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toMetalstoEnginebearings

Enginebearingfailure

Dr.DmitriKopeliovich

Enginebearingsaresmallandrelativelyinexpensivecomponentsofinternalcombustionengineshoweverfailureofanenginebearingcommonlyleadstoseriousreconditioningworksoftheengineincludingitsdisassembling,regrindingthecrankshaftandreplacingthebearings.

Factorsaffectingnormalfunctioningofenginebearings:

Propertiesofenginebearingmaterials:Fatiguestrength(loadcapacity)Seizureresistance(compatibility)WearresistanceConformabilityEmbedabilityCorrosionresistanceCavitationresistance

Bearingsdimensions:DiameterLengthThicknessOilclearance

Parametersoftheinternalcombustionengine,whichdeterminesfunctioningconditionsofthebearings:

Theenginetype(gasoline,dieselwithdirectfuelinjection,dieselwithindirectfuelinjection).Compressionratio.Rotationspeed.Aspirationtype(naturallyaspirated,turbocharged,supercharged).Combustionparameters.

Lubricationsystem:Oilpressureandflowrateprovidedbytheoilpump.Oilsupplythroughtheoilfilter,oilpassagesandthebearingsoilholes.Leveloftheoilcontamination.

Geometryimperfectionsandmisalignment:

7/26/2015 Enginebearingfailure[SubsTech]

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Excessiveorinsufficientbearingcrush.Bearingbacknonconformedtotheroundhousingbore.Improperlygroundhousingbore.Improperlygroundjournal(tapershape,barrelshape,hourglassshape).Excessivefilletofthejournal.Distortedconnectingrod.Distortedcrankcase.Distorted(bent)crankshaft.RoughCrankshaftsurface.

Engineworkconditions:Workunderhightorqueatlowrotationspeed(climbing)foralongperiod.Workatarotationspeedbeyondtheupperlimit.Nonauthorizedimprovementsoftheengineforpowerincrease.

ThemajortypeofenginebearingfailureisFatigue.Fatigueofenginebearingmaterialsiscausedbyrunningthebearingataloadabovethefatiguelimit.

Thecausesofenginebearingfatigue:

WrongselectionoftheEnginebearingmaterialsfortheapplication.Localizedloadingofthebearingduetoamisalignment(eg.hourglassjournal,distortedconnectingrod).Fueldetonationcausedbyadvancedignition.Runningtheengineunderhighloads(torque)atlowrotationspeedsforlongperiod.Poorconformingofthebearingbackwiththehousingsurface.Overfueling.Corrosiveactionofcontaminatedoil,whichlowersthefatiguelimit(Corrosionfatigue).

Typesofenginebearingfailure:

FatigueofoverlayFatigueofcopperbasedliningFatigueofaluminumbasedliningMetaltometalcontactBentortwistedconnectingrodImperfectjournalgeometryCavitationerosion

Fatigueofoverlay

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Fatigueofanoverlayappearsinformofanetworkofthincracks.

Thinneroverlaysformthinnerfatiguecracks.

Fatiguelimitofanoverlayisdeterminedbythestrengthofthematerialandthethicknessoftheoverlay.Thethinnertheoverlaythehigheritsfatiguestrength.

Overlayfatigueitselfdoesnotcausetheenginefailure.

Howeverrunningthebearingwithfatiguedoverlayforalongtimemaycausepartialflakingoftheoverlayandloweringtheoilfilmthickness.

Theconditionsforboundarylubricationoccurredatlowoilfilmthicknessleadtoexcessivewearandlocalizedloading,whichmayresultinthefailureofthelining(intermediatelayer).

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Fatigueofcopperbasedlining

7/26/2015 Enginebearingfailure[SubsTech]

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Fatigueofacopperbasedliningstartsfromfatigueoftheoverlay.

Theoverlayflakesoutfromthecopperliningresultinginbreakingtheoilfilmandchangingthelubricationregimefromhydrodynamictoboundary.

Theloadlocalizesatthecontactareacausingformationofsmallcracksontheliningsurface.

Thecracksthenspreadthroughouttheliningthickness,meetthesteelbacksurfaceandcontinuetoadvancealongthesteelcopperboundary.

Asaresultpartsoftheintermediatelayerdetachfromthesteelsurface.

Fatigueofcopperliningcausesimmediateenginefailure.

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Fatigueofaluminumbasedlining

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Appearanceoffatigueofaluminumbasedliningissimilartothatofcopperbaselining.

Itisalsoresultofoverloadingcausedbyrunningtheengineunderhighloads(torque)atlowrotationspeedsforlongperiod,localizedloadingofthebearingduetoamisalignment,fueldetonationorotherfactors.

Thefatiguecracksformonthesurfaceandspreadinsidetheliningreachingthesteelback.

Thecracksthenprogressalongthebondlinebetweentheliningandthesteel.

Piecesoftheliningflakeoutfromthesteelbackresultingintheenginefailure.

Fatigueofaluminumalloysmayalsocauseextrusionoftheliningmaterialoutofthebearingedges.

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Metaltometalcontact

7/26/2015 Enginebearingfailure[SubsTech]

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Metaltometalcontact(boundarylubrication)maybearesultofdifferentfactors:

Insufficientoilconditions(oilstarvation).BreakingtheoilfilmcausedbythebearingmaterialFatigue.Misalignment(eg.hourglassjournal,distortedconnectingrod).Poorjournalsurfacefinish.Foreignparticlesembeddedintothebearingsurface.

Metaltometalcontactmayappearinthefollowingforms:

Acceleratedwear:thebearingisnotoverheated(shiningappearance).Wiping:thebearingisheavilyworn(overlayispartiallydisappeared),therearesignsofoverheating(blackening),partialmeltingoftheoverlay.Anexampleofawipedbearingispresentedontheleftpartofthepicture.HotShort:severewear,tornsurface,heavyoverheating,meltedoverlayandliningmaterial.AnexampleofaHotShortbearingispresentedontherightpartofthepicture.

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Bentortwistedconnectingrod

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Distorted(bentortwistedconnectingrod)isoneofthecausesoflocalizedloadingofenginebearings.

Overloadingofaninternalcombustionengineduetodetonationorrunningunderhightorqueatlowrotationspeedmaycausedistortionoftheconnectingrods.

Thedistortionresultsinnonparallelorientationofthebearingandjournalsurfaces.

Themisalignmentcauseslocalizedexcessivewearofthebearingsurfaceduetometaltometalcontact(boundarylubrication)occurringnearthebearingedge.

LocalizedmetaltometalcontactmayalsocauseFatiguecrackingoftheEnginebearingmaterialsinthelocationsofthecontact.

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Imperfectjournalgeometry

7/26/2015 Enginebearingfailure[SubsTech]

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Imperfectjournalgeometryisalsoacauseoflocalizedloadingofenginebearings.

Useofawornstoneingrindingacrankshaftresultsinobtaininganimperfect(outofshape)journalsurface:tapershape,hourglassshapeorbarrelshape.

Thepartsofthejournalsurfacehavinghigherdiameter(centralpartofthebarrelshapejournal,edgepartsofhourglassshapejournal)cometometaltometalcontact(boundarylubrication)withthebearingsurface.

Themetaltometalcontactcausesexcessivewear.

FatiguecrackingoftheEnginebearingmaterialsmayoccurinthecontactareas.

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Cavitationerosion

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Cavitationoccurswhentheloadappliedtothebearingfluctuatesathighfrequency(highRPM).

Theoilpressureinstantlyfallscausingformationofcavitiesduetofastevaporation(boiling).

Whenthepressurerisesthevaporcavities(cavitationbubbles)contractathighvelocity.Suchcollapseresultsinimpactpressure,whichmayerodethebearingmaterial.

Theoilpressurecreatesasupportingforceseparatingthejournalfromthebearingsurface.

SoftLeadbasedenginebearingoverlaysoftrimetalbearingsarepronetothecavitationerosion.

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Relatedinternallinks

BearingsininternalcombustionenginesEngineparametersdeterminingbearingloadingLubricationregimesHydrodynamicjournalbearingHydrodynamiclubricationtheoryGeometricalparametersofenginebearingsMechanismsofwearRequirementstoenginebearingmaterialsEnginebearingfatiguetest

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EnginebearingmaterialsCopperbasedbearingmaterialsManufacturingbimetalstripsforcopperbearingsAluminumbasedbearingmaterialsContinuouscastingofaluminumbasedbearingalloysManufacturingbimetalstripsforaluminumbearingsLeadbasedenginebearingoverlaysTinbasedenginebearingoverlaysSputterbearingoverlaysPolymerbasedenginebearingoverlaysSelectionofenginebearingmaterialsEffectoflowviscosityoilsonenginebearingspMaxBlackStrengthenedTrimetalBearingMaterialsforHighPerformanceBearingsUGrooveModifiedDesignofOilGrooveforHighPerformanceBearingsElliptiXOilHoleofNewDesignforHighPerformanceBearingsEccentriXOptimalEccentricityforHighPerformanceBearingsRadiaLockDesignofCrushHeightforReliablePressFitofHighPerformanceBearingsModernTrendsInMaterialsForHighPerformanceEngineBearingsOptimizationofClearanceDesignforHighPerformanceEngineBearingsCamshaftBearingsEcologicalAspectsOfEngineBearingsFatigue

Relatedexternallinks

http://www.waukbearing.com/downloads/Material_For_Plain_Bearings.pdf[http://www.waukbearing.com/downloads/Material_For_Plain_Bearings.pdf]http://www.ilot.edu.pl/Journal%20of%20KONES%202004/01/46.pdf[http://www.ilot.edu.pl/Journal%20of%20KONES%202004/01/46.pdf]http://www.marinediesels.info/2_stroke_engine_parts/Other_info/bearing_materials.htm[http://www.marinediesels.info/2_stroke_engine_parts/Other_info/bearing_materials.htm]

toMetalstoEnginebearings

engine_bearing_failure.txtLastmodified:2015/03/12bydmitri_kopeliovich

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