Segmentation of small defects in laser weld of titanium alloy with complex structure

In this paper, the X-ray non-destructive test method of detecting small defects in precision weldments with complex structure is presented. To resolve the difficulty of small defects segmentation in a variable grey image with low contrast and to hold the shape of defects segmented, image processing based on the Visual Basic program method was adopted. The method of grey stretch was used to enhance the X-ray detection image which has relatively low contrast, then the automatic threshold method was carried out to segment the two high-intensity zones and the neighbourhood zones of raster, and weld zones which contain the small defects were extracted. Unsharp masking (USM) sharpening, high pass and smoothing processes were carried out on the extracted weld zones, and small defects in X-ray defection image of precision weldments were segmented using the method of background subtraction. The experimental results show that comparing with the gradient sharpen and smoothing processing, the original shape of the small defects segmented using the method described in this paper can be held, and the calculation speed of the provided algorithm was improved greatly for the processing that was carried out on the extracted weld zones.