基于CT图像变异系数的小缺陷定量不确定度评定

Uncertainty Analysis of small defect quantification based on Coefficient of Variation in CT image

摘要:

针对工业CT检测技术对小缺陷定量及不确定度评定缺乏有效手段,分析小缺陷尺寸、材料密度对CT图像局部灰度变异系数的影响规律,结果显示变异系数随小缺陷尺寸的增大而增大,其幅值与小缺陷尺寸相关系数达99%以上。建立基于变异系数的小缺陷定量及不确定度评定方法,采用不锈钢材料加工一系列不同尺寸的小缺陷参考试块开展工业CT实验。结果表明：在Ф50mm圆形对比试样上对已知Ф0.7mm的人工通孔缺陷上进行验证,缺陷尺寸实测结果为0.386mm_²±0.073 mm_²。本方法定量精度高、测量过程简便,对金属材料内部小缺陷定量及不确定度评定有一定的参考价值。

Abstract:

Aiming at the lack of effective methods for the quantification and uncertainty evaluation of small defects in industrial CT systems, the effects of small defect size and material density on the local grayscale variation coefficient of CT images are analyzed. The correlation between the amplitude of the coefficient of variation and the size of the small defect is explored. The results show that the local variation coefficient increases with the increase of the size of the small defect, and the correlation coefficient between its amplitude and the size of the small defect is more than 99%. Establish a small defect quantification and uncertainty evaluation method based on the coefficient of variation. This method verifies the known through-hole defect of Ф0.7mm on a Ф50mm circular contrast sample. The actual measurement result is 0.386mm_² ± 0.073 mm_². This method has high quantitative accuracy and simple measurement process. It has certain reference value for the quantification and uncertainty evaluation of small defects in metal materials.