ENGINEERING TRIBOLOGY - GBV

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E N G I N E E R I N GT R I B O L O G YGwidon W. StachowiakDepartment of Mechanical and MaterialsUniversity of Western Australia, AustraliaEngineering,Andrew W. BatchelorDepartment of Mechanical and MaterialsUniversity of Western Australia, AustraliaEngineering,R W O R T HBoston Oxford Auckland Johannesburg Melbourne New Delhi

CONTENTS1INTRODUCTIONBackground1.1Meaning of tribology1.2LubricationWearCost of friction and wear1.3Summary1.4References2PHYSICAL PROPERTIES OF il viscosityDynamic viscosityKinematic viscosityViscosity temperature relationshipViscosity-temperature equationsViscosity-temperature chartViscosity indexViscosity pressure relationshipViscosity-shear rate relationshipPseudoplastic behaviourThixotropic behaviourViscosity measurementsCapillary viscometersRotational viscometersRotating cylinder viscometerCone on plate viscometerOther viscometersViscosity of mixturesOil viscosity 293031

VinENGINEERING TRIBOLOGYSAE viscosity classificationISO viscosity classification2.10 Lubricant density and specific gravity2.11 Thermal properties of lubricantsSpecific heatThermal conductivityThermal diffusivity2.12 Temperature characteristics of lubricantsPour point and cloud pointFlash point and fire pointVolatility and evaporationOxidation stabilityThermal stabilitySurface tensionNeutralization numberCarbon residue 2.13 Optical properties of lubricantsRefractive index2.14 Additive compatibility and solubilityAdditive compatibilityAdditive solubility2.15 Lubricant impurities and contaminantsWater contentSulphur contentAsh contentChlorine content2.16 Solubility of gases in oils2.17 SummaryReferences3LUBRICANTS AND THEIR COMPOSITION3.1 Introduction3.2 Mineral oilsSources of mineral oilsManufacture of mineral oilsTypes of mineral oilsChemical formsSulphur 3434444444444454545454848515152525456565757

CONTENTS3.33.43.5Synthetic oilsManufacturing of synthetic oilsHydrocarbon synthetic lubricantsPolyalphaolefinsPolyphenyl ethersEstersCycloaliphaticsPolyglycolsSilicon analogues of uoroethylenesPerfluoropolyalkylethersEmulsions and aqueous lubricantsManufacturing of turing of greasesCompositionBase oilsThickenerAdditivesFillersLubrication mechanism of greasesGrease characteristicsConsistency of greasesMechanical stabilityDrop pointOxidation stabilityThermal stabilityEvaporation lossGrease viscosity characteristicsClassification of greasesGrease compatibilityDegradation of 6666767676869697272737475757676788080

ENGINEERING TRIBOLOGY3.6Lubricant additivesWear and friction improversAdsorption or boundary additivesAnti-wear additivesExtreme pressure additivesAnti-oxidantsOil oxidationOxidation inhibitorsCorrosion control additivesContamination control additivesViscosity improversPour point depressantsFoam inhibitorsInterference between additives3.7 YDRODYNAMIC LUBRICATION4.1 Introduction4.2 Reynolds equationSimplifying assumptionsEquilibrium of an elementContinuity of flow in a columnSimplifications to the Reynolds equationUnidirectional velocity approximationSteady film thickness approximationIsoviscous approximationInfinitely long bearing approximationNarrow bearing approximationBearing parameters predicted from Reynolds equationPressure distributionLoad capacityFriction forceCoefficient of frictionLubricant flowSummary4.3 Pad bearingsInfinite linear pad bearingBearing 113114115115115116116116

CONTENTS4.44.5Pressure distributionLoad capacityFriction forceCoefficient of frictionLubricant flow rateInfinite Rayleigh step bearingOther wedge geometries of infinite pad bearingsTapered land wedgeParabolic wedgeParallel surface bearingsSpiral groove bearingFinite pad bearingsPivoted pad bearingInlet boundary conditions in pad bearing analysisConverging-diverging wedgesBearing geometryPressure distributionFull-Sommerfeld boundary conditionHalf-Sommerfeld boundary conditionReynolds boundary conditionLoad capacityJournal bearingsEvaluation of the main parametersBearing geometryPressure distributionLoad capacityFriction forceCoefficient of frictionLubricant flow ratePractical and operational aspects of journal bearingsLubricant supplyCavitationJournal bearings with movable padsJournal bearings incorporating a Rayleigh stepOil whirl or lubricant caused vibrationRotating loadTilted shaftsPartial bearingsElastic deformation of the 159163164164165167169170171

xnENGINEERING TRIBOLOGYInfinitely long approximation in journal bearings4.65172Thermal effects in bearingsHeat transfer mechanisms in bearingsConductionConvectionConducted/convected heat ratioIsoviscous thermal analysis of bearingsIterative methodConstant flow methodNon-isoviscous thermal analysis of bearings with locally varying viscosityMultiple regression in bearing analysisBearing inlet temperature and thermal interaction between pads of aMichell bearing4.7 Limits of hydrodynamic lubrication4.8 Hydrodynamic lubrication with non-Newtonian fluidsTurbulence and hydrodynamic lubricationHydrodynamic lubrication with non-Newtonian lubricantsInertial effects in hydrodynamicsCompressible fluidsCompressible hydrodynamic lubrication in gas bearings4.9 Reynolds equation for squeeze filmsPressure distributionLoad capacitySqueeze timeCavitation and squeeze filmsMicroscopic squeeze film effects between rough sliding surfaces4.10 Porous bearings4.11 PUTATIONAL HYDRODYNAMICS5.1 Introduction5.2 Non-dimensionalization of the Reynolds equation5.3 The Vogelpohl parameter5.4 Finite difference equivalent of the Reynolds equationDefinition of solution domain and boundary conditionsCalculation of pressure fieldCalculation of dimensionless friction force and friction coefficientNumerical solution technique for Vogelpohl 186187189191192193194195196196197198

CONTENTSNumerical analysis of hydrodynamic lubrication in idealized journaland partial arc bearingsExample of data from numerical analysis, the effect of shaft misalignment5.6Numerical analysis of hydrodynamic lubrication in a real bearing5.6.1 Thermohydrodynamic lubricationGoverning equations and boundary conditions inthermohydrodynamic lubricationGoverning equations in thermohydrodynamic lubrication for aone-dimensional bearingThermohydrodynamic equations for the finite pad bearingBoundary conditionsFinite difference equations for thermohydrodynamic lubricationTreatment of boundary conditions in thermohydrodynamic lubricationComputer program for the analysis of an infinitely long pad bearing inthe case of thermohydrodynamic lubricationExample of the analysis of an infinitely long pad bearing in the case ofthermohydrodynamic lubrication5.6.2 Elastic deformations in a pad bearingComputer program for the analysis of an elastically deforming onedimensional pivoted Michell pad bearingEffect of elastic deformation of the pad on load capacity and film thickness5.6.3 Cavitation and film reformation in grooved journal bearingsComputer program for the analysis of grooved 360 journal bearingsExample of the analysis of a grooved 360 journal bearing5.6.4 Vibrational stability in journal bearingsDetermination of stiffness and damping coefficientsComputer program for the analysis of vibrational stability in a partial arcjournal bearingExample of the analysis of vibrational stability in a partial arc journal bearing5.7 SummaryReferencesxm5.5HYDROSTATIC LUBRICATION6.1 Introduction6.2 Hydrostatic bearing analysisFlat circular hydrostatic pad bearingPressure distributionLubricant flowLoad capacityFriction 60

xiv7ENGINEERING TRIBOLOGYFriction power lossNon-flat circular hydrostatic pad bearingsPressure distributionLubricant flowLoad capacityFriction torqueFriction power loss6.3 Generalized approach to hydrostatic bearing analysisFlat circular pad bearingsFlat square pad bearings6.4 Optimization of hydrostatic bearing designMinimization of powerLow speed recessed bearingsHigh speed recessed bearingsControl of lubricant film thickness and bearing stiffnessStiffness with constant flow methodStiffness with capillary restrictorsStiffness with an orificeStiffness with pressure sensors6.5 Aerostatic bearingsPressure distributionGas flowLoad capacityFriction torquePower loss6.6 Hybrid bearings6.7 Stability of hydrostatic and aerostatic bearings6.8 9279ELASTOHYDRODYNAMIC LUBRICATION7.1 Introduction7.2 Contact stressesSimplifying assumptions to Hertz's theoryStress status in static contactStress status in lubricated rolling and sliding contacts7.3 Contact between two elastic spherical or spheroidal bodiesGeometry of contacting elastic bodiesTwo elastic bodies with convex surfaces in contact281281282282283283284285286

CONTENTS7.47.57.6Two elastic bodies with one convex and one flat surface in contactTwo elastic bodies with one convex and one concave surface incontactContact area, pressure, maximum deflection and position of themaximum shear stressContact between two spheresContact between a sphere and a plane surfaceContact between two parallel cylindersContact between two crossed cylinders with equal diametersElliptical contact between two elastic bodies, general caseTotal deflectionElastohydrodynamic lubricating filmsEffects contributing to the generation of elastohydrodynamic filmsHydrodynamic film formationModification of film geometry by elastic deformationTransformation of lubricant viscosity and rheology under pressureApproximate solution of Reynolds equation with simultaneous elasticdeformation and viscosity risePressure distribution in elastohydrodynamic filmsElastohydrodynamic film thickness formulaeEffects of the non-dimensional parameters on EHL contact pressures andfilm profilesEffect of the speed parameterEffect of the materials parameterEffect of load parameterEffect of elliptidty parameterLubrication regimes in EHL - film thickness us-elasticPiezoviscous-elasticIdentification of the lubrication regimeElastohydrodynamic film thickness measurementsMicro-elastohydrodynamic lubrication and mixed or partial EHLPartial or mixed EHLMicro-elastohydrodynamic lubricationSurface temperature at the conjunction between contacting solids andits effect on EHLCalculation of surface conjunction temperatureFlash temperature in circular 323325327328331

x v i ENGINEERING TRIBOLOGY8Flash temperature in square contactsFlash temperature in line contactsTrue flash temperature riseFrictional temperature rise of lubricated contactsMechanism of heat transfer within the EHL filmEffect of surface films on conjunction temperaturesMeasurements of surface temperature in the EHL contacts7.7 Traction and EHLA simplified analysis of traction in the EHL contactNon-Newtonian lubricant rheology and EHLEHL between meshing gear wheels7.8 352352BOUNDARY AND EXTREME PRESSURE LUBRICATION8.1 Introduction8.2 Low temperature - low load lubrication mechanisms8.3 Low temperature - high load lubrication mechanismsModel of adsorption on sliding surfacesPhysisorptionChemisorptionInfluence of the molecular structure of the lubricant onadsorption lubricationInfluence of oxygen and waterDynamic nature of adsorption under sliding conditionsMixed lubrication and scuffingMetallurgical effectsInteraction between surfactant and carrierfluid8.4 High temperature - medium load lubrication mechanismsChain matchingThick films of soapy or amorphous materialSoap layersAmorphous layers8.5 High temperature - high load lubrication mechanismsModel of lubrication by sacrificial filmsAdditive reactivity and its effect on lubricationNascent metallic surfaces and accelerated film formationInfluence of oxygen and water on the lubrication mechanism bysacrificial 384384385388389390393395

CONTENTSXVIIMechanism of lubrication by milder E.P. AdditivesFunction of active elements other than sulphurLubrication with two active elementsTemperature distressSpeed limitations of sacrificial film mechanismTribo-emission from worn surfaces8.6 Boundary and E.P. lubrication of non-metallic surfaces8.7 SummaryReferences398398399401403403404404405SOLID LUBRICATION AND SURFACE TREATMENTS9.1 Introduction9.2 Lubrication by solids9.2.1 Lubrication by lamellar solidsFriction and wear characteristics of lamellar solidsGraphite and molybdenum disulphideCarbon-based materials other than graphiteMinor solid lubricantso9.2.2 Reduction of friction by soft metallic filmsReduction of friction by metal oxides at high temperatures9.2.3 Deposition methods of solid lubricantsTraditional methods of solid lubricant depositionModern methods of solid lubricant depositionSolid lubricants as additives to oils and polymers9.3 Wear resistant coatings and surface treatments9.3.1 Techniques of producing wear resistant coatingsCoating techniques dependent on vacuum or gas at very low pressurePhysical vapour depositionChemical vapour deposition.Physical-chemical vapour depositionIon implantationCoating processes requiring localized sources of intense heatSurface weldingThermal sprayingLaser surface hardening and alloyingCoating processes based on deposition in the solid stateMiscellaneous coating processesApplication of coatings and surface treatments in wear and friction controlCharacteristics of wear resistant 426427427427430430431432432-433436436438438439

XVIII1011ENGINEERING TRIBOLOGY9.4 SummaryReferences442442FUNDAMENTALS OF CONTACT BETWEEN SOLIDS10.1 Introduction10.2 Surfaces of solidsSurfaces at a nano scaleSurface topographyCharacterization of surface topographyCharacterization of surface topography by statistical parametersMulti-scale characterization of surface topographyCharacterization of surface topography by Fourier transformCharacterization of surface topography by waveletsCharacterization of surface topography by fractalsOptimum surface roughness10.3 Contact between solidsModel of contact between solids based on statistical parameters of roughsurfacesModel of contact between solids based on the fractal geometry of roughsurfacesEffect of sliding on contact between solid surfaces10.4 Friction and wearOnset of sliding and mechanism of stick-slipStructural differences between static and sliding contactsFriction and other contact phenomena in rollingConcentration of frictional heat at the asperity contactsWear between surfaces of solids10.5 460461ABRASIVE, EROSIVE AND CAVITATION WEAR11.1 Introduction11.2 Abrasive wearMechanisms of abrasive wearModes of abrasive wearAnalytical models of abrasive wearAbrasivity of particlesAbrasive wear resistance of materials483483483484486487494499Abrasive wear resistance of steelsAbrasive wear resistance of polymers and rubbers462465467468469471473476477478478502504

CONTENTS12XLXAbrasive wear resistance of ceramicsEffect of temperature on abrasive wearEffect of moisture on abrasive wearControl of abrasive wear11.3 Erosive wearMechanisms of erosive wearEffect of impingement angle and impact speed on erosive wear rateEffect of particle shape, hardness, size and flux rates on erosive wear rateErosive wear by liquidEffect of temperature on erosive wearEffect of erosion media on erosive wearErosive wear resistance of materialsErosive wear resistance of steelsErosive wear resistance of polymersErosive wear of ceramics and cermets11.4 Cavitation wearMechanism of cavitation wearCavitation wear resistance of materials11.5 518520521523524524525526527ADHESION AND ADHESIVE WEAR12.1 Introduction12.2 Mechanism of adhesionMetal-metal adhesionMetal-polymer adhesionMetal-ceramic adhesionPolymer-polymer and ceramic-ceramic adhesionEffects of adhesion between wearing surfacesFriction due to adhesionJunction growth between contacting asperities as a cause ofextreme frictionSeizure and scuffingAsperity deformation and formation of wear particlesTransfer films12.3 Control of the adhesive wearContaminant layers formed due to surface oxidation and bulk impuritiesLubricantsFavourable combinations of sliding 8549549550

XX1314ENGINEERING TRIBOLOGY12.4 SummaryReferences550550CORROSIVE AND OXIDATIVE WEAR13.1 Introduction13.2 Corrosive wearTransition between corrosive and adhesive wearSynergism between corrosive and abrasive wearTribochemical polishing13.3 Oxidative wearKinetics of oxide film growth on metals at high and low temperaturesOxidative wear at high sliding speedsOxidative wear at low sliding speedsOxidative wear at high temperature and stressOxidative wear at low temperature applicationsTransition between oxidative and adhesive wearOxidative wear under lubricated conditionsMeans of controlling corrosive and oxidative wear13.4 565566566567567568FATIGUE WEAR14.1 Introduction14.2 Fatigue wear during slidingSurface crack initiated fatigue wearSubsurface crack initiated fatigue wearEffect of lubrication on fatigue wear during slidingPlastic ratchetting14.3 Fatigue wear during rollingCauses of contact fatigueAsperity contact during EHL and the role of debris in the lubricantin contact fatigueMaterial imperfectionsSelf-propagating nature of contact fatigue cracks»Subsurface and surface modes of contact fatigueEffect of lubricant on contact fatigueHydraulic pressure crack propagationChemical effects of lubricant additives, oxygen and water on contact fatigueMaterials effect on contact 85586587

CONTENTSXXIInfluence of operating conditions on rolling wear and contact fatigue14.4 Means of controlling fatigue wear14.5 SummaryReferences58858958959015FRETTING AND MINOR WEAR MECHANISMS15.1 Introduction15.2 Fretting wearMicroscopic movements within the contact under applied loadsElastic model for fretting contactsElasto-plastic model for fretting contactsEffect of amplitude and debris retention on fretting wearEnvironmental effects on fretting wearEffects of temperature and lubricants on frettingEffect of materials properties and surface finish on frettingFretting fatiguePractical examples of frettingMeans of controlling fretting15.3 Melting wear15.4 Wear due to electrical discharges15.5 Diffusive wear15.6 Impact wear15.7 60760860961161261361561616WEAR OF NON-METALLIC MATERIALS16.1 Introduction16.2 Tribology of polymersSliding wear of polymers, transfer layers on a harder counterfaceInfluence of counterface roughness, hardness and material type ontransfer films and associated wear and friction of polymersCounterface hardnessCounterface roughnessCounterface surface energyInfluence of temperature on polymer wear and frictionLimit on frictional temperature rise imposed by surface meltingEffect of high frictional temperatures and sliding speeds on wearCombined effect of high surface roughness and elevated contacttemperature on wearFatigue wear of polymers and long term wear kinetics619619619621622623623626626627630631633

XXIIENGINEERING TRIBOLOGYVisco-elasticity and the rubbery state

ENGINEERING TRIBOLOGY Gwidon W. Stachowiak Department of Mechanical and Materials Engineering, University of Western Australia, Australia . HYDRODYNAMIC LUBRICATION 101 4.1 Introduction 101 4.2 Reynolds equation 101 Simplifying assumptions 103 Equilibrium of an element 103