对接管焊缝的双壁双投影工业X射线图像处理研究

准确提取对接管焊缝的有效评定区域是实现自动识别X射线焊缝图像缺陷的首要步骤。针对这一难题,提出一系列结合X射线成像机理和焊缝灰度特征的图像处理方法。首先,以X射线成像原理为基础,对焊缝图像进行灰度变换;然后,以区域图像灰度方差为基础,修正焊道的偏移;进而利用最小二乘法拟合环形管焊缝,确定其中心;最后,利用距离映射方法将环形焊缝变换成矩形焊缝。根据3 000样本的测试结果,该算法对于焊缝中心点的确定以及椭圆拟合的成功率为100%,焊缝偏转角度修正误差为-0.216°±0.826°。因此,该设计能可靠地提取出低对比度X射线数字图像中的焊缝有效评定区域。

Image Processing Research on Double-walled Double-imaging Industrial X-ray Radiographs of Butt Weld

The primary work to recognize butt weld defects automatically with X-ray radiographs is to achieve effective assessment area accurately. In this paper, we propose a specific image processing design to overcome extracting difficulties by combining X-ray imaging mechanism and weld gray features. Firstly, it conducts gray-scale transformation of the butt weld image based on X-ray imaging fundaments. Secondly, it corrects the offset of weld bead based on the regional gray variance. Thirdly, it adopts Least-squares method to fit the weld seam and determine its center. Lastly, it converts weld seam from annular to rectangular using the distance map. The results of 3000 samples show that the design can detect the center of weld seam and fit it with 100% success rate. The fitting ellipses show that the weld seam deflection angle error is . Therefore, it is feasible to extract the effective weld seam area from low contrast digital X-ray image for future assessment.