相控阵兰姆波全聚焦算法的不锈钢薄板分层缺陷检测

航空金属薄板在加工时由于夹杂产生的气孔会随着使用过程中的拉伸和挤压而形成一种闭合型的分层缺陷。针对此类缺陷的检测，提出一种相控阵全聚焦成像算法与兰姆波检测结合的方法。首先从原理上分析并确定激励兰姆波的模态、频率及楔块的角度，其次对3 mm厚度不锈钢板中不同规格、形状的分层缺陷进行试验。结果表明:本研究方法能够对分层缺陷的轮廓成像；兰姆波易受缺陷上端面反射影响，导致缺陷下端面成像出现拖尾图像，且缺陷上端的定位定量精度要高于缺陷下端面；上端面缺陷的定位误差均在4%以内。

Detection of Layered Defects of Stainless Steel Plate by Total Focusing Algorithm of Lamb Wave in Phased Array

Due to the pores generated by the inclusion of aerospace metal plate, a kind of closed delamination defect is gradually formed with the stretching and extrusion during processing. Aiming at the detection of such defects, this paper presents a detection method that combines phased array total focusing method imaging algorithm with Lamb wave detection. Firstly, the mode, frequency and wedge angle of the excitation Lamb wave were analyzed and determined in principle. Secondly, the layered defects of different specifications and shapes in the 3 mm thick stainless steel plate were tested and studied experimentally. Experimental results show that the method proposed in this work can image the contour of layered defects. Lamb waves are susceptible to the reflection of the upper surface of the defect, resulting in a tailing image of its lower end, and the positioning accuracy of the upper end of the defect is higher than that of the lower end. The positioning errors of the upper end surface defects are all within 4%.