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1、ABSTRACTAsanewmotionNondestructiveTesting(NDT)technique,acousticemissiontechnologydetectsthesignalfromactivedefectitselfofthetestpiece,itispossibletoachievereal-timemonitoringofthedefect,anditcandeterminetheseverityofthedefectandtheremaininglifeofthedevice.Asanon-contactultrasonictestingte
2、chniqueinthedetectionofmetallicmaterials,Electromagneticultrasonictransducer(EMAT)technologyhavebeenwidelyused,andespeciallyachievedverygoodresultsinthesurfacecrackdetection.Firstofall,basedonthestudyofgenerateprincipleofEMAEandUltrasonicsignal.takingsignalcharacteristicsintoconsideration,
3、thispaperdesignstheweakacousticemissionsignalloadingUltrasonicsignalexperimentstodetecttheloadingconditions,andthesignalsmakeFouriertransformandwavelettransform.WecanclearlyseetwosignalsofdifferentfrequenciesinthefrequencydomainandWeextractanddisplaythefeaturesegmentsignalafterwavelettrans
4、form,sothattwodifferentfrequencysignalisseparated.Secondly,basedonmasteringthesignalofwavelettransform.Thispaperdesignvibrationfatigueinthemetalplateandloadingultrasonicsignalexperimenttocapturefaintcrackleofacousticemissionsignals.AfterthresholdingandFFTtransform,theapplicationofacousticn
5、onlineardetectiontheory,Wecanseparateequipmentofnonlineareffectsandharmonicacousticsignals,andultimatelydeterminegeneratingacousticemissionsignals.Thiswayprovideamethodforthepreventionofearlyfatiguedamageinmetalplate.Atlast,basedontheelectromagneticultrasonicnondestructivetesting,Thispaper
6、designelectromagneticultrasonicexperimentsinthemetalplateswithorwithoutdefectsandinthemetalplatesofdifferentdefect.Wedeterminewhetherthedefectsinthemetalplate.intime-domainanalysisandfrequency-domainanalysis,andinitiallyidentifieddefecttypesandsizes.Theresearchhaslaidagoodfoundationforthen
7、on-destructivetestingdefectdetectionandquantitativedeterminationofdefectinlargemetalplateKEYWORDS:Acousticemission,Electromagneticultrasonictransducer,wavelettransform,Vibrationfatigue,目录第一章绪论-1-1.1课题背景-1-1.2研究意义-1-1.3国内外研究现状-2-1.3.1声发射国内外研究现状-2-1.3.2电磁超声检测技术研
