CautionwhenapplyingeddycurrentinversiontostresscorrosioncrackingOriginalResearchArticle

Thisstudyevaluatestheapplicabilityofcomputer-aidededdycurrentinversiontechniquestotheprofileevaluationofstresscorrosioncrackinginInconelwelds.Weldedplatespecimens,whichmodelheadpenetrationweldsofpressurizedwaterreactors,arefabricated;notchesandstresscorrosioncracksareartificiallyintroducedintotheweldmetalofthespecimens.Eddycurrentinspectionsareperformedusingauniformeddycurrentprobedrivenatfrequenciesof10and40kHz.Sinceweldnoiseisobserveduniformlyalongtheweldline,asimplesignalprocessingisappliedtoeliminateit.First,theartificialnotchesarereconstructedandgoodagreementsbetweenreconstructedandtrueprofilesareprovided,whichdemonstratesthatthecomputer-aidededdycurrentinversiontechniquecandealwithdefectsinwelds.Then,numericalsimulationsareperformedtoevaluatetheprofilesofthestresscorrosioncracks.Inthenumericalsimulations,thestresscorrosioncracksaremodeledasaconductiveregionwithafixedwidthof0.3mm.Thecross-sectionalprofilesofthecracksarereconstructedfrommeasurededdycurrentsignalsdirectlyaboveandalongacrack.Althougheddycurrentsignalscalculatedfromthereconstructedprofilesagreewellwithmeasuredones,thetrueprofilesrevealedbydestructivetestingarefoundtobeverydifferentfromthereconstructedones.Whereasthemostplausiblereasonforthedifferenceistheunexpectedlyvolumetricprofileofthestresscorrosioncracks,thisstudyhasrevealedthatcomputer-aidededdycurrentinversiontechniquesthathavebeenusedtoconsidercracksinthinstructureswouldnotatthispointbedirectlyapplicabletothoseinthickstructures.Itisalsoimportanttoknowinadvancethosecrackfeaturesthatcanadverselyimpactaccuratecracksizingincludingwhetheradetectedcrackisvolumetricornot,namelytherearemanyparallelcracksinaclusterornot.