Lamb waves topological imaging combining with Green's function retrieval theory to detect near filed defects in isotropic plates
Lamb waves topological imaging combining with Green's function retrieval theory to detect near filed defects in isotropic plates
复制标题
兰姆波拓扑成像结合格林函数反演理论检测各向同性板近场缺陷
DOI：
10.1088/1674-1056/28/7/074301
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发表时间：
2019
期刊：
影响因子：
--
通讯作者：
Chai Xiaodong
中科院分区：
文献类型：
--
作者：
Zhang Hui;Zhang Haiyan;Xu Mengyun;Fan Guopeng;Zhu Wenfa;Chai Xiaodong
本文提出了一种将格林函数反演理论与基于兰姆波的超声阵列成像相结合的方法，以解决薄铝板中的近场缺陷问题。这些缺陷靠近超声相控阵，且满足近场计算公式。在利用全矩阵采集模式直接获取的响应中，缺陷的近场声学信息会被初始波信号的非线性效应所掩盖。通过对传感器对之间直接接收到的超声信号进行互相关运算，生成重构的阵元间响应全矩阵。这个新矩阵消除了非线性干扰，恢复了近场缺陷信息。在近期超声检测中开发的拓扑成像方法被用于显示散射体。分别在含有两个和四个缺陷的薄铝板上进行了实验。结果表明，使用重构全矩阵时，这些缺陷能够被清晰识别。空间分辨率约等于所选激发模式的一个波长，可识别的缺陷大小约为波长的五分之一。然而，在传统的直接采集图像中，缺陷图像相互重叠，无法区分。所提方法降低了背景噪声，能够对近场缺陷进行有效的拓扑成像。
A method of combining Green's function retrieval theory and ultrasonic array imaging using Lamb waves is presented to solve near filed defects in thin aluminum plates. The defects are close to the ultrasonic phased array and satisfy the near field calculation formula. Near field acoustic information of defects is obscured by the nonlinear effects of initial wave signal in a directly acquired response using the full matrix capture mode. A reconstructed full matrix of inter-element responses is produced from cross-correlation of directly received ultrasonic signals between sensor pairs. This new matrix eliminates the nonlinear interference and restores the near-field defect information. The topological imaging method that was developed in recent ultrasonic inspection is used for displaying the scatterers. The experiments are conducted on both thin aluminum plates containing two and four defects, respectively. The results show that these defects are clearly identified when using a reconstructed full matrix. The spatial resolution is equal to about one wavelength of the selectively excited mode and the identifiable defect is about one fifth of the wavelength. However, in a conventional directly captured image, the images of defects overlap together and cannot be distinguished. The proposed method reduces the background noise and allows for effective topological imaging of near field defects.