Radioscopic Images Research Articles

Explicit geometric model of a radioscopic imaging system

In this paper a new explicit model of a radioscopic imaging system is presented. The model includes three parts: X-ray projection, image intensifier and CCD camera. The X-ray projection is modelled as a linear central projection. The image intensifier is modelled using a new explicit model that considers the curved input screen and the non-linear projection caused by electromagnetic fields. The CCD camera is modelled according to a general 2D projective transformation of the output screen of the image intensifier. Thus, the back-projection, required for 3D reconstruction, can be expressed in a closed-form. The model is compared to seven other known models. The presented model achieves high accuracy.

Chemical stratification and solidification in a differentially heated melt

Horizontal directional solidification of Ga–5%mass In was investigated with real-time radioscopic density visualization. A method to quantify the indium stratification from radioscopic images was developed. It was found experimentally that significant indium stratification developed in the melt-phase, with an average vertical indium concentration gradient of 0.09% mass/mm when the volume fraction of solid reached 0.5. Such a large gradient is justified only by a two-phase particulate melt and not by a liquid solution. Validation of the quantitative results was obtained through a heat transfer model for solidification developed from the observed solid–liquid interface morphology and position. Under a set of reasonable assumptions, the calculated interfaces agree well with observed ones, both in morphology and in position. Factors influencing the morphology of the interface are discussed in detail. The agreement of the conductive model with experiments ascertains that at rather large horizontal temperature gradients the melt is in a conductive mode while common CFD codes may predict convection.

Automated flaw detection in aluminum castings based on the tracking of potential defects in a radioscopic image sequence

Presents a method for inspecting aluminum castings automatically from a sequence of radioscopic images taken at different positions of the casting. The classic image-processing methods for flaw detection of aluminum castings use a bank of filters to generate an error-free reference image. This reference image is compared with the real radioscopic image, and flaws are detected at the pixels where the difference between them is considerable. However, the configuration of each filter depends strongly on the size and shape of the structure of the casting under inspection. A two-step technique is proposed to detect flaws automatically and that uses a single filter. First, the method identifies potential defects in each image of the sequence, and second, it matches and tracks them from image to image. The key idea of the paper is to consider as false alarms those potential defects which cannot be tracked in the sequence. The robustness and reliability of the method have been verified on both real data in which synthetic flaws have been added and real radioscopic image sequences recorded from cast aluminum wheels with known defects. Using this method, the real defects can be detected with high certainty. This approach achieves good discrimination from false alarms.

Radioscopic Images Segmentation by “Edge and Area” Combined Approach for Weld Geometric Characterization

The present paper deals with the geometric characterization of a circumferential weld bead by radioscopy. Weld control can only be performed by tangential irradiation. The series of images obtained by projection, for one rotation of the welded component, is then strongly degraded, as each image contains the projected section of the weld and the superposition of several other sections. The inverse problem is solved using a new image segmentation method, based on an “edge and area” combined approach. The edge approach defines the limits of the weld molten zone by minimum gradient points. The area approach uses a thresholding method based on histogram analysis to position the bottom of the bead exactly. This segmentation leads to fast and automatic control of the weld quality. A validation stage on industrial components shows the method reliability.

Radioscopic Images Segmentation by “Edge and Area” Combined Approach for Weld Geometric Characterization

Radioscopic Images Segmentation by “Edge and Area” Combined Approach for Weld Geometric Characterization

Verification of neutron radioscopic measurement of void fraction by Monte Carlo simulation

Neutron radioscopic images have been simulated using the Monte Carlo method to verify the Σ-scaling method used in void fraction measurement of two-phase flow. Continuous energy Monte Carlo code MCNP was used for the accurate treatment of the test section with complex geometry. Radioscopic images of water-layer thickness distribution in a concentric triple-tube test section were successfully reproduced by the Monte Carlo simulation. The simulated images at various distances between the test section and the converter were obtained using an ideal monodirectional (parallel) beam and realistic beam with unparallelness defined by the L D ratio, thus enabling the separate treatment of the unsharpness of the image caused by the scattered neutrons and the unparallelness of the incident neutron beam. The treatment of the scattered component and the unparallelness of incident beam employed in the Σ-scaling method was verified to be appropriate through the simulation, which shows that the Σ-scaling method could be successfully adopted for the quantitative measurement of void fraction of two-phase flow.

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.

Measurement of Dynamic Mass Changes in Burning Cigarettes by Neutron Radioscopy

Abstract Neutron radioscopic images of burning cigarettes under both static and dynamic smoking conditions were analysed with a video image processor to measure the changes occurring in the images. These changes were related to the actual mass changes occurring in the cigarette rod during the burning process. The neutron images were used to determine the deposition, movement and evaporation of pyrolysis products in the cigarette rod. In addition, the experimental data were used to calculate the mass burn rates of cigarettes. While the instantaneous mass burn rate of a smouldering cigarette can be measured with a balance, neutron radioscopy can be used to determine it under both static and dynamic smoking conditions. The results of this study, along with background information on neutron radioscopy, calibration methods and the image processing procedures, are presented.

Design of a divergence and alignment indicator

The divergence and alignment indicator (DAI) is an extension of the ASTM E803 L/D thermal neutron radiography L/D device that allows the user to determine both the beam centerline and the beam divergence. The DAI was made using aluminium plate and rods, and incorporated cadmium wire for contrast. Circular symmetry was utilized to simplify manufacture. The DAI was placed with the five posts against the film cassette or radioscopic imaging device in the physical center of the beam. The DAI was perpendicular to the selected beam radius when the front and back center Cd wire images overlap. The degree of misalignment was indicated by their image positions. After the DAI was aligned, analysis of the cadmium wire “+” image spacing yielded the beam divergence. The DAI was tested in a neutron beam which has an L/D of 30 but a small degree of divergence. The DAI was also imaged using an X-ray source. The point source predictions of Cd wire image locations showed good agreement with those measured from the X-ray radiograph. The neutron radiographic locations could be predicted using the point source equations, even though the neutron beam was a complex distributed source.

An experimental method for macroscopic cross section measurements using neutron radioscopy

Neutron radioscopic images of high quality could be recently used for the quantitative measurements such as the length, the dimension, the shape or the form and/or the thickness. Generally the neutron transmission curve is expressed by a straight line in a graph of the Y-axis on a log scale and the X-axis on a linear scale, and the macroscopic cross section Σ of a material is estimated from the gradient of the line measured by the thickness for 90% neutron attenuation. In the method presented in this paper, the thickness could be obtained from a curve in a linear ( Y)-log( X) graph. This paper describes an experimental method to measure the macroscopic cross section for various materials using neutron radioscopy. Measured Σ values were relatively adequate compared to reference values.

Automatisches Auswerten von Schweißnaht-Radioskopien

This paper describes a new algorithm for the segmentation of welding defects. A two-step analyse was adopted: a search for defect cadidates with the help of an adapted nonlinear filtering operation, followed by a fine location of defects. The second step can be achieved by using a two threshold operator and assessing the relation of length to width from the extracted defects. In comparison with other automated defect segmentation methods and the manual evaluation of radioscopic images the new approach can better detect critical welding defects such as cracks and lack of fusions.

Advanced radioscopic imaging techniques using compton backscattered radiation : 47251 Kosanetzky, J. 1991 Industrial Computed Tomography II, San Diego, California (United States), 20–24 May 1991. pp. 106–109. The American Society for Nondestructive Testing, Inc., (1991)

Advanced radioscopic imaging techniques using compton backscattered radiation : 47251 Kosanetzky, J. 1991 Industrial Computed Tomography II, San Diego, California (United States), 20–24 May 1991. pp. 106–109. The American Society for Nondestructive Testing, Inc., (1991)

A quantitative comparison between linear X-ray sensitive array and image-intensifier systems

This paper discusses the performance of two basic types of real-time X-ray radioscopic systems, with special relevance to a new linear array based system. The performance is assesseusing the concept of output image quality. Image quality parameters are calculated from the radioscopic images of test objects. Evaluation results are illustrated by examples on industrial specimens.

Automatic radiographic film evaluation by Kontron SEM-IPS : Arun Junai, A.; Hofstede, A.; Koster, H.; van Wolferen, H. Proceedings of the 12th World Conference on Non-Destructive Testing, Amsterdam (Netherlands) 23–28 Apr. 1989, Vol. 1, pp. 120–121. Edited by J. Boogaard and G.M. van Dijk, Elsevier, 1989

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.

Image analysis, modeling, enhancement, restoration, feature extraction and their applications in nondestructive evaluation and radio astronomy : Zheng, Yi. Dissertation Abstracts International, Vol. 49, No. 2, pp. 507 (Aug. 1988)

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.

Detection of defects in wove composites by applying the Wigner distribution to radioscopic images obtained with a linear solid-state array

Detection of defects in wove composites by applying the Wigner distribution to radioscopic images obtained with a linear solid-state array

Detection of defects in wove composites by applying the Wigner distribution to radioscopic images obtained with a linear solid-state array

An accurate method to detect defects in wove composites with the help of a linear X-ray-sensitive imaging device is described. The method is based on extracting space/spatial-frequency features of the signals using the Wigner distribution (WD). The detection performance with the WD analysis processing is also compared with that of the classical spectrogram.