射线数字成像透照厚度与灰度模型研究

Research on Penetrated Thickness and Gray Model of Radiographic Digital Imaging

射线检测作为缺陷无损检测的主要技术,在缺陷定性方面有独特优势,但很难测量缺陷沿射线透照方向尺寸,为此,以钢板为研究对象,基于射线成像理论研究图像灰度与透照工艺条件、线衰减系数、透照厚度之间的关系,采用数值积分和曲线拟合方法将线衰减系数转换成管电压和透照厚度表达式,得到最终图像灰度-透照厚度关系模型。利用实验平台获取实验数据,结合软件拟合求得模型当中的未知参数,并采用钢阶梯试块测量模型的精度,比较阶梯试块厚度的实际值与计算值,结果表明,实际厚度和计算厚度比较接近,误差范围为0.18%~1.49%,实验结果很好地证明了模型的准确性,并且可以根据实际透照条件和图像灰度计算钢材料中缺陷处的透照厚度,得到缺陷沿射线透照方向的尺寸,结合数字成像图像测量垂直于射线方向上缺陷尺寸,对缺陷进行全方位评定。

As the main technology of defect nondestructive testing,radiographic testing has unique advantages in defect characterization,but it is difficult to measure the size of the defects along the X-ray penetration direction.For this reason,taking steel plate as the research object,based on the radiographic imaging theory,the relationship between the image gray and the penetration process conditions,linear attenuation coefficient,and penetration thickness was studied.Numerical integration and curve fitting methods are used to convert the linear attenuation coefficient into tube voltage and penetration thickness expressions.The final image grayscale-penetration thickness relationship model is obtained.By using the experimental platform to obtain the experimental data,the unknown parameters in the model are obtained by software fitting,and the accuracy of the model is measured by the steel step test block,and the actual thickness and the calculated thickness of the step test block are compared.The results show that the actual thickness and the calculated thickness are close,the error range is 0.18%--1.49%.The experimental results prove the accuracy of the model well,and the thickness of the defect in the steel material can be calculated according to the actual penetration conditions and the image gray level,and the size of the defect along the ray penetration direction can be obtained.Combined with the digital imaging image to measure the size of the defect perpendicular to the ray direction,the defect can be evaluated in an all-round way.