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Articles 1 - 14 of 14

Full-Text Articles in Physics

Secondary Radiation Influence On Lsf Shapes In Radiography, A. Notea, Y. Bushlin, Y. Feldman Jan 1992

Secondary Radiation Influence On Lsf Shapes In Radiography, A. Notea, Y. Bushlin, Y. Feldman

Review of Progress in Quantitative Nondestructive Evaluation

A radiographic image is generated by both primary and secondary radiations. In a previous study [1, 2] the influence of secondary radiation on the generated image was shown for square based blocks of finite dimensions (few mean free paths). The response to a step change in the block’s thickness, varies drastically with the step location relative to the block’s edges [3]. However, even when the radiographed object is large and the step response is studied far off the object’s limits, the effect of the secondary radiation is still significant. This radiation distorts the “ideal” step response shape ...


Development Of An Advanced 3d Cone Beam Tomographic System, P. Sire, Philippe Rizo, M. Martin, P. Grangeat, P. Morisseau Jan 1992

Development Of An Advanced 3d Cone Beam Tomographic System, P. Sire, Philippe Rizo, M. Martin, P. Grangeat, P. Morisseau

Review of Progress in Quantitative Nondestructive Evaluation

While 2D x-ray CT is now commonly used for NDT applications, the interest in 3D x-ray cone beam tomography has significantly increased over the last few years [1,2]. The need to reduce acquisition time for industrial applications, or radiation dose to patients for medical applications, led engineers to develop a new type of tomograph using x-ray beams more efficiently. Thanks to a high spatial resolution, the 3D x-ray CT allows greater knowledge of the object structure. This understanding is necessary to study and improve industrial production of high technology materials. Therefore, 3D x-ray CT is well suited for the ...


X-Ray Cone Beam Tomography With Two Tilted Circular Trajectories, Philippe Rizo, Pierre Grangeat, Pascal Sire, Patrick Le Masson, Solange Delageniere Jan 1992

X-Ray Cone Beam Tomography With Two Tilted Circular Trajectories, Philippe Rizo, Pierre Grangeat, Pascal Sire, Patrick Le Masson, Solange Delageniere

Review of Progress in Quantitative Nondestructive Evaluation

Recently 3-D cone-beam tomography has become of interest for the nondestructive evaluation of advanced materials. The main field of application in nondestructive testing is the evaluation of structural ceramics. Study of such materials implies high density resolution and high sensitivity to cracks. In fact, with a single circular source trajectory, when the cone-beam aperture increases, density is underestimated and cone shaped artifacts may appear at interfaces in the sample even at relatively small aperture [1–3]. These artifacts limit the thickness we can examine with a planar source trajectory. To maintain optimal reconstruction accuracy with a circular source trajectory, the ...


Quantitative Nondestructive Density Determinations Of Very Low-Density Carbon Foams, W. Anthony E. Moddeman, D. P. Kramer, D. W. Firsich, P. D. Trainer, P. S. Back, S. D. Smith, W. R. Deal, R. F. Salerno, F. A. Koeler, M. E. Hughes Jan 1992

Quantitative Nondestructive Density Determinations Of Very Low-Density Carbon Foams, W. Anthony E. Moddeman, D. P. Kramer, D. W. Firsich, P. D. Trainer, P. S. Back, S. D. Smith, W. R. Deal, R. F. Salerno, F. A. Koeler, M. E. Hughes

Review of Progress in Quantitative Nondestructive Evaluation

Carbon foams have been manufactured at EG&G Mound Applied Technologies through the use of a salt replica process [1,2] that has been modified by a Mound propriety process [3]. Applications of these foams have been described in an early publication [4]. In the basic process [1,2] of manufacturing the foams, salt is pressed into bars; the bars are then cured, infused with polymer and cured again. The salt is then removed by copious solvent rinsings and finally carbonized into very porous and light-weight, briquette-like material [2,5]. In this paper, the carbon density and the carbon distribution in various foams were determined either by bulk measurements of weight and volume or by x-ray computed tomography (CT).


Correlation Of X-Ray Ct Measurements To Shear Strength In Pultruded Composite Materials, G. Georgeson, R. Bossi, L. O'Dell, G. Lorsbach, J. Nelson Jan 1992

Correlation Of X-Ray Ct Measurements To Shear Strength In Pultruded Composite Materials, G. Georgeson, R. Bossi, L. O'Dell, G. Lorsbach, J. Nelson

Review of Progress in Quantitative Nondestructive Evaluation

Pultrusion is an emerging, economical manufacturing process for composite structures. In a pultrusion system, the composite tapes and fabrics are loaded onto a creel, and the materials are fed into a preform (or shaper), along with any fillers that may be needed. If the fiber is not yet preimpregnated with resin, it is run through a resin bath or resin is injected into the die the material is about to enter. The composite is pulled through the heated die and then cut from the system to produce either a fully or partially cured product. This handleable part is then placed ...


Measurement Of The Center-Of-Gravity Using X-Ray Computed Tomography, R. Bossi, A. Crews, J. Nelson Jan 1992

Measurement Of The Center-Of-Gravity Using X-Ray Computed Tomography, R. Bossi, A. Crews, J. Nelson

Review of Progress in Quantitative Nondestructive Evaluation

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. This process is labor intensive. An alternative nondestructive method to measure the CG prior to disassembly could provide a cost effective method to minimize the labor effort in balancing operations.


Computed Tomography Imaging For Nondestructive Evaluation, Claudia V. Kropas, Michael E. Hughes Jan 1992

Computed Tomography Imaging For Nondestructive Evaluation, Claudia V. Kropas, Michael E. Hughes

Review of Progress in Quantitative Nondestructive Evaluation

X-ray Computed Tomography (CT) is a relatively new Nondestructive Evaluation (NDE) technique in industry. Traditional Radiography or Digital Radiography is a data acquisition technique where the full volume information is superimposed in an overlapping fashion on a two-dimensional image. In contrast, CT gathers full volume data at a specified plane in the object and, in software, ‘reconstructs’ the cross-sectional image of the object, removing all superpositioning of overlapping information.


Coherent X-Ray Imaging For Corrosion Evaluation: A Preliminary Assessment, Larry Lawson Jan 1992

Coherent X-Ray Imaging For Corrosion Evaluation: A Preliminary Assessment, Larry Lawson

Review of Progress in Quantitative Nondestructive Evaluation

Corrosion products sometimes complicate the task of measuring metal loss. For example, in layered joints in aircraft, the products of corrosion usually remain trapped between layers. Their presence interferes with ultrasonic and x-ray measurements. Recently, Compton backscatter tomography has been suggested as a means of measuring the amount of metal loss resulting from corrosion. This x-ray method is appealing in that it is one-sided. However, no successful results seem to be yet reported. Suggested reasons for this have included long counting times [1] and poor contrast between metal and corrosion products [2]. Both these problems are related to the high ...


Point Spread Function Estimation Of Image Intensifier Tubes, Edward R. Doering, Joseph Nahum Gray, John P. Basart Jan 1992

Point Spread Function Estimation Of Image Intensifier Tubes, Edward R. Doering, Joseph Nahum Gray, John P. Basart

Review of Progress in Quantitative Nondestructive Evaluation

Real-time radiography systems employing an image intensifier tube have poor resolution (2 to 4 Ip/mm) compared to their film-based counterparts (10 to 20Ip/mm). Phosphor bloom, especially in the output conversion phosphor [1], is the principle cause of reduced resolution. Other systems achieve higher resolution but at the expense of additional hardware complexity [2] or use of expensive materials [3]. We are investigating software-based image restoration techniques that can cost-effectively recover resolution from existing image intensifier tube-based systems.


Measurement Of Internal Residual Strain Gradients In Metal Matrix Composites Using Synchrotron Radiation, Todd A. Kuntz, Haydn N.G. Wadley, David R. Black Jan 1992

Measurement Of Internal Residual Strain Gradients In Metal Matrix Composites Using Synchrotron Radiation, Todd A. Kuntz, Haydn N.G. Wadley, David R. Black

Review of Progress in Quantitative Nondestructive Evaluation

Low density titanium based metal matrices combined with high strength and stiffness ceramic fibers are under widespread investigation for possible use in high temperature aerospace applications [1]. Inherent in the processing of these composite materials are the residual stresses resulting from the thermal expansion coefficient mismatch between the fiber and matrix. A tensile hoop and a compressive radial stress result upon cooling from the consolidation temperature because the fiber has a smaller expansion coefficient [2]. The thermal stresses can be very large and may exceed the matrix yield or even fracture stress [3].


Unfocused Source Of X-Rays In A Microfocus X-Ray Tube, W. Anthony D. Friedman Jan 1992

Unfocused Source Of X-Rays In A Microfocus X-Ray Tube, W. Anthony D. Friedman

Review of Progress in Quantitative Nondestructive Evaluation

In an ideal microfocus X-ray tube all the radiation would emanate from a single point, typically 10µm or less in diameter. The intensity would also be independent of angle within the cone beam that is defined by apertures within the tube. Such a tube would have high resolution due to the small spot size, and the uniform distribution of X-ray photons on the detector plane would make it useful for measuring density variations in flat samples such as ceramic modulus of rupture (MOR) bend test bars. Koenigsberg and Cotter [1] have shown that there are additional sources of X-rays in ...


Performance Modeling Of Scintillator-Based X-Ray Imaging Systems, G. A. Mohr, W. T. Tucker, M. K. Cueman Jan 1992

Performance Modeling Of Scintillator-Based X-Ray Imaging Systems, G. A. Mohr, W. T. Tucker, M. K. Cueman

Review of Progress in Quantitative Nondestructive Evaluation

We recently have been involved in developing x-ray detector systems for industrial NDE applications. A two-step process is commonly used to convert the x-ray flux transmitted through the part under test into a digitized image, with individual pixel values corresponding to the x-ray properties in different regions of the part. First, a scintillator material absorbs x rays and emits light in proportion to the amount of x-ray energy absorbed. Second, this light is converted into an electronic signal by a photodetector device. This electronic signal can then be digitized and stored in a computer system for image display and analysis.


Monochromatic X-Ray Beams For Ndt, T. Jensen, Joseph Nahum Gray Jan 1992

Monochromatic X-Ray Beams For Ndt, T. Jensen, Joseph Nahum Gray

Review of Progress in Quantitative Nondestructive Evaluation

The interaction of an x-ray beam from a conventional generator with an object containing more than one type of material is a very complicated process. The shape of the bremsstrahlung spectrum from the generator depends on the target material and orientation, as well as on the inherent filtration and any additional filters through which the beam passes. Absorption of the beam in the part under study varies dramatically with energy and depends critically on the atomic number and density of the material. Thus, interaction of x-rays in an object can provide a great deal of information about the elemental composition ...


The Global Potential Energy Surfaces Of The Lowest Two 1a' States Of The Ozone Molecule: Theoretical Determination And Analysis , Gregory John Atchity Jan 1992

The Global Potential Energy Surfaces Of The Lowest Two 1a' States Of The Ozone Molecule: Theoretical Determination And Analysis , Gregory John Atchity

Retrospective Theses and Dissertations

The two lowest 1A[superscript]' potential energy surfaces (PES) of the ozone molecule are determined and analyzed using accurate ab-initio MCSCF calculations;As appropriate internal coordinates, the shape-scale perimetric coordinates for triatomic molecules are discussed and further developed;Because the previously determined intersection between these two surfaces of like symmetry is unusual, much of the present work involves this intersection. The relevant theory of intersections is reviewed, and a method for characterizing intersections according to the topology of the surfaces in their vicinity is developed;Furthermore, the reasons for this particular crossing in ozone are investigated. The analysis is based ...