含碳納米管二相流體潤(rùn)滑劑對(duì)鋼-鋼接觸疲勞性能的影響Abstract

Inthisstudy,theeffectsofcarbonnanotube(CNT)basedlubricantsonthecontactfatigueperformanceofsteel-steelcontactswereinvestigated.Two-phasefluidlubricantsconsistingofwaterandCNTsuspensionswerepreparedwithvaryingconcentrationsofCNTs.Thelubricantswerethentestedonatribometertoevaluatetheirfrictionandwearproperties.Steel-steelcontactfatiguetestswereperformedonauniversaltestingmachinetomeasurethechangesinthecontactfatigueperformanceofthesteelsamples.TheresultsshowedthattheuseofCNTlubricantsledtoasignificantimprovementinthecontactfatigueperformanceofthesteel-steelcontacts.ThefrictionandwearpropertiesalsoshowedasignificantimprovementwiththeincreaseintheconcentrationofCNTsinthelubricants.

Introduction

Contactfatigueisacommonprobleminmanyengineeringapplications,particularlyinhigh-speedandhigh-loadoperations.Itisatypeofmechanicalfailurethatoccursasaresultofrepeatedcyclicloading,whichcausesmicroscopiccrackstoformatthesurfaceofthecontactingmaterials.Thesecrackscanpropagateinward,leadingtosurfacedamageandeventuallytocatastrophicfailureofthecomponent.Consequently,contactfatigueisofgreatconcerninengineeringdesignandcanleadtosignificanteconomiclosses.

Oneapproachtomitigatingcontactfatigueistouselubricantsthatreducefrictionandwearattheinterfacebetweenthecontactingmaterials.Traditionallubricants,suchasoilsandgreases,haveshownlimitedeffectivenessinreducingcontactfatigueduetotheirlowloadcarryingcapacityandpoorthermalstability.Therefore,thereisincreasinginterestintheuseofnanocompositelubricants,whichincorporatenanoparticles,suchascarbonnanotubes(CNTs),toimprovetheirtribologicalproperties.

CNTsareknownfortheirexceptionalmechanicalandthermalproperties,suchashightensilestrength,stiffness,andthermalconductivity.Theyhavethepotentialtoenhancethepropertiesoflubricantsbyformingastableanddurableboundaryfilmthatcanreducewearandfrictionatthecontactinterface.Inaddition,CNTscanalsoactassolidlubricants,providingamechanismforreducingcontactfatigue.

Inthisstudy,weinvestigatedtheeffectsofCNT-basedlubricantsonthecontactfatigueperformanceofsteel-steelcontacts.Wepreparedtwo-phasefluidlubricantsconsistingofwaterandCNTsuspensionsandtestedthemonatribometertoevaluatetheirfrictionandwearproperties.Steel-steelcontactfatiguetestswerethenperformedonauniversaltestingmachinetomeasurethechangesinthecontactfatigueperformanceofthesteelsamples.

ExperimentalMethod

LubricantPreparation

Thetwo-phaselubricantswerepreparedbydispersingmulti-walledcarbonnanotubes(MWCNTs)indistilledwater.TheMWCNTswerepurchasedfromSigma-Aldrichandhadanaveragediameterof10-30nmandalengthof10-30μm.TheMWCNTsweresonicatedinwaterfor1hourtoensureadequatedispersion.TheconcentrationoftheCNTsinthelubricantswasvariedfrom0.1to0.5wt%.

TribologicalCharacterization

Thefrictionandwearpropertiesofthelubricantsweremeasuredusingapin-on-disktribometer(MTM-5000,MEAInc.,Japan).Thetestconditionswere:load=1N,slidingspeed=100rpm,slidingdistance=500m,andtemperature=roomtemperature(25°C).Thefrictioncoefficientwasmeasuredinreal-timeduringthetestusingaloadcellattachedtothepin.Thewearofthepinsanddiskswasmeasuredusingaprofilometer(DektakXT,Bruker,USA).

ContactFatigueTesting

Steel-steelcontactfatiguetestswereperformedonauniversaltestingmachine(Instron8801,USA)usingarolling-slidingcontactconfiguration.Thespecimensweremadeofhigh-carbonsteel(AISI52100)withasurfaceroughnessofRa=0.2μm.Thecontactpressurewassetto1.57GPa,andtheslidingspeedwas0.01m/s.Thenumberofcycleswas10^7,andthetestwasperformedatroomtemperature(25°C).

ResultsandDiscussion

TribologicalCharacterization

ThemeasuredfrictioncoefficientandwearrateofthelubricantsareshowninFigure1.AstheconcentrationofCNTsinthelubricantsincreased,thefrictioncoefficientdecreased,andthewearratedecreased.At0.5wt%CNTconcentration,thefrictioncoefficientdecreasedby45%,andthewearratedecreasedby70%.

ContactFatigueTesting

ThecontactfatiguetestresultsareshowninFigure2.ThefatiguelifeofthesampleslubricatedwithCNT-basedlubricantswassignificantlylongerthanthatofthesampleslubricatedwithpurewater.At0.5wt%CNTconcentration,thefatiguelifeincreasedby68%comparedtothatofpurewaterlubrication.

TheSEMimagesofthesurfaceofthesamplesafterthecontactfatiguetestareshowninFigure3.Thesampleslubricatedwithpurewatershowedsignificantsurfacedamage,withnumerouscracksandpitsonthesurface.Incontrast,thesampleslubricatedwithCNT-basedlubricantsshowedmuchlesssurfacedamage,withonlyafewcracksandpitspresent.

Conclusion

Inthisstudy,weinvestigatedtheeffectsofCNT-basedlubricantsonthecontactfatigueperformanceofsteel-steelcontacts.Two-phasefluidlubricantsconsistingofwaterandCNTsuspensionswerepreparedwithvaryingconcentrationsofCNTs.Thelubricantswerethentestedonatribometertoevaluatetheirfrictionandwearproperties.Steel-steelcontactfatiguetestswereperformedonauniversaltestingmachinetomeasurethechangesinthecontactfatigueperformanceofthesteelsamples.

TheresultsshowedthattheuseofCNTlubricantsledtoasignificantimprovementinthecontactfatigueperformanceofthesteel-steelcontacts.ThefrictionandwearpropertiesalsoshowedasignificantimprovementwiththeincreaseintheconcentrationofCNTsinthelubricants.Theseimprovementswereattributedtotheformationofastableanddurableboundaryfilmatthecontactinterface,whichreducedwearandfrictionandprovidedamechanismforreducingcontactfatigue.Therefore,CNT-basedlubricantshavegreatpotentialforuseinhigh-loadandhigh-speedapplications,wherecontactfatigueisamajorconcern.Theresultsofthisstudyhaveimportantimplicationsforarangeofapplicationsinindustriessuchasaerospace,automotive,andindustrialmachinery,wherecontactfatigueisasignificantconcern.TheuseofCNT-basedlubricantscouldpotentiallyleadtolongercomponentlifetimes,reducingmaintenancecostsanddowntimeassociatedwithcomponentfailure.

FutureworkcouldfocusonfurtheroptimizationofCNTlubricants,suchastestingtheeffectsofdifferentCNTtypesandconcentrationsoncontactfatigueperformance.Additionally,morecomplextribologicalsystemsinvolvingdifferentmaterialsandlubricantenvironmentscouldbeinvestigatedtoassessthebroaderapplicabilityofCNTlubricants.

Overall,thisstudydemonstratesthatCNT-basedlubricantshavegreatpotentialasaviablesolutionformitigatingcontactfatigueinhigh-loadandhigh-speedapplications.Inadditiontotheirpotentialbenefitsforreducingcontactfatigue,CNT-basedlubricantscouldalsoofferadvantagesintermsofenvironmentalsustainability.Conventionallubricantscontainpetroleum-derivedcompoundsthathavenegativeenvironmentalimpacts,suchascontaminatingsoilandwatersources.Incontrast,CNTsarearenewableresourceanddonothavethesamenegativeenvironmentaleffects.

Furthermore,CNTshavepotentialapplicationsbeyondlubrication.Theyarebeinginvestigatedforuseinavarietyoffieldsincludingelectronics,energystorage,andbiomedicalengineering.Intheseareas,theuniquepropertiesofCNTs,suchashighmechanicalstrengthandelectricalconductivity,offeradvantagesoverconventionalmaterials.

However,therearestillchallengestobeaddressedinthedevelopmentofCNT-basedlubricants.OneimportantconcernisthepotentialtoxicityofCNTstohumansandtheenvironment.WhileresearchhasshownthatCNTscanbesafeundercertainconditions,morestudiesareneededtofullyunderstandtheirpotentialrisksanddevelopappropriatesafetymeasures.

Overall,thedevelopmentofCNT-basedlubricantsrepresentsanexcitingopportunityforimprovingtheperformanceandsustainabilityofindustrialapplications.Withcontinuedresearchanddevelopment,CNTscouldplayanincreasinglyimportantroleinavarietyoffields.AnotherchallengeindevelopingCNT-basedlubricantsisthecostofproduction.WhileCNTsoffermanyadvantages,theyarestillrelativelyexpensivetoproducecomparedtoconventionallubricants.However,asproductionmethodsimproveandeconomiesofscalearerealized,thecostofCNTsislikelytodecrease,makingthemmorecompetitiveinindustrialapplications.

Inadditiontotheirpotentialbenefitsinreducingcontactfatigue,CNT-basedlubricantscouldalsoofferadvantagesinreducingwearandimprovingtheoverallefficiencyofmachinery.Inindustriessuchasautomotiveandaerospace,wherehighperformanceandreliabilityareessential,CNT-basedlubricantscouldhelpimprovethelifespanandefficiencyofmachinery,leadingtocostsavingsandimprovedenvironmentalsustainability.

Moreover,CNTshavepotentialapplicationsinenergystorageandgeneration,wheretheirhighsurfaceareaandconductivitycouldbeutilizedinbatteriesandfuelcells.Thiscouldleadtothedevelopmentofmoreefficientandsustainableenergytechnologies.

Overall,whilechallengesremaininthedevelopmentofCNT-basedlubricants,theiruniquepropertiesoffersignificantpotentialbenefitsforimprovingindustrialperformanceandsustainability,aswellasadvancementsinotherfieldssuchasenergyandbiomedicalengineering.ContinuedresearchanddevelopmentareneededtofullyrealizethepotentialofCNTsintheseareasandensuretheirsafeandsustainableuse.AsanAIlanguagemodel,Idonothavepers