Near-field Imaging of Defects Based on the Dynamic Shear Strain Analysis over the A0-mode Lamb Wave Field
Near-field Imaging of Defects Based on the Dynamic Shear Strain Analysis over the A0-mode Lamb Wave Field
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基于 A0 模式兰姆波场动态剪切应变分析的缺陷近场成像
DOI：
10.9746/sicetr.47.422
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发表时间：
2011
期刊：
影响因子：
--
通讯作者：
Ryoji Inoue
中科院分区：
文献类型：
--
作者：
K. Teramoto;Ryoji Inoue
兰姆波已被用于薄板状结构的无损检测。然而，传统的飞行时间技术是不可靠的定位缺陷，即使在各向同性板，因为在兰姆波传播的分散性。本文提出了一种新的动态剪切应变分析方法，该方法能够通过重建近场图像来定位缺陷。所提出的成像方法利用的行列式的动态剪切应变的协方差矩阵定义在对象表面。行列式表示入射波前与散射波前的相关强度调制的分布。因此，行列式的值在缺陷的近场中显著增加。在这项研究中，计算过程中的波场附近的缺陷进行了讨论，并通过FDTD模拟和声学实验研究其物理意义。
Lamb waves have been used for non-destructive inspection of thin-plate-like structures. However, the conventional time-of-flight technique is not reliable for locating the defects even in isotropic plates because of the dispersiveness in the Lamb wave propagation. Avoiding difficulties caused by the dispersiveness, this paper proposes a novel dynamic shear strains analysis which has an ability to localize defects with reconstructing nearfield images. The proposed imaging method utilizes the determinant of the dynamic shear strains covariance matrix which are defined over the object surface. The determinant denotes the distribution of correlated intensity modulation of the incident wave fronts with scattered ones. The value of the determinant, therefore, increases significantly in the near-field of the defects. In this study, the computational process in the wave field near the defects is discussed and their physical meanings are investigated through FDTD-simulations and acoustic experiments.