E NGINEERING TRIBOLOGY ENGINEERING TRIBOLOGY Gwidon W. Stachowiak Department of Mechanical and Materials Engineering, University of Western Australia, Australia Andrew W. Batchelor Department of Mechanical and Materials Engineering, University of Western Australia, Australia To the most important persons in our lives Grazyna Stachowiak Gwidon (Jr.) Stachowiak and Valli M. Batchelor Vicky & Diana Batchelor CONTENTS 1 INTRODUCTION 1 1.1 Background 1 1.2 Meaning of tribology 2 Lubrication 3 Wear 5 1.3 Cost of friction and wear 5 1.4 Summary 7 References 8 2 PHYSICAL PROPERTIES OF LUBRICANTS 11 2.1 Introduction 11 2.2 Oil viscosity 11 Dynamic viscosity 12 Kinematic viscosity 13 2.3 Viscosity temperature relationship 13 Viscosity-temperature equations 14 Viscosity-temperature chart 14 2.4 Viscosity index 15 2.5 Viscosity pressure relationship 16 2.6 Viscosity-shear rate relationship 22 Pseudoplastic behaviour 22 Thixotropic behaviour 24 2.7 Viscosity measurements 24 Capillary viscometers 24 Rotational viscometers 26 · Rotating cylinder viscometer 27 · Cone on plate viscometer 28 Other viscometers 29 2.8 Viscosity of mixtures 30 2.9 Oil viscosity classification 31 VIII ENGINEERING TRIBOLOGY SAE viscosity classification 31 ISO viscosity classification 33 2.10 Lubricant density and specific gravity 33 2.11 Thermal properties of lubricants 34 Specific heat 34 Thermal conductivity 35 Thermal diffusivity 35 2.12 Temperature characteristics of lubricants 35 Pour point and cloud point 36 Flash point and fire point 37 Volatility and evaporation 37 Oxidation stability 38 Thermal stability 39 Surface tension 40 Neutralization number 42 Carbon residue 43 2.13 Optical properties of lubricants 43 Refractive index 43 2.14 Additive compatibility and solubility 44 Additive compatibility 44 Additive solubility 44 2.15 Lubricant impurities and contaminants 44 Water content 44 Sulphur content 45 Ash content 45 Chlorine content 45 2.16 Solubility of gases in oils 45 2.17 Summary 48 References 48 3 LUBRICANTS AND THEIR COMPOSITION 51 3.1 Introduction 51 3.2 Mineral oils 52 Sources of mineral oils 52 Manufacture of mineral oils 54 Types of mineral oils 56 · Chemical forms 56 · Sulphur content 57 · Viscosity 57 CONTENTS IX 3.3 Synthetic oils 57 Manufacturing of synthetic oils 58 Hydrocarbon synthetic lubricants 60 · Polyalphaolefins 60 · Polyphenyl ethers 60 · Esters 60 · Cycloaliphatics 61 · Polyglycols 61 Silicon analogues of hydrocarbons 62 · Silicones 62 · Silahydrocarbons 62 Organohalogens 62 · Perfluoropolyethers 63 · Chlorofluorocarbons 63 · Chlorotrifluoroethylenes 63 · Perfluoropolyalkylethers 63 3.4 Emulsions and aqueous lubricants 65 Manufacturing of emulsions 65 Characteristics 65 Applications 66 3.5 Greases 66 Manufacturing of greases 66 Composition 67 · Base oils 67 · Thickener 67 · Additives 68 · Fillers 69 Lubrication mechanism of greases 69 Grease characteristics 72 · Consistency of greases 72 · Mechanical stability 73 · Drop point 74 · Oxidation stability 75 · Thermal stability 75 · Evaporation loss 76 · Grease viscosity characteristics 76 Classification of greases 78 Grease compatibility 80 Degradation of greases 80 X ENGINEERING TRIBOLOGY 3.6 Lubricant additives 81 Wear and friction improvers 82 · Adsorption or boundary additives 82 · Anti-wear additives 83 · Extreme pressure additives 85 Anti-oxidants 86 · Oil oxidation 86 · Oxidation inhibitors 88 Corrosion control additives 91 Contamination control additives 92 Viscosity improvers 93 Pour point depressants 95 Foam inhibitors 95 Interference between additives 95 3.7 Summary 96 References 97 4 HYDRODYNAMIC LUBRICATION 101 4.1 Introduction 101 4.2 Reynolds equation 101 Simplifying assumptions 103 Equilibrium of an element 103 Continuity of flow in a column 107 Simplifications to the Reynolds equation 109 · Unidirectional velocity approximation 109 · Steady film thickness approximation 109 · Isoviscous approximation 110 · Infinitely long bearing approximation 110 · Narrow bearing approximation 111 Bearing parameters predicted from Reynolds equation 113 · Pressure distribution 113 · Load capacity 113 · Friction force 114 · Coefficient of friction 115 · Lubricant flow 115 Summary 115 4.3 Pad bearings 116 Infinite linear pad bearing 116 · Bearing geometry 116 [...]... Vol 31, 19 86, pp 883-888 and Vol 28, 19 83, pp 53-56 respectively Figures 14 .2 and 15 .2: Royal Society of London From Proceedings of the Royal Society of London, Vol 394, 19 84, pp 16 1 -18 1 and Vol 230, 19 55, pp 5 31- 548 respectively Figure 16 .6: The American Society of Mechanical Engineers From Transactions of the ASME, Journal of Lubrication Technology, Vol 10 1, 19 79, pp 212 - 219 Figures 11 . 41 and 16 .22... of fretting 607 Means of controlling fretting 608 15 .3 Melting wear 609 15 .4 Wear due to electrical discharges 611 15 .5 Diffusive wear 612 15 .6 Impact wear 613 15 .7 Summary 615 References 16 616 WEAR OF NON-METALLIC MATERIALS 619 16 .1 Introduction 619 16 .2 Tribology of polymers 619 Sliding wear of polymers, transfer layers on a harder counterface 6 21 Influence of counterface roughness, hardness and... distribution 11 7 · Load capacity 11 9 · Friction force 12 0 · Coefficient of friction 12 3 · Lubricant flow rate 12 4 Infinite Rayleigh step bearing 12 5 Other wedge geometries of infinite pad bearings 12 8 · Tapered land wedge 12 8 · Parabolic wedge 12 9 · Parallel surface bearings 13 0 · Spiral groove bearing 13 1 Finite pad bearings Pivoted pad bearing 13 3 Inlet boundary conditions in pad bearing analysis 4.4 13 2 13 5... wedges 13 7 Bearing geometry 13 8 Pressure distribution 13 8 · Full-Sommerfeld boundary condition 14 0 · Half-Sommerfeld boundary condition 14 1 · Reynolds boundary condition 14 3 Load capacity 4.5 14 4 Journal bearings 14 6 Evaluation of the main parameters 14 6 · Bearing geometry 14 6 · Pressure distribution 14 8 · Load capacity 14 9 · Friction force 15 4 · Coefficient of friction 15 5 · Lubricant flow rate 15 6 Practical... Germany, 19 76 8 Strategy for Energy Conservation Through Tribology, ASME, New York, November, 19 77 INTRODUCTION 9 9 L.S Dake, J.A Russell and D.C Debrodt, A Review of DOE ECT Tribology Surveys, Transactions ASME, Journal of Tribology, Vol 10 8, 19 86, pp 497-5 01 10 H.P Jost and J Schofield, Energy Savings Through Tribology: A Techno-Economic Study, Proc Inst Mech Engrs., London, Vol 19 5, No 16 , 19 81, pp 15 1 -17 3... squeeze films 19 1 Pressure distribution 19 2 Load capacity 19 3 Squeeze time 19 4 Cavitation and squeeze films 19 5 Microscopic squeeze film effects between rough sliding surfaces 19 6 4 .10 Porous bearings 19 6 4 .11 Summary 19 7 4.9 References 5 19 8 COMPUTATIONAL HYDRODYNAMICS 2 01 5 .1 Introduction 2 01 5.2 Non-dimensionalization of the Reynolds equation 2 01 5.3 The Vogelpohl parameter 202 5.4 Finite difference... previously published in Wear, Vol 11 3, 19 86, pp 305-322 and Vol 17 , 19 71, pp 3 01- 312 respectively 1 1 .1 I N T R O D U C T I O N BACKGROUND Tribology in a traditional form has been in existence since the beginning of recorded history There are many well documented examples of how early civilizations developed bearings and low friction surfaces [1] The scientific study of tribology also has a long history,... journal bearings 15 8 · Lubricant supply 15 9 · Cavitation 16 3 · Journal bearings with movable pads 16 4 · Journal bearings incorporating a Rayleigh step 16 4 · Oil whirl or lubricant caused vibration 16 5 · Rotating load 16 7 · Tilted shafts 16 9 · Partial bearings 17 0 · Elastic deformation of the bearing 17 1 XII ENGINEERING TRIBOLOGY · 4.6 Infinitely long approximation in journal bearings 17 2 Thermal effects... bearing 18 1 4.7 Limits of hydrodynamic lubrication 18 2 4.8 Hydrodynamic lubrication with non-Newtonian fluids 18 4 Turbulence and hydrodynamic lubrication 18 4 Hydrodynamic lubrication with non-Newtonian lubricants 18 5 Inertial effects in hydrodynamics 18 6 Compressible fluids 18 7 Compressible hydrodynamic lubrication in gas bearings 18 9 Reynolds equation for squeeze films 19 1 Pressure distribution 19 2 Load... on erosive wear rate 511 Effect of particle shape, hardness, size and flux rates on erosive wear rate 512 Erosive wear by liquid 513 Effect of temperature on erosive wear 515 Effect of erosion media on erosive wear 516 Erosive wear resistance of materials 518 · Erosive wear resistance of steels 520 · Erosive wear resistance of polymers 5 21 · 11 .4 507 Control of abrasive wear 11 .3 506 Erosive wear of . equation 11 3 · Pressure distribution 11 3 · Load capacity 11 3 · Friction force 11 4 · Coefficient of friction 11 5 · Lubricant flow 11 5 Summary 11 5 4.3 Pad bearings 11 6 Infinite linear pad bearing 11 6 ·. CONTENTS 1 INTRODUCTION 1 1 .1 Background 1 1.2 Meaning of tribology 2 Lubrication 3 Wear 5 1. 3 Cost of friction and wear 5 1. 4 Summary 7 References 8 2 PHYSICAL PROPERTIES OF LUBRICANTS 11 2 .1 Introduction. LUBRICATION 10 1 4 .1 Introduction 10 1 4.2 Reynolds equation 10 1 Simplifying assumptions 10 3 Equilibrium of an element 10 3 Continuity of flow in a column 10 7 Simplifications to the Reynolds equation 10 9 ·