射线实时成象检验技术

射线实时成象检验技术,是实时地将射线照相的强度分布转换为可见光图象、对检验结果作出评定的技术,这种技术儿乎与胶片射线照相检验技术同时发展.主要的射线实时成象检验系统有:(1)X射线荧光实时成象检验系统.(2)图象增强实时成象检验系统.(3)数字实时成象检验系统.表1列出了三种检验技术系统的主要特点.     

射线实时成象检验技术

1 研究概况 美国材料试验学会标准ASTM E1000—92将射线检测技术分为三种:射线照相检验技术(radiography)、射线实时成象检验技术(radioscopy)和其它射线检测技术。射线照相是指采用胶片或类似胶片的成象方法,射线实时成象是指随着成象物体的变     

我国射线检测技术近年的发展

简要介绍我国工业射线检测技术自20世纪90年代以来的最新发展概况,包括射线照相检验技术理论、工艺和器材,非胶片射线照相技术,实时成像检验技术,射线层析成像技术,康普顿散射成像技术以及标准化等方面的发展。     

射线Ⅲ级人员补充专题讲座（续）

第7专题实时成像检验技术71概述射线实时成像检验技术．是实时地将射线照相的强度分布转换为可见光图像、对检验结果作出评定的技术．这种技术几乎与胶片射线照相检验技术同时发展。主要的实时成像检验技术有：（1）X射线荧光实时成像检验技术；（2）图像增强实时成像检验技术；（3）数字实时成像检验技术。表7－1列出了三种检验技术系统的主要待点。早期的射线实时成像检验系统是X射线荧光检验系统．它采用荧光屏将X射线照相的强度分市转换为可见图像．50年代左右引入了电视系统．通过电视摄像、在监视器上观察图像。荧光屏图像由于存在…     

射线实时成象检验技术

射线实时成象检验系统得到的图象是电视系统的扫描光栅图象,与胶片射线照相的图象相比,它具有完全不同的结构.常规胶片射线照相图象,由于胶片乳剂的颗粒很小,在一般情况下清晰度不会成为影响图象质量的重要因素.常用的测定胶片射线照相灵敏度的象质计(丝型、孔型),主要反映的是图象对比度.射线实时成象检验系统的图象由象素构成,图象常常可以达到较高的对比度,但不能达到较好的清晰度.这种情况表朗,采用常规的象质计,不能准确测定射线实时成象检验系统图象的质量.美国ASTM E1411—91“射线实时成象检验系统鉴定方法”规定,对射线实时成象检验系统的综合性能应从三方面评定:①空间分辨力(或简称为分辨力).②对比度灵敏度.③IQI灵敏度.     

射线实时成像系统与传统射线照相的可靠性对比试验及分析

介绍了射线实时成像系统的组成、工作原理及特点。通过对实时成像系统与传统射线照相方法进行可靠性对比试验以及对试验的过程和结果的分析，得出了在锅炉制造行业中射线实时成像系统与传统照相技术相比较所具有的优越性。     

第七讲射线实时成象检验技术

1　概述射线实时成象检验技术是随着成象物体的变动图象迅速改变的电子学成象方法 ,它与胶片射线照相检验技术几乎是同时发展的。早期的射线实时成象检验系统是 X射线荧光检验系统 ,它采用荧光屏将 X射线照相的强度分布转换为可见光图象。 50年代左右引入了电视系统 ,通过电视摄象 ,在监视器上观察图象。由于存在图象亮度低 (仅为 0 .3× 1 0 -3cd/m2左右 )、颗粒粗、对比度梯度低等缺点 ,荧光屏图象的细节和灵敏度都低于胶片图象 ,观察这种图象需 30 min的眼睛暗适应时间 ,这限制了该技术的实际应用。这种系统主要应用于轻合金铸件、薄焊…     

X射线实时成像技术在焊缝探伤中的应用

X射线实时成像是一项新兴的无损检测技术,它具有快速、准确、直观、成本低廉等优点,可以代替常规的X射线胶片照相探伤方法。本文概述了X射线实时成像技术的要点和焊缝探伤中的应用情况。     

射线实时成像检验系统的性能及其鉴定方法

射线实时成像检验技术正在不为发展,本文以ＡＳＴＭ标准关于射线实时成像检验技术的主要规定的基础,简要介绍了射线实时成像检验系统的性能和性能鉴定方法。     

变截面工件射线照相检验技术

依据美国有关标准多年来关于像质计灵敏度黑度的规定和射线照相检验技术基本理论，对变截面工件射线照相检验技术的基本问题进行系统性讨论，给出了技术的具体处理，初步解决了变截面工件射线照相检验技术问题。     

射线实时成像检测最新欧洲标准

对工业射线实时成像检测的最新欧洲标准EN 13068—2001 作了简要介绍和评述,包括检测等级、系统等级、操作要求、透检布置、像质评价、图像处理、数据存储和结果记录等。并与新版美国ASME规范进行比较,旨在为国内制订相应行业标准提供借鉴。     

Complementarity of a photon-counting system and radioscopy for inspection of cast aluminium components

This study aims at establishing X-ray methods for inspection of cast aluminium components by combining two approaches, a radioscopic inspection, and a photon-counting system.Indeed, radioscopy is widely used in castings inspection for automatic defect detection and is an efficient method for characterising rather small thicknesses, typically less than 40 mm. However, cast components often show a high range of thicknesses and imaging the whole range is difficult. We propose to use photon-counting measurements to complement the radioscopic image for high thicknesses. Photon-counting is not an imaging tool, but the thickness sensitivity obtained from photon-counting measurements (number of X-ray photons transmitted through the object) is much better than what can be obtained by classical radioscopy for up to 60 mm of aluminium. For high thicknesses of aluminium, within small volumes where defects are believed to be critical, the photon-counting system allows getting information additional to that obtained from classical radioscopy images.     

焊缝X射线检测及其结果的评判方法综述

分析了焊缝X射线检测方法的现状，指出了目前存在的主要问题；介绍了焊缝X射线检测结果的人工评定和计算机辅助评定方法，论述了国内外焊缝X射线检测结果计算机辅助识别的研究现状，研究结果表明，X射线数字实时成像技术是焊缝射线检测的发展方向，焊缝射线数字图像的计算机自动分析与识别技术是射线实时成像技术成功应用的基础。     

射线检测在复合材料无损检测中的应用

随着新型复合材料的迅速开发和应用，其制造过程监测、产品缺陷检测及质量评价等已成为不可缺少的环节。射线检测技术在复合材料无损评价中占有极其重要的地位。对现有的主要射线检测方法，包括X射线照相法、X射线实时成像法、射线计算机断层扫描法、射线断层形貌成像法、康普顿散射法及中子照相法等在复合材料质量评价中的应用状况进行了简要的评述，并指出复合材料射线检测的发展趋势。     

小直径导管点焊接头的射线检测方法

对于直径不大于5mm的小直径导管点焊焊接接头的检测,开展了射线检测方法研究,试验表明采用先垂直于焊接平面透照,再旋转90°透照的两次透照射线检测方法,可实现导管焊接质量的可靠检测。而对于该类焊缝中即使采用微焦点DR成像技术也难于检出的微米量级缺陷,可通过采取金相测试方法,不断优化焊接工艺参数来消除。     

Geometric characterization of a circumferential seam by automatic segmentation of digitized radioscopic images

The present study deals with the nondestructive control of a circumferential seam by digital radioscopy. A series of images for one complete revolution of the welded component is available. We first resort to a joint approach by simulation and experimentation. This approach allows the detection of the molten zone limits for an initial image. We then develop a segmentation method that permits automatic extraction of the geometric characteristics of the set of images representative of the weld. These measures supply fast and automatic control of the weld quality. Results are shown for real components.     

Structure and distribution of oxides in aluminium foam

Foaming of aluminium is investigated under oxidizing and non-oxidizing gas atmospheres. Foams were prepared by mixing and pressing Al99.95 and TiH₂ powders and foaming the pressed material in a gas-tight X-ray transparent furnace while following the process by X-ray radioscopy. The structure and distribution of the oxides present in the powders, precursors and foams were studied by light microscopy, scanning and transmission electron microscopy. Sequential focused ion beam slicing was used to obtain tomographic images of oxide and micropore distributions within the individual cell walls of the foams. A complex hierarchical structure of the oxides is found. Oxides reside in the bulk of the cell walls without a pronounced segregation to the gas/metal interfaces. The presence of air retards foaming due to oxidation of the outer surface.     

Observation of dendritic growth and fragmentation in Ga–In alloys by X-ray radioscopy

Abstract

Capabilities of the X-ray attenuation contrast radioscopy were utilised to provide a real time diagnostic technique for observations of dendritic growth and fragmentation during solidification of a Ga–30In (wt-%) alloy. The solidification process was visualised by means of a microfocus X-ray tube providing shadow radiographs at spatial resolutions of about 10 μm. Experiments have been carried out to solidify the Ga–In alloy unidirectionally either starting from the bottom or the top of the specimen. The first case is significantly affected by solutal convection, which governs a redistribution of solute concentration. A detachment of dendrite side arms, which is unambiguously caused by melt flow, was not observed. Dendritic fragmentation occurs during the solidification in the reverse top down direction. Variations of the applied cooling rate excited a transition from a columnar to an equiaxed dendritic growth (CET).     

Solidification of metal foams

Expansion and contraction phenomena during solidification of liquid metal foams were studied. Such foams were processed by mixing metal powders with TiH₂ powder and compacting the resulting blends, after which the compacted powders were melted. The subsequent foaming process was monitored in situ by X-ray radioscopy. An intermediate expansion stage during solidification was observed. This solidification expansion (SE) could be linked to phase transformations in the alloy. SE was found to depend mainly on the time spent at the foaming temperature before cooling (holding time), the cooling rate and the alloy composition. The interplay between gas shrinkage, solidification shrinkage, gas production by the blowing agent and gas losses due to out-diffusion was identified as the main reason for SE. While the blowing agent had a major influence on SE, gas dissolved in the metal also played a role, since some SE was observed in foams blown without TiH₂ by pure pressure manipulation.     

The effect of cooling rate on the structure and properties of closed-cell aluminium foams

The application of different cooling rates as a strategy to enhance the structure of aluminium foams is studied. The potential to influence the level of morphological defects and cell size non-uniformities is investigated. AlSi6Cu4 alloy was foamed through the powder compact route and then solidified, applying three different cooling rates. Foam development was monitored in situ by means of X-ray radioscopy while foaming inside a closed mould. The macro-structure of the foams was analysed in terms of cell size distribution as determined by X-ray tomography. Compression tests were conducted to assess the mechanical performance of the foams and measured properties were correlated with structural features of the foams. Moreover, possible changes in the ductile–brittle nature of deformation with cooling rate were analysed by studying the initial stages of deformation. We observed improvements in the cell size distributions, reduction in micro-porosity and grain size at higher cooling rates, which in turn led to a notable enhancement in compressive strength.