bluuebunny/crossref_metadata_2025_split huggingface dataset:
Prediction of Creep Anisotropy in Zircaloy Cladding
Authors: Perkins RA , Shann S-H 
Published: March 2009

Due to the hexagonal crystal structure of zirconium and the radial orientation of the basal poles in Zircaloy cladding, the deformation of light water reactor Zircaloy fuel cladding is anisotropic. Plastic deformation of this cladding can be defined by the R and P factors that are the circumferential/radial and axial/radial contractile strain ratios under uniaxial deformation along the axial and circumferential direction, respectively. The in-reactor deformation performance of the cladding can be modeled with good accuracy if the R and P values of the irradiation-induced creep are known.
In a boiling water reactor (BWR) fuel assembly, most fuel rods have a hoop stress to axial stress ratio of about 2:1. The assembly also contains several fuel rods (tie rods) that connect the upper and lower tie plates. The tie rods have an additional stress component in the axial direction. BWR assemblies can, furthermore, contain water rods that are free of stress, and therefore, provide a measure of stress-free irradiation growth. Post-irradiation deformation measurements of these three types of rods are used to derive the R and P factors for BWR cladding during irradiation.
Laboratory tensile and creep tests at several temperatures have been performed on five types of cladding to determine if a short-term test could be used to obtain R values representative of the in-reactor values. For standard Zircaloy-2 cladding that was examined in-reactor, a good correlation with the in-reactor R value was obtained from both tensile and creep tests performed at 382°C. For another type of Zircaloy-2 cladding (late beta-quenched (LBQ) cladding), inreactor deformation performance correlates better with the tensile test results than the creep test results. The other three types of cladding (Zircaloy-4) with differing textures and processing histories have exhibited significant differences in the R values in the laboratory tests.
Microstructure and Properties of Corrosion-Resistant Zirconium-Tin-lron-Chromium-Nickel Alloys
Authors: Bradley ER , Nyström A-L 
Published: March 2009

Long-term autoclave tests in steam at 673 K and mechanical property (tensile and creep) tests have been conducted to evaluate the effects of chromium (0 to 0.3%) and nickel (0 to 0.08%) additions on the corrosion and mechanical properties of dilute zirconium-tin-iron alloys. The base alloys contain 0.4% iron and either 0.5% or 1.0% tin.
Multiple regression analysis showed tin concentration to have a statistically significant effect on corrosion, hydrogen pickup, creep, and tensile strength. The corrosion resistance of the alloys increased significantly when the tin concentration decreased from 1.0 to 0.5%. An additional improvement in corrosion resistance was observed with increasing chromium content. Nickel additions had no apparent effect on corrosion for the alloy compositions examined. Lower hydrogen pickup fractions were measured for alloys containing 0.5% tin compared to alloys containing 1.0% tin. No significant effects of chromium or nickel additions to hydrogen pickup were observed.
Creep rate decreased with increasing tin concentration and to a lesser extent with increasing chromium content. Nickel additions produced a large increase in creep rate for some alloys but not others. This suggests a possible interaction between nickel and the other alloy additions in determining creep strength.
Intermetallic particle type and size distribution varied with alloy composition. Chromium additions tended to decrease the particle size distribution of Zr(Fe,Cr)2 intermetallic particles. Conversely, nickel additions produced large particles of the Zr2(Fe,Ni) type intermetallic. Changes in the intermetallic particle distributions and matrix compositions are discussed with regard to the observed changes in corrosion and mechanical properties of the alloys.
How the Tetragonal Zirconia is Stabilized in the Oxide Scale that is Formed on a Zirconium Alloy Corroded at 400°C in Steam
Authors: Godlewski J 
Published: March 2009

Zircaloy-4, in three different metallurgical forms (stress relieved, recrystallized, and β-quenched), was oxidized at 400°C, in steam, up to 95 days. For each sample, the fraction of tetragonal zirconia was measured by X-ray diffraction and Raman spectroscopy. These two techniques show the presence of several zones containing tetragonal zirconia: a zone rich in the oxide near the metal-oxide interface and an other zones with lower concentrations in the rest of the pre-transition layers. For the post-transition samples, the external sublayer contains only a small amount of tetragonal zirconia.
Measurements of residual stresses by X-ray diffraction in the metal underlying the oxide show that the metal is under tensile stress state and that the stress values vary with oxidation duration. The level of the stress depends on the metallurgical form of the initial metal. The low penetration of X-rays in the material also made it possible to show the presence of a very high stress gradient near the metal-oxide interface that can explain the high proportion of tetragonal zirconia near the interface.
The study of the incorporation of intermetallic precipitates in the oxide and their chemical changes was carried out by electron microprobe analysis on taper cross sections of the oxide. This technique makes it possible to perform a large number of point analyses that yield satisfactory statistics for the variation in the iron/chromium (Fe/Cr) atom ratio of the precipitates in the oxide.
The intermetallic precipitates are incorporated into the oxide layer and then undergo a chemical change starting at a particular distance from the metal/oxide interface. The characteristic values of the Fe/Cr ratio before oxidation (1.6 for stress relieved and recrystallized conditions and 0.8 for β-quenched samples) are progressively spread out during oxidation. This change could correspond to an oxidation of intermetallic precipitates with segregations of iron at the precipitate-oxide interface, as shown in the literature.
The oxidation of the precipitates is accompanied by a volume change that should lead to the formation of a stress field around the precipitates and could stabilize the neighboring tetragonal phase. When the precipitates are completely oxidized, the stress field disappears and there is a transformation of the tetragonal phase to a monoclinic form, leading to the kinetic transition. Stress relaxation is shown by a decrease of the tensile stresses in the metal underlying the oxide that is undergoing kinetic transition.
Phenomenological Study of In-Reactor Corrosion of Zircaloy-4 in Pressurized Water Reactors
Authors: Kim YS , Rheem KS , Min DK 
Published: March 2009

Uniform in-reactor corrosion has been examined on pressurized water reactor (PWR) Zircaloy-4 fuel claddings that were irradiated up to four cycles in the KORI Unit 1. The oxide layer that was formed on the Zircaloy-4 fuel claddings changes from a uniform black oxide into the nonuniform white granular oxides when the oxide layer reaches about 5 to 10 μm. With irradiation exposure, enough of the white granular oxides have nucleated above the black oxide layer to entirely cover the fuel cladding, resulting in a gray or white cladding surface. The change in the oxide layer growth pattern from the uniform black oxide layer into the nonuniform granular oxides resulted in the formation of macro-pores or cracks in the oxide layer, causing the corrosion rate to change into a linear rate from the cubic rate, especially at the beginning of fuel rod life. Consequently, the nucleation of white granular oxides is a phenomenological indicator of the transition of the in-reactor corrosion rate.
To explain the effect of hydride precipitates on the in-reactor corrosion, the corrosion behavior for a defective fuel rod with a through-hole and an intact fuel rod adjacent to it (both were irradiated for two cycles in the KORI Unit 1) has been investigated. Even though both of them were found to have almost identical operating power histories, their corrosion behavior was quite different: the maximum oxide layer thickness for the intact fuel rod was less than 10 μm, while the defective fuel rod had an abnormally thick oxide of 50 μm, especially at an elevation where a large extent of hydrides (corresponding to 1295 to 1520 ppm hydrogen) were precipitated at the cladding outer surface. Therefore, the hydrides that were locally precipitated on the cladding outer surface initiated the in-reactor corrosion enhancement to a degree that was dependent upon the extent of the hydrides. Furthermore, the corrosion enhancement by hydrides is likely to effectively occur late in the fuel life time or after more than three or four cycles of irradiation, thus leading to the enhanced post-transition corrosion rate.
Effects of Pressurized Water Reactor (PWR) Coolant Chemistry on Zircaloy Corrosion Behavior
Authors: Karlsen T , Vitanza C 
Published: March 2009

A number of the test programs currently in progress at the Halden Project are aimed at evaluating Zircaloy cladding performance in terms of corrosion behavior, particularly at high burnup.
A pressurized water reactor (PWR) facility has been used to determine the effects of high (4 to 4.5 ppm) lithium on the corrosion behavior of Zircaloy-4 cladding material exposed to nucleate boiling (1% void) and to one-phase cooling conditions. The test employed four fuel rod segments, base-irradiated to an average burnup of 28.5 MWd/kg UO2 in a commercial power plant, and with average initial oxide layers of either 10, 20, or 40 μm, respectively. Four sets of oxide layer thickness measurements were performed on the four rods during the course of the investigation. Pre-test eddy current measurements were performed on the as-received segments and two interim sets of measurements were made after 80 and 245 full power days of irradiation. Final oxide measurements were made after 425 full power days, when maximum rod burnup was 45 MWd/kg UO2.
Average oxide layer increases of 30 and 55 μm were observed for the rods exposed to one-phase cooling and nucleate boiling conditions, respectively. Although maximum oxide thickness exceeded 95 μm, no evidence of spalling was apparent. The measured oxide layer thicknesses compared favorably with predicted values based on model calculations derived from power plant data, with little evidence of enhanced corrosion rates in the presence of increased lithium concentrations.
Portal Metal Detectors at the U.S. Department of Energy Hanford Site
Authors: Swank RG , Riedeman GW 
Published: March 2009

The U.S. Department of Energy's Hanford Site has devoted considerable attention to improving the operation of and confidence in the commercially available metal detectors installed at the site. A set of testing and calibration specifications was prepared and applied that yielded appreciable improvements.
These specifications were based on a set of tests developed to measure portal zone sensitivity and to derive the probability of detection and nuisance alarm statistics. A pragmatic approach to test article selection was also developed. This paper desribes these specifications, their underlying philosophy and methodology, and the results of their application.
Friction and Wear Characterization of UHMWPE in Reciprocating Sliding Contact with Co-Cr, Ti-6Al-4V, and Zirconia Implant Bearing Surfaces
Authors: Poggie RA , Wert JJ , Mishra AK , Davidson JA 
Published: March 2009

A tribometer, especially designed to simulate the high contact stresses, reciprocating sliding, and plowing conditions observed for the non-conformal mating wear couple of a total knee prosthesis is described. This tribometer was used to evaluate the tribological behavior of Co-Cr, Ti-6Al-4V, yttria-stabilized tetragonal zirconia, and monoclinic zirconia-coated zirconium alloy pins in cyclic sliding contact with UHMWPE.
The tribometer described employs a right cylinder on flat geometry. The metallic and ceramic pins were in the form of cylinders which were 9 mm in diameter and 19 mm long. The cylinders were wear tested in reciprocating sliding contact (15 mm stroke length, 2.1 Hz) with 12.7 mm wide UHMWPE strips. The wear tests were conducted in deionized water for two million cycles. The wear of the UHMWPE strips and cylinders was characterized using an appropriate combination of weight and thickness change measurements, optical stereomicroscopy, scanning electron microscopy (SEM), and measurement of UHMWPE debris and metal ion concentrations in the deionized water solutions.
The lowest friction coefficients (0.02 – 0.04) occurred during the run-in period for all materials tested. The observed increases in COF values coincided with the formation of UHMWPE transfer layers and abrasion of the cylinder surface. Transfer layer formation and an increase in the COF, as well as cylinder abrasion and the resultant increase in surface roughness, correlated with an increase in wear of the UHMWPE strips and an increase in the concentration of UHMWPE wear debris and metal ion levels in the deionized water solutions. The results of this series of wear tests show that this tribometer is capable of obtaining reliable and accurate dynamic friction data and that measured changes in the COF correlate well with observed changes in surface roughness and chemistry of the contact surfaces.
Tribological Approaches for Elastomer Applications in Computer Peripherals
Authors: Bayer RG 
Published: March 2009

In computer peripheral equipment, such as printers and check sorters, elastomers are frequently used as dampers to control impact and as rollers to stop and feed paper and ribbon. To address such applications tests and models were developed to evaluate materials and predict performance. In this paper, the models and tests used to address both impact and feed roll applications are described, along with examples of their applications. In both applications the tests are used to compare materials and to provide values of empirical parameters required for application of the models.
The test techniques and apparatii used to evaluate materials for these applications are described. Further a model developed for impact wear of elastomers and its application to several wear points in an electro-magnet unit of a high speed printer will be presented. Also an abrasive wear model used for feed roll applications will be discussed. Its use will be illustrated by two examples. One is taken from a check sorter; the other, from a ribbon stuffing box application. In both feed roll applications additional friction tests were required. The methods used to determine the coefficient of friction will also be presented.
In these applications predictions of the models were compared with actual performance. The agreement between these predictions and actual performance, which is generally good, will also be discussed.
Additionally, various aspects of another application of elastomers in high speed printing, i.e., as push rod tips, will be discussed. In this application cracking at stress concentration locations is a concern, as well as surface wear. The experimental and analytical approaches used to understand and characterize behavior in this application will be presented.
Crack Resistance, Fracture Toughness, and Instability in Damage-Tolerant Aluminum-Lithium Alloys
Authors: Wanhill RJH , Schra L , 't Hart WGJ 
Published: March 2009

A comparison is made of the crack resistance (R-curve), fracture toughness, and instability behavior of candidate damage-tolerant aluminum-lithium (Al-Li) alloys, 2091 and 8090, and the widely used conventional 2024-T3 alloy. The 2091 alloy was in three heat treatment conditions, T8X, TX, and TY, all artificially aged. The 8090 alloy was in the T81 condition. The crack resistances and fracture toughnesses of 2091-T8X and 8091-T81 were similar to those of 2024-T3, but at a 50 MPa lower strength level. The crack resistances and fracture toughnesses of 2091-TX and 2091-TY were much inferior.
In all cases, stable (slow) crack growth was ductile, but unstable crack growth in 2091-TX and 2091-TY was 100% intergranular and macroscopically brittle. Unstable crack growth in 2091-T8X was 50% intergranular and macroscopically ductile. Fractographic analysis indicated the 2091-TX and 2091-TY alloys to be sensitive to dynamic effects, such that the dynamic fracture toughness could be significantly lower than the quasi-static fracture toughness. This may also be true of 2091-T8X. In view of these results, fail-safe crack arrest tests should be included in any evaluation of damage-tolerant Al-Li sheet alloys for aircraft structures.
Ultrasonic Wave Technique to Assess Cyclic-Load Fatigue Damage in Silicon-Carbide Whisker Reinforced 2124 Aluminum Alloy Composites
Authors: Achenbach JD , Fine ME , Komsky I , McGuire S 
Published: March 2009

Composites composed of a precipitation-hardened 2124 aluminum (Al) alloy matrix reinforced by silicon-carbide (SiC) whiskers, which are fabricated by powder metallurgy, are susceptible to fatigue damage due to microcracking along SiC-Al interfaces, especially at the external surfaces of a body. The microcracks that are produced in the crack initiation process are generally too small to be detected and characterized by conventional ultrasonic techniques. Since they may link up to produce macrocracks and rapid final fracture, a simple experimental technique is required to assess the extent of the microcracking. This paper reports on an ultrasonic surface wave technique that was developed for that purpose. In this technique, the integrated effect of the damage is established by careful measurements of the changes of the phase velocity and the coefficient of attenuation as the number of cycles of fatigue loading increases.
The specimens, 6.6 mm thick, 13 mm wide, and 105 mm long in the gage section, were fatigued in pull-pull under load control. Surface waves were generated at 5 MHz with conventional surface wave transducers. A special self-calibrating ultrasonic bridge was employed to measure surface wave motion by means of two dry contact point pickups separated by a known distance along the direction of surface wave propagation. Wave speed measurements were obtained by the use of a variation of the overlap technique. To measure the attenuation, the data were deconvolved from the response functions of the point contacts by the use of data for surface wave generation in two opposite directions.
Glass Transition and Heat Capacities of Inorganic Glasses: Diminishing Change in the Heat Capacity at T
g for xNa2S + (1 − x)B2S3 Glasses
Authors: Kincs J , Cho J , Bloyer D , Martin SW 
Published: March 2009

The Tg's and heat capacity functions have been measured for a series of Na2S + B2S3 glasses for the first time. Unlike the alkali borates, Tg decreases rapidly as Na2S is added to B2S3. This effect, even in the presence of a rapidly increasing fraction of tetrahedrally coordinated borons, has been associated with the “over crosslinking” effect of the sulfide ion. Unlike the borate glasses where each added oxygen produces two tetrahedral borons, the conversion rate for the thioborates is between four and six. This behavior is suggested to result in the formation of local tightly-bonded molecular-like structures that exhibit less long-range network bonding than the alkali borate glasses. As a result, Tg decreases with added alkali in alkali thioborates rather than increases as in the alkali borate glasses.
The change in heat capacity at Tg, ΔCp(Tg) has been carefully measured and is found to also decrease dramatically as alkali sulfide is added to the glass. Again this effect is opposite to the trends observed for the alkali borate glasses. The decreasing ΔCp(Tg) occurs even in the presence of a decreasing Tg. We have tentatively associated the diminishing ΔCp(Tg) values to the decreasing density of the configurational states above Tg. This is attributed to the high coordination number and site specificity caused by the added alkali sulfide. The glassy state heat capacities were analyzed and found to reach ˜90% of the classical limiting DuLong-Petit value just below Tg for all glasses. This was used to suggest that the diminishing ΔCp(Tg) values are associated with a unique behavior in the system to become a liquid with very little change in the density of configurational states.
Measurement of the Glass Transition Temperature of Elastomer Systems
Authors: Sircar AK , Chartoff RP 
Published: March 2009

The glass transition temperature of polymers depends on both the experimental procedures and the experimental techniques used for its evaluation. However, the value of the published data is often diminished because these details are omitted. Examples are cited to show how the magnitude of differential scanning calorimetry (DSC) Tg depends on the Tg location and different calibration methods. Some comments are also made about thermomechanical analysis (TMA) and dynamic mechanical analysis (DMA) methods, although these are treated only briefly.
The factors that are unique to elastomer glass transition temperatures are: (1) the difficulties of calibration of the instruments at subambient temperature, (2) increase of Tg by the extent of vulcanization and filler loading, (3) differences due to microstructure and microphase separation, and (4) the availability of different grades of the same elastomer with different composition or added components, which alter their Tg. Thus, the literature value of Tg should include not only the calibration and procedure for the experiment, but also the exact name and description of the elastomer with the number index, the recipe used, and the cure conditions.
Glass Transition Measurements on Automotive Coatings by DSC, DMA, and TMA
Authors: Gupta MK 
Published: March 2009

The glass transition temperature (Tg) is a very useful parameter that characterizes the temperature dependence of the physical and mechanical properties of coatings. Differential scanning calorimetry (DSC), thermomechanical analysis (TMA), and dynamical mechanical analysis (DMA) were used to determine the Tg of automotive coatings.
DMA analyses were done on coatings deposited on a steel substrate in the fixed frequency mode, at frequencies of 0.01, 0.1, 1.0, and 10 Hz. Specimens were heated in either step mode (2°C) or ramp mode (5°C/min). TMA analyses were done either on coatings deposited on steel substrate or on free films at 5°C/min. DSC analyses were done at 5°C/min either on free films or on specimens that were sanded out from steel panel. Indium metal was used for the temperature calibration of DSC, TMA, and DMA. For one-coat films, the correlation between the temperature of midpoint in DSC, the onset temperature of penetration by TMA, and the onset temperature of loss modulus by DMA at 0.1 Hz was good. However, for multicoat films the Tg's for individual layers were visible only if their Tg's were far apart. It was possible in some cases to remove the top layer by scraping and analyzing the residual layers. The use of DSC, DMA, and TMA to determine the Tg's of different automotive coatings on metal substrate has been demonstrated, which is very useful in research and development, and problem solving.