超精密磨削加工技术外文翻译文献.docx

超精密磨削加工技术外文翻译文献.docx

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超精密磨削加工技术外文翻译文献

超精密磨削加工技术外文翻译文献

（文档含中英文对照即英文原文和中文翻译）

原文：

Precisioninternalgrindingwithametal-bondeddiamondgrindingwheel

JunQian,WeiLi,HitoshiOhmorib

NanjingUniversityofAeronauticsandAstronautics

Abstract

Ametal-bondedgrindingwheel,comparedwithconventionalgrindingwheels,offerstheadvantageofhighhardness,highholdingabilityandfinerusableabrasivegritmeshsizes.Thetruinganddressingofametal-bondeddiamond（MBD）wheel,inpractice,areverydifficult.Togrindsmall-diameterinternalcylindricalsurfacewithMBD-wheels,anintervalelectrolyticin-processdressing（ELID）methodwasutilized.Experimentswerecarriedoutonanordinarycylindricalgrindingmachinewithanattachedinternalgrindingset-up,andstraighttypegrindingwheelsofdifferentgritsizeswereused.Thegrindingwheelsweretrued,usingtheelectricaldischargemethod,andtheeffectsofelectrodeshapes,grindingparameters,andgritsizeswereevaluatedexperimentally.Mirrorsurfacegrindingofdifferentmaterialswascarriedoutwitha#4000CIB-Dwheel,incorporatedwiththisintervalELID（ELIDII）method.Theexperimentalresultsarereported#2000ElsevierScienceS.A.Allrightsreserved.

Keywords:

Cylindricalgrinding;Metal-bondedgrindingwheel;Dressing;Electrolyticin-processdressing；Precisiongrinding

1.Introduction

Alongwiththetechnologicaladvancementofultra-precisiongrinding,applicationsandrequirementsforprecisioncylindricalsurfaceshaveincreasedsignificantlyintherecentyears[1].Asaprincipalprocessingmethodforaninternalsurface,cylindricalgrindinghasbeencommonlyutilizedasafinaloperationintheproductionofprecisioncomponents.Sincegrindingisusuallythemostcostlyofallmanufacturingprocesses,considerableattemptshavebeenfocusedontheanalysisandoptimizationofthegrindingprocesstominimizemachiningtime[2-6],andonvariouscompensatorycontrolstrategiestoimproveworkpiecequality[7-10]inthecylindricalgrinding.However,fewresearchesonmirror-surfaceinternalgrindinghavebeenreported[5,6,11],probablyduetothelimitationofabrasivegritsizeapplicabletonon-metallicbondgrindingwheels[5,7,8,10].

Researchonhighefficiencygrindingofadvancedmaterials,byutilizinghigh-rigiditygrindingmachinesandtoughmetal-bondedsuperabrasivewheels,hasledtothesuccessfuldevelopmentofcastironbondeddiamond（CIB-D）grindingwheels[12].Thesewheelsaremanufacturedbymixingdiamondgrits,castironpowderorfiber,andasmallamountofcarbonylironpowder.Thewheelsarecompactedtoadesiredformunderhighpressureandthensinteredinanatmosphereofammonia.Thesewheelsarenotsuitableforcontinuousgrindingforalongperiodoftimeforthefollowingreasons:

（1）Astoughermetal-bondedwheelsexhibitpoordressingability,itisdifficulttoachieveefficientandstabledressingsimultaneously.

（2）Higherrateofmaterialremovalinthegrindingpromoteswearoftheabrasivegrains,therefore,morefrequentredressingofthegrindingwheelwillberequiredbystoppingthegrindingprocess.（3）Whilemachiningmetalssuchassteel,wheelloading（embeddingofswarf）occurs,makingeffectivedressingofmetallicbondwheeldifficultinpractice.Althoughadiamondslabincorporatedwithanabrasivejetsharpeningmethodisabletodressabronze-bondedwheeltothesametopographyasanelectroplatedwheel[12],complexequipmentmustbeaddedinevitablywhichcauseworking-environmentproblem.Dressingbyelectricaldischargeisagoodmethod,butitisdifficulttoconducton-linedressing,anddressingstripesappearonthewheelperipherywhenapairofparallelelectrodesisused[13,14].Electrolyticin-processdressing（ELID）hassofarservedasthemostsuccessfuldressingmethodformetal-bondedwheels.Ithasbeendevisedandappliedsuccessfullyinprecisionsurfacegrinding[15-17].However,itsapplicationtointernalgrindinghasnotbeenwellinvestigated;especiallywhentheinternaldiameteroftheworkpieceisjustslightlylargerthanthatofthegrindingwheel,itisverydifficultorevenimpossibletofixadressingelectrodemountedparalleltothewheelsurfaceasinordinaryELIDgrinding[15].AnovelmethodtocarryoutELIDgrindingofinternalcylindricalsurfacesonanordinarygrindingtoolispresentedinthispaper.Theprincipleandprocessofthismethod,namelyintervalELID（ELIDII）grinding,isalsodiscussed.ApplyingELIDIIgrindingtoanordinarygrindingmachine,somepreliminaryexperimentshavebeencarriedout.Twotypesofdressingelectrodeswereusedandtheirdressingeffectswereinvestigated.Withthistechnology,fourspecimensofaluminaceramic,hardenedsteelsSKH51andSKD11andbearingsteel,weregroundtomirrorfinish.Theresultsofthisresearcharepresentedinthefollowingsections.

2.PrincipleofintervalELIDgrinding

Theintervaldressingofanabrasivegrindingwheelitselfisnotanewtechnology.Infact,usingthecommonmechanicaldressingmethods,thewheelisusuallydressedatintervals.Thegrindingprocessisstoppedtodressthewheelaftergrindingoneworkpieceorseveralworkpieces.Thetoollifelimitcanbechattervibration,surfaceroughnessandburningmarks,etc.[2].However,withtheELIDIImethod,thewheelisdressedatintervalsandtheabrasivesremainprotruding,enablingthegrindingprocesstogoonwithoutanyinterruptionandconsequentlyrealizinghighefficiencygrinding.

TheintervalELIDsystemisessentiallycomposedofthefollowingelements:

（i）ametal-bondedgrindingwheel,（ii）anELIDpowersource,（iii）electrolyticcoolant,and（iv）apipedressingelectrode.Themostimportantfeatureofthisprocessisthatnospecialmachineisrequired,andinfacttheexperimentalsystemweusedisanauxiliaryinternalcylindricalgrindingattachmentonanexternalcylindricalgrinder.

ThefundamentalprincipleofintervalELIDgrindingissameasthatofordinaryELIDgrinding[15].Fig.1showsaschematicdiagramoftheintervalELIDgrindingsystem.Themetal-bondedgrindingwheel,whichiselectricallyconductive,isconnectedtothepositiveterminalofaDC-pulsepowersuppl

Fig.1.SchematicdiagramofintervalELIDgrinding.

-ywithasmoothbrushcontact,andafixedelectrodeismadenegative.Aproperclearanceofapproximately0.1mmisoriginallysetbetweenthepositivepole（wheel）andthenegativeone（dressingelectrode）.Byvirtueofelectrolysisbetweentwoelectrodes,thewheelandthedressingelectrode,thegrindingwheelisdressedandanon-conductivefilmisformedonthewheelperiphery.Thisoccursuponthesupplyofcurrentfromthepowersourceandtheelectricallyconductivecoolant.DuringtheintervalELIDgrindingprocess,theprotrudinggrainsgrindtheworkpieceandasaresult,thegrainsandtheoxidelayerweardown.Thewheel'selectricalconductivityincreases,duetothewearofthenon-conductiveoxidelayer.Thecurrentinthecircuitincreases,thusincreasingtheelectrolysis.Theabrasivegrainsthereforebecomemoreprotrudingandaninsulatinglayerisformed.

3.Experimentalprocedure

Usually,intervalELIDgrindingconsistsofthefollowingsteps.（i）Truing:

truingisrequiredtoreducetheinitialeccentricityofthewheel,especiallywhenanewwheelisusedforthefirsttime.Itisdifficulttoapplyconventionaltruingmethods,suchasbrakedresser,tometallicbondwheelsduetothehighbondstrength.Inthisinvestigation,thecastironbondedwheelwastruedbytheelectricaldischarge（ED）process.（ii）ELIDdressing,alsoknownaspre-dressingbyelectrolysis,presentlyperformedatamuchlowerwheelrotationspeedandhigherelectricsettings.（iii）Grinding:

intervalELIDgrinding.Theconditionsofelectrolysis,duringthelasttwosteps,differduetochangeinthewheelstateandgrindingconditions.

3.1.ED-truing

Totrueacastironbondeddiamondwheelathighspeedandwithhighprecision,anelectricaldischargetruing（ED-truing）methodwasusedinthisstudy.Fig.2showsthedetailsofthismethod.AspecialED-truingwheel,madeofhightemperaturealloyandinsulatedfromitscentralshaft,wasmount

Fig.2.ViewoftheED-truingset-up.

-edonthethree-jawchuckofthegrindingtool.TheED-truingwheelwasconnectedtothenegativepoleofanELIDpowersourceoriginatingfromordinaryEDpowersupply,whilstthegrindingwheelwaslinkedtothepositivepole.BoththeED-truingwheelandthegrindingwheel,especiallythelatter,rotatedatafairlylowspeedandtheEDtruingwheelreciprocatedalongwiththemachine'ssaddle.Littleandsometimesevennocoolantwassuppliedtotheworkingareatopreventelectrolysistothefullandtopursuehightruingprecision.

3.2.Pre-dressing

FollowingtheED-truing,pre-dressingwascarriedoutbeforestartingELIDgrinding（seeFig.1）.Whenthepre-dressingbegan,thesurfaceofthetruedwheelshowedagoodelectricalconductivity.Therefore,thecurrentwouldbeveryhighandthevoltagebetweenthewheelandelectrodewouldbelow,varyinginaccordancewiththewheelsizeanddressingsettings.Afterseveralminutes,thecastironfiberbondmaterial,whichismostlyionizedintoFe+2,isdissolvedbyelectrolysis.TheionizedFe+2willreactwithnonconductiveferroushydroxidesandoxidestoformalayeronthewheelperiphery.Thisinsulatingoxidelayerwouldgrowonthewheelsurface,wherebyitselectricalconductivitywouldbereduced.Consequently,thecurrentwoulddecreaseandtheworkingvoltagewouldremainquitehigh（90V,incasethattheoriginallysetopenvoltageis100V）after20min.Thecolorofthewheelchange

-dtodarkpink,duetotheformationofferrousoxide.

3.3.IntervalELIDg