基于全聚焦成像技术的焊缝近表面平面类缺陷检测

Use total focusing method to image the near-surface planar defect in welded joint

摘要: 全聚焦成像技术（TFM，total focusing method）利用虚拟聚焦算法，将采集到的每一组收发信号聚焦于成像区域的每一单元格上（虚拟聚焦点）并最终成像. Half-Skip TFM（HSTFM）是在全聚焦成像技术（TFM）的基础上发展起来的一种超声相控阵后处理成像技术. 文中分别采用TFM，HSTFM这两种算法对位于焊缝试件近下表面的典型平面类缺陷（垂直于试件表面扩展）进行了成像检测. 结果表明，TFM的成像仅观察到平面类缺陷上尖端的存在；而在HSTFM的成像中，平面类缺陷成像完整且清晰可见. 同时，试验中根据HSTFM的成像结果，测量出了缺陷的尺寸与定位信息，并具有较小的测量误差.

Abstract: Total focusing method (TFM) is used to synthetically focus at every image point in a target region. Half-Skip TFM (HSTFM), as a post-processing imaging algorithm of ultrasonic array data, is developed based on TFM. TFM and HSTFM are to image and characterize near-surface planar defects (vertical to the surface of welded joint) in the welded joint, respectively. The result showed that only the indication of the defect tip without root can be seen in the TFM image; in the image formed using HSTFM, the indication of the whole face of the planar defect can be clear observed. Meanwhile, using the HSTFM image of the defect, the near-surface defect with great reliability is sized.