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Full-Text Articles in Physics

Impact Ignition And Combustion Of Micron-Scale Aluminum Particles Pre-Stressed With Different Quenching Rates, Kevin J. Hill, Nobumichi Tamura, Valery I. Levitas, Michelle L. Pantoya Sep 2018

Impact Ignition And Combustion Of Micron-Scale Aluminum Particles Pre-Stressed With Different Quenching Rates, Kevin J. Hill, Nobumichi Tamura, Valery I. Levitas, Michelle L. Pantoya

Materials Science and Engineering Publications

Pre-stressing aluminum (Al) particles by annealing and quenching alters dilatational strain and is linked to increased particle reactivity. The quenching rate associated with pre-stressing is a key parameter affecting the final stress state within the Al particle, with faster quenching rates theoretically favoring a higher, more desirable stress state. Micron scale Al particles are annealed to 573 K, then quenched at different rates (i.e., 200 and 900 K/min), mixed with bismuth oxide (Bi2O3), and the Al + Bi2O3 mixtures are examined under low-velocity, drop-weight impact conditions. Both quenching rates showed increased impact ignition sensitivity (i.e., between 83% and ...


Phase Field Study Of Surface-Induced Melting And Solidification From A Nanovoid: Effect Of Dimensionless Width Of Void Surface And Void Size, Anup Basak, Valery I. Levitas May 2018

Phase Field Study Of Surface-Induced Melting And Solidification From A Nanovoid: Effect Of Dimensionless Width Of Void Surface And Void Size, Anup Basak, Valery I. Levitas

Physics and Astronomy Publications

The size effect and the effects of a finite-width surface on barrierless transformations between the solid (S), surface melt (SM), and melt (M) from a spherical nanovoid are studied using a phase field approach. Melting (SM → M and S → M) from the nanovoid occurs at temperatures which are significantly greater than the solid-melt equilibrium temperature θe but well below the critical temperature for solid instability. The relationships between the SM and M temperatures and the ratio of the void surface width and width of the solid-melt interface, Δ⎯⎯⎯, are found for the nanovoids of different sizes. Below a critical ratio ...


Fem Modeling Of Plastic Flow And Strain-Induced Phase Transformation In Bn Under High Pressure And Large Shear In A Rotational Diamond Anvil Cell, Biao Feng, Valery I. Levitas, Wanghui Li Jan 2018

Fem Modeling Of Plastic Flow And Strain-Induced Phase Transformation In Bn Under High Pressure And Large Shear In A Rotational Diamond Anvil Cell, Biao Feng, Valery I. Levitas, Wanghui Li

Aerospace Engineering Publications

Combined three-dimensional plastic flow and strain-induced phase transformation (PT) in boron nitride (BN) under high pressure and large shear in a rotational diamond anvil cell (rotational DAC or RDAC) are investigated. Geometrically nonlinear frameworks including finite elastic, transformational, and plastic deformations and finite element method (FEM) are utilized. Quantitative information is obtained on the evolutions of the stress tensor, plastic strain, volume fraction of phases in the entire sample, and slip-cohesion transitions, all during torsion under a fixed compressive load in RDAC. The effects of the applied compressive stress and the sample radius on PT and plastic flow are discussed ...


Triaxial-Stress-Induced Homogeneous Hysteresis-Free First-Order Phase Transformations With Stable Intermediate Phases, Valery I. Levitas, Hao Chen, Liming Xiong Jan 2017

Triaxial-Stress-Induced Homogeneous Hysteresis-Free First-Order Phase Transformations With Stable Intermediate Phases, Valery I. Levitas, Hao Chen, Liming Xiong

Aerospace Engineering Publications

Starting with thermodynamic predictions and following with molecular dynamics simulations, special triaxial compression-tension states were found for which the stresses for the instability of the crystal lattice of silicon (Si) are the same for direct and reverse phase transformations (PTs) between semiconducting Si I and metallic Si II phases. This leads to unique homogeneous and hysteresis-free first-order PTs, for which each intermediate crystal lattice along the transformation path is in indifferent thermodynamic equilibrium and can be arrested and studied by fixing the strain in one direction. By approaching these stress states, a traditional two-phase system continuously transforms to homogenous intermediate ...


Phase Field Simulations Of Plastic Strain-Induced Phase Transformations Under High Pressure And Large Shear, Mahdi Javanbakht, Valery I. Levitas Dec 2016

Phase Field Simulations Of Plastic Strain-Induced Phase Transformations Under High Pressure And Large Shear, Mahdi Javanbakht, Valery I. Levitas

Aerospace Engineering Publications

Pressure and shear strain-induced phase transformations (PTs) in a nanograined bicrystal at the evolving dislocations pile-up have been studied utilizing a phase field approach (PFA). The complete system of PFA equations for coupled martensitic PT, dislocation evolution, and mechanics at large strains is presented and solved using the finite element method (FEM). The nucleation pressure for the high-pressure phase (HPP) under hydrostatic conditions near a single dislocation was determined to be 15.9 GPa. Under shear, a dislocation pile-up that appears in the left grain creates strong stress concentration near its tip and significantly increases the local thermodynamic driving force ...


Phase Field Approach With Anisotropic Interface Energy And Interface Stresses: Large Strain Formulation, Valery I. Levitas, James A. Warren Jun 2016

Phase Field Approach With Anisotropic Interface Energy And Interface Stresses: Large Strain Formulation, Valery I. Levitas, James A. Warren

Aerospace Engineering Publications

A thermodynamically consistent, large-strain, multi-phase field approach (with consequent interface stresses) is generalized for the case with anisotropic interface (gradient) energy (e.g. an energy density that depends both on the magnitude and direction of the gradients in the phase fields). Such a generalization, if done in the “usual” manner, yields a theory that can be shown to be manifestly unphysical. These theories consider the gradient energy as anisotropic in the deformed configuration, and, due to this supposition, several fundamental contradictions arise. First, the Cauchy stress tensor is non-symmetric and, consequently, violates the moment of momentum principle, in essence the ...


Study Of Metal Magnetic Memory (Mmm) Technique Using Permanently Installed Magnetic Sensor Arrays, Zhichao Li, Steve Dixon, Peter B. Nagy, Peter Cawley, Rollo Jarvis Jan 2016

Study Of Metal Magnetic Memory (Mmm) Technique Using Permanently Installed Magnetic Sensor Arrays, Zhichao Li, Steve Dixon, Peter B. Nagy, Peter Cawley, Rollo Jarvis

Review of Progress in Quantitative Nondestructive Evaluation

The Metal magnetic memory (MMM) technique is marketed as a non-destructive testing method to evaluate stress concentration for ferromagnetic materials by measuring variations of the self-magnetic leakage field (SMLF) distribution on the specimen surface. This method has been implemented as a periodic screening inspection tool by several companies, and has been reported to be capable of detecting stress concentration in some instances. However, recent literature has suggested that the performance can be unreliable, with many false-calls; however, the reason for the false calls has not been satisfactorily investigated. In this paper, the normal and tangential components of the stress induced ...


Self-Consistent Swept Frequency Eddy Current Measurements For Characterization Of Near Surface Material Conditions, Chester C.H. Lo, Anatoli M. Frishman, Y. Shen, Norio Nakagawa Jul 2008

Self-Consistent Swept Frequency Eddy Current Measurements For Characterization Of Near Surface Material Conditions, Chester C.H. Lo, Anatoli M. Frishman, Y. Shen, Norio Nakagawa

Center for Nondestructive Evaluation Conference Papers, Posters and Presentations

This paper reports on a self‐consistent, swept frequency eddy current (SFEC) technique for characterizing surface and sub‐surface conditions of materials, with specific applications to detecting residual stresses in shot‐peened Ni‐base superalloys and surface oxidation in engineering components. The technique involves measuring lift‐off normalized vertical component signal to suppress lift off noise and instrumentation effect. Theoretical study shows that the vertical component signals are insensitive to coil dimensions, thus enabling EC measurements in separate frequency bands using multiple coils, while yielding continuous broad‐band data so that both the bulk conductivity and near‐surface conductivity profile ...


A Scaling Law For Nondestructive Evaluation Of Shot Peening Induced Surface Material Property Deviations, Anatoli M. Frishman, Chester C.H. Lo, Y. Shen, Norio Nakagawa Jul 2008

A Scaling Law For Nondestructive Evaluation Of Shot Peening Induced Surface Material Property Deviations, Anatoli M. Frishman, Chester C.H. Lo, Y. Shen, Norio Nakagawa

Center for Nondestructive Evaluation Conference Papers, Posters and Presentations

Shot peening is frequently used to improve mechanical characteristics of metallic components’ surfaces. The physical properties of shot peened surfaces exhibit deviations from their bulk values. This paper shows that there exists a scaling law (universality) among seemingly unrelated material property deviations and among different peening conditions. We present examples and support for scaling behaviors based on experimental data on Almen strip deflection, cold work and residual stress profiles of a shot peened nickel‐base superalloy (Waspaloy), and swept frequency eddy current signals used for NDE studies of another shot peened nickel‐base superalloy (Inconel 718). In addition, a fast ...


Shot-Peening Intensities Vs. Eddy Current Signals As Seen In Iterative Treatment-Measurement Experiment, Norio Nakagawa, Anatoli M. Frishman, Y. Shen, Chester C.H. Lo Jul 2008

Shot-Peening Intensities Vs. Eddy Current Signals As Seen In Iterative Treatment-Measurement Experiment, Norio Nakagawa, Anatoli M. Frishman, Y. Shen, Chester C.H. Lo

Center for Nondestructive Evaluation Conference Papers, Posters and Presentations

We report on progress in a swept high frequency eddy current (SHFEC) technique for characterization of surface residual stress on shot‐peened superalloy surfaces. Our aim here is to demonstrate the sensitivity of our measurement for practical shot peening intensities, i.e. at 4 ∼ 6 A. First, we present our improved probe and instrumentation being sufficiently sensitive to resolve the surface conditions at these low Almen intensities, where our earlier measurements encountered noise problems. The previous coil was also larger (18 mm in diameter) than desirable. Our new probe integrates smaller coils (12 mm in diameter, forming an AC bridge ...


Application Of Diffracto Sight Ot The Nondestructive Inspection Of Aircraft Structures, Jerzy Komorowski, Ronald W. Gould, David L. Simpson, Omer Hageniers Jan 1993

Application Of Diffracto Sight Ot The Nondestructive Inspection Of Aircraft Structures, Jerzy Komorowski, Ronald W. Gould, David L. Simpson, Omer Hageniers

Review of Progress in Quantitative Nondestructive Evaluation

The D Sight optical set up was first assembled nearly ten years ago at Diffracto Ltd. It has received several patents, the first of which was in the United States [1]. Since the mid 1980’s, D Sight has been successfully applied to surface quality inspections, particularly in the automotive and plastics industries. Recently, Komorowski et al. [2–5] have shown several potential applications of D Sight in the field of nondestructive inspection of aircraft structures. The technique has been shown to be particularly effective in locating nonvisible impact damage on large surfaces of aircraft structures built from composite materials ...


Laser Ultrasonic And Photoacoustic Characterization Of Subsurface Structures, Meng-Chou Wu, F. Raymond Parker, William P. Winfree Jan 1993

Laser Ultrasonic And Photoacoustic Characterization Of Subsurface Structures, Meng-Chou Wu, F. Raymond Parker, William P. Winfree

Review of Progress in Quantitative Nondestructive Evaluation

There is a strong interest in applying laser ultrasonic and photoacoustic techniques to the NDE of some high performance structures, for example, the actively cooled panels of the National Aero-Space Plane. Both laser ultrasonic and photoacoustic techniques have been developed for years. Much significant work has been done on either the generation of waves, the mechanisms [1–3] or various techniques for the detection of these waves [4–6]. A few applications being pursued or conducted since the early stage of the development for these techniques [5–7]. However, there is little work concentrating on the interaction of these waves ...


Ultrasonic Propagation Through A Surface With A Step Discontinuity: Validation Of A Hybrid, Gauss-Hermite Ray Tracing Beam Model, M. Greenwood, J.-L. Mai, A. Minachi, I. Yalda-Mooshabad, R. Bruce Thompson Jan 1993

Ultrasonic Propagation Through A Surface With A Step Discontinuity: Validation Of A Hybrid, Gauss-Hermite Ray Tracing Beam Model, M. Greenwood, J.-L. Mai, A. Minachi, I. Yalda-Mooshabad, R. Bruce Thompson

Review of Progress in Quantitative Nondestructive Evaluation

This research continues our cooperative effort to study the effects of large-scale surface roughness on ultrasonic transmission through interfaces and updates our previously-reported results [1], The Center for Nondestructive Evaluation has developed a model for the propagation of ultrasound through a surface and into an isotropic metal and this model is undergoing experimental validation at Battelle PNL. Once validated, this model will be used as an engineering tool to study the effects of surface conditions upon an ultrasonic inspection of nuclear reactor components. The goal is to quantify and develop requirements to limit the adverse effects of surface conditions during ...


Laser Ultrasonics For Coating Thickness Evaluation At 1200°C, H. Ringermacher, F. A. Reed, J. R. Strife Jan 1993

Laser Ultrasonics For Coating Thickness Evaluation At 1200°C, H. Ringermacher, F. A. Reed, J. R. Strife

Review of Progress in Quantitative Nondestructive Evaluation

Laser ultrasonics has come of age in such diverse industrial applications as in-process evaluation during steel processing[1] and composite air frame inspection[2,3]. This approach generally offers certain unique advantages for process evaluation and diagnostics. It is a noncontact, largely contour independent, technique ideally suited for hostile environments.


Crack Detection In Fuselage Panels By A Narrow-Band Laser-Based Ultrasonic System, Jin Huang, Sridhar Krishnaswamy, Jan D. Achenbach Jan 1993

Crack Detection In Fuselage Panels By A Narrow-Band Laser-Based Ultrasonic System, Jin Huang, Sridhar Krishnaswamy, Jan D. Achenbach

Review of Progress in Quantitative Nondestructive Evaluation

Surface acoustic waves can be used for the characterization of mechanical properties of materials, as well as to investigate the near-surface region of a solid for cracks and other flaws by probing for the presence of scattering sources. In the non-destructive characterization of solids, laser generation of ultrasound as well as interferometric detection of the surface waves are particularly attractive in view of the non-contacting nature of such systems. In recent studies, accurate detection of surface wave speed and attenuation have been shown to be possible by the use of dual-probe laser interferometers[1,2]. A number of authors have ...


Laser Ultrasonic Inspection Of Honeycomb Aircraft Structures, F. P. Chang, T. E. Drake, M. A. Osterkamp, Jean-Pierre Monchalin, R. Heon, P. Bouchard, C. Padioleau, D. A. Froom, W. Frazier, J. Barton Jan 1993

Laser Ultrasonic Inspection Of Honeycomb Aircraft Structures, F. P. Chang, T. E. Drake, M. A. Osterkamp, Jean-Pierre Monchalin, R. Heon, P. Bouchard, C. Padioleau, D. A. Froom, W. Frazier, J. Barton

Review of Progress in Quantitative Nondestructive Evaluation

Ultrasonic methods have been used extensively for the inspection of advanced composite materials and adhesively bonded structures. Conventional ultrasonic inspections usually require couplants to propagate ultrasonic waves to and from the part surface. Delaminations, porosities, and foreign inclusions in composite laminates can be successfully detected by pulsed-echo and through-transmission modes of ultrasonic inspection. Debonds in adhesively bonded structures are most effectively detected by the through-transmission mode of ultrasonic inspection.


Solid Rocket Motor Nde Using Nuclear Magnetic Resonance, Lowell Burnett, Dale R. Mckay, Erik M. Magnuson, E. J. Vanderheiden Jan 1993

Solid Rocket Motor Nde Using Nuclear Magnetic Resonance, Lowell Burnett, Dale R. Mckay, Erik M. Magnuson, E. J. Vanderheiden

Review of Progress in Quantitative Nondestructive Evaluation

Solid rocket motors (SRMs) are complex integrated structures. An integral part of an SRM is the adhesive liner, which is used to bond the propellant to the insulator covering the inner surface of the case. In order to ensure SRM performance and reliability, the adhesive liner must be properly cured, of the specified thickness, and free of contamination. The goal of this study is to demonstrate the feasibility of a nuclear magnetic resonance (NMR) method to ensure that these conditions are met.


General Automated Flaw Detection Scheme For Nde X-Ray Images, Karl Ulmer, John P. Basart Jan 1993

General Automated Flaw Detection Scheme For Nde X-Ray Images, Karl Ulmer, John P. Basart

Review of Progress in Quantitative Nondestructive Evaluation

This paper presents an approach to automated flaw detection (AFD) in an arbitrary X-ray image. The intensities in the digitized radiographic image are modeled as piecewise-smooth surface functions corrupted by noise and flaws. It has been observed that radiographs generated for NDE purposes containing flaws also have a combination of three unwanted features; background trends, geometrical structures, and noise. These features inhibit the performance of automated flaw detection algorithms. The proposed general processing scheme reduces the unwanted features in such a way that candidate flaws within the image can be identified. The proposed scheme is robust and is applicable to ...


X-Ray Computed Tomography For Geometry Acquisition, R. Bossi, A. Crews, G. Georgeson, J. Nelson, J. Shrader Jan 1993

X-Ray Computed Tomography For Geometry Acquisition, R. Bossi, A. Crews, G. Georgeson, J. Nelson, J. Shrader

Review of Progress in Quantitative Nondestructive Evaluation

X-ray computed tomography (CT) uses penetrating radiation measurements from many angles about an object to reconstruct cross sectional images of the object interior [1–2]. The images are two dimensional maps of the X-ray linear attenuation coefficient for small volume elements in the object defined by the effective X-ray beam size. The CT images provide quantitative measures of component feature dimensions and density as related to the linear X-ray attenuation of the material under study.


Computed Tomography Applications In Turbine Engine Overhaul, Ward Rummel, Mark Davis, Rodolfo Garcia Jan 1993

Computed Tomography Applications In Turbine Engine Overhaul, Ward Rummel, Mark Davis, Rodolfo Garcia

Review of Progress in Quantitative Nondestructive Evaluation

The United States Air Force has an initiative for technology development and implementation in design, production, acceptance and maintenance overhaul operations. As a part of this initiative, an x-ray computed tomography capability was acquired for use in the support of aircraft structures and gas turbine engine overhaul applications at Kelly Air Force Base, Texas. Implementation of the technology into the Kelly work flow has required acquisition of the knowledge and skills required to use the system, and re-analysis of work functions to assess added capability, measurement precision, reliability and productivity. At the same time, the nature of the data / information ...


Development And Application Of Local 3-D Ct Reconstruction Software For Imaging Critical Regions In Large Ceramic Turbine Rotors, E. Sivers, D. L. Holloway, W. A. Ellingson, J. Ling Jan 1993

Development And Application Of Local 3-D Ct Reconstruction Software For Imaging Critical Regions In Large Ceramic Turbine Rotors, E. Sivers, D. L. Holloway, W. A. Ellingson, J. Ling

Review of Progress in Quantitative Nondestructive Evaluation

Current 3-D X-ray CT imaging technology is limited in some cases by the size and sensitivity of the X-ray detector. This limitation can be overcome to some degree by the use of region-of-interest (ROI) reconstruction software when only part of a larger object need be examined. However, images produced from ROI data often exhibit severe density shading if they are reconstructed by unaltered 3-D X-ray CT algorithms (called Global methods here). These density artifacts can be so severe that low-contrast features are hidden. Time-consuming methods introduced previously to remedy these artifacts require specialized processing to replace or approximate the missing ...


Electronic Holography And Shearography Nde For Inspection Of Modern Materials And Structures, J. Clarady, M. Summers Jan 1993

Electronic Holography And Shearography Nde For Inspection Of Modern Materials And Structures, J. Clarady, M. Summers

Review of Progress in Quantitative Nondestructive Evaluation

Coherent optical techniques such as holography, shearography, and ESPI have been available for inspection applications for years. However, they are still not well known or widely used. In fact, they have sometimes been described as “a solution looking for a problem” and like so many new technologies, they may have been somewhat oversold. These optical NDE methods do, however, offer some impressive advantages over more conventional inspection techniques for the right applications. It is the intent of this paper to provide some basic information on how two of these optical methods, holography and shearography, work discuss capabilities and limitations of ...


Electronic Shearography: Current Capabilities, Potential Limitations, And Future Possibilities For Industrial Nondestructive Inspection, John Deaton Jr., Robert S. Rogowski Jan 1993

Electronic Shearography: Current Capabilities, Potential Limitations, And Future Possibilities For Industrial Nondestructive Inspection, John Deaton Jr., Robert S. Rogowski

Review of Progress in Quantitative Nondestructive Evaluation

Image-shearing speckle pattern interferometry, more commonly referred to as ‘shearography’, is a full-field, laser-based interferometric technique first developed for applications in experimental mechanics [1,2]. Shearography is sensitive to derivatives of the out-of-plane surface displacement of a body under load, as opposed to other full-field methods such as holographic interferometry and conventional speckle pattern interferometry, which typically contour the surface displacement directly [3]. The early shearography experiments used high-resolution photographic film to record images of the laser speckle patterns. In contrast to traditional film-based techniques, electronic shearography uses an electronic camera for image recording [4]. This technology, commercially available for ...


Quantitative Analysis Of A Class Of Subsurface Cracks Using Shearography And Finite Element Modeling, Leland Melvin, Brooks A. Childers, James P. Fulton Jan 1993

Quantitative Analysis Of A Class Of Subsurface Cracks Using Shearography And Finite Element Modeling, Leland Melvin, Brooks A. Childers, James P. Fulton

Review of Progress in Quantitative Nondestructive Evaluation

The application of a full field non-contacting measurement system for nondestructively evaluating (NDE) subsurface flaws in structures has been conducted using Electronic Shearography. Shearography has primarily been used as a qualitative tool for locating areas of stress concentration caused by anomalies in materials[1–4]. NASA has been applying optical techniques such as these to NDE inspection of aircraft lap joint integrity, composite material defects, and pressure vessel quality assurance. This paper examines a special class of defects manufactured in thin metal panels and serves as a testbed for interpreting the displacement gradients produced on a simple well-characterized sample with ...


Laser Shearographic Testing Of Foam Insulation On Cryogenic Fuel Tanks, Douglas Burleigh, James E. Engel, David R. Kuhns Jan 1993

Laser Shearographic Testing Of Foam Insulation On Cryogenic Fuel Tanks, Douglas Burleigh, James E. Engel, David R. Kuhns

Review of Progress in Quantitative Nondestructive Evaluation

The Centaur is a high-energy rocket used as a second stage to the Atlas launch vehicle. The Centaur is cryogenically fueled, using liquid hydrogen and liquid oxygen, and requires insulation to prevent fuel boiloff prior to launch. The original insulation system used on Centaur is a set of fiberglass honeycomb panels, which are jettisoned after launch. These panels are still used on the Atlas I version of Atlas/Centaur.


Shearography With Syncrhonized Pressure Stressing, Tom Chatters, Bruno Pouet, Sridhar Krishnaswamy Jan 1993

Shearography With Syncrhonized Pressure Stressing, Tom Chatters, Bruno Pouet, Sridhar Krishnaswamy

Review of Progress in Quantitative Nondestructive Evaluation

Non-destructive evaluation (NDE) techniques of optical video-based speckle interferometry are gaining importance as inspection tools, particularly by the aerospace industry [1,2]. An optical technique such as shearography is attractive to the NDE community largely because of its non-contacting nature, full-field measurement and fast inspection results. However, in order for this optical interferometric method to become widely used as an NDE tool, this technique must be made to be robust enough to operate in noisy environments typically found in industry settings. In this paper, we address these issues for the case of detection of disbonds using shearography in conjunction with ...


Practical Estimates Of The Errors Associated With The Governing Shearography Equation, John Fulton, M. Namkung, L. D. Melvin Jan 1993

Practical Estimates Of The Errors Associated With The Governing Shearography Equation, John Fulton, M. Namkung, L. D. Melvin

Review of Progress in Quantitative Nondestructive Evaluation

In a series of papers Hung[1–3] pioneered the development of shearography, an optical NDE technique that detects gradients of surface displacements. Its utility for qualitative flaw characterization has been demonstrated, and while there is a need for using shearography in NDE for quantitative analysis, a large amount of the research[2–7] has concentrated on the qualitative evaluation of structures and materials. The purpose of this paper is to begin building upon a foundation for the newly emerging quantitative shearography[8].


Development Of A Neutron Radiography Simulation Model, Troy Groth, Joseph Nahum Gray Jan 1993

Development Of A Neutron Radiography Simulation Model, Troy Groth, Joseph Nahum Gray

Review of Progress in Quantitative Nondestructive Evaluation

Measurement models of NDE techniques have been developed with the purpose of proving the capabilities of NDE techniques for finding flaws. The models take NDE parameters such as ultrasonic frequency, probe diameter, and angle of incidence, and predict the response from the flaw. Models are also a part of quantitative NDE, i.e., the ability to size and characterize flaws and or materials.


Application Of The X-Ray Measurement Model To Image Processing Of X-Ray Radiographs, E. Siwek, Joseph Nahum Gray Jan 1993

Application Of The X-Ray Measurement Model To Image Processing Of X-Ray Radiographs, E. Siwek, Joseph Nahum Gray

Review of Progress in Quantitative Nondestructive Evaluation

A computational model has been developed at which simulates the film response to the interaction of x-rays with a sample[1,2]. By using a CAD model as a virtual part, film densities of the radiograph are predicted. The number of photons which reach the film is based on the thickness of the part, part geometry, and the material absorption coefficient. Also taken into consideration are the x-ray beam characteristics, film properties, and the experimental configuration. The model generated images can vary in size and resolution, depending on the user chosen parameters. Noise is calculated using a Gaussian noise distribution ...


Material Thickness Measurements Using Compton Backscatter, T. Jensen, Joseph Nahum Gray Jan 1993

Material Thickness Measurements Using Compton Backscatter, T. Jensen, Joseph Nahum Gray

Review of Progress in Quantitative Nondestructive Evaluation

As the age of airplanes in the commercial fleet has increased, inspection and maintenance costs have steadily increased. The fact that aircraft have a fairly complicated structure and operate under a wide range of environmental conditions means that detection of the onset of structural deterioration is often difficult. In particular, corrosion of aluminum structures may begin on interior layers and be visually evident only at fairly advanced stages. Present maintenance requirements dictate that airplane skin (typical thickness 1mm) must be repaired if more than 10% thickness of the material has corroded[l]. A number of nondestructive inspection techniques are being ...