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Working Mechanism of Organic Friction Modifiers on Steel and Paper Materials

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Working Mechanism of Organic Friction Modifiers on Steel and Paper Materials Working Mechanism of Organic Friction Modifiers on Steel and Paper Materials Yasushi Onumata Submitted in accordance with the requirements for the degree of Doctor of Philosophy The University of Leeds School of Mechanical Engineering September 2016 The candidate confirms that the work submitted is his own and that appropriate credit has been given where reference has been made to the work of others. This copy has been supplied on the understanding that it is copyright material and that no quotation from the thesis may be published without proper acknowledgement. © 2016 The University of Leeds and Yasushi Onumata The right of Yasushi Onumata to be identified as Author of this work has been asserted by him in accordance with the Copyright, Designs and Patents Act 1988. Acknowledgement Firstly, I would like to express my sincere appreciation to my primary supervisor Professor Anne Neville for the continuous support of my PhD study. It must have been challenging to accept the oversea research student who is possible to stay at the University only for two and half years. Her kind guidance based on immense knowledge on the tribology field helped me all the time of research and writing of this thesis. Besides, I would like to thank my co-supervisor Dr Hongyuan John Zhao for his insightful comments and encouragement. His technical papers were the motivation for my decision to study in Leeds, and his deep knowledge and kind advice on the tribotest procedure or the analytical techniques kept supporting my research. My sincere thanks also for Professor Ardian Morina, Dr Chun Wang and all the group members for providing me the precious opportunities to discuss the research topics. The experience and the network connections established in Leeds must be the irreplaceable treasure for my lifetime. I thank my sponsor JX Nippon Oil and Energy Corporation for giving me the opportunity to study in the UK as a PhD student. Their financial support for the academic and the living expenses was essential to conduct the research. I’m coming back to work with them in Japan, and the experience and knowledge obtained in Leeds will be utilised for the lubricant in future. Finally, I would like to thank my family; my wife Maki and children. I know it was quite hard time for them to live in the different culture, especially for Maki looking after our two energetic boys. It is thanks to their spiritual and continuous support that I could finish writing up the thesis. i Abstract The effect of organic Friction Modifiers (FMs) on friction properties at steel and paper clutch materials is investigated, and their working mechanisms are assessed by the observation of reaction and adsorption films formed on the surface. FMs are essential additives for drivetrain lubricants to manage friction properties. Recently developed fuel efficient transmission systems such as Continuously Variable Transmission (CVT) require precise and complicated friction control. As a result it is extremely important for the detailed behaviour of the FMs and in particular their reactions with the surfaces to be elucidated. In this study, friction properties of organic friction modifiers, oleic acid, oleyl alcohol and glycerol mono-oleate, were evaluated by TE77 and MTM using steel and paper specimens, which simulate two major components of CVT; a steel belt-pulley mechanism and a paper clutch system. The surface films on the post-test materials were studied by SEM, EDX, XPS and ATR-FTIR to assess the influence of the FMs. The results indicate that the friction properties are strongly affected by the substrate material and test temperature as well as the chemical structure of the FMs. In addition, interactions between the FMs and the other additives play an important role for the friction modification mechanism. In order to discuss the working mechanism of the FMs, the relationship between the friction properties and the chemical nature of the surface films was considered. Furthermore, the chemical structure of the FMs and its formulation suitable for CVT fluids are discussed. ii Table of Contents Acknowledgement ........................................................................................................... i Abstract ........................................................................................................................... ii Table of Contents .......................................................................................................... iii List of Tables ................................................................................................................. ix List of Figures ................................................................................................................ xi List of Publications .................................................................................................... xviii Chapter 1 - Introduction ................................................................................................ 1 1.1. Background ............................................................................................................ 1 1.2. Objectives ............................................................................................................... 4 1.3. Research Contribution ............................................................................................ 4 1.4. Thesis Outline......................................................................................................... 5 Chapter 2 – Literature Review ...................................................................................... 7 2.1. Background ............................................................................................................ 7 2.1.1. History of Tribology ........................................................................................ 7 2.1.2. Friction ............................................................................................................. 7 2.1.3. Lubrication ....................................................................................................... 8 2.2. Lubrication Technology in Automotive Systems ................................................. 10 2.2.1. Lubrication in Engines ................................................................................... 11 2.2.2. Lubrication in Transmission Systems ............................................................ 12 2.2.3. Conventional Automatic Transmission (AT) ................................................ 15 2.2.4. Continuously Variable Transmission (CVT) ................................................. 18 2.3. Automatic Transmission Fluid (ATF) .................................................................. 19 2.3.1. Formulation Basis .......................................................................................... 19 iii 2.3.2. Base Oil.......................................................................................................... 20 2.3.3. Viscosity Modifier (VM) ............................................................................... 21 2.3.4. Zinc Dialkyl Dithiophosphate (ZDDP).......................................................... 21 2.3.5. Molybdenum Dithiocarbamate (MoDTC) ..................................................... 21 2.3.6. Organic Friction Modifier (FM) .................................................................... 22 2.3.7. Phosphorous Anti-wear Agent ....................................................................... 23 2.3.8. Metal Detergent ............................................................................................. 23 2.3.9. Dispersant ...................................................................................................... 24 2.3.10. Anti-oxidant ................................................................................................. 24 2.4. Literature Review on Working Mechanism of FMs ............................................ 25 2.4.1. Adsorption Film Formation ........................................................................... 25 2.4.2. Interaction with Other Additives ................................................................... 30 2.4.3. Application to ATF and CVTF ...................................................................... 32 2.5. Research Target .................................................................................................... 35 Chapter 3 -Experimental Procedures and Analysis of Starting Oils and Surfaces 37 3.1. Operating Conditions of the CVT Components ................................................... 37 3.2. TE77 Tribotest ...................................................................................................... 38 3.2.1. Introduction to TE77 ...................................................................................... 38 3.2.2. TE77 Test Specimens .................................................................................... 40 3.2.3. TE77 Test Conditions .................................................................................... 42 3.2.4. Data Sampling of TE77 ................................................................................. 43 3.2.5. Treatment for TE77 Post-test Specimens ...................................................... 45 3.3. Mini Traction Machine (MTM) Tribotest ............................................................ 46 3.3.1. Introduction to MTM ..................................................................................... 46 3.3.2. MTM Test
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