Abstract: A location detecting algorithm of the welding defect based on the grayscale distribution curve feature was proposed. At first, the welding line X-ray digital image was acquired by the flat panel detector. Secondly, because the problem of large noise and low dynamic range is ubiquitous, the time domain image frame sequence integration method was adopted to reduce the image noise and enhance the defect detail. Then, the optimal integration time was calculated. Thirdly, the grayscale value curve was drawn parallel to the welding line direction. The welding line image was segmented on the basis of its second derivative curve. At last, extreme point was searched in the welding line image. The size and location were decided if obvious maximum value was existed. Experimental results proved the high accuracy.

Key words: non-destructive testing, defect detection, digital X-ray imaging, welding line segmentation, extreme searching