf and the rail steel, Cann P.M. (2006) [2] . This forms a black layer on the rail which when wet causes very low friction. These leaf layers have also been shown to be isolating and can interfere with railway signalling systems. Traction enhancers (also referred to in this paper as traction gels) have been developed as a new technique in combating the problems caused by leaf contamination. They consist of sand particles suspended in a water based gel and are designed to be delivered to the rail by the trackside or via mobile application systems. The aim of this work was to develop a technique for generating a representative leaf layer on the surface of a twin-disc rail specimen and using this to develop a test methodology for assessing the performance of a traction gel in terms of adhesion recovery, wear and its effect on wheel/rail isolation. A new repeatable method for generating a low traction leaf layer on the rail disc was developed. The traction gel tested was proven to quickly restore adhesion back to close to dry levels. The wear rate of the rail disc with the traction gel was lower than for a dry/uncontaminated contact. Isolation of the leaf layers and traction enhancer were measured using a representation of aTI21 track circuit. This method can be used in the selection and benchmarking of other traction enhancing products before they are trialed in the field.
Elsevier
Wear between wheel and rail: A pin-on-disc study of environmental conditions and iron oxides
Lyu Y., Zhu Y., Olofsson U.
Wear scimago Q1 wos Q2 , 
2015-04-01,  citations by CoLab: 75 ,  Abstract  
Railways operate in an open environment where temperature, humidity, and the oxidation conditions are subjected to change. An experimental investigation used a pin-on-disc machine to examine the influence of environmental conditions and iron oxides on the wear performance of the wheel–rail contact. The wear mechanisms were analyzed using scanning electron microscopy and found to be highly dependent on the environmental conditions. On clean contacts, adhesive wear is predominant under low-moisture conditions, becoming more serious with decreasing temperature. With high moisture and at room temperature (i.e., 20 °C and 10 °C) oxide flakes would self-produce and protect the pins from severe wear, as oxidative wear is the main wear mechanism. Samples experienced a transformation of the wear mechanism from adhesive to oxidative with increasing humidity on clean contacts. Complex three-body wear in abrasion form has been determined to dominate oxidized contacts. Under dry conditions, pins underwent severe wear appearing as delamination at 20 °C and crushed wear debris at 3 °C. Raising the moisture level helps the pins to avoid severe wear. • Effect of environment and iron oxides on wear between wheel and rail was studied. • Clean tests at all temperatures and low relative humidity underwent adhesive wear. • With increasing humidity, wear mechanism changed from adhesive to oxidative. • Self-produced oxides showed a protection effect. • Oxidized tests acted abrasive wear and become severe with decreasing temperature.
Elsevier
Third body layer—experimental results and a model describing its influence on the traction coefficient
Meierhofer A., Hardwick C., Lewis R., Six K., Dietmaier P.
Wear scimago Q1 wos Q2 , 
2014-06-01,  citations by CoLab: 48 ,  Abstract  
When adding substances to the wheel–rail contact, they mix with wear particles and form a Third Body Layer (3BL). This layer influences the initial gradient of the traction characteristic. During twin-disc tests presented in this paper, a granular layer consisting of iron and iron oxides with a thickness of up to 50 μ m was found. In addition, a creepforce model is presented that uses non-linear properties of the 3BL to describe its influence on the traction characteristic. The results of the model were compared to the results of the experiment. A qualitative and quantitative agreement was achieved. This will improve, e.g., the quality of vehicle dynamics simulations, optimizations of control devices for traction and braking, and predictions of wear and damage on wheel and rail.
Laboratory simulation of low-adhesion leaf film on rail steel
Vasic G., Franklin F.J., Kapoor A., Lucanin V.
International Journal of Surface Science and Engineering scimago Q3 wos Q4 , 
2008-06-27,  citations by CoLab: 14 , 
Tribology of the Wheel – Rail Contact
Olofsson U., Lewis R.
2006-05-22,  citations by CoLab: 17 , 

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