bluuebunny/crossref_metadata_2025 huggingface dataset:
The Effect of Metal Atoms on Electron Ionization and Ammonia Chemical Ionization Mass Spectra of Metalloporphyrins: Implications for Geoporphyrin Analysis
Authors: Beato BD , Yost RA , Quirke JME
Published: December 2008

Eight metal complexes of octaethylporphyrin were analyzed by electron ionization (EI) and ammonia chemical ionization (NH3 CI) mass spectrometry. In both modes, features of the mass spectra of the metal complexes correlated well with the stability index of the metalloporphyrin, Si = [100(PE) (V)]/R, where PE is the Pauling Electronegativity of the metal, V is the valence of the metal, and R is the ionic radius of the metal. Metalloporphyrins with high stability indices produced abundant doubly charged fragments in the EI mode, and gave very little fragmentation with NH3 CI. Metalloporphyrins with low stability indices gave less intense doubly charged ions in EI, but gave abundant monopyrrolic fragments, and some dipyrrolic fragments under NH3 CI conditions. These results will be very valuable in geoporphyrin analysis, since it will now be possible to control the degree of fragmentation by inserting an appropriate metal into demetalated geoporphyrins.
On-Line, Mass Spectrometric Determination of Ammonia from Oil Shale Pyrolysis Using Isobutane Chemical Ionization
Authors: Crawford RW , Coburn TT , Miller PE , Oh MS
Published: December 2008

Ammonia is the predominant nitrogen-containing species formed during the pyrolysis of oil shale. An on-line method of determining ammonia was developed to study kinetics and chemistry of formation and evolution. While fragmentation of water interferes with electron ionization mass spectrometry, chemical ionization mass spectrometry using isobutane reagent gas gave excellent sensitivity and selectivity for ammonia. All transfer and sampling lines from the retort were heated to approximately 150°C. We successfully measured ammonia evolution from various oil shales retorted under a variety of conditions, including steam retorting.
Processing of High Resolution Mass Spectral Data by Use of Kendrick Masses in a Rectangular Array
Authors: Grigsby RD
Published: December 2008

Computer programs using the Kendrick scale for calculating masses are described for rapidly assigning elemental formulas to ions in high resolution mass spectra. Output from the programs, based on nominal mass Z series, is displayed in the form of a rectangular array having 14 columns and a variable number of rows, depending on the number of peaks in a spectrum. This layout permits formulas for the major ions to be identified almost as fast as the output is obtained from the printer. The array is especially useful for displaying the spectra of complex petroleum fractions, where molecular ions for one thousand or more components may be detectable. All programs except one are written in FORTRAN 77 and are available from the author.

The utility of the programs is illustrated with output from the mass spectrum of a fraction known to contain one-ring aromatic neutrals separated from the 200 to 425°C distillate of the Cerro Negro (Eastern Venezuela) heavy petroleum. The fraction was found to consist mostly of hydrocarbons with Z numbers ranging from - 6 through - 16, where Z is defined by the formula CnH2n+z. Homologs in the -8 and -10 Z series were the most abundant. Only traces of oxygen- and nitrogen-containing compounds were found, but sulfur compounds having formulas CnH2n+zS with Z ⩽ -4 were found in significant quantities. These types of compounds are in agreement with those anticipated from the HPLC method used in the fractionation of the distillate.
Softening Due to Void Nucleation in Metals
Authors: Hutchinson JW , Tvergaard V
Published: December 2008

The mechanics of void nucleation in an elastic-plastic solid stressed into the plastic range is studied with emphasis on the contribution of nucleation to softening of overall stress-strain behavior. Results for nucleation of an isolated spherical void in an infinite matrix under triaxial remote stressing are used to predict overall stress-strain behavior when interaction between voids is negligible. Calculations for nucleation of a void at a rigid spherical particle in a cylindrical cell model the simultaneous nucleation of a uniform distribution of voids. A strong dependence of the nucleation process on the matrix material specification is found when results based on isotropic hardening are contrasted with those based on kinematic hardening. At issue is the magnitude of the softening contribution due to void nucleation. This issue and the role of nucleation in promoting flow localization are discussed.
The Role of Heterogeneities in Fracture
Authors: Argon AS
Published: December 2008

Heterogeneities play a dual role in the mechanical behavior of materials. They alter the stiffness and plastic resistance of a solid, but also provide interfaces across which stresses are concentrated due to the accumulating deformation-induced misfit that can hasten cavitation and lead to eventual fracture. This paper discusses conditions of cavitation around hard particles in low-temperature ductile fracture of metals and alloys and in intergranular fracture during creep. Also, analogous, but complementary, roles of compliant particles and heterogeneity phases in the craze plasticity of glassy polymers are also surveyed.
Microstructure and the Fracture Mechanics of Fatigue Crack Propagation
Authors: Starke EA , Williams JC
Published: December 2008

Microstructure is the principal independent variable which can be used to control the fatigue crack growth rate (FCGR) once loading conditions and environment are established. Microstructure affects the FCGR through its influence on strain distribution (slip character), slip length, plastic zone size, and crack path. These factors, in turn, can influence both crack closure and the materials sensitivity to aggressive environments. This paper reviews the authors' perception of the current understanding of the effect of microstructure on FCGRs.
Environmentally Assisted Crack Growth in Structural Alloys: Perspectives and New Directions
Authors: Wei RP , Gangloff RP
Published: December 2008

Environmentally assisted crack growth (namely, stress corrosion cracking and corrosion fatigue) in alloys is one of the principal determining factors for durability and reliability of engineering structures. Over the past 20 years, activities in this area have transformed from screening and qualitative characterizations of the phenomena to quantitative assessment and scientific understanding. This work has enabled the recent development of life-prediction procedures.

In this paper, the contributions of fracture mechanics in this transformation are reviewed. Current mechanistic understanding of environmentally assisted crack growth by hydrogen embrittlement is summarized, and is placed in perspective. Applications to mitigate stress corrosion and corrosion fatigue cracking in marine environments are summarized. Outstanding issues and new directions for research are discussed.
Fracture Toughness in the Transition Regime for A533B Steel: Prediction of Large Specimen Results from Small Specimen Tests
Authors: Ingham T , Knee N , Milne I , Morland E
Published: December 2008

The results of an experimental test program to investigate methods of predicting the influence of specimen size on the cleavage fracture toughness of A533B-1 steel are presented. Three-point bend specimens from 10 to 230-mm thick were tested; to minimize scatter in the results, these were all extracted from a single plate of A533B, such that their crack tips lay on the midplane of the plate. A total of 217 tests were performed so that enough data could be obtained to allow statistical analysis.

At any one temperature there was considerable scatter in the results, which did not diminish with increasing specimen size. However, at a particular temperature, the mean or lower-bound fracture toughness at cleavage decreased with increasing specimen size. The fracture toughness was analyzed as a function of size and temperature using exponential curve fitting procedures, multiple linear regression analysis, Weibull statistics and the βIc correction, and the significance of each of these methods is reviewed. The size effect can be quantified in terms of a shift in temperature for a given toughness level. The shift, however, is dependent on toughness, being smaller at the higher levels of toughness, and there is a tendency toward saturation as the fully ductile state is approached.

The implications of this work in respect to obtaining data for use in structural integrity analysis is discussed.
Plastic Collapse in Part-Wall Flaws in Plates
Authors: Willoughby AA , Davey TG
Published: December 2008

Experimental results on plastic collapse stresses in flat plates containing partwall flaws have been collated. These are compared with two-dimensional limit load solutions, assuming both free rotation (pin jointing) and rigid restraint. Allowance for finite flaw lengths is made by calculating an effective flaw depth to thickness ratio, based on the area of the flaw divided by an effective sectional area. Few data on embedded flaws were found, and so an experimental program using diffusion bonded tension specimens containing internal slits was undertaken.

The results of this program, coupled with the analysis of experimental data on surface flaws, show that for surface flaws in sections experiencing some restraint, the assumption of rigid restraint is reasonable. For embedded flaws, pin jointing was assumed, rather than rigid restraint, since the equations are much simpler and the difference is smaller. The proposed correction for finite flaw length is shown to give good results, with overall safety factors under tensile loads in the range 1.08 to 1.64 being obtained. For highly work-hardening materials such as austenitic steels, the method overpredicts the collapse loads, due almost certainly to inappropriate estimates of flow strength.
Fracture Mechanics Model of Fatigue Crack Closure in Steel
Authors: Tanaka Y , Soya I
Published: December 2008

Fatigue crack propagation tests were performed on a high-strength steel with yield strength of 598 MPa under various stress ratios. A fatigue crack opening model, which contains both the effects of R and ΔK, was investigated based upon the cyclic elasto-plastic finite-element analysis (FEA) and the fracture mechanics approach with the small-scale yielding concept. Assuming the existence of the residual deformation in the wake of a crack, the crack opening stress-intensity factor can be calculated as the value at which the fatigue crack opening displacement becomes zero. Using this model, how R and ΔK affect U was investigated. The resultant formula for U contains two parameters, one for the plastic deformation at a crack tip, and the other for the oxide and the roughness in a fatigue crack. The effective stressintensity factor range, based on the measurements of crack opening loads, gives the same crack propagation behavior for various stress ratios. It is observed in experiments, however, that U depends on the stress ratio R and the stress-intensity factor range ΔK. The model successfully explains the experimental results. The fatigue crack propagation behavior under various stress ratios is described by the formula with five parameters, which can be obtained with only one specimen. The predicted crack propagation rates and threshold stress-intensity factor range agreed with empirical results. Therefore, the formula derived from this model may be applied well to the evaluation of fatigue crack extension.
Crack Opening Under Variable Amplitude Loads
Authors: Zwerneman FJ , Frank KH
Published: December 2008

Crack growth rate tests were conducted on eleven compact tension specimens of A588A steel plate to assess the ability of linear cumulative damage models to estimate fatigue life under load-time histories composed of cycles of variable amplitude and mean. Crack opening was monitored using a clip gage and through transmission ultrasonics. Crack growth rate results show that closely spaced overloads can cause acceleration; retardation occurs only if overloads are separated by many small cycles. Comparison of crack opening data to crack opening estimates based on Elber's closure model shows that the influence of crack opening on growth rate in constant-amplitude tests is less than predicted by the model, while the influence of crack opening in variable-amplitude tests is greater than predicted by the model.
Strain-Induced Hydrides and Hydrogen-Assisted Crack Growth in a Ti-6Al-4V Alloy
Authors: Gao S-J , Xiao H-Z , Wan X-J
Published: December 2008

The formation of strain-induced hydrides and the interaction of hydrides with crack growth in a Ti-6Al-4V alloy containing 790-ppm hydrogen have been studied by transmission electron microscopy (TEM) of thin-foil specimens stretched in situ. Three types of strain-induced hydrides were found: a crack tip hydride and two plate-like hydrides. The hydrides have either a face-centered tetragonal (fct) or a face-centered cubic (fcc) structure and are metastable. The formation and subsequent rupture of the hydrides at and in front of the crack tip were observed during crack growth. Hydrogen-assisted crack growth in Ti-6Al-4V alloys is discussed in terms of a hydride mechanism for cracking.
Threshold Crack Growth Behavior of Nickel-Base Superalloy at Elevated Temperature
Authors: Ashbaugh NE , Nicholas T
Published: December 2008

An experimental program was conducted to evaluate the effects of frequency and R on the near-threshold crack growth behavior of Inconel 718 at 649°C in laboratory air. Frequencies from 0.01 to 400 Hz and R from 0.1 to 0.9 were applied to compact tension [C(T)] and middle- or center-cracked tension [M(T)] specimens under decreasing-K conditions using computer-controlled test machines. Digital load-displacement data were obtained to determine crack length and closure load. The fatigue crack growth threshold in Inconel 718 at 649°C obtained using decreasing ΔK testing was generally associated with a crack arrest phenomenon which could be attributed to the buildup of oxides with time. Over the ranges of R and v used in this investigation, the growth rate behavior at the onset of crack arrest appears to be a combination of time-dependent and cyclic-dependent behavior. Even at 400 Hz, purely cyclic behavior was apparently never reached. For crack growth rate modeling, both frequency and stress ratio have to be incorporated in the characterization of ΔKth. Over the ranges of parameters tested, a cyclic threshold was approached at high frequencies and low R and a sustained load time-dependent threshold was obtained at high R, indicating that the cyclic contribution to the growth rate was negligible.
Corrosion and Hydriding of N Reactor Pressure Tubes
Authors: Lanning DD , Johnson AB , Trimble DJ , Boyd SM
Published: December 2008

The Hanford Site N Reactor core includes approximately 1000 Zircaloy-2 pressure tubes that pass horizontally through the graphite moderator and contain the fuel elements and pressurized water coolant. The overall tube length is 16.1 m, and the central fueled length is 10.6 m. Over the fueled length, the coolant temperature increases from 204 to 282°C (399 to 540°F). Moist helium is maintained in the gas gap between tube and graphite moderator.

Along the fueled length of recently examined tubes, the waterside oxide layer thickness increases uniformly from ∼3 μm (the preinstallation value) at the inlet end to a maximum of over 50 μm near the peak neutron flux location. The outer surface oxidation levels are approximately an order of magnitude less. The oxide thicknesses have steadily increased with operating time, which was verified by a tube removal and examination program that spanned the 25-year reactor lifetime.

Oxidation rates were calculated from the waterside oxide layer thickness data. The in-flux oxidation rates are clearly enhanced (at a given temperature) relative to ex-reactor Zircaloy oxidation rates and to out-of-flux rates on actual pressure tubes. The in-flux oxidation rate varies exponentially with absolute temperature, similar to ex-reactor rates. In addition, the in-flux oxidation rate at a given temperature increases significantly as the oxide layer thickness passes from <15 μm to >20 μm. This last trend is in qualitative agreement with recent observations from high-burnup light water reactor (LWR) fuel rods and with a “Thick-Film Hypothesis” derived from test reactor data on N reactor tube materials in low and high oxygenated coolants.

The hydrogen content in the tube wall along the fueled region follows the axial distribution of the oxide thickness. The hydrogen accumulation rate generally follows the oxidation rate. In particular, the hydrogen accumulation rate increases as the waterside oxidation passes from the thin-film (<15-μm) regime to the thick-film (μ20-μm) regime. The hydrogen content has a strong azimuthal distribution with the maximum occurring at the top of the tube, which is the lower temperature region. The hydrogen also has a strong radial distribution with the maximum occurring at the tube inner surface, which is the oxidizing (hydrogen source) surface and which is at the lower temperature.

In this paper, oxidation and hydriding trends are characterized, discussed, and analyzed in the light of current models and comparable LWR and ex-reactor data. Emphasis is given to results and insights generally applicable to in-reactor Zircaloy oxidation and hydriding.
Evaluation of Zircaloy-2 Pressure Tubes from NPD
Authors: Coleman CE , Cheadle BA , Causey AR , Chow PCK , Davies PH , McManus MD , Rodgers DK , Sagat S , van Drunen G
Published: December 2008

The pressure tubes of Canadian Deuterium Uranium (CANDU) reactors are monitored to evaluate their health. The main factors that affect their service life are changes in dimensions, shape, mechanical properties, and flaw tolerance. We have developed equip-ment and techniques to measure these properties and assess the health of the tubes. In this paper we describe the examination of the Zircaloy-2 pressure tubes of the Nuclear Power Demonstration (NPD) reactor. Their dimensional changes posed no problems. However, the combined effect of irradiation and the presence of radial hydrides caused the fracture toughness to decrease to such an extent that it would be difficult to assure leak-before-break in the future. Thus the reactor was closed down after 25 years of operation.
A Laboratory Method to Predict Hydriding Properties of Zirconium Alloys Under Irradiation
Authors: Johnson AB , Levy IS , Lanning DD , Gerber FS , Trimble DJ
Published: December 2008

A corrosion and hydriding test series on zirconium alloys in the Engineering Test Reactor G-7 loop demonstrated relatively large lot-to-lot and alloy-to-alloy differences in hydriding rates under irradiation. Similar differences were also found among irradiated Zircaloy-2 pressure tubes fabricated by three suppliers for the Hanford Site N Reactor. This substantial in-reactor hydriding data base and access to archive materials from these same alloys permitted an investigation of methods to reproduce the in-reactor hydriding orders-of-merit by an out-of-reactor method.

The out-of-reactor method selected for investigation consisted of autoclaving alloys in relatively concentrated (0.3 to 1.0 M) aqueous lithium hydroxide solutions. The test times ranged from 7 to 35 days, and the specimens were held at constant temperatures within the water reactor coolant temperature range (280 to 315°C). The in-reactor hydriding behavior for several lots of Zircaloy-2, one lot of Zircaloy-4, and one lot of Zr-2.5Nb was reproduced in the lithium hydroxide tests. The hydriding rates were compared on the basis of the ratio of hydrogen weight gain to oxide weight gain.

Potential applications of the method include the following: (1) screening to predict relative in-reactor hydriding behavior of zirconium based materials, (2) investigating compositional and fabrication variables that influence hydriding within a given zirconium alloy system, and (3) investigating hydriding mechanisms.
Development of a Mechanistic Model to Assess the External Corrosion of the Zircaloy Claddings in PWRs
Authors: Billot P , Beslu P , Giordano A , Thomazet J
Published: December 2008

Out-of-pile corrosion experiments form a part of the program implemented to progress in understanding power water reactor (PWR) fuel rod waterside corrosion. Thus, out-of-pile loop tests were performed in order to correlate the thermal/hydraulic and chemical environment of the fuel rods to the corrosion rates of the Zircaloy-4 cladding material. Comparison of corrosion data yielded by in-loop, PWR, and autoclave tests then made it possible to demonstrate the effects of heat flux on corrosion kinetics through the temperature gradient in the oxide layer. PWR corrosion data also showed that the activation energy corresponding to Zircaloy oxidation by water does not vary under neutron flux compared to out-of-pile conditions. The influence of irradiation is either a threshold phenomenon dependent on fast neutron flux or a factor related to the chemical environment (for example, inclusion of lithium by recoil effect caused by thermal neutrons). Different destructive examination techniques to characterize the zirconium oxide morphology and (Li/K) concentration profile in the oxide have allowed us to suggest a relationship between operating conditions, such as two-phase flow heat transfer, lithium hydroxide/potassium hydroxide (LiOH/KOH) levels at the metal-coolant interface, and the kinetics of the growing oxide film. Then, the corrosion model makes the following calculations possible: (1) the precise thermal/hydraulic conditions in the environment of the fuel rods in the core of a PWR; (2) the localized coolant pH and overconcentration of soluble species in the coolant under boiling regime and its influence on the waterside corrosion of the Zircaloy cladding; (3) the contribution of irradiation flux to the enhancement of the oxidation rate, and (4) the axial and azimuthal oxide thicknesses on fuel rods. Simultaneously, a study has consisted in correlating the behavior of the Zircaloy materials under different autoclave experiments, out-of-pile tests, and in-reactor conditions. The future objective is to include the metallurgical properties in the corrosion model.
Enhanced Low-Temperature Oxidation of Zirconium Alloys Under Irradiation
Authors: Cox B , Fidleris V
Published: December 2008

The linear growth of relatively thick (>300 nm) interference-colored oxide films on zirconium alloy specimens exposed in the Advanced Test Reactor (ATR) coolant at ⩽55°C was unexpected. Initial ideas were that this was a photoconduction effect. Experiments to study photoconduction in thin anodic zirconium oxide (ZrO2) films in the laboratory were initiated to provide background data. It was found that, in the laboratory, provided a high electric field was maintained across the oxide during ultraviolet (UV) irradiation, enhanced growth of oxide occurred in the irradiated area. Similarly enhanced growth could be obtained on thin thermally formed oxide films that were immersed in an electrolyte with a high electric field superimposed. This enhanced growth was found to be caused by the development of porosity in the barrier oxide layer by an enhanced local dissolution and reprecipitation process during UV irradiation. Similar porosity was observed in the oxide films on the ATR specimens. Since it is not thought that a high electric field could have been present in this instance, localized dissolution of fast-neutron primary recoil tracks may be the operative mechanism. In all instances, the specimens attempt to maintain the normal barrier-layer oxide thickness, which causes the additional oxide growth. Similar mechanisms may have operated during the formation of thick loosely adherent, porous oxides in homogeneous reactor solutions under irradiation, and may be the cause of enhanced oxidation of zirconium alloys in high-temperature water-cooled reactors in some water chemistries.
A Systematic Survey of the Factors Affecting Zircaloy Nodular Corrosion
Authors: Ogata K , Yoshitsugu M , Okubo T , Aoki T , Hattori T , Fujibayashi T , Inagaki M , Murota K , Kodama T , Abe K
Published: December 2008

Out-of-reactor corrosion tests in 10.3-MPa steam at temperatures between 490 and 530°C have been carried out on Zircaloy-2 tube specimens of various fabrication histories including archive specimens of the same tube lots as were used in the commercial boiling water reactor (BWR) to get data for comparison between in- and out-of-reactor nodular corrosion performances. Test conditions, such as temperature and duration, as well as material parameters, such as chemical composition, texture, and precipitates, were examined to clarify the relation to the nodular corrosion susceptibility.

The number density and size of nodules increased when tested at higher temperatures. Extending the test duration increased the nodule size, but not the number density. The archive tube lots showed different degrees of nodular corrosion in the out-of-reactor test and their relative rankings seemed to correlate with the visual ratings of in-reactor corrosion. A higher number density of precipitates tended to reduce the nodular corrosion susceptibility. It should be noted, however, that some lots constituted an exception to this, and the cause was sought in the tube manufacturing processes.
Effects of Alloying Element Distribution on the Nodular Corrosion of Zircaloy-2
Authors: Ogata K
Published: December 2008

The cause of material variety in the nodular corrosion susceptibility was investigated through measurements of the distributions of alloying element concentrations. A Zircaloy-2 specimen surface area of 5 by 5 mm was divided into a 500 by 500 square array of 10 by 10 μm spots, and the concentrations of alloying elements, tin (Sn), iron (Fe), chromium (Cr), and nickel (Ni), were measured on each spot and examined statistically.

No significant differences in the variance of tin concentrations, which were relatively uniform, were observed between specimens tested. However, the respective variances of iron, chromium, and nickel concentrations were larger than that of tin and differed between specimens. A specimen having a larger variance showed heavier nodular corrosion in steam corrosion tests. The measured low concentration spots were randomly distributed on the specimen surface and their frequency correlated with the nodule number density suggesting that a local area deficient in these elements could be one site for nodular corrosion.

Both (α + β)- and β-quenching homogenized the concentrations of iron, chromium, and nickel; hence these treatments improved the nodular corrosion resistance.
Beta-Quenched Zircaloy-4: Effects of Thermal Aging and Neutron Irradiation
Authors: Yang WJS , Adamson RB
Published: December 2008

Ziraloy-4, a zirconium base alloy used extensively as cladding and core structural materials in water-cooled nuclear reactors, was examined by transmission electron microscopy (TEM) after quench-and-aging treatments, neutron irradiation, and postirradiation annealing. Phase instabilities found after quench-and-aging treatments include: (1) formation of the metastable precipitate Zr4(Fe,Cr) during quench from the β-phase field and (2) dissolution of metastable Zr4(Fe,Cr) and formation of the stable precipitate Zr(Fe,Cr)2 during aging in the α-phase field after quench. Rapid precipitation of Zr(Fe,Cr)2 occurs on aging at 750°C. The initial crystallographic structure of the precipitate is cubic, but the hexagonal structure predominates after aging. Microhardness reflects the microstructural changes that occur during annealing, but nodular corrosion resistance remains excellent throughout, except at the extremes of annealing temperature and time.

Phase instabilities detected by transmission electron microscopy after irradiation include disappearance of the metastable precipitate Zr4(Fe,Cr) in the β-quenched matrix. A singlephase solid solution is apparently achieved in the irradiated, β-quenched matrix and is maintained to high fluences without new visible precipitation and segregation. Iron in the matrix precipitates out at grain boundaries as the Zeta-phase during postirradiation annealing at 560°C. Both chromium and iron precipitate out as Zr(Fe,Cr)2 intermetallics on annealing at 750°C. In addition to the phase instabilities, irradiation also causes c dislocation development.
Effects of Irradiation and Hydriding on the Mechanical Properties of Zircaloy-4 at High Fluence
Authors: Garde AM
Published: December 2008

Tension and burst tests were conducted on irradiated Zircaloy-4 charged with hydrogen. The investigated ranges of experimental variables were deformation temperatures, 298 to 673 K; fluence levels, 7 to 12 × 1021 n/cm2, E > 0.821 MeV; and hydrogen concentrations, 50 to 400 ppm. The data show a significant reduction in the elongation compared to the properties of Zircaloy-4 with lower levels of fluence and hydrogen concentration. Although the overall elongations of the specimens were low, the fracture surface examination showed evidence of ductility in the material and localized deformation bands were observed on the specimens deformed at higher temperatures. The inhomogeneous deformation bands, observed predominantly for deformation temperatures between 573 to 673 K, are consistent with the literature evidence of dislocation channeling in highly irradiated Zircaloy. Radiation anneal hardening was observed at the temperature interval of 573 to 623 K. Since the orientations of both the habit plane of hydrides in Zircaloy and the dislocation channels formed during deformation at ȼ600 K are close to the basal plane, hydrides appear to initiate fracture in the dislocation channels in highly irradiated Zircaloy containing quantities of hydrogen above the solubility limit. A failure mechanism involving hydride initiated fracture in dislocation channels is suggested for irradiated Zircaloy deformed at ȼ600 K. Mechanical property data on irradiated Zircaloy in recent literature appear to be consistent with the proposed failure mechanism. An alloy development program is suggested to enhance the ductility of highly irradiated Zircaloys.
Applications of Crystallographic Textures of Zirconium Alloys in the Nuclear Industry
Authors: Murty KL
Published: December 2008

This paper summarizes our recent work on thin sheets, thick-walled TREXs, and thin-walled tubings of Zircaloy materials with emphasis on texture analyses, orientation distribution functions, plasticity models, correlation of single crystal behavior to textured bulk materials as well as their application to in-reactor performance of cladding materials in LWRs. The mechanical anisotropy and strain localization were investigated on recrystallized Zircaloy-4 sheet using the grid method, which yielded the transverse contractile strain ratios (R,P), formability parameter B, critical strains to necking, and fracture. The anisotropy and formability parameters were also evaluated from texture data and crystallite orientation distribution function (CODF) using prism slip as the dominant deformation mode, and both the lower bound and Bishop-Hill analyses were considered. Excellent correlations were noted between the experimental results and lower bound model predictions.

Constant strain-rate impression tests were used to evaluate the directional dependence of the mechanical characteristics of recrystallized Zircaloy-2 TREX from which the mechanical anisotropy and formability parameters were derived. The poor correlation between the experimental results and plasticity-CODF model predictions is attributed to the large texture gradients of the thick-walled tube shells. These parameters determined at the mid-wall using the grid method, however, correlated excellently with the prism model.

Biaxial creep of cladding materials is considered in terms of creep loci at constant energy dissipation for CWSR Zircaloy-4 along with the results by Stehle et al. on recrystallized Zircaloy-4 and by Suzuki et al. on Zircaloy-2. Moreover, the anisotropic yield locus developed for Zircaloy-2 by Suzuki et al. is also considered. The minor compositional differences between the two alloys have negligible influences on their textures as well as their creep behaviors, and all of these results on the recrystallized materials agreed with the predicted creep locus based on prism slip. Quantitative correlations were made by appropriately adjusting the creep compliance. The creep behavior of CWSR cladding was quite different from the recrystallized and correlated with the assumption of basal slip dominance.

The application of creep anisotropy derived from CODF in predicting the out-of-pile and in-pile creep behaviors of fuel rod cladding is demonstrated by considering appropriate model equations for thermal and radiation creep components as well as radiation growth developed by Murty et al., Wilson et al., and Clevinger et al.
The Influence of Tin Content on the Thermal Creep of Zircaloy-4
Authors: McInteer WA , Baty DL , Stein KO
Published: December 2008

The influence of tin content on the unirradiated mechanical properties of zirconium alloys within the Zircaloy-4 specification has been analyzed. A cold-worked, stress-relieved (CWSR) commercial cladding was produced using similar thermo-mechanical processing encompassing tin contents ranging from 1.22 to 1.54%. Thermal creep testing, tension testing, contractile strain ratio (CSR) testing, and texture analysis were preformed over the range of tin contents. Creep testing was performed at 399°C (750°F), over a series of stress ratios and stress levels. The creep strength of Zircaloy-4 was strongly dependent on the tin content over the allowable composition range. The effect of tin was dependent on the stress state, with the 0:1 stress ratio (hoop stress:axial stress ratio) and 1:1 stress ratio showing greater effects than 2:1 stress ratio. The steady state strain rates increased by factors of 6, 5, and 2 for the 0:1, 1:1, and 2:1 stress states, respectively, as the tin content decreased toward the lower tin content limit of 1.20%. A generalized multiaxjal thermal creep equation was used to model the influence of tin content and to separate the anisotropy and stress dependence. The stress dependence and thermal activation energy were insensitive to alloy content; however, the anisotropy parameters measured under low strain rate conditions moved closer to isotropic conditions as the tin content decreased. It was concluded that the change in the creep anisotropy was due to a change in the predominant slip system from a predominantly basal slip at high tin contents to a mixed basal-prism slip at low tin contents.
Effects of High Neutron Fluences on Microstructure and Growth of Zircaloy-4
Authors: Garzarolli F , Dewes P , Maussner G , Basso H-H
Published: December 2008

Irradiation of Zircaloy affects its microstructure and macroscopical properties, for example, influencing its irradiation growth. To gain more insight into these phenomena, experimental fuel rods and growth specimens with various fabrication parameters were irradiated in a pressurized water reactor (PWR) to high fluences. Some of the growth specimens were exposed to a fast neutron fluence of up to 2.3 × 1022 cm-2 (⩾0.82 MeV) over a period of 10 years. Following exposure, the irradiation-induced alterations of the microstructure and the intermetallic precipitates were studied by optical microscopy (OM), scanning electron microscopy (SEM), and transmission electron microscopy (TEM). At a temperature of 300°C during irradiation to fluences up to 7 × 1021 cm-2, growth increases with increasing yield strength. Recrystallized material, which has a low yield strength, exhibits an increased growth rate at very high fluences (⩾1 × 1022 cm-2). Postirradiation annealing studies indicate that the early irradiation growth of the recrystallized material can be recovered, whereas the later accelerated growth does not seem to be recoverable.

At temperatures in the range of 330 to 350°C, the growth depends on the grain size, especially below 2 μm, and on the carbon-content. The effect of yield strength on growth was less at 330 to 350°C than at 300°C, probably because of an irradiation-induced recovery. Moreover, TEM showed that an irradiation-induced formation of dislocations with a c-component occurs at neutron fluences ⩾9 × 1021 cm-2, whereas dislocation loops or fine precipitates or both form at lower fluences.

The intermetallic precipitates observed in the microstructure of the unirradiated, initial material exhibit two types of intermetallics. One type contains (Fe + Cr + Zr) and the other type contains only (Fe + Zr). The effect of irradiation on those intermetallics depends on temperature. At ⩽300°C the (Fe + Zr)-type intermetallic precipitate dissolves at neutron fluences above 5 × 1021 cm-2. The (Fe + Cr + Zr)-type precipitates become more and more amorphous and release iron to the matrix resulting in a decreasing Fe/Cr ratio. The diameter and the number of the precipitates decrease with increasing neutron fluences at this temperature. Only a few small precipitates can still be observed after a neutron fluence of 1.5 × 1022 cm-2. At temperatures above 340°C the size of intermetallics increases because of irradiation enhanced ripening.
Accelerated Irradiation Growth of Zirconium Alloys
Authors: Griffiths M , Gilbert RW , Fidleris V
Published: December 2008

Sponge zirconium and Zr-2.5 wt% Nb, Zircaloy, or Excel alloys all exhibit accelerated irradiation growth compared with high-purity crystal-bar zirconium for irradiation temperatures between 550 to 710 K and fluences between 0.1 to 10 × 1025 n ∙ m-2 (E > 1 MeV). There is generally an incubation period or fluence before the onset of accelerated or “breakaway” growth, which is dependent on the particular material being irradiated, its metallurgical condition before irradiation, and the irradiation temperature.

Transmission electron microscopy has shown that there is a correlation between accelerated irradiation growth and the appearance of c-component vacancy loops on basal planes. Measurements in some specimens indicate that a significant fraction of the strain can be directly attributed to the loops themselves. There is considerable evidence to show that their formation is dependent both on the specimen purity and on the irradiation temperature. Materials that have a high interstitial-solute content contain c-component loops and exhibit high growth rates even at low fluences (<1 × 1025 n ∙ m-2, E > 1 MeV). For sponge zirconium and the Zircaloys, c-component loop formation and the associated acceleration of growth (breakaway) during irradiation occurs because the intrinsic interstitial solute (mainly, oxygen, carbon and nitrogen) in the zirconium matrix is supplemented by interstitial iron, chromium, and nickel from the radiation-induced dissolution of precipitates; iron is the most important element. Zr-2.5 wt% Nb and Excel alloys exhibit accelerated growth which has similar characteristics.
Creep Behavior of Zircaloy Cladding Under Variable Conditions
Authors: Matsuo Y
Published: December 2008

Various creep tests of Zircaloy cladding tubes under variable conditions were conducted to investigate which hardening rule can be applicable for the creep behavior associated with condition changes. The results show that the strain-hardening rule is applicable in general when either the stress or temperature conditions change, provided that a certain amount of creep strain recovery is observed in case of stress drop. In stress reversal conditions, however, “softening” of the material was observed. Strain rate after stress reversal is much higher than that predicted by the strain-hardening rule. Tn this case, the modified strainhardening model, considering a recoverable creep-hardening range together with the strain recovery, predicts the creep behavior well. The applicability of the model is ascertained through a verification test that includes stress reversal, strain recovery, stress changes, and temperature changes.
Use of PAM and Pressuremeters in Offshore Foundation Design
Authors: Brucy F , LeTirant P
Published: December 2008

The pressuremeter is an in situ investigation method and also describes the stress-strain behavior of the soil. The Self-Boring technique is now available for use in water depths up to 1000 m as the result of the development of the “PAM.” It consists principally of a seabed frame from which a measuring probe is made to penetrate into the seabed. Pressuremeter data and self-boring parameter logs are evaluated on the basis of the results acquired to date from different sites. Some comparative data are presented. Then all different ways to use pressuremeter data results in the design of foundations are reviewed. Fundamental analyses still have to face many problems. Correlations with other soil parameters are needed but must be used judiciously. Finally, direct design methods appear to be the most promising ones.
The Development of a Full Displacement Pressuremeter
Authors: Withers NJ , Schaap LHJ , Dalton CP
Published: December 2008

The Fugro Full Displacement Pressuremeter (FDPM) has been developed to make it easier to obtain offshore in-situ measurements of stress-strain properties which can be combined with the continuous profiling of electric piezocone penetration testing. The instrument is designed to follow behind a standard Fugro piezocone with a diameter of 43.7 mm. The prototype has a differential pressure capability of 10 MPa and a radial expansion limit of 50%.

Results of some preliminary field trials on land are reported and its future application offshore is discussed.

Continuing research with the prototype FDPM and conventional pressuremeters will improve both empirical and theoretical interpretation and extend the application of the data.
Numerical Analysis of Pressuremeter Tests by the Finite Element Method
Authors: Lassoudière FM , Zanier FB
Published: December 2008

The self-boring pressuremeter test offers an exceptional means to investigate in situ soil behavior. However, it is important to clarify as thoroughly as possible the conditions in which one can pass from the pressuremeter curve (probe volume-pressure relation) to a stress-strain curve characterizing the local behavior of the soil in the neighborhood of the probe.

This article presents numerical simulations of real pressuremeter tests to help assess the importance of the role played by the geometric characteristics of the probe employed, on the pressuremeter test and on its interpretation.
Pressuremeter Standard and Pressuremeter Parameters
Authors: Briaud J-L , Tucker LM , Makarim CA
Published: December 2008

Remarks are made in a first part on key issues in the performance of a pressuremeter test. These include the length to diameter ratio for the probes, monocell versus tricell probes, pressure versus volume increment procedure, volume and membrane calibrations, data reduction. In a second part a data base is presented of pressuremeter, cone penetrometer, standard penetration and undrained shear strength tests results. Correlation equations between the various parameters are given and the large scatter is shown. In a third part the magnitude of the pressuremeter modulus is discussed in light of experimental findings and theoretical developments. It is shown that considering the weakness of soils in extension changes the moduli values obtained by the theory of elasticity.
Correlations of LLT Pressuremeter, Vane, and Dutch Cone Tests in Bangkok Marine Clay, Thailand
Authors: Bergado DT , Khaleque MA
Published: December 2008

Three types of in-situ tests were performed in Bangkok marine clay, namely: Pressuremeter test, Field Vane test, and Dutch Cone test. The Pressuremeter test using the OYO LLT monocell probe with wash boring technique yielded the horizontal earth pressure at rest (Po), yield pressure (Py), limit pressure (pℓ), undrained Young's modulus (Eu), and undrained strength (Sup). The Field Vane test gave the undrained strength (Suv) while the Dutch Cone test yielded the cone resistance (qc) and local friction (fs). The tests were carried out in 5 sites in the campus of the Asian Institute of Technology (AIT) wherein the 3 uppermost subsoil layers consist of about 2 m thick weathered marine clay, about 8 m very soft marine clay and about 6 m thick stiff clay. In each site, each in-situ tests were done in 5 locations. The averaged in-situ soil parameters obtained were correlated. The correlations obtained have been confirmed, compared, and discussed in relation with past results.
Proposed Method for Application of Pressuremeter Test Results to Designing of Offshore Foundations
Authors: Bécue J-P , Brucy F , Le Tirant P
Published: December 2008

Generalized procedures for soil classification and routine analysis of offshore pile and shallow foundations, directly using self-boring pressuremeter (SBP) test results, are yielded with detailed charts, thus enabling straight application to dimensioning.

The proposed geotechnical classification is based on: — the soil identification coefficient β — and the net pressure p*20 Recommended practice for determination of unit skin friction and end bearing capacity of pipe piles account for phenomena such as critical depth effect and possible pile plugging.

Procedures for generation of lateral load-deflection curves are based on definite analogy between the pressuremeter test and a laterally-loaded pile.

Similarly, the ultimate bearing capacity of shallow foundations may be estimated straightly using SBP test results with empirical coefficients depending on the embedment depth and corrective factors accounting for load eccentricity and inclination and for foundation base shape.

For heterogeneous or multilayered soil profiles procedures are given to derive equivalent parameter values.
Pressuremeter and Deep Foundation Design
Authors: Briaud J-L
Published: December 2008

The rules of design for vertically and horizontally loaded piles on the basis of pressuremeter test results are reviewed. The pressuremeter test considered is the one where the pressuremeter probe is inserted in a prebored hole. The rules are then evaluated on the basis of a series of well-documented vertical and horizontal pile load tests. The accuracy of the predictions is shown and recommendations are made for future use.
Settlement Prediction Using the Pressuremeter
Authors: Lukas RG
Published: December 2008

At seven projects sites where a complete geotechnical investigation had previously been completed, settlement readings of the foundations were obtained after the structures were completed. The measured settlements were compared with the settlements predicted using the results of pressuremeter tests and the pressuremeter method of predicting settlements. A good correlation was observed between settlements predicted for isolated load points such as for spread footings or drilled piers and a poorer correlation was obtained for large loaded areas consisting of a raft foundation. At all seven project sites, the subsoils consisted of deposits where settlement is not time dependent after loading.
Design of Laterally Loaded Piles Using the Pressuremeter
Authors: Robertson PK , Hughes JMO , Campanella RG , Brown P , McKeown S
Published: December 2008

The pressuremeter is ideally suitable for determining the in-situ non-linear parameters for the design of laterally loaded piles. A method for designing laterally loaded piles using presuremeter data is presented. For driven displacement piles, which are commonly used offshore, the pressuremeter can be pushed into the soil in a similar full-displacement manner. Several case histories are presented to illustrate the proposed method.