Variation regularity of metal magnetic memory signals with inspecting time-interval and location

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1、万方数据J．Cent．SouthUniv．Techn01．(2007)03—0319-05DoI：10．1007／sll771—007—0063—7Variationregularityofmetalmagneticmemorysignalswithinspectingtime—intervalandlocationYANChun—yan(严春妍)1，LIWu．shen(李午申)1，DIxin-jie(邸新杰)1，XUEZhen．kui(薛振奎)2，BAIShi—wu(白世武)2，LIUFang．Hling(刘方明)2(1．SchoolofMaterials

2、ScienceandEngineering，TianjinUniversity,Tianjin300072，China；2．Petroleum—GasPipelineResearchInstituteofChina，Langfang065000，China)垒SpringerAbstract：Influencesofinspectingtime．intervalandlocationonvaryingbehaviorofmetalmagneticmemoryfMMMlsignalsofde埯ctswerestudied．Differentareasintwo

3、precrackedweldmentswereinspectedatdifferenttime—intervalsbytypeTSC一1M-4stress—concentrationmagneticinspectortoobtainMMMsignals．MechanismsofMMMsignalsvaryingbehaviorwithinspectingtimeandspacewereanalyzedanddiscussedrespectively．ItisfoundthatMMMsignalsdon’tchangewithinspectingtime—in

4、terval．sincestressfieldandmagneticleakagefieldmaintainunchangedatanytimeafterwelding．Ontheotherhand，MMMsignalsdiffergreatlyfordifferentinspectinglocations，becausestressfieldandmagneticleakagefieldareunevenlydistributedindefectiveferromagneticmaterials．Keywords：nondestructivetesting

5、；metalmagneticmemory；inspectinginterval；inspectinglocation1IntroductionStressconcentrationisoneofthefatalfactorscausingfatiguefractureofferromagneticequipmentsandstructures．Efiectiveearlydiagnosisanddetectionofstress—concentratedzonesbeforedamagearedemandedtopreventabruptfailures．R

6、eputedastheonlyeffc：ctivenondestructivetesting(NDT)methodforearlydefectdiagnosisanddetectionsofar,metalmagneticmemory(MMMlwasfirstlyputforwardat50thInternationalWeldingConfc：rencein1997．UnlikeconventionalNDTmethods，MMMinspectingtechniquecanbeutilizedtoimplementearlydetectionofdefec

7、tivepanswithhighstressconcentrationininspectedferromagneticstructuresandcomponents【1。“．ThefundamentalprincipleofMMMtestingistodetecttheself-magneticleakagefield．whichgeneratesinstablegliding．dislocationzoneswithstressconcen仃ationinferromagneticmaterials．Instress—concentratedpartsof

8、ferromagneticstructures．ta