1、Y1113928猷5薹舞坤手簍夫肇學(xué)校代碼：10488學(xué)號：05104059碩士學(xué)位論文題目金屬薄板的超聲導(dǎo)波無損檢測專業(yè)研究方向姓名導(dǎo)師控制理論與控制工程超聲波無損檢測及其信號處理?xiàng)铨R郝國法教授定稿日期：2007年11月10日第Ⅱ頁武漢科技大學(xué)碩士學(xué)位論文AbstractItisverydifficulttotestthinplatesnondestructivelybyconventionalultrasonicmethodsbut

2、Lambwavetechniquesarerapidandefficientfornondestructivetestingoflargeplate—sh印edstructureTheinteractionbetweenLambwavesanddefectswerecomplex，duetoabsenceoftheknowledge，therearestillalotofinconsistentviewpointsandunresolv

3、edproblemsforLambwavetechniquesInthisresearchtheLambwavesignalsobtainedinthedefectfreeplateanddefectedones，respectivelyareanalyzedintime—frequencydomain，onthebasisofanalyzingtheLambmodesandtheLambmodeconversion，character

4、isticparametersareextractedtocharacterizeandevaluatethedefects；besides，therelationshipbetweenthevibrationdisplacementandthesensitivityofLambmodeisresearchedSlots州tlldifferentdepthandlengtharemadeinmetalsheetofSTl2Inthese

5、metalsheetsLambwavesareexcitedandsampledThedigitalLambwavesignalsareanalyzedandtheresultshows：thereisagoodcorrespondingrelationshipbetweenthedefectsize(thedepthorthelengthoftheslots)andthechangeoftheaverageinstantaneousf

6、requenciesofthesignals；themainLambwavemode，SI，WasisolatedintimedomainbytheFFrband—passfilteringandthenthecentroidofitsenvelopeWasextracted，goodcorrelationofthecentroidpositionwiththeslotdepthWasobtained；thechangeofLambwa

7、ve’Sshapefactorarecorrelativelinearly岍mthedefectsizeOnthebasisoftheEMDprocessing，theshapefactorwouldbeofgreatpromisefordetectingandevaluatingthesliglltdefectAlso，thereisa900dcorrespondingrelationshipbetweenthedefectsizes

8、andthefrequencycentersofsignalsTherelationshipbetweenthevibrationdisplacementandthesensitivityofLambwavetestingisresearchedTheresultshows：thereisagoodcorrespondingrelationshipbetweenthevibrationdisplacementandtheseusitiv

9、ityoftesting，whichprovidesguidanceforthechoiceofthesensitiveLambmodes，andaconvictingexperimentalsupportforthecurrentviewpointwhichiSstilldisputedOILKeywords：Guidedwave；Nondestructivetesting；Lambwave；timefrequencyanalysis

10、ThisworkisfinanciallysupportedbytheHubeiProvincialNaturalScienceFoundation(thecontractnumberis2004ABA019)，theOfficeoftheHubeiProvincialEducation(thecontractnumberis2004D009)，andNingboNaturalScienceFoundation(thecontractn