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1、Ultrasonics44(2006)e1139–e1143www.elsevier.com/locate/ultrasPropagationphenomenaofwidebandguidedwavesinabendedpipea,*abbHideoNishino,KenichiYoshida,HideoCho,MikioTakemotoaInstituteofTechnologyandScience,TheUniversityofTokushima,Minami-Josanjima2-1,TokushimaCity,Tokushima770-8506,Ja
2、panbFacultyofScienceandEngineering,AoyamaGakuinUniversity,Fuchinobe5-10-1,SagamiharaCity,Kanagawa229-8558,JapanAvailableonline8June2006AbstractUltrasonicguidedwavesinpipeshavebeenanticipatedasarapidscreeningtechniqueforpipeinspectionbecauseoftheirlong-rangepropagationduetolowenergy
3、leakage.Inthispaper,thepropagationphenomenaofguidedwavesinabendedpipewereinvestigatedusingawidebandlaserultrasonicsystem.Thelaserultrasonicsystem,togetherwithwavelettransformation,isapowerfultoolforobservingthedispersivephenomenaintrinsictoguidedwaves.Bendedstainlesssteel(SUS304)pi
4、peswith6-mmouterdiameterand1-mmwallthicknesswereusedintheexperiments.Thebendinganglesofthepipesweresetto0°(straightpipe),10°,30°,60°and90°.Theradiusofthebendwas12.5mminallthepipes.AQ-switchedNd:YAGlaserwasemployedtogeneratetheguidedwaves.Thegeneratedguidedwavesweredetectedwithahete
5、rodyneinterferometer.Theobtainedtime-domainsignalsandtheirwaveletcoef-ficientsindicatedthefollowingtwoconclusions:(1)TheamplitudeoftheF(1,1)modeconvertedfromtheL(0,1)modeincreasedwiththeincreaseofthebendingangle.(2)ModeconversionsfromtheL(0,1)toF(1,1)modesandviceversawereclearlyobse
6、rvedinthelow-frequencyrangeuptoaround200kHz.Ó2006ElsevierB.V.Allrightsreserved.Keywords:Guidedwave;Pipeinspection1.IntroductionphenomenaandinteractionbetweentheguidedwavesandvariouskindsofdefectshavebeeninvestigatedinUltrasonicguidedwaves[1]inpipeshavebeenantici-straightpipes;howev
7、er,inactualinspections,notonlypatedasapowerfulandeffectivetoolforlong-rangestraightpipesbutalsoothercomplexpipestructures,e.g.inspectionsofpipesbecauseoftheirabilityforlong-rangebendedpipes,reducedpipes,flanges,andsupportmounts,propagationandtheirintrinsiccharacteroflowenergydis-need
8、tobeinspectedforreliabilit
