【英文标准名称】:StandardPracticeforUltrasonicAngle-BeamContactTesting
【原文标准名称】:超声波角钢梁接触试验标准实施规程
【标准号】:ASTME587-2010
【标准状态】:现行
【国别】:美国
【发布日期】:2010
【实施或试行日期】:
【发布单位】:美国材料与试验协会(US-ASTM)
【起草单位】:E07.06
【标准类型】:(Practice)
【标准水平】:()
【中文主题词】:
【英文主题词】:anglebeam;contactultrasonicmethod;Lambwaves;longitudinalwaves;nondestructiveexamination;Rayleighwaves;shearwaves;ultrasonicexamination;Ultrasonictesting;Anglebeamultrasonictesting;Calibration--ultrasonicanalysisinstrumentat
【摘要】:Anelectricalpulseisappliedtoapiezoelectrictransducerwhichconvertselectricaltomechanicalenergy.Intheangle-beamsearchunit,thepiezoelectricelementisgenerallyathicknessexpanderwhichcreatescompressionsandrarefactions.Thislongitudinal(compressional)wavetravelsthroughawedge(generallyaplastic).Theanglebetweentransducerfaceandtheexaminationfaceofthewedgeisequaltotheanglebetweenthenormal(perpendicular)totheexaminationsurfaceandtheincidentbeam.Fig.1showstheincidentanglex03D5;i,andtherefractedanglex03D5;r,oftheultrasonicbeam.Whentheexaminationfaceoftheangle-beamsearchunitiscoupledtoamaterial,ultrasonicwavesmaytravelinthematerial.AsshowninFig.2,theangleinthematerial(measuredfromthenormaltotheexaminationsurface)andmodeofvibrationaredependentonthewedgeangle,theultrasonicvelocityinthewedge,andthevelocityofthewaveintheexaminedmaterial.Whenthematerialisthickerthanafewwavelengths,thewavestravelinginthematerialmaybelongitudinalandshear,shearalone,shearandRayleigh,orRayleighalone.Totalreflectionmayoccurattheinterface.(RefertoFig.3.)Inthinmaterials(uptoafewwavelengthsthick),thewavesfromtheangle-beamsearchunittravelinginthematerialmaypropagateindifferentLambwavemodes.Allultrasonicmodesofvibrationmaybeusedforangle-beamexaminationofmaterial.Thematerialformsandtheprobableflawlocationsandorientationsdetermineselectionofbeamdirectionsandmodesofvibration.Theuseofanglebeamsandtheselectionoftheproperwavemodepresupposeaknowledgeofthegeometryoftheobject;theprobablelocation,size,orientation,andreflectivityoftheexpectedflaws;andthelawsofphysicsgoverningthepropagationofultrasonicwaves.Characteristicsoftheexaminationsystemusedandtheultrasonicpropertiesofthematerialbeingexaminedmustbeknownordetermined.Somematerials,becauseofuniquemicrostructure,aredifficulttoexamineusingultrasonics.Austeniticmaterial,particularlyweldmaterial,isoneexampleofthismaterialcondition.Cautionshouldbeexercisedwhenestablishingexaminationpracticesforthesetypematerials.Whileexaminationmaybepossible,sensitivitywillbeinferiortothatachievableonferriticmaterials.Whenexaminingmaterialswithuniquemicrostructures,empiricaltestingshouldbeperformedtoassurethattheexaminationwillachievethedesiredsensitivity.Thismaybeaccomplishedbyincorporatingknownreflectorsinamockupoftheweldorparttobeexamined.Angle-BeamLongitudinalWaves8212;AsshowninFig.4,angle-beamlongitudinalwaveswithrefractedanglesintherangefrom1to40x00B0;(wherecoexistingangle-beamshearwavesareweak,asshowninFig.3)maybeusedtodetectfatiguecracksinaxlesandshaftsfromtheendbydirectreflectionorbycornerreflection.AsshowninFig.5,withacrossed-beamdual-transducersearchunitconfiguration,angle-beamlongitudinalwavesmaybeusedtomeasurethicknessortodetectreflectorsparalleltotheexaminationsurface,suchaslaminations.AsshowninFig.6,reflectorswithamajorplaneatanangleupto40x00B0;withrespecttotheexaminationsurface,provideoptimumreflectiontoanangle-beamlongitudinalwavethatisnormaltotheplaneofthereflector.Angle-beamlongitudinalwavesintherangefrom45to85x00B0;becomeweakerastheangleincreases;atthesametime,thecoexistingangle-beamshearwavesbecomestronger.Equalamplitudeanglebeamsofapproximately55x00B0;