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Lamb波时间反转分解损伤识别方法研究.docx

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Lamb波时间反转分解损伤识别方法研究 1.Introduction Lambwavesarewidelyusedinnon-destructivetesting(NDT)andstructuralhealthmonitoring(SHM)ofvariousstructuressuchaspipelines,plates,andcompositematerials.Lambwavescanpropagatelongdistanceswithlowattenuation,andcandetectdefectssuchascracks,delaminations,andvoids.However,itisstillachallengetoaccuratelyidentifyandlocatedefectsinthesestructuresusingLambwavesduetothecomplexityofthewavepropagation,theinterferenceofwavemodes,andthenoiseinthemeasurementdata.Inthispaper,weproposeanovelmethodforLambwavetimereversaldecomposition(TRD)fordamageidentification. 2.LambwaveTRDmethod TheLambwaveTRDmethodisbasedontheprincipleoftimereversalsymmetry.Accordingtothisprinciple,whenaLambwavepropagatesthroughastructurewithdefects,thewavefieldwillchangeduetothescatteringandreflectionofthewavebythedefects.However,ifthetime-reversedwavefieldisgeneratedbyreversingthetimeaxisofthemeasurementdata,thetime-reversedwavefieldwillreconstructaconvergingwavethatexactlyretracesthepathoftheoriginalwaveandconvergesatthelocationofthedefect.Therefore,thedamagelocationandcharacteristicscanberetrievedfromthefocusedwavethroughmatchedfiltering,signalprocessing,andimagingtechniques. TheLambwaveTRDmethodconsistsoffoursteps:dataacquisition,timereversal,decomposition,andimaging.Inthedataacquisitionstep,apiezoelectrictransducerisusedtogenerateandreceiveLambwavesatmultiplelocationsonthestructuresurface.Inthetimereversalstep,thereceivedwavesignalsaretime-reversedandsentbacktothestructure.Inthedecompositionstep,thetime-reversedwavefieldisdecomposedintoasetofLambwavemodesusingasignalprocessingalgorithmsuchassingularvaluedecomposition(SVD).Intheimagingstep,theLambwavemodesareusedtoreconstructthefocusedwavefieldusingabackpropagationalgorithmsuchasKirchhoffmigration.Thefocusedwavefieldcontainstheinformationaboutthedamagelocation,size,andseverity,whichcanbevisualizedandanalyzedfordamageidentification. 3.Numericalsimulationandexperimentalvalidation TovalidatetheLambwaveTRDmethod,numericalsimulatio