功率管焊接质量射线检测

介绍采用射线方法检测功率管芯片与基座之间的焊接质量。试验证明，选用合适的透照参数可使X射线照相和X射线实时成像对焊接部位的检测均得到较高的对比灵敏度，但X射线照相法成本低廉，一次可透照多个工件，效率高，为该功率管焊接质量的理想检测方法。     

工业射线照相胶片系统的分类和胶片处理的控制

介绍国际标准ISO11699及依据该标准而制订的国家标准的主要内容，目的在于使我国无损检测工作者能更好地了解和采用标准所规定的方法。该标准规定了工业射线照相胶片系统(由胶片和胶片处理组合而成)的分类方法和胶片处理的控制方法。该方法能有效地保证射线照相的影像质量，目前已被许多国家采用。     

75Se源γ射线透照工艺性能试验

通过透照试验,比较75Se源γ射线、192Ir源γ射线与X射线的照相特性,以及不同射线源与不同种类胶片和不同厚度增感屏的组合系统的照相灵敏度;测定了75Se源γ射线的透照厚度与灵敏度的关系,提出了75Se射线照相适用的厚度范围。     

基于Snake模型的铁路铸件气孔检测

研究Snake模型在铁路铸件数字化辐射成像(DR)图像气孔缺陷自动检测中的应用,改进初始轮廓点的获取方法。综合运用阈值分割和区域生长方法得到各气孔的重心,依次对其采用一种射线法得到初始控制点,对初始控制点进行收敛和拟合。对仿真图像的实验结果表明,最小检测尺寸为3×3,能较好地收敛到目标的凹陷区域;对实际铁路铸件DR图像检测的实验结果表明,该方法能准确得到检测区域内多个气孔缺陷的轮廓,不会检测出伪缺陷,具有较高的自动化程度。     

铸件DR图像工件号的增强和分割

铸件DR(DigitalRadiography,数字化X射线照相)图像中工件号的识别对提高检测信息录入的自动化程度具有重要意义。由于受铸件厚薄不均等因素的影响,某些铸件DR图像字符区域存在字符与背景区分不明显等问题。要正确识别出铸件的工件号,必须对图像进行处理。采用加性模型消除字符与背景区分不明显的影响,gamma校正调整图像灰度范围,可增强对比度,获得适宜于二值化的增强图像。改进基于二次边缘提取的二值化算法,用于对铸件DR字符图像的二值化,可以减少笔画断裂问题,得到良好的二值化字符图像。字符分割采用小波变换提取图像列和的突变信息,从而确定字符间隔,能够完整地分割出每个字符。对实际的铸件DR图像进行实验表明,研究的方法获得了良好的效果,为铸件DR图像的工件号自动识别做好了准备。     

Cross-Well Radar. I: Experimental Simulation of Cross-Well Tomography and Validation

This paper explains and evaluates the potential and limitations of conducting cross-well radar (CWR) in sandy soils. Implementing the experiment and data collection in the absence of any scattering object, and in the presence of an acrylic plate [a representative of dielectric objects, such as dense nonaqueous phase liquid (DNAPL) pools, etc.], as a contrasting object in a water-saturated soil is also studied. To be able to image the signature of any object, more than one pair of receiving and transmitting antennas are required. The paper describes a method to achieve repeatable, reliable, and reproducible laboratory results for different transmitter-receiver combinations. Different practical methods were evaluated for collecting multiple-depth data. Similarity of the corresponding results and problems involved in each method are studied and presented. The data show that the frequency response of a saturated coarse-grained soil is smooth due to the continuous and dominant nature of water in saturated soils. The repeatability and potential symmetry of patterns across some borehole axes provide a valuable tool for validation of experimental results. The potential asymmetry across other borehole axes is used as a tool to evaluate the strength of the perturbation on the electromagnetic field due to hidden objects and to evaluate the feasibility of detecting dielectric objects (such as DNAPL pools, etc.) using CWR. The experimental simulation of this paper models a real-life problem in a smaller scale, in a controlled laboratory environment, and within homogeneous soils that are uniformly dry or fully water saturated, with a uniform dielectric property contrast between the inclusion and background. The soil in the field will not be as homogeneous and uniform. The scaling process takes into consideration that as the size is scaled down; the frequency needs to be scaled up. It is noteworthy that this scaling process needs to be extensively studied and validated for future extension of the models to real-field applications. For example, to extend the outcome of this work to the real field, the geometry (antenna size, their separation and inclusion size) needs to be scaled up back to the field size, while soil grains will not. Therefore, soil, water, and air coupling effects and interactions observed at the laboratory scale do not scale up in the field, and may have different unforeseen effects that require extensive study.     

数字射线检测技术专题(三)——成像过程基本理论

从一般的成像概念,介绍了成像过程的卷积理论和空间频域分析傅里叶变换方法,给出了调制传递函数概念和瑞利判据,并讨论了射线检测的不清晰度与系统扩散函数关系。     

Microscopic Evaluation of Strain Distribution in Granular Materials during Shear

The evolution of local strains during shear of particles of a granular material is presented in this paper. A cylindrical specimen composed of 6.5-mm spherical plastic particles was loaded under an axisymmetric triaxial loading condition. Computed tomography (CT) was used to acquire three-dimensional images of the specimen at three shearing stages. The high-resolution CT images were used to identify the 3D coordinates of 400 particles. Nine strain components (normal, shear, and rotation), rotation angles, and local dilatancy angles for particle groups were calculated, and their frequency distribution histograms are presented and discussed. It was found that there is no preferred shear direction, and the standard deviation values for shear strain components (εxy, εxz, and εyz) were almost equal for the specific test shearing stage. Shear strains as high as 25.6% were recorded for some particle groups. Furthermore, granular particle groups rotated in the 3D space with almost equal amounts of rotation strains when loaded under axisymmetric triaxial condition. Rotation strain values are very close to the corresponding shear strains. Compared to particle sliding, rotation plays a major role in the shearing resistance of granular materials. The cumulative vertical rotation angles can be as high as 38° and the horizontal rotation angles have values as high as 60°. The statistical distributions of the local dilatancy angle (ψ1) of particle groups were calculated and found to be increasing as shearing continues. The “global” dilatancy angle value is very close to the mean local ψ1 during the first stage of shearing (i.e, when global εz = ?7.3%)     

250例计算机X线摄影(CR)照片质量问题的技术分析

2005年对我市抽检出具有代表性的250例CR照片存在的质量问题进行了总结、分类，并进行了技术分析。归纳为一、曝光条件选择不当。二、调试技术问题。三、摆位标准问题。四、其他技术因素。目的为同道开阔技术视野，提高照片的影像质量。