科技英语论文范文.docx

科技英语论文范文.docx

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科技英语论文范文

科技英语论文范文

ON-LINEDIAGNOSISOFMARINEDIESELCRANKSHAFTCRACK

BASEDONMAGNETICMEMORY

LIHAN-LIN,LINJIN-BIAO,CAIZHEN-XIONG,LUYONG

（MarineEngineeringInstitute,JimeiUniversity,Xiamen,Fujian361021）

Abstract:

Thispapersummarizedrecentdiagnosismethodsofmarinedieselcrankshaftcrackandintroducedthefundamental

principle,developmentandapplicationofmetalmagneticmemorytesting（MMMT）diagnosistechnology.Comparedwithother

methods,aschemedevelopedfromMMMTcombinedwithtorsionalsignaltomakeon-linediagnosisofcrankshaftcrackwas

proposed,andtheon-linediagnosisexperimentalplatformofdieselwasdesigned.Finally,commentswerealsomadeonthe

on-lineMMMTmethod.

Keywords:

marinediesel;crankshaft;crack;metalmagneticmemory

1Introduction

Mostofthecrankshaftcracksonoceanmarinedieselaredeeplylatentanddifficulttodetectartificially.In1general,whilethecrackdevelopstoacertainextentitwillruptureandcausedestructivebreakage.Ifinchoate

stressconcentrationandtinycrackofcrankshaftaredetectedon-linebyNon-DestructiveTesting（NDT）methods,thedieselcanbestoppedbeforethefulldevelopmentofthecrackandthusrupturecanbeavoided.AnewNDTmethod,MMMTdevelopedrapidlyrecentyearswithadvantagesinsuchareasascheapandsimplesensors,measuringwithoutimpactingdieseloperationandlong-termon-linedetection.Therefore,therewillbeagreatforegroundtouseMMMTincrankshaftcrackdetection.

2DynamicDiagnosisofCrankshaftCrack

2.1StaticDiagnosisofCrankshaftCrack

Crankshaftcrackisoneofthefatalfaultsindiesels.TherearesomestaticNDTmethodstodiagnosecrankshaft2cracksuchasUltrasonicTesting,RadiographicTesting,MagneticParticleTesting,PenetrateTesting,EddyCurrentTesting,OpticalHolography,andMicrowaveTesting.Thesemethodshavetakenanimportantpartin

crankshaftqualitycontrolandaccidentprevention.However,ontheotherhandthereareseveraldisadvantagesofthesemethods.Firstly,allofthemmustfindcracksalreadyformedandcannotdetectunexpectedones.Secondly,theyareunabletomakeon-linedetectionandfaultdiagnosis.Thirdly,mostofthemneedsurfacepretreatmentofthefacilitiesbeforeinspection.Finally,theaccuracyofdetectionisaffectedbycrankshaftconfigurationandpersonalskill.

2.2DynamicDiagnosisofCrankshaftCrack

Atpresenttherearesomemethodstodiagnoseshaftcrackson-line:

rotorenginevibrationdisplacementmethod,trainwheelshafttemperaturetesting,acousticemissionandtortionalvibrationsignaltesting.However,vibrationdisplacementmethodisunfitfordieselcrankshaftcrackdiagnosisduetothestrongvibrationfromreciprocatingmovementwhichmakesitdifficulttosurveydisplacementandacceleration.Althoughthereislocalhightemperatureonthecracks,itishardtoinspectthechangeofthecrankshafttemperatureduetothehightemperatureofthelubeoilinthediesels.Acousticemissionmethodisstillindevelopingasgreatnoisefromdieseloperationmakesitdifficulttomeasurehighfrequencyacousticwaveemittedbycrack.Thereforeatpresentitisfeasibletodiagnosecrankshaftcrackon-linebyusingtorsionalvibrationsignal.

ThisresearchissupportedbyNatureScienceFundingProjectofFujianProvinceA0410022.

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2.3CrankshaftCrackDiagnosisUsingTorsionalVibrationSignalLiterature3broughtforwardamethodusingtorsionalvibrationsignaldetectedreal-timefromdieseltodiagnose

crankshaftfault.Itstudiedcrackfaultdiagnosisthoughmeasuringthecharacteristicsofthetorsionalvibrationof

theshaftingflywheelsystem,andpresentedthatmodelfrequencyanddampweresensitiveparametersofcracks.

Thetorsionalvibrationmeasuringsystemofthedieselhadseveraladvantagessuchas:

easymeasuring,nodirect

contact,cheapsensorandlongevity.Itwasalong-termreliablealarmmethodfordieselshaftingcrack.Research

groupinMarineEngineInstituteofJimeiUniversityhasdonetheresearchofinternal-combustionenginescore4faultwithintelligenttorsionalvibrationdiagnosissystem,anditwasasuccessfulcaseofon-linefaultdiagnosisbasedontorsionalvibrationsignal.

3MetalMagneticMemoryTestingTechnique

Intheyear1997,RussianprofessorA.A.Dubovbroughtforwardcorrelativetheoryofmetalmagneticmemory5ontheWorldConferenceonNDT,developedMMMinstrumentsandformedMMMNDTtechnique.

3.1TheoryofMetalMagneticMemoryTesting

Undertheconditionoftheexistenceoftheoutsidemagneticfield,usuallythemagneticfieldoftheearth,therewillappearaphenomenoninthestressconcentrationzoneofferromagneticcomponentswithloadthatpermeabilityofmaterialbesidesthezonereducesandsurfaceleakmagneticfieldincreases,whichiscalledmagnetostriction.Itwillmakesthesurfacemagneticfieldoftheferromagneticaccessoryincrease,andthemagneticfieldcanrememberthelocationofdisfigurementandstressconcentrationzone,thusitisnamedmetalmagneticmemory.Atpresent,oneofthemostpopularexplanationtothemagneticmemoryisthat,loadedbyalternatingstresses,unsymmetricalelasto-plasticstrainwilltakeplaceinthemagneticdomainformedby

Fig.1TSC-1MStressConcentrationspontaneousmagnetizationinferromagneticmaterial,andthenunequal6MagneticTestingInstrumentmagneticfluxdensitywillbeinducedbytensileandcompressivestress.

Withinthemagneticfieldoftheearth,disfigurementand

stressconcentrationzoneofferromagneticcomponentswill

producemaximumleakmagneticfield,andtherewillbeXmaximumtangentialcomponentHofthemagneticfieldpYintensityandzeronormalcomponentH.p

3.2MetalMagneticMemoryTestingInstrumentsandTheir

PracticalUse

Researchonmagneticmemorytestinginstrumentsinforeignisinpacewiththetechnologicaldevelopment.ForemostofallwereTSC-1M（seeFig.1）,TSCM-2FMandTSC-IM-4Fig.2MM-SystemDataProcessionSoftware

stressconcentrationmagnetictestinginstrumentdevelopedbyEnergodiagnostikaLtd.ofRussia.Theseinstrumentswereassociatedwithdifferenttypesofsensorforvarious

requirements.SoftwareoftheseinstrumentsforsignalanalysisanddataprocessingwasalsodevelopedinRussia.Forexample,MM-Systemdataprocessingsoftwareproducedby

EnergodiagnostikaLtd.wasabletoanalyzeMMMsignalanddisplaythesignalinthreemodels:

2-D,3-DandpolarFig.3EMS-2000MMMDiagnosisInstrumentcoordinatesmodel（seeFig.2）.

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InternalMMMtestinginstrumentsweremainlydevelopedby

Eddysun（Xiamen）ElectronicCO.,LTD.Intheyear2000,

EMS-2000metalmagneticmemorydiagnosisinstrument（seeFig.

3）withdifferenttypesofsensorwasproducedbythecompany

forferromagneticcomponentsdisfigurementdiagnosis.Atthe

sametime,M3DPS（seeFig.4）softwareforsignalanalysisand7dataprocessingwasdevelopedtolocateearlyfatiguedamage.

ApplicationsofMMMtestinginChinahasdevelopedrapidly

focusingoncracktestingofsteelweldingline,pressurevessel,Fig.4M3DPSSoftware3-DDisplayaeronauticalstructure,thermalpowerplantandsoon.Firstly,in

thefieldofsteelmaterialweldtesting,itwasmainlyusedfor8dissimilarsteelwelding,hullstructuresteelplatewelding,earlydiagnosisofweldingdisfigurement,

weldinglinequalityexamination,powerplantEHoilpipefilletweldingjoint,highpressureboilerpipeseatfilletweldingjointandsoon.Secondly,itwasappliedinpressurevesseltestingforhighpressurebottle,vesselweldingresidualstressmeasurementandsoon.Thirdly,itwasappliedinaeronauticalstructuretestingforearlierdisfigurementandplaneundercarriageinspection.Fourthly,itwasappliedinthermalpowerplanttestingforsteamturbinescomponent,bladescrack,throttlevalveandreheattubecrackdiagnosis.

4On-lineDiagnosisofCrankshaftCrackUsingMetalMagneticMemoryTesting

4.1CrankshaftCrackMetalMagneticMemoryTesting

Marinedieselenginecrankshaftsaremainlymadeupfrom

ferromagneticmaterial.AccordingtoMMMtheory,stressDieselBodyconcentrationzoneoncrankshaftwillproducemaximumXtangentialcomponentHofthemagneticfieldintensityandpYzeronormalcomponentHwithalternationofsymbol.Withp

scanninginspectionofthesurfacemagneticfieldofcrankshaft

byMMMtestingsensorandinstrument,thestress

concentrationzonewillbefoundoutaccordingtothezeroSensornormalcomponentofthefieldintensity,andthenthe

existenceofcrackonthecrankshaftcanbeestimatedInstrumentindirectly.Withthismethod,thelocationofcrackscanbe

foundoutwithoutinterruptingnormaloperationofthediesel,

andgiveanalarmintimetoremindengineersofoperation

conditionofthediesel.

Inthedesign,thesensoroftheinstrumentwillbeplacedFig.5DieselCrankshaftTestingDesign

intothebodyofthedieselthroughtheguidedoorofthediesel,anditcandirectlyscanzoneswiththemostprobableexistenceofstressconcentration,suchaslocationsnearoilboreandfillet.Incasethenormalcomponentofmagneticfieldintensityofthelocationshowsachangefrompositivetonegativeorfromnegativetopositive,itmeansthattheremaybetinycrackorstressconcentrationtakingplace,andatthesametime,theinstrumentwillrecordinalogandgiveanalarm.Themethodissimple,effectiveandfeasibletoon-linetestingonoperatingdieselonships.4.2DesignforCrankshaftCrackTestingSimulationExperiment

InordertoputMMMcrankshaftcracktestingmethodintopracticalapplicationtoships,simulationexperimentshouldbedone,andthemodelexperimentplatformis