Abstract: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 reach… Show more
“…• Top-of-rail (TOR) products: maintain the wheel tread/rail head interface at an intermediate friction level • Traction enhancers: raise friction where low adhesion is occurring • Lubricants: reduce friction wear in the wheel flange/ rail gauge face contact Figure 1 shows defined friction regimes for the wheel/rail interface as well as how friction management products are expected to change friction levels. 2 Managing and controlling TOR friction helps in tackling issues such as noise, 3,4 damage development 5 and energy consumption. 6,7 A range of TOR products have been designed to achieve this, which are often characterised by their "drying behaviour" 8 :…”
Section: Introductionmentioning
confidence: 99%
“…Figure 1 shows defined friction regimes for the wheel/rail interface as well as how friction management products are expected to change friction levels. 2 Managing and controlling TOR friction helps in tackling issues such as noise, 3,4 damage development 5 and energy consumption. 6,7 A range of TOR products have been designed to achieve this, which are often characterised by their “drying behaviour” 8 :• TOR friction modifiers (TOR-FMs): water-based, drying products where the water evaporates leaving solid particles to mix with the third body layer present on both wheel and rail to control friction• TOR lubricants: non-drying products based on an oil or grease• TOR hybrids: slow-drying mix of water and oil-based productsFigure 1.Wheel/rail interface regimes and impact of friction management products.…”
Section: Introductionmentioning
confidence: 99%
“…6,7 A range of TOR products have been designed to achieve this, which are often characterised by their “drying behaviour” 8 :• TOR friction modifiers (TOR-FMs): water-based, drying products where the water evaporates leaving solid particles to mix with the third body layer present on both wheel and rail to control friction• TOR lubricants: non-drying products based on an oil or grease• TOR hybrids: slow-drying mix of water and oil-based productsFigure 1.Wheel/rail interface regimes and impact of friction management products. 2 …”
The railway industry uses top-of-rail products to control and manage the friction in the wheel/rail interface to help ensure efficient train operations and reduce wheel and rail damage. A product is typically applied from a wayside applicator that pumps a puddle onto the rail head where a passing wheel will pick it up and then transfer it down the track. The aim of this study was to study the transfer mechanisms of water-based top-of-rail friction modifiers (TOR-FMs) and how they are linked to the friction conditions in the wheel/rail interface. The transfer mechanisms were split into three parts: pick-up, carry-on and consumption. Pick-up looks at how the product transfers from the puddle on the rail to a wheel tread, whereas the carry-on mechanism relates to the product transfer back to the wheel. Consumption focuses on the removal rate of the product layer from the wheel or rail. A full-scale rig and twin disc machine were chosen to perform the tests because each rig could give different insights into understanding the product transfer mechanisms. Two products were tested of similar formulation. Results show that there are differences in the transfer and friction between the two products despite them being relatively similar. The test methods developed can clearly resolve differences between varying product types, which could be useful for product development studies or approvals work. The outcomes could also be used to develop a model of transfer/consumption.
“…• Top-of-rail (TOR) products: maintain the wheel tread/rail head interface at an intermediate friction level • Traction enhancers: raise friction where low adhesion is occurring • Lubricants: reduce friction wear in the wheel flange/ rail gauge face contact Figure 1 shows defined friction regimes for the wheel/rail interface as well as how friction management products are expected to change friction levels. 2 Managing and controlling TOR friction helps in tackling issues such as noise, 3,4 damage development 5 and energy consumption. 6,7 A range of TOR products have been designed to achieve this, which are often characterised by their "drying behaviour" 8 :…”
Section: Introductionmentioning
confidence: 99%
“…Figure 1 shows defined friction regimes for the wheel/rail interface as well as how friction management products are expected to change friction levels. 2 Managing and controlling TOR friction helps in tackling issues such as noise, 3,4 damage development 5 and energy consumption. 6,7 A range of TOR products have been designed to achieve this, which are often characterised by their “drying behaviour” 8 :• TOR friction modifiers (TOR-FMs): water-based, drying products where the water evaporates leaving solid particles to mix with the third body layer present on both wheel and rail to control friction• TOR lubricants: non-drying products based on an oil or grease• TOR hybrids: slow-drying mix of water and oil-based productsFigure 1.Wheel/rail interface regimes and impact of friction management products.…”
Section: Introductionmentioning
confidence: 99%
“…6,7 A range of TOR products have been designed to achieve this, which are often characterised by their “drying behaviour” 8 :• TOR friction modifiers (TOR-FMs): water-based, drying products where the water evaporates leaving solid particles to mix with the third body layer present on both wheel and rail to control friction• TOR lubricants: non-drying products based on an oil or grease• TOR hybrids: slow-drying mix of water and oil-based productsFigure 1.Wheel/rail interface regimes and impact of friction management products. 2 …”
The railway industry uses top-of-rail products to control and manage the friction in the wheel/rail interface to help ensure efficient train operations and reduce wheel and rail damage. A product is typically applied from a wayside applicator that pumps a puddle onto the rail head where a passing wheel will pick it up and then transfer it down the track. The aim of this study was to study the transfer mechanisms of water-based top-of-rail friction modifiers (TOR-FMs) and how they are linked to the friction conditions in the wheel/rail interface. The transfer mechanisms were split into three parts: pick-up, carry-on and consumption. Pick-up looks at how the product transfers from the puddle on the rail to a wheel tread, whereas the carry-on mechanism relates to the product transfer back to the wheel. Consumption focuses on the removal rate of the product layer from the wheel or rail. A full-scale rig and twin disc machine were chosen to perform the tests because each rig could give different insights into understanding the product transfer mechanisms. Two products were tested of similar formulation. Results show that there are differences in the transfer and friction between the two products despite them being relatively similar. The test methods developed can clearly resolve differences between varying product types, which could be useful for product development studies or approvals work. The outcomes could also be used to develop a model of transfer/consumption.
“…The results showed that the top-of-rail friction modifier could adjust the friction coefficient to near 0.2 and reduce the friction coefficient to 0.1 using lubricating oil. Ben White [24] proposed a test method to evaluate the effectiveness of top-of-rail friction management products using a twin-disc test rig to gather data on the "effective level of friction" and "retentivity". This method can provide valuable insights into the performance of such products.…”
The generation of wheel–rail-sliding frictional heat is often accompanied by transverse displacement of a wheel. To study the thermal problem of wheel–rail sliding friction at two-point contact, this paper uses an LM tread wheel and a 60 kg·m−1 rail as examples. A thermal–mechanical-coupled finite-element model of equal proportion wheel–rail sliding is established. A direct-coupling method is used to analyze the thermal–mechanical coupling of the wheel–rail interface under sliding contact. This model considers the temperature-dependent material properties and boundary conditions, such as thermal convection and thermal dissipation, in the process of nonstationary frictional-heat conduction. Firstly, the effects of different sliding speeds, axle loads, and contact modes on the temperature and stress fields of the contact area are analyzed. Then, the lubrication and cooling effects of friction modifiers on the rail top and rail gauge angle are compared. The results show that, at a sliding speed of 2 m/s and an axle load of 30 t under a sliding condition of 200 mm, on the top and side of the rail, the temperatures at the contact patch centers are 813 °C and 547.7 °C, respectively. Under different operating conditions, the rail-side temperature is 55–75% of that of the temperature at the rail top, and the rail-side contact and friction stress values are 76–96% of those at the rail top. This indicates that frictional thermal damage on the rail side cannot be ignored. With a lower sliding speed, the thermal response of the two contact patches is closer. The impact of axle load on the frictional temperature and stress on the rail side is more critical than the sliding speed. The optimal lubrication choice is overall lubrication, which can decrease the rail top temperature by 47.2% and frictional stress by 56.2%, as well as decreasing the rail side temperature by 70.3% and frictional stress by 77.4%.
“…The ultralow regime (0.05 and below) is where a train will definitely experience difficulties with braking and traction.Figure 1.CoF ranges (adapted from Ref. 2, by White et al 12 ).…”
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.
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