VW 01131-1-201202 Eng摩擦系数的测定实际定向试验

GroupStandardVW01131-1

Issue2012-02

Class.No.:01712

Descriptors:coefficientoffriction,threadedjoint,testbolt,testnut,tighteningtorque,practice-orientedtesting

DeterminationofCoefficientsofFriction

Practice-andMounting-OrientedTesting

Preface

DINENISO16047

stipulatesstandardizedconditionsforperformingtorque/preloadforcetestsformechanicalfastenerswhoseresultsoftencannotbeappliedtouseinproduction.Forinstance,

boltsandnutsareusuallytightenedinseveralstageswithfastpre-tighteninginordertoshortenassemblytime.Thefinaltighteningisusuallyperformedat20min-1,oftenbeyondtheyieldpoint.Additionalfriction-influencingfactorsbecomeeffectivewithlargeranglesofrotation.

Thefriction-influencingfrictionpartnersoftheboltsandnutscanhaveverydiversesurfacetex‐

tures.Specialrequirementsresultfromverysmoothandcohesivesurfacesorsurfacesthatare

veryroughduetotheprocessingandmaterialstructure.Moreover,fasteningonpaintedpartscancausesurfacedamage,e.g.,duetotheunavoidablethermalstressesoncathodicallyelectrocoatedpartsduringfastscrew-inoperations,whichresultsinextremefrictionconditionsandoftenprodu‐cesundesiredeffects.Also,screwingboltsintodeepthreadedholesorinsertnutswithengage‐

mentlengthsover2xdplacesspecialrequirementsoncoatingsystemsforrelativelysoftmaterialssuchasunquenchedanduntemperedsteel,castiron,aluminum,andmagnesium.

Insomeapplications,e.g.forwheelbolts,themountingisperformedmultipletimeswiththefasten‐ingstagesoftightening,loosening,andfinaltightening.Multipletighteningoperationsmustalsobetakenintoconsiderationinthecaseofrework.Contrarytostandardizedlaboratorytests,thesepro‐ductionconditionsusuallygeneratehighercoefficientsoffrictionwithsometimessignificantlylargerdispersion.

Previousissues

VW01131-1:2010-02

Changes

ThefollowingchangeshavebeenmadecomparedwithVW01131-1:2010-02:

Page1of12

VerifythatyouhavethelatestissueoftheStandardbeforerelyingonit.

ThiselectronicallygeneratedStandardisauthenticandvalidwithoutsignature.

TheEnglishtranslationisbelievedtobeaccurate.Incaseofdiscrepancies,theGermanversionisaloneauthoritativeandcontrolling.

Numericalnotationacc.toISO/IECDirectives,Part2.

Technicalresponsibility

NQ-HKMarkus

Gentemann

Tel.:

+495117985151

StandardsDepartment

EKDV/4Uwe

Stüber

EKDV

Tel.:

+495361929063

ManfredTerlinden

Allrightsreserved.NopartofthisdocumentmaybeprovidedtothirdpartiesorreproducedwithoutthepriorconsentoftheStandardsDepartmentofaVolkswagenGroupmember.

©VolkswagenAktiengesellschaftVWNORM-2012-05i

Page2

VW01131-1:2012-02

–

Section1"Scope"

changed

–

Section3"Requirements"

changedandexpandedby

Section3.2"Firstsampling"

–

Section4"Testingpartsandreferenceparts,headcountersurfaces"

rearranged

–

Section4.2"Testnut,referencescrew"

and

Section4.3"Threadedjointonpaintedsurfaces"

,specificationsofmaterialschanged

–

Section4.5"Testingofaluminumscrews"

new

–

Section4.6"ProcuringtheDUTs,referenceparts,andheadcountersurfaces"

new

–

Section5"Testprocedure(testsequenceforthethreadedjoint)"

,detailsadded

–

Section7"Applicabledocuments"

updated

–Standardedited

Contents

Page

1

Scope

2

2

Termsandsymbols

3

3

Requirements

4

3.1

Generalrequirements

4

3.2

Firstsampling

4

3.3

Partspreparation

5

4

Testingpartsandreferenceparts,headcountersurfaces

6

4.1

Testbolt,referencenut

6

4.2

Testnut,referencescrew

6

4.3

Threadedjointonpaintedsurfaces

7

4.4

Threadedjointsonandincastmaterials

8

4.5

Testingofaluminumscrews

9

4.6

ProcuringtheDUTs,referenceparts,andheadcountersurfaces

9

5

Testprocedure(testsequenceforthethreadedjoint)

9

6

Evaluation

11

7

Applicabledocuments

12

1Scope

Asasupplementinsomeareasandalsoindeviationfrom

DINENISO16047

,thisStandardde‐

scribestestsetupsandtestproceduresfordeterminingthecoefficientsoffrictionasper

VW01129

.Thetestprocedurerepresentsthegeneralprinciplesfordeterminingcoefficientsoffric‐

tionatroomtemperature,whichformthebasisforallfurtherexaminations.Theexaminationsof

faultsinthefasteningprocessaresimulatedandevaluatedasclosetofieldconditionsaspossible.Thereleasetestswithinthetestingofsamplesarebasedonthisprocedure,butcanbeperformedinasimplifiedmethodifthereissufficientexperienceonthebehaviorofthecoefficientsoffrictionfromfamiliesofsimilarparts.

Page3

VW01131-1:2012-02

2Termsandsymbols

See

table1

.

Table1

Symbol

Definition

In

DINENISO16047

as

d

Nominaldiameterofthethread

d

d2

Pitchdiameteroftheexternalthread(

DIN13-1

)

d2

dh

Diameterofthethrough-holeofthewasherorbearingplate

dh

Dkm

Effectivediameterforthefrictiontorqueintheboltheadornutbearingsurface

(theoreticalormeasured)

Db

dW

OutsidediameterofthebearingsurfacedW,minordk,min(seeproductstandard)

D0

FV

Preloadforce

F

P

Lead

P

MA

Tighteningtorque

T

MK

Frictiontorqueinthebearingsurface

Tb

MG

Threadtorqueintighteningdirection

Tth

ML

Threadtorqueinlooseningdirection(looseningtorque)

-

MLG

Looseningtorque,atthetimeofslidingfriction

-

MLH

Looseningtorque,atthetimeofstaticfriction(breakawaypeak)

-

µtotal,loosening,

150°C

Totalcoefficientoffrictionforlooseningat+150°C

-

µtotal,tightening,

RT

Totalcoefficientoffrictionfortighteningatroomtempera‐ture

-

µk

Coefficientoffrictioninthenutandheadbearingsurfaces

μb

µg

Coefficientoffrictioninthethreadintighteningdirection

μth

µg,loosening

Coefficientoffrictioninthethreadinlooseningdirection

-

µtotal

Totalcoefficientoffriction

µtot

µtotal,RT

Totalcoefficientoffriction(intighteningdirectionatroomtemperature)

-

Page4

VW01131-1:2012-02

3Requirements

3.1Generalrequirements

Duetoverydifferentinitialconditionsandawiderangeofmeasurementequipment,coefficientoffrictiontestscanbecomparedonlyifthetestconditionsarespecifiedwithinnarrowlimits.The

mainfocusofthisStandardispractice-orientedtesting,inorderalsotoobtaincorrelationswithex‐periencesfrommountingprocedures.

Theconditionsrelevantforthethreadedjointmustbesimulatedasclosetofieldconditionsaspos‐sible.Thisincludesthreadelements,theheadbearingsurface,thethreadedjointtypehardness,

aswellastheclampinglengthandengagementlength.Athreadprojectionofatleast3×P(better1×d)mustbeensuredonprinciple.Thethreadedjointmustbetightenedbasedonproduction

conditionswithatestbedthatcorrespondstothestateoftheart.Becausethestiffnessofthetestbedcanbeinfluencedonlyminimallyanduptonowtherearenovalidspecifications,thedecisivefactorsforthesuitabilityofthetestbedaretheadjustmentofthecontrol,drive,andmeasurementequipmenttotheexpectedmeasurementrangeandthelowestpossibleinertia.Thespecificationsforspeedandtorqueshutoffandswitchingpointsmustbeobserved.

Therequirementsforthethreadedjointtestbedaredescribedin

DINENISO16047

anddefinedmorepreciselyinthefollowing:

Thethreadedjointtestbedmustbeabletoimplementhighscrew-inspeeds(standardtargetvalue200min-1)andintermittent,multiple-stagetightening(pre-tightening,stop,finaltightening),since

theseconditionscancausefasteningproblemsthatmightnotbedetectedatlowtestspeeds

and/orwithone-stagetighteningforcertainheadbearingsurfacegeometriesandsurfacepairings.Furthermore,itmustbepossibletoperformandevaluateuptofourrepeatedfasteningprocesses.Thecontrol,drive,andmeasurementequipmentthatisusedmustbematchedtothethreaddiam‐eter,sothatthemeasurementrangesforthetorquesandpreloadforcesaresensiblymatchedtothenominalvaluesofthetestingequipment.Inparticular,measurementsinthelowermeasure‐

mentrange(<10%ofthenominalvalues)mustbeconsideredascriticalhere.

3.2Firstsampling

Forthefirstsamplingofstandardparts,drawingparts,ormulti-usepartswithmetricthreads,test

proceduresandtestingstrategiesthatdeviatefromthespecificationsof

VW01129

maybeused

onthebasisofbasicresearchonfamiliesofpartsanalogoustothisstandard.Pleasenotethat,intheeventofadispute,thetestsinthespecifiedscopeandintheprocedureasper

VW01129

mustbepassed.

Specialcasesareveryshortorlongthreadedparts,verylargeorsmalldiameters,partswith

threadprotection,basematerialsotherthansteel(e.g.,aluminumscrews),orintermediatesizes.

Thesespecialcasesmaketheprocurementoftestpartsandreferencepartsand/orthetestproce‐duremoredifficult,sothatspecialtestsarepossiblehere(withothertestspecificationsor,e.g.,

onlythemostseveretestingagainstaluminumheadbearingsurfaces).Theinitialconditionsthatarethenvalidmustbespecifiedindividually.

Page5VW01131-1:2012-02

3.3Partspreparation

New,unusedparts(bolts,nuts,headbearingsurfaces)mustbeusedforeachtest.Reference

parts(e.g.,greasedforlong-termstorage)mustbethoroughlycleanedbeforefastening.Anexam‐pleofthecleaningprocess(threestageswithcleaner'snaphthaintheultrasonicbath)isshownin

figure1

butitcanbedifferentdependingonthepre-treatmentandgreasingoftheparts.Ifrepea‐

tedfasteningprocessesarecarriedoutduringthetest,thedescribedcleaningprocessmustbe

performedonlyonceatthestartofthetests.However,thecleaningprocessdoesnotapplytotestswithproductionpartsthatmustbeusedintheas-deliveredconditionandwithoutanychangesto

theirpropertiesifpossible.

Figure1–Three-stagecleaningprocessforreferenceparts

–Petroleumetherascleaningagent(specialboilingpointfluid,fraction80°C/110°C,Volkswagenmat.no.A290008orsimilar)

–Cleaningagentmustbereplacedafterapprox.20cycles.

Page6

VW01131-1:2012-02

4Testingpartsandreferenceparts,headcountersurfaces

Onprinciple,thepertinentsample,production,orproblempartsmustbeusedforthetests.Ifthesecannotbeusedforgeometricalorfunctionalreasons,alternativepartsmustbeusedthatproducetheoriginalthreadedjointtypeascloselyaspossible.Thefollowingbasicrulesforpartselection

mustbeobserved:

4.1

Testbolt

Testbolt,referencenut

–Flangeboltofsufficientlength,propertyclass10.9ifpossible,toallowhighpreloadforces.

–Thethreadtolerancezonepositionisimportantforthefunctionofthethread.Thethreadforboltswithgalvaniccoatingsystemsmusthavebeenmadeasper

VW11624

(tolerance

class6f)andforzincflakecoatingsystemsasper

VW11627

(toleranceclass6e)inordertostillprovideenoughclearanceforthepairingwithnutthreadsoftolerancezoneposition6H.Impactmarkshaveanegativeeffect,whichmustbeeitherassessedorexcluded.

–Inthespecialcaseofflangeboltswithconcaveheadbearingsurfaces(e.g.,asper

DINEN1665

,concavebolt),theouterareaoftheunderheadbearingsurfacemakesfirstcon‐tactinaring-shapedpattern.Combinedwiththehighercircumferentialspeedincomparison

withconvexbolts,thisincreasesthermally-inducedfrictiondisturbanceswithsignificantlyhigh‐ercoefficientsoffriction,whichcanleadto"stick-slip"effects.Thetestresultsareonlycondi‐tionallycomparable.

Referencenut(fortestsonbolts)

–Preferablysquareweldnuts,hightype,acc.to

VW60449

–Threadacc.to

VW11624

–toleranceclass6G

–Surfacec340(unalloyedzinccoating,thinlayerpassivationwithoutpost-treatmentacc.to

VW13750

andTechnicalSupplySpecification

TL217

)

Thesepartsarestandardpartsandcanbeeasilysecuredagainstrotation.Theyhaveade‐quateengagementlengthsandstrengthforhighpreloadforces,andtheyhavearelativelyneutralbehaviorwithrespecttomanysurfacecoatingsystems.

4.2Testnut,referencescrew

Iffasteningisperformedonthenutside(thenutasthedeviceundertest(DUT)andtheboltas

referencepart),thesetupinthetestbedmustbereversed.Inparticular,anadequatethreadpro‐jection(atleast3×P)fromthenutmustbeobserved.

Testnut

–Forflangenuts,thenotesonflangebolts(see

section4.1

)concerningthedimensionsandheadbearingsurfaceapplyanalogouslytothetestnut.

–Iforiginalpartscannotbeused,comparablenutthreadpartsmustbeusedthatmatchwithregardtodesign,propertyclass,andsurface.

Referencebolt(fortestsonnuts)

–Hexagonheadboltasper

DINENISO4017

/

DINENISO8676

orcomparable,preferablywithsurfacec340(asper

VW13750

and

TL217

).

–Propertyclass8or10,dependingontheDUTandthreadasper

VW11624

(toleranceclass6f)

Page7VW01131-1:2012-02

4.3Threadedjointonpaintedsurfaces

Inthreadedjointsonspecialsurfaces,e.g.,onthefrequentlyoccurringcathodicallyelectrocoated

surfacesinthechassisarea,increasedunderheadfrictionwith"stick-slip"effectscanoccurin

combinationwithhigherscrew-inspeeds.Thesespecialconditionsserveasastandardforthefric‐tioncoefficientexaminations,whichiswhyperforatedsheetsthatarecathodicallyelectrocoated

underproductionconditionsareusedascountersurfaces.Whentheseareused,caremustbetak‐entoavoiddeflections.Useonbothsidesisonlyusefulinexceptionalcasesandmustbeavoided.Inordertoensurecomparabilityofthetestresultstothelargestextentpossible,thefollowingre‐

quirementsmustbeobserved(deviationsmustbeagreeduponwiththetestdepartmentandmustbedocumented):

Headcountersurface

Atestsheetisshownin

figure2

asanexample.

–Bodysheet(

DINEN10111

–DD12,unalloyedhot-rolledstripsteel,max.hardness130HV)

–Sheetthickness:2mm

–Throughholeacc.to

DINEN20273

,mediumseries

–Single-layercathodicelectrocoating(cathodicelectrocoatingasper

QPF087

):blackcolor,

zincphosphatingpre-treatment(e.g.,Bonder153/Granodine1994),totallayerthickness=(20±

3)µm

–Cathodicelectrocoatingmaterial:

AquaEC3000madebyDuPontHellac,consistingoftwocomponents:

1.Binder(materialno.ALE017100)

2.Pigmentpaste(materialno.ALE017043)

Alternativeforspecialcases:

EnviroprimeGeneration6DOTOmadebyPPG

Sheetmetalpartswithcomparableproperties(strength,bearingsurface,andcoating)maybe

agreeduponwiththepurchaser,whereinespeciallythefactors"elasticity"and"protectionagainstrotation"mustbeobserved.

Figure2–Perforatedbodysheetwithblackcathodicelectrocoating

Page8

VW01131-1:2012-02

4.4Threadedjointsonandincastmaterials

Thesimulationofthethreadedjointclosetofieldconditionsisoftennoteasilypossibleonthetestbedduetoengagementlengthsandpartlengths.Asanalternative,divisionintotwoseparatetestswithproductionpartsisfeasible.Inthiscase,theoriginalboltispartofeachseparatetest.

Inthefirststep,thethreadfrictionandthescrew-intorqueathighspeedscanbedeterminedusingtheoriginalnutthreadandastandardcathodicallyelectrocoatedperforatedsheetasheadbearingsurface.Inthesecondstep,thematchingreferencenut(squareweldnut)mustbeusedtogether

withtheoriginalheadbearingsurfacetodeterminetheunderheadcoefficientsoffriction.Bothtestpartscombinedcreatethecompletepicturefortheinteractionofthesurfacecoatingwiththecastmaterials.

Ifthesimulationclosetofieldconditionsisfundamentallynotpossibleduetoalackofusablepro‐ductionparts,ataminimumthetestofheadfrictioncoefficients–especiallyunderhighpreload

force–mustbesimulatedonthetestbedasasubstitute.Thisalternativetestisalsopartofthe

releasetestsfornewsurfaces(see

VW01131-2"DeterminationofCoefficientsofFriction;Release

ofNewSurfaceCoatingSystems"

).Thereferencenuttobeusedmustbeselectedasperthespe‐cificationsfrom

section4.1

.Themetrologicalboundaryconditions(suchastemperatureandhu‐

midity)mustbedocumentedsinceinfluencesontheresultcannotbeexcluded(see

section6

).

Headcountersurface

Analuminumperforatedstripisshownin

figure3

asanexample.

–AluminumperforatedstripmadefromAlSiMgMnasperENAW-6082,T651asper

DINEN573-3

,

DINEN485-1

,

DINEN485-2

,and

DINEN485-3

–Sheetthickness≥5mm(topreventdeflection)

–Throughholeacc.to

DINEN20273

,mediumseries,freeofburrs

–Strengthand/orhardnessintheprocessedcondition(100±20)HB

–Surfacemilledandsubsequentlyfinishcut,Rz=(15±5)μm

Thestripscanbeusedseveraltimesafterthesurfacehasbeenmilledagain.

Figure3–Aluminumperforatedstrip

Page9VW01131-1:2012-02

4.5Testingofaluminumscrews

Thetestingisconductedanalogoustosteelscrews,butwithadaptedparameters.Thismethodispreferredbecausethefrequentpairingwithlightmetalnutthreadscanbetestedonlyonoriginalparts.Alternatively,thepairingwithsteelnutsisalsousefulforthetestingofbasicsuitability.Theheadcoefficientsoffrictionthatarereachedoncathodicallyelectrocoatedperforatedstripsand

aluminumperforatedstripsarecomparable.Thefollowingspecificationsmustbeusedasabasisfortheparameterizationforfinaltightening(tighteningtorque+additionalangleofrotation)de‐

pendingonthethreaddiameter:

M6:3Nm+90°

M8:8Nm+90°

M10:15Nm+90°M12×1,5:25Nm+90°

4.6ProcuringtheDUTs,referenceparts,andheadcountersurfaces

ThecompanyKeller&KalmbachGmbHhasalargeselectionofcertifiedtestspecimensandrefer‐enceparts,aswellasmatchingheadcountersurfaces,whichfulfillthedescribedspecifications.Ifthesepartsarenotused,thisfactmustbedocumentedinthetests.Intheeventofadispute,onlytestswiththesepartsarepermissible.

5Testprocedure(testsequenceforthethreadedjoint)

Thethreadedjointsmustbefastenedwithastationarybolttestbed(spindleormotordrive)and,ifpossible,thefasteningprogramsfromproductionorproblemthreadedjointsmustbeused.Iftheproductionparametersareunknownorifthetestingispartofbasicresearch,thefollowingstepsareapplicableasabasicrule:

–Ensureminimumturningangleof≥360°betweenscrewheadandcountersurface(necessaryforthespindledrivetoacceleratetothespecifiedspeed)

–Pre-tighteningofthethreadedjointwithanincreaseddrivespeed(standardtargetvalue:

200min-1,forthreadsizes>M10,themaximumvalueofthedrivespeed<200min-1isalsopossible)toatighteningtorqueofapprox.30%ofthefinaltorque

–Shortunloadingofthespindle(MA=0Nm)withstopofatleast0,2s(transitionsfromslidingtostatictoslidingfrictioncanleadtohighercoefficientsoffriction)

–Finaltighteningofthethreadedjointat20min-1totherespectivefinaltorque

–Oncathodicallyelectrocoatedperforatedstrips,4repeatedfasteningprocessesmustbecon‐ductedwithidenticalparameters.Onanaluminumperforatedstrip,thefasteningprocessmustberepeatedoncewithidenticalparameters.Beforeeachrepetition,afterashortrestperiod(atleast1s),looseningatthelowestpossiblespeed(max.60min-1)isnecessarytoavoidaddi‐

tionalheating.

Thestandardvaluesbasedon

VW01126-1

mustbeusedasthespecificationfortorquesoncath‐odicallyelectrocoatedperforatedstrips.Thetestsonthealuminumperforatedstripmustusethespecificationsfrom

VW01126-2

forthetighteningbeyondtheelasticlimitcorrespondingtothreadsizeandstrength/material.Besidesthecoefficientsoffriction,thecurveoftheachievedpreload

forcemustbeassessed.

Figure4

and

Figure5

showexamplesforanOKandanot-OKtorquecurveincludingpre-tighten‐

ingandfinaltightening.

Page10

VW01131-1:2012-02

Figure4–Torque/timecurveincludingpre-tighteningandfinaltightening(threadedjointOK)

Figure5–Torque/timecurveincludingpre-tighteningandfinaltightening(threadedjointnotOK,

stick-slipeffect)

Page11

VW01131-1:2012-02

6Evaluation

VW01129

specifieshowtoevaluatethetestresultsanddeterminethetolerancelimitsofthede‐terminedcoefficientsoffriction.Forcomputingµkandµtotal,theaveragefrictiondiameterDkmmustbedeterminedfromtheimpressionofthetwobearingsurfaces(countersurfaceandunderhead

bearingsurface)afterthefirstloosening.Theevaluationmustbeperformedatapreloadforcethatisequivalenttotheminimumpreloadforceachievedoverallrepetitionsduringthetests.

Withregardtothetestconditions,thedocumentationofresultsmustincludetheinformationasper

DINENISO16047

.Informationoncorrespondingreports(Volkswageninternalreportssuchas

fromtheLaboratoryInformationandManagementSystemLIMS)andtheorganizationalaffiliationofthetestersmaybehelpful.Furthermore,thefollowingstandardformatshavebeenestablishedforrepresentingthequantitiestobemeasuredinthetestreport:

Graphicrepresentationofthefollowingquantitiestobemeasured

x/ydiagramµk,µg,µtotalversusFVx/ydiagramMK,MG,MAversusFV

BarchartMinimum,average,andmaximumvalueofµk,µg,andµtotalofthefirstthrea‐dedjoint

Optionalrepresentations

BarchartMinimum,average,andmaximumvalueofµk,µg,andµtotalofrepeatedthreadedjoints

x/ydiagramµk,µg,µtotalversusangleofrotation

x/ydiagramMK,MG,MA,FVversusangleofrotation

Page12

VW01131-1:2012-02

7Applicabledocuments

ThefollowingdocumentscitedinthisStandardarenecessarytoitsapplication.

SomeoftheciteddocumentsaretranslationsfromtheGermanoriginal.ThetranslationsofGer‐

mantermsinsu