《TOFD检测（双语）》课件-18.灵敏度设置

灵敏度设置

SensitivitysettingTOFD检测技术

TOFDTestingTechnology增益设置与校准方法的选择

GainSettingandCalibrationSelectionofGain-SettingMethod1TOFD检测增益的设置方法

MethodsforSettingtheGaininTOFDTesting2选择设置增益方法的小结

SummaryofGain-SettingMethods3知识目标

Knowledgeobjectives教学目标

Teachingobjectives增益过低

GainTooLow增益适中

AppropriateGain增益过高

GainTooHighTOFD检测的定量是不依靠信号波幅的，但系统增益的设置会影响检测的可靠性。

DefectsizinginTOFDtestingdoesnotrelyonsignalamplitude.However,thesystemgainsettingaffectsinspectionreliability.增益过低缺陷的衍射信号过于微弱，就不能被接收和观察到。

Ifthegainistoolow,diffractedsignalsfromdefectsmaybetooweaktobereceivedordisplayed.增益过高也会影响图像的观察、信号的识别和测量，同样影响缺陷的检出。

Excessivegaincanimpairimageinterpretation,signalidentification,andmeasurement,therebyadverselyaffectingdefectdetection.增益设置与校准方法的选择

SelectionofGain-SettingandCalibrationMethods识别缺陷：使缺陷信号在局部噪声背景下是可分辨的

Defectidentification:Thedefectsignalmustbedistinguishablefromthelocalnoisebackground分析缺陷性质：有时需要依据缺陷上下端点信号的相对高度来分析判断缺陷性质

Defectcharacterization:Insomecases,therelativeamplitudesofthesignalsfromtheupperandlowerdefecttipsmaybeusedtohelpcharacterizethedefect校验系统灵敏度：有时需要用人工缺陷的脉冲高度确认系统灵敏度没有改变

Systemsensitivityverification:Thesignalamplitudefromanartificialreflectormaybeusedtoverifythatthesystemsensitivityhasnotchanged在英国BS7706-1993标准指出，波幅在TOFD检测中有以下三种用途：

BritishStandardBS7706:1993identifiesthefollowingthreeusesofsignalamplitudeinTOFDtesting:增益设置与校准方法的选择

SelectionofGain-SettingandCalibrationMethods用直通波设置

GainSettingUsingtheLateralWave用晶粒噪声设置

GainSettingUsingGrainNoise用底面反射波设置

GainSettingUsingtheBack-WallEcho用尖角槽的衍射波设置

GainSettingUsingtheDiffractedSignalfromaSharp-EdgedNotch用侧孔的反射波设置

GainSettingUsingtheEchofromaSide-DrilledHoleTOFD检测增益的设置方法

MethodsforSettingtheGaininTOFDTesting1.用直通波设置（最优先）

GainSettingUsingtheLateralWave:PreferredMethod操作：探头装在工件上，设好时间窗口、PCS，焊缝区直通波调到满屏40%～80%。

Procedure:PositiontheprobesontheworkpieceandsetthetimewindowandPCS.Adjustthelateral-waveamplitudeintheweldregionto40%–80%offull-screenheight.标准依据：NB/T47013.10，厚度≤50mm、单通道首选。

Standardbasis:AccordingtoNB/T47013.10,thismethodispreferredforsingle-channelinspectionofworkpieceswithathicknessof50mmorless.TOFD检测增益的设置方法

MethodsforSettingtheGaininTOFDTesting不能用直通波设置的情况：

Thelateralwavecannotbeusedforgainsettingunderthefollowingconditions:表面裂纹、咬边、凹槽挡住直通波；

Surfacecracks,undercut,orgroovesobstructthelateralwave;折射角小、波束陡、扩散小，无直通波；

Therefractedangleissmall,thebeamissteep,andthebeamspreadisnarrow,sonolateral-wavesignalisproduced;PCS太大、能量弱，直通波看不见；

ThePCSistoolargeandthesignalenergyistoolowforthelateralwavetobedisplayed;厚板分区扫查下部通道；

Alowerchannelisusedduringzonalinspectionofathickplate;焦点设在底部的特殊扫查。

Aspecialscanisperformedwiththebeamintersectionpointpositionednearthebackwall.TOFD检测增益的设置方法

MethodsforSettingtheGaininTOFDTesting1.用直通波设置（最优先）

GainSettingUsingtheLateralWave:PreferredMethodD扫图像

D-ScanImageTOFD检测波束

TOFDInspectionBeamsA型检测波型

A-ScanWaveformTOFD检测增益的设置方法

MethodsforSettingtheGaininTOFDTesting1.用直通波设置（最优先）

GainSettingUsingtheLateralWave:PreferredMethod2.用晶粒噪声设置

GainSettingUsingGrainNoise操作：探头放工件干净母材区，显示直通波和底波，调增益使晶粒噪声满屏5%～10%；

Procedure:Positiontheprobesonacleanareaoftheparentmaterialwhereboththelateralwaveandback-wallechocanbedisplayed.Adjustthegainuntilthegrainnoisereaches5%–10%offull-screenheight;直通波前电噪声比晶粒噪声低≥6dB。标准：NB/T47013.10，≤50mm、单通道可用。

Theelectricalnoiseprecedingthelateralwaveshouldbeatleast6dBlowerthanthegrainnoise.Standardbasis:AccordingtoNB/T47013.10,thismethodmaybeusedforsingle-channelinspectionofworkpieceswithathicknessof50mmorless.TOFD检测增益的设置方法

MethodsforSettingtheGaininTOFDTesting用晶粒噪声设置特点：

CharacteristicsofGainSettingUsingGrainNoise:增益高，小缺陷更容易检出；

Therelativelyhighgainmakessmalldefectseasiertodetect;噪声重、B/D扫过亮，分析难；

However,thehighnoiselevelmaymaketheB-scanandD-scanimagesexcessivelybrightanddifficulttointerpret;校验：底波测厚误差≤0.25mm，A扫参数才合格。

Verification:TheA-scansettingsareacceptableonlywhenthethicknessmeasurementerrordeterminedfromtheback-wallechodoesnotexceed0.25mm.2.用晶粒噪声设置

GainSettingUsingGrainNoiseTOFD检测增益的设置方法

MethodsforSettingtheGaininTOFDTesting如果采用晶粒噪声设置增益，必须保证所有的A扫参数都是正确的。

Whengrainnoiseisusedtosetthegain,allA-scanparametersmustfirstbeverifiedascorrect.确认的方法之一是：用设置完A扫参数的仪器探测被检工件，以工件底面反射波测定工件的厚度，与实际厚度的误差应在0.25mm之内。

OneverificationmethodistoinspecttheworkpieceusingtheinstrumentwiththeconfiguredA-scanparametersanddeterminetheworkpiecethicknessfromtheback-wallecho.Thedifferencebetweenthemeasuredandactualthicknessesshouldnotexceed0.25mm.TOFD检测增益的设置方法

MethodsforSettingtheGaininTOFDTesting2.用晶粒噪声设置

GainSettingUsingGrainNoise3.用底面反射来设置（备选）

GainSettingUsingtheBack-WallEcho:AlternativeMethod操作：底面波调到满屏80%，再提高20～32dB（常用18～30dB）。

Procedure:Adjusttheback-wallechoto80%offull-screenheight,andthenincreasethegainby20–32dB,with18–30dBcommonlyused.标准：≤50mm、单通道可用。

Standardbasis:Thismethodmaybeusedforsingle-channelinspectionofworkpieceswithathicknessof50mmorless.TOFD检测增益的设置方法

MethodsforSettingtheGaininTOFDTesting局限：底波受表面、耦合、材质影响大，不稳定，需试验或经验修正。

Limitation:Theback-wallechoisstronglyaffectedbysurfacecondition,coupling,andmaterialpropertiesandmaythereforebeunstable.Correctionsbasedontestingorpracticalexperiencemayberequired.D扫图像

D-ScanImageTOFD检测波束

TOFDInspectionBeamsA型检测波型

A-ScanWaveform3.用底面反射来设置（备选）

GainSettingUsingtheBack-WallEcho:AlternativeMethodTOFD检测增益的设置方法

MethodsforSettingtheGaininTOFDTesting用上表面开口尖角槽，下端点信号类似疲劳裂纹衍射；下表面槽以反射波为主，不用来校衍射灵敏度。

Useasharp-edgednotchopentotheinspectionsurface,becausethediffractedsignalfromitslowertipissimilartothatproducedbyafatiguecrack.Anotchopentothebackwallproducespredominantlyreflectedsignalsandisthereforenotusedtocalibratediffractionsensitivity.4.用尖角槽的衍射波设置（分区校准）

GainSettingUsingDiffractedSignalsfromSharp-EdgedNotches:ZonalCalibrationTOFD检测增益的设置方法

MethodsforSettingtheGaininTOFDTesting分区扫查时，每个分区25%、75%深度加工尖角槽；调增益使远处端点衍射波满屏60%，此时底波饱和。

Forzonalinspection,sharp-edgednotchesshouldbemachinedatdepthscorrespondingto25%and75%ofeachinspectionzone.Adjustthegainsothatthediffractedsignalfromthefarthernotchtipreaches60%offull-screenheight.Atthissetting,theback-wallechowillbesaturated.4.用尖角槽的衍射波设置（分区校准）

GainSettingUsingDiffractedSignalsfromSharp-EdgedNotches:ZonalCalibrationTOFD检测增益的设置方法

MethodsforSettingtheGaininTOFDTesting设置增益时，在满足信噪比要求的情况下把远处的端点衍射信号波调到满屏的60%，这种设置下，底面反射信号都非常饱和。

Whensettingthegain,adjustthediffractedsignalfromthefarthertipto60%offull-screenheightwhilemaintainingtherequiredsignal-to-noiseratio.Underthiscondition,theback-wallechowillgenerallybeheavilysaturated.5.用侧孔的反射波设置

GainSettingUsingtheEchofromaSide-DrilledHole以侧孔设置增益常被用于其他增益设置方法的验证或补充，侧孔是反射信号，比衍射信号强如果侧孔直径小于使用波长的2倍，需注意孔顶部与底部散射信号之间发生干扰，NB/T47013.10标准中，试块主要采用侧孔设置灵敏度。

Gainsettingusingaside-drilledholeisoftenusedtoverifyorsupplementothergain-settingmethods.Aside-drilledholeproducesareflectedsignalthatisstrongerthanadiffractedsignal.Iftheholediameterislessthantwicethewavelength,interferencebetweenthesignalsfromthetopandbottomoftheholeshouldbeconsidered.InthereferenceblocksspecifiedinNB/T47013.10,side-drilledholesareprimarilyusedforsensitivitysetting.TOFD检测增益的设置方法

MethodsforSettingtheGaininTOFDTesting用侧孔的反射波设置方法：

ProcedureforSettingtheGainUsingaSide-DrilledHole测量侧孔的信号峰值，区分顶部和底部的信号，选取其中较低值调至波高80%，记录增益值；

Measurethepeakamplitudesofthesignalsfromtheside-drilledhole,distinguishthesignalsfromthetopandbottomofthehole,adjustthelower-amplitudesignalto80%offull-screenheight,andrecordthegainvalue;参考噪声情况或根据经验确定增益是否适当，有时需要将增益再提高数dB。

Assesswhetherthegainisappropriatebasedonthenoiselevelorpracticalexperience.Thegainmayneedtobeincreasedbyseveraladditionaldecibels.5.用侧孔的反射波设置

GainSettingUsingtheEchofromaSide-DrilledHoleTOFD检测增益的设置方法

MethodsforSettingtheGaininTOFDTesting直通波法：直通波波幅调至满屏40%～80%；

Lateral-wavemethod:Adjustthelateral-waveamplitudeto40%–80%offull-screenheight;底面反射波法：直通波不可用时，底波调满屏后再增益18～30dB；

Back-wall-echomethod:Whenthelateralwavecannotbeused,adjusttheback-wallechotothespecifiedfull-screen-heightlevelandthenincreasethegainby18–30dB;晶粒噪声法：前两种均不可用时，将晶粒杂波调至满屏5%～10%。

Grain-noisemethod:Whenneitheroftheabovemethodscanbeused,adjustthegrainnoiseto5%–10%offull-screenheight.1.三种现场常用法

ThreeCommonFieldMethods选择设置增益方法的小结SummaryofGain-SettingMethods2.选择顺序

OrderofPreference直通波

Lateralwave底波

Back-WallEcho晶粒噪声，逐级替代

GrainNoise(FinalAlternative)选择设置增益方法的小结SummaryofGain-SettingMethods3.厚薄工件逻辑

ConsiderationsforThinandThickWorkpieces薄工件（厚度＜50mm）：声波传播路径简单，单对探头全覆盖检测，可直接在工件上完成灵敏度校准。

Thinworkpieces,withathicknessoflessthan50mm,haverelativelysimpleultrasonicpropagationpathsandcangenerallybefullycoveredbyasingleprobepair.Sensitivitycalibrationcanthereforebeperformeddirectlyontheworkpiece.厚工件（厚度＞50mm）：声波衰减大、单探头无法覆盖全深度，采用多对探头分区扫查，需对每个扫查区间单独设置灵敏度。

Thickworkpieces,withathicknessgreaterthan50mm,producegreaterultrasonicattenuationandcannotbefullycoveredthroughtheentirethicknessbyasingleprobepair.Multipleprobepairsarethereforeusedforzonalscanning,andthesensitivitymustbesetseparatelyforeachinspectionzone.分区完成灵敏度设置后，不能直接用于检测，必须使用含不同深度人工缺陷（槽、侧孔）或真实缺陷的参考试块，对已设灵敏度进行验证校准，保证全深度范围缺陷检出能力。

Afterthesensitivityhasbeensetforeachzone,thesettingsmustbeverifiedandcalibratedbeforeinspectionusingareferenceblockcontainingartificialreflectorsatdifferentdepths,suchasnotchesorside-drilledholes,orrepresentativerealdefects.Thisensuresadequatedefectdetectabilitythroughoutthefullthicknessrange.3.厚薄工件逻辑

ConsiderationsforThinandThickWorkpieces选择设置增益方法的小结SummaryofGain-SettingMethods01TOFD灵敏度设置，是为了保证有效识别缺陷衍射信号是TOFD检测的关键工艺步骤。

SensitivitysettingisacriticalstepinTOFDtestingbecauseitensuresthatdiffractedsignalsfromdefectscanbeidentifiedreliably.02TOFD一般不采用缺陷回波增益，灵敏度不能过高，增益过大会导致晶粒噪声、杂波增多，造成图像模糊、误判缺陷；灵敏度也不能过低，增益不足会造成微小缺陷衍射信号丢失，出现漏检。

TOFDgainisgenerallynotsetwithreferencetotheamplitudeofadefectecho.Thesensitivitymustnotbesettoohigh,becauseexcessivegainincreasesgrainnoiseandspurioussignals,resultinginblurredimagesandpossiblefalseindications.Itmustalsonotbesettoolow,bec