对接管焊缝的双壁双投影工业X射线图像处理研究

中文摘要: 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。
Abstract:The primary work to recognize butt weld defects automatically with X-ray radiographs is to achieve effective assessment area accurately. A specific image processing design was proposed 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 3 000 samples showed that the design can detect the center of weld seam and fit it with 100% success rate. The fitting ellipses showed that the weld seam deflection angle error is -0.216°±0.826°. Therefore, it is feasible to extract the effective weld seam area from low contrast digital X-ray image for future assessment.