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Micro crack detection based on the spatio-temporal gradient method

基于时空梯度法的微裂纹检测

基本信息

批准号：
15560360
负责人：
TERAMOTO Kenbu
金额：
$ 1.34万
依托单位：
Saga University
依托单位国家：
日本
项目类别：
Grant-in-Aid for Scientific Research (C)
财政年份：
2003
资助国家：
日本
起止时间：
2003 至 2004
项目状态：
已结题

项目摘要

1:The first results presents a defect characterization method by spatio-temporal gradient analysis over the Lamb wave field. The surface ultrasound waves that propagate in the direction of the layer are potential candidates of non-destructive evaluation(NDE) methodology. The proposed method has an ability to classify the surface acoustic wave field through the rank of the covariance matrix defined over the four-dimensional vector space which is spanned by following components : a vertical displacement, its vertical velocity, and a pair of shear strains of the surface. The covariance matrix provides the information about defects. The determinant of the covariance matrix, therefore, is proposed as the index of homogeneity of the object surface. In this study, the computational process in wave field near the defects is discussed and their physical meanings are investigated through FDTD-simulations and acoustic experiments.2.The second results are shown as follows.In this study, the local phase velocimetry based on the spatio-temporal gradient analysis is derived theoretically. The proposed method has an ability to characterize the phase velocity of the Lamb-wave propagation through the linearity among the 4-dimensional vector which is composed by following components : (1)a vertical (z-directional) displacement, (2)its vertical particle velocity, (3)x-directional and (4)y-directional out-of-plane strains. In this study, the computational process of the local velocimetry is discussed and their physical meanings are investigated through numerical and acoustical experiments.

1：第一个结果提出了一种缺陷表征方法的时空梯度分析在兰姆波场。在层的方向上传播的表面超声波是无损评价（NDE）方法的潜在候选者。所提出的方法具有通过定义在四维向量空间的协方差矩阵的秩来对表面声波场进行分类的能力，所述四维向量空间由以下分量构成：垂直位移、垂直速度和表面的一对剪切应变。协方差矩阵提供关于缺陷的信息。因此，协方差矩阵的行列式，建议作为指标的均匀性的对象表面。本文讨论了缺陷附近波场的计算过程，并通过时域有限差分（FDTD）模拟和声学实验研究了缺陷附近波场的物理意义。2.研究结果如下：本文从理论上推导了基于时空梯度分析的局部相位测速法。所提出的方法具有通过由以下分量组成的4维矢量之间的线性来表征兰姆波传播的相速度的能力：（1）垂直（z方向）位移，（2）其垂直粒子速度，（3）x方向和（4）y方向的平面外应变。本文讨论了局部速度测量的计算过程，并通过数值计算和声学实验研究了其物理意义。