【摘要】：超聲Lamb波具有傳播距離遠(yuǎn)、衰減小等特點(diǎn),已被廣泛應(yīng)用于大型薄板結(jié)構(gòu)的無損檢測。目前的研究可以實(shí)現(xiàn)薄板中裂紋的二維成像,提供了金屬薄板裂紋的可視化檢測方法,然而薄板中裂紋的深度信息還未能實(shí)現(xiàn)有效的檢測,本研究將此問題作為工作重點(diǎn),以工程實(shí)際中廣泛應(yīng)用的鋁制薄板為研究對象,將時(shí)間反轉(zhuǎn)方法、分?jǐn)?shù)階微分方法與超聲Lamb波無損檢測相結(jié)合,開展Lamb波信號重構(gòu)、信號增強(qiáng)、信號去噪與裂紋深度定位等相關(guān)研究。本文主要研究內(nèi)容如下:分析了 Lamb波的傳播規(guī)律和頻散特性。根據(jù)Lamb波的頻率方程、群速度和相速度的關(guān)系,利用MATLAB研究了鋁制薄板中Lamb波的群速度和相速度的多模態(tài)特性,并利用短時(shí)傅立葉變換對鋁制薄板中的Lamb波檢測信號進(jìn)行模態(tài)識別。研究了時(shí)間反轉(zhuǎn)方法及Lamb波的時(shí)間反轉(zhuǎn)特性,將接收的多模態(tài)信號經(jīng)過時(shí)間反轉(zhuǎn)重構(gòu)為單模態(tài)信號,并對含裂紋薄板中Lamb波的傳播進(jìn)行有限元建模仿真。研究了一種基于分?jǐn)?shù)階微分的去噪方法。為降低噪聲對Lamb波檢測信號的影響,提出一種基于分?jǐn)?shù)階微分的去噪方法,該方法首先利用分?jǐn)?shù)階微分對含噪Lamb波信號的幅值譜進(jìn)行各階微分,識別出頻域特征參數(shù);然后根據(jù)賽利斯模型重建原始信號的幅值譜;最后結(jié)合相位信息得到去噪后的Lamb波信號。研究了分段計(jì)算裂紋深度的方法。首先通過分段計(jì)算得出裂紋深度與頻率響應(yīng)函數(shù)之間的關(guān)系式,再采用時(shí)間反轉(zhuǎn)方法建立起重構(gòu)信號的波形損傷指數(shù)(DI)和裂紋深度的對應(yīng)關(guān)系式,由該關(guān)系式計(jì)算裂紋深度。該方法與時(shí)間反轉(zhuǎn)方法相結(jié)合不僅減少了計(jì)算的復(fù)雜度也完全加載了裂紋位置的相關(guān)信息。仿真結(jié)果表明,此分段計(jì)算法可以準(zhǔn)確的檢測出裂紋深度。
[Abstract]:Ultrasonic Lamb wave has been widely used in nondestructive testing of large thin plate structures due to its long propagation distance and low attenuation. The current research can realize the two-dimensional imaging of cracks in thin plates and provide a visual detection method for cracks in thin plates. However, the depth information of cracks in thin plates has not yet been effectively detected. Taking aluminum thin plate widely used in engineering practice as the research object, the time reversal method, fractional differential method and ultrasonic Lamb wave nondestructive testing are combined to reconstruct the signal of Lamb wave and enhance the signal. Research on signal denoising and crack depth location. The main contents of this paper are as follows: the propagation law and dispersion characteristics of Lamb wave are analyzed. According to the frequency equation of Lamb wave and the relationship between group velocity and phase velocity, the multimodal characteristics of group velocity and phase velocity of Lamb wave in aluminum thin plate are studied by MATLAB. The short time Fourier transform (STFT) is used to identify the Lamb wave detection signal in aluminum sheet. The time inversion method and the time reversal characteristic of Lamb wave are studied. The received multimodal signal is reconstructed into a single mode signal by time inversion. The finite element simulation of the propagation of Lamb wave in a cracked thin plate is carried out. A denoising method based on fractional differential is studied. In order to reduce the influence of noise on Lamb wave detection signal, a method of denoising based on fractional differential is proposed. In this method, the amplitude spectrum of noisy Lamb wave signal is firstly differentiated by fractional differential, and the characteristic parameters in frequency domain are identified. Then the amplitude spectrum of the original signal is reconstructed according to the Celis model and the de-noised Lamb wave signal is obtained by combining the phase information. The method of calculating crack depth in sections is studied. First, the relationship between crack depth and frequency response function is obtained by piecewise calculation, and then the corresponding relationship between the waveform damage index (DI) and crack depth of reconstructed signal is established by time reversal method. The crack depth is calculated by the relation. The combination of this method and the time reversal method not only reduces the computational complexity but also loads the relevant information of crack location completely. The simulation results show that this method can accurately detect the crack depth.
【學(xué)位授予單位】：南京信息工程大學(xué)
【學(xué)位級別】：碩士
【學(xué)位授予年份】：2017
【分類號】：TB553

【參考文獻(xiàn)】

相關(guān)期刊論文 前10條

1 林椹\ ;席文靜;惠小強(qiáng);;基于COMSOL的矩形體內(nèi)部缺陷圓的無損檢測[J];西安郵電大學(xué)學(xué)報(bào);2017年01期

2 顧建祖;周春杰;駱英;王自平;徐晨光;;CS損傷成像中的時(shí)間逆轉(zhuǎn)多重信號分類算法[J];電子科技;2015年12期

3 楊理踐;趙丹錚;高松巍;;基于超聲蘭姆波的管道防腐層缺陷檢測方法[J];無損探傷;2015年02期

4 劉增華;徐慶龍;董拓燦;龔裕;何存富;吳斌;;基于時(shí)間反轉(zhuǎn)法的Lamb波檢測技術(shù)的研究進(jìn)展[J];實(shí)驗(yàn)力學(xué);2015年02期

5 張宇;黃松嶺;趙偉;王s，

本文編號：2406650