本文選題：結(jié)構(gòu)健康監(jiān)測(cè)　切入點(diǎn)：Lamb波成像　出處：《中國(guó)科學(xué)技術(shù)大學(xué)》2017年碩士論文

【摘要】：在平板結(jié)構(gòu)的健康監(jiān)測(cè)領(lǐng)域,Lamb波由于具有傳播范圍廣,對(duì)缺陷敏感等優(yōu)點(diǎn),被廣泛使用。其中,Lamb波成像技術(shù)不僅能精確定位損傷位置,還能評(píng)估損傷程度,是Lamb波應(yīng)用的研究熱點(diǎn)。本文從Lamb波在應(yīng)用中的局限性出發(fā),提出了改進(jìn)的模型和方法,旨在擴(kuò)展Lamb波成像技術(shù)的應(yīng)用范圍,提高成像質(zhì)量。本文首先對(duì)脈沖振聲調(diào)制機(jī)理的做了初步研究,為后續(xù)的Lamb波振聲調(diào)制效應(yīng)提供理論指導(dǎo)。在此基礎(chǔ)上,本文提出了基于雙穩(wěn)模型的Lamb波振聲調(diào)制成像模型。該模型利用Lamb波的振聲調(diào)制效應(yīng),可以實(shí)現(xiàn)Lamb波的無(wú)基準(zhǔn)成像,同時(shí)利用雙穩(wěn)結(jié)構(gòu)的振動(dòng)特性,有效地提高板在非共振頻率區(qū)的振幅,加強(qiáng)了調(diào)制現(xiàn)象。通過(guò)實(shí)驗(yàn)對(duì)比,發(fā)現(xiàn)該模型比傳統(tǒng)模型在非共振頻率區(qū)成像準(zhǔn)確度更高,有效地?cái)U(kuò)展了 Lamb波振聲調(diào)制成像方法的操作帶寬。針對(duì)超聲導(dǎo)波成像的頻散補(bǔ)償方法進(jìn)行研究,本文提出了基于時(shí)頻延時(shí)的頻散補(bǔ)償方法。傳統(tǒng)頻散補(bǔ)償方法在結(jié)構(gòu)材料屬性未知下需要通過(guò)幅值計(jì)算和額外實(shí)驗(yàn)計(jì)算波數(shù)曲線,本文通過(guò)提出的新線性映射方法,利用窄帶信號(hào)時(shí)延脊線估計(jì)映射參數(shù),實(shí)現(xiàn)頻散補(bǔ)償。該方法相較于傳統(tǒng)方法計(jì)算簡(jiǎn)單,適用性廣。仿真和實(shí)驗(yàn)結(jié)果驗(yàn)證了該方法的有效性,并且展示了該方法可以有效地提高Lamb波成像的分辨率。通過(guò)以上研究,有效地改善了 Lamb波在振動(dòng)系統(tǒng)和頻散狀態(tài)下的成像質(zhì)量,擴(kuò)展了 Lamb波在無(wú)基準(zhǔn)監(jiān)測(cè)、長(zhǎng)距離監(jiān)測(cè)和多故障檢測(cè)中的應(yīng)用。
[Abstract]:Lamb waves are widely used in the health monitoring field of flat structures because of their wide range of propagation and sensitivity to defects.Lamb wave imaging can not only accurately locate the location of damage, but also can evaluate the degree of damage. It is a research hotspot in the application of Lamb wave.Based on the limitation of Lamb wave in application, an improved model and method are proposed in this paper. The purpose of this paper is to extend the application of Lamb wave imaging technology and improve the imaging quality.In this paper, the mechanism of pulse vibration-acoustic modulation is studied in order to provide theoretical guidance for the subsequent Lamb wave vibration-acoustic modulation effect.On this basis, a bistable model of Lamb wave vibration-acoustic modulation image is presented in this paper.In this model, the vibration-acoustic modulation effect of Lamb wave can be used to realize the non-reference imaging of Lamb wave. At the same time, the vibration characteristics of bistable structure can be used to effectively increase the amplitude of plate in the non-resonance frequency region and strengthen the modulation phenomenon.The experimental results show that the proposed model is more accurate than the traditional model in the non-resonance frequency region and extends the bandwidth of the vibroacoustic modulation imaging method of Lamb wave effectively.In this paper, the dispersion compensation method based on time-frequency delay is proposed for ultrasonic guided wave imaging.The traditional dispersion compensation method needs to calculate the wavenumber curve through amplitude calculation and extra experiment when the properties of structural materials are unknown. In this paper, we use the new linear mapping method to estimate the mapping parameters of narrow band signal time-delay ridge line to realize dispersion compensation.Compared with the traditional method, this method is simpler and more applicable.The simulation and experimental results show that the proposed method is effective in improving the resolution of Lamb wave imaging.Through the above research, the imaging quality of Lamb wave in vibration system and dispersion state is improved effectively, and the application of Lamb wave in non-reference monitoring, long-distance monitoring and multi-fault detection is extended.
【學(xué)位授予單位】：中國(guó)科學(xué)技術(shù)大學(xué)
【學(xué)位級(jí)別】：碩士
【學(xué)位授予年份】：2017
【分類號(hào)】：TP391.41;TB559

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