VW 01131-201803米制螺纹的钢制紧固件的摩擦系数的确定EN.pdf

GroupstandardUpdatedtranslation:2018-06VW01131

Issue2018-03

Class.No.:01712

Descriptors:coefficientoffriction,fieldtesting,testbolt,testnut,threadedconnection,tighteningtorque

DeterminationofCoefficientsofFriction

SteelMechanicalFastenerswithMetricISOThreads

Preface

Boltsandnutsareusuallytightenedinseveralstageswithafastpre-tighteningstageinorderto

shortenassemblytime.Thefinaltighteningoperationisusuallyperformedwithreducedrotational

speedandincreasinglyfrequentlyalsowithtorque-to-yieldtighteningprocedures.Withlargeran‐

glesofrotation,additionalfactorsthathaveanimpactonfrictiontakeeffect.Externalstandards

andregulationsdonotsufficientlytakethisfactintoaccount.

Thefriction-influencingfrictionpartnersoftheboltsandnutscanhaveverydiversesurfacetex‐

tures.Noteveryconceivablefrictionpairingcanbesimulatedinstandardizedtests.Verysmooth

andcohesivesurfacesorsurfacesthatareveryroughduetotheprocessingandmaterialstructure

presenttheirownchallenges.Moreover,surfacedamagecanoccuronfastenedpaintedparts

whichleadstoextremefrictionconditionsandoftenproducesundesiredeffects.Screwingboltsor

screwsintodeepthreadedholesmadeinsoftmaterialsplacesspecificdemandsonthecoating

systems.

Forinstance,wheelboltsaretightenedinseveralstagesduringinstallation(tightening,loosening,

andfinaltighteningstages).Multistagetighteningoperationsmustalsobetakenintoconsideration

whenitcomestorework.Contrarytostandardizedlaboratorytests,seriesproductionconditions

usuallygeneratehighercoefficientsoffrictionwithsometimessignificantlylargerdispersion.

Furthermore,fortheevaluat