基于时间反转的超声兰姆波检测方法研究
发布时间：2019-01-10 18:33
【摘要】：超声Lamb波具有传播距离远、衰减小等特点,已被广泛应用于大型薄板结构的无损检测。目前的研究可以实现薄板中裂纹的二维成像,提供了金属薄板裂纹的可视化检测方法,然而薄板中裂纹的深度信息还未能实现有效的检测,本研究将此问题作为工作重点,以工程实际中广泛应用的铝制薄板为研究对象,将时间反转方法、分数阶微分方法与超声Lamb波无损检测相结合,开展Lamb波信号重构、信号增强、信号去噪与裂纹深度定位等相关研究。本文主要研究内容如下:分析了 Lamb波的传播规律和频散特性。根据Lamb波的频率方程、群速度和相速度的关系,利用MATLAB研究了铝制薄板中Lamb波的群速度和相速度的多模态特性,并利用短时傅立叶变换对铝制薄板中的Lamb波检测信号进行模态识别。研究了时间反转方法及Lamb波的时间反转特性,将接收的多模态信号经过时间反转重构为单模态信号,并对含裂纹薄板中Lamb波的传播进行有限元建模仿真。研究了一种基于分数阶微分的去噪方法。为降低噪声对Lamb波检测信号的影响,提出一种基于分数阶微分的去噪方法,该方法首先利用分数阶微分对含噪Lamb波信号的幅值谱进行各阶微分,识别出频域特征参数;然后根据赛利斯模型重建原始信号的幅值谱;最后结合相位信息得到去噪后的Lamb波信号。研究了分段计算裂纹深度的方法。首先通过分段计算得出裂纹深度与频率响应函数之间的关系式,再采用时间反转方法建立起重构信号的波形损伤指数(DI)和裂纹深度的对应关系式,由该关系式计算裂纹深度。该方法与时间反转方法相结合不仅减少了计算的复杂度也完全加载了裂纹位置的相关信息。仿真结果表明,此分段计算法可以准确的检测出裂纹深度。
[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.
【学位授予单位】：南京信息工程大学
【学位级别】：硕士
【学位授予年份】：2017
【分类号】：TB553
[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.
【学位授予单位】：南京信息工程大学
【学位级别】：硕士
【学位授予年份】：2017
【分类号】：TB553
【参考文献】
相关期刊论文 前10条
1 林椹\ ;席文静;惠小强;;基于COMSOL的矩形体内部缺陷圆的无损检测[J];西安邮电大学学报;2017年01期
2 顾建祖;周春杰;骆英;王自平;徐晨光;;CS损伤成像中的时间逆转多重信号分类算法[J];电子科技;2015年12期
3 杨理践;赵丹铮;高松巍;;基于超声兰姆波的管道防腐层缺陷检测方法[J];无损探伤;2015年02期
4 刘增华;徐庆龙;董拓灿;龚裕;何存富;吴斌;;基于时间反转法的Lamb波检测技术的研究进展[J];实验力学;2015年02期
5 张宇;黄松岭;赵伟;王s，
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