机械毕业设计钢筋切断机外文翻译.docx

机械毕业设计钢筋切断机外文翻译.docx

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机械毕业设计钢筋切断机外文翻译

附录Ⅰ：

MagnetoelasticTorqueSensorUtilizingaThermalSprayedSense-ElementforAutomotiveTransmissionApplications

BrianD.Kilmartin

SiemensVDOAutomotiveCorporation

ABSTRACT

AMagnetoelasticbasedNon-Contacting,Non-CompliantTorqueSensorisbeingdevelopedbySiemensVDOforautomotivetransmissionapplications.Suchasensorwouldbenefittheautomotiveindustrybyprovidingthefeedbackneededforprecisecomputercontroloftransmissiongearshiftingunderawiderangeofroadconditionsandwouldalsofacilitatecross-platformusageofacommontransmissionunit.

SiemensVDOhasprototypedtransmissiontorquesensorsoperatingontheprincipleofInverse-magnetostriction,alsoreferredtoastheInverse-JouleEffectandtheVillariEffect.Magnetostriction,firstdocumentedinthemid1800’s,isastructuralpropertyofmatterthatdefinesamaterial’sdimensionalchangesasaresultofexposuretoamagneticfield.Magnetostrictioniscausedwhentheatomsthatconstituteamaterialreorientinordertoaligntheirmagneticmomentswithanexternalmagneticfield.Thiseffectisquantifiedforaspecificmaterialbyitssaturationmagnetostrictionconstant,whichisavaluethatdescribesamaterial’smaximumchangeinlengthperunitlength.

Inverse-magnetostriction,conversely,defineschangesinamaterial’smagneticpropertiesinresponsetoappliedmechanicalforces.Materialthatishighlymagnetostrictiveandelasticinnatureisreferredtoasbeingmagnetoelastic.ThepremiseoftheSiemensVDOtorquesensordesignisthatamagnetoelasticmaterialcanbebondedtoacylindricalshaftandmagnetizedinitsmechanicalquiescentstatetocreateasense-element.Whileundertorque,principletensileandcompressivestressvectorsintheformofcounter-spiraling,mutuallyorthogonalhelicesdevelopintheshaftandareconveyedtothemagnetoelasticsense-elementgivingrisetoameasurablemagneticfieldchange.Themagneticfielddeviationthatarisesfromthemagnetoelasticsense-elementisdirectlyproportionaltothemagnitudeoftheimposedtorque.Ineffect,themagneticfieldismodulatedbytorque.Asensitivemagnetometerthentranslatesthefieldstrengthintoananalogvoltagesignal,therebycompletingthetorque-to-voltagetransducerfunction.

CriticaltothesuccessoftheSiemensVDOtorquesensordesignisanintimateattachmentofthesense-elementtothetorque-bearingmember.Inconsistenciesintheboundarybetweenthesense-elementandthetorque-bearingmemberwillresultinaberrantcouplingofstressesintothesense-elementmanifestinginperformancedegradation.Boundaryinconsistenciescanincludesuchimperfectionsasvoids,contaminates,lateralshearing,andlocalizedzonesofstresspre-load.Suchinhomogeneitiesmaybeinherenttoanattachmentmethoditselformaysubsequentlybecausedbysystemicallyrenderedmalformations.

Thermalspray,theprocesswheremetalparticlesaredepositedontoasubstratetoformacoating,wasusedtoaddresstheissueofsecurelyaffixingmagneticmaterialtoatorque-bearingmember.Inadditiontoachievingtheprerequisiteofanintimateandsecurebond,thethermalsprayprocesscanberegulatedsuchthatthedepositedmagneticmaterialispre-loadedwiththeinternalstressesneededtoinvoketheinverse-magnetostrictioneffect.

Summarizing,thepassivenatureofthemagneticsense-elementprovidesanintrinsicallysimplekernelfortheSiemensVDOtorquesensorthatmakesforahighlyreliableandstabledesign.Thethermalsprayprocessaddsrobustnesstothemechanicalaspectbypermittingtorqueexcursionstoanunprecedented±2000%offullscale（perprototypevalidationtestingofcertainconstructs）withouttheneedforancillarytorquelimitingprotectiondevices.Furthermore,accuracy,repeatability,stability,lowhysteresis,rotationalpositionindifference,lowcostandamenabilitytothehigh-volumemanufacturingneedsoftheautomotivemarketplaceareallattributesofthistorquesensingtechnique.Whencoupledwithamagnetometerthatisgroundedinwell-establishedfluxgatetechnology,theresultantsensorisinherentlydependableandcanpotentiallyestablishanewstandardfortorquemeasuringsensors.

INTRODUCTION

Asiswellknown,automotivetransmissionsaredesignedtoalterthepowertransferratiobetweentheengineandthedrivewheelseffectivelyoptimizingengineloading.Theenginetherebyrunsinanarrowandefficientoperatingbandeventhoughthevehicletravelsoverawiderangeofspeeds.Forautomatictransmissions,shiftvalvesselectthegearratiobasedgenerallyonthethrottleposition,enginevacuumandtheoutputshaftgovernorvalvestate.Withtheadventofelectronicsensorsandcomputerizedenginecontrollers,transmissionshiftfunctionshavebeenmigratingtowardsclosed-loopoperationundersoftwareprocessingcontrol.Alongwiththisprogressioncametherealizationthatthetransmissionoutputtorquewouldprovideavaluablefeedbackparameterforshiftandtractioncontrolalgorithms.Themeasurementofoutputtorque,however,provedelusiveduetotheextremelyharshoperatingconditions.OneparticularSUVapplicationunderconsiderationrequired1%accuracyinmeasurementsofroughly2700Nmwithpossibletorqueexcursionof4700Nm;allwhileexposedtotemperatureextremes-45to+160oC.

Onemethodformeasuringtorqueistoexaminethephysicalstressesthatdevelopinashaftwhenitissubjectedtoanend-to-endtwistingforce.Theprinciplestressesarecompressiveandtensileinnatureanddevelopalongthetwocounter-spiraling,mutuallyorthogonal45ohelices.Theyaredefinedbytheequation:

t=Tr/J

WhereTisthetorqueappliedtotheshaft,ristheshaftradiusandJisthepolarmomentofinertia.

Settingpr4/2=Jforasolidcylindricalshaftandr=d/2yields:

t=16T/pd

Onceagain,Tisthetorqueappliedtotheshaftanddistheshaftdiameter.

Furthermore,thedegreeoftwistexperiencedbytheshaftforagiventorqueisgivenby2:

q=32（LT）/（pd4G）

WhereListhelengthoftheshaft,Tistheappliedtoque,disthediameteroftheshaftandGisthemodulusofrigidityoftheshaft.Themodulusofrigiditydefinesthelevelofelasticityoftheshaftmaterial,thus,alowerGvaluewouldmanifestinashaftwithahigherdegreeoftwistforanygivenappliedtorque.

Torqueinducedstressesthatoccurintheshaftmaterialaretransferredintoanaffixedmagneticcoatingandgiverisetomeasurablechangesinitssurroundingmagneticfieldthataredirectlyproportionaltothemagnitudeoftheappliedtorque;withthepolarityofthemagneticfield,i.e.,northorsouth,governedbythedirectionoftheappliedtorque.Inessence,thisisthepremiseoftorquesensingbymeansofinversemagnetostriction.

TORQUESENSOREMBODIMENT

Toeffectivelyinvoketheinverse-magnetostrictioneffect,themagneticmaterialmustbecorrectlypre-loadedwithstressanisotropyinitsquiescentstate.Inthecaseofacylindricallyshapedmagneticelement,theanisotropicforcesmustbecircumferential（i.e.,tangential）innatureandcanbeeithercompressiveortensile–dependingonthepolarityorsignofthematerial’ssaturationmagnetostrictionconstant.Achievingahomogenouspre-loadthroughoutthemagneticmaterialiscrucialifthesensoristoaccuratelyinterprettorqueregardlessofitsrotationalpositionwithinastationarymagnetometer.

POSITIVEMAGNETOELASTICDEVICES

Earliereffortstocreatesuchatorquesensingelementreliedonasenseelementmadeofmaterialwithapositivesaturationmagnetostrictionconstant.Thisembodimentwasrealizedwitharing-shapedmagnetoelasticelementmadefrom18%nickel-ironalloythatintrinsicallyrequirestensilecircumferentialpre-loading3.Suchapre-loadwasachievedbypressingtheringontoataperedareaofthebaseshaft–effectivelystretchingit.TheeffectoftensilestressonthemagnetichysteresisbehaviorisshowninFigure1wheretheremnantinductance,Br,nearlytriples.The“easy-axes”ofthemagneticdomainsaligncircumferentiallyduetotheanisotropydefinedbytheprincipaltensilestressvector.Whenmagneticallybiased,thesystemineffectoperatesasacircumferentiallyshortedmagnetwithBapproachingBrandHapproachingzero.

NEGATIVEMAGNETOELASTICDEVICES

Toadvancethestateoftheart,SiemensVDOAutomotivehasoptedforamagnetoelasticelementwithanegativesaturationmagnetostrictionconstant.Inthiscase,thealloyisveryhighinnickelcontentexhibitingasaturationmagnetostriction,ls,intherangeof-3e-5dl/landrequiresthestresspre-loadtobetangentiallycompressiveinnature.Toachievethisembodiment,themagnetoelasticmaterialthatconstitutesthesenseelementis“deposited”ontothebaseshaftusingahigh-velocity-oxygen-fuel（HVOF）thermalsprayprocess.Thecoatingthicknessisonly0.5mmwithanaxiallengthof25mm.Thesenseelementmaterialisendowedwithcompressivestressbymeansofprecisecontrolofthethermalsprayprocessparameters.Thisproprietaryproceduretransformsadepositionprocessthatnormallyconfersisotropicmaterialpropertiesintoonethatrenderstherequisitestressanisotropy.

PrototypeFabrication

MagnetoelasticElement

Thespecificationfortheshaftrequiresthemeasurementoftorquelevelsof2700Nmwithnodeleteriouseffectsfollowingexposuresofupto4700Nm.Operatingtemperatureis-45oCto160oC.

Byconvertingfromtheearliertorquesensor“pressed-onring”concepttoonebasedonamagnetoelasticmaterialwithanegativesaturationmagnetostrictionconstant,ls,thedesignisadvancedinseveralrespects.Primarily,itsresiliencyagainststress/corrosioncrackingisenhancedby1）