DOCTORAL T H E SIS Saad Ahmed Khan Saad Department of Civil, Environmental and Natural Resources Engineering Division of Operation, Maintenance and Acoustics ISSN 1402-1544 ISBN 978-91-7790-272-0 (print) ISBN 978-91-7790-273-7 (pdf) Effects of top-of-rail friction modifiers Effects of top-of-rail friction modifiers on the friction, wear and cracks of railway rails and cracks of railway Effects of top-of-rail friction wear modifiers on the friction, Luleå University of Technology 2019 on the friction, wear and cracks of railway rails Saad Ahmed Khan Operation and maintenance engineering Effects of top-of-rail friction modifiers on the friction, wear and cracks of railway rails Saad Ahmed Khan Division of Operation, Maintenance and Acoustics Department of Civil, Environmental and Natural Resources Engineering Luleå University of Technology Printed by Luleå University of Technology, Graphic Production 2019 ISSN 1402-1544 ISBN 978-91-7790-272-0 (print) ISBN 978-91-7790-273-7 (pdf) Luleå 2019 www.ltu.se ACKNOWLEDGEMENTS The research work presented in this thesis was carried out between March 2015 and February 2019 at the Division of Operation, Maintenance and Acoustics of Luleå University of Technology. I gratefully acknowledge Luleå Railway Research Center (JVTC) and the Swedish Transport Administration (Trafikverket) for financing the project. I would like to express my gratitude to my supervisor, Professor Jan Lundberg, and my co-supervisors, Dr Christer Stenström and Associate Professor Matti Rantatalo. I am thankful for the confidence that they have placed in my capability to conduct this research work, and for all their support through sharing their ideas, proposing improvements, proofreading manuscripts, finding new ways, and always adopting a positive approach. Many thanks are due to Ingemar Persson at AB DEsolver for assisting me by providing support for simulations and a large amount of useful information during my research. Special thanks are extended to my ex-colleague and my project leader at Trafikverket, Matthias Asplund, for all his support during this project. I am also grateful to Per Gustafsson at LKAB, who helped us to decide the location of the TOR equipment installation and provided information in the initial phase of the project. I would also like to express my thanks to Emil Viberg from Infranord, who arranged for a security person to accompany me every time I went to the railway track for measurements, as well as Stephan Scheriau from Voestalpine Schienen GmbH in Austria for providing rail steel material that was used for making wear probes. Furthermore, I would like to thank all my colleagues at the Division of Operation, Maintenance and Acoustics, especially my co-researcher Thomas Nordmark and laboratory technician Allan Holmgren. I would also like to thank all the PhD students and senior researchers at our division who helped me during the research work for my PhD. I am also grateful to all my friends in and outside the university who supported me during the work on this thesis, but who are too many to be mentioned by name. My deep gratitude is owed to my parents, Asma and Zaheer Ahmed Khan, and to my wife, Hiba, and my son, Daniyal, for all the support and confirmation received from them; without them, my goal would never have been achieved. Saad Ahmed Khan February 2019 Luleå, Sweden i ii ABSTRACT The railway is an economical and environmentally friendly mode of transport for long distances and heavy loads. The demands on the operators are increasing with increased competition in the market, and therefore they are currently demanding more track capacity. In the short term, the existing network is expected to deliver the increased capacity. In order to achieve increased capacity without introducing double track, either the axle load or the number of trains (i.e. the annual gross tonnage) needs to be increased, which will decrease the life of the rail and thus increase the maintenance cost. To increase the lifetime of the rails without compromising with regard to the axle load and speed, one must increase the strength of the rails, decrease the friction forces between the rails and wheels, or introduce a third body with anti-wear and anti-crack properties that can reduce the wear and rolling contact fatigue (RCF) without reducing the traction coefficient below the safety limit. The friction forces depend on several variables, for example third bodies in the wheel-rail interface, the train dynamics, the wheel and rail profiles, etc. Third bodies in the wheel-rail interface are one of the important influencing factors. The additive third bodies with anti-wear properties and friction reduction capabilities reduces both the wear and the RCF. However, a friction coefficient in the wheel tread and the top of the rail below 0.3 can cause slippage and a long braking distance. To reduce the degree of utilised friction to a value close to 0.35 from dry conditions with a value of 0.55, and thereby reduce the wear, a product known as top-of-rail friction modifier (TOR-FM) was developed in North America and presented in 2003 at the heavy haul conference. The TOR-FM manufacturers claim that their products provide a fixed range of friction coefficients (μ) and Kalker’s reduction factors in the wheel-rail interface. Kalker’s reduction factor considers the tendency of creepage between the rail and wheel as a function of the friction forces at lower creepage levels. Field and laboratory tests in the USA, Canada and China have determined the benefits of using friction control products, which include the reduction of RCF, wear, corrugation, bogie hunting, noise, and fuel consumption without any side effects. In contrast, researchers at Luleå University of Technology (LTU) have found that such products in certain conditions give unacceptably low friction that can cause long braking distances and slippage. Initial measurements, before the starting of the present research, performed using a wayside TOR-FM system on the Iron Ore Line (IOL – “Malmbanan” in Swedish) could not show any benefits of implementing such systems. Trafikverket is considering the implementation of the TOR-FM technology on the IOL. Directly implementing such technology can be inappropriate and expensive, because the reliability of a TOR- FM system has never been assessed for the conditions of the IOL. The IOL is the northernmost railway line in Sweden and is experiencing the problem of RCF, especially on its curves. This railway line is a single track and is mainly utilised by the ore freight trains operated by the Swedish mining company LKAB. The freight trains run by LKAB have an axle load of 30 tonnes, which is the heaviest in Europe. At present LKAB is planning to increase the axle load of their heavy haul trains to 32.5 tonnes, which will increase the RCF and wear issues. iii The present research investigated the effects of TOR-FMs using computer-based simulations, laboratory tests and field tests. The results from all the tests and simulations were used to calculate the life cycle cost of wayside and on-board systems. The simulation results have shown that by reducing the friction, the RCF can be reduced. This reduction in the RCF is greater on narrow curves than on larger curves as the friction force decrease with an increase in the curve radius. Curves with a radius larger than 1,000 m are not prone to RCF. The damage index method used in the simulation has also shown that on circular curves with a radius smaller than 300 m, the so-called “magic wear” rate can be achieved. Magic wear means that the wear rate due to normal operation is equal to the crack generation rate. The field results obtained using a handheld tribometer have shown that by using a TOR-FM, both the wear and the friction coefficients can be reduced. The content of the TOR-FM can have a significant effect on the carry distance and, generally, non-drying FMs have a longer carry distance. Excessive use of TOR-FM may only cause unacceptably low friction and a high operational cost and result in an insignificant increase in the carry distance. In addition, it was also concluded that in the case of the wayside system during extreme winters, the equipment could have maintenance issues and thus a high operational cost. The on-board system is an economical alternative to the wayside system, as it has lower operation and maintenance costs. The results have also shown that snow and ice formation in the winter act as a lubricant. However, further investigations are needed to provide knowledge of the efficiency of such natural lubricants and their retention on the rail. The present research has taken the IOL as a case study, but the results will be applicable all over the world. KEYWORDS: friction modifier, heavy haul, Iron Ore Line, Malmbanan, magic wear, railway, rolling contact fatigue (RCF), top-of-rail (TOR) lubrication, wear. iv SAMMANFATTNING Järnvägen är ett ekonomiskt och miljövänligt transportsätt för långa avstånd och tunga laster. Operatörernas krav ökar med ökad konkurrens på marknaden. Därför finns det för närvarande en efterfrågan på mer spårkapacitet. På kort sikt förväntas den befintliga järnvägen leverera den ökade kapaciteten. För att uppnå ökad kapacitet utan att införa dubbelspår måste axelbelastningen eller antalet tåg (årlig bruttoton) ökas, vilket minskar spårens livslängd och därmed ökar underhållskostnaderna. För att öka skenornas livslängd utan att behöva minska axelbelastningen och hastigheten måste man antingen öka slitstyrkan och spricktåligheten på skenorna eller minska friktionskrafterna mellan skenorna och hjulen eller införa så kallade “third bodies” med goda anti-sprick och slitageegenskaper. Friktionskrafterna är beroende av flera variabler, till exempel “third bodies” i hjul-järnvägsgränssnitt, tågdynamik, hjulprofil etc.