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ID:32923829
大小:1.20 MB
页数:23页
时间:2019-02-17
《Eddy Current- In Brief》由会员上传分享,免费在线阅读,更多相关内容在学术论文-天天文库。
1、ElectromagneticTestingEddyCurrentinBrief2014-DecemberMyASNTLevelIIIPre-ExamPreparatorySelfStudyNotes外围学习中CharlieChong/FionZhangEddycurrenttestingisusedtofindsurfaceandnearsurfacedefectsinconductivematerials.Itisusedbytheaviationindustryfordetectionof
2、defectssuchascracks,corrosiondamage,thicknessverification,andformaterialscharacterizationsuchasmetalsortingandheattreatmentverification.Applicationsrangefromfuselageandstructuralinspection,engines,landinggear,andwheels.Eddycurrentinspectioninvolvesin
3、itialsetupandcalibrationprocedureswithknownreferencestandardsofthesamematerialasthepart.Probesofappropriatedesignandfrequencymustbeused.Eddycurrentinspectionisbasedontheprincipleofelectromagneticinduction.Anelectriccoilinwhichanalternatingcurrentisfl
4、owingisplacedadjacenttothepart.Sincethemethodisbasedoninductionofelectromagneticfields,electricalcontactisnotrequired.CharlieChong/FionZhangFigure1.SchematicofEddyCurrentabsoluteprobeCharlieChong/FionZhangAnalternatingcurrentflowingthroughthecoilprod
5、ucesaprimarymagneticfieldthatinduceseddycurrentsinthepart.Energyisneededtogeneratetheeddycurrents,andthisenergyshowsupasresistancelossesinthecoil.TypicalNDEapplicationaredesignedtomeasuretheseresistancelosses.Eddycurrentsflowwithinclosedloopsinthepar
6、t.Figure2.DiagramillustratingEddyCurrentscreatedinaportCharlieChong/FionZhangAsaresultofeddycurrents,asecondmagneticfieldisgeneratedinthematerial.Themagneticfieldsofthecoreinteractwiththoseinthepartandchangesinthematerialbeinginspectedaffecttheintera
7、ctionofthemagneticfields.Theinteraction,inturn,affectstheelectricalcharacteristicsofthecoil.Resistanceandinductivereactanceadduptothetotalimpedanceofthecoil.Changesintheelectricalimpedanceofthecoilaremeasuredbycommercialeddycurrentinstruments.So,what
8、doesallofthishavetodowithnondestructivetesting?Themainmethodusedineddycurrentinspectionisoneinwhichtheresponseofthesensordependsonconductivityandpermeabilityofthetestmaterialandthefrequencyselected.CharlieChong/FionZhangHoweddycurrentsarecreatedandse
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