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Some current developments in NDE of corrosion
N DT Abstracts 55176 Thoe, R.S. Single sided tomography of extremely large dense objects Lawrence Livermore National Lab., California (United States), DE 93017993/GAR, 14pp. (24 Mar. 1993) The author has developed a technique which can be used to obtain three dimensional radiographs using Compton scattered radiation from a monochromatic source and a high efficiency, high resolution germanium spectrometer. This paper gives specific details of the reconstruction technique and presents the results of numerous numerical simulations and compares these simulations to spectra obtained in the laboratory. In addition the author presents the results of calculations made for the development of an alternative single sided radiography technique which will permit inspection of the interior of large objects. 54853 Lamb, S.R.; Clark, G. Some current developments in NDE of corrosion Proceedings of the 41st Annual Welding Conference and National AINDT Conference, Wollongong (Australia), 27 Sep. - 1 Oct. 1993. pp. 14-21. WTIA, AINDT (1993) This paper discusses two promising methods for the detection and assessment of hidden corrosion. The first is based on detecting the acoustic emission generated by active corrosion cells, and using triangulation methods to determine the location of significant areas. The second method is Compton Back-Scattering of X-rays, which offers a means of detecting corroded areas on the basis that the corrosion product has a lower effective density of free electrons. 54527 Lawson, L. Measurement of layered corrosion with Compton backscatter Review of Progress in Quantitative Nondestructive Evaluation, La Jolla, California (United states), 19-24 Jul. 1992. Vol. 12B, pp. 1971-1978 Edited by D.O; Thompson and D.E. Chimenti. Plenum Press (1993) ISBN 0.306~A.A.483-6 Recently, interest in aircraft corrosion has renewed interest in Compton backscatter for NDT. This interest appears to be justified partly because aircraft corrosion often takes a layered morphology; and, the needed information is the thickness of the layers. Compton x- ray backscatter has been shown to be a useable method for measuring the thickness of metal layers and for distinguishing corrosion in aluminum. When Compton backscatter is used for this purpose, the scattering zone, defined by the camera geometry, is scanned through the material. The resulting raw data, counts per volume element at the various positions, requires reconstruction to obtain the actual electron density versus distance. It is from this electron density plat that thickness measurements can be made. The reconstruction method used here is in two parts, an approximate reconstruction assuming a constant ratio of electron density to linear x-ray absorbtion coefficient followed by a correction for beam hardening effects.
Balogun, F.A.; Spyrou, N.M. Compton scattering tomography in the study of a dense inclusion in a lighter matrix 54523
Nuclear Instruments and Methods in Physics Research B, Vol. 83, No. 4, pp. 533-538 (1993) The number of photons inelastically scattered within a well defined solid angle used in Compton scattering is linearly dependent on the mass density and hence the electron density of the sample. The effect of a high density high atomic number material (Pb), and a lower atomic number material (Cu) in an aluminium matrix on the resultant Compton scattered images has been investigated. Better contrast, signal-to- noise ratio, and measurement precision are recorded for the lead inclusion, as expected. A minimum detectable change in mass density of 4.2 g/cm for our system is recorded.
53731 Babot, D.; Lefloch, C.: PeLt, G. Testing and characterization of composite materials by Compton Tomodensitometry (In French) Aerospatiale, Paris (France), N93-21458/3/GAR, I 0 pp. (1992) The Compton diffusion method is explained and examples of its use in measuring density and thickness of materials and in studying faults are given. This method uses X-rays produced by an industrial X-ray tube. It produced a three dimensional image of all types of materials without even touching the object. The X-ray tube and the detector are placed on the same side of the object. It is consequently possible to test a tank wall, even if the tank is full, since the rays do not need to transverse the object. 53729 Harding, G. Novel applications of X-rays in non-destructive testing Colloquium on NDT 1992: Non-Destructive Testing in the Single European Market, London (United Kingdom), 15 June 1992. pp. 5/1-5/3. Institution of Electrical Engineers (1992). Given the fact that X-ray scattering is a very sensitive probe of material properties, several laboratories have studied over the years the feasibility of X-ray scatter imaging. Here at Hamburg we have concentrated on just two types of X-ray scattering i.e. Compton and coherent.
Alvaro, M.; Moreno, F.I.; Martindebernardo, J.M.; Cortes, V. Noncontact nondestructive tests (In Spanish) 53615
Constrncciones Aeronauticas S.A., Madrid (Spain), N9320929/4/GAR, 12 pp. (1992) Methods developed for noncontact nondestructive tests are reviewed. These tests were developed to improve the applicability of nondestructive tests, which were constrained to the use of sensors and contacts. The techniques applied involve ultrasonic waves for lasers, optical interferometry, thermography and Compton effect X-ray analysis. The following topics are presented: holographic pattern, holographic reconstruction, source laser, technical holographic inspection methods, real time interferometry, pulsed laser holograms, application problems and result interpretation thermal analysis principles and procedures, production of ultrasonic waves by lasers, and ultrasonic interferometric analysis. 53518 Prettyman, T J-L; Gardiner, R.P.; Russ, J.C.; Verghese, K. A c o m b i n e d transmission a n d scattering tomographic approach
to composition and density imaging Applied Radiation and Isotopes, Vol. 44, No. 10-1 l, pp. 1327-1341 (Oct.-Nov. 1993) A method of imaging the composition and density of industrial samples by combining information obtained from a transmission tomographic scanner and a projective. Compton scatter imaging system is described. A reconstruction algorithm with attenuation and multiple scatter correction capabilities is developed around a detailed model of the Compton scatter imaging system. Monte Carlo simulation is used to generate realistic data for the determination of model parameters, the analysis and design of device components, and for testing the reconstruction algorithm. 52240 Gusev, E.A.; Potapov, V.N.; Karpelson, A.E. Analysis of the characteristics of scanning inspection systems using hackscattering Russian Journal of Nondestructive Testing, Vol. 28, No. 8, pp. 505-509 (Apr. 1993) The characteristics of a Compton scanner giving information on the structure of the inspected article from recording x-ray backscattering are analysed on the basis of information obtained by the Monte Carlo method. Methods of selecting the geometric parameters and energy of the x-ray source are examined and the maximum sensitivity and frequency-contrast characteristics of the giver, inspection system are evaluated.
54011
Jensen, T.; Gray, J.N. Material thickness measurements using Compton backscatter
51969 Anon Structural investigation of a damaged GRP/foam sandwich composite using x-ray computed tomography
Review of Progress in Quantitative Nondestructive Evaluation, La Jolla, California (United States), 19-24 Jul. 1992. Vol. 12A, pp. 303-308. Edited by D.O. Thompson and D.E. Chimenti. Plenum Press (1993). ISBN 0-306. ~4A.83-6. Most studies of backscatter for nondestructive inspection have used a conventional bremsstrahlung X-ray source. Which tends to obscure the fine points evident in scattering equations. We have approached this problem by using a monochromatic X-ray source, which allows us to quantitatively compare scattering measurements with predictions. We describe a Monte Carlo model of the X-ray backscatter process and a comparison with experimental measurements.
Australian Institute of Non-Destructive Testing National Conference, Melbourne (Australia), 19-21 Aug. 1991.9pp. AINDT (1991) The construction of the Australian Mine Hunter Inshore (MHI) vessels presents a difficult nondestructive testing (NDT) problem because the nature of the foam core prevents ultrasonic inspection, the application in large panels requires inspection from one side, and for service use the method must be portable to dockyard facilities. Two approaches are being investigated in order to solve this NDT problem. The first method is to demonstrate the capabilities of the x-ray computed tomography (CT). The second approach is to evaluate the Compton backscaUer technique which
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Balogun, F.A.; Spyrou, N.M. Compton scattering tomography in the study of a dense inclusion in a lighter matrix 54523
Nuclear Instruments and Methods in Physics Research B, Vol. 83, No. 4, pp. 533-538 (1993) The number of photons inelastically scattered within a well defined solid angle used in Compton scattering is linearly dependent on the mass density and hence the electron density of the sample. The effect of a high density high atomic number material (Pb), and a lower atomic number material (Cu) in an aluminium matrix on the resultant Compton scattered images has been investigated. Better contrast, signal-to- noise ratio, and measurement precision are recorded for the lead inclusion, as expected. A minimum detectable change in mass density of 4.2 g/cm for our system is recorded.
53731 Babot, D.; Lefloch, C.: PeLt, G. Testing and characterization of composite materials by Compton Tomodensitometry (In French) Aerospatiale, Paris (France), N93-21458/3/GAR, I 0 pp. (1992) The Compton diffusion method is explained and examples of its use in measuring density and thickness of materials and in studying faults are given. This method uses X-rays produced by an industrial X-ray tube. It produced a three dimensional image of all types of materials without even touching the object. The X-ray tube and the detector are placed on the same side of the object. It is consequently possible to test a tank wall, even if the tank is full, since the rays do not need to transverse the object. 53729 Harding, G. Novel applications of X-rays in non-destructive testing Colloquium on NDT 1992: Non-Destructive Testing in the Single European Market, London (United Kingdom), 15 June 1992. pp. 5/1-5/3. Institution of Electrical Engineers (1992). Given the fact that X-ray scattering is a very sensitive probe of material properties, several laboratories have studied over the years the feasibility of X-ray scatter imaging. Here at Hamburg we have concentrated on just two types of X-ray scattering i.e. Compton and coherent.
Alvaro, M.; Moreno, F.I.; Martindebernardo, J.M.; Cortes, V. Noncontact nondestructive tests (In Spanish) 53615
Constrncciones Aeronauticas S.A., Madrid (Spain), N9320929/4/GAR, 12 pp. (1992) Methods developed for noncontact nondestructive tests are reviewed. These tests were developed to improve the applicability of nondestructive tests, which were constrained to the use of sensors and contacts. The techniques applied involve ultrasonic waves for lasers, optical interferometry, thermography and Compton effect X-ray analysis. The following topics are presented: holographic pattern, holographic reconstruction, source laser, technical holographic inspection methods, real time interferometry, pulsed laser holograms, application problems and result interpretation thermal analysis principles and procedures, production of ultrasonic waves by lasers, and ultrasonic interferometric analysis. 53518 Prettyman, T J-L; Gardiner, R.P.; Russ, J.C.; Verghese, K. A c o m b i n e d transmission a n d scattering tomographic approach
to composition and density imaging Applied Radiation and Isotopes, Vol. 44, No. 10-1 l, pp. 1327-1341 (Oct.-Nov. 1993) A method of imaging the composition and density of industrial samples by combining information obtained from a transmission tomographic scanner and a projective. Compton scatter imaging system is described. A reconstruction algorithm with attenuation and multiple scatter correction capabilities is developed around a detailed model of the Compton scatter imaging system. Monte Carlo simulation is used to generate realistic data for the determination of model parameters, the analysis and design of device components, and for testing the reconstruction algorithm. 52240 Gusev, E.A.; Potapov, V.N.; Karpelson, A.E. Analysis of the characteristics of scanning inspection systems using hackscattering Russian Journal of Nondestructive Testing, Vol. 28, No. 8, pp. 505-509 (Apr. 1993) The characteristics of a Compton scanner giving information on the structure of the inspected article from recording x-ray backscattering are analysed on the basis of information obtained by the Monte Carlo method. Methods of selecting the geometric parameters and energy of the x-ray source are examined and the maximum sensitivity and frequency-contrast characteristics of the giver, inspection system are evaluated.
54011
Jensen, T.; Gray, J.N. Material thickness measurements using Compton backscatter
51969 Anon Structural investigation of a damaged GRP/foam sandwich composite using x-ray computed tomography
Review of Progress in Quantitative Nondestructive Evaluation, La Jolla, California (United States), 19-24 Jul. 1992. Vol. 12A, pp. 303-308. Edited by D.O. Thompson and D.E. Chimenti. Plenum Press (1993). ISBN 0-306. ~4A.83-6. Most studies of backscatter for nondestructive inspection have used a conventional bremsstrahlung X-ray source. Which tends to obscure the fine points evident in scattering equations. We have approached this problem by using a monochromatic X-ray source, which allows us to quantitatively compare scattering measurements with predictions. We describe a Monte Carlo model of the X-ray backscatter process and a comparison with experimental measurements.
Australian Institute of Non-Destructive Testing National Conference, Melbourne (Australia), 19-21 Aug. 1991.9pp. AINDT (1991) The construction of the Australian Mine Hunter Inshore (MHI) vessels presents a difficult nondestructive testing (NDT) problem because the nature of the foam core prevents ultrasonic inspection, the application in large panels requires inspection from one side, and for service use the method must be portable to dockyard facilities. Two approaches are being investigated in order to solve this NDT problem. The first method is to demonstrate the capabilities of the x-ray computed tomography (CT). The second approach is to evaluate the Compton backscaUer technique which
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