Top Of Rail Research Articles

Assessing the Performance of TOR Lubricants in Humid Environments and Under Dew Conditions

Top-of-rail (TOR) lubricants are commonly used for friction control in railway operations. They aim to lower friction and reduce noise and wear while ensuring sufficient transmission of traction/braking forces. However, the wheel–rail interface is an open system, so the conditions may suddenly change due to the weather, and different contaminants may enter the contact and influence the performance of these lubricants. Thus, this study examined the effect of humidity and dew on two commercial products, as these conditions often occur on the track. A methodology based on a creep curves measurement approach was used to assess product performance under various scenarios. All measurements were conducted on a universal tribometer in the ball-on-disc configuration covered with a climate chamber. The results show a strong influence of dew on the tested products, as dew lowered their performance parameters and caused low adhesion problems. Possible mechanisms of water–oil interaction and formation of oxidic third body layers were discussed. The main findings indicate that TOR lubricants may cause traction/braking problems if used in dew conditions. The present study may be helpful in optimising friction management methods in the future.Graphical

Investigation into Discrepancies in Alignment and Levelling of Precast Segmental Box Girders (SBGs) During Launching for LRT 3, from Bandar Utama to Johan Setia (Package GS10)

In recent decades, there has been a notable global increase in the utilization of precast concrete segmental bridges within construction projects. However, discrepancies have been observed in the height of precast Segmental Box Girders (SBGs) installed alongside PS1 (monolithic), deviating from project specifications. This discrepancy impacts the deck level and consequently influences the Top of Rail (TOR). Consequently, a study was undertaken at AlKauthar Kinematics Sdn Bhd, a company involved in the LRT3 project's construction, with a specific focus on the casting and installation of Segmental Box Girders. The study's objectives include identifying the factors contributing to precast SBG misalignment during the LRT3 project's launch at P25-08, analyzing data for realignment purposes, and proposing design methodologies for manufacturing SBGs. The methodology employed in this study entails the analysis of data sourced from the industry, utilizing As-Built Surveys conducted by surveyors. Findings indicate that precast SBG misalignment during launching at P25-08 is primarily attributed to on-site errors, particularly casting errors during the construction of the cast-in-situ monolithic segment P25-08. This insight is invaluable for both governmental bodies and private construction organizations in mitigating project setbacks.

A benchmarking methodology for top-of-rail products: Carry distance and retentivity

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.

Tribological and rheological performance of friction modifiers with different viscosities

Friction modifier (FM) in the rail/wheel applications is a special lubrication material that could be applied between the top of rail and the tread of wheel. The application of FM brings many benefits to the wheel-rail interface such as reducing noise, alleviating wheel-rail wear and mitigating corrugation. Viscosity is an important parameter to reflect fluid properties of FM materials. In this study, FM samples with different viscosities were prepared by changing the content of sodium carboxymethyl cellulose (CMC). The tribological and rheological performance of these FM samples were explored using the twin-disc testing machine and rotational rheometer. Furthermore, the relationship between the tribological and rheological results were tried to establish. The results showed that the increase in the content of CMC could increase the viscosity of FM and enhance the solid-like characteristic of FM, which could help FM reduce coefficient of adhesion (COA) level and wheel-rail damage. For the FM material developed in this study, the rational applying amount and the range of viscosity were about 15 μL/time and 200 Pa s to 400 Pa s, respectively, considering the factors of wheel-rail adhesion, wear, potential waste and pumping process in the practical application.

A benchmarking methodology for top-of-rail products

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.

Complete modified notch functions for a welded detail of a trough bridge

AbstractAmong the most frequent tasks occurring in railway bridge construction, there is the replacement of old structures of length up to 25 m. To reduce the own weight, old bridges are usually erected without a ballast bed. On the contrary, today railway bridges are provided with a ballast bed with a standard depth of 55 cm. As in most cases neither the top of rail can be raised nor the bottom line of the structure can be lowered, the depth of the construction itself must be kept as low as possible. An appropriate (though special‐purpose and expensive) solution is given by a trough bridge with 120 mm‐deep heavy a steel plate as road deck. This plate is connected by fillet and single‐level broad welds to the web plates. The present article deals with the fatigue verification of these welded details based on a modified formulation of notch stresses.

Towards a Standard Approach for the Twin Disc Testing of Top-Of Rail Friction Management Products

A wheel/rail friction coefficient that is too low can result in damage to the wheel and rail due to slips and slides, delays and safety concerns. A friction coefficient that is too high can result in excessive wear, noise and rolling contact fatigue. Changing contact and environmental conditions cause variations in wheel/rail friction, so friction management products, applied via wayside or on-board applicators, are used to either increase or decrease the friction coefficient so that an improved level is reached. They can be split into three classes; traction enhancers, lubricants and top-of-rail products (including water-based, oil/grease-based and hybrid products). This paper focuses on top-of-rail products and describes the different apparatus, contact conditions, product application methods and result interpretation that have been used to test these products and highlights the requirement for a more standardised test method. A proposed test method is outlined, which uses a twin disc test rig to collect “effective level of friction” and “retentivity” data to assess product effectiveness. More comparable and standardised data will ensure that maximum benefit is obtained from each set of results and help both product development and the approvals process.

Influence of change in frictional condition of track rail surfaces on interaction forces in the “wheel/rail” contact

Determination of frictional condition of the running surface and side surface of the top of rail (lubrication) that ensures the best interaction of the rolling stock wheels and the rail, reduces the force action and thus ensures the track stability and reduced side wear of rails in the curved tracks is relevant for all the rail net.The objective of research is to determine the influence of frictional condition of the track rail surfaces on the interaction forces in the “wheel/rail” contact with various motion parameters (speed, radius).The theoretical and experimental methods were used in the research. The theoretical methods include multioptional computer modelling of axial and lateral forces that appear in the curved tracks during the freight train movement in the software package “Universal Mechanism”. The modelling results were processed with the use of correlation and regression analysis. The experimental methods include full-scale measurements in the existing track and results processing.According to the research results, the theoretical algorithms for assessment of influence of the running surface lubrication on the forces. The option of frictional condition of the wheel and rail interaction surfaces has been established to ensure reduction in the operating expenses for surfacing and rail replacement, energy costs for haulage of freight train.

Impact of Different Nose Lengths on Flow-Field Structure around a High-Speed Train

In this study, the time-averaged and instantaneous slipstream velocity, time-averaged pressure, wake flows, and aerodynamic force of a high-speed train (HST) with different nose lengths are compared and analyzed using an improved delayed detached-eddy simulation (IDDES) method. Four train models were selected, with nose lengths of 4, 7, 9, and 12 m. To verify the accuracy of the numerical simulation results, they were compared with wind tunnel test results. The comparison results show that the selection of the numerical simulation method is reasonable. The research results show that with increasing nose length, the peak values of the time-averaged slipstream velocity of the trackside position (3 m from the center of track and 0.2 m from the top of rail) and the platform position (3 m from the center of track and 0.2 m from the top of rail) decrease continuously, and show a trend of rapid reduction at first, and then a slow decrease. As the nose length increased from 4 to 12 m, the time-averaged slipstream velocity at the trackside position and platform position are decreased by 57% and 19.5%, respectively. At a height of 1.6 m from the top of the rail, ΔCP max (maximum pressure coefficient), |ΔCP min| (the absolute value of minimum pressure coefficient), and ΔCP (pressure change coefficient) decrease with increasing nose length, which is similar to the peak value of time-averaged slipstream velocity, decreasing rapidly at first and then slowly. As the nose length increased from 4 to 12 m, decreases of ΔCP max, |ΔCP min|, and ΔCP by 26.5%, 58.5%, and 44.8% were shown, respectively. Different nose lengths also have a significant impact on wake flow.

Aerodynamics of high-speed maglev trains passing each other in open air

With increasing train speed, aerodynamic effects pose a safety risk for train operations, especially for trains passing each other, the strong transient aerodynamic loads could result in window breakage, sideward shaking, trackside worker injuries, and facility fatigue damage. Unsteady compressible numerical simulation is carried out in this paper to investigate the transient flow field induced by two maglev trains passing each other at a speed of 430 km/h in open air. Good agreement is obtained between the numerical method and full-scale experiment results, with differences smaller than 6%. The transient pressure change on train surfaces and the slipstream distributions on trackside are analysed. It was noted that the peak values of pressure coefficient for two trains passing each other are approximately twice as larger as that of a single train passing because of the blocking effect and interference by the motion of the other train in the opposite direction. The maximum slipstream velocity occurs at a height of 1.4 m from the top of rail (TOR) at the meeting position, and the relationship between the slipstream velocity and the distance from the centre of rail (COR) is obtained, based on which, the safe distance is calculated.

Comparative numerical analysis of the slipstream caused by single and double unit trains

The use of double-unit trains is becoming a common means of increasing passenger capacity for a rail network. However, their expanded usage may create additional aerodynamic challenges. The present work obtains the characteristics of the slipstream caused by single and double unit trains using the detached eddy simulation (DES) method for 1/20th scaled models. The numerical results are verified by full-scale experiments. The slipstream velocities and pressures obtained by the two train models at different distances from the center of track (COT) and the top of rail (TOR) are compared. The coupling structure of the double-unit train model is found to produce a velocity peak that is much greater than that of the single-unit train model in the same position. At the area away from the COT and close to the TOR, the velocity of the far wake region is larger for the double-unit train model. The coupling structure also leads to a positive pressure change in the coupling region, and its value is comparable to or even much greater than that caused by the nose. It is considerable that the subsequent pressure criteria could take the positive pressure on the coupling region into account for the double-unit train.

Analysis of Passenger Incident Data from Five Rail Transit Systems

The study results reported here are part of a larger research project that developed a manual for practitioners to improve safety at rail transit platform/train and platform/guideway interfaces. As part of that effort, passenger injury incident data was collected from five rail transit systems, and interviews were conducted with safety officers at other rail transit systems in the US and Canada. The data collected showed that stairs and escalators and general platform tripping produced more injury incidents than the platform/train and platform/guideway interfaces. Heavy rail transit with platforms that are higher than 24 inches from top of rail had more injury incidents than light rail transit that typically operates on low level platforms. Other causes of injury incidents included intoxication, attempted suicide, and distraction.

DEVELOPMENT OF THE MUNICIPAL NOISE-ABSORBING SCREEN AND TEST SECTION CONSTRUCTION TECHNOLOGY

The article presents the development and construction technology of the Municipal noise-absorbing screen (MNAS) – in Czech "Mestská protihluková clona" (MPHC). The Municipal noise-absorbing screen is a new acoustical element developed in cooperation of the Department of Railway Structures, Faculty of Civil Engineering, CTU in Prague and the Montstav CZ s.r.o. Company. It is characterised by very small dimensions – its height is only ca 0.3 metre above the top of rail. The element serves to attenuate the noise induced by rail traffic arising at the wheel-rail contact. The Municipal noise-absorbing screen consists of individual, mutually interlocked units, placed one after another, made of bound recycled rubber. The article describes the major limiting conditions for the placement, shape and execution of the Municipal noise-absorbing screen. It also describes the construction of the test section situated on a tram track in Prague and sums up the experience obtained after the first year of operation.

The effects of friction management materials on rail with pre existing rcf surface damage

Management of rolling contact fatigue (RCF) risk is a critical maintenance activity in railway operations. Practical means of RCF mitigation involve: 1) preventative and corrective grinding to remove RCF cracks; 2) management of wheel and rail profiles to minimize peak contact pressures; and 3) selection of appropriate rail metallurgy. In addition, reduction of traction forces by application of dry film Top of Rail friction modifiers (FM) has recently been shown to reduce crack growth and extend grinding intervals.Hydro-pressurisation and crack face lubrication are processes by which liquid materials (e.g., water), enter pre-existing RCF cracks and under wheel/rail contact pressure and cause accelerated crack growth, leading to spalling and shelling on rail and wheels. Thus, any liquid material added deliberately to the wheel/rail interface should be considered carefully in terms of the potential for aggravating RCF damage. This study compares the impact on hydro-pressurization and crack face lubrication of different types of materials designed for application to the top of rail using twin disc testing. One type of FM material is water-based, drying providing solid particles to the rail-wheel contact. Two other types are oil or oil-plus-water-based (hybrid material) that do not naturally dry and have been introduced more recently to the market. In addition, a commonly used gauge face lubricant (grease) was evaluated.

Effects of curve radius and rail profile on energy saving in heavy haul achieved by application of top of rail friction modifier

Energy saving achieved by application of top of rail (TOR) friction modifier (FM) in heavy haul are modeled, and the effects of curve radius and rail profile on the energy saving are discussed. A vehicle model for a C70 freight car running on the track of a heavy haul line was established. The coefficient of friction and Kalker coefficient were adjusted to simulate the creepage/force relationship when the TOR FM is applied to the wheel/rail interface. Friction work is used to represent the energy dissipation due to wheel/rail creepage. Energy saving achieved by applying TOR FM was calculated. The energy saving was studied under different operating conditions, and the effects of track curve radius and rail profile were studied. It is found that the curve radius of the track has significant influence on the energy saving. The energy saving was also found to behave differently on new and worn rails. The dramatic increase of lateral creepage on new rail when FM is applied and the decrease of the difference of wheel rolling radius when the rail profile changes from new to worn were found to be the main reasons that cause the difference.

Material concepts for top of rail friction management – Classification, characterisation and application

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.

Implementation of a wheel–rail temperature model for locomotive traction studies

ABSTRACTCalculation of the temperature in the contact zone at the wheel–rail interface is a very complex and important issue for multidisciplinary railway studies. The knowledge of temperature in the contact interface between two bodies, and with the possible presence of a third body interfacial layer, allows making informed judgments on processes in areas such as lubricant choice, wear estimation, life cycle prediction, etc. This paper focuses on development of a temperature modelling methodology in Gensys, and also presents its implementation for the study of temperatures at different contact points (top of rail, gauge corner, and gauge face contacts). In operational practice, all these mentioned contacts have different coefficients of friction which should be characterized as velocity and slip-dependent variables. To demonstrate the workability of the developed methodology, numerical experiments for a heavy haul locomotive equipped with a simplified bogie traction control system have been performed on curved track, where a locomotive has been operated under maximum traction forces and with longitudinal and lateral coupler forces attached in order to take into account train dynamics. Both new and worn rail profiles have been used. Limitations of the proposed methodology as well as proposed future work and further improvements are discussed.

Measurements of friction coefficients between rails lubricated with a friction modifier and the wheels of an IORE locomotive during real working conditions

The real friction coefficients between the rails and the wheels on a 360t and 10,800kW IORE locomotive were measured using the locomotive׳s in-built traction force measurement system. The locomotive consisted of two pair-connected locomotives had a CoCo+CoCo bogie configuration, and hauled a fully loaded set of 68 ore wagons (120t/wagon). The measurements were performed both on rails in a dry condition and on rails lubricated with a water-based top-of-rail (ToR) friction modifier on the Iron Ore Line between the cities of Kiruna and Narvik in Northern Sweden and Norway, respectively. Since full-scale measurements like these are costly, the friction coefficients were also measured at the same time and place using a conventional hand-operated tribometer, with and without the ToR friction modifier. The most important results are that the real friction coefficient is definitely not constant and is surprisingly low (0.10–0.25) when the ToR friction modifier is used, and that it is also significantly dependent on the amount of ToR friction modifier. A large amount will reduce the friction coefficient. Furthermore, it is concluded that the real friction coefficients are in general lower than the friction coefficients measured with the hand-operated tribometer. A final remark is thus that the use of a water-based ToR friction modifier can give excessively low friction, which can result in unacceptably long braking distances.

Research methodology for evaluation of top-of-rail friction management in Australian heavy haul networks

Managing the coefficient of friction at the wheel/rail interface through wheel flange/gauge face lubrication is an accepted practice in railway systems. However, the coefficient of friction between the top of rail and wheel tread is not well addressed using this method, with traction, braking and some steering forces causing significant rail and wheel damage. Top-of- rail friction management uses friction modifiers to control the coefficient of friction within a defined range, and is being used in some North American rail networks with beneficial results. In Australia, there has been limited use of top-of-rail lubrication and where it is applied, it is mainly utilised to improve steering forces and mitigate wheel squeal. This research project sought a holistic understanding of top-of-rail lubrication and management of wheel/rail friction in the Australian context. A systematic approach for experimentation and analysis of the application of a friction modifier was developed in this study. The approach utilised an engineering analysis based on experimental results and publications and a numerical study for three-dimensional analysis. Vehicle system dynamics and wheel/rail operating conditions were then modelled through GENSYS simulation to understand variations in wear index with respect to friction conditions at the wheel/rail interface.

Numerical calculation of the slipstream generated by a CRH2 high-speed train

Slipstreams caused by high-speed train movement through the atmosphere pose a safety risk to passengers, trackside workers and track infrastructure. The improved delayed detached eddy simulation (IDDES) approach, an improved version of the detached eddy simulation method, is adopted in this paper to calculate the slipstream of a four-coach 1/25th-scale model of the CRH2 high-speed train. Slipstream velocities and pressures at various lateral distances from the centre of rail (COR) position and vertical distances from the top of rail (TOR) position at trackside are calculated. Numerical results are compared with measurements obtained in a full-scale test and good agreement is obtained, which verifies the effectiveness and potential of the less costly IDDES method. It is found that the velocity and pressure distributions are similar to those obtained using different train types but with different peak values related to the difference in shapes. The peak velocities in the slipstream along the length of the train are found at the tail and in the near wake region. The magnitude of the peak decreases with an increasing distance from the COR and shows a relatively high value at about two thirds of the train height from the TOR. The maximum pressure coefficients are found in the upstream and nose regions. The results show that the value of these coefficients decreases with an increasing distance from the COR and TOR. Based on the suggested safe slipstream velocity in China, the IDDES results show that for a CRH2 high-speed train at a speed of 350 km/h, the safe standing distance should be greater than 3.4 m in the lower part of the train’s slipstream (up to about half of the train height from the ground) and 2.4 m for the top part of the train’s slipstream (above half the height of the train from the ground).