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Tribo-Lyon 2013 A satellite conference of WTC’2013 Torino, Italy With the opportunity to organize two important tribology-related events, 40th Leeds-Lyon Symposium on Tribology and Tribochemistry Forum 2013, prior to the WTC'2013 Torino, the organizers have merged them into a Joint Event held at Lyon - France, from Wednesday 4th to Friday 6th September 2013. The Conference Organizing Committee is excited to welcome you at the conference center Espace Tête D’Or, located close to the famous Parc de la Tête d’Or in Lyon.

40th Leeds-Lyon Symposium on Tribology Leeds-Lyon at 40: is the past still present?

Since the Leeds-Lyon Symposium on Tribology was first conceived by Professors DOWSON and GODET in 1973, the participants have tackled the toughest problems in our field – indeed some of the most difficult problems in science and technology. Among the earliest conference themes proposed in Lyon were as follows: Super Laminar Flow in Bearings, Surface Roughness Effects in Lubrication, Thermal Effects in Tribology, The Running-in Process in Tribology, Mechanisms and Surface Distress … There have been notable successes and failures emerging from these topics. Since 1973, tribology can claim credit for such triumphs as extended trouble-free automotive life, previously unimaginable levels of information storage, and prosthetic joint replacement to improve the quality of life of an aging population. On the other hand, the fundamental origins of friction and wear in most applications remain a mystery. The 40th Leeds-Lyon anniversary seems like an appropriate time for a major retrospective. Each of these topics still has relevance. Thus we welcome papers on the vast array of previous Symposium subjects and particularly papers which can place current research in historical perspective.

Tribochemistry Forum 2013

Exploring tribochemical processes through computer simulation and/or advanced experiments

Improving the performance of increasingly severe sliding contacts is an important technological challenge, impacting economic and environmental issues. Regimes like mixed lubrication, boundary lubrication or solid lubrication are thus more frequently encountered, causing tribologically-induced chemical changes of rubbing surfaces. Tribochemistry Forum 2013 aims at fostering exchange and discussion for improving the knowledge and the understanding, down to the nanometer scale, of such tribochemical processes and their consequences on tribological performance. The conference will address issues related to the role of lubricant additives, nanoparticles, coatings, and related topics. Contributions are expected to promote innovative experimental and/or numerical approaches.

During the joint conference, more than 200 papers (talks and posters) will be presented, related to the following conference topics: T1- Extending the limits of lubrication granular lubrication, non linearities, free surfaces, boundary settings T2- Surface roughness effects wettability, numerical treatment, friction induced vibrations T3- Thermal effects in tribology high temperature interfaces, multiphase flow, rolling-sliding contacts T4- Running-in and surface distress surface damage, inspection & prevention, material transformation T5- Advanced tribometry in-situ analyses, experimental modeling, gas phase lubrication T6- Computer simulation molecular dynamics, quantum chemistry The organizers are wishing all participants a fruitful conference and a nice stay in Lyon.

Tribo-Lyon 2013 committees Scientific committee Benyekba BOU-SAID & Jean-Michel MARTIN, chairmen Maria-Isabel DE BARROS & Philippe VERGNE, co-chairs

Local organizing committee Michel BELIN & Philippe VERGNE, coordinators

T1 - Nicolas FILLOT T2 - Fabrice VILLE T3 - Francesco MASSI T4 - Aurélien SAULOT T5 - Fabrice DASSENOY T6 - Clotilde MINFRAY Posters : Julien FONTAINE, David PHILIPPON & Christophe DONNET

http://tribo-lyon2013.sciencesconf.org/

Sandrine BEC Yves BERTHIER Benyekba BOU-SAID Anne-Marie COLIN Fabrice DASSENOY Maria-Isabel DE BARROS Sophie DE OLIVEIRA Nicolas FILLOT Julien FONTAINE Francesco MASSI Clotilde MINFRAY David PHILIPPON Aurélien SAULOT Fabrice VILLE

The Leeds-Lyon Symposia on Tribology: an historical perspective

Leeds

Lyon

1 Cavitation and Related Phenomena in Lubrication, 1974 rd 3 The Wear of Non-Metallic Materials, 1976 th 5 Elastohydrodynamics and Related Topics, 1978 th 7 Friction and Traction, 1980 th 9 Tribology of Reciprocating Engines, 1982 th 11 Mixed Lubrication and Lubricated Wear, 1984 th 13 Fluid Film Lubrication - Osborne Reynolds Centenary, 1986 th 15 The Tribological Design of Machine Elements, 1988 th 17 Vehicle Tribology, 1990 th 19 Thin Films in Tribology, 1992 st 21 Lubricants and Lubrication, 1994 rd 23 Elastohydrodynamic: Fundamentals and Applications in Lubrication and Traction, 1996 th 26 Thinning films and Tribological Interfaces, 1999 th 29 Tribology Research and Design for Engineering Systems, 2002 st 31 Life Cycle Tribology, 2004 rd 33 Tribology at the Interface (nano-, bio-, boundary/mixed-lubrication), 2006 th 35 Duncan Dowson at 80, 2008 th 37 Tribology for Sustainability: Economic, Environmental and Quality of life, 2010 th 39 Great Challenges in Tribology, 2012

2 Super Laminar Flow in Bearings, 1975 th 4 Surface Roughness Effects in Lubrication, 1977 th 6 Thermal Effects in Tribology, 1979 th 8 The Running-in Process in Tribology, 1981 th 10 Numerical and Experimental Methods in Tribology, 1983 th 12 Mechanisms and Surface Distress, 1985 th 14 Interface Dynamics, 1987 th 16 Mechanics of Coatings, 1989 th 18 Wear Particles: From the Cradle to the Grave, 1991 th 20 Dissipative Processes in Tribology, 1993 nd 22 The Third Body Concept Interpretation of Tribological Phenomena, 1995 th 25 Lubrication at the Frontier: The Role of the Interface and Surface Layers, 1998 th 27 Tribology Research: From Model Experiment to Industrial Problem, 2000 th 30 Transient Processes in Tribology, 2003 nd 32 Interactions of Tribology and the Operating Environment, 2005 th 34 Tribological Contacts and Component Life, 2007 th 36 Multi Facets of Tribology, 2009 th 38 Energy and Health, 2011 th 40 Leeds-Lyon at 40: Is the past still present? 2013

st

nd

th

24 Tribology of Energy Conservation, London, 1997 28 Boundary and Mixed Lubrication: Science and Application, Vienna, 2001 th

The first Leeds-Lyon Symposium on Tribology was held in Leeds in September 1974. Since then, the two partners (the Institute of Tribology of the University of Leeds and the Laboratoire de Mécanique des Contacts of the Institut National des Sciences Appliquées de Lyon) have organized the symposium on an alternate year basis. This rule was not applied on only two occasions: - In 1997, the Symposium was held at Imperial College in London, a few days prior the 1st World Tribology Congress organized by the Tribology Group of the Institution of Mechanical Engineers, - In September 2001, the Symposium was run in co-operation with the 2nd Word Tribology Congress, hosted by the Austrian Tribology Society in Vienna. From the very start, this tribology-related event attracted many participants from countries all around the world. More than 130 delegates attended the first Symposium. Another remarkable feature concerns the publication of the proceedings. Over some 40 years, the organizers have published the Symposium proceedings according to the highest editorial standards. For the first 31 years, the papers and discussions were fully published in a hard-cover book format. Since the 32nd Symposium, the authors have been invited to submit a full length article to a Special Issue of either Tribology International or the Journal of Engineering Tribology. The papers are published in accordance with the normal processes and format of these journals. The earliest conference themes proposed in Lyon were as follows: Super Laminar Flow in Bearings (1975), Surface Roughness Effects in Lubrication (1977), Thermal Effects in Tribology (1979), The Running-in Process in Tribology, and Mechanisms and Surface Distress (1981), etc. The organizers believe that these topics still have relevance and can be fruitfully debated one more time. Thus, we look forward gathering our community at the 40th Leeds-Lyon on Tribology to tackle the interesting question embodied in the current theme: Is the Past Still Present?

Pr. Benyekba BOU-SAID, Chair Dr. Philippe VERGNE, Vice-Chair

Tribochemistry Forum: an historical perspective

The Tribochemistry Forum has been formerly held by the Tribochemistry Technical Committee, Japanese Society of Tribologists (JAST) as a satellite Forum of the International Tribology Conference in Japan (ITC) and/or the World Tribology Congress (WTC) in Japan in order to deepen the science and technology of Tribochemistry through presentations and discussions in the light of the latest findings. The Forums were held successively in: - Tokyo in 1995 satellite of ITC in Yokohama - Tsukuba in 2000 satellite of ITC in Nagasaki - Nara in 2005 satellite of ITC in Kobe - Kyoto in 2009 satellite of WTC IV in Kyoto - Hagi in 2011 satellite of ITC in Hiroshima. During the 6th Tribochemistry Forum, many important aspects of tribochemistry will be presented and discussed, such as tribo-physics, surface analysis, tribo-corrosion tribology. In 2013, a special attention will be paid to advanced in situ techniques and computer simulations. Important fields of tribology are concerned: boundary and EHL lubrication regimes, dry and vacuum tribology, nanolubricants, coatings, ionic liquids, superlubricity and so on. We are grateful if the Forum can stimulate, emulate and initiate further developments through discussions of the most recent results. International advisory board of the 6th Tribochemistry Forum: Pr. ADACHI Koshi, Tohoku University, Japan Pr. CARPICK Robert W., University of Pennsylvania, USA Dr. CROCKETT Rowena, EMPA Duebendorf, Switzerland Dr. DIENWIEBEL Martin, Karlsruhe Institute of Technology, Germany Pr. DONNET Christophe, Université Jean Monnet, France Dr. ERDEMIR Ali, Argonne National Laboratory, IL, USA Dr. FISCHER Alfons, University Duisburg-Essen, Germany Pr. HIRATSUKA Kenichi, Chiba Institute of Technology, Japan Dr. HIRAYAMA Tomoko, Doshisha University, Japan Pr. KAJDAS Czeslaw, Warsaw University of Technology, Poland Pr. KALIN Mitjan, University of Ljubljana, Slovenia Pr. LIU Weimin, Lanzhou Institute of Chemical Physics, PRC Dr. MISCHLER Stefano, Ecole Polytechnique Fédérale de Lausanne Lausanne, Switzerland Pr. MIYAMOTO Akira, Tohoku University, Japan Dr. MONTMITONNET Pierre, MINES ParisTech, France Pr. MORI Shigeyuki, Iwate University, Japan Pr. NAKAYAMA Keiji, Chiba Institute of Technology, Japan Pr. ROSSI Antonella, University of Cagliari, Italy Pr. SINNOTT Susan, University of Florida, USA Pr. SPENCER Nicholas D., ETH Zurich, Switzerland Pr. SPIKES Hugh, Imperial College, UK Pr. STACHOWIAK Gwidon, University of Western Australia, Australia

Pr. Jean-Michel MARTIN, Chair Dr. Maria-Isabel DE BARROS-BOUCHET, Vice-Chair

Table of Contents Wednesday, September 4, 2013 - 14:40 - 15:25 CARACAS - BRASILIA : Plenary conference Tribochemistry and tribocorrosion; understanding the interface to design better engineering systems, A. Neville ..............................................................................................................................................................................1

Wednesday, September 4, 2013 - 15:45 - 17:05 CARACAS - BRASILIA : T5/6 - Chemical and structural activation in tribology I Position-Shift of Triboplasma Generation Observed by Temperature Measurement as the Origin of Tribochemical Reactions, K. Nakayama ......................................................................................................................................2 Atomistic simulation on the sliding of a rigid indenter over aluminum with crystalline defects, E. Bortoleto [et al.] ....................................................................................................................................................................... 3 Effect of temperature on chemical activity of nascent steel surface, S. Mori [et al.] ......................................... 4 Tribochemical effects during running-in of metals and alloys, M. Dienwiebel [et al.] ...................................... 5

LIMA : T1 - Elastohydrodynamic lubrication Effect of Hertzian Contact Pressure on Shear Stress Distribution of EHL Oil Films, T. Mawatari [et al.] ........6 Transient effects and associated time scales in thermal elasto-hydrodynamic line contacts, J. Raisin [et al.] ...7 Reduced Finite Element Elastohydrodynamic Lubrication Model: Circular Contacts, W. Habchi.....................8 Model order reduction on stationary and dynamical isothermal Newtonian EHD contacts, D. Maier [et al.] ...9

MEXICO : T2 - Biotribology I Influence of Surface Roughness on the Fretting-Corrosion Regimes and Characteristics of Cemented Femoral Stems, B. Michael [et al.] ..................................................................................................................................10 Influence of surface morphology on mechanical properties of polyethylene. Tribological consequences in a biomimetic environment, M. Popa [et al.] ........................................................................................................ 11 Effect of mental sweating on fingertip friction, K. Mizuhara [et al.] ............................................................... 12 An Evaluation of the Needed Dimples Spacing and Roughness of Hip Joint Prosthesis Articulating Surfaces at Partially Regular Surface Texture, V. Pakhaliuk [et al.] ................................................................................... 13

Wednesday, September 4, 2013 - 17:20 - 18:20 CARACAS - BRASILIA : T5/6 - Graphitic materials in tribology Nanofriction properties of graphite tribofilms: influence of the tip/sample interface, G. Minatchy [et al.] .....14 Experimental and theoretical investigations of friction properties of graphite intercalated compounds., J. Mansot [et al.] ................................................................................................................................................................ 15 Exfoliation of Graphene from C60 monolayer, K. Miura [et al.] ..................................................................... 16

LIMA : T2 - Contact mechanics Influence of a single asperity on stresses during lubricated sliding contact on DLC-coated system, G. Pagnoux [et al.] ................................................................................................................................................................ 17 Surface Star Defect Tolerance Assessment on finished Silicon Nitride balls in Rolling Contact, A. Awan [et al.] I

............................................................................................................................................................................18 Elastic contact between representative rough surfaces, V. Yastrebov [et al.] ................................................... 19

MEXICO : T2 - Friction and wear I Probing the micromechanics of a multi-contact interface at the onset of frictional sliding, A. Prevost [et al.] ... 20 Wear Depth Evaluation During Erosion of X65 Carbon Steel Using RMS Values of Measured Acoustic Emission Signals, J. Ukpai [et al.] .................................................................................................................................... 21 Sliding Friction by a Liquid Meniscus Bridge between Parallel Plates, T. Kentaro [et al.] ............................. 22

Wednesday, September 4, 2013 - 18:30 - 20:00 Posters - Coatings & Surfaces Analysis by Scratch Method of Coatings of AISI5115 and M31 Steels Coated with AlTiN and CrN Using PVD Method, A. Aytaç [et al.] ................................................................................................................................... 23 Development of a combined optical lever atomic force microscope with a quartz crystal microbalance, D. Inoue [et al.] ................................................................................................................................................................ 24 Effects of Doping Elements on the Tribological Properties of DLC films, H. Fukuda [et al.] .........................25 Influence of Nitrogen on Friction Properties of CNx Coatings Based on First-Principles Molecular Dynamics and Tight-Binding Quantum Chemical Molecular Dynamics Methods, S. Sato [et al.] ...................................26 Mechanical Response of Coated Surfaces under Severe Contact Loading, A. Elwafi [et al.] ..........................27 Neutron reflectometry of adsorbed additive layers on (a-C) DLC, R. Simic [et al.] ........................................28 Structure and Properties of Titanium Doped Tungsten Bisulfide Thin Films Produced by Magnetron CoSputtering DC Technique, J. De la roche yepes [et al.] .................................................................................... 29 The Effect of Si and W Dopants on the Mechanical and Tribological Properties of Diamond-Like Carbon, L. Austin [et al.] .....................................................................................................................................................30 Tribological and Electrical Contact Behavior of Metal/DLC Nanocomposite Coating on Brass Substrate, R. Hombo [et al.] ................................................................................................................................................... 31 Tribological behaviour of ZrCN PVD and other DLC coatings for engine components, A. Igartua [et al.] ....32 Tribological performance of Cr/CrN and Cr/CrN/CrAlN multilayer coatings deposited by r.f. magnetron sputtering, N. Beliardouh [et al.] .......................................................................................................................33 Tribological properties of Ti(CN)x hard coating on titanium alloy by pulsed plasma electrolytic carbonitriding process, Y. Qin [et al.] ....................................................................................................................................... 34

Posters - Fluid Lubrication CFD Investigation of hydrodynamic lubrication on textured surface - Effects of interaction between dimples, Y. Oshima [et al.] ...................................................................................................................................................35 Combined Experimental and Numerical Study of PTFE Faced Thrust Bearings Considering Effect of Creep on Bearing Performance, B. Rothwell [et al.] ........................................................................................................36 Film thickness equations for line-contact thermal elastohydrodynamic lubrication under misaligned loads, Z. Wang [et al.] ...................................................................................................................................................... 37 Finite Line Contacts EHL Analysis of Misaligned Logarithmically Profiled Roller, T. Park........................... 38 II

High-tech anti-wear lubricant based on carbon nanotube/ionic liquid combination, T. Taaber [et al.] ............ 39 Lubricant Rheology Effect on Roughness Behavior in EHL Contacts, P. Sperka [et al.] .................................40 Modeling of the edge effects for Main Bearings of a Multi-supporting Crankshaft of an Internal Combustion Engine: the Theory, J. Rozhdestvenskiy [et al.] ................................................................................................41 Research on Causes of Cavitation Generation on Textured Surface under Hydrodynamic Lubrication, R. Tsuboi [et al.] ................................................................................................................................................................ 42 Thermal Friction Analysis of a Single-Nut Preloaded Ball-Screw, C. Wei [et al.] ...........................................43 Tribological properties of halogen-free ionic liquids against sintered ceramics, Y. Kondo [et al.] ..................44

Posters - Lubricant Additives 1,3-Diketone Fluids and their Complexes with Iron, M. Walter [et al.] ........................................................... 45 Adsorption of fatty acids on steel and gold surfaces: An in-situ XPS study, C. Matta [et al.] ......................... 46 Comparative study of tribological behaviour of steel/steel and steel/nanocristallin diamond contacts lubricated by organomolybdenum and ZnDTP, O. Gorbatchev [et al.] ............................................................................. 47 Effect of Lubricant Chemistry on the Camshaft Friction and Follower Rotation, R. Mufti [et al.] ................. 48 Effects of iron oxide layers on adsorption mechanism of C18 fatty acid: A computational study, S. Loehlé [et al.] ..................................................................................................................................................................... 49 Experimental analysis of tribological properties of chemically modified bio-based lubricant with nanoparticle additives, N. Mohd zulkifli [et al.] ....................................................................................................................50 Impact Study of Fuel Additives in Piston Ring Cylinder Liner Contact, C. Forest [et al.] .............................. 51 Influence of the structural characteristics of IF-MoS2 nanoparticles on their lubrication mechanisms, I. Lahouij [et al.] ................................................................................................................................................................ 52 Microencapsulation for Next Generation Lubrication, K. Mitchell [et al.] ...................................................... 53 Optimized Nanolubricant for Friction Reduction, M. Abdullah [et al.] ............................................................54 Quantum Chemical Molecular Dynamics Simulations of Chemical Mechanical Polishing Processes for Silicon Wafer by SiO2 Abrasive Grain, K. Kawaguchi [et al.] .....................................................................................55 Speed-Dependent Friction Characteristic of ZnDTP Having Linear Hydrocarbon Moiety, S. Aoki [et al.] .... 56 Study of GMO concentration on the boundary lubricated W-doped DLC coatings, L. Yang [et al.] ............... 57 The research on tribological behaviors of lubricating oil in TFL, J. Zhang...................................................... 58 Towards a better understanding of warm mix asphalt additives, F. Geisler [et al.] .......................................... 59 Tribological behaviour of fullerene-like MoS2 nanoparticles for different lubrication regimes in the presence of dispersants, P. Rabaso [et al.] ............................................................................................................................60

Posters - Materials for Tribology A micromechanical approach for the wear prediction of fiber-reinforced composites, D. Yang [et al.] .......... 61 Alloying process for Cu-Zn mixed powder using the tribo-mechanical approach, H. Miki [et al.] .................62 An Experimental Study of the Impact Erosion for high Pressure pipe Manifold, J. Fan [et al.] ...................... 63 Biomimetic Sealing System for Power Generation from Natural Energy, Y. Nakanishi [et al.] .......................64 Comparative Tribological study of biomaterials AISI 316L and Ti6Al7Nb, M. Fellah [et al.] ........................65 Correlations between wear mechanisms and rail grinding operations., P. Cuervo [et al.] ................................66 Development of a novel component test to investigate railway switch slide baseplate tribology, A. Beagles [et

III

al.] ..................................................................................................................................................................... 67 Effect of heat dissipaters in a NA disc brake pad - Wear performance and influence on µ sensitivity towards pressure and speed, V. Thiyagarajan [et al.] ......................................................................................................68 Effect of Temperature on the Tribological Properties of the Polyimide Composites Reinforced with Different Fibres in Sliding and Erosive Conditions, G. Zhao [et al.] ...............................................................................69 Field measurement of coefficient of friction in rails using a hand-pushed tribometer, Y. Areiza [et al.] ......... 70 Mechanical Characteristic Analysis of Micro-gear Meshing Transmission, W. Zhenlu [et al.] ....................... 71 Micro-contact parameters and specific dissipated friction power during self-mating reciprocating sliding wear tests of a martensitic steel, D. Stickel [et al.] ....................................................................................................72 Modeling of the abrasive tool wear in metal cutting: Influence of the sliding-sticking contact zones, F. Halila [et al.] ................................................................................................................................................................ 73 Prevent/Limit Edge Loading in Total hip Replacement, E. Torabi kachousangi [et al.] ...................................74 Study of nitrided steel R6M5 abrasive wear-resistance, B. Rakhadilov [et al.] ............................................... 75 Synergy between tribo-oxidation Mechanically Mixed Layer (MML) and strain rate response on governing the dry sliding wear behavior of Ti-6Al-4V against SS316L, J. Ashok raj [et al.] .................................................76 The development of friction tester in pressurized hot water at 30 MPa and 300 degree C, Y. Yagi [et al.] ..... 77 The Running-in Behavior of AlSi as a function of Si morphology and final machining, D. Linsler [et al.] ....78 Wear Measurement and Analysis of Explanted Acetabular Cups, M. Uddin.................................................... 79 Wear phenomena and simulation of hot shearing process, M. Varga [et al.] .................................................... 80

Posters - Surface Engineering A benchmark of filtering methods for tribological surfaces, G. Le goic [et al.] ...............................................81 Application of Surface Modification for Airplanes Winglets, Z. Ibrahim [et al.] .............................................82 Consideration of combined water intrusion/drainage effects in the prediction of road skid resistance, M. Do [et al.] ..................................................................................................................................................................... 83 Decomposition of a tribological system by chaos theory, M. Bigerelle [et al.] ................................................84 Friction and material transfer of a textured wafer surface during sliding, H. Xiao [et al.] ...............................85 In-situ observation of the friction/water depth relationship, V. Cerezo [et al.] .................................................86 Laboratory test to evaluate the effect of contaminants on road skid resistance, M. Do [et al.] ........................87 Microstructure and wear resistance changes of 30CrMnSiA steel modified surface layers by electrolyte-plasma processing, M. Skakov [et al.] ...........................................................................................................................88 Numerical Modeling for Cold Sprayed Particle Deposition, J. Xie [et al.] ...................................................... 89 Relationship between brightness and roughness of polypropylene abraded surfaces, D. Najjar [et al.] .......... 90 Roughness and Wetting, a Multiscale Approach, V. Belaud [et al.] ..................................................................91 Running-in process of Si-SiOx/SiO2 pair at nanoscale, L. Qian [et al.] .......................................................... 92 Scuffing of spiral bevel gears, M. Kalbarczyk [et al.] ...................................................................................... 93 The Representative Topography of Worn Hot Rolling Mill Cylinders, E. Luc [et al.] .....................................94 Topographical and ellipsometrical analysis of orange peel on polished steel surfaces, M. Miranda-medina [et al.] ..................................................................................................................................................................... 95 Topographical Model Selection in Tribology, S. Tchoundjeu [et al.] ............................................................... 96 Tribological Performance of PTFE + Taillings of Scheelite Composites, J. Souza [et al.] .............................. 97

IV

Wear Behavior of Magnesium Alloys AZ31B and its Composites, Q. Nguyen [et al.] ....................................98

Thursday, September 5, 2013 - 08:30 - 09:15 CARACAS - BRASILIA : Plenary conference Towards an atomic scale understanding of wear in carbon materials and metals, M. Moseler......................... 99

Thursday, September 5, 2013 - 09:35 - 10:55 CARACAS - BRASILIA : T5/6 - Diamond-Like Carbon: Solid and boundary lubrication First-Principles Calculation on the Structure Transition of Diamond to Graphene in Si-Doped DLC, S. Bai [et al.] ................................................................................................................................................................... 100 Investigating the Tribochemistry of Silicon Oxide-Doped Diamond-Like Carbon: from Ultra-High Vacuum Systems to the International Space Station, F. Mangolini [et al.] ................................................................... 101 Formation process of metal-rich tribo-film on the counter face during sliding against metal/diamondlike-carbon nanocomposite coatings, M. Goto [et al.] ....................................................................................................... 102 The Origin of the Tribofilm Formed in DLC/MAC Lubrication Using 13C-DLC, M. Iwaki [et al.] ............ 103

LIMA : T1 - Biotribology II Friction of 316L Stainless Steel on Soft-tissue-like Poly (vinyl alcohol) Hydrogel in Physiological Liquid, H. Kosukegawa [et al.] .........................................................................................................................................104 Tribological study of oral care silica, S. Descartes [et al.] ..............................................................................105 Comparison of Sliders for Tactile Friction Measurements, B. Henson [et al.] ...............................................106

MEXICO : T2 - Surface texturing I Relation between roughness and surface hardening after ultrasonic shot peening, J. Marteau [et al.] ...........107 Surface Characterization of Ultrasonic Shot Peening Surface, J. Marteau [et al.] ......................................... 108 Quantitative approach to determine the mechanical properties of sandblasted materials by nanoindentation, Y. Xia [et al.] ........................................................................................................................................................109 Influence of machining-induced 3D surface roughness on component's performance, Q. Zeng [et al.] ........110

Thursday, September 5, 2013 - 11:10 - 12:30 CARACAS - BRASILIA : T5/6 - Organic films and additives Oil-Compatible Polymer-Brush Coatings for Lubrication, R. Bielecki [et al.] .............................................. 111 Ab initio adsorption of organic additives on an iron surface, P. Bedolla velazquez [et al.] ........................... 112 In-situ observation of additive concentration and molecular interaction in EHL contact using micro-FTIR, K. Takiwatari [et al.] ............................................................................................................................................ 113 Coupling experimental and numerical approaches to study adsorption mechanism of stearic acid on iron based surfaces, C. Minfray [et al.] ............................................................................................................................ 114

LIMA : T3 - Thermal effects on special materials in tribology Experimental Validation of a Thermal Model of a LOx Flooded Ball Bearing, J. Bozet [et al.] ....................115 Tribological Conditions leading to the Ignition of an Energetic Material, R. Charlery [et al.] ...................... 116 V

Selective choice of high temperature wear resistant materials, M. Varga [et al.] ........................................... 117 The Thermal Properties of Polyaryletherketones (PAEKs) and their Influence on Tribological Performance, C. Dyson [et al.] ...................................................................................................................................................118

MEXICO : T2 - Surface texturing II Tribological behaviors of textured surfaces under lubricated point contact conditions, P. Pawlus [et al.] .....119 Identification of lubrication regime on textured surfaces by multi-scale decomposition, C. Hubert [et al.] ..120 Tribological Properties of PTFE / Laser Surface textured Stainless Steel under Lubrication, D. Xiong [et al.] .. 121 Tribological comparison of three typical wrinkled surface on the elastomeric polymer, Z. Xiaoli [et al.] .... 122

Thursday, September 5, 2013 - 14:00 - 15:50 CARACAS - BRASILIA : T5/6 - Tribochemistry of sulfur and phosphorous compounds Ab initio investigation of atomistic mechanisms in solid and boundary lubrication, M. Righi [et al.] ..........123 Wear and sulphur chemistry of the tribolayer, M. Jech [et al.] ....................................................................... 124 Tribochemical mechanism of superlubricity of phosphoric acid: a reactive molecular dynamics study, D. Yue [et al.] .............................................................................................................................................................. 125 Tribological performance of DLC/cast iron and steel/cast iron system when lubricated in fully formulated oils with different concentration of MoDTC-type friction modifier., S. Kosarieh [et al.] .....................................126 Real time MoS2 formation and friction performance, Y. Rai [et al.] ..............................................................127

MEXICO : T4 - TTS and Material evolution A thermo-mechanical model for TSTs based on TRIP, and numerical treatment, F. Lebon [et al.] ............... 128 Role of white etching layer on rail squat formation, S. Simon [et al.] ............................................................129 Study of modified layers on 316L steel created by friction stir process, C. Langlade [et al.] ........................ 130 Understanding White Etching Cracks (WEC) in rolling element bearings: the effect of hydrogen charging, A. Ruellan [et al.] .................................................................................................................................................131 Subsurface Deformation and Structural Changes during Scuffing of Steel, H. Li [et al.] ..............................132

Thursday, September 5, 2013 - 14:10 - 15:50 LIMA : T1 - Complex fluids I Ice Lubrication for Transporting Heavy Stones to the Forbidden City in 15th - 16th Century China, J. Li [et al.] ..........................................................................................................................................................................133 How does the water mixed with Ionic Liquids behave under lubricating condition?, S. Watanabe [et al.] ... 134 Halogen-Free Ionic Liquids Composed of Bis(salicylato)borate Anion as Lubricants Additive, R. Gusain [et al.] ..........................................................................................................................................................................135 Study on Ionic Liquids in the Electric Field, S. Kawada [et al.] .....................................................................136 Electrochemical control of lubrication by ionic liquids, R. Bennewitz [et al.] ...............................................137

Thursday, September 5, 2013 - 16:10 - 18:00 CARACAS - BRASILIA : T5/6 - Complex tribochemical environments VI

Ionic Liquids-Graphene composite carbon-based lubricating films, Q. Xue [et al.] ...................................... 138 Surface-analytical investigation of boundary films formed in silica contacts lubricated by trifluoro tris (pentafluoroethyl) phosphate-based ionic liquids, A. Arcifa [et al.] ...............................................................139 First-Principles Calculation on CMP Process of Glass Surface by CeO2 Particle and Design of Alternative Abrasive Grain, N. Ozawa [et al.] ...................................................................................................................140 Fretting corrosion comparison between 316L SS and CoCrMo alloys.Effect of Ti content on cast alloys CoCrMo, J. Geringer [et al.] ............................................................................................................................................141 Reliability enhancements in hard disk drives using in-situ vapor phase additives, V. Raman [et al.] ............142

LIMA : T3 - Thermal effects on highly loaded contacts Contact temperatures during sliding contact and their influence on wear, F. Kennedy...................................143 Bichromatic measurement of thermal fields induced by friction, E. Berté [et al.] ......................................... 144 Effect of Temperature on Micro-Pitting Strength of Carburized Steel, M. Hirano [et al.] ............................. 145 Identification of thermal/friction laws governing the tool-workmaterial interface behaviour and their integration in a FE code for machining processes analyses, B. Haddag [et al.] ................................................................146 Erosive wear behavior of steel and iron material under the stress state, B. Sun [et al.] ................................. 147

Thursday, September 5, 2013 - 16:20 - 18:00 MEXICO : T2 - Surface roughness: Modelling Determination of the Friction Coefficient of Mixed Lubricated Contacts by Means of the Finite Element Analsyis, B. Lorentz [et al.] ............................................................................................................................................ 148 Multiresolution analysis of tribological surfaces, D. Bianchi [et al.] ............................................................. 149 New averaged Reynolds equation based on wall slip boundary conditions, A. Fatu [et al.] .......................... 150 On the modeling of two bonded silicon surfaces, N. Cocheteau [et al.] .........................................................151 A model of watertight based on fluid movement percolation on 3D rough surfaces, R. Deltombe [et al.] ....152

Friday, September 6, 2013 - 08:30 - 10:00 CARACAS - BRASILIA : T5/6 - Diamond-Like Carbon: Structural and chemical modifications Tribochemical Reaction Dynamics of Diamond-Like Carbon and Its Related Materials by First-Principles and Tight-Binding Quantum Chemical Molecular Dynamics Simulations, M. Kubo [et al.] ............................... 153 In situ Observation of the Structural Changes of DLC during Friction Motion, K. Sasaki [et al.] ................ 154 Role of graphite-like tribofilm on the friction reduction of DLC films, T. Ma ............................................... 155 Adsorption of polar molecules on DLC coatings, M. Kalin [et al.] ................................................................156

MEXICO : T2 - Surface roughness and lubrication Surface roughness effects in elastohydrodynamic lubrication, G. Morales-espejel........................................ 157 Study DLC coating influence on lubrication regime transition, C. Héau [et al.] ............................................158 Effects of Surface Ridges on EHL Films under Impact Loading, H. Nishikawa [et al.] ................................ 159 Effect of Lubricity of Drilling Fluids on Buckling and Lockup of Coiled Tubing in Drilling Operations, J. Abdo [et al.] .............................................................................................................................................................. 160

VII

Friday, September 6, 2013 - 08:40 - 10:00 LIMA : T1 - Complex fluids II High Pressure Behavior of Oil Extracted from Green Alga Botryococcus braunii, B. Zhang [et al.] ............161 Proposal of a General Method to Investigate Long Term Interactions between Minor Components of Complex Lubricant Formulations, M. Fox...................................................................................................................... 162 The Static and Dynamic characteristics of an Offset Journal Bearing Lubricated with micropolar Fluid, C. Boualem........................................................................................................................................................... 163 Observation of lubrication behaviours by a liquid droplet, F. Guo [et al.] ..................................................... 164

Friday, September 6, 2013 - 10:20 - 12:10 CARACAS - BRASILIA : T5/6 - Chemical and structural activation in tribology II The Surface Chemistry of Boundary Film Formation, W. Tysoe.....................................................................165 Development of Multi-scale, Multi-physics Simulators for Tribochemical Applications, A. Miyamoto [et al.] . 166 Atomic-scale Processes in Adhesion and Wear Elucidated by In Situ TEM Tribological Studies and Atomistic Modeling, R. Carpick [et al.] .......................................................................................................................... 167 Understanding the Mechanisms of Friction in Pure Metals, Alloys and Composites, M. Chandross [et al.] .168 Numerical study of lubrication properties of dry granulates and suspensions, C. Bierwisch [et al.] ............. 169

LIMA : T1 - Challenges in lubricated systems A new concept in cavitation modelling, A. Almqvist [et al.] .......................................................................... 170 New mass conserving cavitation algorithm originating from compressible fluid models, G. Bayada............171 Experimental study of hydrodynamic spiral groove mechanical seals, A. Djamaï [et al.] ............................. 172 An Ultrasonic Investigation of Lubrication on the Tool/Chip Interface, A. Abodena [et al.] .........................173 Measurement of Piston Ring Pack Lubricant Residence Time in a Gasoline Engine using Laser Induced Fluorescence, R. Notay [et al.] ........................................................................................................................174

Friday, September 6, 2013 - 10:30 - 12:10 MEXICO : T4 - Friction and Wear II Rubbing force estimation during blade/seal interaction, R. Mandard [et al.] .................................................175 Wear and Friction Behaviour of PA12, PVDF, PEEK and PPS Polymer Tapes, O. Burke [et al.] .................176 Friction modification of the wheel/rail contact - A comparison between full-scale and twin disc experimentation, L. Buckley-johnstone [et al.] ...........................................................................................................................177 Microstructure based modeling of angular impact on a martensitic steel and a metal matrix composite, A. Laukkanen [et al.] ............................................................................................................................................178 Comparison of Adhesive Force of Additive's Layer on The Rubbed Surface Using Microscopic Methods, H. Kaleli [et al.] ....................................................................................................................................................179

Friday, September 6, 2013 - 13:40 - 15:00 CARACAS - BRASILIA : T5/6 - Diamond-Like Carbon: Interactions with lubricant additives The Effects of Si-Dopant on the DLC Coating Tribological Performance and Tribofilm Formation Lubricated VIII

by Organic Friction Modifier-Containing Engine Oil Formulations, H. Zhao [et al.] ....................................180 Comparing the benefits of a rapidly-formed tribofilm against less tribological active DLCs over time, J. Lanigan [et al.] .............................................................................................................................................................. 181 Tribochemistry of the lubricant additives/WDLC system under Boundary Lubrication, L. Yang [et al.] ......182 Friction and Wear Characteristic of DLC Coatings with Different Hydrogen content Lubricated with Several Mo-containing Compounds and Their Related Compounds, M. Masuko [et al.] ...........................................183

LIMA : T1 - Friction and wear III Numerical study of the initiation and propagation of fretting-fatigue cracks in a TA6V polycrystal, C. Nigro [et al.] ................................................................................................................................................................... 184 A 3D Linear Elastic Multigrid Model for Strongly Heterogeneous Materials, H. Boffy [et al.] ....................185 Analysis of the mechanical and chemical wear components by combining multi-asperity nanotribology and discrete numerical simulation, P. Stempfle [et al.] ..........................................................................................186 Conjecture on limits of boundary lubrication, L. Wojciechowski [et al.] .......................................................187

MEXICO : T2 - Vibrations Modeling Vibrations Due to Surface Roughness at Planar Sliding Contacts, A. Soom [et al.] ......................188 An Experimental Study of the Frictionally Induced Vibrations on Rough Textile Fabrics, B. Sümer [et al.] 189 Unidirectional wetting of anisotropic textured GaSb surfaces, E. Contraires [et al.] .....................................190 Reducing disc brake squeal by sawed-groove texturing - A combined approach of complex eigenvalue analysis and dynamic transient analysis, D. Wang [et al.] ............................................................................................ 191

Friday, September 6, 2013 - 15:20 - 16:40 CARACAS - BRASILIA : T5/6 - Interfacial processes at small scales Tribological Properties and Mechanism of Graphene by Computational Study, Q. Zhang [et al.] ................ 192 Molecular Dynamics Study of Lubrication Phenomena of Nanoscale Liquid Bridge between Surfaces, T. Tokumasu [et al.] .............................................................................................................................................193 Friction Phase Diagram of Frenkel-Kontorova Atomistic Model, M. Hirano [et al.] .....................................194 SEM Observation Study for Recognition of Wear Mechanism Using AE Technique, A. Hase [et al.] ..........195

LIMA : T3 - Thermal effects on lubricated contacts Thermal modeling of a grease lubricated thrust ball bearing, A. Neurouth [et al.] ........................................ 196 A theoretical simulation of thermal EHL in impact motion, J. Wang [et al.] ..................................................197 Aircraft Landing Gear Slider Bearing Thermo-Elastohydrodynamic Concept Model, L. Heirendt [et al.] ... 198 The Effects of Oil Supply Pressure and Groove Position on Temperature and Pressure Profile in Journal Bearing Lubrication, M. Ahmad [et al.] ........................................................................................................................199

MEXICO : T4 - Surface Treatment and Coating Gas nitriding process : an effect on steels rolling contact fatigue life and behavior?, M. Le [et al.] ............. 200 Tribological advantages of nitrocarburizing over carbonitriding: influence of the composition and architecture of the compound layer, P. Cardey [et al.] ........................................................................................................ 201 IX

A study of the normal impact fatigue and impact wear behavior of thick hard carbide coatings, W. Richard [et al.] ................................................................................................................................................................... 202 Wear resistant multilayer nanocomposite WC1-x/C coating on Ti-6Al-4V titanium alloy, K. Kubiak [et al.] .... 203

X

40th Leeds-Lyon Symposium on Tribology &TribochemistryForum 2013 September 4-6, 2013, Lyon, France

Tribochemistry and tribocorrosion; understanding the interface to design better engineering systems Pr Anne Neville School of Mechanical Engineering, University of Leeds

In this paper both tribochemistry and tribocorrosion will be discussed; tribochemistry of DLC lubricated systems for engines and tribocorrosion of the hip joint. Engineering and biomedical systems may often be seen to be at different ends of the tribology spectrum but for both a detailed understanding of the chemical and electrochemical reactions and what their products are is required. Advanced surface analysis is key to this and enables engineers to then be able to design engineering systems with much improved functionality. The paper will discuss how some of the most advanced electron microscopy and spectroscopy has enabled the mechanisms of lubrication and wear to be understood and how this information is being used to move forward to the next generation of lubricated interfaces.

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40th Leeds-Lyon Symposium on Tribology & Tribochemistry Forum 2013 September 4-6, 2013, Lyon, France

Position-Shift of Triboplasma Generation Observed by Temperature Measurement as the Origin of Tribochemical Reactions K. Nakayama1* 1)

Chiba Institute of Technology, 2-17-1, Narashino, Chiba 275-0016, Japan *

Corresponding author: [email protected]

then shift to the rear gap of the sliding contact (7s). The rear plasma intensity increases (8s) and increases (9s) and then decreases (10s) and becomes very weak (11s). The phenomena occured repeatedly with one revolution time of 6s at ω = 10 rps. This process of the plasma generation is caused by the distribution of the tribocharge-induced surface potential as explained by the electron avalanche process as shown in Fig. 1 (below). It was also observed that distribution of the triboemission intensity of the negatively and positively charged particles from the plasma correlated well with the tribocharge-induced surface potential distribution.

1. Introduction Previously, it has been reported that triboplasma is generated in the rear gap of sliding contact. However, recently we have observed that the triboplasma is also generated in front of and inside of the sliding contact. Further, we have succeeded to measure the temperature distribution of triboplasma. This paper reports the distribution and flow of triboplasma generated in front of and in the rear gap of the sliding contact with the correlation of tribocharging distribution on the sliding surface. 2. Experimental procedure

4. Summary

Temperature distribution at and around the sliding contact was measured using a highly sensitive infrared camera (FLIRATS SC7600-BB) together with friction coefficient at a tribosystem of insulator/insulator, i.e., a diamond pin sliding with a tip radius r = 4mm on a sapphire disk under FN = 1N and the rotational velocity ω = 10 to 155 rpm (wear track dia. d = 40 mm). Tribocharge-induced surface potential was also measured simultaneously with the negatively and positively charged particles from the triboplasma using a non-contacting type surface potential measurement apparatus1) and the specially invented triboemission measuring apparatus2).

Triboplasma is non-equilibrium low temperature plasma. The position and intensity of the plasma change depending on the strength of the tribocharge where sliding contact is located. Namely, triboplasma position and intensity shift from the place “in front gap of”, through that “inside gap of” and to that “in the rear gap of” the sliding contact in one revolution of rotation. This means that triboplasma reactions occur not only in the rear gap but also in front of and inside of the sliding contact. 5. Acknowledgement The author would like to express his thanks to F. Yagasaki for his help to measure triboplasma temperature and also to the Ministry of Education, Science and Culture of Japan for the support by the Grant-Aid for Scientific Research.

3. Results and discussion Figure 1(above) shows time dependence nature of the temperature distributions at and around the sliding contact measured by the infrared camera at the second sliding revolution from 7s to 12 s under ω = 10 rps. The plasma temperature was very low and not greater than 0.15℃ at this rotational velocity. This means that the triboplasma is non-equilibrium low temperature plasma. In the second sliding revolution, the triboplasma was generated first in front of the sliding contact (6s) and 7s







8s



MM MM

e- eM e-



  -











M



9s





M

M   M  -





 M



M

-

1)

Nakayama, K., Tribocharging and friction in insulators in ambient air”, Wear 194, 1996, 185-189. Nakayama K., Suzuki N. and Hashimoto, H., “Triboemission of charged particles and photons from solid surfaces during frictional damage, J. Phys. D: Appl. Phys., 25, 1992, 303-308.

2)

10 s



 

 M 

ee- M e

11 s

    M 

M M

M

e

e- M e





6. References

-









M

M

M M

M



M 

ee- M e







 M

  

M

ee- M e

0.15 ℃ 



M

M -



12 s

-

M M

ee- M e

-

0.00 ℃

Fig. 1 Triboplasma temperature distributions (above) and electron avalanche process (below).

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40th Leeds-Lyon Symposium on Tribology & Tribochemistry Forum 2013 September 4-6, 2013, Lyon, France

Atomistic simulation on the sliding of a rigid indenter over aluminum with crystalline defects E.M. Bortoleto1*, R.M. Souza1 , M.G.V. Cuppari2 1)

Surface Phenomena Laboratory, Department of Mechanical Engineering, Polytechnic School of the University of São Paulo, Av. Prof. Mello Moraes 2231, 05508-900 São Paulo, Brazil. 2) Federal University of ABC – UFABC, Santo André, 09210-170, Brazil *

Corresponding author for [email protected]

1. Introduction This work presents a molecular dynamics (MD) study of contact, indentation and dry sliding of a rigid flat punch indenter over a previously deformed metallic Aluminum slab body. The slab was deformed by means of a hydrostatic pressure in order to generate crystal defects. The crystal defects in the slab were quantified using a local coordination analysis of the atoms at different times of the simulation. The pre-deformed slab was then subjected to indentation and followed by slip of a planar rigid indenter. The strain hardening effects on friction and adhesion were studied, as a function of the amount of defects, by measuring the penetration force and the friction force. The results show that the adhesion force between atomic layers is affected by the crystal defects density.

intermediate group, to which is applied a thermal bath condition using the Nose/Hoover thermostat algorithm; and, finally, the atoms layers that are free to move. Periodic boundary conditions with EAM potential, developed by Mishin et al. (1999) were used to describe the interactions between atoms. A cut-off radius of 6.28 Å was adopted. 3. Results and discussion Positions and velocities of each atom were calculated. Energy, temperature, stresses and reaction forces due to penetration and slip were also obtained. A disorder parameter of the crystalline lattice is evaluated to measure the evolution of crystalline defects (Fig. 2). Defect density affects the adhesion force between atomic layers. Defect density also affects the amount of material prow formed ahead of the indenter. Stick slip motion is also observed.

2. Materials and methods Four different models were developed, as shown in Fig. 1, each one with different initial crystalline defects and residual stress levels. The different amounts of crystalline defects were introduced by the imposition of different strains due to compression. Each model is divided into five steps of simulation: I. Initial assembly of the deformable block II. Equilibrium of the system III. Compression of the lower block IV. Vertical motion of the rigid indenter until the penetration of deformable block over 3 atomic layers V. Horizontal slip of the rigid indenter over deformable block

Fig. 2 - Disorder of crystalline lattice after different compression levels 4. Conclusions The results show that the adhesion strength between atomic layers is affected by defects density in metallic crystal. Contrary to the observed in macroscopic scale, increasing the amount of defects causes a reduction in the frictional force between the contact surfaces. 5. References [1]

Fig. 1 - Initial dimensions of each model

[2]

Each ensemble has 17,385 atoms, arranged in a rigid indenter and a deformable slab, both constituted by FCC aluminum cells with lattice parameter 4.05Å. The slab is organized in 3 regions: two fixed atomic layers; an

[3]

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Bhushan, B., “Contact Mechanics of Rough Surfaces in Tribology: Single Asperity Contact”, Applied Mechanics Reviews, 49, 5, 1996. Jinesh, K.B., “Atomic-Scale Friction: Thermal effects and capillary condensation”, PhD Thesis, Leiden University, 2006. Mishin, Y.; Farkas, D.; Mehl, M.J.; Papaconstantopoulos, D.A., Phys. Rev. B, 59, 1999, 3393-3407.

40th Leeds-Lyon Symposium on Tribology & Tribochemistry Forum 2013 September 4-6, 2013, Lyon, France

Effect of temperature on chemical activity of nascent steel surface S. Mori1*, T. Konno1, N. Shimotomai2, H. Nanao1 , K. Takiwatari3, Y. Hoshi1 1)

Faculty of Engineering, Iwate University, 4-3-5 Ueda, Morioka 020-8551, Japan. 2) Kyodoyushi Co. Ltd., 2-2-30 Tsujido Kandai, Fujisawa 251-8588, Japan. 3) Ichinoseki National College of Technology, Takanashi, Hagisho, Ichinoseki 021-8511, Japan *

Corresponding author for [email protected]

1. Introduction

Scratching 5.0

5.0E-08

D

4.6

4.6E-08

4.4

4.4E-08

D

D

D

D

110℃ 90℃ 70℃ 50℃ 34℃

D

m/e=84

4.2

4.2E-08

4.0

2. Experimentals

4.0E-08

0

1

2

3

Time, min

Scratching 4.5

4.5E-09

Ion Intensity,×10-9A

Nascent surface of steel was formed by scratching under high vacuum conditions. Sample gas was introduced from a variable leak valve, and evacuate continuously by TMP. Adsorption of sample gas and evolution of reaction products were monitored by a quadrupole mass spectrometer. Temperature of specimen was controlled by a heater and was monitored with a thermocouple. Mild steel and benzene, benzene-d6(C6D6) and ethyl alcohol were used as a specimen and sample gases, respectively. The temperature of specimen was controlled 30 to 110 ℃.

4.8

4.8E-08

Ion Intensity,×10-8A

Chemical reactions of lubricant components under boundary lubricating conditions are affected by the chemical activity of material surfaces. Although surface is covered with metal oxides under mild conditions, nascent metal surfaces formed under severe conditions play an important role on tribochemical reactions of lubricant components. We have been studying on chemical activity of nascent surfaces of metals and ceramics[1]. In this study, the effect of temperature on the chemical reactions was investigated using a unique method with a mass spectrometer.

34℃ 50℃ 70℃ 90℃ 110℃

4.0

4.0E-09

D2 m/e=4

3.5

3.5E-09

3.0

3.0E-09

3. Results and Discussion Benzene chemisorbed on nascent steel surface easily and hydrogen evolution as a decomposition product was observed. Adsorption rate of benzene decreased but hydrogen evolution rate increased at elevated temperature[2]. This suggests that there is a different hydrogen source except for benzene. Decomposition reaction is investigated by a tracer method using C6D6. The result is shown in Figure 1. It is obvious that adsorption rate of benzene decreased and desorption rate of deuterium as a decomposition product also decreased at elevated temperature. On the other hand, hydrogen evolution increased even under C6D6 atmosphere at elevated temperature. In conclusion, a competitive chemisorption of benzene and water as a component of residual gas occurred and water adsorption on nascent steel surface was accelerated at elevated temperature. The effect of temperature on chemisporption of organic compounds on nascent steel surface is also investigated.

2.5

2.5E-09

0

1

2

3

Time, min

Figure 1 Effect of temperature on C6D6 adsorption and D2 formation on nascent steel surface 4. Summary It was found that the chemisorption of organic compounds on nascent steel surface is affected by temperature. Acknowledgement This research was financially supported by GRENE project of MEXT. References [1] Mori, S., Appl. Surf. Sci., 27, 1987, 401-410. [2] Shimotomai, N., Nanao, H., Mori, S., Tribology Online, 7, 2012, 54-59.

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40th Leeds-Lyon Symposium on Tribology &TribochemistryForum 2013 September 4-6, 2013, Lyon, France

Tribochemical effects during running-in of metals and alloys Martin Dienwiebel1,2)*,Tim Feser1,2), Pantcho Stoyanov1,2) 1)

Institute of AppliedMaterials (IAM), Karlsruhe Institute of Technology (KIT), Kaiserstraße 12, D-76131 Karlsruhe, Germany 2) FhG-KIT MikrotribologieCentrum (μTC),P.O. Box 43 01 03, 76216 Karlsruhe, Germany * Corresponding author:[email protected]

1. Introduction The formation of third bodies of metallic alloys depends on the mechanical mixing of the first bodies, debris and the lubricant or the atmosphere. While many previous results on pure metals have shown that the formation of „mixed material‟ decreases friction and wear, inclusive correlations between the properties of this layer (e.g. thickness, structural, mechanical, and chemical) and the tribological properties have not yet been studied rigorously.

2. Experimental As examples of two very different alloys, reciprocating sliding tests are performed using an „on line‟ tribometer in order to monitor topographical changes on brass and tungsten [1]. This instrument consists of a force sensor, a holographic microscope, and an atomic force microscope. The experiments are performed in dry and lubricated conditions (i.e. hexadecane or PAO as lubricant). Wear and roughness measurements are performed after each cycle and correlated to the friction behavior, which is recorded at the position of the holographic microscope. Ex situ analysis is performed on the worn surfaces (i.e. plates and counterfaces) using X-ray photoelectron spectroscopy (XPS), AFM, and cross-sectional SEM imaging of the near-surface region.

subsequently to the initial plowing events, the sliding occurs mainly within an amorphized WC layer.Classical molecular dynamics simulations of W sliding against WC (i.e. with and without Hexadecane) with rough surfaces are consistent with these observations. The lubricated sliding, on the other hand, results in a less pronounced third body formation; while a thin transfer layer is observed on the WC counterface, only slight grain refinement is evident in the near surface region of the W specimen. Similarly to the dry sliding, these ex situ analysis are consistent with atomistic simulations; subsequently to the initial adjustment of the two surfaces (i.e. plowing events of the WC surface), the sliding occurs on monolayers of the lubricant, which results in low friction values due to the low viscosity of hexadecane [4].

4. References [1]

[2]

[3]

3. Results The tribometer experiments with brass (zinc content varied from 5-36 wt.-%) sliding against a 100Cr6 countersurface showed that the zinc concentration has a strong influence on the third body formation, while mechanical properties such as the hardness of the base material are less important. Correlating the tribometer results with the XPS analysis we find that a strong reduction of friction is taking place when a thin zone is forming that is enriched in zinc-oxide and mixed with carbon from the lubricant [2].

[4]

The dry and lubricated experiments of W sliding against WC lead to a different third body.Ex situ analysis for the dry tests reveal the formation of a grain refined layer in the near surface region of the tungsten specimen and an amorphous layer on the WC counterface[3]. These observations indicate that

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Korres,S., and Dienwiebel, M., Design and construction of a novel tribometer with online topography and wear measurement, Rev. Sci. Instrum., (2010) 063904. Feser, T., Stoyanov, P., Mohr, F., and Dienwiebel, M. The running-in mechanisms of binary brass studied by in-situ topography measurements, submitted Stoyanov, P., Romero, P.A., Järvi T.T., Pastewka L., Scherge M., Stemmer P., Fischer A., Dienwiebel M., Moseler M., “Experimental and numerical atomistic investigation of the third body formation process in dry tungsten/tungsten-carbide tribo couples”, Tribology Letters (2012) online first. Stoyanov, P., Romero P.A., Järvi T.T., Scherge M., Stemmer P., Fischer A., Dienwiebel M., Moseler M.,“Interfacial processes of metallic contacts under dry and lubricated conditions”, (in preparation)

40th Leeds-Lyon Symposium on Tribology & Tribochemistry Forum 2013 September 4-6, 2013, Lyon, France

Effect of Hertzian Contact Pressure on Shear Stress Distribution of EHL Oil Films T. Mawatari1*, A. Nakajima1, B. Zhang1, N. Ohno1, M. Kaneta2 1)

2)

Department of Mechanical Engineering, Saga University, 1 Honjo-machi, Saga, Japan. Faculty of Mechanical Engineering, Brno University of Technology, Tecknicka 2896/2, 616 69 Brno, Czech Republic. *

Corresponding author for [email protected]

1. Introduction

100

10

IR (isoviscous rigid)

5

PH=0.6GPa PH=1.5GPa

PH= 0.8GPa

viscoelastic solid

viscous fluid αPav=13

1 1

-0.15 τx/PH

5

τx/PH

elasticplastic solid αPav=25

10 αPav

-0.10 -0.05

(a)PH=0.6GPa, Y=0 t0=353K 0.5% Solid B 1.0%

50

100

-0.10 -0.05

1.2

:Σ=4.0% P,Σ=4.0%

0.1%

-1.0

-0.5

(b)PH=1.5GPa, Y=0 t0=353K Solid B 0.3% 1.0% 0.5%

0 -1.5

-1.0

0

0.8 0.4

0.3%

0 -1.5 -0.15

Fig.2

PE (piezoviscous elastic)

Lubrication regime diagram for Ke=1.4

Fig.1

2. Procedure of numerical analysis Fig. 1 shows the lubrication regime diagram for the elliptical parameter Ke=1.4. In the figure, G, U, α and Pav show the dimensionless material parameter, the dimensionless speed parameter, the pressure viscosity coefficient and the average Hertzian pressure. When an automobile CVT traction oil corresponding to ISO VG 32 (kinetic viscosity ν: 32.2 mm2/s at 313 K, α: 31.2 GPa-1 at 313 K, specific gravity 288/ 277 K: 0.962) is used, all analytical conditions are included in the piezo-viscous elastic (PE) region. However, the behaviour of EHL oil films varies depending on the parameter of αPav. Namely, when the maximum Hertzian pressure PH is 0.6 GPa or 0.8 GPa, αPav becomes less than 13. Thus, the EHL oil films behave as the viscous fluid. In the case of PH=1.5 GPa, αPav shows the value between 13 and 25, and so the behaviour of EHL oil films becomes the visco-elastic solid. A non-Newtonian thermal EHL analysis was carried out in the same contact condition as a pair of steel flat disk with steel roller1). The disk diameter and the roller radius Rx in rolling direction are 102 mm and 10.32 mm. The elliptical parameter Ke is 1.4. Regarding the governing equations and the material properties, those used in the previous study1) were applied, and in accordance with the identical calculating procedures with before, the numerical calculations were performed.

PR (piezoviscous rigid)

Ellipticity parameter Ke=1.4 Traction oil (VG32) t0=353K

0.5

1.0

0 1.5 1.2

:Σ=4.0% :P,Σ=4.0% 0.2% 0.1%

-0.5 0 0.5 1.0 X direction, X=x/b

P=p/PH

GU1/4

50

P=p/PH

In the present investigation, the maximum Hertzian pressure PH for the thermal elastohydrodynamic lubrication (EHL) analysis was chosen by the lubrication regime diagram for the elliptical parameter Ke=1.4. Each of the pressure is 0.6 GPa, 0.8 GPa or 1.5 GPa. The inlet oil temperature t0 and the entrainment velocity ue were fixed at 353 K and 10 m/s. As the lubricating oil properties, the values of an automobile CVT traction oil were used. Under the above analytical conditions, the same non-Newtonian thermal EHL analysis as the previous investigation1) was performed at the slide roll ratio Σ of 4 % or less. Based on the calculating results, the relation between the Hertzian contact pressure and the shear stress distribution of EHL oil films was discussed.

0.8 0.4

0 1.5

Shear stress τx/PH and pressure P distributions -6

9.77×10 . U and G are 3.53×10-11 and 4.11×103. Fig.2 shows the dimensionless shear stress τx/PH distributions on the central cross section of motion direction. The shear stress τx is the rolling direction component on the slow side solid surface. In the figure, the dimensionless pressure P=p/PH distributions are also indicated. Where, p is the fluid pressure. The shear stress varies with an increase in the slide roll ratio Σ. In the case of PH =0.6 GPa, the shear stress varies on the small region compared with the fluid pressure. On the other hand, the changes in the shear stress at PH=1.5 GPa occurs on almost the same area to the fluid pressure. The velocity distribution of oil films had the close relation to the occurrence region of the shear stress varying in accordance to the Hertzian pressure. 4. References

3. Results and discussion

[1]

In the analytical condition, the dimensionless load parameter W increases with an increase in the Hertzian pressure, and the values become 6.25×10-7, 1.48×10-6 and

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Mawatari, T. and Nakajima, A., “Shear Stress Analysis of EHL Oil Films based on Thermal EHL Theory - In the case of Elliptical Contact Condition-”, Tribol. Online, 4 (3), 2009, 70-73.

40th Leeds-Lyon Symposium on Tribology & Tribochemistry Forum 2013 September 4-6, 2013, Lyon, France

Transient effects and associated time scales in thermal elasto-hydrodynamic line contacts J. Raisin1,2 , N. Fillot1,* , D. Dureisseix1, P. Vergne1 and V. Lacour2 1)

Laboratoire de Mécanique des Contacts et des Structures, INSA de Lyon, F69621 Villeurbanne Cedex, France. 2) Total Supply Marketing - SDR, Centre de Recherche de Solaize, BP 22, 69360 Solaize, France. *

Corresponding author for [email protected]

1. Abstract

SRR = 0,4 SRR = 2 SRR = 3,6

200

Ahc []

During their life cycle, complex tribological systems such as gears and cam-followers are subjected to extremely severe operating constraints. Those invariably involve substantial shear rates, pressures and temperatures within the lubricant, in addition to dynamic applied conditions of load, speeds and conjunction geometry [1]. In recent years, the use of transient TEHD models is progressively becoming a standard for the simulation of gears and cam-follower systems. New advances focus on topics such as roughness, starvation, boundary lubrication, etc. Surprisingly, a clear understanding of the onset and magnitude of the transient effects in TEHD configurations is still lacking. The present study aims at addressing this point by providing a comprehensive numerical analysis of the transient phenomena occurring within the conjunction, their respective influence (depending on the operating conditions and material parameters), and their associated time scales. As a prerequisite, the system of equations, boundary conditions and numerical scheme used in the model are described. In addition, developments to solve transient fully-flooded TEHD problems are detailed, on the basis of a previous work [2] dedicated to the study of steady state cases. Then, the phenomena at the origin of transient effects in a TEHD contact are reviewed along with their characteristic time. In this context, a particular focus is placed on the thermal problem. The complexity in finding a relevant thermal characteristic time is illustrated by the influence of the slide-to-roll ratio (SRR) on the contact performance (film thickness and friction) [3]. The dependency of the dominant heat transfer mode on the SRR is showed. A distinction between low sliding, pure sliding and high sliding conditions is made. Each configuration is thoroughly analyzed, leading to the formulation of new thermal characteristic times. Finally, in order to determine the onset of transient effects, time-dependent TEHD computations are performed. A reference configuration consisting of two contacting cylinders subjected to a sinusoidal load variation (of amplitude Aw and period tw) is used. Transient evolutions of the central film thickness and friction coefficient are compared to quasi-steady solutions for the three different SRR cases and varying tw. For this purpose, characteristic variables of a periodic TEHD problem, namely the mean value (hc m)

400

0

-200 1E-3

0,01

0,1

1

10

100

/wt/tw[]

Fig. 1: Influence of the transient effects on the variation of the normalized average friction coefficient ΔAhc as a function of the load fluctuation frequency 1/tw. In abscissa, the latter is normalized by the dominant physical time tφ identified for each SRR. and amplitude (Ahc) of the central film thickness and the mean value of the friction coefficient (Cfm), are extracted from each computation. Those are, in turn, used to create a set of normalized variables (Δhc m, ΔAhc and ΔCfm) allowing to calculate deviations induced by the transient effects. Results, as the example plotted on Fig.1, show that the onset of transient effects of the different configurations can be matched if related to their dominant physical characteristic time tφ. A parametric study on the operating conditions (load, entrainment velocity, amplitude of fluctuation) and material properties further validates this conclusion.

2. References [1]

[2]

[3]

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D. Dowson, P. Ehret, Past, present and future studies in elastohydrodynamics, Proceedings of the Institution of Mechanical Engineers, Part J: Journal of Engineering Tribology 213 (5) (1999) 317-333. W. Habchi, D. Eyheramendy, P. Vergne, G.E. Morales-Espejel, "A Full-System Approach of the Elastohydrodynamic Line/Point Contact Problem", ASME Journal of Tribology 130 (2) (2008) 021501-021510. V. Bruyere, N. Fillot, G. Morales-Espejel, P. Vergne, Computational fluid dynamics and full elasticity model for sliding line thermal elastohydrodynamiccontacts, Tribology International 46 (1) (2012) 3-13.

40th Leeds-Lyon Symposium on Tribology &TribochemistryForum 2013 September 4-6, 2013, Lyon, France

Reduced Finite Element Elastohydrodynamic Lubrication Model: Circular Contacts W. Habchi* Lebanese American University, Department of Industrial and Mechanical Engineering, Byblos, Lebanon. *

Corresponding author:[email protected]

Fig. 1: Three-dimensional pressure (left) and film thickness (right) profiles for a typical EHL contact (M=200, L=20) obtained using the reduced finite element model

1. Introduction This paper presents a reduced finite element model for circular elastohydrodynamic lubricated (EHL) contacts. This model combines fast convergence rates with reduced memory requirements and negligible model reduction errors compared to the full model which makes it an attractive tool for EHL contact performance prediction.

fully-coupled framework using a damped-Newton procedure allowing fast convergence rates for the global solution. The free boundary arising at the exit of the contact is handled by means of a penalty method. Fig. 1 shows typical pressure and film thickness profiles for a circular contact (M=200, L=20) obtained using the reduced model. The elastic deformation of the contacting solids is also obtained using less than 30 degrees of freedom allowing a significant reduction in cpu time and memory requirements compared to the full model.

2. Methodology 3. Conclusion The reduced EHL line contact model was developed and validated in a previous work [1] [2] where it was shown that the elastic deformation of the contacting solids can be obtained using less than 30 degrees of freedom. This lead to a significant reduction in the size of the matrix system to solve leading to reduced memory usage and computational times. In fact, cpu times for the reduced line contact model were shown to be an order of magnitude smaller than for the full model. In addition, model reduction errors of the order of only 1‰ were obtained for both central and minimum film thicknesses. In this work, the model order reduction technique developed in [1] and [2] is extended to the case of circular contacts. It consists in defining the elastic deformation of the solid components as a linear combination of carefully selected and pre-computed EHL deformations called “basis functions”. The model is based on a finite element discretization of the EHL equations: Reynolds, linear elasticity and load balance. All equations are solved simultaneously in a

A reduced finite element fully-coupled model for the solution of EHL circular contacts is developed. Compared to the full model, it offers an order of magnitude reduction in cpu times with negligible model reduction errors. In addition, memory requirements are significantly reduced as the size of the obtained matrix system to solve at every iteration is considerably smaller. 4. References [1]

[2]

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Habchi W. and Issa J. - Model Order Reduction Techniques for the Solution of EHL Problems, Proceedings of the 38th Leeds- Lyon Symposium on Tribology, Lyon, 2011. Habchi W. and Issa J. – Fast and Reduced Full-System Finite Element Solution of Elastohydrodynamic Lubrication Problems: Line Contacts, Advances in Engineering Software, 2013, vol. 56, pp. 51-62.

40th Leeds-Lyon Symposium on Tribology & Tribochemistry Forum 2013 September 4-6, 2013, Lyon, France

Model order reduction on stationary and dynamical isothermal Newtonian EHD contacts D. Maier2*, C. Hager2, H. Hetzler1, N. Fillot3, P. Vergne3, D. Dureisseix3, W. Seemann1 1)

Institut für Technische Mechanik, Karlsruher Insitut für Technology, 76131 Karlsruhe, Germany. 2) Robert Bosch GmbH, 70049 Gerlingen-Schillerhöhe, Germany. 3) Université de Lyon, INSA-Lyon, LaMCoS, CNRS, UMR5259, F-69621 Villeurbanne Cedex, France. *

Corresponding author for [email protected]

Abstract We are introducing a method to decrease the calculation time of EHD contacts. The method is based on model order reduction (MOR) techniques [1] and will be applied to a stationary and dynamical isothermal Newtonian EHD contact. The contact problem is arranged as one full system of equations [2] – including Reynolds equation with cavitation condition, elasticity equation and force balance – and solved directly. The full system is solved iteratively by a Newton method with an active set procedure accounting for the unilateral constraints related to the chosen cavitation model. The reduction procedure is executed not only on the linear part representing the elasticity equation of the EHD contact problem [3] but also on the strongly nonlinear and parametric part given by the Reynolds equation. To cope with the cavitation condition within the reduced system, the cavitational area is separated from the computational area and the boundary between those two areas is adapted iteratively. Furthermore the costs of constructing the reduced system are cut by approximating the reduced system function and its Jacobian using only a few distinguished nodes [4]. We will investigate accuracy and efficiency of the partially reduced system (only linear part), the fully reduced system and the fully reduced system with system approximation (SA) compared to the full system.

Table 1 Comparison of central film thickness for a point contact problem (M=200, L=10) with a density model based on Dowson and Higginson and the Roelands viscosity model Model Venner and Lubrecht [5] Habchi et al. [2] current model (full) current model (reduced) current model (reduced + SA)

References [1] [2]

[3]

dimensionless pressure

[4] 1

reference MOR

[5]

0 -1 0 1 dimensionless coordinate

Fig.1

Hc 0.08144 0.08222 0.082305 0.082308 0.082338

MOR approximation of pressure for a line contact problem

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Antoulas, A. C., “Approximation of large-scale dynamical systems,” Philadelphia: SIAM; 2005. Habchi, W., Eyheramendy, P., Vergne, P. and Morales-Espejel, G., “A Full-System Approach of the Elastohydrodynamic Line/Point Contact Problem,” ASME J. of Tribology, 130, 2008, 021501 Habchi, W. and Issa, J., “Fast and reduced full-system finite element solution of elastohydrodynamic lubrication problems: Line contacts,” Advances in Engineering Software 56, 2013, 51-62. Carlberg, K., Bou-Mosleh, C. and Farhat, C., “Efficient Nonlinear Model Reduction via a Least-Squares Petrov-Galerkin Projection and Compressive Tensor Approximations,” Int. J. Numer. Meth. Engng, 86, 2011, 155-181. Venner, C.H. and Lubrecht, A.A., “Multilevel Methods in Lubrication,” Amsterdam: Elsevier (Tribology Series Vol. 37); 2000.

40th Leeds-Lyon Symposium on Tribology & Tribochemistry Forum 201 3 September 4-6, 2013, Lyon, France

Influence of Surface Roughness on the Fretting-Corrosion Regimes and Characteristics of Cemented Femoral Stems Michael Bryant1)*, Richard Farrar2) , Robert Freeman2), Ken Brumitt2) and Anne Neville1) 1)

Institute of Engineering Thermofluids, Surfaces and Interfaces, School of Mechanical Engineering, University of Leeds. United Kingdom. 2) DePuy International, Leeds. United Kingdom * Corresponding author: [email protected]

1. Introduction Metal on Metal Total Hip Replacements (MoM THR) regained popularity over two decades ago as an effective method of treating degenerative hip diseases. However recent clinical studies have demonstrated unacceptably high revisions rates of MoM THR due to fretting-corrosion of the cemented portions of the femoral component due to the release in toxic metal ions [1;2]. In order to optimize the design at this interface a number of different mechanical surface treatments are employed depending of the design philosophy of the femoral stem. Studies have demonstrated that surfaces with an increased surface roughness exhibited a stronger mechanical interlocking with the bone cemented due to the interdigitation of the bone cement within asperities of the surface. In contrast, the Exeter polished femoral stem also has over 20 years of clinical data supporting its design philosophy. This study investigates the role surface roughness has on the initiation, propagation and fretting regimes of cemented femoral stems 2.

cement and metallic femoral stem to facilitate measurement of the relative displacement between the two components. 3.

Results

Upon the application of cyclic loading a shift in the negative direction in OCP and increase in fretting-corrosion current was seen indicating depassivation of the metallic surface and increase in metal ion release. Polished femoral stems where seen to exhbit increased fretting-corrosion currents (Figure 1). Different fretting regimes where seen to exist at the interface (Figure 2). An increase in relative displacment was seen for the polished surfaces (≈12µm) compared to the roughened surfaces (≈3µm).

Test Method

Low carbon CoCrMo Ultima TPS™ (DePuy International, Leeds. UK) collarless polished femoral stems (n=3) were utilized in this study. Each femoral stem went through a forging process and were either mechanically polished (Ra ≈ 0.05µm) or subjected to an aqueous bead blast (Ra ≈ 0.8µm). Surface roughness profiles of the polished and blasted surfaces were obtained using a Taylor-Hobson TalySurf CCI interferometer. A test method, facilitating in-situ corrosion measurements, was developed and conducted in part reference to ISO 7206-4 to evaluate fretting-corrosion mechanisms at the stem-cement interfaces. Each stem-cement component was immersed in 0.9% NaCl at 37±1ºC and subjected to cyclic load between 300N to 2300N at 1Hz for 500,000. Intermittent Open Circuit Potential (OCP) and Linear Polarization Resistance (LPR) measurements were taken every 10hrs in order to observe the role surface roughness has on the fretting-corrosion currents from the stem-cement interface. A novel transducer arrangement was also developed in an attempt to quantify the fretting regimes at the stem-cement interface. A linear variable differential transformer has applied to the PMMA bone

Figure 1 – Fretting corrosion currents obtained from LPR data for roughened and polished femoral stems

a

b

Figure 2 – Load vs displacments for a) polished and b) roughened femoral stems References

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[1]

S.Donell, C.Darrah, J.Nolan, J.Wimhurst, A.Toms, T.Barker, et al. Early failure of the Ultima metal – on – metal total hip replacement in the presence of normal plain radiographs. Journal of bone and joint surgery [Br] 2010;92(B):1501-8.

[2]

B.Bolland DC, D.Langton, J.Millington, N.Arden, J.Latham. High Failure rates with a large-diameter hybrid metal-on-metal total hip replacement. Journal of Bone and Joint Surgery [Br] 2011;93(B):608-15.

Influence of surface morphology on mechanical properties of polyethylene. Tribological consequences in a biomimetic environment. M. Popa1,3, N. Wang1,2, R. Diehl2, D. Portinha1,4, J.P. Rieu1,2 , A-M Trunfio-Sfarghiu1,3, Y. Berthier1,3 1

2

Université de Lyon, F-69000, France Université Claude Bernard Lyon-1, Laboratoire PMCN, CNRS, UMR5586 ;F-69622 Villeurbanne Cedex, France 3 CNRS INSA-Lyon ,LaMCoS UMR5259, F-69621 Villeurbanne Cedex, France 4 CNRS INSA-Lyon , IMP UMR5223, F-69621 Villeurbanne Cedex, France

1. Abstract It is known that wearing of the polyethylene part of implants is the primary cause of premature failure of total joint replacements [1]. In this study, using atomic force microscopy technique and tribological methods, we have investigated the influence of polyethylene surface morphology on mechanical properties, wear and friction. 2. Introduction The only known treatment for severe osteoarticular diseases is the replacement of the joint surface with an orthopedic prosthesis. However, the lifespan of these implants is limited at approximately 10 years due to the wearing of polyethylene part. The final goal of our study is to improve the properties of polyethylene by grafting biological molecules on the surface of the material. In order to reach this goal we have initiated a study to determine how different types of morphology influence the mechanical and bio-tribological properties of polyethylene. 3. Materials and methods For our study, we have used samples of ultra high weigh molecular polyethylene with four different types of surfaces obtained by different types of polishing (samples A,B and C) and one with a high-speed turning machine (sample D). The friction coefficient is measured using a homemade bio-tribometer that allows in situ visualization of the contact between the flat surface of the sample and a plane-convex surface of a glass. The tests last 540 min (2027 cycles) using a TRIS-buffered saline solution as lubricant. Nanoindentation was applied to test the mechanical properties of the material using AFM technique. Mechanical properties such as Young modulus are used initially, to establish if it will interfere with friction tests. Further, in our study, the elastic properties will be used to determine influence of chemical treatments applied to samples.

The four types of topographies with their characteristics are shown in table 1. Table 1. Type of Profilometer Friction coefficient topography Ra [μm] A 0.43 0.045±0.0008 B 0.25 0.035±0.0004 C 0.55 0.040±0.0003 D 0.52 0.019±0.0004 As we can see in table 1, the value for Ra is similar for type A, C and D, however the morphology is different for each one of the samples. Thus, type A and C surfaces are characterized by roughness picks that are flattened for type C and more sharp for type A, type D presents concentric stripes, and type B is characterized by the so called “third body platelets” morphology. Each type of surface structure sets the velocity accommodation mode that explains the value of friction coefficient. For example, type D has the lowest value of friction coefficient due to the regularity and the form of stripes, which allows that during friction, peaks are drawn until particles are detached and enter between peaks forming a blend with the TRIS solution (Fig1.(b)). These conclusions were made based on different test realized on chemical treated polyethylene surface.

Fig. 1(a) Variation of friction coefficient with time ; (b)sectional view of the surface of sample D

4. Results and discussion The measures for elastic modulus show no difference for the polished types of samples, reaching a value of approximately 3 GPa, thus we were able to separate this parameter for the friction test that will depend only on the surface characteristics.

6. References [1] A. Buford et al, “Review of wear mechanisms in hip implants” Materials & Design volume25, 2004, 385-393

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40th Leeds-Lyon Symposium on Tribology &TribochemistryForum 2013 September 4-6, 2013, Lyon, France

Effect of mental sweating on fingertip friction K. Mizuhara1*, H. Hatano2,S.Ozaki1, T. Washio3 1)

Department of Mechanical Engineering, Tokyo Denki University, 5 Senju-Asahi-cho, Adachi-ku, Tokyo, Japan 2) Kits Corporation, Nakase 1-10-1, Mihama-ku, Chiba, Chiba, Japan 3) Surgical Assist Technology Group, AIST, Namiki 1-2-1, Tsukuba, Ibaraki, Japan *

Corresponding author for [email protected]

1. Introduction The usability of touch pad is inferior to the other device such as mouse [1]. One of the authors found that the usability of the touchpad is closely related to the frictional coefficient. The higher the friction is the lower the usability [2]. The factors affecting the friction most are the surface roughness and difficulty of the task. The mechanism with which the task difficulty affected is the cautiousness required for difficult tasks and it is suggested that the mental sweating might be the other mechanism. The aim of this paper is to investigate the effect of mental sweating on fingertipfriction. 2. Experimental Friction test were conducted using the index finger touching the touch pad, which moved in traverse direction. To stimulate the sweating, stresses were applied by unpleasant sound (90dB, 0.5sec), gripping300N grip trainer for 10 seconds by the other hand and a mathematicaltask for 10min.The moisture level of the fingertip was monitored by the MoistSense intermittently.

coefficients show rather common load dependence however the each individualresponded to the stress differently. The tendency of increasing load by stress was not relevant for the mathematical task. Concerning the moisture level at the fingertip, increased moisture level was often detectable(10-20% in reading) for sound stress and the mathematical task, but not always.Weak correlation was found over moisture level of 50, [4] for the mathematical task.However it was difficult to find the general trend reported before. This could be attributed to the occlusion time [6] necessary for moisture level to affect the friction. Also, the moisture level tended to decreasewith times of stimulation for sound and duration over 6 min for the mathematical task.Subjects might haveaccustomed to these stresses easily. Further discussions including the effect ofsurface roughness or moving direction will be made.

3. Results and discussions Figure 1 shows an example of the relation between the friction coefficients on smooth plastic surfaceafterdifferent stresses. At the same load range the friction are higher for stressed conditions. However for subjects who shown relatively low friction were not affected by the stress. It was found that thegripping or sound stress increased the normal load, which was consistent with the human behavior undernegative affect [3]. Figure 2 shows an example of friction during mathematical task from 3 subjects. The friction

Figure 2. Correlation between normal load and friction during the mathematical task 4. Summary It is confirmed that the mental stress affectsthe friction at the fingertip. Sound and gripping stimulation tend to increase the normal load but the mathematical task. The effect of sweatingseemed to depend on the initial moisture level. 5. References [1] [2] [3] [4]

Figure 1.Correlation between normal load and friction, before and after stimulations.

[5]

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Accot J, Zhai S, CHI 99 Papers ,1999, 295-302. Mizuhara K, Washio T, Ishii T, Proc. WTC 2009 Kyoto, 2009, 190 Mentis HM, Gay GK, Proc. 4th IEEE Int. Conf. on Multimodal Interfaces,2002, 406-410 Tomlinson SE, Lewis R, Liu X, Texier C, Carre MJ, Tribology Letters (2011) 41:283-294 PasumartySM, Johnson SA, Watson SA, AdamsMJ,TribolLett (2011) 44:117-137

40th Leeds-Lyon Symposium on Tribology & TribochemistryForum 2013 September 4-6, 2013, Lyon, France

An Evaluation of the Needed Dimples Spacing and Roughness of Hip Joint Prosthesis Articulating Surfaces at Partially Regular Surface Texture V. Pakhaliuk*, M. Kalinin , Y. Pashkov, O. Poliakov, Y. Ivanov Interdepartmental Laboratory of Biomechanics, Sevastopol National Technical University, 99053 Sevastopol, Ukraine. *

Corresponding author for [email protected]

1. Introduction

3. Results and discussions

Currently in the field of technology of processing of a surface with formation of partially regular surface texture is reached essential progress. Creation of artificial lubricant pockets (dimples), as a rule, prevents the bonding of articulated surfaces of tribo-pair, promotes removal of products of wear process into dimples from a contact place, feeds the frictional contact by portion of lubricant in process of its operation, that all essentially improve tribological properties. The objective of this work is to regulate the dimples spacing of partially regular surface texture on a ball head of hip joint prosthesis depending on the nominal contact pressure and to define a class of a roughness to which it is necessary to process a ball head surface for metal/metal and metal/polymer friction pairs.

In a range of nominal contact pressure 2…20 MPa the condition of "film starvation» absence is the defining one that gives the optimum relationship S /( S  d ) = 1.01…7.0. The coefficient of friction at this relationship does not reach the minimum and is not therefore the defining criterion. To the higher surface roughness class it is necessary to process a ball head surface: for the metal/metal tribo-pair in comparison with the same of the metal/UHMWPE, also in the case of a spherical waviness in comparison with cylindrical one, and at increase in magnitude of ratio S /( S  d ) and of a nominal contact pressure, but the latest factor provides a weak influence. There is the interesting result which shows that considerable variability of initial parameters at the definition of ratio S /( S  d ) leads to the maximum change of a surface roughness class no more than in one unit.

2. Materials and methods The problem of optimisation of a surface texture from a position of the molecular mechanical theory of a dry and boundary friction and a hypothesis of "film starvation», developed by Kragelsky [1], taking into account criterion of a minimum of coefficient of friction, is considered. According to a hypothesis of "film starvation» on two contacting surfaces in a sliding direction the protective layers of an intermediate layer simultaneously are formed and destroyed and probability of contact through an lubricant layer increases owing to an optimum relationship of speeds of destruction and restoration of a boundary film, and also a relationship S /( S  d ) is an average distance between dimples S and their average extent S  d , where d is a size of dimple on a surface. The contacting prosthesis elements (a ball head and an insert) have the area of interaction where the contact process is also influenced by a surface waviness.The nominal contact pressure depends on contour pressure, therefore at definition of contour pressure the two forms of a wave – cylindrical and spherical were considered and comparison of their influence was performed. The actual nominal pressure was defined by a simulation method with use of software ANSYS. The metal/metal (CoCrMo alloy) and the metal/UHMWPE (ultra-high-molacular-weight polyethylene GUR 1020) friction pairs were simulated. Taking into account the noted above criteria the roughness characteristic of a ball head surface  was defined by which then the main roughness parameter R a – the mean arithmetic deviation of the profile, was obtained.

4. Conclusion The obtained results allow providing the engineering well-founded approach at designing of the spherical joint of hip prosthesis with partially regular surface texture, and also other joints which structure includes the spherical joint. Besides, it allows generating initial data at the formulation and solution of the further problem by the definition of wear rate in the joint to be designed. 5. Acknowledgements The work is supported by grants from the Ministry of Education and Science of Ukraine [0111U003330, 0113U001251]. 6. References [1]

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Kragelsky, I.V., Dobychin, M.N., and Kombalov, V.S., “Friction and Wear”. New York: Pergamon Press; 1982.

40th Leeds-Lyon Symposium on Tribology & Tribochemistry Forum 2013 September 4-6, 2013, Lyon, France

Nanofriction properties of graphite tribofilms: influence of the tip/sample interface Georges Minatchy1*, Laurence Romana1, Philippe Bilas1, Nadiège Nomede Martyr2, Philippe Thomas1, Jean-Louis. Mansot1,3 1)

Groupe de Technologie des Surfaces et Interfaces (GTSI EA 2432) Université des Antilles et de la Guyane, Campus de Fouillole, BP 250, 97 157 Pointe à Pitre, Guadeloupe, F.W.I 2) Laboratoire d'Analyses par Réactions Nucléaires LARN, Faculté Universitaire de Notre Dame de la Paix FUNDP Rue de Bruxelles 61, B-5000 Namur, Belgique 3) Centre Commun de Caractérisation des Matériaux des Antilles et de la Guyane (C3MAG), Université des Antilles et de la Guyane, Campus de Fouillole, BP250, 97 157 Pointe à Pitre, Guadeloupe, F.W.I *

Corresponding author for [email protected]

Previous study has shown that friction properties of lamellar compounds are significantly improved in the presence of liquid [1]. In the present work, the nanofriction properties of the macrotribofilms formed from UF4 powder in the presence of liquid, are investigated at the nanoscale. For this purpose the tribofilms are characterized using an atomic force microscope coupled with a friction force microscope. Three different AFM tips (Si, CrAu & Si3N4) are used in order to study the influence of the friction interfaces on the nanotribological properties. AFM images recorded on the tribofilms reveal a heterogeneous surface constituted of smooth platelets surrounded by granular areas as shown in Figure 1.

Classical contact mechanic theories have been used to fit the experimental curves reported in figure 2. Data recorded on granular areas are well fitted by DMT [2] theory whereas on platelet areas the curves are better fitted using the JKR one [3]. The shear stress values deduced from these procedures are reported in table 1. Si CrAu Si3N4 (MPa) (MPa) (MPa) Platelet area 4.4±1.4 3.2±0.8 4.9.± 2 Granular area 62±9 58±5 69±10 Table 1: Shear stress values deduced from JKR (platelet zone) and DMT (granular area) contact theories. The shear stress values calculated on the platelets are around 10 times lower than the ones measured on the granular area revealing their good friction properties. Note that the friction forces measured on the platelets are of the same order of magnitude than the ones measured on HOPG bulk indicating that the platelets are probably HOPG particles oriented with their c axis perpendicular to the surface.

Figure 1: AFM deflection image recorded on UF4 tribofilm. The friction forces as a function of the total normal load using the 3 AFM tips are reported in figure 2. Each data point of a curve is average lateral force obtained from 8 measurements on different areas and the error bars are the associated standard deviation.

The fact that the nature of the tip has no influence on the friction behavior, suggests that sliding occurs between two basal graphene planes. This conclusion is strongly supported by SEM post-analysis of the tips which show graphite flakes bonded to the tips by electrostatic force in the regions corresponding to the contact area.

1. References 25

UF4/Si3N4 UF4/Cr-Au UF4/Si

20

[1]

FF (nN)

15

[2] UF4/Si3N4 UF4/Cr-Au UF4/Si

10

5

[3] 0 0

20

40

60

80

100

120

FN+Fad (nN)

Figure 2: Friction force as a function of total normal load recorded on UF4 tribofilms using the three types of AFM tips.

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Nomede-Martyr N.; Ph-D thesis, Etude de l’influence d’un liquide organique sur les propriétiés tribologiques de particules minérales, Université des Antilles et de la Guyane (2010) Derjaguin, B.V., Muller, V.M. and Toporov, Y.P., Effect of contact deformations on the adhesion of particles, J. Colloid Interface Sci., 53, 314-326, 1975 Johnson, K.L., Kendall, K., Roberts, A.D., Surface energy and the contact of elastic solids, Proc. R. Soc. London, A324, 301-313, 1971

40th Leeds-Lyon Symposium on Tribology & Tribochemistry Forum 2013 September 4-6, 2013, Lyon, France

Experimental and theoretical investigations of friction properties of graphite intercalated compounds. J.L.Mansot1,2*, K. Delbé3, P. Baranek4, P. Thomas1, F. Boucher5, F. Vangelisti6, D. Billaud6. 1)

Groupe de Technologie des Surfaces et Interfaces (GTSI EA 2432) Université des Antilles et de la Guyane, Centre Commun de Caractérisation des Matériaux des Antilles et de la Guyane (C3MAG), Université des Antilles et de la Guyane Campus de Fouillole, BP 250 97157Pointe à Pitre, Guadeloupe, F.W.I 3) LaboratoireGénie de Production, EA 1905, ÉcoleNationaled’Ingénieurs de Tarbes, BP 1629, 65016, TarbesCédex 4) EDF - R&D, Department MMC and MAI, Avenue des Renardières, Les Renardières, 77818 Moret sur Loing Cedex 5) Laboratoire de Chimie des Solides, Institut des Matériaux Jean Rouxel, UMR 6502 CNRS-Université de Nantes, 2 rue de la Houssinière, BP 32229, 44322, NantesCédex 3, France 6) Institut Jean Lamour, UMR CNRS 7555, Faculté des Sciences, Université Henri Poincaré Nancy I, BP 239, 54506 Vandoeuvre-Lès-NancyCédex, France * Corresponding [email protected] 2)

1. Introduction It is classically admitted that the goodfriction properties of lamellar compounds are strongly related to their anisotropic structure and especially to the existence of weak interlayer interactions through the van der Waals gap separating the basal layers [1]. As it is also known, the presence of the van der Waals gap in the structure of lamellar compounds will allow lot of chemical species to be intercalated in the structure leading both to the expansion of structure parameters and inter layer interactions modifications [2]. The present work is concerned with the experimental and theoretical study of friction propertiesof Graphite Intercalated Compounds (GICs) in order to better understand thetribologiclamellar compounds. In order to modulate the interlayer interactions, two types of intercalated species were used, electrophylic species (AlCl3, FeCl3, SbCl5) and nucleophilic species (Li, K, Rb). 2. Experimental and theoretical method Friction properties were studied using a reciprocal sphere/plane (AISI52100/AISI52100) tribometer under pure argon atmosphere. The electronic properties and interlayer interactions were investigated using ab initio band structure calculations based on DFT theory [3]. 3. Results and discussion Tribologic results collected on the various GICs are presented in figure1.

better intrinsic friction coefficient (measured in the early stage of friction tests) than graphite. Most of the compoundspresents a de-intercalation process during sliding leading to an increase of the friction coefficient as a function of cycles number. The figure 2 presents the evolution of the intrinsic friction coefficient as a function of the calculated interlayer interaction intensities.

Figure 2: Friction coefficient as a function of the calculated interlayer interaction intensities. As expected electrophilic intercalated GICs, which present low intrinsic friction, also present low interlayers interactions (lower than graphite) according to the classical interpretation of tribologic properties of lamellar compounds. The very high interlayer interactions in the case of the nucleophilicGICs associated also with friction coefficient lower than graphite is surprising. It demonstrates that friction properties are not simply related to interlayer interactions but also to other parameters such as the mobility, in the van der Waals gap, of the intercalated species. This last hypothesis is strongly suggested by the friction coefficient increase recorded from Li to Rb ions. 4. References [1] [2]

[3]

Figure 1: Evolution of friction coefficients as a function of cycles number for the two GICs families. As it can be seen, the various GICs compounds present

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Nanolubricants, J.M. Martin and N. Ohmae ed., J. Wiley and Sons, New-York, (2008). Dresselhaus, M.S., Dresselhaus, G., Intercalation compounds of graphite, Advances in Physics, 51, 2002, 1-186. Delbé, K., Mansot, J.-L., Thomas, Ph., Baranek, Ph., Boucher, F., Vangelisti, R., Billaud, D., Contribution to the understanding of tribological properties of graphite intercalation compounds with metal chloride,Tribology Letters, Volume 47, Issue 3, 2012, 367-379.

40th Leeds-Lyon Symposium on Tribology &TribochemistryForum 2013 September 4-6, 2013, Lyon, France

Exfoliation of Graphene from C60 monolayer K. Miura1*, M. Ishikawa1, M.Ichikawa1, N.Sasaki2 2)

1) Department of Physics, Aichi University of Education, Hirosawa, Igayacho, Kariya-shi, Aichi 448-8542, Japan Department of Materials and Life Science, Faculty of Science and Technology, Seikei University, 3-3-1 Kichijoji-Kitamachi, Musashino, Tokyo 180-8633, Japan * Corresponding author: [email protected]

depicts a schematic of the exfoliation experiment.

1. Introduction Detachment and exfoliation experiments areexpected to provide information on the adhesion forces andenergies of solid surfaces in contact with each other.However, it was not easy to scientifically solve exfoliation and fracture, because we could not approach them at the atomic scale.Recently, it has been reported that carbon nanotube arrays with curved entangled tops exhibit a macroscopic adhesive force of approximately 100N/cm2, almost 10 times as large as that of a gecko foot, and a shear force much stronger than the normal adhesion force[1,2]. Wefocus our attention on the elementary processes involved in the exfoliation of a graphene on the C60 monolayer. 2. Experimental setup First, we account for the preparation of a single-layer graphene (SL-graphene) and a graphene tip. Graphene films were prepared by the mechanical exfoliation (repeated peeling) of highly oriented pyrolytic graphite. Figure 1(a) shows an optical microscopy image of a relatively large multilayer graphene (ML-graphene) on top of an oxidized Si wafer that locally includes an SL-graphene.The position of the SL-graphene on the oxidized Si wafer was estimated from the shape of the G’ band of Raman spectroscopy,as shown in Fig. 1(b), because atomic force microscopy (AFM) was not sufficient for identifying the SL-graphene on the oxidized Si wafer. The thickness of the SL-graphene on the oxidized Si wafer was estimated to be approximately 0.8 nm using AFM, corresponding to the height difference between X and Y at the bottom of Fig. 1(c), although the thickness of the SL-graphene on another SL-graphene (or an ML-graphene) was estimated to be approximately 0.3 nm, corresponding to the height difference between Y and Z, because the force between the graphene and the oxidized Si wafer is different from that between graphenes. Here, a glass sphere (diameter: 40 μm) with a two-component epoxy resin adhesive was used to bond the SL- or MLgrapheneson the oxidized Si wafer to the AFM tip. We call this a graphene tip. The junction formed between the AFM tip and the graphene is sufficiently mechanically rigid to measure the elasticity of the SLor ML-graphene during the exfoliation process. Figure 1(d) shows a scanning electron microscopy (SEM) image of the ML-graphene tip. We set the graphene tip on the AFM instrument under ambient conditions and obtained the vertical force-distance curve. Figure 1(e)

Fig. 1 Preparation of single layer (SL-) graphene and graphene tip. (a) Optical microscopy image of relatively large multilayer graphene (ML-graphene) on top of oxidized Si wafer that locally includes SL-graphene. (b)and(c) Raman spectroscopy data and atomic force microscopy (AFM) image of SL-graphene on oxidized Si wafer, respectively. (d)Scanning electron microscopy (SEM) image of graphene tip. (e) Schematic of exfoliation (peeling) experiment. 3. References [1] Qu,L. Dai,L. Stone,M. Xia, Z.and Wang, Z. L.,“Cabon nanotube arrays with strong shear biding-on and easy normal lifting-off”, Science,322, 2008, 238-242. [2] Ishikawa, M.Harada, R.Sasaki,N. and Miura, K., “Adhesion and peeling forces of carbon nanotubes on a substrate”,Phys. Rev. , B 80 ,2009, 193406.

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40th Leeds-Lyon Symposium on Tribology & Tribo hemistry Forum 2013 September 4-6, 2013, Lyon, Fran e

Inuen e of a single asperity on stresses during lubri ated sliding

onta t on DLC- oated system 1,2,3

G. Pagnoux

1

2

3

, S. Fouvry , M. Peigney , B. Delattre , G. Mermaz-Rollet

3

1. LTDS, 36 Avenue Guy de Collongue, 69131 E ully, Fran e; 2. Univ. Paris-Est, Lab. Navier (E ole des Ponts ParisTe h, IFSTTAR, CNRS), F-77455 Marne-la-Vallée, Fran e; 3. PSA Peugeot Citroën, Route de Gisy, 78140 Vélizy, Fran e, georey.pagnouxmpsa. om

1. Introdu tion

Extreme low wear rates of Diamond-Like Carbon (DLC) oatings are one the properties that makes them parti ularly interesting for numerous appli ations, like automotive ones. This property is often observed during hara terisation tests under basi solli itations like fretting, sliding, rolling-sliding, et ... However, tests on am-tappet systems show the oating lifetime an be highly redu ed under spe i oupled onditions, su h as the presen e of an asperity breaking through the lubri ation lm into the onta t area. Experimentally observed, its inuen e on surfa e and subsurfa e stresses has to be quantied to eventually obtain a predi tive model of the oating lifetime. The purpose of this study is to develop a simplied numeri al model onsistent with elasto-hydrodynami lubri ation (EHD) approximations to estimate the stress perturbation due to su h an asperity. 2. Coupled wear me hanisms

Conta t kinemati s of the am-tappet system is a omplex ombinaison of impa t loading, rollingsliding and sliding onta t under lubri ated onditions, resulting in dierent solli itations on the tappet surfa e. Observations on worn oated surfa es revealed six hara teristi fa ies and hightlighted four wear me hanisms. The worst one, relative to oating delamination, was systemati ally found to initiate around ir ular s rat h networks. It is then assumed that those two wear me hanisms are strongly oupled. Cir ular s rat h networks may be

reated either by asperity existing on the initial am surfa e, or by hard parti ules ( oming from a highly

ontaminated lubri ant) in rusted into the am surfa e. 3. Single asperity onta t

Regardless its sour e, it is ne essary to assess the

damage aused by su h a defe t on the oating lifetime. It has been shown that, under pure rolling

onditions, DLC oatings are more sensitive to hard parti ules trapped into the onta t than un oated surfa es [1℄. The numeri al model on whi h the study is based on is however limited to 2D plain strain with no lubri ation and no sliding. Under sliding onditions, observations suggest the damage is similar to the one aused by s rat h tests. The indu ed damage me hanism was highlighted by Holmberg [2℄, using both experimental and numeri al results and fo using on lo al stress elds and rst ra k lo ation. Based on ongoing resear h and following the work of Hannes [3℄, a simplied 3D numeri al model onsistent with EHD lubri ation approximations will be developped, using joint elements with dened ompression and shear behavior to model the lubri ant. It an estimate the load arried by an asperity as well as the indu ed perturbation on surfa e and subsurfa e stress. As a simplied model, it an be run qui kly on multiples ongurations. Analyti al fun tions an then be tted upon spe i variables in order to be used as input datas in a more general iterative pro essus. 6. Referen es

[1℄ F. He et al., "Wear properties of DLC- oated steel rollers running with highly ontaminated lubri ation", Tribology International, 43(5-6), 2010, 990996. [2℄ K. Holmberg et al., "Tribologi al analysis of fra ture onditions in thin surfa e oatings by 3D FEM modelling and stress simulations", Tribology International, 38(11-12), 2006, 1035 1049. [3℄ D. Hannes et al., "Rolling onta t fatigue ra k path predi tion by the asperity point load me hanism", Engineering Fra ture Me hani s, 78(17), 2011, 28482869.

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40th Leeds-Lyon Symposium on Tribology & Tribochemistry Forum 2013 September 4-6, 2013, Lyon, France

Surface Star Defect Tolerance Assessment on finished Silicon Nitride balls in Rolling Contact A.W. Awan1*, M. Hadfield1, B. Thomas1 C. Vieillard2 and R. Cundill2

1)

2)

School of Design Engineering and Computing, Bournemouth University, Poole, Dorset, BH12 5BB, UK SKF Engineering & Research Centre, Kelvinbaan 16, 3439 MT, Postbus 2350, 3430 DT Nieuwegein, the Netherlands *

Corresponding author: [email protected]

Abstract Surface defects are the main limiting factor for the use of silicon nitride in hybrid ball bearings applications. So-called star features are surface defects created during ball lapping/finishing by coarse diamond grit indenting the ball surface. They can offer different morphologies involving cracks, incipient chips and chips or remnant central pit. This experimental studies focus on the performance of silicon nitride rolling elements having different morphologies of star defects in rolling contact with different lubricants. 1. Introduction The main limiting factor of silicon nitride in hybrid rolling element bearing applications is the presence and sensitivity of surface defects with relatively low fracture toughness. Surface defects may be of different forms including star-like cracks, C or ring cracks, inclusions, and missing material. An experimental study [1] confirmed a failure mechanism by spalling due to crack propagation from the existing crack. Lubrication, crack location and orientation within the contact path also play a very important role in the rolling contact fatigue of silicon nitride. Ueda [2] produced theoretical study on the surface cracks caused by artificial indenter. Most recent study [3] conducted on C or ring cracks in silicon nitride modelled subsurface stress field, predicted potential cracks shapes, possible maximum stress intensity factors locations and critical flaw size. Karazewski [4] concluded that crack/defect size and oil additives play an important role in rolling contact fatigue of silicon nitride. Depending on how late in the ball lapping process, a coarse diamond indents the ball surface, the resulting star feature morphology can vary with how much material is further lapped/polished away. With limited stock removal, the resulting star can retain similar damage than Vickers indentation with central dent, radial and lateral cracks or even associated small flakes. In this study, naturally occurring surface star features were tested in rolling contact for highlighting their potential failure mode.

a) b) Fig. 1: Natural star Defects (a) under UV illumination (b) under white light illumination

Rolling contact tests on these star features in different lubricants showed no damage processes or changes with thick oil, while thinner oils and grease lubrication could lead to surface material loss within the confine of the original star extent within few millions overrolling cycles (8 to 30 Millions). These damages were small and did not trigger vibrations increase that would be a sign of rolling function loss at this stage. However, these results indicated that such star feature do present a damaged (weaker) initial shallow zone that quickly develop into a missing material by internal fracture, and subsequent chipping at an early stage of rolling. Thinner lubrication film can contribute to higher contact friction and/or higher surface/near surface stresses acting on the star features and promoting cracking on the weak pre-damaged star zone. Due to the pre-existing shallow weak star zone, crack branching and breaking to the surface lead to the formation of a missing material at the ball surface which is further exposed to rolling contact. 3. Conclusion A mild morphology of naturally occurring stars on Si3N4 balls from ball finishing process, presenting star like radial cracks from usually a central ring were shown prone to develop into missing material by internal fracture over the extent of the star in lubricated rolling contact. Lubrication quality or film thickness can influence this mechanism. The orientation of the pre-existing cracks to the rolling direction may also influence the damage process and severity. 4. References [1]

2. Experimental results Lubricated 4-ball rolling contact tests were conducted on Si3N4 balls with mild morphology of star, Fig.1, presenting the star like crack branches with no or very small associated pits, missing material. The star feature was placed in the rolling contact of the top ball and tested against bottom bearing steel balls, and subjected to rolling contact with medium to high contact pressure but no special care was taken for its orientation to the rolling direction.

[2]

[3]

[4]

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Wang, Y. and Hadfield, M., “Ring crack propagation in silicon nitride under rolling contact”, Wear, 250, 282-292, 2001 Ueda, K., “Contact-Stress Deformation and Fracture in Ceramics”, Japanese Journal of Tribology, Vol. 34, No.2, pp. 123-131, 1989. Levesque, G. and Arakere, N. K., “Critical flaw size in silicon nitride ball bearings”, Tribology Transactions, 53, pp. 511-519, 2010 Karaszewski, W., “The influence of oil additives on spread cracks in silicon nitride”, Tribology International, 41, pp. 889-895, 2008

40th Leeds-Lyon Symposium on Tribology & Tribochemistry Forum 2013 September 4-6, 2013, Lyon, France

Elastic contact between representative rough surfaces V. A. Yastrebov1*, G. Anciaux2, G. Cailletaud1, J.-F. Molinari2 1)

2)

Centre des Matériaux, MINES ParisTech, CNRS UMR 7633, F-91003 Evry, France Laboratoire de Simulation en Mécanique des Solides (LSMS), École polytechnique fédérale de Lausanne (EPFL), CH-1015 Lausanne, Switzerland *

Corresponding author [email protected]

Introduction Under a certain magnification all surfaces are rough. This roughness determines the mechanics of the contact, onset of plasticity, wear, friction and the properties of heat and electricity transfer. An important parameter characterizing the mechanics and physics of the rough contact is the real contact area. We study the evolution of the real contact area under the increasing contact pressure. We compare our results to the existing theoretical models [Bush et al., 1975; Persson, 2001] and deduce a quite general contact evolution law. For that purpose we use a mechanically complete numerical model for elastic contact.

realistic roughness. We demonstrate also that for considered surfaces the evolution of the real contact area is significantly more linear than predicted by asperity based theoretical models. The slope of this evolution for infinitesimal contact is very close to the constant found by [Bush et al., 1975] and is significantly higher than the value predicted by [Persson, 2001]. We suggest a phenomenological contact evolution law valid up to about 40 percent of the relative contact area [Yastrebov et al., 2012].

Methods A realistic roughness is self-affine and the surface heights follow a normal distribution. We use a filtering algorithm in Fourier space [Hu and Tonde, 1992] to generate rough surfaces. To make the study statistically meaningful, 30 surfaces are generated for a given Hurst roughness exponent and two cut-off frequencies in the surface spectra. The highest frequency determines the smallest asperities, which should be well resolved in the mechanical sense for a given discretization of the computational mesh. The lowest frequency in the surface spectrum determines the representativity of the surface, which is responsible for the proximity of the surface's heights distribution to a normal one. To solve the mechanical contact problem (Fig. 1), we use an FFT based boundary element method [Stanley and Kato, 1997] which allows us to compute accurately the contact pressure and the contact area between two semiinfinite elastic solids with periodic roughness. Results and discussions We show that the lowest frequency in the surface spectrum has to be big enough, i.e. the surface should be representative, to obtain the results corresponding to

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Fig. 1. Contact between rough surfaces: bottom – scaled superposition of roughness; top – contact pressure. References Bush, A. W. and Gibson, R. D. and Thomas, T. R., “The elastic contact of a rough surface”, 35, 87-111, 1975. Persson, B. N. J., Theory of rubber friction and contact mechanics, J Chem Phys, 115, 3840-3861, 2001. Hu, Y. Z. and Tonde, K.r, “Simulation of 3-D random rough surface by 2-D digital filter and Fourier analysis”, Int. J. Machine Tools Manuf. 32, 83-90, 1992. Stanley, H. M. and Kato, T., “An FFT-based method for rough surface contact”, J Tribol-T ASME, 119, 481-485, 1997. Yastrebov, V. A., Anciaux, G., Molinari, J.-F., Contact between representative rough surfaces, Phys Rev E, 86, 035601(R), 2012.

40th Leeds-Lyon Symposium on Tribology & Tribochemistry Forum 2013 September 4-6, 2013, Lyon, France

Probing the micromechanics of a multi-contact interface at the onset of frictional sliding A. Prevost1, J. Scheibert2* , G. Debrégeas1 1)

2)

CNRS/UPMC Univ Paris 06, FRE 3231, Laboratoire Jean Perrin LJP, F-75005, Paris, France. Laboratoire de Tribologie et Dynamique des Systèmes, CNRS / Ecole Centrale de Lyon, 69134 Ecully, France. *

Corresponding author: [email protected]

1. Introduction The transition from static to sliding friction is a crucial process in various fields, ranging from contact mechanics, earthquakes dynamics to human/humanoid object grasping. In the classical Amontons-Coulomb’s framework, when two solids are brought in contact under normal load P and subjected to a shear force Q, no relative motion occurs until Q exceeds some threshold value Qs = µsP, where µs is called the static-friction coefficient. However, in most real situations, the transition from static to dynamic friction does not follow this ideal simple scenario. As soon as Q > 0, partial slippage generally sets in owing to the large stress heterogeneity within the contact zone, which depends on the geometry of the objects in contact as well as on the loading conditions. Understanding this incipient sliding regime thus requires to gain access to the interfacial micromechanics within the contact zone.

2. Summary

hypothesis underlying CM's scenario. In particular we will show that, instead of the rigid-plastic behavior assumed in CM's model, the interface obeys an elasto-plastic-like friction law involving a roughness-related length scale. We will discuss this local constitutive law in the light of a recent model derived for homogeneously loaded macroscopic multi-contact interfaces [3].

3. Conclusion Overall, the present study suggests the need to replace the rigid-plastic-like Amontons-Coulomb friction law with an elasto-plastic constitutive friction law in CM-like derivations of the displacement/stress fields, and more generally in any micromechanical analysis of contact mechanics problems. The effective modulus of the elastic part of this constitutive law is i) proportional to the local applied pressure and ii) inversely proportional to the thickness of the rough interfacial layer. The type of measurements developed and validated in this work opens the way for more focused studies in any other contact geometry or loading configurations, for which no explicit model might be available. The time resolution of the measurements being entirely controlled by the frame rate of the imaging system, we anticipate that the very same method could also be used in the fast transient regimes involved in frictional instabilities. 4. References [1]

[2] Fig.1

Sketch of the experimental setup.

[3]

We will discuss the role of surface roughness on the transition between static and kinetic friction, on the example of a flat rough elastomer in contact with a spherical smooth glass surface (fig. 1). Digital Image Correlation is used to monitor the in-plane elastomer deformation as the shear load is increased [1]. An annular slip region is found to progressively invade the contact, in coexistence with a central stick region. The main features of these local measurements are correctly captured by Cattaneo and Mindlin (CM)'s model [2]. However, close comparison reveals significant discrepancies that reflect the oversimplifying

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A. Prevost, J. Scheibert and G. Debrégeas, Probing the micromechanics of a multi-contact interface at the onset of frictional sliding, Eur. Phys. J. E 36, 17 (2013). K.L. Johnson, Contact Mechanics , Cambridge University Press (2003). L. Bureau, C. Caroli and T. Baumberger, Elasticity and onset of frictional dissipation at a non-sliding multi-contact interface, Proc. R. Soc. London 459, 2787 (2003).

Abstract Wear Depth Evaluation During Erosion of X65 Carbon Steel Using RMS Values of Measured Acoustic Emission Signals Jonathan Ukpai*, Richard Barker and Anne Neville Institute of Engineering Thermofluids, Surfaces and Interfaces, School of Mechanical Engineering, University of Leeds, LS2 9JT, UK Corresponding author email: [email protected]

The root mean square (RMS) of acoustic waves emitted during erosion of X65 carbon steel materials under submerged impinging jet at 50 oC has been measured and its values have been correlated with the erosive wear depth calculated from profilometry. An approximate relationship has been established in order to explain the erosive wear behaviour of X65 carbon steel for different flow velocities and sand concentrations which is intended for petroleum pipeline integrity monitoring.

Key Words: Erosion, Acoustic Emission, Wear Depth

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40th Leeds-Lyon Symposium on Tribology & Tribochemistry Forum 2013 September 4-6, 2013, Lyon, France

Sliding Friction by a Liquid Meniscus Bridge between Parallel Plates K. Tanaka1*, K. Iwamoto1

1)

Dept. Of Marine Electronics and Mechanical Engineering, Tokyo Univ. of Marine Science and Technology, 2-1-6, Etchujima, Koto-ku, Tokyo 135-8533, Japan. *

Corresponding author for [email protected]

1. Introduction Frictional, capillary and viscous forces are among the most influencing factors in micro and nano-mechanics. In the presence of liquid film, droplet or condensed water from humid air on a surface, a liquid meniscus bridge can be formed between two bodies. The liquid bridge causes a strong interaction heavily influences the operation of micro/nano devices. A normal component of capillary force is widely studied. Hysteresis in a force-curve detection during approaching and retrieving process of two surfaces is mainly appeared with capillarity. In this study, we focused on the lateral component of capillary forces. A force during sheared process of a liquid bridge between parallel plates was measured. Behavior of contact lines which have an important role on the lateral component of capillary force was also observed.

energy corresponds to a force needed to shear the liquid bridge. Figure 3 shows that some additional factors are necessary to depin the contact line.

2. Experiment A liquid meniscus bridge is formed between parallel plates. The lateral force acts on the plate during sheared process is measured. And the deformation of the meniscus bridge is observed by a CCD camera through a microscope. By using image-processing technique, movements of contact line are tracked. And, change in contact angle can be calculated with an assumption that a radius of curvature is constant. 3. Result and discussion Figure 1 shows a snapshot of a liquid meniscus bridge of 10L water between a gap of 1mm. Asymmetrical shape appears with shear. Fig.2 shows a typical trend of lateral force and change in contact line movement and contact angle at four contact lines. Deformation of the liquid bridge with pinned contact line result in the increase of lateral force. When the lateral force reach a limit, interfacial slip with depinned contact line occurred. To explain these trends, change in interfacial energy during shear is calculated. A derivative of interfacial TL

BL

Fig. 2 Typical trend of lateral force, contact line movement and contact angle

TR

BR

Fig. 1 Snapshot of liquid meniscus bridge between glass plates under shear, dotted edge with “TL” means position of a detected contact line at the Top – Left

Fig. 3 Calculated lateral force with pinned and depinned contact line model

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40th Leeds-Lyon Symposium on Tribology & Tribochemistry Forum 2013 September 4-6, 2013, Lyon, France

Analysis by Scratch Method of Coatings of AISI5115 and M31 Steels Coated with AlTiN and CrN Using PVD Method A. Aytaç1*, U. Malayoğlu2 , H. Sert3 1)

Turkish Military Academy, Ankara, Turkey. Dokuz Eylul University, İzmir, Turkey. 3) University of Turkish Aeronautical Association, Ankara, Turkey. 2)

*

Corresponding author for [email protected]

1. Introduction

2. Material and Method 16MnCr5 (AISI 5115) and 32NiCrMo145 (M31) cementation steels, which have structural function and are extensively used in moving parts of light guns, were taken as the base materials in the experiments. Thermal processes were applied to these parts par and they were coated with AlTiN and CrN using PVD technique (Table 1).

M31

Number of Cathode

CrN

-110

3 Pcs. AlTiN (%66Al+ %33Ti) 3 Pcs. Chrome (Pure)

60

Temperature( °C)

Cathode Current (A)

50

Time (min.)

Basic Voltage (V)

-180

Nitrogen Pressure (Torr)

Coating

Material

AlTiN

8x10–

30

300

60

220

3

6,5x1 0–3

Cross-sections sections of experimental samples were scrutinized with scanning electron microscope (SEM) and coating thicknesses were measured. Besides, after the coating process surface roughness, hardness and elasticity module measurements were made. made Scratch tests were applied to the samples in order to determine the mechanical characteristics, such as breakage, damage and adhesion, of AlTiN and CrN coatings and the results were evaluated.. 3. Results of the Experiments In the experiments, the critical load (Lc1) at which the first crack occurred, and the critical load (Lc 2) at which the coating broke were calculated [2]. [2] The scratch images obtained with optical microscope, were evaluated together with acoustical emission graphics. The numerical data obtained from the experiments are given in Table 2.

HVIT Mean Vickers Hardness (HV-10mN) 10mN)

Uncoated AlTiN CrN Uncoated AlTiN CrN

2,8 2,82 2,4 2,20

373,9963 2903,99 2649,24 612,516 2827,485 2225,105

Scratch Testing Load (N)

Critical Load (Lc1)

Critical Load

30 30 25 30

6,5 6 8 7

23,5 19 21 18

(Lc2)

4. Evaluation

Table 1 Parameters of AlTiN and CrN Coatings.

M31 AISI 5115

Coating Thickness Mean (µm)

Material

AISI 5115

Surface

Table 2 Coating Thickness Thickness, Hardness and Scratch Test Measurement Data Data.

AISI 5115 and M31 steels are frequently used in the production of guns. Improving wear resistances of these parts is important in order to have them function properly and work without any problem. Scratch test methods are extensively used to identify mechanical characteristics such as breakage, damage and adhesion of surfaces of thin films and coatings [1].

Hardness values of coated samples increase 3,3 to 7,7 times compared to uncoated samples samples. After the coatings, although hardness of CrN coatings came forth at the expected value, hardness of AlTiN coatings resulted in a value 13 % less than the expected one. The critical loads (Lc2) for AlTiN coatings are approximately 23 % higher compared to CrN coatings for both of the base materials. The results are compatible with the hardness values obtained btained after the coatings. It was observed that the critical loads (Lc 2) were on the decrease as the surface roughness values of the same base materials decreased [3]. 5. Summary In this study, Adhesion Strength and Mechanical Failure Modes of AlTiN / CrN thin film coatings on AISI5115 and M31 steels, which were applied to improve surface characteristics of these steels, were examined by using the scratch method. 6. References [1]

[2]

[3]

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Efeoğlu., İ, Arnell, A.D., Çelik, A., “Adhesion Scratch Test Studies on Some of the TiN Coating”, MMO Symposium,, Denizli, 1999, 690-697. ASTM C1624-05, “Standard Standard Test Method For Adhesion Strength and Mechanical Failure Modes of Ceramic Coatings by Quantitative Single Point Scratch Testing”, ASTM International, 2010, 1-28. Blau, P.J., “Scratch adhesion testing”, Lab Handbook of Scratch Testing, Oak ridge, 7:1-15 (2002).

40th Leeds-Lyon Symposium on Tribology & Tribochemistry Forum 2013 September 4-6, 2013, Lyon, France

Development of a combined optical lever atomic force microscope with a quartz crystal microbalance D. Inoue1*, S. Machida1, Y. Ikada1, J. Taniguchi1, M. Suzuki1, M. Ishikawa2 , K. Miura2 1)

Department of Engineering Science, University of Electro-Communications, Chofu, Tokyo, Japan. 2) Depaerment of Physics, Aichi University of Education, Kariya, Aichi, Japan *

Corresponding author for [email protected]

1. Introduction A probe-tip-quartz-crystal-resonator technique enables us to observe the energy dissipation rate at a small contact area.[1] In 2003, Berg and Johnnsmann studied the tribology of micron-sized Au-Au contacts based on the ring-down technique. They found that the frictional force remains small below the velocity of 0.4 m/s and explained that a local slip-to-stick transition occurs at the oscillation amplitude of about 0.5 nm. [2]

2. Experimental To study the energy dissipation due to sliding motion in nano-meter scale, we have developed a combined optical lever atomic force microscope (AFM) with a quartz crystal microbalance (QCM). Figure 1 shows a sketch of the experimental setup. A resonator with substrate was mounted on a piezo-scanner base and was set facing an AFM cantilever as a force sensor. In the present experiments, a Si3N4 optical cantilever with a spring constant of 0.05 N/m (OMCL-RC800PSA-, Olympus Corporation) was used, and typical radius of the tip was 15 nm. The normal load acting on a Si3N4 tip was controlled by driving the piezo-scanner base. The restoring force and the energy dissipation due to contact are detected by changes in the resonance frequency fR and the Q-factor of the resonator Δ(1/Q),

Figure 1. Schematic diagram of the experimental setup. 3. Results and Discussion We prepared mica as the substrate. The sliding direction was parallel to the [110] direction. Figure 2 shows the average frictional force as a function of sliding distance for a normal load of 5 nN. The force increased with increasing sliding distance up to 0.7 nm, and became almost constant. We found that the force shows a transition around the lattice constant of the substrate.

where, MC is the mass of the oscillating area and κ is the effective spring constant, ΔE is the energy dissipated per cycle and E is the energy stored in the system. The average frictional force was observed as the dissipated energy par unit distance.

Where, A is the oscillation amplitude of the resonator.

Figure2. Oscillation amplitude dependence of average frictional force for the mica substrate at the normal load of 5nN. 4. References [1] [2]

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B. Borovsky, J, Krim, S. A. Syed Asif, and K. J. Wahl, J. Appl. Phys. 90, 6391 (2001). S. Berg and D. Johnnsmann, Phys. Rev. Lett. 91, 145505 (2003).

40th Leeds-Lyon Symposium on Tribology & Tribochemistry Forum 2013 September 4-6, 2013, Lyon, France

Effects of Doping Elements on the Tribological Properties of DLC films H. Fukuda1*, R. Tsuboi1, S. Sasaki1, T. Tamura2, S. Katou2 1)

Department of Mechanical Engineering, Graduate School of Tokyo University of Science 6-3-1 Niijyuku, Katsusika-ku, Tokyo 125-8585, Japan 2) KYB Corporation 1-12-1 Asamizodai, Minami-ku, Sagamihara-si, Kanagawa 252-0328, Japan *

Corresponding author for [email protected]

Diamond-like carbon (DLC) films are well known for reducing friction of interacting surfaces in relative motion. Tribological properties of DLC films are influenced by surrounding environment and its structure. It has been reported that a friction coefficient of hydrogenated DLC films had no effect on the friction reduction under the oil lubricating condition, while titanium nitride (TiN) films led to a lower friction coefficient in the same lubricating condition [1]. Therefore, in order to improve the reactivity between DLC films and lubricants, various experiments have been performed by doping several alloy elements to the DLC films [2]. However, there is still a lack of understanding of the sliding mechanisms which is changed by elements doping to DLC films. In this research, the friction behavior of Ti-, Cr-, and Si-doped DLC films and a-C:H DLC film were investigated by using a ball-on-disk tribo-tester under oil lubricating conditions.

after the experiment start. 4. References [1]

[2]

S. Miyake, et al. “Improvement of boundary lubrication properties of diamond-like carbon (DLC) films due to metal addition”, Trib. Int., 37, 2004, 751-756 B.Vengudusamy, et al. “Friction properties of DLC/DLC contacts in base oil”, Trib. Int., 44, 2011, 922-932 (a) 0.2

Friction coefficient

1. Introduction

Si−DLC

0.1

Four different types of DLC films were tested. In all cases, DLC films were deposited on the test specimens made of bearing steel. Friction tests were carried out using a ball-on-disk SRV tribo-tester, where a 10mm diameter bearing steel ball was loaded and rubbed against a DLC coated disc under boundary lubricating conditions (applied load = 50N, a frequency of 50 Hz, a temperature of 50 °C with a stroke of 1.0 mm for 1 hour) . The base oil and additives used in this study were PAO (poly alpha olefin), PAO+ZnDTP (zinc dialkyl ditio phosphate) and PAO+ZnDTP/MoDTC (molybdenum ditio carbamate).

a−C:H

Cr−DLC

0 0

2. Experimental details

20

40

60

Time [min]

(b) Friction coefficient

0.2

Si−DLC

Ti−DLC

0.1

0 0

Cr−DLC

a−C:H

20

40

Time [min]

60

(c)

3. Result

0.2

Friction coefficient

Figure 1 shows the friction coefficient as a function of sliding time for the DLC films under PAO, PAO+ZnDTP and PAO+ZnDTP/MoDTC. From Fig. 1 (a), the friction coefficients of all DLC films showed about 0.14 at the end of the experiment. Fig. 1 (b) showed that an addition of ZnDTP to base oil demonstrated more stable than that of PAO-lubricated condition. Furthermore adding MoDTC in PAO+ZnDTP (Fig. 1 (c)) showed that the friction coefficient of all DLC films became unstable with the beginning of the experiment except Cr-DLC. The Cr-DLC film showed a low friction coefficient about 0.09 and stable friction behavior at 15000 cycles just

Ti−DLC

Ti−DLC

a−C:H

Cr−DLC

0.1

Si−DLC

0 0

20

40

60

Time [min]

Fig.1

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Friction coefficient behavior of different DLC films under (a) PAO, (b) PAO+ZnDPT and (c) PAO+ZnDPT/MoDTC

40th Leeds-Lyon Symposium on Tribology & Tribochemistry Forum 2013 September 4-6, 2013, Lyon, France

Influence of Nitrogen on Friction Properties of CNx Coatings Based on First-Principles Molecular Dynamics and Tight-Binding Quantum Chemical Molecular Dynamics Methods Seiichiro Sato1, Shandan Bai1, Yuji Higuchi1, Nobuki Ozawa1, Koshi Adachi2, Jean-Michel Martin3, and Momoji Kubo1* 1)

Fracture and Reliability Research Institute, Tohoku University, 6-6-11, Aoba, Aramaki, Aoba-ku, Sendai 980-8579, Japan. 2) Department of Nanomechanics, Tohoku University, 6-6-01, Aoba, Aramaki, Aoba-ku, Sendai 980-8579, Japan. 3) Laboratoire de Tribologie et Dyanamique des Systemes, Ecole Centrale de Lyon 69134 Ecully Cedex, France. Corresponding author for [email protected]

Carbon nitride (CNx) and diamond like carbon (DLC) films are expected as solid lubricants for MEMS and have been studied actively. For previous experiments, CNx and DLC films showed low friction properties, and it is pointed out that chemical reactions strongly influence their friction properties. CNx film is expected to have lower friction properties and more durable than DLC film. However, this mechanism has not been clarified well. This is because it is very difficult to obtain atomic-scale dynamics directly during the chemical reactions by experiments, which affect their friction properties. In this study, our purpose is to clarify the super-low friction mechanisms of hydrogen terminated CNx (H-CNx) film compared to hydrogen terminated DLC (H-DLC) in an atomic scale by our first-principles molecular dynamics (FPMD) and tight-binding quantum chemical molecular dynamics (TB-QCMD) methods. 2. Method We employ our TB-QCMD code, Colors, and FPMD code, Violet, for performing friction simulations of the H-CNx and H-DLC coatings. In H-CNx model, 15% of carbon atoms are replaced by nitrogen atoms. The upper substrate is slid with 100 m/s and the bottom atoms of the lower substrate are fixed. A load is given to the upper substrate in a direction vertical to the interface. We calculate the cumulative averaged friction coefficient defined as the following equation; µ = Fx/Fz. Here, Fx and Fz represent the sums of horizontal and perpendicular forces to the upper substrate, respectively. All simulations are performed at 300 K.

are not generated at the interfaces of these films under 1 GPa as shown in Fig. 1 (a), the friction coefficient keeps a low value during the friction. In Fig. 1 (b), H-CNx film shows a low friction coefficient of 0.07 under 5 GPa. On the other hand, H-DLC film shows a high friction coefficient of 0.43 under 5 GPa. Here, while C-C and C-N bonds are not generated at the interface of H-CNx film, many C-C bonds are generated at the interface of H-DLC film. Thus, we suggest that H-CNx film has more stable and lower friction properties than H-DLC film under high pressure condition because of preventing the generation of C-C bonds. The details of these results are discussed in the conference. (a) Friction Coefficient

1. Introduction

H

ーH-CNx ーH-DLC

0.40 0.30 0.20 0.10 0.00 0

5

(b)

10 15 Time [ps]

20

N H

C

0.50

ーH-CNx ーH-DLC

0.40 0.30 0.20 0.10 0.00 0

3. Results and discussion First, to investigate super-low friction mechanism of CNx films, we performed friction simulations of H-CNx/H-CNx and H-DLC/H-DLC films by our TB-QCMD method. Fig. 1 shows time variation of the friction coefficients of the films under 1 GPa and 5 GPa. In Fig. 1 (a), both H-CNx/H-CNx and H-DLC/H-DLC films take a low friction coefficient of 0.05 under 1 GPa. Here, our previous study presented that the generation of C-C bonds at the interface of DLC film caused a rise of the friction coefficient [1]. Since C-C and C-N bonds

C

0.50

Friction Coefficient

*

5

10 15 Time [ps]

20

N

Fig. 1 Time variation of the friction coefficients of H-CNx and H-DLC under (a) 1 GPa and (b) 5 GPa. 4. References [1]

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Hayashi, K., Sato, S., Kubo, M. et al., “Fate of methanol molecule sandwiched between hydrogen-terminated diamond-like carbon films by tribochemical reactions: tight-binding quantum chemical molecular dynamics study”, Faraday Discuss., 156, 2012, 137-146.

40th Leeds-Lyon Symposium on Tribology & Tribochemistry Forum 2013 September 4-6, 2013, Lyon, France

Mechanical Response of Coated Surfaces under Severe Contact Loading Ali Elwafi 1*, Bader Al-sadi1, Azan Al-Rushdi1, and David C. Barton2

2)

1) Faculty of engineering, Sohar University, P.O Box 44, Al Jameah St, Sohar 311, Oman School of Mechanical engineering, University of Leeds, Woodhouse lane, Leeds LS2 9JT, UK *

Corresponding author for [email protected], Present address: Efccts, Ottawa, Canada

Abstract A number of new wear resistant hard coatings for

also on the properties and specifications of the whole

tribological contact are currently being developed to

contact system (substrate, coating, and interface) which

protect interacting surfaces of automobile engine

is a function of different variables such as contact

components. However, coating deterioration is one of

stresses, coating properties and coating thicknesses, and

the main ways in which these components reduce their

existence or otherwise of impurities.

service lives. To make these coatings not only to protect the surfaces but also to increase their durability, it is necessary to demonstrate their viability by investigating and understanding their mechanical behaviour and potential failure mechanisms.

The present work

investigates the mechanical response of steel engineered surfaces coated with hard layers with different properties at maximum Hertz contact pressures ranging from 540 MPa to 1540 MPa. The study focused on developing finite element models (using SLODWORK) to study the magnitude and distribution of the contact stresses both with and without surface traction forces due to friction. Stresses arising from differential strain of the impurities that deliberately inserted within the protective coating and the effect of their elastic moduli were also investigated. The results showed how the magnitude and location of the maximum stresses varied as a function of the layer thickness, properties and the loading conditions. The main failure modes anticipated included

delamination

within

the

coating,

and

interfacial delamination. It was concluded that the mechanical behaviour and response of engineered surfaces (with a protective hard coating) depended not only on the coating properties and specifications, but

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40th Leeds-Lyon Symposium on Tribology & Tribochemistry Forum 2013 September 4-6, 2013, Lyon, France

Neutron reflectometry of adsorbed additive layers on (a-C) DLC R. Simič1, T. Hirayama2, M. Kalin1* 1)

Laboratory for Tribology and Interface Nanotechnology, Faculty of Mechanical Engineering, University of Ljubljana, Bogišićeva 8, 1000 Ljubljana, Slovenia. 2) Department of Mechanical Engineering, Doshisha University, 1–3 Miyakodani, Tatara, Kyotanabe, Kyoto 610-0394, Japan. *

Corresponding author. Tel.: +386 1 4771 462. E-mail address: [email protected]

Diamond-like carbon (DLC) coatings have proven to be very promissing in protecting the contact surfaces of mechanical systems due to their low friction, low wear and anti-adhesion properties. It is known that most carbon films are chemically very stable and, therefore, generally inert towards external species under static conditions. However, under dynamic sliding conditions, DLC surfaces may interact with counter faces and with the hydrogen or water molecules in their surroundings [1]. Tribochemical reactions of DLC surfaces were also confirmed in cases with relatively complex additives, like ZDDP and MoDTC [2]. On the other hand, only a few studies on the adsorption of simple polar organic molecules, such as alcohols, exist on DLC [3]. Since the adsorption of polar groups is one of the fundamental boundary-lubrication mechanisms that affect both the friction and wear on steel surfaces, we aimed to find out whether such molecules form adsorbed layers also on the DLC surfaces. 2. Experimental We used neutron reflectometry to study the adsorbed additive layers on DLC, as this technique has been used successfully on metal surfaces [4]. Samples were silicon blocks, which were coated with a 40 nm thick a-C coating. The experiments with each block were performed in three steps; (1) a neutron reflectivity profile was obtained from the sample surface in air, (2) a reflectivity profile was obtained in base oil, and (3) a reflectivity profile was obtained in base oil mixed with 20 mmol/l of deuterated hexadecanol. The use of the deuterated additive was necessary to differentiate the neutron scattering length densities of the additive and PAO oil, which enabled the observation of adsorbed layers. The fitting of the data was performed using a Parratt theory. 3. Results Fig.1 presents the reflectivity profiles obtained for the a-C coating during each step. The thickness of the coating was calculated from the fitting of the data of the first step, and was determined to be 40.5 nm. In the second step, when the coating was exposed to pure PAO oil, no shift of the reflectivity profile was observed, as expected. In the third step, when PAO with deuterated hexadecanol was used, the shift of fringes was observed. Fitting of the data revealed that a 0.4 nm thick layer of

adsorbed additive was formed on the surface. The density of the layer was calculated to be more than 90 % of the density of the bulk hexadecanol. 100 PAO+OH 10

Reflectivity [arb. units]

1. Introduction

PAO air

1 0,1

0,01 0,001

0,0001 0,00001 0,01

0,02

0,03

0,04

0,05

0,06

0,07

q [Å-1]

Fig.1 Neutron reflectometry profiles for a-C coating. Fitting of the data revealed a 0.4 nm thick layer of adsorbed hexadecanol (OH) molecules. 4. Conclusions In this work neutron reflectometry was successfully used to study the adsorption of alcohol molecules on the DLC coating. The results revealed that hexadecanol adsorbs onto the surface of the a-C coating and forms a dense (90 %) 0.4 nm thick layer on it. This implies that alcohols can serve as potential boundary lubrication agents in the tribological DLC contacts. 5. References [1]

[2]

[3]

[4]

28/203

Erdemir, A. and Donnet, C., “Tribology of diamond-like carbon films: recent progress and future prospects,” J. Phys. D: Appl. Phys. 39, 2006, R311–R327. de Barros Bouchet, M.I et al., “Boundary lubrication mechanisms of carbon coatings by MoDTC and ZDDP additives,” Tribol. Int. 38, 2005, 257-264. Kalin, M. and Simič, R., “Atomic force microscopy and tribology study of the adsorption of alcohols on diamond-like carbon coatings and steel,” Appl. Surf. Sci. 271, 2013, 317– 328. T. Hirayama et al. “Thickness and density of adsorbed additive layer on metal surface in lubricant byneutron reflectometry,” Tribol. Int., 54, 2012, 100–105.

40th Leeds-Lyon Symposium on Tribology & Tribochemistry Forum 2013 September 4-6, 2013, Lyon, France

Structure and Properties of Titanium Doped Tungsten Bisulfide Thin Films Produced by Magnetron Co-Sputtering DC Technique J. De la Roche1,2, J. M. González1,2, E. Restrepo-Parra1, F. Sequeda2 1

2

Laboratorio de Física del Plasma, Universidad Nacional de Colombia-Sede Manizales, Manizales, Colombia. Laboratorio de Recubrimientos Duros y Aplicaciones Industriales RDAI, Universidad del Valle, Cali, Colombia.

Key words: Thin Films, Doping, Solid Lubricant, co-Sputtering

(108) (203)

(114)

(110)

(006)

(102)

Abstract In this work were deposited Titanium doped tungsten bisulfide films (WS2-Ti) on AISI 304 stainless steel substrates using Magnetron Co-Sputtering DC technique, varying titanium power cathode from 0 to 25W. Using Energy dispersive Spectroscopy (EDS) were determinate the titanium content on the WS2 structure, obtaining a maximum of 10%. X- Ray Diffraction (XRD) results showed for the pure sample the presence a hexagonal phase on high intensity on (100) plane. However with titanium insertion, it promoted a nanocomposite formation [1] this is verified with TEM images. Raman spectroscopy shows the formation of tungsten and titanium oxides of film surface. The tribological behavior was measured using Ball on Disk (POD) Test obtaining Friction Coefficients- Cycles curves, were it observed a friction values of 0.1 for the pure sample and 0.15 for 5W sample.

(103)

E-Mail: [email protected]

WS2-Ti 25W

Intensity (a.u)

WS2-Ti 20W WS2-Ti 15W WS2-Ti 10W WS2-Ti 5W

WS2

10

20

30

40

2

50

60

70

80

Figure 3. Coefficient of friction as a function of cycles by using the Ball on Disk test for the substrate and WS2 and WS2-Ti films

Figure 1. EDS of WS2 with different content of Titanium 1,1

120

W S Ti

100

1,0 0,9

Friction Coefficient

0,8

80 60

%

40

0,7 0,6 0,5

Steel WS2 WS2-Ti5W WS2-Ti10W WS2-Ti15W WS2-Ti20W WS2-Ti25W

0,4 0,3 0,2

20

0,1

0

0,0

0

5

10

15

20

0

25

1000

1500

2000

2500

3000

Cycles

Titanium power Cathode (W)

Figure 2. Diffraction pattern of the WS2 andWS2 -Ti layers grown by magnetron sputtering DC

500

References [1]T.W. Scharf, A. Rajendran, R. Banerjee and F. Sequeda, Thin Solid Films 517 5666–5675

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40th Leeds-Lyon Symposium on Tribology & Tribochemistry Forum 2013 September 4-6, 2013, Lyon, France

The Effect of Si and W Dopants on the Mechanical and Tribological Properties of Diamond-Like Carbon L.Austin1*, A.Neville1, T.Liskiewicz1, R.Tietema2 1)

Institute of Engineering Thermofluids Surfaces and Interfaces, Department of Mechanical Engineering, University of Leeds, Woodhouse Lane, Leeds, West Yorkshire, LS2 9JT 2) Hauzer Techno Coating BV, 5928 LL Venlo *Corresponding author [email protected]

Introduction Diamond-like carbon (DLC) coatings are recognised as a promising way to reduce friction and increase wear performance of automotive parts and are currently being introduced for some engine and transmission components. DLC coatings provide new possibilities in the improvement of the tribological performance of automotive components beyond what can be achieved with lubricant design alone. In this work, three DLC coatings are tested and their properties compared. Properties taken into consideration are: Young’s modulus, Hardness (nano and micro), thickness, chemical composition and tribology (friction and wear). The tests used to quantify these properties are nano indentation, micro indentation, ball abrasion testing, SEM/EDX, TEM(Figure 1)/EELS(Figure 2), pin on reciprocating plate tribometer and a white light interferometer, respectively. The DLC coatings employed in this series of testing are a PACVD DLC and Si-DLC deposited at the University of Leeds and a W-doped DLC acquired from Oerlikon Balzers. The three samples will be subject to the same testing conditions in all cases and the results will be compared with a specific emphasis on application for the valve train in a passenger vehicle.

Figure 2: Curve fitted EELS spectra for W-doped DLC

Figure 1: TEM micrograph of W-doped DLC

30/203

40th Leeds-Lyon Symposium on Tribology & Tribochemistry Forum 2013 September 4-6, 2013, Lyon, France

Tribological and Electrical Contact Behavior of Metal/DLC Nanocomposite Coating on Brass Substrate R. Hombo1*, T. Takeno2, J. Fontaine3, H. Miki4, N. Kato1, T. Nozu1, N. Inayoshi1, M. Belin3 and T. Takagi5 1)

2)

Frontier Research Institute for Interdisciplinary Science, Tohoku University, Aramaki aza Aoba 6-3, Aoba-ku, Sendai, MIYAGI 980-8578, Japan.

Institute of Fluid Science, Tohoku University, Katahira 2-1-1, Aoba-ku, Sendai, MIYAGI 980-8577, Japan. *Corresponding author: [email protected]

1. Introduction Demands for innovative technology on electrical contacts in vehicles have been increasing with the growth of market share of electrical and hybrid vehicles. Reducing the electrical contact resistance (ECR) and the coefficient of friction (μ) are the major technological issues. In this study, tribological and electrical behaviors of metal containing diamond-like carbon (DLC) nanocomposite coating deposited on a brass (Copper-Zinc alloy) substrate were investigated.

characteristics of the contact were thus provided by the tribofilm on the ball. Table 1

2. Experiment Experimental materials and conditions are shown in Table 1. A hybrid deposition process, coupling plasma enhanced chemical vapor deposition and DC magnetron sputtering of a metal (W, Cu) target, was used for the deposition [1]. The tribological and electrical contact behavior was investigated by using a ball-on-plate reciprocating tribometer. The four-terminal method was used for the measurement of ECR between the ball and the plate during the tribo-test.

Plate Normal load Track length Frequency Electrical current Sliding cycles Atmosphere

Brass (φ6.35mm) Brass (uncoated) Tungsten containing DLC (W-DLC) Copper containing DLC (Cu-DLC) 3N 0.8mm 0.5Hz 0.2Amps up to 1000 Ambient air (20-25 oC, 25-35%RH)

Electrical contact resistance, mOhms

10000

W-DLC

1000 100 10

Cu-DLC

Brass

1 0.1 0

Fig.1

200

400 Cycles 600

800

1000

Electrical contact resistance behavior

1.0

Coefficient of Friction

3. Results and Discussion Figure 1 and Figure 2 show the typical ECR and μ responses. In the case of the uncoated brass plate, low ECR and high μ were observed and their variations were relatively wide. In the case of the W-DLC, ECR gradually increased with increasing number of cycles and reached above 100 milliohms at 1000 cycles. In contrast, μ decreased and the value was maintained below 0.25 after 200 cycles. From the sliding surface of the ball, oxygen was detected but W was not detected by energy dispersive X-ray spectroscopy (EDS). Oxides of copper and zinc have high resistivity and low friction characteristics. So, it is supposed that above mentioned phenomena in the W-DLC experiment were caused by an oxidation of the ball surface. In the case of the Cu-DLC, while initial value of ECR was hundreds of milliohms, it gradually decreased with cycles and reached 1.5 to 2 milliohms after 600 cycles. μ started below 0.35 and decreased progressively, and stabilized around 0.25 after 600 cycles. Figure 3 shows typical sliding surfaces after 1000 cycles. Observation of worn surfaces after different number of sliding cycles reveals that a tribofilm was built up on the sliding surface of the ball, and that it grows as the sliding cycle increased. This tribofilm consists mainly of copper according to EDS. Surprisingly, the Cu-DLC coating on the plate was almost worn out after less than 600 cycles, without detrimental effects neither on ECR nor on μ. The good electrical and tribological

Experimental materials and conditions Ball

Materials

5)

Conditions

4)

DENSO CORPORATION, 1-1 Showa-cho, Kariya-shi, AICHI 448-8661, Japan. Graduate School of Engineering, Tohoku University, Aoba 6-6-1, Aramaki, Aoba-ku, Sendai, MIYAGI 980-8579, Japan. 3) Laboratoire de Tribologie et Dynamique des Systèmes, École Centrale de Lyon, 69134 Écully, France.

Brass

0.8 0.6

W-DLC

0.4

Cu-DLC

0.2 0.0 0

Fig.2

(a) Ball

200

400

Cycles

600

800

1000

Coefficient of friction behavior

(b) Plate (Cu-DLC)

Fig.3 Sliding surfaces after 1000 cycles

4. Summary A Cu-rich tribofilm providing good tribo-electrical characteristics was formed on the ball by sliding with the Cu-DLC. In contrast, no W but copper and zinc oxides causing high ECR were observed on the ball after sliding with the W-DLC. 5. Reference [1] Takeno T et al, Diamond and Related Materials, 18, 2009, 1023-1027.

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40th Leeds-Lyon Symposium on Tribology & Tribochemistry Forum 2013 September 4-6, 2013, Lyon, France

Tribological behaviour of ZrCN PVD and other DLC coatings for engine components A. Igartua1, X. Fernandez1, B. Zabala1*, M. Conte1, U. Ruiz de Gopegui1, P. Tribotte2, M. Abramczuk2, JM. Malhaire2 1)

IK4-Tekniker, Parque Tecnológico de Guipúzcoa, Calle Iñaki Goenaga 5, 20600 Eibar, Spain RENAULT, Direction de la Recherche, des Etudes Avancées et des Matériaux.SCE 68530. FR TCR LAB 0121, avenue du golf 78288 Guyancourt cedex. France 2)

*

[email protected]

1. Introduction

Wear Test

400

2

200

1

Coatings0

A01 A03 Disc wear Scar (µm) 3 2 Ball Wear Scar (µm) 611,9 532,9

B01 B02 B03 5,5 4 2 718,3 658,5 494,0

C02 C03 3 3 635,7 637,8

D01 0,6 536,7

0

Fig 1. Friction and Wear Tests Results

Friction Coefficient ()

Fig 2. a) ZrCN D01 Disc wear scar (max depth: 0.6µm) b) DLC Coating C 03Disc wear (max depth:3µm)

Stribeck Curves

0,25 0,2 0,15

0,1 0,05 Speed/Load (mm/s*N)

0 0 A01

A02

0,2 A03

B01

0,4 B02

0,6 B03

0,8 C01

C02

1 C03

D01

Fig 3.Stribeck curves for ZrCN and DLC´s coatings 4. References [1]

3. Results and conclusions The ZrCN (D01) coating presents the lower wear scar depth (of about 0.06 µm) while the rest of the coatings ranged between 2 - 5.5 µm. The Figure 1and 2 show the test profile, the maximum depth on the disc scar, h (µm). The Stribeck curve of the ZrCN coating shows a stable coefficient of friction under conditions of high load/small frequency. In fact, as seen at Figure 3, a minimum variation of 0.02 was observed with ZrCN (D01) in comparison with other coatings that ranged between 0.03 - 0.15.

600

Disc Wear Scar 4 (max depth; h:µm) 3

2. Test setup and specimens The test rig used for the experiments is the SRV (Schwingung-Oscillating, Reibung-Friction, and Verschleiss-Wear) Tribometer in ball-on-disc configuration, able to simulate high frequency reciprocating sliding motion to evaluate friction, wear and the maximum allowed load characteristics. A stainless steel AISI 52100 ball is matched against a stationary coated steel test disk (substrate: M2 polished) with a roughness of 0.05μm. The system is in a bath of the reference lubricant SHELL PC 1277- SAE 15W40. Two kinds of tests were run according to the following standards: ASTM D5707/ D6425 to evaluate the friction and wear properties (stable load is applied), and ASTM D5706/ D7421 to determinate the maximum allowed load before failure under sliding test conditions. The tests were carried out at a temperature of about 180ºC in order to reproduce actual working conditions.

800

5

Ball Wear Scar (diameter; d µm)

6

Plasma Assisted Chemical Vapour Deposition (PACVD) and Physical Vapour Deposition (PVD) coatings are used in many fields of Tribology and, in particular, as coatings for engine components in automotive applications for enhancing wear resistance and achieving friction reduction [1]. Recently, the effect of the tribo-reactive materials in combination with bio-lubricants for engine components was published by A. Igartua et al. [2]. In this work different types of commercial available Diamond Like Carbon (DLC) coatings are compared with the new proposal multilayer ZrCN coating deposited by PVD and developed by IK4-TEKNIKER, presenting the experimental/analytical approach for coating pre-selection before engine tests in actual working conditions.

[2]

C. Donnet , Recent progress on the tribology of doped diamond-like and carbon alloy coatings: a review, Surface and CoatingsTechnology 100-101 (1998) 180-186 A. Igartua, X. Fernández, et al. “Biolubricants and triboreactive materials for automotive applications”, Tribology International, 42, 561 -568, 2009

6. Acknowledgements The authors would like to acknowledge the EC funding in the frame of the European Project Powerful (Contract 234032).

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40th Leeds-Lyon Symposium on Tribology & Tribochemistry Forum 2013 September 4-6, 2013, Lyon, France

Tribological performance of Cr/CrN and Cr/CrN/CrAlN multilayer coatings deposited by r.f. magnetron sputtering N.E Beliardouh1* , K. Bouzid1, B. Tlili2, C. Nouveau2 1)

2)

Laboratoire Ingénieries des surfaces(LIS), UBMA, BP12-23000 Annaba Algérie. Laboratoire Bourguignon des Matériaux et Procédés (LABOMAP), CER ENSAM de Cluny, Rue Porte de Paris, F-71250, France. *

Corresponding author for [email protected]

1. Introduction

a)

The objective of this work was to analyze the surface states of the coated samples in terms of the friction coefficient evolution during dry sliding using two (02) different static partners (alumina balls & WC-Co balls). Samples were elaborated by R.F sputtering magnetron. The chemical compositions and some characteristics of samples are given in table 1. The friction tests conducted on the surface of (CrN /CrAlN) samples are analyzed and compared to (Cr/CrN/CrAlN) samples. The results are interpreted basing on previous works [1] and are discussed with other

10 µm 100 µm

reports [2].

b)

2. Tribological tests Tribological experiments were carried out using a real time ball-on-disk test machine from CSM instruments. Dry wear resistance tests were performed and the following experimental parameters were kept constant for all tests: Sliding velocity = 0.01 m s-1; Wear track diameter = 4 mm; Diameter of balls = 6 mm; Applied force = 1 N; Total sliding distance =200 m; Temperature=20°C and the relative humidity about 40±5%. After the tribotests, wear rates of balls and the wear rates of the coatings were determined using standard equations. The wear mechanisms and the chemical composition of the wear debris and of the worn surfaces were studied using SEM/EDS analysis.

200 µm Fig. 1 (a)- Example of typical appearance of wear track on Cr/CrN/CrAlN after 200 m sliding distance against alumina balls; (b)-Corresponding wear scar on alumina ball; (c)-3D final wear track topographies corresponding to (a).

3. Results The counterpart material has a distinctive influence on the tribological behavior of the coatings; consequently different wear mechanisms are shown. The Cr/CrN/CrAlN multilayer coatings present best resistance wears than CrN/CrAlN; The Cr under layer reduces the wear severity. The highest wear rates of disc were estimate for tribological contacts with Al2O3. Table 1 Characteristics of multilayer coatings

Samples 1 Cr/CrN/CrAlN 2 CrN/CrAlN 3 Cr/CrN/CrAlN 4 CrN/CrAlN

Chem. Composition (at.%) N Al Cr

51.8 50.8 50.5 52

4.2 4 4.7 5

42.9 43.1 42.5 41.3

Thick. (nm) 1500 300 300 1500

4. References [1]

[2]

Hard. (Gpa)

26 22 32 17

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B. Tlili, C. Nouveau, M.J. Walock, M. Nasri, T. Ghrib “Effect of layer thickness on thermal properties of multilayer thin films produced by PVD; Vacuum 86 (2012) 1048-1056 J.E. Sanchéz, O.M. Sanchéz, L. Ipaz, W. Aperador, et al. “Mechanical, tribological, and electrochemical behavior of Cr1−xAlxN coatings deposited by r.f. reactive magnetron co-sputtering method”Applied Surface Science, 256, Issue 8, 1 (2010), 2380–2387

40th Leeds-Lyon Symposium on Tribology & Tribochemistry Forum 2013 September 4-6, 2013, Lyon, France

Tribological properties of Ti(CN)x hard coating on titanium alloy by pulsed plasma electrolytic carbonitriding process Y.K. Qin, D.S. Xiong*, J.L. Li School of Materials Science and Engineering, Nanjing University of Science and Technology, 210094 Nanjing, China. *

Corresponding author for [email protected]

1. Introduction

increases to 478HV0.1 after 80min treatment.

Due to the poor tribological properties under dry friction, the application of titanium alloys is limited in tribological components. Many surface engineering technologies such as oxygen diffusion treatment, diffusional carbonitriding et al. have been developed to improve the wear resistance [1,2]. Plasma electrolytic carbonitriding (PEC/N) technology can fast deposit hard cabonitriding layers on metal surface at near-ambient temperature, obviously improving the surface hardness and wear resistance [3,4]. In this paper, the PEC/N coatings were deposited on titanium alloy and the tribological properties were investigated. 2. Experimental details Ti6Al4V alloy plates (Ф20mm×2mm) were used as substrates. For PEC/N treatment, a pulsed high voltage power supply was employed with the cathode of Ti6Al4V alloy plate and the anode of graphite plate. The electrolyte was a mixed aqueous solution of formamide and KCl. The applied voltage, pulse frequency and duty cycle were fixed at 250V, 10kHz and 40%, respectively, and the samples were treated for 40-80min. The phase components, morphologies and hardness were analyzed with XRD, FESEM and Vickers indenter using the load of 100g. Friction tests were carried out with ball-on-disk tribometer (1N and 0.1m/s) under dry friction. The wear rate was calculated by the weight loss. 3. Results and Discussions Fig.1 shows the XRD patterns of the PEC/N samples treated for different time. It is obvious that the layer consists of complex Ti(CN)x phase and the intensity of its peaks increase with the increase of discharge time. The roughness of Ti(CN)x coating increases owing to the plasma discharge at the substrate surface. With the increase of discharge time, small cracks appear in the coating (Fig.2). Fig.3 shows the variation of friction coefficient and wear rate of PEC/N sample under dry friction. The friction coefficient of PEC/N coating increases quickly at the initial stage; however, it keeps stable at 0.4 during the sliding process, which is lower than the untreated sample (Fig.3(a)). Compared with the untreated sample, the PEC/N coating shows a great improvement in wear resistance, especially with the increase of treated time. After sliding about 20min, the wear rate of PEC/N treated samples decreases to 1.8×10-4mm3/N*m ~ 3.5×10-4mm3/N*m, which is obviously lower than the untreated samples, about 7.1×10-4mm3/N*m (Fig.3(b)). Compared to the substrate with the hardness of 340HV0.1, the average surface micro-hardness of PEC/N coating significantly

Fig.1 XRD patterns of PEC/N samples

Fig.2 SEM photograph of PEC/N sample, 80min

Fig.3 Friction coefficient and wear rate of PEC/N samples 4. Conclusions Ti(CN)x hard coating were deposited on Ti6Al4V alloy by plasma electrolytic carbonitriding process in a mixed formamide electrolytic solution. The average micro-hardness of PEC/N coating increases with the increase of discharge time. The friction coefficient and wear rate decrease obviously compared to the substrate. The results demonstrate that PEC/N treatment can obviously improve the surface hardness and wear resistance of Ti6Al4V alloy. 5. References [1]

[2]

[3]

[4]

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Qu J., Blau P.J., Howe J.Y., Meyer Iii H.M., “Oxygen diffusion enables anti-wear boundary film formation on titanium surfaces in zinc-dialkyl-dithiophosphate(ZDDP)-containing lubricants,” Scripta Materialia, 60, 2009, 886-889. Matsuura K., Kudoh M., “Surface modification of titanium by a diffusional carbonitriding method,” Acta Materialia, 50, 10, 2002, 2693-2700. Nie X., Tsotsos C., Wilson A., Yerokhin A.L., Leyland A., Matthews A., “Characteristics of a plasma electrolytic nitrocarburising treatment for stainless steels,” Surface and Coating Technology, 139, 2-3, 2001, 135-142. Shen D.J., Wang Y.L., Nash P., Xing G.Z., “A novel method of surface modification for steel by plasma electrolysis carbonitriding,” Materials Science and Engineering A, 458, 1-2, 2007, 240-243.

40th Leeds-Lyon Symposium on Tribology & Tribochemistry Forum 2013 September 4-6, 2013, Lyon, France

CFD Investigation of hydrodynamic lubrication on textured surface - Effects of interaction between dimples Yasutsugu OSHIMA1)*, Ryo TSUBOI1) and Shinya SASAKI1) 1)

Department of Mechanical Engineering Tokyo University of Science

6-3-1 Niijyuku, Katsushika-ku, Tokyo 125-8585, Japan *

Corresponding author for [email protected]

1. Abstract Surface texturing has been recognized to be very efficient in modifying tribological performances of sliding surfaces. The effects of surface texturing change with lubricating conditions. In the hydrodynamic lubrication, it is known that the generation of hydrodynamic pressure increases the load carrying capacity of the sliding surface. In many numerical studies, two- or three-dimensional analyses for the single dimple were investigated in the hydrodynamic lubrication. On the other hand, there is small number of studies about three-dimensional analysis of multi dimples. In the single dimple analyses, it is insufficient to investigate tribological properties of the textured surface because the pressure distribution and flow configuration are affected by the adjacent dimples. In this paper, influence of the pitch and pattern arrangement of the dimples are investigated using three-dimensional simulations. In the simulations, commercial CFD software ANSYS CFX Ver.14.5 was used. It is assumed that flow field is three-dimensional, incompressible and laminar. Temperature distribution and a cavitation generation were not taken into account. Working fluid is assumed to be oil (VG-16), and physical properties of the working fluid are listed in Table1. Figure 1 and 2 show cross-sectional profile and pattern arrangement of the dimple, respectively. The pitch and geometry parameters are listed in Table 1. Dimples are placed nine.

The periodic boundary conditions are imposed on both sides of the computation unit along the z-direction. The upper wall is smooth and has a relative velocity, which is 1 m/s. Upper and lower wall are parallel. The inlet and outlet boundary conditions along the x-direction are static pressure 100kPa. Table 1 Dimension properties of simulation and physical properties of working fluid Dimple depth d 10 [m] Dimple diameter 50  [m] Film thickness h 5.0 [m] Pitch 70, 100 [m] 3 Density 880  [kg/m ] Kinematic viscosity  [m2/s] 16 × 10-6 Figure 3 shows the pressure distribution in case of pattern B. In both pitches, minimum and maximum pressure is observed at the first dimple lines and the last dimple lines. The range of the highest and lowest value of pressure is bigger in case of 70 mm pitch. At the each dimple, the peak of the pressure is confirmed, and the magnitude of the peak in case of 100 mm pitch is larger than that in 70 mm pitch. Load capacity of the sliding surface in 70 mm pitch calculated from integration of the pressure is 0.100 N/mm2. Hence, the effect of the peak observed in each dimple is not dominant. From the figures, small pitch raises maximum pressure and decreases minimum pressure both patterns.

Sliding direction

h



d

Figure 1 Geometry of texture

Pitch Pitch

Pitch Pitch

y x (a) Pitch = 70 m

(a) Pattern A

(b) Pattern B

Z (b) Pitch = 100 m

Figure 3 Pressure distributions in case of pattern B

Figure 2 Pattern arrangement of dimples

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40th Leeds-Lyon Symposium on Tribology &TribochemistryForum 2013 September 4-6, 2013, Lyon, France

Combined Experimental and Numerical Study of PTFE Faced Thrust Bearings Considering Effect of Creep on Bearing Performance B C Rothwell, R W Hewson, A Neville, AMorina, D C Barton School of Mechanical Engineering, University of Leeds, Leeds, LS2 9JT

2. Theory Thepressure in the fluid film isobtained bycoupling theReynoldsequation with a three dimensional finite element stress-strain model of the PTFE face [2]. The thermal characteristics are also included with the viscous losses resulting in heat generation. The energy equation then models the heat conduction and convection through the lubricating oil, pad face and backing steel[3]. From the initial solution to the TEHL problem a transient solution is used to consider the creep of the PTFE face material. The creep characteristics are obtained from experimental results (described below). This allows the bearing characteristics to be considered throughout its operational life, including the pressure and temperature profiles, and the evolution of the pad topography due to creep. The overall frictional performance of the bearing can also be described. 3. Experimental Creep Tests Compressive creep experiments were conducted on PTFE samples and a creep determined as a function of temperature and pressure.The samples tested were of 10mm thickness, and 5mm diameter.The PTFE used in this study was a filled grade with 15% carbon black and 2% graphite mixture. The experimental test range considered was that of temperatures ranging

from 40 to900Cand pressures of 4 to 12MPa.This data was used to derive a creep rate function, in terms of temperature and pressure. This relationship was then incorporated into the modelto allow long term creep performance of the pad to be investigated. 4. Results Figure 1 shows typical transient creep for different temperatures and load. From Figure 1 it can be seen that after an initial large strain and primary creep region lasting for around 10 minutes there is a secondary creep rate which is almost constant. 8 7

4MPa 40Deg

6 Strain (%)

1. Introduction Hydrodynamic thrust bearings are used in a wide range of rotating machinery applications such as hydroelectric generators and submarine engines.Polytetrafluoroethylene (PTFE) has been shown to be a promising pad face material due to its large temperature range and low coefficient of friction [1]. One of the restrictions on its more widespread adoption is lack of understanding of such bearings’ long term transient ThermoElastoHydrodynamic Lubrication(TEHL) performance. This includes the through-life creep performance of the polymer face and its effect on film thickness and bearing thermal characteristics. The work presented here combines a computational and experimental approach to modelling PTFE faced thrust bearings at a range of different operating conditions. The creep performance of the polymeris included in the simulation, and a prediction of bearing performance over the lifetime of the bearing is presented.

5

4MPa 90Deg

4 3

8MPa 40Deg

2 1

8MPa 90Deg

0 0,001

0,1 10 Time Log(hours)

Fig.1 Creep behaviour of the PTFEat varying Loads and Temperatures The model predicts the pressure and temperature profile across the pad face and allows comparisons to be made between initial geometry and once creep has occurred. 5. References [1] Glavatskih S, Fillon M. THED analysis of thrust bearings with PTFE faced pads [2]Dowson and Higginson (1977). ElastoHydrodynamic Lubrication. 2nd ed. Surrey: Pergamon Press Ltd. [3]Pai (1956). Viscous Flow Theory, I-Laminar Flow. D. Van Nostrand Company Inc.

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40th Leeds-Lyon Symposium on Tribology & Tribochemistry Forum 2013 September 4-6, 2013, Lyon, France

Film thickness equations for line-contact thermal elastohydrodynamic lubrication under misaligned loads Zhijian Wang, Xiaoyang Chen*, XuejinShen School of Mechanical Eng ineering and Automatic, Shanghai Un iversity No.149 Yanchang Road, Zhabei District, 200072 Shanghai, China *

Corresponding author for [email protected]

The film th ickness is the impo rtant index in line-contact thermal elastohydrodynamic lubrication. Fro m the viewpoint of engineering application, the simp lified film thickness equations are more convenient than numerical co mputation. Recently, the formu las simu lated by Dowson and Higginson, Pan and Hamrock are widely-used. The effect of misalign ment, thermal and finite length could not be considered in them. While it has been verified these factors can apparently influent film thickness by Xiaoling Liu, Haoyang Sun and Xiaoyang Chen. The model on thermal elastahydrodynamic lubrication under misaligned loads has been established by the author’s former work. In the present paper, the effect of dimensionless load, speed, and material parameters on film thickness is discussed(see Fig.1-2). Figs.1-2 show the variat ion of the central and minimu m film thicknesses with d imensionless load parameter in different misaligned angles. As the dimensionless load parameter increases, the central and minimu m film thicknesses decrease. And the effect of misaligned angles on the central film thickness is very little, while it apparently influent the min imu m film thickness, especially in heavy load. The results of numerical computation are used to developed suitable equations for determining the central and min imu m film thickness. H cen  1.649W

0.031

H min  0.108W

U

0.244

0.620

U

G

0.717

0.502

G

e

Fig.2 Effect of dimensionless load on dimensionless minimu m film thickness (U=5.54×10-11, G=4972, S=0)

0.006 S  0.018

0.775

e

0.1 S  25.15

If slid/rolling rat ios and misaligned angle are set to zero, the current formulas are converted to simp ler equations. By comparing to the widely-used equations, the validity of the present equations is proved(see Fig.3-4). It shows the results of our current equations are close to those reported by Dowson and Hamrosk.

Fig.3 Verificat ion of formu las

Fig.1 Effect of dimensionless load on dimensionless central film thickness (U=5.54×10-11, G=4972,S=0)

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40th Leeds-Lyon Symposium on Tribology & Tribochemistry Forum 2013 September 4-6, 2013, Lyon, France

Finite Line Contacts EHL Analysis of Misaligned Logarithmically Profiled Roller T. J. Park1* 1)

School of Mechanical Engineering, ERI, Gyeongsang National University, Jinju, 660-701, Korea. *

[email protected]

1. Introduction The EHL of finite line contacts occur in machine elements such as roller bearings, disk cam and roller followers. The rollers are profiled their ends to relieve high edge stress concentration caused by their finite length and misalignment. Until now, the profile design is mainly depend on the elastostatic analysis and it is generally understood that the logarithmic profile (Lundberg profile) to be the best for uniform pressure distribution. However, the rollers and races are separated by the EHL film and the pressure distribution is different from those of elastostatic state. Although the Lundberg profile is commonly used in roller bearing design, few EHL studies concerning this profile have been reported. Sun and Chen [1] introduced the profile modification coefficient and obtained converged solutions, however, some of their results were physically inconsistent. Therefore, more studies are required to investigate detailed EHL behaviors. In this study, a numerical analysis is carried out to study the effect of profile modification coefficient and roller misalignment on the EHL of a Lundberg-profiled cylindrical roller. The EHL results are compared and variations of the minimum film thicknesses with dimensionless parameters, profile modification coefficient and misalignment are presented.

profile, the minimum film thickness occurred always near the edge region [3]. The minimum film thickness can be increased with proper adoption of the profile modification coefficient. And very small misalignment can influence highly on the EHL results.

Fig. 1 Pressure and film contour for Lundberg profile.

Fig. 2 Pressure and film contour for d = 2.5.

Fig. 3 Comparison of pressure and film thickness.

2. EHL film thickness In EHL film thickness, the profile modification coefficient, d , is defined as ì 2w ì 2y 2 ü l y < ï- p El ln í1 - ( l ) ý , 2 x ï î þ hg = +d ´í 2R ï 2 w ì1.1932 + ln( l ) ü , y = l ý ïî p El íî 2c þ 2 2

Fig. 4 Variations of the minimum and central film thicknesses with profile modification coefficient.

3. Numerical methods To solve the highly nonlinear EHL problems, a finite difference method with non-uniform grids and the Newton-Raphson method is used [2,3]. Irregular grids of 101x61 are constructed over the computation zone, and the numerical data used are as follows: R = 5 mm, l = 10 mm, E = 220 GPa, Z = 0.55, ho = 0.0411 Pa·s.

Acknowledgements This research was supported by Basic Science Research Program through the NRF of Korea funded by the Ministry of Education, Science and Technology (Grant number 2011-0014650). 5. References

4. Results and discussions

[1]

Near roller edge region, the pressure distributions and film thicknesses for different profile modification coefficient are shown in Fig. 1 ~ Fig. 3. In Lundberg

[2] [3]

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Sun, H. and Chen, X., Proc. of IUTAM, 107-120, 2006. Park, T. J. and Kim, K.W., Wear, 223, 102-109, 1998. Park, T. J., Proc. of ITS 2013, Lulea, 2013.

40th Leeds-Lyon Symposium on Tribology & Tribochemistry Forum 2013 September 4-6, 2013, Lyon, France

High-tech anti-wear lubricant based on carbon nanotube/ionic liquid combination T. Taaber1,2*, K. Põhako-Esko1,2, M. Plaado2, K. Saal2, R. Lõhmus2, U. Mäeorg1 1)

2)

University of Tartu, Institute of Chemistry, 14a Ravila St.,50411, Tartu, Estonia. University of Tartu, Institute of Physics and Estonian Nanotechnology Competence Center,142 Riia St., 51014, Tartu, Estonia. * Corresponding author for [email protected]

1. Introduction

and high sliding speed), and their self-repair function to

Nowadays the development of lubricant is relevant

the worn surface, and good environmental-friendliness [5].

because of the ongoing needs for reducing energy and

Adding only a small amount of nanoparticles to a

material losses in mechanical devices. The aim of the

lubricant can significantly improve its lubricating

present study is to investigate the applicability of carbon

properties.

nanotube/ionic liquid composites as novel protective lubricating

films

for

metal

wear

parts.

Either

4. Summary Ionic

nanoparticles or ionic liquids independently have been shown to exhibit exceptional lubricating qualities[ 1 , 2 ]. However, the combinations of the two have not been

liquids

were

combined

with

differently

functionalized carbon nanotubes and obtained mixtures were tested with standard tribological tests. The combination of carbon nanotube/ionic liquid can

demonstrated before.

significantly reduce the long-term instability and 2. Ionic liquids

clustering of the particles in suspensions (e.g. oil

Ionic liquids have remarkable lubrication and anti-wear

suspensions), as it is well known that ionic liquids are

capabilities as compared with lubrication oils in general

highly effective stabilizer for nanoparticles[6]. In addition,

use. Ionic liquids are suitable at harsh friction conditions

the novel type lubricant has many advantages and can

that require high thermal stability and chemical

also widen the range of applications, e.g.

[3]

wider

inertness . There is a very wide range of different ionic

temperature range and preserved functionality at harsh

liquids and their properties can be modified by selection

conditions where oil-based lubricants fail.

of suitable cation and anion. In

current

study

different

imidazolium

and

5. References

bis-imidazolium ionic liquids with TFSI (bis(trifluoromethane)sulfonimide) and FAP (trifluorotris(pentafluoro ethyl)phosphate) anions were investigated. To obtain better adhesion with lubricated surface polar functional groups were added to ionic liquid cation structure.

3. Nanoparticles In recent years nanoparticles have gained much attention as the extreme pressure and anti-wear additives to lubricating oils

[ 4 ]

. Reasons behind this include

remarkable tribological behavior of nanoparticles even at

(1) M.-D. Bermúdez, A.-E. Jiménez, J. Sanes, F.-J. Carrión, Molecules 2009, 14, 2888-2908. (2) V.N. Bakunin, A.Yu. Suslov, G.N. Kuzmina, O.P. Parenago. J. Nanopart. Res., 2004, 6, 273–284. (3) I. Minami, Molecules 2009, 14, 2286-2305. (4) L. Rapoport, V. Leshchinsky, I. Lapsker, Y. Volovik, O. Nepomnyashchy, M. Lvovsky, R. Popvits-Biro, Y. Feldman, R. Tenne, Wear 2003, 255, 785-793. (5) Q.J. Xue, W.M. Liu, Z.J. Zhang, Wear 1997, 213, 29-32; (6) J. Dupont, J. D. Scholten, Chem. Soc. Rev., 2010, 39, 1780–1804.

severe frictional conditions (high temperature, high load

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40th Leeds-Lyon Symposium on Tribology &TribochemistryForum 2013 September 4-6, 2013, Lyon, France

Lubricant Rheology Effect on Roughness Behavior in EHL Contacts P. Sperka1*, I. Krupka1, M. Hartl1 1)

Faculty of Mechanical Engineering, Brno University of Technology, Technicka 2896/2, Brno, Czech Republic. *

Corresponding author [email protected]

1. Introduction The trend of decreasing of lubricant film thickness in tribological systems is one of the important features of current tribology stirred up by the quest for higher efficiency and energy saving. As a result, the influence of the surface micro geometry on the contact performance and machine component life increases steadily. Roughness features are elastically or plastically deformed during EHL contact passage. The elastic deformation is connected with pressure variations and effectively decreases the actual roughness height. The pressure variations are related to subsurface stress field and affecting surface fatigue life. The surface height has a role on severity of asperity contacts in mixed regime. Therefore, the effects of surface roughness and topography on lubrication film thickness and pressure have been a subject of a number of numerical and experimental studies. Systematic study of a low-amplitude surface roughness passing through a rolling EHD contact has led to general model called amplitude attenuation theory. It was found that the elastic deformation of roughness features is wavelength dependent, where short wavelengths are deformed less than the long wavelengths. The effect of operational conditions can be expressed by relation for non-dimensional wavelength. It was found that the cases of pure rolling and rolling-sliding show different behavior. In pure rolling case the model with one component is sufficient for the film thickness description. However, in rolling-sliding case two components model is necessary to explain the film variations. It is roughness deformation and so called complementary wave, the first moves at rough surface speed and the second is drift by mean entrainment speed. Recently, it was shown that the amplitude of complementary wave is related to the conditions in contact inlet contrary to roughness deformation which is influenced by conditions inside the contact. Unlike the contact inlet where lubricant often behaves as Newtonian fluid, inside the contact the flow is governed by non-Newtonian phenomenon. The current amplitude attenuation model for rolling-sliding conditions is based on Ree-Eyring shear thinning theory and parameter τ0 with in the form [1]: ha 1  iCQ 6 2  , Q  sign(u) 2 0 2 A0 1  iQ  iCQ  E' h

(1)

where ha/A0is the complex amplitude ratio representing the modified amplitude and phase, λ is roughness wavelength, E’ is reduced elastic modulus,

his mean film thickness, C = hE’ / 4Bimplies the fluid compressibility effect. 2. Material and methods The experimental results were obtained by using ball-on-disk optical tribometer. Thin film colorimetric interferometry was used for the film thickness evaluation. Experiments conditions are in Tab 1. Table 1 Operational conditions and lubricants LoadF 50 N Reduced modulus elasticityE’ 123.8 GPa Mean film thickness, h 220 nm Lubricant min. oil SR600 synth. oil PAO650 Viscosity, η 0.22 Pa.s ~6Pa.s Pressure-viscosity 24 GPa-1 ~20 GPa-1 Eyring stress, τ0 5 MPa ~0.06MPa 3. Results Fig. 1 shows measured profile of transverse ridge with initial height 200 nm. For both lubricants deformation for same mean film thickness is very similar. However, this does not correspond to Eq. 1 since the both lubricant has significantly differentτ0 value.

Fig 1Measured film thickness profile;black solid line PAO650, gray dashed line SR600 oil.

4. Conclusions The experiments with artificial roughness features and two lubricants withvarious τ0stress exhibit similar deformation which cannot be explain by current theory. In this study the effect of lubricant rheology will examine to extend the present amplitude attenuation theory. References [1]

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Hooke. CJ, Roughness in rolling-sliding elastohydrodynamic lubricated contacts. Proc. Instn. Mech. Engrs. Part J: J. Eng. Tribol., 2006; 220: 259-271.

40th Leeds-Lyon Symposium on Tribology &TribochemistryForum 2013 September 4-6, 2013, Lyon, France

Modeling of the edge effects for Main Bearings of a Multi-supporting Crankshaft of an Internal Combustion Engine: the Theory Ju.Rozhdestvenskiy, E.Zadorozhnaya, N.Khozeniuk*, A.Mylnikov, A. Boyarshinova Autotransport and service department, South Ural State University (National Research University), Chelyabinsk, 454080 Lenin av. 76, Russia. *

Corresponding author for [email protected]

The mathematical model for improving of the calculation of the main bearings system of a multi-supporting crankshaft of an internal combustion engine is offered. It’s based on applying the continuous scheme of the multi-supporting crankshaft with the liquid friction supports which are fixed into the elastic crankcase. The crankshaft is loaded with forces which change both in magnitudes and directions. The elastic behavior of a crankcase is simulated by the finite elements method. The nonlinear properties of the lubricant layers are considered in the continuous model of a crankshaft. To define these properties the set of equations of the movement of a journal (a shaft neck) on a lubricant layer and Reynolds's modified equation for the non-Newtonian liquid has been constructed for each bearing. While creating the set of the motion equations, it was supposed that each journal has 5 degrees of freedom: two linear coordinates of the mass center and three Euler’s angles. The rheological model of the non-Newtonian liquid n 1

 * Vx, z , T , p     I  2  e T  p  C1eC 2 T  C3  presented in [1] is used in the Reynolds modified equation. Where  is viscosity of the lubrication at a low share 2

2

 V   V  rate (to 102 sec-1); I 2   x    z  is the second  y   y  invariant of share rates; n is the parameter which characterizes the degree of the non-Newtonian behavior of the lubricant; T is the lubricant temperature; p is the

hydrodynamic pressure;  T , C1, C2 , C3 are the lubricant fluid constants. It is known that the major problem in the solution of the similar tasks is extremely low values of the film thickness (up to contact) in the areas close to the edges of the bearing (edge effect). Lubricants application with the load-carrying additives significantly reduces the edge effect. To simulate the edge effects including the multiple-viscosity oils properties, the model of the structured lubricant layer presented in [2] is used. It is based on idea of the irregular structure across the layer thickness. This irregularity is caused by interaction of the additives molecules with the journal and bushing materials. Viscosity is presented by the following function   y   y  y2     *  y    0   s  exp  1   exp  . lh 2    lh1   

Where  0 is the initial viscosity of the liquid at the infinite distance from a surface;  s is viscosity of the boundary layer (viscosity of the layer adsorbed on a surface); y is the coordinate in the direction along a normal to a friction surface; y1, y2 are the thicknesses of the boundary layers determined by minimization of the hydrodynamic friction forces; lh1 , lh 2 are the reference parameters various for each combination of the lubricant and the material of surfaces. The parameters of the model are defined by means of the original combined computational and experimental technique. More details are explained in [2, 3]. This model has allowed to appropriate quantity of the minimum film thickness value for the big-end connecting rod bearings which have a small film thickness. The implementation of the presented mathematical statement of the problem, taking into consideration the adequate experimental choice of the models parameters, will allow to increase the quality of the main bearings design of the multi-supporting crankshaft for an internal combustion engine. This will happen due to the simultaneous considering of misalignments of the journals and bearings axes, flexibility of a crankshaft and a crankcase and rheological behavior of the multiple-viscosity oils. References [1]

[2]

[3]

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Zadorozhnaya, E.A., Levanov, I.G. and Mukhortov, I.V., “Application of Non-Newtonian Models of Lubricating Fluids for Calculation of Heavy-Loaded Tribounits of Piston and Rotor Machines,”Friction and Greasing in Machines and Mechanisms, 7, 2011,22-30. Muchortov, I., Zadorojznaya, E.,Levanov, I., “Reological Model of a Boundary Layer of Lubricant,” STLE Annular Meeting & Exhibition, 15-19 May, 2011, Hilton Atlanta, Georgia (USA)2011, 235-241. Mukhortov, I.V., “Multimolecular adsorption lubricants and its integration in the theory fluid friction,”Bulletin SUSU: Mechanical Engineering Series, 31 (248), 2011, 62-67.

40th Leeds-Lyon Symposium on Tribology & Tribochemistry Forum 2013 September 4-6, 2013, Lyon, France

Research on Causes of Cavitation Generation on Textured Surface under Hydrodynamic Lubrication R. Tsuboi1*, A. Nakano1, S. Sasaki1 Department of Mechanical Engineering, Tokyo University of Science 6-3-1 Nijyuku, Katsusika-ku, Tokyo 125-8585, Japan *

Corresponding author for [email protected]

1. Abstract One of the effects of surface texturing under hydrodynamic lubrication is increasing load capacity. It is said that this effect is caused by generation of cavitation around the geometry by the surface texturing and presence of the cavity is observed by experiments. Considering the generation of the cavity, there are two kinds of cavitation phenomenon. One is vaporous cavitation, the other is gas cavitation. However, the detailed mechanism of cavitation on the textured surface is not clear since it is difficult to perform in-situ observation of the sliding surfaces. For this reason, numerical analyses were conducted to investigate the mechanism of the cavitation with cavitation models. However, it is considered that most of them are not accurate because the mechanisms of generation of cavitation are unclear. We think further discussion about cavitation is needed. The objective in our research is to verify the mechanism of generation of cavitation by using CFD (Computational Fluid Dynamics). A new model, growth of a bubble, is proposed and is applied for CFD analysis. In our simulations, a flow field is assumed to be two-dimensional, laminar and incompressible. Governing equations are Continuity and Navier-Stokes equations. These equations are numerically solved using marker and cell method (MAC). The computational domain and the dimensions of the dimple are illustrated in Figure 1. As boundary conditions, the parallel walls have relative velocity of 0.1, 0.5, 1.0 and 3.0 m/s. Pressure of inlet and outlet is atmospheric pressure, 101.3 kPa. In addition, as physical properties of working fluid, viscosity is 0.052 Pa s, and density is 826 kg/m3.

Fig. 1 Simulation Domain

Figure 2 shows maximum decrease of pressure. We can observe that minimum pressure is larger than saturation vapor pressure. Therefore, it is considered that vaporous cavitation does not occur. In addition, gas cavitation is not generated from the perspective of supersaturation. We propose a new model, growth of bubble, based on an assumption that bubbles generated by something except for the texture intrude the sliding surface. The growth of bubble is calculated by use of Young-Laplace equation and two-film model with Pressure field simulated by CFD. Parameters of the calculation of the bubble growth are listed in Table 1. Figure 3 shows the calculation results. The changes of bubble diameter caused by decrease of pressure are confirmed. We can observe that the increase of the bubble diameter when sliding velocity and gas solubility are high. Table 1 Parameter of Bubble Growth Initial Bubble Diameter db

[m]

h/2

Surface Tension



[dyne/cm]

36.0

Overall Mass Transfer Coefficient

KL

[m/s]

0.00016

Henry Coefficient

H

[Pa・m3/mol]

2028

Solubility of Gas

CA

[mol/m3]

Molar Mass Gas Constant Temperature

KL R T

[m/s] [J/kgK] [ºC]

50, 100, 200, 300 0.00016 8.314 20

Fig. 2 Decrease of Pressure (h=10m)

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Fig. 3 Growth of bubble with presented model

40th Leeds-Lyon Symposium on Tribology

Thermal Friction Analysis of a Single-Nut Preloaded Ball-Screw Chin-Chung WEIa, Jeng-Haur HORNGa (Tel/Fax:+88656315414/+88656312110,

mail: [email protected])

a

Department of Power Mechanical Engineering, National Formosa University, Yunlin, 63208, Taiwan

46, pp.880-898.

1. ABSTRAT High speed transmission table is wildly used in industry and its demand is increased. High speed ball-screw device is a major component. Traditional lubricant is oil used in a high speed ballscrew device. But now grease is a more convenient lubricant than oil and became more often used in high speed device. Operating in high speed condition brings high thermal effect, which lets viscosity of grease decreasing with temperature rising. This will let transmission performance of ball-screw device varies with operating time. The work of this paper is to establish a thermal elasticviscous hydrodynamic lubrication (EHL) analyzing model [1,2] for friction calculation. The thermal effect and the real reheology of grease are both considered in this model. Thickness of the oil film and friction force of each contact surface varying with operating conditions of ball-screw can be obtained and confirmed with driving torque of motor by experimental test. The study is useful in understanding thermal friction between ball and raceway.

900 rpm 240kgf

8

Driveing torque (N-m)

6

3000 rpm 240kgf

6.5

4

6.0

2

5.5

0

5.0

-2

4.5

-4

4.0

-6

3.5

-8

3.0

Temperature rising of nut (C)

3000 rpm 60kgf 7.0

-10 0

10

20

30

40

50

Experimental time (mins)

Figure 11500psi變溫變頻率掃描黏度比較圖 Driving torque of ball-screw 1200

viscosity ( Pa.s )

1000 50 rad/s 5 rad/s 0.5 rad/s 0.05 rad/s 0.03 rad/s

800 600 400 200 0 40

60

80

100

120

140

160

temperature(℃)

Figure 2 viscosity measurement result of Grease A

Friction Force 0.2402 N 0.491 N 0.724 N

9

1.2x10

-5

1.0x10

-6

8.0x10

8

9.0x10

-6

6.0x10 8

8

3.0x10

Normal Load 20 N 50 N 80 N

-6

4.0x10

Hydrodynamic Pressure (Pa)

-5

1.2x10

Film Thickness ( m)

9

1.5x10

6.0x10

9

1.8x10

-5

1.4x10

Grease Viscous : 1 Pa.s u1= 0.6 m/s; u2 = 2 m/s 

-5

Grease Viscous : 200 Pa.s u1= 0.6 m/s; u2 = 2 m/s 

9

1.6x10

9

Normal Load 80 N 140 N 180 N 220 N

1.4x10

9

1.2x10

9

1.0x10

Friction Force 2.06 N

8.0x10

8

-5

3.5x10

-5

-5

2.5x10

6.0x10

-5

2.0x10 8

4.0x10

-5

1.5x10

8

-6

2.0x10

2.0x10

-5

0.0

0.0

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-5

4.0x10

3.0x10

4.17 N 5.75 N 7.23 N

8

4.5x10

-4

-4.0x10

0.0 -4

-4

-2.4x10

-1.6x10

-5

-8.0x10

0.0

-5

8.0x10

-4

-3.0x10

-4

-2.0x10

-4

-1.0x10

0.0

-4

1.0x10

1.0x10 -4 2.0x10

Longitude Axis (m)

Longitude Axis (m)

(a) (b) Figure 3 lubrication and friction force varying with load. Theoretical Result Linear Curve Fitting Experiments

0.88

Equation y = a + b*x Adj. R-Squar 0.65872

0.86

D D

Intercept Slope

Value Standard Erro 0.87096 0.01013 -2.01818E5.6899E-5

0.84

0.82

0.80

0.78 0

200

400

Operating Distance (km)

Figure 4 Friction force versus contact conditions

Film Thickness ( m)

9

1.8x10

Torque of Ball Screw (N m)

3. REFERENCES 1. J.F. Lin and H.Y. Chu, 1991, "A numerical solution for calculating elastic deformation in elliptical-contact EHL of rough surface," ASME J. Tribol., 113, pp.12-21. 2. Kim, H., and Sadeghi, F., 1991, "Non-Newtonian Elastohydrodynamic Lubrication of Point Contact," ASME J. Tribol., 113, pp. 703–711. Wei, C.C. and Lai R.S., 2011, "Kinematical Analyses and Transmission Efficiency of a Preloaded Ball Screw Operating at High Rotational Speeds," Mechanism and Machine Theory,

10

900 rpm 60kgf

7.5

Hydrodynamic Pressure (Pa)

2. RESULT AND DISCUSSION In grease lubricating ball-screw system, driving torque is decreased before 10 mins, as shown in Figure 1, and also increases with raising rotational speeds. Temperature rising of nut is also increase with operating time. It means that contact temperature on ball and raceway is rising with time. The driving torque analyzing model is considered viscosity variation with thermal rising with different shear rate, as shown in Fig.2. The viscosity drops rapidly with temperature raising. Oil film and pressure distribution were calculated, as shown in Figs. 3(a) and (b) with different viscosities, 1 and 200 pa・s. Friction force can thus be obtained from different operating conditions and driving torque of ball-screw also can be calculated. If the viscosity of grease is 200 pa・s, minimum oil film is greater than 1.6×10-5 m, and it is also larger than roughness of raceway. Wear occurred at ball and raceway can thus be avoided. But friction forces, whose shown in Fig.3(b), are also ten times greater than those obtained from 1 pa・s. This reveals that high viscosity of grease brings high friction and thermal rising. The thermal effect also can decrease viscosity and lower friction force is obtained. Driving torque of motor on a linear driving table is composited by the friction torque of ball bearings, screw and linear guiders. The torque of screw is calculated by the analysis and compared with experimental data as shown in Fig.4. It shows that the torque is decreased with the increase of operating distance. This is owing to the wear is occurred at ball and raceway contact area. Friction heat was estimated in order to do the iteration of viscosity varying with contact temperature and find out the wear condition. Comparing the trend between theoretical and experiment data is the same, and the value of them is similar. The calculating error is due to the variation of asperity cannot be estimated properly. This is the next step in the research.

Screw Cooling system : on Torque Temp. rising

8.0

40th Leeds-Lyon Symposium on Tribology & Tribochemistry Forum 2013 September 4-6, 2013, Lyon, France

Tribological properties of halogen-free ionic liquids against sintered ceramics Y. Kondo1, S. Kawada1, S. Watanabe1, R. Tsuboi1 and S. Sasaki1* 1)

Tokyo University of Science, Niijyuku 6-3-1, Katsushika-ku, Tokyo 125-8585, Japan *

Corresponding author for [email protected]

shown in Table 2.

1. Introduction Ionic liquids (ILs) are expected to be used as new high-performance lubricants due to their low volatility and thermal stability. In general, it is known that their lubricity depend on whether they have halogen in their molecule structures. Halogen containing ILs exhibit excellent lubricity for metals; however at the same time, corrosive damage occurs on worn surfaces [1]. In addition, halogen-containing ionic liquids generate toxic gas including halide during sliding phase. On the other hands, halogen-free ILs can prevent such corrosive phenomena, however, the lubricity is very inferior compared with halogen-containing ILs. In the previous study [2], the tribological properties of halogen-free ILs against various hard materials were investigated, and it was reported the change of sliding materials can improve the lubricity of halogen-free ionic liquids. The lubricity of the combinations of sintered ceramics and halogen-free ILs exhibited good lubricity. In this study, the tribological properties and their mechanisms were investigated.

3. Results and discussions Figure 1 shows the friction and wear properties of ceramics using all lubricants. Al2O3 and Si3N4 lubricated with both ionic liquids and SiC lubricated with [BMIM][TCC] showed lower friction coefficient than that with PAO. In addition, the wear scar of the disk was not observed because the wear was too small. The friction behaviour of each ceramic lubricated with [BMIM] [TCC] and [EMIM] [DCN] are shown in Fig. 2. When [BMIM] [TCC] was used, few differences were observed between the friction behaviour of ceramics. On the other hand, when [EMIM] [DCN] was used, a remarkable difference was observed between the friction behaviour of SiC and the others. Though SiC had the smoothest surface of all ceramics, its friction coefficient showed the highest value. It is supposed that the differences of these tribological properties were due to the chemical effects rather than the physical effects such as the surface roughness.

2. Experimental conditions

4. References

The tribological properties of sintered ceramics, Al2O3, Si3N4 and SiC, were evaluated using a ball-on-disk reciprocating sliding tester. The physical properties of ceramics disks are shown in Table 1. The ball specimen was 10mm in diameter and made of AISI52100 (HRC 60). In this study, two kinds of halogen-free ionic liquids, [EMIM][DCN] and [BMIM][TCC], and PAO were adopted as lubricants. These viscosities are 7.62mPa·s, 11.13mPa·s and 8.55mPa·s at 50˚C respectively. The test conditions are

[1]

0.253

18

Si3N4

0.109

14

SiC

0.020

22

Table 2 Test conditions Frequency [Hz] Amplitude [mm]

50 1

Lubricant [µl]

30

Temperature [ºC] Load [N] Time [min]

50 50 60

0.3

0.3 (1) [EMIM][DCN]

(2) [BMIM][TCC]

(3) PAO

0.2 0.1 0

400

800

(1) (3) (2)

Al 2O3

(1) (3) (2)

(2)(3) (1)

Si3N4

Friction coefficient

Al2O3

Friction coefficient

Roughness Hardness Material [µm] [GPa]

0.4

Wear scar diameter [μm]

Table 1 Physical properties of ceramics

[2]

Y. Kondo et.al.,: “ Lubricity and corrosiveness of ionic liquids for steel-on-steel sliding Contacts”, Proc. of IMech E., Part J, 226(11) (2012) 991-1006 Y. Kondo et.al.,: “Study on Tribological property of Halogen-free Ionic Liquids for Hard Materials”, Proc. of JAST Tribo. Conf. Tokyo(2012) 373-374

Al2O3

Si3N4

SiC

with [BMIM][TCC]

Al2O3

Si3N4

SiC

0.2 SiC with [EMIM][DCN]

All ceramics with [BMIM][TCC]

0.1

SiC

Fig. 1 Friction and wear properties of ceramics using all lubricants

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with [EMIM][DCN]

Al2O3 and Si 3N4 with [EMIM][DCN]

0

1000 2000 Sliding time [s]

3000

Fig. 2 Friction behavior of ceramics using ionic liquids

40th Leeds-Lyon Symposium on Tribology & TribochemistryForum 2013 September 4-6, 2013, Lyon, France

1,3-Diketone Fluids and their Complexes with Iron Michael Walter1,2∗, Tobias Amann 2, Ke Li3, Andreas Kailer2, Jürgen Rühe3, and Michael Moseler 2 1)

Freiburg Materials Research Center, University of Freiburg, Stefan-Meier-Straße 21, 79104 Freiburg, Germany. 2)

IWM - Fraunhofer Institute for Mechanics of Materials, Woehlerstr. 11, 79108 Freiburg, Germany. 3)

Department of Microsystems Engineering, University of Freiburg, Georges-Köhler-Allee 103, D-79110 Freiburg, Germany. *

Corresponding author [email protected]

Tribological experiments with 1,3-diketone fluids in contact with iron surfaces show ultralow friction[1], which was suggested to be connected to the formation of iron complexes. In order to support this assumption, we calculate infrared and optical spectra of various substituted 1,3-diketones and their iron complexes using gradient corrected density functional theory (DFT). The description of the complexes requires the application of the DFT+U scheme for a correct prediction of the high spin state on the central iron atom. With this approach we obtain excellent agreement between experiment and simulation in infrared and optical spectra (see fig. 1), allowing for the determination of 1,3-diketone tautomeric forms [2]. The match in the spectra of the complex strongly supports the assumption of iron complex formation by these lubricants.

Fig. 1Comparison of simulated and experimental UV-Vis spectra. References [1] [2]

Amann, T., and Kailer, A. Tribology Letters 41, 2011,121–129 Walter, M., Amann, T., Li, K., Kailer, A, Rühe, J., and Moseler, M. J. Phys. Chem. A, submitted 2013

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40th Leeds-Lyon Symposium on Tribology & Tribochemistry Forum 2013 September 4-6, 2013, Lyon, France

Adsorption of fatty acids on steel and gold surfaces: An in-situ XPS study C. Matta1*, S. Loehle1, C. Minfray1, Th. Le Mogne1, J. M. Martin1, R. Iovine2 and A. Miyamoto3 1)

Laboratory of Tribology and System Dynamics, Ecole Centrale de Lyon, 36 avenue Guy de collongue, 69134 Ecully, France. 2) Total, Solaize Research Center, BP22 69360 Solaize, France. 3) New Industry Creation Hatchery Center, Tohoku University, 6-6-10 Aoba, Aramaki, Aoba-ku, Sendai 980-8579, Japan *

Corresponding author: [email protected]

1. Introduction Most of the traditional additives used in automotive lubrication, like ZDDP and MoDTC, are considered as source of pollution and are accused to have a major contribution to environmental concerns. Nowadays, with growing issue around the world on environment protection, these additives must be minimised or replaced with biodegradable molecules having the same efficiency while being friendly to the environment. In order to meet these requirements, automotive and oil industries are trying to develop new lubrication technologies based on biodegradable additives. Among these additives, fatty acids are widely used as friction modifiers in fuels and lubricating oils and could be good candidates to meet the environmentally concerns. Several studies have proved the efficiency of these additives under certain operating conditions [1-3] and many lubrication models have been proposed but none have been evidenced experimentally. In this study we investigate the adsorption of stearic acid and other fatty acids on different steel surfaces by using XPS analysis. The objective is a better understanding of the effect of substrate on their mechanism of action. 2. Methodology For the adsorption tests, metallic iron and pure iron oxide surfaces were prepared in situ by ion etching. Gold and AISI 52100 steel surfaces were also studied for comparison. After the surface preparation, the samples were transferred all together into the preparation chamber of the XPS analyzer and vapor of C18 fatty acid was introduced in the chamber for adsorption at different times. Afterwards the adsorbed layers were analysed by XPS to study the effect of substrate nature. 3. Results XPS analysis of adsorbed layers shows that the substrate nature influences the adsorption type. Stearic acid molecules seem to chemisorb via the COOH group on metallic iron but only physisorb on iron oxide and gold. No adsorption is detected on contaminated surfaces before etching (Fig.1). These results are in good agreement with computer simulation results presented in another paper of this conference.

Fig.1: C1s XPS spectrum of: a) Pure stearic acid powder, b) Metallic iron and c) Iron oxide adsorbed surfaces 4. Conclusion The adsorption mechanism of stearic acid and other fatty acids on steel and gold surfaces was studied by XPS technique. Results show that stearic acid adsorbs via the carboxylic group (COOH). Depending on the nature of the surface and its preparation, the type of the adsorption varies. Overall, these results are in good agreement with computer simulation studies presented in another paper of this conference. 5. References [1] Bowden, P. and Tabor, D., “The friction and lubrication of solids,” Oxford University Press. [2] Allen, C. M. and Drauglis, E., “Boundary layer lubrication: monolayer or multilayer,” Wear, 14, 1969, 363-384. [3] Sahoo, R. R. and Biswas, S. K., “Frictional response of fatty acid on steel,” Journal of colloid and Interface Science, 333, 2009, 707-718.

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40th Leeds-Lyon Symposium on Tribology &TribochemistryForum 2013 September 4-6, 2013, Lyon, France

Comparative study of tribologicalbehaviour of steel/steel and steel/nanocristallin diamond contacts lubricated by organomolybdenum and ZnDTP O. Gorbatchev1*, S. Fedry1, M.I. De Barros Bouchet1, Th. Le-Mogne1, R. Iovine2, J.M. Martin1 1)

Laboratoire de Tribologie et Dynamique des Systèmes, Ecole Centrale de Lyon, 69134 Ecully, France. 2) Centre de Recherche de Solaize, TOTAL, Supply & Marketing, BP22 Solaize, France *

Corresponding author for [email protected]

1. Introduction Nowadays, the control of energy consumption is a priority, especially for the automotive industry. The reduction of energy consumption of diesel engines can be reached through the minimization of friction losses of some engine parts, like the ring-piston-liner. Some authors blame this part to be responsible for 40% of friction losses in the entire diesel engine, particularly in case of mixed and boundary lubrication [1]. To overcome this problem, various chemical additives can be added to engine oil. These compounds interact with steel surfaces or coatings deposited on these surfaces and form protective layers to reduce friction coefficient between the two surfaces in contact. Fire segment, in his capacity as head segment is subjected to severe conditions and therefore to significant wear. That is why we propose to apply a coating of NanoCrystalline Diamond (NCD). Subsequently, it is needed to formulate a lubricant suitable for both steel/steel and steel/NCD contacts.

with heptane in an ultrasonic bath. Then,surface analyses were carried out inside and outside the tribofilm by X-Ray Photoelectron Spectroscopy (XPS), and Time Of Flight Secondary Ion Mass Spectrometry (TOF-SIMS). 4. Results Figure 1compares thesteady-state friction coefficientsobtained withthe PAO4 aloneand PAO4 with additives.It is clear thatthe presence of additives decreases friction in both cases, even if they appears more activeonferroussurfaces(see Fig. 1). Moreover, Organomolybdenum does not contain sulfurtherefor it is a more environmentally friendly additive. Fig. 1: Comparison of steady-state friction coefficient of steel/steel and steel/NCD contactslubricated with PAO4 only and with a lubricant composed of PAO4, Organomolybdenum and ZnDTP(II). 0,16 0,14 Steady-state fric on coefficient

2. Nanocrystalline diamond coatings Nanocrystallinediamond coatings were elaborated by MW-PECVD (Plasma Microwave-Enhanced Chemical Vapour Deposition) process and have unique properties in terms of resistance to wear, abrasion and corrosion and they can exhibit very low friction in certain conditions [2]. For this study, we selected a NCD coating combining both strong mechanical properties and very low surface roughness (see Table 1).

0,14 0,12 0,1 0,1

0,09

0,08

0,07

NCD/steel steel/steel

0,06 0,04 0,02 0

PAO4

PAO4+OrganoMo+ZnDTP(II)

Table 1 : Main properties of NCD coatings Gaseous mixture CH 4-CO2 50%

Diamond purity (%)

Hardness (GPa)

75

60±5

Biaxial modulus RMS (GPa) (nm) 550

20

3. Experimental details For tribological experiments, a reciprocating cylinder-on-flat tribometer was used to simulate the ring/cylinder contact geometry in thermal engines. Friction pairs were made of 100C6 steel cylinder and NCD-coated Ti-6Al-4V alloy flat. The wear track was 5 mm long, the temperature was 80°Cand the frequency used is 5Hz with the sinusoidal sliding speed A normal load of 50N ensures initially a maximal contact pressure of 270MPa.The lubricant is composed of grade 4 poly-alpha-olefin base oil, organomolybdenum friction modifier and zinc dialkyl-dithio-phosphate (ZnDTP) antiwear additives. After friction experiments, the samples were washed

6. Conclusion Inthis work,we would like to understand lubrication mechanism and explain differences between steel/steel and steel/NCD behavior. 5. References [1]

[2]

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K. Holmberg, P. Andersson, A. Erdemir, Global energy consumption due to friction in passenger cars, Tribol. Int. 47(2012) 221-234.. M.I. De Barros, and all., Tribological performance of diamond-coated Ti-6Al-4V alloy with respect to diamond characteristics, Surf. Coat. Technol., 127 (2000), p. 193.

40th Leeds-Lyon Symposium on Tribology &TribochemistryForum 2013 September 4-6, 2013, Lyon, France

Effect of Lubricant Chemistry on the Camshaft Friction and Follower Rotation RA. Mufti1*, M. Khurram1, F. Qureshi2, R. Zahid1, and J. Aslam1 1)

School of Mechanical and Manufacturing Engineering, National University of Sciences and Technology, H-12 Islamabad, Pakistan 2) The Lubrizol Corporation, 29400 Lakeland Boulevard, Wickliffe, Ohio 44092, USA * Corresponding author:[email protected]

1. Abstract

Lubricant technology is mainly driven by fuel economy, emissions and durability. Lubricant manufacturers and formulators are under constant pressure to develop products that would reduce fuel consumption and lower emissions while maintaining engine durability. This drive has resulted into the introduction of low viscosity lubricants [1] to reduce fluidfriction and has augmented the importance of friction modifiers to improve mixed to boundary lubrication friction. It is well known that engine valve train is one of the most challenging components to lubricate effectively due to the high contact loading at the cam-tappet interface of the direct acting valve train configuration. The contribution of frictional losses from the valve train is relatively low at low temperatures and high speeds but a significant impact on fuel economy can be seen at low speeds and high temperatures [2]. Lubricant viscosity has a major impact on the valve train performance. Lowering the viscosity increases the friction at the cam/tappet interface whereas the tappet-bore friction decreases as shear friction is more dominant in this region. The cam-tappet-bore friction has an impact on the rotation of the tappets and tappet rotation has an effect on the tappet wear and thus durability. With the introduction of low viscosity lubricants, maintaining the valve train component durability is one of the key challenges faced by automotive OEMs. Along with viscosity,friction modifiers also influence the cam/tappet friction. Friction modifiers reduce the boundary friction at the cam/tappet interface buttheir impact on tappet rotation needs to be investigated. In adirect acting cam/tappet configuration, the tappets are slightly offset from the cam and in some cases conical cam/dome tappets are used to facilitate rotation. Tappet rotation is important as it plays a vital role in reducing sliding friction but more importantly it encourages uniformwear. If for some reasons the tappets stop rotating catastrophic component failure can take please due to fatigue or sliding wear. To study the impact of lubricant rheology and chemistry on the valve train friction and tappet rotation, Mercedes Benz OM646engine head is instrumented for simultaneous measurement of these parameters(Fig1).The tappet rotation speed is

measured using magnetic gradiometer chip, a recently developed technique that allows the measurement of tappet rotation without the need to drill holes in the engine block for sensor installation.The engine valve train friction is measured using the online torque tube method previously implemented on heavy duty diesel engines [3] and now applied on the passenger car engine. The instrumentation of the engine head is carried out in such a way that components under investigation operate in original environment so that realistic behavior can be observed. With the use of advanced data acquisition system simultaneous measurement of friction and tappet rotation was made possible, providing an insight into the tappet friction and rotation relationship. Friction reduction improves fuel economy but it also reduces the traction required for tappet rotation. Tests carried out under different operating conditions clearly show the influence of lubricant chemistry on the engine valve train performance.

Fig1. Instrumented engine for camshaft friction and tappet rotation measurement. 2. References [1]

Taylor, R. I., Coy. R. C., “Improved Fuel Efficiency by Lubricant Design”IMechE J. of Engineering Tribology, 214, 1, 2000, 1-15.

[2]

Mufti, R. A., Priest, M., “Effect of Engine Operating Conditions and Lubricant Rheology on the Distribution of Losses in an Internal Combustion Engine,” ASME J. Tribology, 131, 4, 2009.

[3]

Mufti, R. A., “Experimental Technique of Evaluating Valve Train Performance of a Heavy Duty Diesel Engine,” IMechE J. of Engineering Tribology, 223, 3,2009, 425-436.

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40th Leeds-Lyon Symposium on Tribology &TribochemistryForum 2013 September 4-6, 2013, Lyon, France

Effects of iron oxide layers on adsorption mechanism of C18 fatty acid: A computational study Sophie Loehle1)*,Clotilde Minfray1), Christine Matta1), Thierry Le Mogne1), Jean-Michel Martin1), Raphaele Iovine2),Yukiko Obara3), Ryuji Miura3) and Akira Miyamoto3) 1)Laboratory of Tribology and System Dynamics, Ecole Centrale de Lyon, 36 avenue, Guy de Collongue 69134, Ecully Cedex, France 2) TOTAL, SolaizeResearch Center, BP22 – 69360 Solaize Cedex, France 3) New Industry Creation Hatchery Center, Tohoku University, 6-6-10 Aoba, Aramaki, Aoba-ku, Sendai 980-8579, Japan *Corresponding author: [email protected]

1. Introduction

In the automotive industry, the control of friction and wear by the lubricant in thermal engines is one of the most important issues for fuel economy. Therefore, it is needed to better understand the nature of tribochemical reactions in order to design and develop better lubricants that also address environmental requirements. C18 fatty acids seem to be good candidates to achieve this target. In this study, we have investigated the adsorption mechanism of some organic friction modifiers on different iron-based surfaces.

Orientation of the molecule toward the Fe2O3 surface has an impact on the adsorption mechanism. Depending on the angle between the acid group and Fe2O3, molecule can be physisorbed as shown on figure 1 or chemisorbed through the acid group. Table 1: Adsorption mechanism summary regarding the surface type for single molecule adsorption

Iron-based surfaces

Adsorption mechanism

Pure Iron

Chemisorption

Iron Oxide Fe2O3

Physisorption/Chemisorption

Iron Oxide FeOOH

No adsorption/Physisorption

2. Material and methods

The computational chemistry approach can give us dynamic information at the atomistic and electronic levels. An ultra-accelerated quantum chemical MD (UA-QCMD) simulator “Colors-Ryudo” has been developed in order to deal with chemical reaction dynamics for large complex systems [1] . We have applied these methods to study the adsorption mechanismof C18 (saturated and unsaturated) fatty acid e.g. stearic, oleic and linoleic acids which are organic friction modifiers on different iron based surfaces choose with respect to a steel surface study[2]: pure iron, iron oxide Fe2O3 and iron oxide FeOOH. 3. Results

In this work, different orientations of fatty acid will be studied on each iron based surfaces. Main results are gathered on Table 1. Molecule is always chemisorbed through the acid groupon pure iron. If the position is imposed, molecule is physisorbed on FeOOH but free molecule doesn’t interact with FeOOH.

Figure 1:Adsorption of Stearic acid on iron oxide Fe2O3 surface at 50 °C studied bu UA-QCMD: initial step (left snapshot), final step (right snapshot)

4. Conclusion

The adsorption mechanism of C18 fatty acids on iron based surfaces has been successfully studied by UA-QCMD. The most the iron surface is oxidized; the less it is reactive with the fatty acid. These results can be confirmed by experimental surface characterizations. 5. References [1] Korshed A. et al. Cat. Today 164 (2011) 9–15 [2] Olla M et al. Surf.Int.Analysis, 38 (2006) 964-974

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40th Leeds-Lyon Symposium on Tribology &TribochemistryForum 2013 September 4-6, 2013, Lyon, France

Experimental analysis of tribological properties of chemically modified bio-based lubricant with nanoparticle additives N.W.M. Zulkifli1*, M.A.Kalam1, H.H. Masjuki1 and R. Yunus2 1

2

Department of Mechanical Engineering, University of Malaya, Kuala Lumpur 50603, Malaysia Institute of Advanced Technology, University Putra Malaysia, 43400 Serdang, Selangor, Malaysia * Corresponding author: [email protected]

1. Introduction

2.2. Experimental procedure The test method to investigate the tribological properties focused on running in effect of lubricant was fourball machine. The test conditions were 392 N, rotational speed of 1770 rpm and operation time of 10 minutes with room temperature.

There has been an enormous amount of research conducted on using vegetable oil as a lubricant. Vegetable oil has a positive impact to use as a lubricant has high biodegradability and reduces friction. In addition to that, the uncertainty of the crude oil supply, increasing crude oil prices, and issues related to environmental makes the vegetable oil more valued. However, vegetable oil has some drawback such as low oxidation stability, and low thermal stability. Several techniques have been done to overcome the potential problem produced by vegetable oil such blending with other diluents such as polyalphaolephin, by chemical modification such as esterification, transesterification and epoxidized vegetable oil and adding additives. It has been well known that addition of nanoparticle to lubricant is effective in reducing wear and friction.The mechanisms of friction-reduction of nanoparticles in lubricant have been reported as the colloidal effect, rolling effect, protective film and third body [1]. Therefore, this study is conducted to study the interaction between nanoparticles and chemically modified vegetable oil in terms of friction and wear.

3. Results and Discussion The friction coefficients of the lubricant with and without nanoparticles are shown in Fig.1. The friction coefficient containing WS2 and MoS2 are lower than lubricant without nanoparticles. This may cause by the nanoparticle acting as third body and protect the surface [3]. Coefficient of Friction

0,12 0,1

Paraffin Paraffin +MoS2 TMP ester+ WS2

Paraffin +WS2 TMP ester TMP etser+MoS2

0,08 0,06 0,04 0,02 0 Running in

Steady state

Fig.1 Coefficient of friction of lubricant for different condition

2. Methodology 2.1. Constituents of tested oil The nanoparticles WoS and MoSwere provided by Sigma Aldrich. The sizes of nanoparticles were less than