bluuebunny/crossref_metadata_2025_split huggingface dataset:
Local Crack Closure Measurements: Development of a Measurement System Using Computer Vision and a Far-Field Microscope
Authors: Sutton MA , Zhao W , McNeill SR , Helm JD , Piascik RS , Riddell WT 
Published: March 2009

An accurate and relatively simple methodology for estimating crack closure loads has been developed. Using this method, measurements may be taken at a user-specified position behind the crack tip during the entire fatigue crack growth process. The methodology has three distinct components: (a) an imaging system having adequate magnification with minimal distortion, (b) a simple, Windows-based procedure for image acquisition and image analysis, and (c) techniques for applying a random, high contrast pattern on the specimen's surface.
To meet the imaging requirements, a far-field microscope objective capable of high magnifications was employed to image small regions on the order of 0.5 mm by 0.5 mm. The regions were near the crack tip. To meet the requirements of a user-friendly system, a Windows-based data-acquisition interface was developed to run the system on a common PC. Using the interface, images are acquired automatically during a loading/unloading cycle and stored digitally. Image analysis is performed on the saved images to rapidly obtain the crack opening displacement as a function of load; these data are used to estimate the crack closure load. Finally, two methodologies for applying a random, high-contrast pattern with average sizes of 4 to 20 μm were developed. The first method uses 11 μm filter paper and a low-pressure compressed air supply to apply small particles of photocopier toner powder to the surface of the specimen. The second method uses contact lithography to achieve a random pattern with smaller feature sizes, on the order of 2 to 8 μm.
Baseline tests of the overall system have demonstrated that it is both easy to use and accurate. Specifically, (a) the PC interface has demonstrated that images can be acquired automatically while the loading frame is cycling at 0.01 Hz, and (b) the crack tip opening displacement data have been shown to have errors on the order of 0.05 pixels for the toner powder patterns, corresponding to 27 nm for the magnification used.
Solid Waste Disposal Site Characterization Using Non-Intrusive Electromagnetic Survey Techniques and Geostatistics
Authors: Kuhn GN , Woldt WE , Jones DD , Schulte DD 
Published: March 2009

Prior to the research reported in this paper, a site-specific hydrogeologic investigation was developed for a closed solid waste facility in Eastern Nebraska using phased subsurface characterizations. Based on the findings of this prior investigation, a surface based geoelectric survey using electromagnetic induction to measure subsurface conductivity was implemented to delineate the vertical and horizontal extent of buried waste and subsurface contamination. This technique proved to be a key non-intrusive, cost-effective element in the refinement of the second phase of the hydrogeologic investigation.
Three-dimensional ordinary kriging was used to estimate conductivity values at unsampled locations. These estimates were utilized to prepare a contaminant plume map and a cross section depicting interpreted subsurface features. Pertinent subsurface features were identified by associating a unique range of conductivity values to that of solid waste, saturated and unsaturated soils and possible leachate migrating from the identified disposal areas.
Microstructure Evolutions and Iron Redistribution in Zircaloy Oxide Layers: Comparative Effects of Neutron Irradiation Flux and Irradiation Damages
Authors: Iltis X , Lefebvre F , Lemaignan C 
Published: March 2009

To understand the acceleration of the Zircaloy corrosion kinetics in PWR conditions, TEM microstructural characterizations of oxide layers grown in an autoclave or directly in-reactor have been performed. To separate the influence on the oxidation process of the irradiation damage in the alloy from the dynamic effect of neutron flux, oxide layers have also been grown in an autoclave on previously neutron-irradiated cladding. The comparative characterization of these oxide layers leads to the following results: the nucleation and growth process are observed to be similar on oxides formed in-autoclave and significantly different on oxides grown directly in-reactor, indicating that this process is essentially affected by neutron irradiation or, more generally, parameters specific to the reactor environment. Concerning grain growth phenomena, it appears that the high microstructural instability noticed in oxides formed in-reactor is also the consequence of parameters specific to the reactor environment such as neutron irradiation or the lithium concentration gradient. Finally, the iron distribution in the oxide is almost the direct image of the iron distribution in the metal.
The impact of each experimental statement on the oxidation kinetics is discussed. The role of neutron irradiation on the structure of the oxide layer appears to be the most determining.
Effect of In-PWR Irradiation on Size, Structure, and Composition of Intermetallic Precipitates of Zr Alloys
Authors: Garzarolli F , Goll W , Seibold A , Ray I 
Published: March 2009

The corrosion behavior of Zr alloys depends on the kind, size, and distribution of the intermetallic second-phase particles. TEM examinations of Zr-Sn-Fe-Cr alloys irradiated in PWRs at temperatures between 300 and 370°C and fast fluences in the range of 5E21 to 1.3E22 cm-2 have been performed to study the irradiation-induced effects on the precipitates. The alloys contained different types of second-phase particles such as Zr(Fe,Cr)2, Zr2(Fe,Si), and Zr3Fe before irradiation. The influence of irradiation was found to depend on temperature and type of second-phase particles.
At temperatures below 310°C, the Laves phase Zr(Fe,Cr)2, which normally is the most frequent precipitate in Zry-4, depletes in Fe, becomes amorphous, and dissolves completely at higher fluences. With increasing temperature, the rate of Fe depletion and dissolution decreases and new Zr-Fe phases are formed. At temperatures above 370°C, the Laves phase remains stable or even grows under irradiation.
In Fe-containing Zr alloys with little or no Cr, rather large Zr3Fe precipitates are the most frequent particles. These particles are not dissolved by irradiation even at low temperatures. This was confirmed by annealing after irradiation.
As a hypothesis, it was assumed that the different behavior of the various precipitates can be related to their melting or decomposition temperatures by using the homologous temperature (i.e., the temperature under consideration in K normalized to the melting or decomposition temperature in K). This interrelationship has been found to apply for irradiation-induced amorphization. The empirical approach to describe the thermal ripening behavior of second-phase particles before irradiation and to describe the transition from irradiation-induced dissolution to irradiation-induced growth by a normalized (homologous) temperature led to reasonable results.
Evolution of Microstructure in Zirconium Alloys During Irradiation
Authors: Griffiths M , Mecke JF , Winegar JE 
Published: March 2009

X-ray diffraction (XRD) and transmission electron microscopy (TEM) have been used to characterize microstructural and microchemical changes produced by neutron irradiation in zirconium and zirconium alloys. Zircaloy-2, Zircaloy-4, and Zr-2.5Nb alloys with differing metallurgical states have been analyzed after irradiation for neutron fluences up to 25 × 1025 n.m-2 (E &gt; 1 MeV) for a range of temperatures between 330 and 580 K.
Irradiation modifies the dislocation structure through nucleation and growth of dislocation loops and, for cold-worked materials in particular, climb of existing network dislocations. In general, the a-type dislocation structure tends to saturate at low fluences (&lt; 1 × 1025 n.m-2). The c-component dislocation structure, however, may evolve over long periods of irradiation (for fluences &gt;10 × 1025 n.m-2 in some cases).
The phase structure is also modified by irradiation. The common alloying/impurity elements, Fe, Cr, and Ni, are relatively insoluble in the α-phase but are dispersed into the α-phase during irradiation irrespective of the state of the phase initially containing these elements, i.e., metastable β-phase or stable intermetallic precipitate. The stable intermetallic particles may undergo structural changes dependent on their composition and the temperature. For the metastable dual-phase α/β-alloys (Zr-2.5Nb alloy), the β-phase structure is modified during irradiation, but the change is complex, being a combination of thermal decomposition and radiation-induced mixing.
Non-Linear Irradiation Growth of Cold-Worked Zircaloy-2
Authors: Holt RA , Causey AR , Christodoulou N , Griffiths M , Ho ETC , Woo CH 
Published: March 2009

Accelerating irradiation growth has been reported for several zirconium alloys with a range of metallurgical states during high-temperature tests in fast-breeder reactors (673 to 723 K) for annealed Zircaloys in thermal test reactors at power reactor temperatures (523 to 623 K) and in power reactor core components fabricated from annealed or recrystallized Zircaloy. In the latter case, there was a transition from low to high irradiation growth rates at moderate fluences (about 3 × 1025 n/m2, E &gt; 1 MeV, at 580 K) related to the nucleation and growth of basal plane c-component loops.
It was recently reported that the elongation rate of cold-worked Zircaloy-2 pressure tubes also accelerates with increased fluence at about 550 K. This gradual acceleration coincides with a gradual increase in the density of c-component dislocations as a result of the helical climb of those dislocation segments with a predominantly screw character.
New data showing the acceleration of growth of cold-worked Zircaloy-2 at 550 K are presented, and a model is presented for the irradiation growth behavior of cold-worked Zircaloy-2 based on the evolution of the sink strengths of c-component dislocations (net vacancy sinks) and a-type dislocations (net interstitial sinks) as a function of fast fluence. According to the model, the growth rate reaches a maximum when the sink strength of c-component dislocations is approximately equal to that of the a-type dislocations, and hence the growth rate tends to saturate with increasing fluence.
The Three Thresholds for Fatigue Crack Propagation
Authors: Miller KJ 
Published: March 2009

The three governing threshold conditions in metal fatigue are considered, one relating to crack growth in single crystals, one concerned with crack growth in polycrystalline materials, and one based on linear elastic fracture mechanics (LEFM).
All three conditions are examined in relation to the two physical processes of cracking, i.e., Stage I (shear) and Stage II (tensile) crack growth.
The LEFM threshold is seen as a lower bound condition for fatigue crack growth rate, and the single crystal threshold is viewed in relation to the fundamental threshold pertaining to the fatigue resistance of polycrystalline metals.
Short Crack Growth Behavior
Authors: Sadananda K , Vasudevan AK 
Published: March 2009

We have re-evaluated short crack growth behavior using concepts developed recently, and we show that these concepts provide a unified framework that can explain both short and long crack growth behavior without resorting to the crack closure effect. We consider that the behavior of long cracks, including the effects of load ratio, R, is fundamental. We had shown previously that, since fatigue is at least a two-parameter problem in that at least two load parameters are required for an unambiguous description, there are two critical driving forces required simultaneously for fatigue cracks to grow. In extending this analysis to the growth of short cracks, we reject the current notion of the lack of similitude for short cracks and express the similitude as a fundamental postulate that, for a given crack growth mechanism, equal crack tip driving forces result in equal crack growth rates.
We find that, in most short crack problems considered in the literature, the cracks grow in pre-existing stress fields, which are either externally introduced or in situ generated. We refer to them as internal stresses. These can be residual stresses, residual stresses from prior treatment, or stresses generated during cycling. We show here that the observed lack of similitude and the large spread in the data for short cracks are due to: (1) an incomplete description of fatigue crack growth, (2) the variability of the internal stresses, and (3) uncertainties in their quantitative description (elastic versus elastic-plastic). We consider that the short cracks also grow at the same two thresholds as the long cracks, when all the components that contribute to the crack tip driving forces are included. In fact, short crack growth behavior confirms our concept that two parameters are required to define fatigue; consequently, for fatigue cracks to grow, two thresholds need to be satisfied simultaneously. We present examples from the literature to illustrate the concepts discussed.
Resistance Spot Weld Failure Loads and Modes in Overload Conditions
Authors: Zuniga S , Sheppard SD 
Published: March 2009

The failure modes of two single-weld specimens, the coach-peel and the tensile-shear specimens, were studied in detail. Weld overload experiments, along with optical and scanning electron microscopy, revealed that the coach-peel specimen failed by microvoid coalescence (ductile fracture) near the weld nugget/heat affected zone (HAZ) boundary and that the tensile-shear specimen failed predominately by localized necking (shear localization) near the HAZ/base metal boundary. Empirical data extracted from measurements performed on metallurgical cross sections of interrupted coach-peel and tensile-shear specimens established the deformed characteristic material distance (coach-peel) and the existence of a critical thickness strain for localized necking (tensile-shear). These quantities were used to predict weld failure via finite element analysis as described in Ref 1.
The work presented here is the first step in a larger project that is focused on developing a methodology for predicting spot weld overload failure in detailed finite element simulations of spot-welded joints. This methodology is based upon the failure phenomena (as reported here) and detailed characterization of the HAZ (as reported in Ref 1). The main requirement of this predictive methodology is that it be adaptable to any combination of joint configuration and loading direction. This predictive methodology will serve as the basis for the final step of developing a model of resistance spot weld failure based upon a simpler representation of the spot weld that can be used in car crash simulation models.
Development of High Strength 12% Cr Ferritic Steel for Turbine Rotor Operating above 600‡C
Authors: Tsuda Y , Yamada M , Ishii R , Tanaka Y , Azuma T , Ikeda Y 
Published: March 2009

An advanced 12% chromium ferritic steel has been developed for the high-temperature rotors in improved fossil-fired power plants. The development of this steel is based on the experimental studies of various 12% chromium heat resistant steels. Effects of alloy elements on the creep rupture strength have been investigated and the 10Cr-1.8W-0.7Mo-V-3Co-Nb-B steel was selected to be a hopeful candidate. This revealed the creep rupture strength was higher than that of 10Cr-1Mo-1W-V-Nb rotor steel being used at 593‡C.
The producibility and properties of the new steel have been verified with the medium size trial forging manufactured from a 20 ton ingot. Although a few technical subjects are remaining, these are expected to be solved with the modification of the manufacturing process.
This newly developed high strength 12% chromium ferritic steel is expected to be applicable to high-temperature rotors operating at 630‡C or above, and the significant improvement of thermal efficiencies would be obtained in fossil-fired power plants.
Electrochemical Methods for On-Site Determinations of Corrosion Rates of Rebars
Authors: Feliú S , González JA , Andrade C 
Published: March 2009

A review on the available electrochemical methods is presented for the on-site determination of rebar corrosion rate. In real size structures the methods available at present may be classified in three groups: A) Confinement of the applied electrical signal, B) Measurement of the lateral spreading of the electrical signal and C) Minimization of this lateral spreading. From these three alternatives, the first one has been implemented in a device that is now currently used for on-site measurements. This device is based in a “controlled” guard ring. In real size structures, the normal values of corrosion rates recorded are of the same order of magnitude of those previously measured in laboratory experiments. The levels are classified in: negligeable, low, moderate and high.
The gaps in the knowledge which still need to be investigated are also, commented: 1) unconfined measurements, 2) effect of counterelectrode size, 3) the true meaning of the corrosion rate measured, 4) constant B value, 5) current distribution around rebar perimeter 6) relation between mean corrosion rate and maximum pit depth and 7) identification of local corrosion. Finally, the role of embedded sensors on the monitoring of rebar corrosion risk, is mentioned.
Digital Elevation Data, Landsat TM and Magnetic Data for Visualization of Geomorphological and Geological Features
Authors: Wester K , Lundén B 
Published: March 2009

The main objective of this study is to develop methods for optimizing and merging different types of digital data for visual interpretation of geological lineaments and geomorphology. Two test areas with different topographic variability were selected in the Scandinavian mountain region.Different methods for enhancement based on convolution, both directional and non-directional, were applied on elevation data to detect subtle structural features. An excellent product for visual interpretation of lineaments is the artificial stereo pairs, using raw elevation data for the topography and spatially enhanced elevation data as background.The best spatial enhancement of Landsat TM images was achieved by unsharp masking and adaptive contrast stretch. To visualize the topography when analyzing satellite imagery, artificial stereo pairs were created using elevation data with Landsat TM data as background.Using synthetic stereo pairs solely based on magnetic data it was possible to find subtle magnetic anomalies. Also, together with elevation data, artificial stereo pairs were created with magnetic data as background color. This product allows interpretation of the relationship between topographic lineaments and magnetic anomalies.The image products presented here will not replace traditional maps and mapping methods; however, used as supplementary tools they may increase the understanding of many various geological and geomorphological phenomena. The techniques can provide some of the useful products needed for a complete environmental site characterizations.
Fire Fighters' Protective Clothing and Thermal Environments of Structural Fire Fighting
Authors: Lawson JR 
Published: March 2009

Fire fighters' protective clothing is designed to perform several functions. Of these, protection from heat and flame is one of the most important. Today's fire fighter protective clothing designs are based on years of field experience and research studies which addressed structural fires. Much of this work has concentrated on the fire environment where a fire fighter suddenly becomes enveloped in flames. This exposure generally results in serious life threatening injuries and sometimes death. Little appears to have been done to address the conditions where most burn injuries occur, outside of the flaming envelope. This paper attempts to define the general thermal environment at locations where fire fighters stage and begin their attack on a fire.
A great deal of research has been done to evaluate structural fires as they relate to building design, materials and contents. Only small elements of these data have been used in evaluating the thermal environment around fire fighters during normal attack situations. Results from early and recent studies clearly demonstrate the severity of thermal environments at fire attack staging areas. The flow of hot gases from a doorway or through a window may be well above 400°C (752°F) and may extend tens of meters down a corridor or across an adjoining room ceiling. Thermal radiation from a room's open doorway or window may reach levels which will cause burn injuries to exposed skin and cause charring or ignition of protective clothing fabrics which result in burn injuries to protected skin. Surface temperatures of solids within this staging zone may easily exceed 100°C (212°F), and touching these surfaces without protection could result in a sudden burn injury. A brief scenario is presented which serves as an example of how a fire fighter could receive second degree burns while attacking a fire from outside of the flaming envelope.
The Use of Electrochemical Noise to Investigate the Corrosion Resistance of UNS Alloy N04400 Nuclear Heat Exchanger Tubes
Authors: Brennenstuhl AM , Palumbo G , Gonzalez FS , Quirk GP 
Published: March 2009

Underdeposit corrosion of freshwater-cooled shutdown heat exchangers (SHX) and steam generators (SG) resulted in unscheduled unit shutdowns very early in the life of the Ontario Hydro Pickering B Nuclear Generating Station, whereas the same SHX and SG in the identical A station had not experienced any problems in over 19 years of operation. UNS alloy N04400 tubes were used for SHX and SG at both stations. Because detailed metallurgical analysis of tubes removed from the A and B stations suggested that alloy differences may be a major factor to the early failures at the B station, an investigation to characterize the corrosion resistance of the two alloys was carried out. From standard accelerated corrosion test methods it was inferred that the A and B alloys had similar corrosion resistance, suggesting that subtle but important material differences may have been masked by the aggressiveness of the test methods. Therefore, the electrochemical noise measurement (ENM) technique in conjunction with less aggressive test environments was used to characterize better the corrosion resistance of the A and B alloys. Variations in the corrosion resistance of the material removed from Pickering A and B heat exchangers (HX) were evident. During an initial exposure to deionized (DI) water at a pH of 5, the B alloy generally displayed greater passivity than the A material. However, the B alloy exhibited far less corrosion resistance than the A material when the pH of the water was reduced to 1 by the introduction of a nitric acid/acetic acid mixture. The predominant mode of degradation in the B material was intergranular attack with some localized corrosion in grain interiors. The A alloy, on the other hand, exhibited general corrosion.
The study also showed that the corrosion resistance of the A alloy was markedly reduced by heat treatment. A solution heat treatment at 900°C for 1 h followed by a cold-water quench or furnace cool from this temperature led to a corrosion performance similar to the nonheattreated B alloy. The same heat treatment did not significantly alter the corrosion performance of the B alloy. Changes in the mode of attack of the A and the B alloys were also observed when samples had been thermally treated. Both exhibited crystallographic attack, which was very localized in some areas. Transmission electron microscopy and secondary ion mass spectrometry revealed changes in the microstructure, which may account for the differences in the mode of attack. The predominant precipitate chemistry in the A alloy was Cr23C6, whereas in the B material it was titanium carbide. The B alloy also displayed boron segregation at the grain boundaries. This seemed to influence the extent of intergranular attack in this alloy.