涡流阻抗图的傅里叶描述和分析

,(,442002)(,430074):,:;;:TG115.28;O174.2:A:100026656(2001)0920369203FOURIERDESCRIPTIONANDANALYSISOFEDDYCURRENTIMPEDANCEPATTERNSWUBu2ning,LIANGYu2hong(HubeiAutomotiveIndustriesInstitute,Shiyan442002,China)CHENZhi2xiang(HuazhongUniversityofScienceandTechnology,Wuhan430074,China)Abstract:Amethodofcharacterizingtheeddycurrent(EC)patternsbasedontwo2dimensionalFourierdescriptionofin2phaseandquadraturesignalsispresented.ThedescriptioncanbeconsideredasanapproximationoftheECpatternbyaparametricmodel.ItisshownthattheECpatternscanbeeasilyreconstructedfromthetwocomplextermsintheFouri2erexpansionandbothlowandhighfrequencynoisescanbeefficientlyfilteredoutduringthereconstruction.Keywords:Fouriertransform;Eddycurrenttesting;Impedancepattern,,,,,,,,:2001202209(),,,,,[1],,,96323920019NDTVol.23No.9Sep.2001©1995-2004TsinghuaTongfangOpticalDiscCo.,Ltd.Allrightsreserved.1,[2],,[3]()()(),,,[4,5],,,[3],2,[1],T,u(t)=x(t)+jy(t),j=-1x(t)y(t)u(t)=n=-Cnexpj2tT(1)Cn=1TT0u(t)exp-j2ntTdt(2),C-n=-CnC0=0,u(t)=2j[C1sin(t)+C2sin(2t)]=2TC1=r1expj-2C2=r2expj-2+u(t)=2exp(j)[r1sin(t)+r2exp(j)sin(2t)](3),C1C2,r2A=4r1r2sinC1C2,=0,C1C2,=90,1,r1/r2,(a)(b)(c)r2,=/4(d)r2,=-/41(),,2.12073:©1995-2004TsinghuaTongfangOpticalDiscCo.,Ltd.Allrightsreserved.,;,,,(2),(3),2.2,,,,,,2,,2323,(1),,(1),,4(a)(b)4,)3,,(),:[1]UdpaSS,LordW.AFourierdescriptorclassificationschemefordifferentialprobesignals[J].MaterialsEval2uation,1984,42(8):1136-1141.[2]LibbyHL.Introductiontoelectromagneticnondestruc2tivetestmethods[M].NewYork:JohcWiley&SonsInc,1971.[3]BirnbaumG,FreeG.EddyCurrentCharacterizationofMaterialsandStructures[M].Philadelphia:ASMPubli2cation,1981.[4],.[J].,2000(22):243-245,268.[5]JenkinsStaveA.Eddycurrentinspectionsimulanters:computer2aidedlearning[J].MaterialsEvaluation,1993,51(11):1226-1236.173:©1995-2004TsinghuaTongfangOpticalDiscCo.,Ltd.Allrightsreserved.