ThinfilmlubricationandmixedlubricationinnanoscaleLUOJianbinStateKeyLaboratoryofTribologyTsinghuaUniversity,Beijing,China,ContentsIntroductionTestingtechnologyPropertiesofthinfilmlubrication(TFL)FailureoffluidfilmsLubricationmodel&mapContactratioinnano-mixedlubricationConclusion,1.1What’sThinfilmlubrication(TFL)?HDL(1886)EHL(1950s)？BoundaryLurication(1921)Dryslide(Coulomb,1785)1.2Myquestions:?What’sthestateoftheregion？?What’sitslubricationmechanism??What’stherelationshipbetweensuchregimeandEHLorBoundarylubrication?1.Introduction(1),1.Introduction(2)1.3Jost’squestions(Tribology2000):What’sthedefinitionofboundarylubrication?1.4Granick’squestions(Science,1991)Whatdeterminestheeffectiveviscosityofsuchultra-thinfilm?Whatmakesthefilmchangeintosolidstatefromliquidwhenitisenoughthin?Whydosethesolidfilmcanendueacontinuoussliding？,1.Introduction(3)ExperimentonThinfilmlubrication(TFL)Spikes’sgroup(UK)WenandLuo’sgroup(SKLT,TU,China)Hartal’sgroup(Czechoslovakia)Israelachvili’sgroup(USA)Granick’sgroup(USA)CalculationinTFLTichy,Thompson,Robbins,Hu,Popov,etal.,2.Testingtechnology(1)Measurerange:0~500nmVerticalresolution:0.5nmHorizontalresolution:1?mVelocity:0.2~1900mm/sFrictionforceresolution:0.1mNTemperaturerange:~120°CMainQualifications:SchematicofNGY-2,(a)Differentwavelengths(b)DifferentrefractiveindexesResolutionoffilmthicknessv.s.opticalinterferenceintensity2.Testingtechnology(2),Filmthicknessincontactregiona-b-c-d,3.TFLproperties3.1Filmthicknessv.s.influencingfactors3.2Filmthicknessv.s.solidsurfaceenergy3.3EffectofrunningtimeonTFL3.4EffectofexternalelectricfieldonTFL3.5Effectofnano-particlesonTFL3.6TFLviscosity,3.1Filmthicknessv.s.parametersFilmthicknessv.s.viscosityandspeed,FilmthicknesscurveFilmthicknessinthecentralcross-sectionLubricant:mineraloilwithviscosityof36mPa.sat20?CTemperature:25?C,Diameterofball:20mm,Load:6.05N,A:Decane+3%Palmitic,Load:4N,T=30?C,v=0mm/sB:Decane+3%Palmitic,Load:4N,T=30?C,v=3.12mm/sC:Whiteoil,Load:20N,T=20?C,v=54.5mm/s3.2Effectoftime,FilmthicknesscurveFilmincrosssectionofHertzregionLubricant:Paraffinliquid,Load:Temperature:30ºC,Ball:?23.5mmSpeed:18.6mm/sRunningtime:1minSpeed:3.12mm/sRunningtime:40min,Snowball,Lubricant:13604,Load:4N,Temperature:25?C3.3Filmthicknesswithsubstrates,3.4TFLunderexternalelectricfieldFilmthicknessv.s.voltageFrictioncoefficientv.s.velocity,EffectofelectricvoltageonTFL,3.5Filmwithnanoparticles(1)EffectofUDPconcentrationonfilmthickness,TimeeffectofUDPconcentrationonfrictionforce3.5Filmwithnanoparticles(2),（a）Whiteoil+0.5%UDP（b）WhiteoilSEMphotosofballsurfaceLoad:4N，Runningtime:30min,3.6EffectiveviscosityofTFL(1)Floatingdeviceforfrictionmeasurement1.Carrierofstraingauge；2.Straingauge；3.Beam;4.Plank；5.Steelball；6.Oilcup;7.MandrilFrictionwithdifferentsubstratesLubrication:paraffinliquid;Load:2NEffectiveviscositywithfilmthickness,Effectiveviscosityv.s.filmthicknessConcentrationofadditive:2%;Load：0.174GPa3.6EffectiveviscosityofTFL(2),4.Thefailureofliquidfilm(1)Filmthicknessv.s.pressureLubricant:PolyglycoloilFilmthicknessv.s.viscosity,(1)L=?kv0.69(2)Lf=23.5?10-4Pf2Failureofliquidfilm:4.Thefailureofliquidfilm(2),5Lubricationmodelandmap(1)HardymodelofboundarylubricationThinfilmlubricationSolidsurfaceFluidmoleculesOrderedmoleculesAdsorbedmolecules,5Lubricationmodelandmap(2)Lubricationmap,?v0.69-kp2=0Transitionpoint:Failurepoint:5Lubricationmodelandmap(3),6.Contactratioinnano-mixedlubrication6.1Contactratiov.s.averagefilmthickness;6.2Contactratiov.s.speed,load,lubricantviscosityandpolaradditives;6.3Deformationofasperities;6.4Relationshipbetween?andinfluencefactors.2021/9/3Sept,2001SKLT,TsinghuaUniversity28/18,6.1Contactratioandfilmthickness(a)MaximumHertz(pressure:0.293GPa(b)Lubricant:13604Dynamiccontactratio?vs.averagefilmthicknessCombinedsurfaceroughness:16.6nm,6.2Contactratioandinfluencefactors(1)Effectofspeedonthedynamiccontactratio;(2)Effectofloadonthedynamiccontactratio;(3)Effectoflubricantviscosityonthedynamiccontactratio;(4)Effectofsurfaceroughnessonthedynamiccontactratio.2021/9/3Sept,2001SKLT,TsinghuaUniversity30/18,(1)EffectofspeedDynamiccontactratiovs.speedCombinedsurfaceroughness:16.6nm,Lubricant:13604MaximumHertzpressure:0.293GP,(a)v=1.2mm/s,α=0.8(b)v=3.0mm/s,α=0.6(c)v=5.0mm/s,α=0.34(d)v=12.0mm/s,α=0Thefilmthicknessinmixedlubrication(Combinedsurfaceroughness:16.6nm,Lubricant:13604,Pressure:0.293GP),Effectofpressureonthedynamiccontactratio?Combinedsurfaceroughness:16.6nm,Lubricant:136042021/9/3Sept,2001SKLT,TsinghuaUniversity33/15(2)Effectofload,(3)EffectofviscosityEffectofviscosityondynamiccontactratioCombinedsurfaceroughness:16.6nm,(4)EffectofsurfaceroughnessRelationbetweencontactratioandsurfaceroughnessLubricant:13604,MaximumHertzpressure:0.293GPa,Fig.10EffectofpolaradditivesoncontactratioCombinedsurfaceroughness:16.6nm，Pressure:0.293GPa(5)Effectofpolaradditives,6.3Deformationofasperities(a)Load:1.2N,?=0.08(b)Load:3.6N,?=0.24,(c)Load:6.0N,?=0.37(d)Load:8.4N,?=0.51(e)Load:10.8N,?=0.61(f)Load:13.2N,?=0.68,(g)Load:15.5N,?=0.70(h)Load:17.9N,?=0.73(i)Load:20.3N,?=0.78Fig.4ContactregionSurfaceroughness:31.7nm,6.4Relationbetween?andinfluencefactorsStaticDynamic,7.Conclusions(1)Thinfilmlubrication(TFL)isanewlubricationregimebetweenboundarylubricationandEHL;InTFL,filmthicknessisnotonlyrelatedtofluidfactors,butalsotothephysicalandchemicalpropertiesofsolidsurfaceandlubricants;InTFL,electricvoltagehasinfluenceonthefilmthicknessinthenanoscale.,7.Conclusions(2)Theincreaseoflubricantviscosityandspeed,theadditionofpolaradditives,andthedecreaseofpressurewillreducethedynamiccontactratio.Thecontactratiobetweentheroughsurfacesislargerthanthatbetweensmoothsurfacesathigherspeed,butitsvaryingrateissmallerthanthatofsmoothsurfaces.,TableofContentsMaterialandTribologicalCharacterizationPhysicalPropertyCharacterizationofMaterialsPeterHodgsonChemicalCharacterizationofMaterialsKazuhisaMiyoshiMechanicalBehaviorofPlastics:SurfacePropertiesandTribologyMarkI.PetrokovetsandNikolaiMyshkinVisualisationandCharacterisationofSurfaceandBulkMorphologyofPolymericMaterialsbyMicrothermalAnalysisandAtomicForceMicroscopyNamitaChoudhuryMacroandMicromechanicsofCeramicsBesimBen-NissanScuffingandSeizureCharacterizationandInvestigationMarianSzczerek,TadeuszBurakowski,andWaldemarTuszynskiWearMappingandFrictionandWearCharacterizationMethodologyS.C.LimandChristinaLimMeasuringTechniqueandCharacteristicsofThinFilmLubricationatNanoScaleLuoJianbinandWenShizhuApplicationTribologyTribologyofMetalCuttingV.AstakhovTribologyofMetalFormingEmilevanderHeideandD.J.SchipperTribologyinTextileManufacturingandUseStephenMichielsenBiotribologyBingShiandHongLiangBiocompatibleMetalsandAlloys:PropertiesandDegradationPhenomenainBiologicalEnvironmentsAlexiaW.E.Hodgson,SannakaisaVirtanen,andHeimoWabussegMeasuringTechniqueandCharacteristicsofThinFilmLubricationatNanoScaleLuoJianbinandWenShizhuItwillbepublishedinApril,2004,Thankyouforattention!,CollisionofaparticletosurfaceParticle：Si，4×4×4crystalcells(512atoms);Surface：Si，22*22*10crystalcells(38720atoms);Insetangel:0º;Speed:50,1200,6000m/s.,Collisionprocess1.Adhesionphenomenon粘著階段：若入射能量較高，顆粒的勢(shì)能、熱運(yùn)動(dòng)能在極短時(shí)間內(nèi)增大到極大值，然后在一段時(shí)間內(nèi)較快地減小，使粘附在表面上的顆粒形成穩(wěn)定的形態(tài)2.Vibrationphenomenon振動(dòng)階段：與表面粘著在一起的、具有穩(wěn)定形態(tài)的顆粒上下振動(dòng)，隨著能量的耗散，振幅緩慢減小，振動(dòng)頻率由單晶Si的性質(zhì)決定,Adhesionprocess(atspeedof50m/s)Adhesionprocesswithin10psPotentialenergy:－Kineticenergy:－Time:0-50ps,Adhesionprocess0-10psAdhesionprocess(atspeedof6000m/s)Potentialenergy:－Kineticenergy:－Time:0-50ps,Vibrationprocessatspeedof1200m/s結(jié)合能和顆粒質(zhì)心位置變化曲線（0～50ps）質(zhì)心位置：－，結(jié)合能：－Vibrationprocess0-50ps振動(dòng)過程:10~50ps,Vibrationprocess－振動(dòng)幅度Variationsofparticle’scentralpositionincollisionprocessSpeed:1200m/s,Temperature：300K(－)，50K(－),Vibrationprocess―frequencyVariationsofparticle’scentralpositionincollisionprocess碰撞過程顆粒質(zhì)心位置變化曲線Insetspeed:1200m/s(－)，6000m/s(－),Thankyouforattention!,為什么粘著？為什么不反彈?若變形顆粒釋放的彈性勢(shì)能小于顆粒與表面的結(jié)合能，則發(fā)生粘著；反之，顆粒將反彈出表面Si共價(jià)鍵的結(jié)合能很大顆粒的粒徑越小，能量越易耗散顆粒的粒徑越小，結(jié)合能越小，越易破碎