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外文翻译--影响机械设计暂停动态加载过程.doc

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外文翻译--影响机械设计暂停动态加载过程.doc

1M.SukD.GillisEffectofmechanicaldesignofthesuspensionondynamicloadingprocessReceived2July2003/Accepted24February2004/Publishedonline3August2005_SpringerVerlag2005AbstractIndesigningaload/unloadsystemutilizedinharddiskdrives,necessarycareneedstobetakentoensurethatthesliderdoesnotdamagethedisksurfaceduringloadingandunloadingprocesses.However,asmalldeviationinthedesignpointofthepreloadbetweentheloaddomeandflexurecanleadtoundesirableloadingprocessesresultinginanadversenumberofslider/diskcontacts.Inthisstudy,weshowthatifthepreloadbetweentheloaddomeandflexureistoolow,theslidercanoscillatecausingthecornersoftheslidertocontactthediskmultipletimeseventhoughthesliderisafewmicronsawayfromthedisk.Inaddition,theslidercanbesuckeddowntowardsthediskresultinginacompleteseparationoftheloaddomefromtheflexureassemblyleadingtouncontrolledloadingconditions.Thisseparationoccurswhilethesuspensionisstillontheramp,andthusnopreloadisexertedonthesliderimmediatelyfollowingtheseparation.Consequently,thesliderfliesataflyingheighthigherthanthedesignpointuntilthegapbetweentheloaddomeandflexurecloses.Hence,thesuspensionmustbecarefullydesignedtosuppressslideroscillationandtoensurethattheloaddomedoesnotseparateduringtheloadingprocess.1IntroductionOneoftherequirementsindesigningaload/unloadsystemutilizedinharddiskdrivesisensuringthatthesliderdoesnotdamagethedisksurfaceduringloadingandunloadingprocesses.Sinceitisdifficulttoavoidslider/diskcontactsinentirety,however,thesystemisdesignedtominimizethenumberofslider/diskcontacteventsandtolessentheconsequenceswhencontactsdooccur.Thelikelihoodofslider/diskcontactsdependsontheloadingspeed,diskspeed,staticattitudeoftheslider,airbearingroughness,slidergeometry,etc.Forexample,sliderswithalargeradiusofcurvatureatitscornerscaneliminatediskdamagebyreducingthecontactstressbetweentheslideranddisksurfaceSukandGillis1998.Manyrecentstudieshaveconsideredtheeffectofsuspension,limiter,andairbearingdesignsontherobustnessoftheloadingandunloadingprocessesB2ogyandZeng2000Huaetal.2001LiuandZhu2001ZengandBogy2000.However,mostofthesestudieshaveprimarilyfocusedontheunloadingprocesssincethispartofthesequenceusuallyrevealsinterestingdynamicprocessesduetotheeffectsofnegativepressureairbearingdesigns.Thenegativepressureregionoftheairbearingresiststheunloadingactionresultinginstorageofpotentialenergyintheflexureandsuspensionassembly.Whenthesliderisfinallypulledawayfromthediskandthepotentialenergyisreleased,theslidercanoscillateviolentlyFig.1.Ontheotherhand,forareasonablywelldesignedsystem,theloadingprocessdoesnotexhibitsuchabehavior.Hence,mosthaveprimarilyinvestigatedtheunloadingprocessgivingonlacursoryattentiontothemorecriticalloadingprocess.Mostdesignersofload/unloadsystemswillfindthattheloadingprocesscanbemoretroublesomecomparedtotheunloadingprocess.Besidespotentiallycausingdamagetothedisk,otherproblemscanbeencounteredduringtheloadingprocess.Forexample,insomeinstances,theslidermayneverloadtothedesignedflyingheight,butrather,loadatflyingheightsontheorderof1lmSuketal.2004.Inthispaper,weshowhowasmalldeviationinthemechanicaldesignoftheflexure/suspensionassemblycanincreasetheprobabilityofslider/diskcontactsthatcanleadtoasignificantnumberofdiskcontactsinonesingleloadcycle.Specifically,weshowthatasuspensionsystemwithlowpreloadbetweentheflexureandloaddomecanleadtoloadingoftheslideratanuncontrolledstaticattitudeandvelocity.Theproblemsassociatedwiththisparticularaspectofdesigncanbeeasilyidentifiedbymeasuringthefullbodycapacitanceduringtheloadingprocess.2DescriptionofexperimentThesliderloadingdynamicswasinvestigatedusingalaserDopplervibrometerLDV,62kHzframeratehighspeedcamera,andfullbodycapacitance.Theexperimentalsetupconsistsofastandardload/unloadtester.Thecapacitancemetermeasuresthefullbodycapacitancebetweentheslideranddiskwhilethesliderisloadingontothedisk,similartotheoneusedinSuketal.2004.Thesliderwasloadedontoan3dunloadedfromthediskusingamovingrampwhilekeepingtheslider/suspensionassemblyfixedovertheODregionofthedisk.TheverticalmotionofthetrailingedgeofthesliderwasmeasuredusinganLDV.Alltestswerecarriedoutusingan84mmglassdiskandanegativepressurebobsledtypesliderwiththediskrotatingat10krpm.ThepitchstaticattitudePSAoftheslidersusedintheexperimentwasbetween1and2_.Toshowtheeffectoflackofpreloadbetweentheflexureandloaddome,wechosetwosuspensionassembliesthatareessentiallyidenticalwiththeexceptionofthepreload.Sincethedifferenceinthemagnitudeofthepreloadisdifficulttomeasure,onlytheexistenceofsubstantialdifferenceisverified.Todothis,wemounttheheadsuspensionassemblywithnormalpreloadNPHSAontotheramp.Asmallweight,thatissufficienttocauseloaddomeseparationfromtheflexure,isthenattachedtotheflexure.TheamountofseparationismeasuredwithaproperlypositionedCCDcamera.SimilarmeasurementismadeforaheadsuspensionassemblywithlowpreloadLPHSA.Figures2and3showopticalimagesoftheloaddomeandflexuretakenunderthesameconditionsforbothNPHSAandLPHSA,respectively.AgreaterloaddomeseparationfromtheflexureisobservedforLPHSAthantheNPHSA,confirmingthatLPHSAhaslowerpreloadthanNPHSA.3ResultsanddiscussionnegativepressureslidersT4hesliderloadsontothediskandthenfollowstherunoutofthediskasexpected.ThebottomplotinFig.3isthecorrespondingfullbodycapacitancemeasurement,whichshowsasinglejumpinthecapacitanceatthemomentthesliderloadsontothedisk.AsimilarmeasurementforLPHSAisshowninFig.5.Inthiscase,theslideroscillatesbeforeloadingontothediskunlikethecasewithahigherpreloadbetweentheloaddomeandflexure.Furthermore,theslidersverticalloadingvelocitysuddenlyincreaseswhenthesliderisabout50lmawayfromthedisk.Associatedwiththissuddenincreaseinthevelocity,thecapacitancemeasurementrevealsmultiplesharptransitions.Followingthetransitions,thecapacitancedoesnotreachthemaximumvalueforanother1msorso.Theseobservationsindicateaproblem,butitisdifficulttoascertaintheprecisedynamicsduetothelowmeasurementbandwidth.HigherresolutionmeasurementrevealsthattheslidercontactsthediskmultipletimesFig.6notethatthisexactbehaviordoesnotoccurforeverysuspensionassembly,butvariesfromonesuspensiontoanother.Figure6showssimultaneousmeasurementoffullbodycapacitanceandLDVduringloadingforLPHASimmediatelybeforefullyloadingontothedisksurface.Capacitancemeasurementshowssomeoscillationabout2msbeforeasteplikejumpisobserved.Notethattheaverageheightofthesliderduringtheseoscillationsisontheorderofafewmicrons.Atthisheight,thesuspensionpreloadnotthepreloadbetweentheflexureandloaddomeisstillsupportedbytheramp.TheLDVmeasurementshowsthattheslideractuallycontactsthediskandbouncesonandoffthediskoscillatingatthesamefrequencyasthatofthemeasurementmadewiththecapacitancemeter.Thesliderthensettlesintowhatappearstobealoadedposition,butthecapacitancemeasurementshowsthatthesliderhasnotfullyreachedthenominalflyingheightpositionthecapacitancemeasurementisslightlylowerinmagnitudethanthefinalvalue.Ittakesanother4msorsobeforethesliderfinallyloadsfullyintothenominalflyingheight.Surprisingly,LDVisalsoabletomeasurethislatterprocessaswell.Thecorrespondingarmmountedacousticemissionmeasurementshowsslider/diskcontactFig.4TopLDVmeasurementoftheloadingmotionofthetrailingedgeofthesliderforasystemwithnormalpreloadbetweentheloaddomeandflexure.BottomFullbodycapacitancemeasurement,whichshowsasinglesharptransitionasthesliderloadsontothediskverifyingtheLDVandcapacitancemeasurementsofslider–diskcontactFig.7.Thesligh

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