51473 High energy, high resolution monochromatic x-ray computed tomography system

ND T Abstracts poles is usually an invasive, imprecise, and indirect process. A prototype field-transportable x-ray computerized tomography scanner has been constructed to allow the internal structure of poles up to 450 mm across to be obtained in the form of cross-sectional images of mass density. The technique is totally nondeslructive. 52218 Suendermann, B. Structural investigation of a damaged GRP/foam sandwich composite using x-ray computed tomography Non-Destructive Testing-Australia, Vol. 29, No. 5, pp. 130-132 (Sep.- Oct. 1992) The results presented in this paper show that conventional medical CT body scanners can characterise, in fine detail, small sections of the GRP/foam sandwich composite material used in the hulls of Inshore vessels. The method shows an ability to identify non-uniform density in foam panels, cracks and small defects down to a scale of approximately 1 mm in the composite material. Application of the technique to large slructures requires assessment of the sizes of the defects which can be tolerated and the degree to which images can be reconstructed using a more restricted data set, considering that one- sided inspection may be necessary. 52216 Wells, P.; Davis, J. The role of tomography and densitometry in the nondestructive testing and evaluation o f wood Non-Destructive Testing-Australia, Vol. 29, No. 6, pp. 162-165,172 (Nov.-Dec. 1992) X-ray computed tomography (CT) is able to provide a full three dimensional internal view of an object without destruction. CT can provide structural information at a scale ranging from many centimeters down to micrometers. The actual physical variable measured with this technique is the X-ray linear attenuation coefficient. The aim of this paper is to discuss some of the results available from the CT technique applied to wood. 51975 Osier, R. C o m p u t e d t o m o g r a p h y (CT) as a nondestructive test method used for composite helicopter components Messerschmitt-Boelkow-Blohm, Munich (Germany) TIB/B9201178/GAR, 8pp. (1991) New developments in rotor components, e.g. the rotor-blade technology of the Bo108 and PAH2 programs, make use of very complex fiberreinforced structures to achieve simplicity and strength. Computed tomography has been found to be an outstanding nondestructive test method for examining the internal structure of components. ACT scanner generates X-ray attenuation measurements which are used to produce computerreconstructed images of any desired part of an object. This contribution reports on several CT investigations and their results, taking composite helicopter components as an example. 51969 Anon Structural investigation of a damaged GRP/foam sandwich composite using x-ray computed tomography 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 backscatter technique which uses one-sided imaging and promises equipment which is deployable to the field in the near future. This present work describes the CT imaging of a GRP/foam composite from the MHI, and takes advantage of underwater blast test panels which are available and contain typical shock induced defects in the foam.

Grant, J.A.; Morgan, M d.; Davis, J.R., Davies, D.R.; Wells, P,

51726

X-ray diffraction m i c r o t o m o g r a p h y Measurement Science and Technology, Vol. 4, No. 1, pp. 83-87 (1993) A table-top system has been developed for tomographic imaging of the internal structure of objects of low mass density at sub-millimetre resolution. Images are based on the x-ray diffraction properties of constituent materials, and are reconstructed from tomographic data using summation-filtered back-projection. Typical images are presented, the apparatus used for data acquisition is described, and the application of summation-filtered back-projection is discussed.

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51724 Breunig,T.M.; Stock, S.R.; GuvenUir, A.; Elliott, J.C.; Anderson, P.; Davis, G.R. Damage in aligned-fibre SiC/AI quantified using a laboratory X-ray tomographic microscope Composites, Vol. 24, No. 3, pp. 209-213 (1993) A fn'st-generafion laboratory X-ray tomographic microscope is used to nondestructively 'section' a continuous, aligned-fibre SiC/AI metal- matrix composite (MMC). Damage in the MMC associated with mechanical deformation is the principal focus of the study. Two types of deformation are examined: wedge loading (with and without load) and three-point bending. Quantification of crack opening and fibre fracture detection is found to be practical down to one-tenth of a pixel in the reconstructed sections. 51722 Gopalsami,N.; Rizo, P.; Ellingson, WA.; Tracey, D.M. Detection sensitivity of x-ray C T imaging fof NDE of greenstate ceramics Review of Progress in Quantitative Nondestructive Evaluation, Brunswick, Maine (United States), 28 Jul.-2 Aug. 1991), Vol. 11B, pp. 1861-1868. Edited by D.O. Thompson and D.E. Chimenti. Plenum Press (1992) Three-dimensional micmfocus X-ray computed tomography (CT) and nuclear magnetic resonance imaging (MR) systems have been developed at Argonne National Laboratory (ANL) for appfication to quantitative NDE evaluation of ceramics. This paper evaluates the detection sensitivity of the ANL X-ray CT system when used to determine density gradients, inclusions, and voids in green-state SiN ceramics. A theoretical account of key system-and sample-related parameters affecting X-ray CT detection sensitivity is given, and results of experimental evaluation are presented. 51476 Breunig,T.M. Nondestructive evaluation of damage in SiC/AI metal matrix composite using X-ray tomographic microscopy Dissertation Abstracts International, Vol. 53, No. 4, p. 2007-B (Oct. 1992) The goal of the present work is to improve the understanding of damage accumulation in SiC/AI using a new microscopic nondestructive volumeimaging technique, X-ray Tomographic Microscopy (XTM), which has resolution comparable to optical microscopy. Correlation of damage initiation and accumulation mechanisms and the macroscopic mechanical response of samples are discussed for continuous fiber SiC/AI MMC's. The types of damage detected include: fiber fracture (SiC sheath and C core), fiber-matrix interface microcracking, intra-ply malrix voids and cracks. Quantitative three-dimensional measurements of damage are reported in as-fabricated, monotonically loaded and mechanically fatigue loaded SiC/AI. 51475 Tonner,P.D.; Stanley, Jdt. Supervoltage computed tomography for large aerospace structures Materials Evaluation, Vol. 50, No. 12, pp. 1434-1438,1445 (Dec. 1992) The scientific and technical feasibility of computer tomography (CT) imaging with "supervoltage" x-rays from a 60-MeV linear accelerator has been demonstrated. The 60-MeV energy is required to obtain sufficient penetration of large, highly attenuating objects and has practical significance because pair production causes x-ray attenuation to increase without bound for x-ray energies beyond this limit. Thus, supervoltagn CT (SVC'D represents the upper limit of CT technology in terms of object size and penetrability. These experiments used a test phantom radiographically equivalent to a solid rocket motor of 3.9 mdia. Very subtle features in the phantom, such as fin tip cracks and density irregularities, are reproducibly imaged. Density differences as small as one to two percent between samples of graphite, propellant, and even water at 20C and 80C, were accurately measured, demonstrating that, in addition to being able to measure densities over a wide dynamic range, SVCT is also extremely sensitive to very small density differences anywhere within that range. 51473 Nagata, Y.; Yamaji, H.; Hayashi, K.; Kawahima, K.; Hyodo, K.; Kawata, H.; Ando, M. High energy, high resolution monochromatic x-ray computed tomography system Research in Nondestructive Evaluation, Vol. 4, No. 2, pp. 55-78 (1992) We have developed a high energy, high resolutionmonochromatic x-ray computed tomography system using synchro1~'on radiation.Our system is installedin a verticalwiggler beamline at the Photon Factory of the National Laboratory for High Energy Physics thatcan produce high brilliancex-rays

ND T Abstracts in the high energy region. At the present stage, we have obtained monochromatic x-rays up to 75 keV, succeeded in taking computed tomography images of materials up to 50 keV with large absorption coefficients that could not be imaged by conventional methods, and observed three-dimensionni fine structures in such materials. When the K-edge subtraction method was applied, the system could quantitatively and nondesWactively measure the trace distribution of a specific element in the object of interest. In this paper we introduce the experimental system, mainly the crystal monochromator, evaluate the results, and discuss the performance of the system.

Rheinlander, J.; Lindegaard-Andersen, A.; B~hlin, Y. Evaluation of performance of a film-based x-ray tomographic 51472

system Research in Nondestructive Evaluation, Vol. 4, No. 2, pp. 97-107

(1992) The performance of a home-made tomographic system for film-based rotational X-ray tomngraphy is evaluated by comparison of calculated intensity profiles to measured film density profiles within tomngrams of aluminium test objects with small implemented defects. The calculated intensity profiles have been obtained using the back- projection and summation method, calculating-the linear absorption coefficient by integrating over the entire energy spectrum of the applied microfocus X-ray set. It is shown that the logarithmic response of the X-ray film must be taken into account when relating intensity profiles to film-density units. The resulting calculated film density profiles nicely fits the actually measured profiles, indicating a low total unsharpness. It is concluded that the method is capable of resolving voids down to about 25 pro. However, due to the inherent blurting of the method, image processing techniques must be applied. 51468 Jensen, T.; Gray, J. M o n o c h r o m a t i c x-ray beams for NDT Review of Progress in Quantitative Nondestructive Evaluation, Brunswick, Maine (United States), 28 Jul. - 2 Aug. 1991. Vol. 11A, pp. 339-345. Edited by D.O. Thompson and D.E. Chimenti. Plenum Press (1992) In this report we present preliminary results from studies of monochromatic x-ray beams generated using a graphite crystal. In the following section we describe the experimental apparatus and the properties of the monochromatic beam. We follow that with examples of applications of this technique in characterization of detectors, measurement of attenuation coefficients, and computed tomography.

51464 Sire, P.; Rizo, P.; Martin, M.; Grangeat, P.; Morisseau, P. Development of an advanced 3D cone beam tomographic system Review of Progress in Quantitative Nondestructive Evaluation, Brunswick, Maine (United States), 28 Jul. - 2 Aug. 1991. Vol. 11A, pp. 371-378. Edited by D.O. Thompson and D.E. Chimenti. Plenum Press (1992) LETI has been working on a new generation of 3D x-ray CT machine for manyyears. After a presentation of the project partners, we briefly recall the principle of the 3D x-ray CT, then we describe the general design of the device and the few tasks performed by the machine to provide a reconstructed volume. Finally, we show some actual data acquired by the system.

51463 Rizo, P.; Grangeat, P.; Sire, P.; Le Masson, P.; Delageniere, S. X-ray cone beam t o m o g r a p h y with two tilted circular trajectories Review of Progress in Quantitative Nondestructive Evaluation, Brunswick, Maine (United States), 28 Jul. - 2 Aug. 1991. Vol. I IA, pp. 379-386. Edited by D.O. Thompson and D.E. Chimenti. Plenum Press (1992) Recently 3-D cone-beam tomography has become of interest for the nondestructive evaluation of advanced materials. Until now, most of the experiments presented in the literature were performed with a planar source trajectory. Recently, a new method presented by Smith has been applied to nonplanar source trajectories by Kudo and Saito. The inversion presented by Kudo uses the Hilbert transform of the first derivative of the Radon transform. This inversion has been experienced with real data on two circular trajectories at 90sup(o) with intersection of the two axis of the trajectories (orthogonal scan). We have presented reconstructions on simulated with double circular source trajectories with an exact reconstruction method using the inversion of the first derivative of the 3-D Radon transform. These simulations were performed with an angle smaller

than 90sup(o) between the two trajectories. Here we quantify the advantages of this method and we present experimental reconstruction in this implementation. We show also that according to the Radon space sampling, the axes of the two trajectories do not have to intersect, but they must be close enough. 51461 Georgeson,G.; Bossi, R.; ODell, L.; Lorsbach, G.; Nelson, J. Correlation of x-ray CT measurements to shear strength in pultruded composite materials Review of Progress in Quantitative Nondestructive Evaluation, Brunswick, Maine (United States), 28 Jul. - 2 Aug. 1991. Vol. 11A, pp. 395-402. Edited by D.O. Thompson and D.E. Chimenti. Plenum Press (1992) Pultrusion is an emerging, economical manufacturing process for composite structures. Destructive testing, such as shear testing of small sections, is the normal method for assessing the quality of the pulU'usion manufacturing product. X-ray computed tomography (CT) is a nondestructive method to measure material density/constituents and displays the information as a map of the relative linear X-ray attenuation coefficients of small volume elements in a cross section of a sample. The mean CT value in a composite material and the standard deviation of that value in the small image elements are directly related to the material density and the density variation present. These measurements are related to the fiber/resin ratio of the composite and the consolidation, which affect the overall strength. CT data can be readily obtained over many regions to map the material quality throughout a sample. By correlating CT measurements to destructive shear strength measurements, it is possible to reduce the need for destructive sampling and provide on-line measurement of product

quality.

51460 Bossi, R,; Crews, A.; Nelson, J. Measurement of the center-of-gravity using x-ray computed tomography Review of Progress in Quantitative Nondestructive Evaluation, Brunswick, Maine (United States), 28 Jul. - 2 Aug. 1991. Vol. 11A, pp. 403-408. Edited by D.O. Thompson and D.E. Chimenti. Plenum Press (1992) The quantitative capability of CT to measure the relative X-ray linear attenuation coefficient and position of small volume elements in a component also offers the potential to perform center-of-gravity (CG) measurements for rotating systems. Currently, the practice of engine vibration reduction is one of disassembly, iteratively checking balance and grinding off mass until the amount of imbalance is acceptable. In order to address the potential of CT to be used in the balancing of a complex system, such as a jet engine assembly, it is necessary to determine the capabilities of CT to accurately locate the CG of a part from CT dam. In an initial experiment, the ability to measure the CG of a test phantom to better than 0.8 g-cm indicates that accuracies suitable to small jet engine testing can be achieve under controlled conditions. 51459 Kropas, C.V.; Hughes, M.E. Computed tomography imaging for nondestructive evaluation Review of Progress in Quantitative Nondestructive Evaluation, Brunswick, Maine (United States), 28 Jul. - 2 Aug. 1991. Vol. 11A, pp. 409-415. Edited by D.O. Thompson and D.E. Chimenti. Plenum Press (1992) This paper will present examples of CT imaging as an NDE tool in some aerospace and industrial application areas. It will also show some research efforts that insert CT into the in-process evaluation of new materials, and some experimental work to evaluate the optimum performance of the CT machine. The system used for all the CT imaging contained in this paper was the LAMDE CT System located at Wright Laboratory, Wright-Patterson AFB, Ohio. The LAMDE CT System is a translate-rotate type CT machine with a 420 keV X-ray tube source. The system can examine components up to 600 mm in diameter and 500 pounds. 51458 Roberts, RA. Limited data tomography using support minimization with a priori data R e v i e w of Progress in Quantitative Nondestructive Evaluation, Brunswick, Maine (United States), 28 Jul. - 2 Aug. 1991. Vol. 11A, pp. 749-756. Edited by D.O. Thompson and D.E. Chimenti. Plenum

Press (1992) This paper addressesthe reconstruction of incomplete projection data such as obtained in limited angle X-ray tomography, including cases where a priori object geometry information is available. The focus of the research is on the prescription of appropriate functional measures, and in particular

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