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1、ON-LINEDIAGNOSISOFMARINEDIESELCRANKSHAFTCRACKBASEDONMAGNETICMEMORY*ThisresearchissupportedbyNatureScienceFundingProjectofFujianProvinceA0410022.LIHAN-LIN,LINJIN-BIAO,CAIZHEN-XIONG,LUYONG(MarineEngineeringInstitute,JimeiUniversity,Xiamen,Fujian361021)
2、Abstract:Thispapersummarizedrecentdiagnosismethodsofmarinedieselcrankshaftcrackandintroducedthefundamentalprinciple,developmentandapplicationofmetalmagneticmemorytesting(MMMT)diagnosistechnology.Comparedwithothermethods,aschemedevelopedfromMMMTcombin
3、edwithtorsionalsignaltomakeon-linediagnosisofcrankshaftcrackwasproposed,andtheon-linediagnosisexperimentalplatformofdieselwasdesigned.Finally,commentswerealsomadeontheon-lineMMMTmethod.Keywords:marinediesel;crankshaft;crack;metalmagneticmemory1Introd
4、uctionMostofthecrankshaftcracksonoceanmarinedieselaredeeplylatentanddifficulttodetectartificially.Ingeneral,whilethecrackdevelopstoacertainextentitwillruptureandcausedestructivebreakage1.Ifinchoatestressconcentrationandtinycrackofcrankshaftaredetecte
5、don-linebyNon-DestructiveTesting(NDT)methods,thedieselcanbestoppedbeforethefulldevelopmentofthecrackandthusrupturecanbeavoided.AnewNDTmethod,MMMTdevelopedrapidlyrecentyearswithadvantagesinsuchareasascheapandsimplesensors,measuringwithoutimpactingdies
6、eloperationandlong-termon-linedetection.Therefore,therewillbeagreatforegroundtouseMMMTincrankshaftcrackdetection.2DynamicDiagnosisofCrankshaftCrack2.1StaticDiagnosisofCrankshaftCrackCrankshaftcrackisoneofthefatalfaultsindiesels.TherearesomestaticNDTm
7、ethodstodiagnosecrankshaftcrack2suchasUltrasonicTesting,RadiographicTesting,MagneticParticleTesting,PenetrateTesting,EddyCurrentTesting,OpticalHolography,andMicrowaveTesting.Thesemethodshavetakenanimportantpartincrankshaftqualitycontrolandaccidentpre
8、vention.However,ontheotherhandthereareseveraldisadvantagesofthesemethods.Firstly,allofthemmustfindcracksalreadyformedandcannotdetectunexpectedones.Secondly,theyareunabletomakeon-linedetectionandfaultdiagnosis.Thirdly,mostofthemneedsurfacepretreatment
