板结构裂纹兰姆波阵列复合成像方法研究

针对板结构中裂纹方向识别及定量检测问题,提出了一种板结构兰姆波阵列复合成像方法。利用超声阵列采集的单模态兰姆波全矩阵数据,分别提取其幅值信息和极性信息,进行全聚焦成像和极性一致成像,并利用极性一致成像对全聚焦成像进行了加权处理;对全阵列进行子阵列划分,计算出各子阵列的特征矢量,并进行加权合成,得到矢量全聚焦成像;利用全聚焦成像的强度信息和矢量全聚焦成像的方向信息,综合得到兰姆波阵列的复合成像,并从中提取出缺陷的方向及空间分布范围等信息。实验结果表明,提出的兰姆波阵列复合成像方法可以很好地实现板中多个裂纹方向识别,其角度测量误差在20%以内。本文工作为裂纹缺陷识别及定量检测做了有益探索。

Study on the compound imaging method for crack detection in plate structure using array of Lamb wavesJiao

Aiming at the problem of the direction identification and quantitative detection of cracks in metal plate, a compound imaging method for plate structure is developed using array of Lamb waves. From the total matrix data of single mode Lamb waves acquired with ultrasonic array, the amplitude and sign information is extracted, which are used for total focus imaging and sign coherence imaging; and the sign coherence imaging is used to perform the weighted processing for the full focus imaging. The total array is divided into sub arrays, the feature vector of each sub array is calculated, and all of them are superimposed with weight to get the vector total focus imaging; Using the intensity information on the weighted total focus imaging and the direction information of the vector total focus imaging, the compound imaging is obtained, from which the orientation and dimension information of the crack is extracted. The experiment results demonstrate that the proposed compound imaging method using array of Lamb waves can achieve the orientation characteristic identification of multiple cracks in plate nicely, and the angle measurement errors is within 20%. The research provides a useful exploration for the crack defect identification and quantitative detection of metal plate.