超聲Lamb波具有傳播距離遠,對損傷敏感等優(yōu)點,常用于板狀結(jié)構(gòu)的無損評估（NDE）和結(jié)構(gòu)健康監(jiān)測（SHM）�；贚amb波的損傷定位成像方法的研究已成為SHM和NDE領(lǐng)域的研究熱點。然而,Lamb波的頻散特性使其在傳播時產(chǎn)生拉伸和失真,將影響有關(guān)損傷散射信息的渡越時間的提取,從而導(dǎo)致?lián)p傷定位和成像的不準(zhǔn)確;頻散效應(yīng)影響下入射信號和損傷散射信號的混疊也使得損傷特征信息的解讀更為困難;此外,現(xiàn)有基于時域分析的損傷成像方法難以有效利用激勵帶寬內(nèi)的全部頻率成分所包含的有效損傷信息,因此成像精度受限。為此,本文提出基于多頻段時域濾波的超聲Lamb波散射信號分析方法,利用小波分析將寬頻帶的激勵信號分解為多個頻散特征較弱的窄帶信號,進而構(gòu)建時域濾波窗函數(shù)以分離各窄帶信號中的損傷散射信息;分別對各窄帶信號實施頻域/空間延時疊加成像算法以獲取針對板結(jié)構(gòu)中的損傷成像;最終對各頻率分量的成像結(jié)果綜合分析（邏輯與）,以進一步提高損傷成像的精度和信噪比。建立預(yù)制損傷的鋁板中超聲Lamb波驅(qū)動,傳播及損傷散射的有限元數(shù)值模型,基于數(shù)值模擬數(shù)據(jù)驗證所提出多頻段時域濾波超聲信號處理方法和延時疊加損傷成像算法,指導(dǎo)建立... 

【文章頁數(shù)】：85 頁

【學(xué)位級別】：碩士

【文章目錄】：
摘要
Abstract
LIST OF SYMBOLS
CHAPTER1 INTRODUCTION
    1.1 RESEARCH BACKGROUND
    1.2 RESEARCH OF ULTRASONIC GUIDED WAVE BASED ARRAY IMAGING TECHNOLOGY
        1.2.1 LAMB WAVE DAMAGE IMAGING METHOD
            1.2.1.1 Time reversal imaging
            1.2.1.2 Migration imaging method
            1.2.1.3 Elliptical damage positioning method
            1.2.1.4 Array beamforming damage imaging method
    1.3 ULTRASONIC SIGNAL PROCESSING METHOD
        1.3.1 TIME DOMAIN ANALYSIS
        1.3.2 FREQUENCY WAVENUMBER DOMAIN ANALYSIS
        1.3.3 INTEGRATED TIME DOMAIN-FREQUENCY DOMAIN ANALYSIS
    1.4 RESEARCH OBJECTIVES AND NOVELTY
CHAPTER2 ULTRASONIC LAMB WAVE THEORY
    2.1 ULTRASONIC LAMB WAVE
        2.1.1 LAMB WAVE FORMATION MECHANISM
        2.1.2 LAMB WAVE PROPAGATION CHARACTERISTICS
        2.1.3 PHASE VELOCITY AND GROUP VELOCITY
        2.1.4 DICHOTOMY METHOD TO SOLVE THE DISPERSION CURVES
    2.2 ULTRASONIC SIGNAL PROCESSING METHOD
        2.2.1 FREQUENCY WAVENUMBER DOMAIN ANALYSIS
        2.2.2 WAVELET TRANSFORM
            2.2.2.1 Wavelet basis selection
        2.2.3 FREQUENCY BANDS AND TEMPORAL FILTERING METHOD
    2.3 SUMMARY OF THIS CHAPTER
CHAPTER3 ULTRASONIC LAMB WAVE ARRAY BEAMFORMING AND DELAY AND SUM DAMAGE IMAGING METHOD
    3.1 DELAY AND SUM DAMAGE IMAGING METHOD
        3.1.1 TIME/PHASE DELAY AND SUM DAMAGE IMAGING METHOD
        3.1.2 SPATIAL DELAY AND SUM DAMAGE IMAGING METHOD
    3.2 LOGICAL OPERATIONS
    3.3 RELATIVE ERROR
    3.4 SUMMARY OF THIS CHAPTER
CHAPTER4 NUMERICAL STUDY ON DAMAGE IMAGING OF AN ALUMINUM
    4.1 NUMERICAL SIMULATION PARAMETER SETTING AND MODEL ESTABLISHMENT
        4.1.1 TIME STEP SIZE AND GRID SIZE
        4.1.2 BOUNDARY CONDITIONS AND MODEL LOADS
        4.1.3 WAVE FIELD DIAGRAM OF ULTRASONIC LAMB WAVE AT DIFFERENT TIMES
    4.2 SIGNAL EXTRACTION AND DAMAGE IMAGING
        4.2.1 MODEL ANALYSIS
        4.2.2 DAMAGE IMAGING ANALYSIS
    4.3 SUMMARY
CHAPTER5 EXPERIMENTAL STUDY ON DAMAGE IMAGING OF AN ALUMINUM PLATE
    5.1 ULTRASONIC LAMB WAVE DAMAGE DETECTION EXPERIMENTAL PLATFORM
        5.1.1 EXPERIMENTAL TEST PIECES AND DEVICES
        5.1.2 POINT PLACEMENT IN THE EXPERIMENT
    5.2 EXPERIMENTAL DAMAGE DETECTION PROCESS AND RESULTS
        5.2.1 DAMAGE SCATTER SIGNAL EXTRACTION
        5.2.2 ANALYSIS OF IMAGING RESULTS
    5.3 CONCLUSION
CHAPTER6 CONCLUSION
REFERENCES
ACKNOWLEDGEMENTS
MAJOR PAPERS PUBLISHED DURING THE MASTER'S DEGREE


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