The-tyre-GRIP轮胎抓地力

GripGripSociétédeTechnologieMichelin23,rueBreschet,63000Clermont-Ferrand©SociétédeTechnologieMichelin,2001ProducedbyArtice/Japa-PhotographsfromMichelinpicturelibraryMadeinFranceReproduction,representation,adaptationortranslationofanypartofthisworkwithoutthepermissionofthecopyrightownerisunlawful.Requestsforpermissionorfurtherinformationshouldbeaddressedto:ManufactureFrançaisedesPneumatiquesMichelinServiceGroupeCommunication/TechniquePlacedesCarmesDéchaux,63040Clermont-FerrandCedex09FRANCEPage1Griponroadsurfaces4Introduction5Foreword:gripanditsdoubleparadox7IRubberandgrip8RUBBER:AVISCO-ELASTICMATERIAL8Whatisavisco-elasticmaterial?8Alittlemoreinformationon…thebehaviourofelasticmaterials9Alittlemoreinformationon…thebehaviourofviscousmaterials10Alittlemoreinformationon…thebehaviourofvisco-elasticmaterials11Wheredoesthevisco-elasticityoftyrerubbercomefrom?12Themodulusofrubber13INFLUENCEOFSTRESSFREQUENCYANDTEMPERATUREONTHEBEHAVIOUROFRUBBER13Influenceofstressfrequency14Influenceoftemperature15Frequency-temperatureequivalence16Alittlemoreinformationon…theWLFequation17THEMECHANISMSINVOLVEDINTHERUBBER-ROADINTERFACEFRICTION17Roadroughnesseffects18Molecularadhesion19Rubberandgrip:don’tforgetthebasics!21IIHowroadroughnessaffectsgrip22CHARACTERISATIONOFROADSURFACES23Measurementofmacroroughness23Measurementofmicroroughness24Conceptsregardingroadsurfaces25Measurementoftheloadbearingsurface26Characterisationofthefrictioncoefficientofarubber-roadinterface27INFLUENCEOFROADSURFACESONTHECOEFFICIENTOFFRICTION28Variationinfrictioncoefficientonadrysurface29Variationinfrictioncoefficientondamporwetroadsurfaces30Relativeimportanceoftherubberfactorandtheroadsurfacefactoringrip30Whataboutsnow?30Andwhataboutice?31Howroadroughnessaffectsgrip:don’tforgetthebasics!II.2II.1I.3I.2I.1ContentsPage233IIIGenerationofgripforcesinthecontactpatch34FRICTIONMECHANISMSOFARUBBERBLOCK34Shear(orpseudo-slippage)35Slippage36LONGITUDINALGRIPINBRAKING36Sourceofslippage37Alittlemoreinformationon...slippageandbraking38Longitudinalfrictionforce38Longitudinalfrictioncoefficientµ38Alittlemoreinformationon...thecoefficientoflongitudinalfriction39Thelongitudinalfrictionlawµ(G)40Generationofbrakingforcesinthecontactpatch40Alittlemoreinformationon...themaximumshearvalueofthetreadblockandthebeginningofslippage42Examplesofslippageandshearasafunctionofthecoefficientofgripandtheslippagerate42Alittlemoreinformationon...maximumlengthofshearandslippage43Analysisoftheµ(G)curve45Longitudinalgripinbraking:don’tforgetthebasics!46TRANSVERSALGRIPINCORNERING46Centrifugalforce46SlipangleIII.3III.2III.148Transversalfrictionforce48Coefficientoftransversalfrictionτ48Alittlemoreinformationon...thecoefficientoftransversalfriction49Effectofthebendradiusonthemaximumcorneringspeed49Alittlemoreinformationon...maximumcorneringspeed50LawoftransversalfrictionY(δ)50Alittlemoreinformationon...thetransversalgripcoefficient51Generationoftransversalforcesinthecontactpatch52AnalysisoftheY(δ)law52Alittlemoreinformationon...themaximumlengthofshearandslippage54Transversalgripincornering:don’tforgetthebasics!55SHARINGTHEGRIPPOTENTIALONTHEROAD55Combinedgrip55Apotentialtobeshared57ABS57Alittlemoreinformationon...howtheABSworks59IVGriponwetsurfaces61THEHYDRODYNAMICZONE:DISPERSALANDDRAINAGE61Alittlemoreinformationon...thespeedatwhichaquaplaningoccurs62Aroundedfootprinttoreducethepressureexertedbythebankofwateronthetyre62Alittlemoreinformationon...theroundedcontactpatchwhichincreasesaquaplaningspeedIV.1III.4Page3Contents63Widetyresandwaterdispersal64Angledtreadgroovestodrainawaywatertotheside65THEVISCODYNAMICZONE:STORINGWATERINTHETREADGROOVES65Compressionofthewaterbythetreadblocks65Alittlemoreinformationon...thetimeforwatertransfertothestoragezones67Sipesandgriponwetsurfaces69DAMPTODRYZONE:RESTORINGDRYCONTACT69Edgestobreakthroughthefilmofwater70Griponwetsurfaces:don’tforgetthebasics!71VGripandvehiclehandling72LOADTRANSFER72Longitudinalloadtransfer72Alittlemoreinformationon...howloadtransferaffectsbrakingefficiency73Lateralloadtransfer73Alittlemoreinformationon...howloadtransferaffectscornering74UNDERSTEERANDOVERSTEERV.2V.1IV.3IV.277VITestingtyregrip79ANALYTICALTESTS79Roadsimulators80Laboratoryvehicles81VEHICLETRACKTESTS82Testinglongitudinalgrip83Alittlemoreinformationon...calculatingthecoefficientofgripµ84Transversalgriptests87VIIGripandrollingresistance88Wheredoesrollingresistancecomefrom?88Maximisegripandminimiserollingresistance:achallengeinphysicalscience90Twodifferentfrequencyranges91IndexVI.2VI.1A,B,C…GriponroadsurfacesIftherewerenosuchthingasgrip,carsjustwouldnotbeabletomoveatall.Thewheelswouldspinandthedriverwouldnotbeabletobudgethevehicle.Evenonastraightroadandatsteadyspeed,thereisnoalternativetogrip.Thisisbecauseamovingvehiclehastodealwithnaturalforces,suchasthebanking,theslopeortheunevennessoftheroad,orrollingresistance,whichareconstantlytryingtoslowthevehicledownorpushitoffitspath.Howeveritisonlyduringcorneringorbrakingthatadriverorpassengeris