ThisreportisavailableatnocostfromtheNationalRenewableEnergyLaboratory(NREL)at/publications.

ContractNo.DE-AC36-08GO28308

WindTurbineDesignGuidelineDG03:YawandPitchBearings

MatthiasStammler,1OliverMenck,1YiGuo,2andJonKeller3

1FraunhoferInstituteforWindEnergySystems

2TechnicalUniversityofDenmark

3NationalRenewableEnergyLaboratory

NRELisanationallaboratoryoftheU.S.DepartmentofEnergyOfficeofEnergyEfficiency&RenewableEnergy

OperatedbytheAllianceforSustainableEnergy,LLC

TechnicalReport

NREL/TP-5000-89161July2024

NationalRenewableEnergyLaboratory

15013DenverWestParkwayGolden,CO80401

303-275-3000?

ThisreportisavailableatnocostfromtheNationalRenewableEnergyLaboratory(NREL)at/publications.

ContractNo.DE-AC36-08GO28308

WindTurbineDesignGuidelineDG03:YawandPitchBearings

MatthiasStammler,1OliverMenck,1YiGuo,2andJonKeller3

1FraunhoferInstituteforWindEnergySystems

2TechnicalUniversityofDenmark

3NationalRenewableEnergyLaboratory

SuggestedCitation

Stammler,Matthias,OliverMenck,YiGuo,andJonKeller.2024.WindTurbineDesignGuidelineDG03:YawandPitchBearings.Golden,CO:NationalRenewableEnergyLaboratory.NREL/TP-5000-89161.

/docs/fy24osti/89161.pdf.

NRELisanationallaboratoryoftheU.S.DepartmentofEnergyOfficeofEnergyEfficiency&RenewableEnergy

OperatedbytheAllianceforSustainableEnergy,LLC

TechnicalReport

NREL/TP-5000-89161July2024

NOTICE

ThisworkwasauthoredinpartbytheNationalRenewableEnergyLaboratory,operatedbyAllianceforSustainableEnergy,LLC,fortheU.S.DepartmentofEnergy(DOE)underContractNo.DE-AC36-08GO28308.FundingprovidedbytheU.S.DepartmentofEnergyOfficeofEnergyEfficiencyandRenewableEnergyWindEnergyTechnologiesOffice.TheviewsexpressedhereindonotnecessarilyrepresenttheviewsoftheDOEortheU.S.Government.

ThisreportisavailableatnocostfromtheNationalRenewableEnergyLaboratory(NREL)at

/publications.

U.S.DepartmentofEnergy(DOE)reportsproducedafter1991andagrowingnumberofpre-1991documentsareavailable

freevia

www.OSTI.gov.

CoverPhotosbyDennisSchroeder:(clockwise,lefttoright)NREL51934,NREL45897,NREL42160,NREL45891,NREL48097,NREL46526.

NRELprintsonpaperthatcontainsrecycledcontent.

Acknowledgments

AlthoughthisdocumentisareportbytheauthorsandNREL,therehasbeensubstantialsupportinthewriting.

Severalpublicmeetingshaveresultedinthisdocumentbeingsignificantlyimprovedfromtheinitialdraft.The

authorsareimmenselygratefulfortheactiveparticipationofthefollowingindividualsinthepitchandyawbearingcommunity:

HenrikAlbertsen......................................................................................IMO

ArneBartschat..................................................FraunhoferInstituteforWindEnergySystems

DanielBecker.......................................................................thyssenkrupprotheerde

EikeBlechschmidt..............................................FraunhoferInstituteforWindEnergySystems

ChristianBulligk...................................................................................Bewind

M.AjmalChoudhary...............................................................................Enercon

MartinCorrens...................................................................................Schaeffler

JensDemtr?der......................................................................................Vestas

VolkerFranzen....................................................................................Enercon

MatthisGra?mann..............................................FraunhoferInstituteforWindEnergySystems

IkerHeras..................................................................UniversityoftheBasqueCountry

MichaelHornemann..........................................................................ONYXInsight

HansAggerHougaard...............................................................................?rsted

SebastianHomberger.............................................................................Vattenfall

RhysHowells........................................................................................RWE

ThorstenJepsen...................................................................................Enercon

SamuelLeupold.........................................................................NordexACCIONA

WolfgangLosert...................................................................................Eolotec

OliverMichaelMaier.....................................................................DetNorskeVeritas

AdamMinadeo................................................................................GEVernova

CoryMittleider...............................................................................MalloyWind

MireiaOlave....................................................................................IKERLAN

MarioOliveira......................................................................................Vestas

RokPotonik.....................................................................................KISSsoft

StefanSchacht...........................................................................DetNorskeVeritas

FlorianSchleich.................................................FraunhoferInstituteforWindEnergySystems

DavidSchlüter......................................................................thyssenkrupprotheerde

FabianSchwack.....................................................................................Vestas

WooyongSong..........................................................OffshoreRenewableEnergyCatapult

NathanStang.................................................................................MalloyWind

RémiStein..........................................................................................Engie

XavierTourde....................................................................................Vattenfall

DominicVillain.........................................................................NordexACCIONA

iv

ThisreportisavailableatnocostfromtheNationalRenewableEnergyLaboratory(NREL)at/publications

RobertZell.......................................................................................Liebherr

Theauthorswouldalsoliketothanktothefollowingindividualswhoprovidedadditionalsupport:

JosuAguirrebeitia..........................................................UniversityoftheBasqueCountry

HéctorRodrigoBarral.............................................................................Iberdrola

MichaelM.Carr......................................................................................SKF

MartinGeibel...................................................FraunhoferInstituteforWindEnergySystems

WilkoGudewer....................................................................................Enercon

MatthiasKohlrusch......................................................................NordexACCIONA

NielsLerke.........................................................................................?rsted

ArkaitzLopez....................................................................................Laulagun

LilianaVicenteMenteiro..........................................................................Vattenfall

KoldoOstoloza...................................................................................Laulagun

ValentinRadigois..............................................................................GEVernova

MehrdadRahimian.............................................................................WindGuard

DayanandaRaju......................................................................................SKF

MarcReichhart.....................................................................................Eolotec

JackRobson............................................................OffshoreRenewableEnergyCatapult

DavidJ.VanLangevelde...............................................................................SKF

ChaoWang....................................................................................WindGuard

v

ThisreportisavailableatnocostfromtheNationalRenewableEnergyLaboratory(NREL)at/publications

ListofAcronyms

ABMA

AmericanBearingManufacturersAssociation

ANSI

AmericanNationalStandardsInstitute

ASME

AmericanSocietyofMechanicalEngineers

CPC

collectivepitchcontrol

DG

designguideline

DIS

draftinternationalstandard

DLC

designloadcase

DNV

DetNorskeVeritas

FE

finiteelement

FKM

ForschungskuratoriumMaschinenbau

HB

Brinellhardness

HRC

RockwellCscalehardness

HV

Vickershardnessnumber

IEA

InternationalEnergyAgency

IEC

InternationalElectrotechnicalCommission

IPC

individualpitchcontrol

ISO

InternationalOrganizationforStandardization

IWES

InstituteforWindEnergySystems

JCGM

JointCommitteeforGuidesinMetrology

kN

kilonewton

kNm

kilonewton-meter

MN

meganewton

MNm

meganewton-meter

MPa

megapascal

m/s

meterpersecond

N

newton

NREL

NationalRenewableEnergyLaboratory

TR

technicalreport

TS

technicalspecification

VDE

VerbandderElektrotechnik,ElektronikundInformationstechnik

VDI

VereinDeutscherIngenieure

vi

ThisreportisavailableatnocostfromtheNationalRenewableEnergyLaboratory(NREL)at/publications

TableofContents

Acknowledgments

iv

ListofAcronyms

vi

1Introduction

1

1.1Scope

1

1.2MainDifferencesBetweenRevisionsofthisDocument

1

1.3NormativeReferences

2

2BasicPrinciples

4

2.1PitchandYawBearingTypes

4

2.2PitchBearingCoordinateSystem

4

2.3NomenclatureofOscillations

4

2.4PitchControllerTypes

7

2.5AppliedLoad

7

2.6Truncation

7

3SummaryofDamageModesandCalculationMethods

9

3.1DamageModes

9

3.2SummaryofCalculationMethods

11

3.2.1RollingContactFatigue

11

3.2.2StaticOverloadoftheRaceways

11

3.2.3RacewayEdgeDamagesDuetoTruncation

11

3.2.4RollerMisalignment

11

3.2.5CoreCrushing

12

3.2.6StructuralFatigueofBearingRings

12

3.2.7StaticOverloadofBearingRings

12

3.2.8BoltFatigue

12

3.2.9StaticOverloadofBolts

12

3.2.10SeparationofFlangeSurfaces

12

3.2.11SeparationofSealingSurfaces

12

4FiniteElementModelsofYawandPitchBearings

13

4.1PurposeofFiniteElementModels

13

4.2ChecksandValidationofFiniteElementModels

13

4.3ModelTypes

13

4.4ConsiderationofInterfaceParts

14

4.5FrictionalContacts

14

4.6ParameterStudies

15

4.7LoadCaseSelectionforGlobalModels

15

4.8ExampleApproaches

17

4.8.1RollingBodyandBoltModeling

17

4.8.2LoadApplicationonRotorBlades

18

4.8.3FiniteElementStudiesforReplacements

19

5CalculationofBearingFatigueLife

20

5.1TypesofBearingFatigue

20

5.2RollingContactFatigue

20

5.2.1Lundberg-PalmgrenTheory

20

5.2.2PreprocessingofTimeSeries

21

5.2.3ExperimentalValidation

21

5.2.4BasicDynamicAxialLoadRating

21

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5.2.5DynamicEquivalentAxialLoadandBearingRatingLife

23

5.2.6ModifiedRatingLife

27

5.2.7LifeModificationFactorforMaterial

28

5.2.8LifeCalculationforOscillatingBearings

29

5.2.9CombinedLifeUnderAllOperatingConditions

30

5.2.10ServiceLifeModificationFactor

31

5.2.11TruncationandCoreFatigue

31

5.2.12SmallOscillationsandContactAngleVariations

31

5.3StructuralFatigue

31

5.3.1CriticalLocations

32

5.3.2CalculationAspects

32

6BearingStaticStrength

33

6.1General

33

6.2PermanentDeformation

33

6.3MaximumBallorRollerLoad

34

6.3.1SimplifiedMethod

34

6.3.2FiniteElement-BasedMethod

34

6.4MaximumContactStress

35

6.5ContactDimensions

35

6.5.1PointContact

35

6.5.2LineContact

36

6.6StaticSafetyFactor

37

6.6.1EffectofSurfaceHardnessonStaticCapacity

38

6.7TruncationandCoreCrushing

38

6.8StructuralStrength

38

7EffectiveLubricationandWearPrevention

40

7.1General

40

7.2GreaseSelection

40

7.3RelubricationIntervals

40

7.4WearPrevention

41

8BearingFrictionTorque

42

8.1General

42

8.2Four-PointContactBallBearings

42

8.3OtherBearingTypes

42

8.4InfluenceofSealsandBoltPretension

42

9MiscellaneousDesignConsiderations

43

9.1ProductionProcess

43

9.2Truncation

43

9.3ConsiderationsfortheHardenedLayer

43

9.3.1DesignStresses

43

9.3.2AllowableShearStressesforYieldandFatigue

44

9.3.3CalculationofSubsurfaceShearStress

44

9.3.4EvaluationofCoreStresses

45

9.4BoltsandStuds

46

9.4.1Design

46

9.4.2Tightening

47

9.5CageDesign

47

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9.6Seals

47

9.7CorrosionProtection

48

9.8FlatnessofInterfacingParts

48

9.9MonitoringofPitchandYawBearings

48

9.9.1DriveTorque

48

9.9.2GreaseSampling

48

9.9.3OtherApproaches

48

10Testing

49

10.1General

49

10.2TestTargets

49

10.3ExampleTestMethods

50

10.3.1ValidationofFiniteElementModels

50

10.3.2DeterminationofFrictionTorque

50

10.3.3RollingContactFatigue

50

10.3.4CageWear

51

10.3.5RacewayWear

51

10.3.6StructuralFatigue

52

10.3.7LubricantQualifications

52

References

60

AppendixAWindTurbineYawBearing

61

A.1BearingDescriptionandOperatingConditions

61

A.2BearingFatigueLife

62

A.2.1BasicDynamicAxialLoadRating

62

A.2.2DynamicEquivalentAxialLoad

63

A.2.3CombinedBasicRatingLife

64

A.2.4ModifiedRatingLife

64

A.3BearingStaticStrength

65

A.3.1MaximumBallLoad

65

A.3.2ContactDimensions

65

A.3.3MaximumContactStress

66

A.3.4StaticSafetyFactor

66

A.4MiscellaneousDesignConsiderations

66

A.4.1Truncation

66

A.4.2ConsiderationsfortheHardenedLayer

67

AppendixBWindTurbinePitchBearing

68

B.1BearingDescriptionandOperatingConditions

68

B.2FiniteElementModels

68

B.3BearingFatigueLife

68

B.3.1BasicDynamicAxialLoadRating

68

B.3.2DynamicEquivalentAxialLoadandBasicRatingLife

69

B.3.3CombinedBasicRatingLife

71

B.3.4ModifiedRatingLife

75

B.4BearingStaticStrength

75

B.4.1MaximumBallLoad

75

B.4.2ContactDimensions

76

B.4.3MaximumContactStress

77

B.4.4StaticSafetyFactor

77

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B.5MiscellaneousDesignConsiderations

77

B.5.1Truncation

77

B.5.2ConsiderationsfortheHardenedLayer

78

ListofFigures

Figure

1.Pitchandyawbearingtypes

4

Figure

2.Pitchbearingcoordinatesystem

5

Figure

3.Definitionoftheoscillationangle

5

Figure

4.Contacttrackandoscillationamplituderatioforpointcontact

6

Figure

5.Contacttrackandoscillationamplituderatioforlinecontact

6

Figure

6.Contactanglechangeandtruncatedcontactellipse

8

Figure

7.Possibledamagelocationsinpitchandyawbearings

9

Figure

8.Crackedringofapitchbearing

11

Figure

9.Sectionofabearingmodelandsubmodel

14

Figure

10.One-thirdoftherotorwithcyclicsymmetricboundaries

15

Figure

11.Exampleloadcases

16

Figure

12.Bladeazimuthangle

17

Figure

13.Bearingsegment,non-linearsprings,andlinearsprings

17

Figure

14.Boltmodels

18

Figure

15.Bearingnomenclature

22

Figure

16.Boreholemodels

32

Figure

17.Schematicoftwosolidelasticcurvedbodiescompressedtogether

36

Figure

18.Actualandpermissibleshearstressoverdepth

44

Figure

19.Allowablestress

45

Figure

20.Subsurfacestressparameter

45

Figure

21.Exampletensioningsequence

47

Figure

22.Pitchbearingtestrig

49

Figure

23.Sandwich-typetestrig

51

Figure

A.1.YawbearingfortheInternationalEnergyAgency(IEA)15-MWreferencewindturbine

61

Figure

B.1.Type12480pitchbearingforIWT7.5-164referencewindturbine

68

Figure

B.2.Pitchmovementpertimestepoffile1.1_s20112.txt

73

Figure

B.3.Firsttimestepofthesampletimeseries1.1_s20112.txtinthegridoffiniteelementsimulations

.

74

Figure

B.4.Usableraceway

78

Figure

B.5.PermissibletruncationforIWTpitchbearing

78

x

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ListofTables

Table

1.Possibledamagemodesandlocationsinpitchandyawbearings

10

Table

2.Valuesoffcforthrustballbearings

22

Table

3.MultipliersforTable2toobtainfcforothergrooveconformities

23

Table

4.Valuesoffcforrollerbearings

23

Table

5.Lifemodificationfactorforreliability

28

Table

6.Conversionfactorsfordifferentunits

31

Table

7.Maximumstaticstresses,σmax,forapermanentracewaydeformationmagnitudeof0.0001Dw

33

Table

8.Valuesofa*andb*versusF(ρ)

39

Table

9.Effectofhardnessonhardnessreductionfactor,ηs

39

Table

10.Allowablesubsurfaceshearstresses

44

Table

11.Subsurfaceshearstressparameter,ζ,versusz/bandb/a

46

Table

12.Nomenclature

53

Table

A.1.IEA15-MWyawbearingbasicgeometricandmaterialparameters

62

Table

A.2.IEA15-MWyawbearingdetailedgeometricparametersandbasicdynamicaxialloadratings

63

Table

A.3.IEA15-MWyawbearingloadspectrum

63

Table

A.4.IEA15-MWyawbearingbasicratinglives

64

Table

A.5.IEA15-MWyawbearingmodifiedratinglives

65

Table

A.6.IEA15-MWyawbearingstaticstrengthparameters

66

Table

A.7.IEA15-MWyawbearingshearstrengths

67

Table

B.1.IWT7.5-164pitchbearinggeometricandmaterialparameters

69

Table

B.2.IWT7.5-164designloadcase(DLC)multipliers

72

Table

B.3.IWT7.5-164pitchbearingstaticstrengthcalculations

76

xi

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1Introduction

1.1Scope

This

designguideline(DG)

describesthedesigncriteria,calculationmethods,andapplicablestandardsrecom-

mendedforuseinperformanceandlifeanalysesofballandroller(rolling)bearingsforyawandpitchmotionsup-portinwindturbineapplications.Theformulaepresentedhereforrollingbearinganalyticalmethodsandbearing-liferatingsareconsistentwithmethodscurrentlyusedbywindturbinedesignersandrollingbearingmanufacturers.

Theoriginalyawandpitchbearing

DG

wasfirstdraftedin1999byindustrymembersandfinallypublishedin2009bythe

NationalRenewableEnergyLaboratory(NREL)

(Harris,Rumbarger,and