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Iowa State University

1992

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Full-Text Articles in Physics

Twinned One-Dimensional Quasicrystals In Bridgman-Grown Al-Si-Cu-Co Alloys, L. X. He, Thomas A. Lograsso, Alan I. Goldman Jul 1992

Twinned One-Dimensional Quasicrystals In Bridgman-Grown Al-Si-Cu-Co Alloys, L. X. He, Thomas A. Lograsso, Alan I. Goldman

Ames Laboratory Publications

Single grains of Al60Si2Cu18Co20 with a decaprismatic morphology were grown by the Bridgman method and studied by transmission electron microscopy and x-ray diffraction. Although the diffraction patterns of these grains superficially resemble that of a decagonal quasicrystal, a closer inspection reveals that they are composed of tenfold twins of a one-dimensional quasicrystal along with small domains of three crystalline approximant phases.


Relaxation And Fluctuations In Glassy Fast-Ion Conductors: Wide-Frequency-Range Nmr And Conductivity Measurements, Ferdinando Borsa, D. R. Torgeson, Steve W. Martin, Hitendra K. Patel Jul 1992

Relaxation And Fluctuations In Glassy Fast-Ion Conductors: Wide-Frequency-Range Nmr And Conductivity Measurements, Ferdinando Borsa, D. R. Torgeson, Steve W. Martin, Hitendra K. Patel

Materials Science and Engineering Publications

Li7 nuclear spin-lattice relaxation rates (R1) versus the temperature at several resonance frequencies (4 to 40 MHz) are reported together with the conductivity measurements, σ(ω), in the range 1 Hz to 3.76 MHz on 0.56Li2S+0.44Si2S, a glassy fast-ionic conductor. Both R1 and σ(ω) are fitted consistently over the whole temperature and frequency range by using a stretched-exponential, i.e., exp(-t/τ*c)β for the corresponding correlation functions (CF). Formulas that relate R1(ω) and σ(ω) and that give the asymptotic behavior as functions of T and ω of both quantities are ...


Fast Ionic Conduction In Na2s+B2s3 Glasses: Compositional Contributions To Nonexponentiality In Conductivity Relaxation In The Extreme Low-Alkali-Metal Limit, Hitendra K. Patel, Steve W. Martin May 1992

Fast Ionic Conduction In Na2s+B2s3 Glasses: Compositional Contributions To Nonexponentiality In Conductivity Relaxation In The Extreme Low-Alkali-Metal Limit, Hitendra K. Patel, Steve W. Martin

Materials Science and Engineering Publications

The conductivity relaxation phenomenon in glassy and crystalline ionic conductors has been known for many years to be a highly nonexponential process. The stretched exponential function exp-(t/τ)β has been used with varying levels of success to describe this relaxation. Whether the nonexponentiality is due to parallel conducting processes acting independently of each other and having a distribution of relaxation times or to serial processes strongly coupling the ionically conducting species and constraining each other’s relaxation, the exact nature of this process is still unknown. If coupling is the active mechanism responsible for the nonexponentiality, then there ...


Spatial Variation Of A Short-Lived Intermediate Chemical Species In A Couette Reactor, R. Dennis Vigil, Q. Ouyang, Harry L. Swinney Apr 1992

Spatial Variation Of A Short-Lived Intermediate Chemical Species In A Couette Reactor, R. Dennis Vigil, Q. Ouyang, Harry L. Swinney

R. Dennis Vigil

We have conducted experiments and simulations of the spatial variation of a short-lived intermediate species (triiodide) in the autocatalytic oxidation of arsenite by iodate in a reactor that is essentially one dimensional-the Couette reactor. (This reactor consists of two concentric cylinders with the inner one rotating and the outer one at rest; reagents are continuously fed and removed at each end in such a way that there is no net axial flux and there are opposing arsenite and iodate gradients.) The predictions ?f a one-dim~ns~onal . reaction-diffusion model which has no adjustable parameters, are In good qualItative (and, In ...


Pinski Et Al. Reply, F. J. Pinski, B. Ginatempo, Duane D. Johnson, J. B. Staunton, G. M. Stocks, B. L. Gyorffy Mar 1992

Pinski Et Al. Reply, F. J. Pinski, B. Ginatempo, Duane D. Johnson, J. B. Staunton, G. M. Stocks, B. L. Gyorffy

Duane D. Johnson

With our calculations [I], we uncovered the electronic mechanism responsible for inducing atomic short-range order (SRO) in the disordered solid solution of NiPt as it is cooled. Usually, but not always, SRO, whether derived theoretically or measured experimentally, indicates the nature of the long-rangeordered (LRO) state that will stabilize at low temperature. Our calculation of the atomic SRO, while agreeing with experiments [2], neglected the relativistic effects in the electronic structure. Lu, Wei, and Zunger (LWZ) [3,4], on the other hand, have calculated the L lo-ordered alloy formation energy and find that only when relativistic effects are included is ...


Tem Observations Of The Mechanism Of Delamination Of Chromium Films From Silicon Substrates, D. Goyal, Alexander H. King Feb 1992

Tem Observations Of The Mechanism Of Delamination Of Chromium Films From Silicon Substrates, D. Goyal, Alexander H. King

Alexander H. King

We have observed the complete delamination of polycrystalline chromium films from single crystal silicon substrates during deposition due to the formation of high internal stresses. These intrinsic stresses can give rise to interfacial defects which assist in the separation of the film from the substrate. Stresses in the film are balanced by stresses in the substrate, which cause mechanical failure in the substrate near the interface. Extensive arrays of dislocations and cracking of the substrate have been observed. We find that the delamination of the films from the substrate is initiated by the formation of damage in the substrate, rather ...


Magnetic Flux Motion And Flux Pinning In Superconductors , Steven C. Sanders Jan 1992

Magnetic Flux Motion And Flux Pinning In Superconductors , Steven C. Sanders

Retrospective Theses and Dissertations

Magnetization measurements on the two high-temperature superconductors Nd[subscript]1.85Ce[subscript]0.15CuO[subscript]4-y and Ba[subscript]0.6K[subscript]0.4BiO[subscript]3 have been undertaken in order to study the reversible and irreversible magnetic behavior and compare these two different materials with other high-temperature superconductors (HTSC). While the other HTSC are known to have hole carriers and layers of CuO[subscript]2 planes in anisotropic crystal structures, Nd[subscript]1.85Ce[subscript]0.15CuO[subscript]4-y (NCCO) has electron carriers as well as hole carriers, and Ba[subscript]0.6K[subscript]0.4BiO[subscript]3 (BKBO ...


Magnetic Properties Of High-T[Subscript C] Superconductors , Junho Gohng Jan 1992

Magnetic Properties Of High-T[Subscript C] Superconductors , Junho Gohng

Retrospective Theses and Dissertations

Magnetic properties of high-T[subscript] c superconductors have been studied in order to determine the free-energy surface, the characteristic critical fields, order parameters structure, and the grain size effect on magnetization. Studies of the thermodynamic reversibility for YBa[subscript]2Cu[subscript]3O[subscript]7-[delta] show the rounding in magnetization vs. temperature curves is a reflection of the thermodynamic fluctuations near T[subscript] c. Specific heat jump C(0)-C(H) values that have been calculated from the free-energy surfaces show good agreement with the direct calorimetric measurements;Comparative studies of the free-energy surfaces, flux creep and critical currents for ...


A Study Of Isolated Photons In Z0 Hadronic Decays Using The Delphi Detector At Lep , Randall R. Holmes Jan 1992

A Study Of Isolated Photons In Z0 Hadronic Decays Using The Delphi Detector At Lep , Randall R. Holmes

Retrospective Theses and Dissertations

We present a study of the production of energetic isolated photons in the reaction e[superscript]+e[superscript]-→ Z[superscript]0→ q[macron]q[gamma] using the DELPHI detector at LEP. Within the context of the Standard Model, our results for final state radiation show no evidence for anomolous photon production due to rare or new processes. We present a comparison of our data with these theoretical expectations and present upper limits at the 95% CL on the cross section times the branching ratio to hadrons and a photon for the rare or new processes: (1) [sigma](e[superscript]+e ...


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 ...


Ir Thermal Wave Tomographic Studies Of Structural Composites, L. D. Favro, H. J. Jin, Y. X. Wang, T. Ahmed, X. Wang, P. K. Kuo, R. L. Thomas Jan 1992

Ir Thermal Wave Tomographic Studies Of Structural Composites, L. D. Favro, H. J. Jin, Y. X. Wang, T. Ahmed, X. Wang, P. K. Kuo, R. L. Thomas

Review of Progress in Quantitative Nondestructive Evaluation

Vavilov et al [1] have recently described a technique for making tomographic thermal wave images. Their method involves recording a succession of thermal wave images after a flash-heating pulse, followed by a numerical pixel-by-pixel search of the images for the time at which the reflected thermal waves from subsurface features have their peak amplitudes. Since the peak time is related to the depth of the scatterer, this information enables one to separate the image into time (or depth) slices. The result is a thermal wave tomogram. Since their process involves post-processing and a search through a large number of stored ...


Error Arising From Original Approximation In Photothermal Measurement Of Weak Absorption Of Optical Thin Film, Baixuan Shin, Wenbin Chen, G. G. Siu, D. S. Chiu Jan 1992

Error Arising From Original Approximation In Photothermal Measurement Of Weak Absorption Of Optical Thin Film, Baixuan Shin, Wenbin Chen, G. G. Siu, D. S. Chiu

Review of Progress in Quantitative Nondestructive Evaluation

The technique of photothermal deflection spectroscopy (PTDS) for absorption measurement of optical thin film is simple in installation and fast in detection. However, while measurable absorbance reaches the order of magnitude of 10-7, e.g. in studies of optical thin film and investigation of laser damage mechanisms [1,2], we are still doubtful of its precision because of the lack of independent evaluation with available instruments whose precision could reach this lower limit. This work aims at giving a theoretical investigation on the source of error in order to obtain a realistic estimate of measurement error and hence to find ...


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.


Analytic Calculations And Numerical Simulations Of Box-Car Thermal Wave Images Of Planar Subsurface Scatterers, D. J. Crowther, L. D. Favro, P. K. Kuo, R. L. Thomas Jan 1992

Analytic Calculations And Numerical Simulations Of Box-Car Thermal Wave Images Of Planar Subsurface Scatterers, D. J. Crowther, L. D. Favro, P. K. Kuo, R. L. Thomas

Review of Progress in Quantitative Nondestructive Evaluation

The purpose of this study is to improve the quality of thermal wave infrared (IR) images in terms of the real shape of the defect. Due to heat diffusion into the sample, thermal wave images are usually blurred, especially for deep defects or long times. Because of this feature the use of traditional image post-processing (gradient image, threshold…) to assess the size and the shape of the defect quite often leads to false results. In order to increase the accuracy in the shape recovery, we need to “unblur” the thermal wave image, i.e. to reverse or invert the blurring ...


Dynamic Thermal Tomography: New Nde Technique To Reconstruct Inner Solids Structure Using Multiple Ir Image Processing, V. Vavilov, X. Maldague, J. Picard, R. L. Thomas, L. D. Favro Jan 1992

Dynamic Thermal Tomography: New Nde Technique To Reconstruct Inner Solids Structure Using Multiple Ir Image Processing, V. Vavilov, X. Maldague, J. Picard, R. L. Thomas, L. D. Favro

Review of Progress in Quantitative Nondestructive Evaluation

Nondestructive evaluation (NDE) technique appeared as the natural consequence of materials analysis by using a variety of physical fields and particles which being propagated through the specimen are able to produce the image of its inner structure. Disadvantage of traditional “shadow” or “backscattered” images is that the “weak” details are scarcely seen on the background of “stronger” ones. This is why the introduction of the tomographic principles, allowing to “slice” the solid into individual layers, was viewed as a revolution in vision techniques (especially in X-ray imaging). Ultrasonic, ultra-high frequency and nuclear magnetic resonance tomography are under quick development now.


Time-Resolved Infrared Radiometry (Trir) For Characterization Of Impact Damage In Composite Materials, J. W. Maclachlan Spicer, W. D. Kerns, L. C. Aamodt, J. C. Murphy Jan 1992

Time-Resolved Infrared Radiometry (Trir) For Characterization Of Impact Damage In Composite Materials, J. W. Maclachlan Spicer, W. D. Kerns, L. C. Aamodt, J. C. Murphy

Review of Progress in Quantitative Nondestructive Evaluation

A quantitative thermographie NDE technique for the characterization of impact damage in composite materials is under development along with supporting theoretical analysis. We have previously shown that the technique of time-resolved infrared radiometry (TRIR) is an effective method for quantitatively detecting coating thickness variations and for characterizing the degree of coating disbonding in terms of equivalent air gaps [1,2]. Here we extend the TRIR technique to the study of composite systems by applying the results of a multilayer analytical model [3]. Experimental results in both simple and hybrid composite systems are discussed. The depth and lateral extent of interlaminar ...


Fast Photothermal Inspection Of Plasma-Sprayed Coatings Of Primary Circulation Seal Rings Of A Nuclear Reactor, R. Lehtiniemi, J. Hartikainen, J. Rantala, J. Varis, M. Luukkala Jan 1992

Fast Photothermal Inspection Of Plasma-Sprayed Coatings Of Primary Circulation Seal Rings Of A Nuclear Reactor, R. Lehtiniemi, J. Hartikainen, J. Rantala, J. Varis, M. Luukkala

Review of Progress in Quantitative Nondestructive Evaluation

A need for NDE of plasma-sprayed coatings has been a serious problem in the industry for a long time. Traditional methods like ultrasonics or x-ray absorption usually cannot be used because of the high attenuation and the heterogeneity of the coating. On the other hand, sub-surface flaws cannot be detected with liquid penetration technique and electromagnetic methods are not suitable for dielectric coating. However, photothermal techniques have been successfully applied [1,2], but first the introduction of fast infrared scanning systems has lead to reasonable speed of inspection from the practical point of view.


Flying Laser Spot Thermal Wave Ir Imaging, Y. Q. Wang, P. Chen, P. K. Kuo, L. D. Favro, R. L. Thomas Jan 1992

Flying Laser Spot Thermal Wave Ir Imaging, Y. Q. Wang, P. Chen, P. K. Kuo, L. D. Favro, R. L. Thomas

Review of Progress in Quantitative Nondestructive Evaluation

In a previous report, some of the authors have described the basic experimental technique for flying laser spot thermal wave IR imaging, and demonstrated its potential usefulness for the detection of closed vertical cracks [11. The objective of the present work is to provide a theoretical description of the temperature distribution from a Gaussian-shaped surface heat spot, scanned at constant speed, and to compare the predictions of that theoretical description with temperature distributions measured experimentally with our thermal wave flying spot imaging system.


Numerical Solutions For Heat Flow In Adhesive Lap Joints, P. A. Howell, William P. Winfree Jan 1992

Numerical Solutions For Heat Flow In Adhesive Lap Joints, P. A. Howell, William P. Winfree

Review of Progress in Quantitative Nondestructive Evaluation

The detection of disbonds in riveted lap joints is of increasing interest to the aerospace community. Adhesively bonded and riveted lap joints are used to bond the thin overlapped sheets of aluminum which comprise the outer skin of an aircraft. Through time, the integrity of the bond can become compromised by disbanding, leading to corrosion and stress concentrations at the rivets and subsequent cracking leading to joint failure. A thermal technique for determining bond integrity in these structures has been investigated by Winfree, et al [1]. This technique involves active heating of the aircraft fuselage with a measurement of the ...


Bonds Nde Using Stimulated Infrared Thermography, P. M. Delpech, D. M. Boscher, F. Lepoutre, A. A. Deom, D. L. Balageas Jan 1992

Bonds Nde Using Stimulated Infrared Thermography, P. M. Delpech, D. M. Boscher, F. Lepoutre, A. A. Deom, D. L. Balageas

Review of Progress in Quantitative Nondestructive Evaluation

Among all the photothermal techniques that have appeared since some years, the photothermal radiometry is very attractive because of its noncontact and rapid-scanning ability [1,2]. In our laboratory, we developed pulsed stimulated infrared (IR) thermography [3]. Due to the relatively low refreshment frequency of the currently used IR cameras, the application of the method was restricted to low thermal conductors. In particular, we applied it to carbon/epoxy composites [4,5]. Some new developments of the data reduction procedure were presented last year [6] to use this technique with good heat conductors. Satisfactory results were obtained in the case ...


Comparison Of Heating Protocols For Detection Of Disbonds In Lap Joints, William P. Winfree, B. Scott Crews, P. A. Howell Jan 1992

Comparison Of Heating Protocols For Detection Of Disbonds In Lap Joints, William P. Winfree, B. Scott Crews, P. A. Howell

Review of Progress in Quantitative Nondestructive Evaluation

With the increased concern for the safety and reliability of aging aircraft, new nondestructive techniques are being sought for detecting and characterizing defects in these structures. These techniques must be both reliable and economical to impact the current safety of the fleet. To meet both of these requirements, more focus is being placed on large area inspection techniques. These offer the possibility for greatly reduced inspection times as compared to current point measurement techniques.


Nondestructive Evaluation Using Shearing Interferometry, Thomas C. Chatters, Sridhar Krishnaswamy Jan 1992

Nondestructive Evaluation Using Shearing Interferometry, Thomas C. Chatters, Sridhar Krishnaswamy

Review of Progress in Quantitative Nondestructive Evaluation

Coherent shearing interferometry involves the interference of a coherent optical wavefront with a spatially shifted version of itself. The resulting interference pattern carries information which for small shears (spatial shifts) can be related to the gradients of the phase of the wavefront. The primary advantage of this optical technique is that it is relatively insensitive to rigid body motion. A coherent wavefront that is transmitted through a body or is reflected from the surface of a body will carry information about the resulting stress state or deformation of the body. This information can be used for nondestructive evaluation applications using ...


Nanosecond Scale Optical Pulse Separations For Holographic Investigation Of High-Speed Transient Events, Michael J. Ehrlich, James W. Wagner Jan 1992

Nanosecond Scale Optical Pulse Separations For Holographic Investigation Of High-Speed Transient Events, Michael J. Ehrlich, James W. Wagner

Review of Progress in Quantitative Nondestructive Evaluation

The dynamics of detonation for dispersed solid particulate explosives are not well understood. These explosives, used for mine neutralization, are comprised of a fine, solid particulate dust which is dispersed as a cloud over a given area. When detonation is initiated in some portion of the cloud, the ensuing detonation wave propagates throughout the entire cloud and results in an explosion, generating a tremendous pressure which serves to destroy any land mines present. However, the mechanism with which individual explosive particles interact to sustain detonation in these solid dispersed particle explosives is not clear. In liquids, for example, it is ...


Computed Speckle Decorrelation (Csd) And Its Application For Fatigue Damage Monitoring, J. Scott Steckenrider, James W. Wagner Jan 1992

Computed Speckle Decorrelation (Csd) And Its Application For Fatigue Damage Monitoring, J. Scott Steckenrider, James W. Wagner

Review of Progress in Quantitative Nondestructive Evaluation

A video-based laser speckle technique has been developed for non-contact surface deformation analysis and mapping at speeds approaching video frame rates. This technique, Computed Speckle Decorrelation (CSD), makes use of the speckle decorrelation associated with surface deformation. In its current application, CSD is a method of full field inspection which has been used both to locate fatigue damage sites and to measure damage severity during fatigue deformation in reverse bending fatigue of a cylindrically notched aluminum specimen. With the development of the CSD method it will now be possible to examine in greater detail the progression of fatigue damage in ...


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 ...