基于超声杂波抑制的缺陷检测

超声TOFD(time of flight diffraction,衍射时差)法检测的D扫描图像中,作为背景杂波的侧向波与近表面缺陷波会发生混叠,致使近表面缺陷不易于检测. 针对这一问题,提出一种基于杂波抑制的缺陷检测方法. 该方法通过图像能量分布统计,确定背景杂波分量并予以去除,从而分离出与其混叠的缺陷信号,实现近表面缺陷的检测. 建立了的超声TOFD法检测信号的数学模型,阐明了基于图像能量分布的杂波抑制原理. 制作了人工缺陷试块及实际焊缝试块,并对其检测获取的图像进行了杂波抑制处理. 结果表明,提出的方法可有效去除图像中的非缺陷目标、提取近表面缺陷波,从而提高系统的有效检测范围.

Defect detection method based on ultrasonic clutter wave suppression

In ultrasonic TOFD (time of flight diffraction) D-scan image, the lateral wave overlaps with the near surface defect wave, which makes it difficult in the testing of shallowly buried defect. In order to solve this problem, a defect testing method based on background clutter suppression is presented. The energy distribution in the image is calculated to determine the clutter wave component. Then the clutter wave is removed to separate the defect signal from the background image. The mathematical model for TOFD signal is established. The principle of clutter wave suppression method is described in details. Artificial defects contained block and the weld test pieces were made and tested. The collected D-scan images with clutter wave suppression were processed. The results show that using the proposed method, the background clutter wave can be removed from the D-scan image and the defect signal can be extracted from the overlapped waves effectively. The defect detection range for TOFD can be improved using the proposed method.