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1、TribologyLettersVol.10,No.1-2,200123Amoleculardynamicsstudyofscaleeffectsonthefrictionofsingle-asperitycontactsL.C.Zhanga,K.L.JohnsonbandW.C.D.CheongaaDepartmentofMechanicalandMechatronicEngineering,TheUniversityofSydney,NSW2006,Australiab1NewSquare,Cam
2、bridgeCB11EY,UKTheapparentscaleeffectonfrictionofsingle-asperityslidingwasinvestigatedwiththeaidofamoleculardynamicsanalysis.Thespecimenmaterialusedwasmono-crystallinecopper,whiletheasperitymaterialswerediamondandcopper,respectively.Itwasfoundthatafrict
3、iontransitiondoesexistbutdependsoninterfaceconditionsbetweentheasperityandspecimen.KEYWORDS:frictiontransition;scaleeffect;moleculardynamics;singleasperity1.Introductionanismsofslidingissolelyduetothedifferentcontactsize.Themoleculardynamicsmodelsconsis
4、tofasinglecylindri-Amicro-mechanicaldislocationmodeloffrictionalslipcalasperity(rigiddiamondandcopper)ofvariousradii,slid-betweentwoasperitieswaspresentedbyHurtadoandingacrossthefaceofacopperworkpieceonits(111)planeKim[1],whichpredictsthatthefrictionstr
5、essisconstantwithaspeedof5m/s.Theindentationdepth,d,was0.46nmandoftheorderofthetheoreticalshearstrength,whentheand−0.14nm(0.14nmabovetheworkpiece),respectively,contactsizeissmall.However,atacriticalcontactsizetherewheredisthedistancebetweenthesurfacesof
6、theasper-isatransitionbeyondwhichthefrictionalstressdecreasesityandspecimendefinedbytheenvelopesatthetheoreticalwithincreasingcontactsize,untilitreachesasecondtran-radiioftheirsurfaceatoms[2–4].Asusual[2–4],twolay-sitionwherethefrictionstressgraduallybec
7、omesindepen-ersofthermostatatomsarearrangedaroundtheNewtoniandentofthecontactsize.Hence,themechanismsofsliparecopperatomsofthespecimentoensurethattheheatgen-size-dependent,orinotherwords,thereexistsascaleeffect.eratedduringslidingcanconductoutofthecontr
8、olvolumeBeforethefirsttransition,theconstantfrictionisassociatedproperly.Theboundaryatomsarefixedtothespacetoelim-withconcurrentslipoftheatomswithouttheaidofdislo-inatetherigidbodymotionofthecopperspecimen.Thecationmotion.Thefirsttr
