简介：Tostudythepossibilityofdetectingthecrossingchannelbyusingatraditionalloggingtool,acousticfieldgeneratedbyamonopolesourceinacasedwellwithacrossingchannelofvariousanglesissimulatedby2.5-DFiniteDifferenceMethod(FDM).Snapshotsofnormalstressandsynthetictime-domainwaveformsaredisplayed.Thetwo-dimensionalspectruminwave-numberandfrequencydomainsisalsocalculated,wheretheinfluenceofthechannelisclearerthanthatinthewaveforms.Numericalstudydemonstratedthatacrossingchannelcanbedetectedandsizedifitsangleisgreaterthan30degree,andlargerspacingandlowerfrequencysourcearefavorabletodetectandsizethecrossingchannel.

简介：Aresidual-stressprofilealongthethicknessofanaluminumalloysheetisdeterminedbylaser-ultrasonictechnique.SurfaceacousticwavesaregeneratedbyaNd:YAGpulselaseranddetectedbyaHeterodyneinterferometeronalateralfreesurfaceofthesheet.Thedistributionofresidualstressisdeterminedbymeasuringtherelativevariationofthewavevelocitiesatdifferentlocationofthesamplealongitsthickness.Thistechniqueisvalidatedbythreedifferentresidualstressprofilesobtainedexperimentally.

简介：Currentstudiesareaimingatmonitoringcorrosiondamageofaircraftmainstructuresbyusingacousticemission(AE)techniqueandatsupplyingusefuldatafordeterminingcalendarlifeoftheaircraft.ThecharacteristicsofAEsignalsproducedduringacceleratingcorrosionprocessaredescribed,andmethodsforevaluatingcorrosiondamagesanddeterminingremaininglifeofmainstructuresofaircraftusingAEtestingareoutlined.ExperimentalresultshaveshownthatAEtechniquecandetectcorrosiondamageofaluminumalloymuchearlierthanconventionalnon-destructivetestingmeans,suchasultrasonictestingandeddycurrenttesting.RelationshipbetweencorrosiondamageandAEparameterswasobtainedthroughinvestigatingcorrosiondamageextentandchangesofAEsignalsduringacceleratingcorrosiontest,andshowingthatAEtechniquecanbeusedtodetectearlycorrosion,investigatingcorrosiondevelopingtrend,andinmonitoringandevaluatingcorrosiondamages.

简介：Thepartlyspecularreflectionandpartlydiffusionreflectionmodelisaconvenientwaytoexpressthephenomenaofsurfacesoundenergyscatteringinroomacoustics.Soundenergydiffusioncoefficientbecomesakeyfactortostudysurfacescattering.Buttherehavebeenveryfewmethodsfordeterminingtheaveragesoundenergydiffusioncoefficient.Vorliinderproposedsuchaneasyonebasedonthecorrelationprinciple.However,hismethodignoredthecorrelationfromdirectsound,inwhichdefectispresent.Anewapproximatemethodforcalculatingsoundenergydiffusioncoefficient,includingdirectsoundandfirststrongreflectionsispresented.Therefore,Vorlaender''''''''sdefectisovercome.Inaddition,withtheaidofdigitalmeasuringtechnology,arelevantmeasuringsystemwasdeveloped.TheexperimentresultshowsthatthemethodisimprovedthanVorlaender's.

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