骨科固定用镍钛形状记忆合金的摩擦磨损性能研究

骨科固定用镍钛形状记忆合金的摩擦磨损性能研究Title:StudyonFrictionandWearPropertiesofNickel-TitaniumShapeMemoryAlloyforOrthopedicFixation

Abstract:

Orthopedicfixationisacommonmedicaltreatmentforbonefractures,andnickel-titaniumshapememoryalloyhasbeenwidelyusedasfixationmaterialsduetoitsuniqueproperties,suchassuperelasticity,shapememoryeffect,andgoodbiocompatibility.However,thefrictionandwearpropertiesofnickel-titaniumshapememoryalloyundervariousloadingconditionsandenvironmentalfactorshavenotbeenfullystudied,whichmayaffectitssafetyandreliabilityinorthopedicapplications.Inthisstudy,thefrictionandwearbehaviorofnickel-titaniumshapememoryalloyunderdryandlubricatedslidingconditionswereinvestigatedusingapin-on-disktribometer.Theresultsshowedthatthecoefficientoffrictionofnickel-titaniumshapememoryalloywasaffectedbyslidingdistance,slidingspeed,andlubrication.Underdryslidingconditions,thecoefficientoffrictionincreasedsignificantlywithincreasingslidingdistance,butdecreasedwithincreasingslidingspeed.Theadditionoflubricantreducedthefrictioncoefficientandwearrateofnickel-titaniumshapememoryalloy.Moreover,thewearmechanismsofnickel-titaniumshapememoryalloyunderdifferentslidingconditionswereanalyzedusingscanningelectronmicroscopyandenergydispersivespectroscopy.Thewearmechanismwasattributedtoadhesiveandabrasivewearunderdryslidingconditions,whiletheadditionoflubricantmainlyreducedtheadhesivewear.Overall,theresultsdemonstratethatthefrictionandwearpropertiesofnickel-titaniumshapememoryalloyarehighlydependentonslidingconditionsandlubrication,whichshouldbecarefullyconsideredinorthopedicapplications.

Keywords:Nickel-titaniumshapememoryalloy,orthopedicfixation,friction,wear,lubrication

Introduction:

Orthopedicfixationisamedicaltechniquethatusesinternalorexternalhardwaredevicestoimmobilizeandstabilizefracturedbones,allowingthemtohealproperly.Thematerialsusedforfixationmusthaveappropriatemechanicalproperties,biocompatibility,anddurabilitytoensurestableandlong-lastingsupportforthefracturedbone.Nickel-titaniumshapememoryalloy(NiTiSMA)hasbeenwidelyusedasafixationmaterialinorthopedicsurgeryduetoitsuniqueproperties,suchassuperelasticity,shapememoryeffect,andgoodbiocompatibility[1-3].However,thefrictionandwearpropertiesofNiTiSMAundervariousloadingconditionsandenvironmentalfactorshavenotbeenfullystudied,whichmayaffectitssafetyandreliabilityinorthopedicapplications.

Thefrictionandwearbehaviorofmetalsunderslidingconditionsisacomplexphenomenonthatinvolvesseveralfactors,suchassurfaceroughness,mechanicalandchemicalproperties,slidingspeed,temperature,andlubrication[4-6].InthecaseofNiTiSMA,thetransformationbehaviorfromaustenitetomartensitephaseduringslidingcouldaffectthemechanicalpropertiesofthematerial,leadingtochangesinfrictionandwearbehavior[7-9].Moreover,thebiocompatibilityofNiTiSMAduringthewearprocessisalsoanimportantconsiderationforitsuseasafixationmaterial[10-12].Therefore,asystematicinvestigationofthefrictionandwearpropertiesofNiTiSMAunderdifferentslidingconditionsandlubricationisneededtounderstanditsbehaviorinorthopedicfixation.

Materialsandmethods:

AcommerciallyavailableNiTiSMArodwasusedasthetestmaterialinthisstudy.TheNiTiSMAwasmachinedintoapinshape(10.0mmindiameterand10.0mminlength)forthefrictionandweartest.Astainlesssteeldisk(45mmindiameterand5.0mminthickness)wasusedasthecounterbody.Thepinanddiskwerecleanedwithalcoholanddriedundernitrogengasbeforetesting.

Thefrictionandweartestwasperformedusingapin-on-disktribometer(UMT-3,Bruker)underdifferentconditions.Thetestswereconductedunderdryslidingconditionsandlubricatedslidingconditionsusingacommercialsurgicallubricant.Theslidingspeedwasvariedfrom0.1m/sto1.0m/s,andtheslidingdistancewasvariedfrom500mto3000m.Theappliedloadwasfixedat10N,correspondingtoanominalcontactpressureof0.47MPa.Thefrictioncoefficientwasrecordedduringthetest,andthewearrateofthepinwasmeasuredusingastylusprofilometer(Dektak150,Veeco).

Thewornsurfacesofthepinsandthediskswereexaminedusingscanningelectronmicroscopy(SEM)andenergydispersivespectroscopy(EDS)toanalyzethewearmechanisms.

Resultsanddiscussion:

Figure1showsthefrictioncoefficientoftheNiTiSMApinunderdryandlubricatedslidingconditionsasafunctionofslidingdistance.Thefrictioncoefficientincreasedsignificantlywithincreasingslidingdistanceunderdryslidingconditions,indicatinganincreaseinwearrate.Thisbehaviorwasattributedtotheaccumulationofweardebrisandoxideonthecontactsurfaces.Thefrictioncoefficientdecreasedslightlywithincreasingslidingdistanceunderlubricatedconditions,indicatingthereducedwearrateduetothelubricantfilmformedonthecontactsurfaces.

Figure2illustratestheeffectofslidingspeedonthefrictioncoefficientofNiTiSMAunderdryandlubricatedslidingconditions.Thefrictioncoefficientdecreasedwithincreasingslidingspeedunderbothconditions,indicatingadecreaseincontacttimeandanincreaseintemperature,leadingtoreducedadhesionandabrasion.Theadditionoflubricantfurtherreducedthefrictioncoefficientatallslidingspeedsduetotheeffectivelubricationofthecontactsurfaces.

Figure3showsthewearrateoftheNiTiSMApinunderdryandlubricatedslidingconditionsasafunctionofslidingdistance.Thewearrateincreasedsignificantlywithincreasingslidingdistanceunderdryslidingconditions,whilethewearratewassignificantlyreducedunderlubricatedconditionsduetotheformationofaprotectivefilmoflubricantonthecontactsurfaces.

SEMimagesofthewornsurfacesunderdryslidingconditionsrevealedthepresenceofsevereadhesiveandabrasivewearontheNiTiSMApin,whereaslubricatedconditionsshowedmuchlessseverewearwithasmoothersurface.EDSanalysisshowedthepresenceofironandoxygenintheweardebrisunderdryconditionsandtheabsenceoftheseelementsunderlubricatedconditions.Thewearmechanismsunderdryandlubricatedconditionswereidentifiedasadhesiveandabrasivewear,respectively.

Conclusion:

ThefrictionandwearpropertiesofNiTiSMAunderdifferentslidingconditionsandlubricationwereinvestigatedusingapin-on-disktribometer.TheresultsshowedthatthefrictioncoefficientofNiTiSMAwasaffectedbyslidingdistance,slidingspeed,andlubrication.ThewearrateofNiTiSMAwassignificantlyreducedunderlubricatedconditionsduetotheformationofaprotectivefilmoflubricant.Thewearmechanismsunderdryandlubricatedconditionswereidentifiedasadhesiveandabrasivewear,respectively.TheseresultsdemonstratetheimportanceofconsideringthesefactorswhenselectingNiTiSMAasafixationmaterialinorthopedicsurgery.

Acknowledgements:

TheauthorsacknowledgethefinancialsupportfromtheNationalNaturalScienceFoundationofChina(GrantNo.11872106),theStateKeyLaboratoryofSolidificationProcessing(NWPU),andtheFundamentalResearchFundsfortheCentralUniversities.

References:

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[11]M.Guo,Y.Zhang,T.Liu,etal.,TribologicalpropertiesandbiocorrosionofTi-30Zr-basedbulkmetallicglassesinsimulatedbodyfluid,Tribol.Int.129(2018)111-122.

[12]H.Zhu,J.Xi,Y.Yuan,etal.,BiocompatibilityandtribologicalpropertiesofmedicalTi6Al4Valloyafteralkaliheattreatment,Tribol.Int.142(2020)105996.Inadditiontotheresultsanddiscussionpresentedinthestudy,furtherresearchinthisareacouldfocusonthelong-termwearbehaviorandbiocompatibilityofNiTiSMAinorthopedicapplications.Thestudyonlyinvestigatedtheshort-termwearbehaviorundercontrolledlaboratoryconditions,whilethewearbehaviorofthematerialinthehumanbodyunderdynamicloadingconditionsismorecomplexanddifficulttopredict.Therefore,invitroandinvivostudiesareneededtovalidatethefindingsofthisstudyandassessthelong-termperformanceandsafetyofNiTiSMAinorthopedicfixation.

Moreover,thestudyonlyinvestigatedtheeffectoflubricationonthefrictionandwearbehaviorofNiTiSMA,whileotherfactorssuchastemperature,humidity,anddifferentlubricantscouldalsoaffectthebehaviorofthematerial.Therefore,futureresearchcouldfurtherexploretheeffectofthesefactorsonthefrictionandwearpropertiesofNiTiSMA.

Overall,thestudyprovidesimportantinsightsintothefrictionandwearbehaviorofNiTiSMA,whichhasimplicationsfortheselectionanddesignoforthopedicfixationmaterials.TheresultssuggestthatlubricationcansignificantlyreducethewearrateofNiTiSMA,whichcouldbeimportantforreducingtheriskofimplantfailureandimprovingpatientoutcomes.However,furtherresearchisneededtofullyunderstandthebehaviorofNiTiSMAunderrealisticconditionsandtooptimizeitsperformancefororthopedicfixationapplications.AnotheravenueforfurtherresearchinthisareaisexploringtheeffectofsurfacetreatmentsonthewearbehaviorofNiTiSMA.Surfacetreatmentmethodssuchasplasmaspraying,ionimplantation,andchemicalvapordepositioncanmodifythepropertiesofthesurfacelayerofthematerial,whichcouldenhanceitswearresistanceandbiocompatibility.Therefore,futurestudiescouldinvestigatetheeffectofthesetreatmentsonthefrictionandwearbehaviorofNiTiSMAandassesstheirsuitabilityfororthopedicfixationapplications.

Furthermore,thestudyonlyinvestigatedthewearpropertiesofNiTiSMAinaunidirectionalslidingmotion,whichmaynotaccuratelyrepresentthewearbehaviorofthematerialinmorecomplexloadingconditions.Inorthopedicapplications,theimplantmayexperiencemulti-axialloading,cyclicloading,andimpactloading,whichcouldaffectthewearbehaviorofthematerial.Therefore,futurestudiescouldexplorethewearbehaviorofNiTiSMAundermorerealisticloadingconditionstobetterunderstanditsperformanceinorthopedicapplications.

Inconclusion,thestudyprovidesimportantinsightsintothefrictionandwearbehaviorofNiTiSMA,butfurtherresearchisneededtofullyunderstandthepropertiesofthematerialandoptimizeitsuseinorthopedicfixation.ThefindingsofthestudysuggestthatlubricationandsurfacetreatmentscouldenhancethewearresistanceofNiTiSMA,andexploringthebehaviorofthematerialundermorecomplexloadingconditionsisimportantforimprovingthesafetyandefficacyoforthopedicimplants.AnotherareathatcouldbeexploredinfurtherresearchistheeffectofenvironmentalfactorsonthewearbehaviorofNiTiSMA.Inthestudy,thewearbehaviorofthematerialwastestedunderdryconditions,butinvivo,theimplantmaybeexposedtoarangeofbiologicalfluidsandenvironmentsthatcouldaffectitswearresistance.Therefore,futurestudiescouldinvestigatethewearbehaviorofNiTiSMAunderdifferentenvironmentalconditions,suchasinthepresenceofsimulatedbodyfluids,andassessthematerial’sbiocompatibilityundertheseconditions.

AnotherimportantaspecttoconsideristheeffectofagingonthewearbehaviorofNiTiSMA.Themechanicalandphysicalpropertiesofthematerialcouldchangeasitagesduetoenvironmentalfactors,suchasexposuretoheatand/ormoisture.Therefore,itisimportanttoinvestigatetheeffectofagingonthewearbehaviorofNiTiSMAtobetterunderstanditslong-termperformanceinorthopedicapplications.

Lastly,thestudyonlyinvestigatedthewearbehaviorofNiTiSMAinasingleiteration;therefore,moredetailedstudiescouldinvestigatethematerial’swearbehaviorovermultipleiterations.Thiscouldbettersimulatethereal-lifeconditionsoforthopedicimplants,whicharesubjectedtocyclicloadingandwear.Assessingthewearbehaviorofthematerialovermultipleiterationscouldprovidecrucialinformationonthematerial’slongtermwearpropertiesandhelpoptimizetheperformanceoforthopedicimplants.

Inconclusion,furtherresearchisneededtofullyunderstandthewearbehaviorofNiTiSMAandoptimizeitsuseinorthopedicfixation.Investigatingenvironmentalfactorsandagingeffects,aswellaswearbehaviorovermultipleiterations,couldprovideimportantinsightsintothelong-termperformanceofthematerialinvivo.Thisinformationcouldthenbeusedtooptimizethedesignandimplementationoforthopedicimplantsandimprovetheirsafetyandefficacy.AnotherareathatcouldbeexploredinfurtherresearchisthedevelopmentofsurfacemodificationtechniquesforNiTiSMAtoenhanceitswearresistance.Surfacemodificationcanalterthesurfacepropertiesofthematerialtoimproveitsbiocompatibilityandmechanicalproperties,andcanalsoenhanceitswearresistance.Therefore,moredetailedstudiescouldevaluatetheeffectsofdifferentsurfacemodificationtechniques,suchaspl