《TOFD检测（双语）》课件-7.TOFD检测声束扩散角影响因素

TOFD检测声束扩散角影响因素

FactorsAffectingtheBeamSpreadAngleinTOFDDetectionTOFD检测技术

TOFDTestingTechnology影响TOFD检测声束扩散角的因素有哪些

WhatFactorsAffecttheBeamSpreadAngleinTOFDTesting?1各因素对TOFD检测声束扩散角有何影响

HowDoesEachFactorAffecttheBeamSpreadAngleinTOFDTesting?2TOFD检测声束扩散角实际应用

PracticalApplicationofBeamSpreadAnglesinTOFDTesting3知识目标

Knowledgeobjectives教学目标

Teachingobjectives当α取下表任一角度时，楔块中α1和α2均存在下述关系：

Whenαissettoanyoftheangleslistedinthetablebelow,thefollowingrelationshipsapplytoα₁andα₂inthewedge:波束在楔块中的角度

BeamAngleintheWedge波束在钢中的角度

BeamAngleinSteelα=16.57°β=45°α=20.44°β=60°α=22.27°β=70°由上式可知：θ数值直接影响α1和α2的数值。

Theequationaboveshowsthatθdirectlyaffectsthevaluesofα₁andα₂.影响TOFD检测声束扩散角的因素有哪些

WhatFactorsAffecttheBeamSpreadAngleinTOFDTesting?声束半扩散角公式：

Thehalf-beam-spreadangleiscalculatedusingthefollowingequation:

θ∈(0,π/2），sinθ由F、f和D共同决定。

Forθ∈(0,π/2),sinθisdeterminedjointlybyF,f,andD.影响TOFD检测声束扩散角的因素有哪些

WhatFactorsAffecttheBeamSpreadAngleinTOFDTesting?截取波束边缘的声压下降值

Sound-PressureDropUsedtoDefinetheBeamEdge声压下降值6dB

6dBSound-PressureDrop声压下降值12dB

12dBSound-PressureDrop声压下降值20dB

20dBSound-PressureDrop扩散因子F值

Beam-SpreadFactorFF-6=0.51F-12=0.7F-20=1.08随F增加，θ增大；

AsFincreases,θincreases;θ增大，导致α1增大，α2减小；

Asθincreases,α₁increasesandα₂decreases;α1增大，α2减小，导致在钢中扩散角整体增大。

Theincreaseinα₁anddecreaseinα₂resultinagreateroverallbeamspreadangleinsteel.当f和D一定时

WhenfandDAreConstant各因素对TOFD检测声束扩散角有何影响

HowDoesEachFactorAffecttheBeamSpreadAngleinTOFDTesting?f越大，楔块中λ越小；

Asfincreases,λinthewedgedecreases;f越大，同一晶片θ越小；

Foragivenelementdiameter,θdecreasesasfincreases;f一定，θ随D减小而增大。

Ataconstantfrequency,θincreasesasDdecreases.当F一定时（例：F=0.7时）

WhenFIsConstant,forExample,F=0.7频率，MHz

Frequency(MHz)在楔块中的λ，mm

WavelengthλintheWedge(mm)θ角度

AngleθD=15mmD=10mmD=6mm30.82.123.215.3450.481.262.063.21100.240.630.961.6不同频率和晶片尺寸探头的楔块中的波长和波束扩散角

WavelengthsandBeamSpreadAnglesintheWedgeforProbeswithDifferentFrequenciesandElementSizes由上表可知，获得最大声束扩散角的两个途径是：①选最低的频率；②选最小的晶片。

Asshowninthetableabove,thebeamspreadanglecanbemaximizedintwoways:①byselectingthelowestfrequencyand②byselectingthesmallestelement.各因素对TOFD检测声束扩散角有何影响

HowDoesEachFactorAffecttheBeamSpreadAngleinTOFDTesting?f减小，扩散区间增大；

Asfdecreases,thebeamspreadrangeincreases.f减小，同一晶片扩散区间增大；

Foragivenelementdiameter,thebeamspreadrangeincreasesasfdecreases;f一定，D减小，扩散区间增大。

Ataconstantfrequency,thebeamspreadrangeincreasesasDdecreases.当声束中心角度一定α（例：α=60°)

WhentheCentralBeamAngleαIsFixed,forExample,atα=60°不同频率和晶片尺寸探头的声束扩散角

BeamSpreadAnglesofProbeswithDifferentFrequenciesandElementSizes频率，MHzc

Frequency(MHz)中心声束角度为60°探头在钢中的声束扩散

BeamSpreadinSteelforaProbewithaCentralBeamAngleof60°D=5mmD=10mmD=15mm340.2-9047.3-8451.1-72.2547.3-8451.9-70.654.5-66.51053.2-68.555.8-64.857.1-63.1各因素对TOFD检测声束扩散角有何影响

HowDoesEachFactorAffecttheBeamSpreadAngleinTOFDTesting?从分辨力和声束强度的因素考虑，似乎应优先选择高频和大直径探头，但是在以发现缺陷为目的的初始阶段，声束的覆盖往往为考虑的第一因素，这使我们不得不选择低频率和小直径探头。

Fromtheperspectivesofresolutionandbeamintensity,probeswithhigherfrequenciesandlargerelementdiameterswouldappearpreferable.However,duringtheinitialstageofdefectdetection,beamcoverageisgenerallytheprimaryconsideration.Therefore,probeswithlowerfrequenciesandsmallerelementdiametersmustoftenbeselected.当已经发现缺陷并知道其大致位置后，就需要更多考虑分辨力因素，选择更优化设置进一步精确扫查，以便测定缺陷的尺寸。

Onceadefecthasbeendetectedanditsapproximatelocationisknown,greateremphasisshouldbeplacedonresolution.Amoresuitableprobeconfigurationshouldthenbeselectedforfurtherprecisionscanningandaccuratedefectsizing.TOFD检测声束扩散角实际应用原则

PrinciplesforthePracticalApplicationofBeamSpreadAnglesinTOFDTesting01了解影响TOFD检测声束扩散角的因素有哪些

UnderstandtheFactorsAffectingtheBeamSpreadAngleinTOFDTesting02掌握各因素对TOFD检测声束扩散角的具体影响

UnderstandHowEachFactorAffectstheBeamSpreadAngleinTOFDTesting03了解TOFD检测声束扩散角实际应用原则

UnderstandthePrinciplesforthePracticalApplicationofBeamSpreadAnglesin