涡轮叶片锥束微纳CT散射校正  

Scatter correction of cone-beam micro-nano computed tomography for turbine blades

作　　者：段晓礁[1,2] 唐天旭 周志政 马天宇 Duan Xiaojiao;Tang Tianxu;Zhou Zhizheng;Ma Tianyu(Key Laboratory of OPptoelectronic Technology and Systerms,Education Ministry,Chongqing University,Chongqing 400044,China;Engineering Research Center of Industrial Computed Tomography Nondestructive Testing,Ministry of Education,Chongqing Uniersily,Chongqing 400044,China;Chongqing Zhence Science and Technology Co.,Ltd.,Chongqing 401332,China)

机构地区：[1]重庆大学光电技术及系统教育部重点实验室,重庆400044 [2]重庆大学工业CT无损检测教育部工程研究中心,重庆400044 [3]重庆真测科技股份有限公司,重庆401332

出　　处：《仪器仪表学报》2020年第12期39-47,共9页Chinese Journal of Scientific Instrument

基　　金：国家重大科学仪器设备开发专项(2013YQ030629);重庆市技术创新与应用发展专项(cstc2019jscx-msxmX0058)资助。

摘　　要：航空发动机涡轮叶片无损检测是叶片制造、维修过程中的关键技术之一。常用的检测手段有着色、红外热波、超声等,与其他检测方法相比,计算机层析成像(CT)技术具有检测精度高、成像质量好、缺陷识别能力强等优点。锥束微纳CT由于具有更小的射线源焦点和探测器单元,成像分辨率更高,进一步提高了检测精度。但是,由于微纳CT射线源能量较低,而涡轮叶片自身材料密度较大,导致重建图像伪像更严重,因此需要对其进行校正。采用射束阻止网格(BSG)散射校正板,对涡轮叶片微纳CT检测图像进行散射校正研究。传统的BSG方法采用一块铅条在横向或纵向全覆盖的校正板,需进行两次CT扫描,结合两组投影数据实现校正和图像重建。为进一步提高检测效率,对BSG方法进行了改进,只通过单次扫描即可实现散射校正。对校正板进行了重新设计,铅条全覆盖改为在投影图像左、右两侧交错分布。重建算法在传统FDK算法基础上进行改进,利用一组投影数据获取散射分布的同时,还能重建出完整的CT图像。实验结果表明,单次扫描可获得与两次扫描接近的校正效果,提高图像质量的同时,避免了牺牲检测效率。相比于校正前,信噪比平均可提高107.3%,对比度噪声比平均可提高119.6%。Non-destructive testing of aero-engine turbine blades is one of the key technologies in the process of blade manufacturing and maintenance. Commonly used detection methods include coloring, infrared heat wave, ultrasound, etc. Compared with other methods, CT detection has the advantages of high detection accuracy, good imaging quality and strong defect recognition ability. As cone-beam micro-nano CT has a smaller ray source focus point and detector unit, higher imaging resolution could be achieved, which further improves the detection accuracy. However, due to the low energy of the X ray source of micro-nano CT and the high material density of the turbine blades, the reconstructed image artifacts are more serious, which needs to be specially corrected. Beam Stop Grid(BSG) scatter correction board is used to study the scatter correction of micro-nano CT inspection images for turbine blades. The traditional BSG method uses a correction board with lead strip fully covering in horizontal or vertical direction, which requires to perform two CT scans and combine two sets of projection data to achieve correction and image reconstruction. In order to further improve the detection efficiency, the BSG method was reformed so that the scatter correction can be realized by only a single scan. The correction board was redesigned, and the full coverage of the lead strip was changed to staggered distribution on the left and right sides of the projected image. The reconstruction algorithm was improved on the basis of traditional FDK algorithm. While using a set of projection data to obtain the scattering distribution, a complete CT image could also be reconstructed. Experiment results show that using a single scan can obtain the scatter correction effect close to that of two scans, which avoids sacrificing detection efficiency while improving the image quality. Compared with those before correction, the signal-to-noise ratio can be increased by 107.3% on average and the contrast-to-noise ratio can be increased by 119.6% on averag

关 键 词：锥束CT 涡轮叶片 散射校正 单次扫描 

分 类 号：TN911.73[电子电信—通信与信息系统] TH744[电子电信—信息与通信工程]