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Full-Text Articles in Physics

Nondestructive Residual Strain Measurement Using High Energy X-Ray Diffraction, Mohammad Yousef Al-Shorman Jan 2008

Nondestructive Residual Strain Measurement Using High Energy X-Ray Diffraction, Mohammad Yousef Al-Shorman

Graduate Theses and Dissertations

A nondestructive high energy (60 keV) x-ray diffraction method to measure the internal strain depth-profile in materials was developed using a standard 320 kVp laboratory x-ray source. Traditional x-ray strain measurements are limited to few microns of depth due to the limited penetration of Cu Ka and Mo Ka radiation if a synchrotron or neutron source is not used. The high energy used allows for greater penetration without a synchrotron or neutron facility. Results for aluminum with penetration depths of 1mm and for titanium with penetration depths of 300 micrometers are demonstrated. The spatial resolution of this depth-profile is 50 ...


Crystallography, Anisotropic Metamagnetism, And Magnetocaloric Effect In Tb5si2.2ge1.8, Min Zou, Yaroslav Mudryk, Vitalij K. Pecharsky, Karl A. Gschneidner Jr., Deborah L. Schlagel, Thomas A. Lograsso Jan 2007

Crystallography, Anisotropic Metamagnetism, And Magnetocaloric Effect In Tb5si2.2ge1.8, Min Zou, Yaroslav Mudryk, Vitalij K. Pecharsky, Karl A. Gschneidner Jr., Deborah L. Schlagel, Thomas A. Lograsso

Ames Laboratory Publications

The metamagnetic-like transitions and giant magnetocaloric effect were observed with the magnetic field applied parallel to the aand c axes, but not the b axis in a Tb5Si2.2Ge1.8 single crystal. The in situ x-ray powder diffraction study indicates that these metamagnetic-like transitions are coupled to crystallographic phase transformations occurring via strong magnetoelastic interactions. The magnetocrystalline anisotropy plays an important role in this system. Magnetic fields less than 40 kOe cannot drive either the magnetic or the crystallographic phase transition to completion for Tb5Si2.2Ge1.8 powder due to ...


An Extended Model Of The Barkhausen Effect Based On The Abbm Model, D. M. Clatterbuck, V. J. Garcia, M. J. Johnson, David C. Jiles May 2000

An Extended Model Of The Barkhausen Effect Based On The Abbm Model, D. M. Clatterbuck, V. J. Garcia, M. J. Johnson, David C. Jiles

Ames Laboratory Publications

The Barkhausen model of Alessandro et al. [J. Appl. Phys. 68, 2901 (1990)] has been extended to nonstationary domain walldynamics. The assumptions of the original model limit, its use to situations where the differential permeability, and time derivative of applied field are constant. The later model of Jiles et al. assumes that the Barkhausen activity in a given time interval is proportional to the rate of change of irreversible magnetization which can be calculated from hysteresis models. The extended model presented here incorporates ideas from both of these. It assumes that the pinning field and domain wall velocity behave according ...


Estimation Of Fatigue Exposure From Magnetic Coercivity, Z. J. Chen, David C. Jiles, J. Kameda May 1994

Estimation Of Fatigue Exposure From Magnetic Coercivity, Z. J. Chen, David C. Jiles, J. Kameda

Ames Laboratory Publications

An investigation of the effects of fatigue on A533B steel under constant load amplitude is reported in this paper. It was found that the plastic strain of the sample accumulated logarithmically with the number of stress cycles after initial fatigue softening. Based on the fact that plastic strain is often linearly related to the coercivity of material, at least for small changes of H c , a phenomenological relationship has been developed and tested to correlate the number of stress cycles to this magnetic parameter. This result represents the first successful attempt to relate the fatigue exposure directly to a magnetic ...


Evaluation Of Fatigue Damage In Steel Structural Components By Magnetoelastic Barkhausen Signal Analysis, Madhav Rao Govindaraju, Andrew Strom, David C. Jiles, S. B. Biner, Z. J. Chen May 1993

Evaluation Of Fatigue Damage In Steel Structural Components By Magnetoelastic Barkhausen Signal Analysis, Madhav Rao Govindaraju, Andrew Strom, David C. Jiles, S. B. Biner, Z. J. Chen

Ames Laboratory Publications

This paper is concerned with using a magnetic technique for the evaluation of fatigue damage in steel structural components. It is shown that Barkhausen effect measurements can be used to indicate impending failure due to fatigue under certain conditions. The Barkhausen signal amplitude is known to be highly sensitive to changes in density and distribution of dislocations in materials. The sensitivity of Barkhausen signal amplitude to fatigue damage has been studied in the low‐cycle fatigue regime using smooth tensile specimens of a medium strength steel. The Barkhausen measurements were taken at depths of penetration of 0.02, 0.07 ...


Modeling Of Micromagnetic Barkhausen Activity Using A Stochastic Process Extension To The Theory Of Hysteresis, David C. Jiles, Levent B. Sipahi, G. Williams May 1993

Modeling Of Micromagnetic Barkhausen Activity Using A Stochastic Process Extension To The Theory Of Hysteresis, David C. Jiles, Levent B. Sipahi, G. Williams

Materials Science and Engineering Publications

Recent work by Bertotti [IEEE Trans. Magn. MAG‐24, 621 (1988)] and others has shown that it is possible to model the micromagnetic Barkhausen discontinuities at the coercive point using a two‐parameter stochastic model. However, the present formulation of the model is restricted to limited regions of the hysteresis curve over which dM/dH is approximately constant and whendH/dt is held at a constant rate. A natural extension of this model is to take the basic result, in which the level of Barkhausen activity in one time period is related to the activity in the previous time ...


Comprehensive Analysis Of Barkhausen Emission Spectra Using Pulse Height Analysis, Frequency Spectrum, And Pulse Wave Form Analysis, Levent B. Sipahi, David C. Jiles, D. Chandler May 1993

Comprehensive Analysis Of Barkhausen Emission Spectra Using Pulse Height Analysis, Frequency Spectrum, And Pulse Wave Form Analysis, Levent B. Sipahi, David C. Jiles, D. Chandler

Materials Science and Engineering Publications

The dependence of magnetic Barkhausen emissions (MBE) upon both field excitation and detection frequencies and excitation wave form was studied in order to investigate two of several crucial factors which affect the emissions. Sinusoidal, triangular, and square wave forms were used to generate the MBE and the pulse height spectra, frequency spectra, and pulse wave forms of these signals were analyzed. The frequency spectra of sinusoidal and triangular alternating field excitations showed similar behavior but the spectrum under square wave excitation was different due to the existence of high frequency components during square wave switching. As yet, no common standard ...


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 ...


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 ...


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.


Experiments With Double Microwave Apertures, John Basart, Zhong Zhang Jan 1993

Experiments With Double Microwave Apertures, John Basart, Zhong Zhang

Review of Progress in Quantitative Nondestructive Evaluation

One of the significant characterizations of microwave imaging is the spatial resolution. The relative long wavelength of microwaves as compared to ultrasonic waves and x-rays necessarily means that aperture arrays (real-time or synthetic) are required for high-resolution microwave imaging. Certain limitations on resolution apply regardless of how the array is realized. Types of antenna arrays fall into two broad categories: Phased arrays which are usually operated in real time by scanning a beam past an object, and aperture synthesis in which data are collected with one or more antennas and later processed to produce an image. In NDE we are ...


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 ...


Support Minimized Limited View Ct Using A Priori Data, R. Roberts, O. Ertekin Jan 1993

Support Minimized Limited View Ct Using A Priori Data, R. Roberts, O. Ertekin

Review of Progress in Quantitative Nondestructive Evaluation

This paper reports progress in work on CT reconstruction of incomplete X-ray (Radon) projection sets in situations where explicit object geometry and composition information is available. Previous work on this problem, reported in [1,2,3], addressed two major issues: 1.) appropriate compensation for missing projection data regarding flaws for which no explicit a priori data is available, and 2.) the scaling and geometric registration of explicit a priori component data. The first of these issues is addressed by restricting interest to the reconstruction of flaws which have high-contrast (high S/N) discontinuous boundaries. This restriction focuses attention on problems ...


Use Of An X-Ray Process Model To Determine Crack Detectability In A Multi-Layer Geometry, R. Mark Wallingford, Joseph Nahum Gray Jan 1993

Use Of An X-Ray Process Model To Determine Crack Detectability In A Multi-Layer Geometry, R. Mark Wallingford, Joseph Nahum Gray

Review of Progress in Quantitative Nondestructive Evaluation

Inspection of a multi-layer geometry is of particular interest to the aircraft industry in which areas repaired with doublers must be continually inspected for further crack growth in the underlying structure. In some muti-layer geometries, x-ray inspection is the modality of choice due to the inaccessibility and limitations of other techniques. Because x-ray inspectability is extremely dependent upon crack opening and orientation, a need exists to quantitatively assess the detectability of cracks for various crack geometry parameters and x-ray generator parameters. X-ray simulation models for different generator types, generator settings, inspection geometries and crack parameters can be used to make ...


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.


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 ...


Pressure Cell For Magnetostrictive Measurements, Jerome E. Ostenson, Douglas K. Finnemore, David C. Jiles Feb 1989

Pressure Cell For Magnetostrictive Measurements, Jerome E. Ostenson, Douglas K. Finnemore, David C. Jiles

Ames Laboratory Publications

A pressure cell has been designed to study the magnetostrictive properties of a material as a function of both pressure and magnetic field. For changes in length on the order of 2000 ppm, it is necessary to have a substantial compliance in the pressure cell to retain a constant stress over the length of travel.