相控阵超声检测技术基本原理ndtday2rev11对照

GeneralPhasedGeneralPhasedArrayUltrasonic相控阵超声检测技术基本TrainingDayCopyright©TWILtdDay2isdividedDay2isdividedinto2第二天内容分为两部分1.CompletionofthebasicPhasedArray相控阵基本原理的2.IntroductiontoInitialCalibration初始校准内容的Copyright©TWILtdPhasedArrayTheoryisPhasedArrayTheoryissplitinto3相控阵原理可分为3DesignofUltrasonic超声探头Wave声波传ModificationofUltrasonicBeamShape(Beam超声波束的波形Copyright©TWILtdProbe探头设e.g.SubProbe探头设e.g.SubElementSize0.3mmwith0.1mm如：晶片0.3mm，间隙晶Matching匹配Copyright©TWILtdBackingBridgedSub分割小晶CompositeWhethersingleelementprobeorWhethersingleelementprobeorphasedarrayprobe,thepiezoeffectsarethesameandlayersofconstructionessentiallyidenticalCopyright©TWILtdLensAsinglewavefrontformswith bendingattheedgesdisplacesparticlesalongtheelementAsinglewavefrontformswith bendingattheedgesdisplacesparticlesalongtheelement面Adisplacementpointexistsateverydomainpoint每个区域有一个位UnstressedStressedWhenavoltageisappliedthepiezoeffectexpandstheelementinsynchronisationwiththevoltageamplitude施加电压时，晶片产生与电压幅值同步的逆压电效Copyright©TWILtd•PiezocompositeMaterialsweredeveloped•PiezocompositeMaterialsweredevelopedtoimprove压电复合材料的开发应用大大提高了探头的分辨MaterialsincludeLeadMetaniobate,PZT(leadzirconatetitanate)andPVDF(PolyVinylidineDiFluoride)具体材料有偏铌酸铅，压电陶瓷（锆钛酸铅）和聚二氟乙烯（聚偏氟乙烯Piezocompositesareusedtomakeprobesusinga‘sliceanddice’or‘1-3structure’.应用压电复合材料加工探头，一般采用切片式或1-3结构In1-3structurePiezoelectricrodsareembeddedinaepoxy在1-3结构中，压电陶瓷棒上包有固化环氧树Matchinglayeris匹配层厚度为Backingmaterialreducespulselengthandabsorbsinternal背胶层可缩短发射脉冲的长度，吸收探头内部的反射Probecablingisveryhighqualitytoreduce探头连线质量非常高，以较少损••••••Copyright©TWILtd•ThepiezocompositeThepiezocompositematerialisdesignedtoreduce•ThepiezocompositeThepiezocompositematerialisdesignedtoreducethecrosscouplingbetweenneighbouringelements,whichisnecessarytosteerthebeam.•MatchingThematchinglayerisdesignedtooptimisetheenergytransfer,toshortenthepulselengthandtobewearresistant.Copyright©TWILtd•ThebackingThe•ThebackingThebackingmaterialisdesignedtoshortenthepulselengthandattenuatethebackecho.•TheThecableattenuationmustbeaslowaspossible,mainlyforhighfrequencyprobes.ItselectricalimpedanceismatchedtoprobeandelectronicCopyright©TWILtd•Piezoelectricrodsareembeddedinaepoxymatrix(1-3structure)•Piezoelectricrodsareembeddedinaepoxymatrix(1-3structure)压电陶瓷棒上包有固化环氧树•ThisimprovesthepropertiesofthepiezocompositematerialwhichisusuallyPZT(LeadZirconateTitanate)Sliceand切片式•Copyright©TWILtd•Deflectionindepth•Deflectionindepthandangleinoneplane在深度方向上波束发生•Elliptical椭圆形Copyright©TWILtd•Deflectionindepth•Deflectionindepthandanglein2planes在深度方向上波束发Elliptical椭圆形•Copyright©TWILtd•Deflectionindepth•Deflectionindepthandanglein2planes在深度方向上波束发Elliptical椭圆形•Copyright©TWILtdDepthDeflectionDepthDeflection•Spherical球形波•Copyright©TWILtd•Deflectionin•DeflectioninDepthandanglein2planesSphericalorelliptical球形或椭圆形•Copyright©TWILtdggap（间隙ggap（间隙eelementwidth（晶片宽度Aaperture（孔径P=pitch（中心间距Welementheight（晶片高度）nnumberofelements（晶片数量Activeapertureisthesteeringplane(A)Passiveaperturehasnosteeringcapability(W)Copyright©TWILtdPrincipleof工作原•Eachelementisfiredindividually,propagatinganultrasonic每个晶片被单独激发，发射传播AsthePrincipleof工作原•Eachelementisfiredindividually,propagatinganultrasonic每个晶片被单独激发，发射传播Asthewaveexpands,thewavefront随着波束向前传播，波阵面在逐步延伸扩展Ifalltheelementsarefiredsimultaneously,theresultingwavefrontformsalongitudinalorcompressionwave如果同时激发所有晶片，最后波阵面形成一束纵波或压缩波••Copyright©TWILtdPhasedArrayTechnology-Principlesof相控阵技术-工作•Agroupofelementsarefiredelectronicallyinsequencealongthelengthofthetransducer(e-scan).沿着探头PhasedArrayTechnology-Principlesof相控阵技术-工作•Agroupofelementsarefiredelectronicallyinsequencealongthelengthofthetransducer(e-scan).沿着探头长轴方向，依序激活一组晶片（电子扫查Theresultingwavefronttravelsalongthelengthofthephasedarray波阵面沿着阵列探头长度方向向NothirdaxisofmechanicalmovementisrequiredforC-Scanmapping.••Copyright©TWILtdAngular角度扫•BeamSteeringisaccomplishedbydelayingthepulsingofeachelementelectronicallyatasetrate.延时每个晶片的脉冲激发，进行Angular角度扫•BeamSteeringisaccomplishedbydelayingthepulsingofeachelementelectronicallyatasetrate.延时每个晶片的脉冲激发，进行Theresultingwavefronttravelsalongatanangledependantonthetimedelaybetweenfirings.波阵面以一定角度向前移动，角度的大小取决于晶片间的激发延时•Copyright©TWILtdCopyright©TWILtdBeam波束聚Copyright©TWILtdBeam波束聚BeamLinear查Focal聚焦Copyright©TWILtdBeamLinear查Focal聚焦Copyright©TWILtd•Probeparameterslearnedin•ProbeparameterslearnedinLevel1UTinsingleelementareequallyapplicabletoPhasedArraybeamanalysis–Near近场–Beam声束扩Spotsize(beamdiameter焦点尺寸（声束直径Copyright©TWILtdN=D2/4asN=D2/4asafirstND2/4Where:•DisprobeD指探头直thewavelengthinthemediumtransmitted(assumesMoreaccuratelyN=(D2-2)/4指波在介质中传播的波长（假设<DN=(D2-2•Note:importantwhenDandaresimilardimensionsasinthecaseofthesmallelementsinPAprobes.Copyright©TWILtd•Sin(t/2)==•Sin(t/2)==–forcircular•Sin(t/2)==–forrectangularCopyright©TWILtd•Beamspreadlimitedto-6dB波束扩散限制•Beamspreadlimitedto-6dB波束扩散限制在-6dBAPointAisOKbecauseallraysarewithinelemental的所有波均在波束扩散限制宽PointByieldsresultsbecauseraysareoutsideelementalbeam-BCopyright©TWILtd••ApproximatedbyBD••ApproximatedbyBD–••••BD=BeamD=istheprobeF=Chosenfocal选择的聚焦范=wave波••NOTE:formulaisforcontinuouswavenotpulseInpractice10to20%larger实际尺寸要理论值大10-Copyright©TWILtdNearzonecanbethoughtNearzonecanbethoughtofasanaturalfocal近场区可视为一个Geometricfocusinginalenseffectivelyforeshortensthenearzone几何透镜聚焦可有效缩短Electronicfocusinggenerallytperformyefunctinsthanadens.Butitnbetechnicallybetterforanumberof尽管，与透镜聚焦相比，电子聚焦并未提供更多的的聚焦功能，但在技术方面有较大优势结论Focuscannotbelongerthanthenaturalnearzonepointforagivencrystalsizeandfrequency.给定了晶体的尺寸和频率，焦距不会大于其自然近场距离Theminimumfocallengthisgovernedbythecriticalangleofabeam(>10%N),thereforecan’tfocusinfirst10%N.最小焦距受波束临界角限制（>10%N），因此不能在近场区首个10%区域Copyright©TWILtd5MHz相控阵探头325MHz相控阵探头32晶片，聚焦位置Copyright©TWILtd5MHz相控阵探头85MHz相控阵探头8晶片，聚焦位置Copyright©TWILtdFocalspotFocalspotsizedecreaseswhensameaperture(32elements)isusedtofocusatshorterdistances运用相同的孔径（32个晶片）聚焦，聚焦距离越短，聚焦尺寸越小Copyright©TWILtdTheequationforspotTheequationforspotsizeisapplicabletoBOTHsinglecrystalandPhasedArraySimplyreplacethecrystaldiameterbythePhasedArrayaperture(dimensionofelementsused(A))tocalculatetheNearzoneandspotsize相控阵应用中，计算近场区和聚焦尺寸时，只需将晶体尺寸改为激活孔径尺寸即可Copyright©TWILtd•示例12mmFlatProbe平面12mmFocusat聚焦位置•示例12mmFlatProbe平面12mmFocusat聚焦位置FocusedBeamat15mmis1.6mmdiameter(i.e.½ofFlatelementbeamat30mmnaturalfocus3.2mmdiameterCopyright©TWILtd1.Energydistribution1.Energydistributionin波束能量的分Interference干涉条Probeshoenoisedueto探头内部发射引起的Copyright©TWILtdTakeeachelementinitsTakeeachelementinitsownright从每个晶片的角度考虑Eachelementhasanearzoneandbeam每个晶片发射的波束均有一个近场区，也发生Thelargertheelementsthesmallerthebeam晶片尺寸越大，声束扩散Thesumoftheindividualbeamsmakesthefull所有单一晶片发射的波束结合起来形成全波束Youcannotsteeranelementsowngenerated不能控制单个晶片发射的Yousteerthecombinedeffectofallthe但可控制所有晶片发射波束的综Ultrasonicbeamshapedependsuponthefollowing超声波形取决于以a)孔Frequency.Elementsize.晶片尺Elementpitch.Timedelaysbetweeneach晶片间的激f)Powerofeach每个晶片的Copyright©TWILtdCopyright©TWILtdCopyright©TWILtdof5MHzPAProbeof5MHzPAProbe32focusedat70mm5MHz相控阵探头32晶片，聚焦位置70mm（0.5N）ofPeakNDTPeakNDT幻灯Copyright©TWILtd5MHzPA5MHzPAprobe32elementsfocusedat70mm0.5Nwithtransmitvoltageapodisation5MHz相控阵探头3270mmCopyright©TWILtd5MHzPA5MHzPAprobe32elements5elementsturnedoff5MHz相控阵探头32晶片，其中关闭5个晶Copyright©TWILtd5MHzPA5MHzPAprobe32elementsfocusedat15mm0.5N5elementsnotfunctioning5MHz相控阵探头32晶片，聚焦位置15mm0.5N，5Copyright©TWILtd仪仪Capabilitiesand功能与Copyright©TWILtdLosses损耗•InstrumenttendtoLosses损耗•Instrumenttendtobenoisierbecauseoftheamountofelectronicactivityonadjacentchannelsandthepowertoeachelement相邻通道间的电子激活量以及每个晶片的功率，均影响仪器的噪声大小Gains增益•Phasedarrayprobesandinstrumentationprovidenaturalsignal相控阵探头和仪器具有信号平均Thisisprovidedbecauseofthemultipleelementsreceivingthesignalsatdifferingtimesfromagiventarget每个晶片接收到同一目标点的信号在时间上是有差异的，Butelectronicnoiseisreceivedatthesametimeforeach••但每个晶片接收到的电子噪声在时间上是一致的，因此需要平均化处理Foragivenappliedvoltagetheconstructiveinterferenceprovidesatleast6dBmoretransmittedpressurecomparedtosingleelementsystems与单晶系统相比，相控阵系统在给定的电压下工作时，由于干涉作用的存在，在发射电压的基础上至少提高了dB•Copyright©TWILtdSingle单探头/ElectronicSingle单探头/Electronic电子Defect缺陷Copyright©TWILtdTime时间1st第一Time时间1st第一个晶2nd第二个晶Copyright©TWILtdAddthesignalsfrombothelementsAddthesignalsfrombothelementstogetheranddivideby两探头的信号求和Defect缺陷Electronic电子Copyright©TWILtd•Far-fieldpattern•Far-fieldpatternofanarrayprobeshowsamainbeamandgratinglobesatregularangularArraylobesreduceusefulsteeringrange,andmaygeneratemultipleimages•Copyright©TWILtdFOURIERTRANSFORM傅立叶变化•Beamwidth(mainbeam,lobes)determinedbyaperture(A)SteeringcapabilityisdeterminedFOURIERTRANSFORM傅立叶变化•Beamwidth(mainbeam,lobes)determinedbyaperture(A)Steeringcapabilityisdeterminedbyelementwidth(e)控制能力取决于晶片宽度Angularpositionoflobesdeterminedbyfrequencyfandpitchp: p•Z•Fourierp-Copyright©TWILtd Elementsize(e)λ,SideLobesElementsize(e)λ,SideLobeswille<λ/2,NoSideLobeseλ/2•••<<λ,Lobeangularpositionwilldependsteeringangletobe<<Copyright©TWILtdInfluenceofpitch(forA=激活孔径固定Influenceofpitch(forA=激活孔径固定Ifp,andn如果晶片中心距p，同时晶片数量nthenlobedistance则波瓣偏离距andlobeamplitude波瓣幅值–––Copyright©TWILtdArrayMain8Elements(Pitch8Elements(Pitch8晶片（中心间距6Elements(Pitch12Elements(Pitch4Elements(Pitch6晶片（中心间距1mm）12晶片（中心间距0.4mm）4晶片（中心间距IDEALSOLUTIONTOGRATINGLOBESISTODESIGNTHEMCopyright©TWILtdCopyrightCopyright©TWILtdCopyright©Copyright©TWILtdBeam波束Fermatprinciple费马原theactualpathbetweentwopointstakenbyabeamoflight(orsound)istheonethatistraversedintheleasttime.TheequipmentsearchesforFermatprinciple费马原theactualpathbetweentwopointstakenbyabeamoflight(orsound)istheonethatistraversedintheleasttime.TheequipmentsearchesfortheSnellpoint.Thecentreoftheactiveaperture.(fromelements2to7inthis激活孔径的中心（例中为第2-7晶片Then,theX,Zpointofthefocalpointisdetermined确定焦点的X,Z坐标ThewedgedelayandpathlengthisthencalculatedSnell思奈XaxisorScanX轴或扫查界scan扫查偏深Focal焦点Copyright©TWILtdThecentralrayfollowingSnell’sLawlocatesthearraywithrespecttothepointoffocusandthencalculationsaremadeforeachraypathfromtheelementsusedtothepointoffocusXaxisorScanThecentralrayfollowingSnell’sLawlocatesthearraywithrespecttothepointoffocusandthencalculationsaremadeforeachraypathfromtheelementsusedtothepointoffocusXaxisorScanX界Sound声程（时间Inwedge楔块Inmateriel材料Focal焦点Element晶片Copyright©TWILtdFermatcalculationsdonotconsidersteeringlimits(beamdivergence)sootherfactors,suchasprobedesign,Fermatcalculationsdonotconsidersteeringlimits(beamdivergence)sootherfactors,suchasprobedesign,mustbeconsideredwhenusingthephasedarrayprobeforanapplication费马理论不考虑波束控制限制（波束发散）素，如探头设计。但当实际应用相控阵探头时，则必须考虑这些因素。Copyright©TWILtdPhased-ArrayinspectionsrequireextracompensationsnotconsideredPhased-Arrayinspectionsrequireextracompensationsnotconsideredinsingleelement•SteeringLimits(withorwithouta控制限制（无论是否配有楔块Angledependence(echo-transmittanceeffects)Attenuationvariations(withwedges)duetovariablepathtimesinthewedge楔块中传播声程的不同引起衰减的不同（配有楔块时••Copyright©TWILtdSteeringSteeringLimits(withorwithouta控制限制（无论是否配有楔块Alreadyconsideredinprobe在探头设计时已Copyright©TWILtdAngledependenceA