section 8 acoustic emission第8节的声发射

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1、9/8/98AC43.13-1BSECTION8.TAPTESTINGPar5-105Page5-539/8/98AC43.13-1B5-105.GENERAL.Taptestingiswidelyusedforaquickevaluationofanyaccessibleaircraftsurfacetodetectthepresenceofdelaminationordebonding.a.Thetaptestingprocedureconsistsoflightlytappingthesurfaceofthepartwithacoin,lightspecialhammerwitham

2、aximumof2 ounces(seefigure 522),oranyothersuitableobject.Theacousticresponseiscomparedwiththatofaknowngoodarea.b.A“flat”or“dead”responseisconsideredunacceptable.Theacousticresponseofagoodpartcanvarydramaticallywithchangesingeometry,inwhichcaseastandardofsomesortisrequired.Theentireareaofinterest

3、mustbetapped.Thesurfaceshouldbedryandfreeofoil,grease,anddirt.Taptestingislimitedtofindingrelativelyshallowdefectsinskinswithathicknesslessthan.080 inch.Inahoneycombstructure,forexample,thefarsidebondlinecannotbeevaluated,requiringtwosideaccessforacompleteinspection.Thismethodisportable,butnoreco

4、rdsareproduced.Theaccuracyofthistestdependsontheinspector’ssubjectiveinterpretationofthetestresponse;therefore,onlyqualifiedpersonnelshouldperformthistest.Par5-105Page5-539/8/98AC43.13-1BFigure5-22.Sampleofspecialtaphammer.5-106.¾5-111.[RESERVED.]SECTION9.ACOUSTICEMISSIONPar5-Page5-559/8/98AC43.1

5、3-1B5-112.GENERAL.AcousticEmissionisanNDItechniquethatinvolvestheplacingofacousticalemissionsensorsatvariouslocationsontheaircraftstructureandthenapplyingaloadorstress.Thelevelofstressappliedneednotreachgeneralyielding,nordoesthestressgenerallyneedtobeofaspecifictype.Bendingstresscanbeappliedtob

6、eamedstructures,torsionalstresscanbeappliedtorotaryshafts,thermalstressescanbeappliedwithheatlampsorblankets,andpressureinducedstresscanbeappliedtopressurecontainmentsystemssuchastheaircraftfuselage.Thematerialsemitsoundandstresswavesthattaketheformofultrasonicpulsesthatcanbepickedupbysensors.C

7、racksandareasofcorrosioninthestressedairframestructureemitsoundwaves(differentfrequenciesfordifferentsizedefects)whichareregisteredbythesensors.Theseacousticemissionburstscanbeusedbothtolocateflawsandtoevaluatet