Physics of Eddy Current-An Introduction

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1、PhysicsofEddyCurrent-ET-AnUnderstanding2014-OctoberMyASNTLevelIIIPre-ExamPreparatorySelfStudyNotesCharlieChong/FionZhangExpertatWorksCharlieChong/FionZhangExpertatWorksCharlieChong/FionZhanghttp://eddycurrent.net/gallery/index.php/Palm-Cooling-Discovery-Garde

2、ns/IMG_2100ExpertatWorksCharlieChong/FionZhanghttp://ropax.co.uk/eddy-current-inspection.htmlExpertatWorksCharlieChong/FionZhanghttp://ropax.co.uk/eddy-current-inspection.htmlExpertatWorksCharlieChong/FionZhanghttp://ropax.co.uk/eddy-current-inspection.htmlCh

3、arlieChong/FionZhangOverview:Eddy-currenttestuseselectromagneticinductiontodetectflawsinconductivematerials.Theeddycurrenttestset-upconsistsofacircularcoilwhichisplacedonthetestsurface.Thealternatingcurrentinthecoilgenerateschangingmagneticfieldwhichinteracts

4、withtheconductivetestsurfaceandgenerateseddycurrent.Theflowofeddycurrentcanbedisruptedduetochangeinresistivityorconductivity,magneticpermeability,anyphysicaldiscontinuities.Thechangeineddycurrentflowandacorrespondingchangeinthephaseandamplitudeismeasuredagain

5、stknownvalues.Eddycurrenttestmethodcandetectverysmallcracksinornearthesurfaceofthematerial,thesurfacesneedminimumpreparation.Thebiggestadvantageoftheeddycurrenttestmethodisthatiscanbeemployedtodeterminesurfaceflawsonpaintedorcoatedsurface.Eddycurrentflawdetec

6、tioniscommonlyusedintheaerospaceindustry,craneindustry,concretepumpingindustryandothergeneralindustrieswheretheprotectivesurfacecoatingcannotberemoved.CharlieChong/FionZhangThecraneindustryandcraneownersbenefitsmostfromtheapplicationofeddycurrenttestmethodtod

7、etectsurfaceflawsunderneaththeprotectivecoating(paint).Theexorbitantcostofpaintremovalandrepaintingiseliminatedbyapplyingeddycurrentflawdetectionmethodascomparedtomagneticparticletest.Itisalsousefulformakingelectricalconductivityandcoatingthicknessmeasurement

8、s.Eddycurrenttestiscommonlyemployedforrapidthicknesstestingofcoatings–conductiveandnon-conductive.Theprincipleofeddycurrenttestwhichmeasuresthechangeinresistivityintheconductivematerialma