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 |  موضوع: كتاب Engineering Tribology الأربعاء 05 فبراير 2014, 7:58 pm | |
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Engineering Tribology 2E
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
ويتناول الموضوعات الأتية :
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
VIIIENGINEERING 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
CONTENTS XI
· Pressure distribution 117
· Load capacity 119
· Friction force 120
· Coefficient of friction 123
· Lubricant flow rate 124
Infinite Rayleigh step bearing 125
Other wedge geometries of infinite pad bearings 128
· Tapered land wedge 128
· Parabolic wedge 129
· Parallel surface bearings 130
· Spiral groove bearing 131
Finite pad bearings 132
Pivoted pad bearing 133
Inlet boundary conditions in pad bearing analysis 135
4.4 Converging-diverging wedges 137
Bearing geometry 138
Pressure distribution 138
· Full-Sommerfeld boundary condition 140
· Half-Sommerfeld boundary condition 141
· Reynolds boundary condition 143
Load capacity 144
4.5 Journal bearings 146
Evaluation of the main parameters 146
· Bearing geometry 146
· Pressure distribution 148
· Load capacity 149
· Friction force 154
· Coefficient of friction 155
· Lubricant flow rate 156
Practical and operational aspects of journal bearings 158
· Lubricant supply 159
· Cavitation 163
· Journal bearings with movable pads 164
· Journal bearings incorporating a Rayleigh step 164
· Oil whirl or lubricant caused vibration 165
· Rotating load 167
· Tilted shafts 169
· Partial bearings 170
· Elastic deformation of the bearing 171
XII ENGINEERING TRIBOLOGY
· Infinitely long approximation in journal bearings 172
4.6 Thermal effects in bearings 172
Heat transfer mechanisms in bearings 173
· Conduction 174
· Convection 174
· Conducted/convected heat ratio 175
Isoviscous thermal analysis of bearings 176
· Iterative method 176
· Constant flow method 178
Non-isoviscous thermal analysis of bearings with locally varying viscosity 178
Multiple regression in bearing analysis 179
Bearing inlet temperature and thermal interaction between pads of a
Michell bearing 181
4.7 Limits of hydrodynamic lubrication 182
4.8 Hydrodynamic lubrication with non-Newtonian fluids 184
Turbulence and hydrodynamic lubrication 184
Hydrodynamic lubrication with non-Newtonian lubricants 185
Inertial effects in hydrodynamics 186
Compressible fluids 187
Compressible hydrodynamic lubrication in gas bearings 189
4.9 Reynolds equation for squeeze films 191
Pressure distribution 192
Load capacity 193
Squeeze time 194
Cavitation and squeeze films 195
Microscopic squeeze film effects between rough sliding surfaces 196
4.10 Porous bearings 196
4.11 Summary 197
References 198
5 COMPUTATIONAL HYDRODYNAMICS 201
5.1 Introduction 201
5.2 Non-dimensionalization of the Reynolds equation 201
5.3 The Vogelpohl parameter 202
5.4 Finite difference equivalent of the Reynolds equation 204
Definition of solution domain and boundary conditions 206
Calculation of pressure field 207
Calculation of dimensionless friction force and friction coefficient 207
Numerical solution technique for Vogelpohl equation 210
CONTENTS XIII
5.5 Numerical analysis of hydrodynamic lubrication in idealized journal
and partial arc bearings 210
Example of data from numerical analysis, the effect of shaft misalignment 211
5.6 Numerical analysis of hydrodynamic lubrication in a real bearing 216
5.6.1 Thermohydrodynamic lubrication 216
Governing equations and boundary conditions in
thermohydrodynamic lubrication 217
· Governing equations in thermohydrodynamic lubrication for a
one-dimensional bearing 218
· Thermohydrodynamic equations for the finite pad bearing 221
· Boundary conditions 222
Finite difference equations for thermohydrodynamic lubrication 223
Treatment of boundary conditions in thermohydrodynamic lubrication 226
Computer program for the analysis of an infinitely long pad bearing in
the case of thermohydrodynamic lubrication 227
Example of the analysis of an infinitely long pad bearing in the case of
thermohydrodynamic lubrication 228
5.6.2 Elastic deformations in a pad bearing 231
Computer program for the analysis of an elastically deforming onedimensional pivoted Michell pad bearing 233
Effect of elastic deformation of the pad on load capacity and film thickness 233
5.6.3 Cavitation and film reformation in grooved journal bearings 236
Computer program for the analysis of grooved 360° journal bearings 240
Example of the analysis of a grooved 360° journal bearing 240
5.6.4 Vibrational stability in journal bearings 246
Determination of stiffness and damping coefficients 246
Computer program for the analysis of vibrational stability in a partial arc
journal bearing 251
Example of the analysis of vibrational stability in a partial arc journal bearing 251
5.7 Summary 254
References 254
6 HYDROSTATIC LUBRICATION 257
6.1 Introduction 257
6.2 Hydrostatic bearing analysis 258
Flat circular hydrostatic pad bearing 258
· Pressure distribution 258
· Lubricant flow 259
· Load capacity 259
· Friction torque 260
XIVENGINEERING TRIBOLOGY
· Friction power loss 262
Non-flat circular hydrostatic pad bearings 262
· Pressure distribution 263
· Lubricant flow 264
· Load capacity 265
· Friction torque 265
· Friction power loss 265
6.3 Generalized approach to hydrostatic bearing analysis 266
Flat circular pad bearings 266
Flat square pad bearings 266
6.4 Optimization of hydrostatic bearing design 267
Minimization of power 267
· Low speed recessed bearings 269
· High speed recessed bearings 269
Control of lubricant film thickness and bearing stiffness 270
· Stiffness with constant flow method 271
· Stiffness with capillary restrictors 271
· Stiffness with an orifice 273
· Stiffness with pressure sensors 274
6.5 Aerostatic bearings 275
Pressure distribution 276
Gas flow 276
Load capacity 277
Friction torque 277
Power loss 278
6.6 Hybrid bearings 278
6.7 Stability of hydrostatic and aerostatic bearings 278
6.8 Summary 279
References 279
7 ELASTOHYDRODYNAMIC LUBRICATION 281
7.1 Introduction 281
7. 2 Contact stresses 282
Simplifying assumptions to Hertz's theory 282
Stress status in static contact 283
Stress status in lubricated rolling and sliding contacts 283
7.3 Contact between two elastic spherical or spheroidal bodies 284
Geometry of contacting elastic bodies 285
· Two elastic bodies with convex surfaces in contact 286
CONTENTS XV
· Two elastic bodies with one convex and one flat surface in contact 287
· Two elastic bodies with one convex and one concave surface in
contact 288
Contact area, pressure, maximum deflection and position of the
maximum shear stress 289
· Contact between two spheres 289
· Contact between a sphere and a plane surface 292
· Contact between two parallel cylinders 294
· Contact between two crossed cylinders with equal diameters 297
· Elliptical contact between two elastic bodies, general case 299
Total deflection 304
7.4 Elastohydrodynamic lubricating films 305
Effects contributing to the generation of elastohydrodynamic films 306
· Hydrodynamic film formation 306
· Modification of film geometry by elastic deformation 306
· Transformation of lubricant viscosity and rheology under pressure 307
Approximate solution of Reynolds equation with simultaneous elastic
deformation and viscosity rise 307
Pressure distribution in elastohydrodynamic films 311
Elastohydrodynamic film thickness formulae 312
Effects of the non-dimensional parameters on EHL contact pressures and
film profiles 313
· Effect of the speed parameter 313
· Effect of the materials parameter 314
· Effect of load parameter 314
· Effect of ellipticity parameter 315
Lubrication regimes in EHL - film thickness formulae 316
· Isoviscous-rigid 317
· Piezoviscous-rigid 318
· Isoviscous-elastic 318
· Piezoviscous-elastic 318
Identification of the lubrication regime 319
Elastohydrodynamic film thickness measurements 319
7.5 Micro-elastohydrodynamic lubrication and mixed or partial EHL 322
Partial or mixed EHL 323
Micro-elastohydrodynamic lubrication 325
7.6 Surface temperature at the conjunction between contacting solids and
its effect on EHL 327
Calculation of surface conjunction temperature 328
· Flash temperature in circular contacts 331
XVIENGINEERING TRIBOLOGY
· Flash temperature in square contacts 331
· Flash temperature in line contacts 334
True flash temperature rise 335
Frictional temperature rise of lubricated contacts 339
Mechanism of heat transfer within the EHL film 341
Effect of surface films on conjunction temperatures 342
Measurements of surface temperature in the EHL contacts 342
7.7 Traction and EHL 343
A simplified analysis of traction in the EHL contact 346
Non-Newtonian lubricant rheology and EHL 348
EHL between meshing gear wheels 350
7.8 Summary 352
References 352
8 BOUNDARY AND EXTREME PRESSURE LUBRICATION 357
8.1 Introduction 357
8.2 Low temperature - low load lubrication mechanisms 359
8.3 Low temperature - high load lubrication mechanisms 360
Model of adsorption on sliding surfaces 361
· Physisorption 362
· Chemisorption 364
· Influence of the molecular structure of the lubricant on
adsorption lubrication 365
· Influence of oxygen and water 369
· Dynamic nature of adsorption under sliding conditions 371
· Mixed lubrication and scuffing 372
· Metallurgical effects 379
· Interaction between surfactant and carrier fluid 380
8.4 High temperature - medium load lubrication mechanisms 381
Chain matching 381
Thick films of soapy or amorphous material 384
· Soap layers 384
· Amorphous layers 385
8.5 High temperature - high load lubrication mechanisms 388
Model of lubrication by sacrificial films 389
Additive reactivity and its effect on lubrication 390
Nascent metallic surfaces and accelerated film formation 393
Influence of oxygen and water on the lubrication mechanism by
sacrificial films 395
CONTENTS XVII
Mechanism of lubrication by milder E.P. Additives 398
Function of active elements other than sulphur 398
Lubrication with two active elements 399
Temperature distress 401
Speed limitations of sacrificial film mechanism 403
Tribo-emission from worn surfaces 403
8.6 Boundary and E.P. lubrication of non-metallic surfaces 404
8.7 Summary 404
References 405
9 SOLID LUBRICATION AND SURFACE TREATMENTS 411
9.1 Introduction 411
9.2 Lubrication by solids 411
9.2.1 Lubrication by lamellar solids 412
Friction and wear characteristics of lamellar solids 415
· Graphite and molybdenum disulphide 415
· Carbon-based materials other than graphite 419
· Minor solid lubricants 420
9.2.2 Reduction of friction by soft metallic films 421
Reduction of friction by metal oxides at high temperatures 422
9.2.3 Deposition methods of solid lubricants 422
Traditional methods of solid lubricant deposition 423
Modern methods of solid lubricant deposition 423
Solid lubricants as additives to oils and polymers 424
9.3 Wear resistant coatings and surface treatments 426
9.3.1 Techniques of producing wear resistant coatings 427
Coating techniques dependent on vacuum or gas at very low pressure 427
· Physical vapour deposition 427
· Chemical vapour deposition 430
· Physical-chemical vapour deposition 430
· Ion implantation 431
Coating processes requiring localized sources of intense heat 432
· Surface welding 432
· Thermal spraying 433
· Laser surface hardening and alloying 436
Coating processes based on deposition in the solid state 436
Miscellaneous coating processes 438
Application of coatings and surface treatments in wear and friction control 438
Characteristics of wear resistant coatings 439
XVIIIENGINEERING TRIBOLOGY
9.4 Summary 442
References 442
10 FUNDAMENTALS OF CONTACT BETWEEN SOLIDS 447
10.1 Introduction 447
10.2 Surfaces of solids 447
Surfaces at a nano scale 448
Surface topography 449
Characterization of surface topography 452
· Characterization of surface topography by statistical parameters 452
Multi-scale characterization of surface topography 455
· Characterization of surface topography by Fourier transform 455
· Characterization of surface topography by wavelets 456
· Characterization of surface topography by fractals 457
Optimum surface roughness 460
10.3 Contact between solids 461
Model of contact between solids based on statistical parameters of rough
surfaces 462
Model of contact between solids based on the fractal geometry of rough
surfaces 465
Effect of sliding on contact between solid surfaces 467
10.4 Friction and wear 468
Onset of sliding and mechanism of stick-slip 469
Structural differences between static and sliding contacts 471
Friction and other contact phenomena in rolling 473
Concentration of frictional heat at the asperity contacts 476
Wear between surfaces of solids 477
10.5 Summary 478
References 478
11 ABRASIVE, EROSIVE AND CAVITATION WEAR 483
11.1 Introduction 483
11.2 Abrasive wear 483
Mechanisms of abrasive wear 484
Modes of abrasive wear 486
Analytical models of abrasive wear 487
Abrasivity of particles 494
Abrasive wear resistance of materials 499
· Abrasive wear resistance of steels 502
· Abrasive wear resistance of polymers and rubbers 504
CONTENTS XIX
· Abrasive wear resistance of ceramics 505
Effect of temperature on abrasive wear 506
Effect of moisture on abrasive wear 507
Control of abrasive wear 507
11.3 Erosive wear 509
Mechanisms of erosive wear 509
Effect of impingement angle and impact speed 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 521
· Erosive wear of ceramics and cermets 523
11.4 Cavitation wear 524
Mechanism of cavitation wear 524
Cavitation wear resistance of materials 525
11.5 Summary 526
References 527
12 ADHESION AND ADHESIVE WEAR 533
12.1 Introduction 533
12.2 Mechanism of adhesion 533
Metal-metal adhesion 533
Metal-polymer adhesion 536
Metal-ceramic adhesion 537
Polymer-polymer and ceramic-ceramic adhesion 537
Effects of adhesion between wearing surfaces 538
· Friction due to adhesion 538
· Junction growth between contacting asperities as a cause of
extreme friction 539
· Seizure and scuffing 542
· Asperity deformation and formation of wear particles 542
· Transfer films 544
12.3 Control of the adhesive wear 548
Contaminant layers formed due to surface oxidation and bulk impurities 549
Lubricants 549
Favourable combinations of sliding materials 550
XX ENGINEERING TRIBOLOGY
12.4 Summary 550
References 550
13 CORROSIVE AND OXIDATIVE WEAR 553
13.1 Introduction 553
13.2 Corrosive wear 553
Transition between corrosive and adhesive wear 557
Synergism between corrosive and abrasive wear 559
Tribochemical polishing 560
13.3 Oxidative wear 560
Kinetics of oxide film growth on metals at high and low temperatures 561
· Oxidative wear at high sliding speeds 562
· Oxidative wear at low sliding speeds 563
· Oxidative wear at high temperature and stress 564
· Oxidative wear at low temperature applications 565
· Transition between oxidative and adhesive wear 566
· Oxidative wear under lubricated conditions 566
Means of controlling corrosive and oxidative wear 567
13.4 Summary 567
References 568
14 FATIGUE WEAR 571
14.1 Introduction 571
14.2 Fatigue wear during sliding 572
Surface crack initiated fatigue wear 573
Subsurface crack initiated fatigue wear 575
Effect of lubrication on fatigue wear during sliding 577
Plastic ratchetting 578
14.3 Fatigue wear during rolling 579
Causes of contact fatigue 580
· Asperity contact during EHL and the role of debris in the lubricant
in contact fatigue 580
· Material imperfections 581
Self-propagating nature of contact fatigue cracks 581
Subsurface and surface modes of contact fatigue 581
Effect of lubricant on contact fatigue 585
Hydraulic pressure crack propagation 585
Chemical effects of lubricant additives, oxygen and water on contact fatigue 586
Materials effect on contact fatigue 587
CONTENTS XXI
Influence of operating conditions on rolling wear and contact fatigue 588
14.4 Means of controlling fatigue wear 589
14.5 Summary 589
References 590
15 FRETTING AND MINOR WEAR MECHANISMS 593
15.1 Introduction 593
15.2 Fretting wear 594
Microscopic movements within the contact under applied loads 594
· Elastic model for fretting contacts 594
· Elasto-plastic model for fretting contacts 596
Effect of amplitude and debris retention on fretting wear 597
Environmental effects on fretting wear 599
Effects of temperature and lubricants on fretting 602
Effect of materials properties and surface finish on fretting 604
Fretting fatigue 604
Practical examples 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 616
16 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 621
Influence of counterface roughness, hardness and material type on
transfer films and associated wear and friction of polymers 622
· Counterface hardness 623
· Counterface roughness 623
· Counterface surface energy 626
Influence of temperature on polymer wear and friction 626
· Limit on frictional temperature rise imposed by surface melting 627
· Effect of high frictional temperatures and sliding speeds on wear 630
· Combined effect of high surface roughness and elevated contact
temperature on wear 631
Fatigue wear of polymers and long term wear kinetics 633
XXII ENGINEERING TRIBOLOGY
Visco-elasticity and the rubbery state 634
Friction and wear in the rubbery state 635
· Schallamach waves 635
· Visco-elasticity and friction of rubbers 636
· Wear mechanisms particular to rubbery solids 637
Effect of lubricant, corrosive agents and microstructure on wear and
friction of polymers 638
· Effects of lubricants 638
· Effects of corrosive agents 639
· Effect of oxidizing and biochemical reagents 640
· Effects of polymer microstructure 641
16.3 Tribology of polymer composites 643
Polymer blends 643
Fibre reinforced polymers 643
· Chopped fibre reinforced polymers 644
· Unidirectional and woven fibre reinforcements 644
· Modelling of wear of fibre reinforced polymers 646
Powder composites 647
16.4 Wear and friction of ceramics 648
Unlubricated wear and friction of ceramic-ceramic contacts 650
· Dry friction and wear of ceramics at room temperature 650
· Dry friction and wear of ceramics at elevated temperatures 652
· Friction and wear of ceramics in the presence of water or humid
air 652
· Quantitative wear model of ceramics 653
· Dry wear and friction characteristics of individual ceramics 655
Lubricated wear and friction of ceramic-ceramic contacts 656
· Liquid lubrication 656
· Solid lubricants 658
Wear and friction of ceramics against metallic materials 659
Wear and friction of ceramics against polymers 662
Wear and friction of ceramic matrix composites 662
16.5 Summary 663
References 663
APPENDIX 669
Introduction 669
A.1 User friendly interface 669
A.2 Program ‘VISCOSITY 671
CONTENTS XXIII
Program description 673
List of variables 674
A.3 Program ‘SIMPLE 674
Program description 676
List of variables 677
A.4 Program ‘PARTIAL 678
Program description 681
List of variables 684
A.5 Program ‘THERMAL 686
Program description 690
List of variables 693
A.6 Program ‘DEFLECTION 696
Program description 698
List of variables 701
A.7 Program ‘GROOVE 702
Program description 708
List of variables 714
A.8 Program ‘STABILITY 716
Program description 719
List of variables 721
INDEX 723
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