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1、PlatewaveacousticemissionMichaelR.GormanAeronauticsandAstronautics,NavalPostgraduateSchool,Monterey,California93943(Received22February1990;revised20December1990;accepted7February1991)Platetheoryismoreeasilyappliedtotheanalysisofcompositelaminatesthanexactthree-dimensionalelasticitytheory.Un
2、derconditionssuchthatplatetheoryisapplicable,itissuggestedthatplatewavesareusefulforunderstandingacousticemission(AE)phenomena.Totestthisidea,pencilleadswerebrokenonaluminumplatesandcompositeplates,andtheresultingwavesweredetectedwithabroadbandultrasonictransducer.Boththefundamentalextensio
3、nalandflexuralmodeswereobserved.TheircharacteristicsaredescribedandtheimplicationsforAEsourcelocationarediscussedaswell.Severaltransducers,commonlyusedforacousticemissionmeasurements,arecomparedwithregardtotheirabilitytoreproducethecharacteristicshapesofplatewaves.Theirdifferentresponsessho
4、wwhysimilartestspecimensandtestconditionscanyielddisparateresults.PACSnumbers:43.40.Le,43.40.DxINTRODUCTIONble.Absolutemeasurementsofepicentermotioninaniso-6tropicplatehavebeencarriedoutforcalibrationpurposes,Formanyacousticemissionstudies,thetestspecimenisbutforpracticalacousticemissionmea
5、surements,thesensorgeometricallyplatelike.Thatis,thethicknessismuchpositionisoftendeterminedbytestfixturingorothercon-smallerthantheothertwodimensions.Consideringonlystraints,anditisusuallynotthecasethatthesourcepositionlinearlyelasticdisplacements,awayfromthesourcetheisknowninadvance.Theco
6、mputationsinvolvedforoffepi-propagatingwaveswillbegovernedbyLamb'shomoge-centermeasurementsareverytimeconsumingevenforiso-neousequation,thesolutionstowhicharecalledLambtropicmaterials.Thus,itmaybesometimebeforethisap-waves.Inthelimitwhenthewavelengthismuchlargerthanproachcanbefullyexploited
7、bythenondestructivetheplatethickness,asimplersetofgoverningequationsde-evaluation(NDE)practitionerworkingwithcomposites.rivedfromclassicalplatetheorycanbeusedtounderstandIncaseswherethewavemotioncanbedescribedbyplatethemotion.Inthis"thinplate"case,thewav
