A Baseline-Free Defect Imaging Technique in Plates Using Time Reversal of Lamb Waves

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1、CHIN.PHYS.LETT.Vol.28,No.6(2011)064301ABaseline-FreeDefectImagingTechniqueinPlatesUsingTimeReversalofLambWaves*HyunjoJeong**,SungjongCho,WeiWeiDivisionofMechanicalandAutomotiveEngineering,WonkwangUniversity,Iksan,Jeonbuk570-749,Korea(Received6January2011)Wepresentananal

2、yticalinvestigationforabaseline-freeimagingofadefectinplate-likestructuresusingthetime-reversalofLambwaves.Wefirstconsidertheflexuralwave(?0mode)propagationinaplatecontainingadefect,andreceptionandtimereversalprocessoftheoutputsignalatthereceiver.Thereceivedoutputsignal

3、isthencomposedoftwoparts:adirectlypropagatedwaveandascatteredwavefromthedefect.Thetimereversalofthesewavesrecoverstheoriginalinputsignal,andproducestwoadditionalsidebandsthatcontainthetime-of-flightinformationonthedefectlocation.Oneoftheside-bandsignalsisthenextractedas

4、apuredefectsignal.Adefectlocalizationimageisthenconstructedfromabeamformingtechniquebasedonthetime-frequencyanalysisofthesidebandsignalforeachtransducerpairinanetworkofsensors.Thesimulationresultsshowthattheproposedschemeenablestheaccurate,baseline-freeimagingofadefect.

5、PACS:43.35.Cg,43.60.Tj,43.60.LqDOI:10.1088/0256-307X/28/6/064301MostoftheLambwave-baseddamagedetectionage/defectdetectionandlocalizationwhereaflawistechniquesoftenrequireapastbaselinedata.Thebeinginterrogatedinapitch-catcharrangementusingscatteredsignalfromadamageisobta

6、inedusingtheanetworkofpiezoelectric(PZT)transducers.baselinesubtractiontoconstructthedamagelocaliza-[1,2]tionimage.Atimereversal(TR)processcanbeDefectDefect(a)(b)establishedasabaseline-freemethodfordamagede-ScatteredtectioninSHMapplications.[3]Initialapplicationsforwave

7、Path2Path2thetimereversalmethodinflawordamagedetectionwereaimedatincreasingLambwaveresolutionbyus-APath1BAPath1BDirectingtimereversalmirrors.[4]TheeffectofdispersionwaveonthetimereversalanalysisofLambwaveswasfirstFig.2.FlexuralwavepropagationinaplatecontainingstudiedbyW

8、angetal.[5]byintroducingthetimere-adefect:(a)forwardpropagationfromsensorA,and(b)versaloperatorintotheLambwave