本文選題：導(dǎo)波 + 無損檢測(cè)�。� 參考：《上海交通大學(xué)》2014年博士論文

【摘要】：傳統(tǒng)的導(dǎo)波無損檢測(cè)是利用傳感器網(wǎng)絡(luò)采集導(dǎo)波信號(hào)，再經(jīng)過復(fù)雜的一維信號(hào)處理方法提取損傷特征、識(shí)別損傷參數(shù)。這種檢測(cè)形式對(duì)傳感器的位置、網(wǎng)絡(luò)布置形式及信號(hào)處理方法均提出了較高的要求，很難實(shí)現(xiàn)工業(yè)化檢測(cè)。 散斑干涉術(shù)是上世紀(jì)六十年代逐漸興起的一種光學(xué)測(cè)量技術(shù)，它具有高精度、高靈敏度、全場(chǎng)、實(shí)時(shí)性、結(jié)構(gòu)簡單、非接觸等特點(diǎn)，廣泛應(yīng)用于變形測(cè)量、應(yīng)力應(yīng)變、振動(dòng)分析、無損檢測(cè)等領(lǐng)域。論文提出以散斑干涉技術(shù)作為導(dǎo)波信號(hào)的采集裝置，輸出散斑條紋信號(hào)，快速直觀地提取結(jié)構(gòu)的全場(chǎng)信息。該技術(shù)可以取代現(xiàn)有傳感器網(wǎng)絡(luò)，形成另外一種形式的導(dǎo)波無損檢測(cè)系統(tǒng)。但是，強(qiáng)烈的散斑噪聲導(dǎo)致了較低的可見度和空間分辨率，大大降低了條紋信號(hào)的使用效果。 散斑噪聲可分為三類：隨機(jī)散斑噪聲、非一致背景光、光強(qiáng)調(diào)制。傳統(tǒng)的散斑條紋信號(hào)的質(zhì)量增強(qiáng)方法可以分為兩類：信號(hào)濾波法和相位解調(diào)法。這兩類方法都存在各自的弊端，適用范圍受限。信號(hào)濾波法，多為通用的圖像處理技術(shù)，并未考慮條紋信號(hào)的特點(diǎn)，只是針對(duì)隨機(jī)散斑噪聲和非一致背景光，因此在某些情況下的質(zhì)量增強(qiáng)效果并不理想；相位解調(diào)法，充分考慮了條紋信號(hào)的特點(diǎn)，試圖在噪聲和背景光的干擾下直接進(jìn)行相位解調(diào)，然而即使解調(diào)方法的魯棒性再強(qiáng)，在某些情況下，依舊無法擺脫噪聲的干擾。 論文綜合考慮了多種不利因素的影響，結(jié)合信號(hào)濾波和相位解調(diào)，提出了一種散斑條紋信號(hào)的三層質(zhì)量增強(qiáng)方法： 第一，論文提出了信號(hào)分解與特征分類方法。首先，引入了快速自適應(yīng)二維經(jīng)驗(yàn)?zāi)B(tài)分解，并提出碟形結(jié)構(gòu)元素和自適應(yīng)鄰域窗的改進(jìn)；其次，提出了基于二維固有模態(tài)函數(shù)能量估計(jì)的特征分類方法。前者可將散斑條紋信號(hào)按空間頻率從高到低進(jìn)行分解，形成若干局部窄帶的平穩(wěn)子信號(hào)；后者具有自動(dòng)識(shí)別功能，實(shí)現(xiàn)了子信號(hào)的特征分類。第一層質(zhì)量增強(qiáng)可以消除高頻散斑噪聲和直流背景光。 第二，論文提出了基于希爾伯特螺旋變換的第二層質(zhì)量增強(qiáng)方法。首先，以方向角和二維符號(hào)函數(shù)為基礎(chǔ)，提出了五種可行的二維希爾伯特變換形式，其中以希爾伯特螺旋為最優(yōu)；其次，提出了幅值分布閾值法，該方法判定低于閾值的區(qū)域?yàn)樵肼暎缓笠跃哂凶赃m應(yīng)窗口的均值濾波器進(jìn)行去噪。第二層可以消除中頻噪聲。 第三，論文提出了一種修正正則化相位追蹤方法。引入了傳統(tǒng)的正則化相位追蹤方法，并提出了四點(diǎn)修正，其中：能量函數(shù)中加入了高斯窗函數(shù)，并對(duì)局部條紋模型分別作了線性和二次展開，從而解決了歸一化處理的難題；提出以迭代次數(shù)作為質(zhì)量譜引導(dǎo)解調(diào)過程；提出具有自適應(yīng)窗口的高斯窗函數(shù)；提出使用一種收斂快速的優(yōu)化方法——Levenberg-Marquardt。修正方法的解調(diào)范圍更廣，解調(diào)效果更好。第三層質(zhì)量增強(qiáng)可以降低光強(qiáng)調(diào)制變量的影響。 最后，論文研究了散斑干涉測(cè)量技術(shù)及其信號(hào)質(zhì)量增強(qiáng)方法在導(dǎo)波無損檢測(cè)中的應(yīng)用，實(shí)現(xiàn)了薄板類機(jī)械構(gòu)件的損傷檢測(cè)，系統(tǒng)包括三部分：Lamb波波場(chǎng)的激發(fā)、Lamb波波場(chǎng)的檢測(cè)以及散斑條紋信號(hào)的質(zhì)量增強(qiáng)。為簡化波場(chǎng)，利用可窄帶激發(fā)的棱柱耦合塊法產(chǎn)生了單模式超聲波波場(chǎng)；為捕捉波場(chǎng)的瞬態(tài)信息，設(shè)計(jì)了雙脈沖數(shù)字散斑干涉測(cè)量系統(tǒng)，可每隔3微秒記錄1個(gè)散斑條紋信號(hào)；最后使用三層質(zhì)量增強(qiáng)方法，提高散斑條紋信號(hào)的可見度和空間分辨率，達(dá)到無損檢測(cè)的目的。另外，，計(jì)算機(jī)和同步電子作為同步裝置，控制整個(gè)無損檢測(cè)系統(tǒng)的工作時(shí)序。
[Abstract]:Traditional guided wave nondestructive testing uses sensor networks to collect guided wave signals, and then extracts damage characteristics and identification of damage parameters through complex one-dimensional signal processing methods. This detection form puts forward higher requirements for sensor location, network layout and signal processing methods. It is difficult to realize industrial detection.
Speckle interferometry is a kind of optical measurement technology which rose gradually in the 60s of last century. It has the characteristics of high precision, high sensitivity, full field, real time, simple structure, non contact and so on. It is widely used in the fields of deformation measurement, stress strain, vibration analysis, nondestructive testing and so on. This paper proposes the speckle interference technique as the acquisition and assembly of the guided wave signal. It can quickly and intuitively extract the full field information of the structure. This technique can replace the existing sensor network and form another form of guided wave nondestructive testing system. However, the strong speckle noise leads to lower visibility and spatial resolution, and greatly reduces the use effect of the stripe signal.
Speckle noise can be divided into three categories: random speckle noise, non consistent background light and intensity modulation. The quality enhancement methods of traditional speckle stripe signals can be divided into two categories: signal filtering and phase demodulation. These two methods all have their own disadvantages, and the application range is limited. Considering the characteristics of the stripe signal, only for random speckle noise and non coherent background light, the quality enhancement effect is not ideal in some cases. The phase demodulation method takes full consideration of the characteristics of the stripe signal and tries to demodulate the phase directly under the interference of the noise and the background light, but even if the robustness of the demodulation method is strong again In some cases, it is still unable to get rid of noise interference.
Considering the influence of many unfavorable factors, combining the signal filtering and phase demodulation, a three layer quality enhancement method of speckle fringe signal is proposed.
Firstly, the method of signal decomposition and feature classification is proposed. First, the fast adaptive two-dimensional empirical mode decomposition is introduced, and the improvement of the dish structure element and adaptive neighborhood window is proposed. Secondly, a feature classification method based on the energy estimation of the two-dimensional intrinsic modal function is proposed. The former can make the speckle stripe signal in space frequency. From high to low to decompose to form a number of local narrow band stationary signal; the latter has automatic recognition function, and realizes the feature classification of the subsignal. The first layer quality enhancement can eliminate the high frequency speckle noise and the DC background light.
Second, the paper proposes a second layer quality enhancement method based on Hilbert spiral transformation. First, based on the direction angle and the two-dimensional symbolic function, five feasible two-dimensional Hilbert transform forms are proposed, in which the Hilbert spiral is the best. Secondly, the amplitude distribution threshold method is proposed, which determines the area below the threshold value. The domain is noise and then denoised by means of adaptive window averaging filter. The second level can eliminate intermediate frequency noise.
Third, a modified regularized phase tracing method is proposed. The traditional regularization phase tracing method is introduced, and the four point correction is proposed, in which the Gauss window function is added to the energy function, and the linear and two expansion of the local fringe model are made respectively, and the problem of normalization is solved. The number of times is used as the quality spectrum to guide the demodulation process; the Gauss window function with adaptive window is proposed, and a fast convergence method is proposed - the Levenberg-Marquardt. correction method has a wider demodulation range and better demodulation effect. The third layer quality enhancement can reduce the influence of the intensity modulation variable.
Finally, the application of speckle interferometry and signal quality enhancement in guided wave nondestructive testing is studied. The damage detection of thin plate mechanical components is realized. The system includes three parts: the excitation of the Lamb wave field, the detection of the Lamb wave field and the quality enhancement of the speckle stripe signal. A single mode ultrasonic wave field is produced by the prism coupled block method. In order to capture the transient information of the wave field, a dual pulse digital speckle interferometry system is designed, which can record 1 speckle stripe signals every 3 microseconds. Finally, the visibility and spatial resolution of the speckle stripe signal are improved by using the three layer quality enhancement method, and the nondestructive testing is achieved. In addition, computers and synchronous electronic devices are used as synchronous devices to control the working sequence of the whole NDT system.

【學(xué)位授予單位】：上海交通大學(xué)
【學(xué)位級(jí)別】：博士
【學(xué)位授予年份】：2014
【分類號(hào)】：TN911.7

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