数字射线检测技术专题(一)——概述

概括介绍了数字射线检测技术的发展情况、物理基础与标准制定情况。     

Local Flooding Phenomena in Channel and Land Areas Occurring during Dynamic Operation of a PEFC

In this work, we report on flooding phenomena occurring during dynamic operation of a polymer electrolyte fuel cell (PEFC). The combination of high spatially and temporally resolved neutron radiography and submillimeter resolved current density distribution measurements enables the simultaneous observation of local liquid water content and current density transients in the channel and land areas of a differentially operated PEFC air cathode. The local transients of a triangular voltage sweep and a voltage step are presented here. Both results demonstrate that in the land area the current density is only marginally affected by the local liquid water content. In the voltage sweep experiment, at higher cell polarization a limiting current density is observed in the land area as a result of mass transport limitations due to the high lateral diffusion path length. In the channel area the corresponding transients of the liquid water content and the current density both exhibit a hysteresis. The transients of the voltage step indicate liquid water rearrangement in channel and land areas as a slow process occurring on a time scale of several minutes. Thereby, the local cell performance is primarily affected by the local liquid water content in front of the oxygen electrode.     

Reliability of non-destructive test techniques in the inspection of pipelines used in the oil industry

The aim of this work is to evaluate the reliability of non-destructive test (NDT) techniques for the inspection of pipeline welds employed in the petroleum industry. Radiography, manual and automatic ultrasonic techniques using pulse-echo and time of flight diffraction (TOFD) were employed. Three classes of defects were analyzed: lack of penetration (LP), lack of fusion (LF) and undercut (UC). The tests were carried out on specimen made from pipelines containing defects, which had been artificially inserted on laying the weld bead. The results showed the superiority of the automatic ultrasonic tests for defect detection compared with the manual ultrasonic and radiographic tests. Additionally, artificial neural networks (ANN) were used in the detection and automatic classification of the defects.     

对ASTM E1742---2008标准射线照相质量级别规定的讨论

基于射线照相基本理论,对ASTME1742--2008标准关于射线照相质量级别的规定进行了分析讨论,并与ISO标准的规定进行了比较。结果指出,ASTME1742--2008标准基于ASTME1025标准规定的射线照相质量级别,每个级别本身对各厚度并不是等价的,与工业射线照相技术也不构成一个协调的系统。     

射线照相噪声（颗粒度）的理论模式与实验验证

在射线照相影像质量的三要素中,影象噪声（颗粒度）是先决性的。本文介绍射线底片上噪声的理论处理模式,并对工业上常用的Agfa D4和D7胶片,就计算求出的相关于底片黑度的噪声量值,与实验作了比较,两者数值颇为一致。     

厚板焊缝TOFD检测及其与传统检测方法的比较

对板厚＞100 mm的承压设备钢焊缝,采用ASME规范认可的超声衍射时差(TOFD)法检测,灵敏度和缺陷检出率明显优于直线加速器和手工超声检测.将新技术与传统的缺陷评价方法作了比较分析,并通过实例,指出新技术对检测结果的验收特点.     

Detection and 3-D positioning of small defects using 3-D point reconstruction,tracking, and the radiographic magnification technique

In this paper the capability of a 3-D point reconstruction algorithm based on multiple hypothesis tracking is experimentally explored on a setup consisting of a microfocus X-ray source and a digital detector array. The algorithm is verified to detect and 3-D position steel particles with diameters 0.16–0.26 mm radiographed behind 4.7 mm Inconel 718 at two to ten times magnification. At ten times magnification the algorithm is verified to detect and 3-D position with an average error of 0.1 mm pore defects with diameters 0.05–0.25 mm in 4.7 mm thick titanium alloy laser welds.     

新型双丝像质计设计

从射线检测的一般理论,提出了新型双丝像质计设计的理论.试验证明,所提出的理论可以用于指导新型双丝像质计的设计.该像质计可克服标准型双丝像质计只能得到一些特定的不清晰度值问题,并可测量更大范围的不清晰度.     

X射线照相底片复制技术

自制了底片复制曝光箱，进行了X射线照相底片复制试验，成功地复制了熔焊缺陷图谱所用的底片。     

X射线数字成象噪声特性及噪声消除方法研究

X射线数字成象中存在着各种类型的噪声，它们来源于不同的成象环节，如CCD相机、成象屏、射线散射和控制电路噪声等，严重影响成象质量。用实验的方法研究了X射线数字成象系统的噪声来源及其性质，给出了消除噪声的方法和实例，得到了较好的降噪效果。