bluuebunny/crossref_metadata_2025 huggingface dataset:
A Biological Risk Assessment Approach to Establishing Water Quality-Based Effluent Limits
Authors: Fava JA , Kapp RM , Gift JJ , Flynn CR , Del Pup JA
Published: March 2009

Once water quality criteria are derived by states for a designated use of a particular water body and approved by the U.S. Environmental Protection Agency, they become enforceable in-stream water quality standards. On rivers, these standards are usually applied to a designated low stream flow to establish water quality-based effluent limits. The design stream flow used most often is the Q7–10, the lowest 7-consecutive-day average flow that is expected to occur once in 10 years. By definition, the Q7–10 is generally exceeded in approximately 99 percent of the historical record. Therefore, setting effluent limits to continuously meet the in-stream standards designed for infrequent low flow periods, regardless of the actual flow conditions, adds a margin of safety to that already provided by the water quality standard.

The objective of this effort is to evaluate the design-stream-flow concept and the general relationships between water quality standards and effluent limits. An approach is presented to estimate the relative biological risks involved with applying instream standards to alternative stream flows. As an example, a predictive assessment of Pennsylvania's cyanide standard for the protection of warmwater fisheries was evaluated, using the lower Monongahela River as a model. Requirements for this assessment included hydrological, biological, and water quality data for the Monongahela River and an evaluation of the toxicological literature on cyanide.

The results of this assessment suggest that in setting standards for cyanide, the Q7–10 design flow needs to be employed only when the most biologically sensitive portion of the year corresponds with periods of potential low flow. At other times of the year, design flows greater than the Q7–10 can be used in standard setting. These preliminary findings provide a technically defensible site-specific basis for the dynamic application of water quality standards to more than one design stream flow. Such an approach can be developed by states to protect the most sensitive life-history events of aquatic species occurring during historically low-flow periods while still providing an equivalent degree of protection to the aquatic community during the remaining major periods of the year.
Influence of Hydrogen on Age-Hardening Processes in 15-5 Precipitation Hardened Stainless Steel
Authors: Murali J , Louthan MR , McNitt RP
Published: March 2009

The aging characteristics of 15-5 precipitation hardened stainless steel were altered when age-hardening took place in a hydrogen environment. The presence of hydrogen increased the peak hardness and decreased the time to achieve peak hardness. Furthermore, the hardness of the hydrogen-aged samples increased to a maximum value with time of storage at room temperature. These observations are discussed in terms of proposed mechanisms for hydrogen embrittlement.
Microstructure and Related Material Characteristics of Some Duplex Austenitic-Ferritic Alloys with Less Than 40 Percent Ferrite
Authors: Bodine GC , Sump CH
Published: March 2009

Duplex austenitic-ferritic stainless steel alloys with major composition variants were prepared as induction melted heats and were converted to tubing by centrifugal casting and cold pilger reduction. Ferrite content of the tubing ranged from 19 to 30 percent depending upon composition and heat treatment. The effects of composition and heat treatment variants on the characteristics of microstructure and related corrosion properties were determined.
Influence of Microstructure on the Mechanical Properties and Localized Corrosion of a Duplex Stainless Steel
Authors: Solomon HD , Devine TM
Published: March 2009

The alloy studied, U50, is a ferritic-austenitic duplex stainless steel. In addition to the two major phases (that is, ferrite and austenite), several additional phases form during low and intermediate temperature aging, namely, M7C3, M23C6, σ, χ, R, γ2, and α′. This study details the precipitation of these phases and their influence on the mechanical and localized corrosion properties. The sigma phase has the most deleterious influence on the impact properties. The α′ produces the largest increase in the yield and ultimate tensile strength. The precipitation of M23C6 and σ adversely affects the pitting resistance of U50 in 0.1NHC1 because of the accompanying chromium and molybdenum depletion of the matrix. The formation of α′ also severely reduces the chromium content of the ferrite phase and thereby inhibits its passivation. The large volume percent of ferrite in the alloy prevents intergranular corrosion that typically accompanies grain boundary precipitation of M23C6 in single-phase stainless steels.
Challenges Facing Tire Cord Engineers Today
Authors: Draves CZ , Skolnik L
Published: March 2009

The basic challenge facing tire cord engineers is to develop a better understanding of the relationships between tire cord properties and tire performance. This paper traces the historical development of tire cords; analyzes forecasts of tire cord consumption; discusses past and present market and societal goals; notes the complexities of relating tire cord properties to tire performance; discusses the optimization of tire cord tensile strength to burst and bruise a tire; and notes the importance of tire cord dynamic properties to power loss in tires.
Laboratory Machine to Evaluate the Resistance of Tire Cords (Textile or Steel) to Tensile Fatigue or Compressive Fatigue or Both
Authors: Canevari C , Lala AG
Published: March 2009

A device for measuring the fatigue resistance of tire reinforcing materials at pure tensile or compressive strain is described.

If a pure bending moment is applied to a specimen like the complex beam used in the Simoni-Canevari “bending dynamometer” the specimen deforms like an arc of a circle and will be subjected to pure tensile or compressive stresses according to the direction of the bending. After a mathematical study had shown the possibility of the construction, we thought of building a machine capable of bending this kind of specimen cyclically as an arc of a circle. With this machine we achieved compression or tension or both in cycles at different stress levels (both as regards the average value and range) by changing the length of the connecting rod and the crank.

The first results of the study of steel cord fatigue made on this device were related to belt fatigue performance of car tires. We have found: (a) on the tire, the indoor fatigue life measured at different lateral forces followed a trend that can be described by the curve in Fig. 1; (b) on the specimen, by increasing the strain on the cord, its life decreased with a similar law; (c) on the specimen, by appling dissymmetrical strains at equal total strain we obtained longer lives, with different behaviors if the mean strain were on the tensile side or on the compressive side; and (d) the visual aspects of the failures obtained with the machine were the same as those obtained in the tires tested on the road.
Physical Factors in Cord-to-Rubber Adhesion by a New Tire Cord Adhesion Test
Authors: Fielding-Russell GS , Nicholson DW , Livingston DI
Published: March 2009

The physical parameters affecting the force required to pull a cord from the coid-rubber specimen used in a new tire cord adhesion test (TCAT) were investigated using a variety of rubber compounds and tire cords. The cord pull-out force was proportional to the square roots of cord perimeter, specimen cross-sectional area, and Young's modulus of the rubber, as anticipated from theoretical considerations. The constant of proportionality involved the square root of the energy of adhesion. The value of the energy of adhesion calculated from the proportionality constant was confirmed by an independent peel test.
Dynamic Moduli of Continuous Filament Yarns Subjected to Low Frequency Excitation Superimposed on High Initial Longitudinal Strain
Authors: Zorowski CF , Smith ZP
Published: March 2009

Reported are the results of an experimental and theoretical investigation of the dynamic viscoelastic properties of twisted continuous filament yarn subject to low frequency longitudinal excitation superimposed on high initial strain. The object is to relate the effective dynamic mechanical properties of the constituent filaments and the geometry of the filaments in the structure. An analytical model is presented which defines this relationship based on the following principle assumptions: (1) the imposed dynamic longitudinal strain is propagated as a plane wave in the twisted yam structure, (2) filament locations within the yarn structure are constant radius helical paths, and (3) filament dynamic mechanical properties can be represented by a generalized Maxwell model. An analysis of the effects of filament to filament interactions within the yarn structure represented by a simple coulomb friction is also included in the model development. Experiments performed on 70 denier, 34 filament nylon 66 yarn using the Rheovibron DDV II Viscoelastometer shown that yarn dynamic mechanical properties are predictable in terms of the dynamic mechanical properties of the filaments and the geometry of the yarn structure using the developed model at levels where sufficient static strain is imposed to eliminate coulomb friction effects.
Role of Tire Reinforcements on Composite Static and Dynamic Characteristics
Authors: Vorachek JJ
Published: March 2009

The structural characteristics of orthotropic and anistropic composites made of several tire belt reinforcements and rubber are measured and reported. Characteristics are obtained as a function of strain level and ply angle for one- and two-ply composites. Hysteretic loss data under sinusoidal cycling at various initial strain levels are reported. Photoelastic experimental analysis techniques for measuring strains are discussed. An electrohydraulic tester with strain gage extensometers and a reflection polariscope were utilized in the studies. Composite structural characteristics affect tire deformations and, consequently, the stresses that are developed in tire components as well as heat build-up and rolling resistance.
Viscoelastic Properties of Tire Cords Under Conditions of Rolling Tires
Authors: Kwon YD , Sharma RK , Prevorsek DC
Published: March 2009

An apparatus is described to measure the viscoelastic properties of greige and tensilized cords at frequencies, strain-amplitudes, pretensions, and temperatures which exist in tires during service. It is shown that the response of cords is nonlinear and time dependent. Properties of polyethyleneterephthalate (PET) cords are presented and the effects of tensilizing conditions and curing of tires are discussed. It is shown that tensilizing conditions and curing conditions have an important effect on dynamic modulus and loss factor.
Prediction Methods for Fatigue Crack Growth in Aircraft Material
Authors: Schijve J
Published: March 2009

In the first part of the paper a survey is given of relevant knowledge on fatigue crack growth and qualitative and quantitative understanding of predictions. Aspects of cycle-by-cycle predictions and characteristic K prediction methods are discussed. In the second part recent work on prediction problems is reported. This includes (a) crack growth under flight-simulation loading with crack closure measurements, (b) predictions for flight-simulation loading based on a constant crack opening stress level, and (c) crack growth under pure random loading with different Srms-values, two irregularities and two crest factors.

The random load tests were also carried out to explore the usefulness of Krms. The paper is concluded with some indications for future research and a number of conclusions.
Fatigue Crack Propagation in Nylon 66 Blends
Authors: Hertzberg RW , Skibo MD , Manson JA
Published: March 2009

Fatigue crack propagation (FCP) rates were measured in nylon 66, an impact-modified nylon 66, and in blends of the two resins as a function of the stress intensity factor range ΔK and cyclic frequency. Significant reductions in FCP rates were observed with increasing additions of the impact-modified polymer to pure nylon 66, though the relative ranking of the various blends was found to depend on the magnitude of ΔK and test frequency. These differences were related to specimen heating associated with certain blend compositions and high ΔK levels. Crack tip temperatures increased with increasing ΔK level and were as high as 125°C (257°F) in the impact-modified nylon 66 that had been moisture equilibrated at room temperature. Other tests revealed that this material represents the first polymeric solid to exhibit higher fatigue crack growth rates with increasing cyclic frequency.
Tensile Cracks in Creeping Solids
Authors: Riedel H , Rice JR
Published: March 2009

The aim of the paper is to answer the question: which loading parameter determines the stress and strain fields near a crack tip, and thereby the growth of the crack, under creep conditions? As candidates for relevant loading parameters, the stress intensity factor KI, the path-independent integral C*, and the net section stress σnet have been proposed in the literature. The answer, which is attempted in this paper, is based on the time-dependent stress analysis of a stationary crack in Mode I tension. The material behavior is modeled as elastic-nonlinear viscous, where the nonlinear term describes power law creep. At the time t = 0, load is applied to the cracked specimen, and in the first instant the stress distribution is elastic. Subsequently, creep deformation relaxes the initial stress concentration at the crack tip, and creep strains develop rapidly near the crack tip. These processes may be analytically described by self-similar solutions for short times t.

An important result of the analysis is that small-scale yielding may be defined. In creep problems, this means that elastic strains dominate almost everywhere except in a small “creep zone” which grows around the crack tip. If crack growth ensues while the creep zone is still small compared with the crack length and the specimen size, the stress intensity factor governs crack growth behavior.

If, however, the calculated creep zone becomes larger than the specimen size, the stresses become finally time-independent and the elastic strain rates can be neglected. In this limiting case, the stress field is the same as in the fully-plastic limit of power law hardening plasticity that has been treated in the literature. The loading parameter that determines the near tip fields uniquely is then the path-independent integral C*.

It should be emphasized that KI and C* characterize opposite limiting cases. Which case applies in a given situation can be decided by comparing the creep zone size with the specimen size and the crack length. Criteria for small-scale yielding are worked out in several alternative forms. Besides several methods of estimating the creep zone size, a convenient expression for a characteristic time is derived also, which characterizes the transition from small-scale yielding to extensive creep of the whole specimen.
A Critical Examination of a Numerical Fracture Dynamic Code
Authors: Hodulak L , Kobayashi AS , Emery AF
Published: March 2009

After upgrading the energy dissipation algorithm, numerical experiments were conducted to assess the reliability of the explicit dynamic finite element code, HCRACK. Two dynamic fracture specimens (that is, the wedge-loaded rectangular double cantilever beam (RDCB) specimen and the wedge-loaded tapered double cantilever beam (TDCB) specimen), which were studied experimentally by Kalthoff, Beinert, and Winkler, were then analyzed with this updated fracture dynamic code. Using the experimentally determined dynamic fracture toughness, KID, versus crack velocity, ˙a, relation, the RDCB specimen was analyzed first by the “propagation method” where good agreements between calculated and measured KID versus a relations were observed. The calculated a versus time, t, relation was then used as input data in the “generation method” where the resultant KID were virtually identical to those obtained in the propagation method. Error analyses of the generation method also were made first by using the experimentally determined a versus t relation and secondly by artificially perturbing this relation.

A TDCB specimen was then analyzed with both the propagation and generation methods by using the KID versus ˙a relation established for this specimen and the measured a versus t relation, respectively. The computed KID obtained by both methods were in good agreement with the experimental results, showing that either approach can be used in analyzing fracture.
Elastic-Plastic Analysis of Growing Cracks
Authors: Rice JR , Drugan WJ , Sham T-L
Published: March 2009

In an extension of earlier studies by Rice and Sorensen, a discussion is presented on the elastic-plastic stress and deformation fields at the tip of a crack which grows in an ideally plastic solid under plane strain, small-scale yielding conditions. The results of an asymptotic analysis suggest the existence of a crack-tip stress state similar to that of the classical Prandtl field, but containing a zone of elastic unloading between the centered fan region and the trailing constant stress plastic region. The near tip expression for the rate of opening displacement δ at distance r from the growing tip is found to have the same form suggested by Rice and Sorensen ˙δ=α˙J∕σo+β(σo∕E)˙aln(R∕r) but now the presence of the elastic wedge causes β to have the revised value of 5.08 (for Poisson ratio ν = 0.3). Here, a = crack length, σo = yield strength, E = elastic modulus, and J denotes the far-field value, namely, (1 − ν2)K2/E for the small scale yielding conditions considered. The parameters α and R cannot be determined from the asymptotic analysis, but comparisons with finite element solutions suggest that, at least for small amounts of growth, α is approximately the same for stationary and growing cracks, and R scales approximately with the size of the plastic zone, being about 15 percent to 30 percent larger. For large scale yielding it is argued that a similar form applies with possible variations in α and β, at least in cases which maintain triaxial constraint at the crack tip, but in the fully yielded case R is expected to be proportional to the dimension of the uncracked ligament. The model crack growth criterion of Rice and Sorensen, requiring a critical δ at some fixed r from the tip, is reexamined in light of the more accurate solution. The results suggest that the J versus Δa relation describing growth will be dependent on the extent of yielding, although it is suggested that this dependency might be small for highly ductile materials, provided that a similar triaxial constraint is maintained in all cases.
A J-Integral Approach to Development of η-Factors
Authors: Paris PC , Ernst H , Turner CE
Published: March 2009

Relating work done on a notched or cracked test piece directly to other fracture parameters, such as the J-integral, has been of interest at least since the development of the Charpy test. In this paper relationships between J and work are explored. The conditions for the existence of direct relationships are explained, and some cases where such relationships do not exist are observed. Moreover, these relationships are explored in terms of Turner's η-factors, which are useful both in J-integral test analysis methods and for structural analysis.
Temperature Dependence of the Fracture Toughness and the Cleavage Fracture Strength of a Pressure Vessel Steel
Authors: Kotilainen H
Published: March 2009

A new model for the temperature dependence of the fracture toughness has been sought. It is based on the yielding processes at the crack tip, which are thought to be competitive with fracture. Using this method a good correlation between measured and calculated values of fracture toughness has been found for a Cr-Mo-V pressure vessel steel as well as for A533B. It has been thought that the application of this method can reduce the number of surveillance specimens in nuclear reactors.

A method for the determination of the cleavage fracture strength has been proposed. It can be measured either with low temperature tensile tests or with slow bend tests of Charpy V-notch specimens.
Crack Analysis of Power Hardening Materials Using a Penalty Function and Superposition Method
Authors: Yagawa G , Aizawa T , Ando Y
Published: March 2009

Crack analysis is performed for plates characterized by the power hardening material law. A new superposition method of the analytical and the finite element models is proposed with the use of the penalty function, which is frequently adopted to solve the optimization problems. The characteristic distributions of the stress and strain around the crack tip are calculated and compared with the analytical results. Numerical discussion is also made regarding the effects of the crack length to plate width ratio and the power exponent in the hardening law on the nondimensional values of the J-integral, the crack opening displacement, and the residual load point displacement.
On the Equivalence Between Semi-Empirical Fracture Analyses and R-Curves
Authors: Orange TW
Published: March 2009

This paper examines the relationship between several semi-empirical fracture analyses (SEFA) and the R-curve concept of fracture mechanics. The conditions for equivalence between a SEFA and an R-curve are derived. A hypothetical (imaginary) material is employed to study the relationship analytically. Equivalent R-curves (ERC) are developed for real materials using data from the literature.

For each SEFA there is an ERC whose magnitude and shape are determined by the SEFA formulation and its empirical parameters. If the R-curve is indeed unique, then the various empirical parameters cannot be constant, and vice versa. However, for one SEFA the differences are small enough that they may be within the range of normal data scatter for real materials.
A Modification of the COD Concept and Its Tentative Application to the Residual Strength of Center Cracked Panels
Authors: Schwalbe K-H
Published: March 2009

Simple assumptions are used to derive analytical expressions for the crack-tip opening displacement of center cracked tension panel (CCT) specimens with finite width. The formulas obtained thereby are used to describe the fracture behavior of CCTs of aluminum alloys. The results of 83 tests show that the crack opening displacement (COD) concept yields reasonable assessment of the fracture behavior of thin sheet material. The advantages and limitations are discussed.
Texture Measurement Techniques for Zircaloy Cladding: A Round-Robin Study
Authors: Lewis JE , Schoenberger G , Adamson RB
Published: March 2009

A round-robin study of the texture of Zircaloy tubing was conducted. Experimental techniques and texture determination results from 14 independent laboratories are presented. Results are consistent and reproducible, as determined both qualitatively (pole figures) and quantitatively (f-parameters). It was concluded that reliable X-ray diffraction techniques exist which describe the texture and that results from the participating laboratories are comparable. A number of parameters which can affect texture results are also discussed.
Application of Hydrostatic Extrusion to Fabrication of Zircaloy Tubing
Authors: Nagai N , Kakuma T , Matsushita T , Kimpara M
Published: March 2009

Preliminary experiments in the extrusion of Zircaloy tubing using both cold and hot hydrostatic extrusion processes were carried out.

In the cold hydrostatic extrusion, a maximum extrusion ratio of five could be obtained, but it should be limited to a maximum of three to prevent the occurrence of galling. When the cold hydrostatic extrusion process was applied to the final pass of cold reducing, the properties of the obtained tubes were nearly identical to those of the current boiling water reactor cladding tubes in spite of the difference of the crystallographic texture of the tubes.

Application of the newly developed hot hydrostatic extrusion process to the extrusion of tube shells resulted in an increase of the extrusion ratio to three times that of the conventional direct extrusion. The tubing processed from hydrostatically extruded tube shells at the higher extrusion ratios showed higher strength and lower ductility than those of lower extrusion ratios in the tension tests. In the case of the burst tests, however, the ductility was higher in the tubes processed from the tube shells of the higher extrusion ratios.
New Intermetallic Compounds in Zircaloy-4
Authors: Grange JM , Charquet D , Moulin L
Published: March 2009

The precipitation of intermetallic compounds in Zircaloy-4 has been studied by transmission electron microscopy. The classical precipitates with a ZrCr2 lattice have been observed. In addition to these precipitates, a hexagonal phase with lattice parameters a = 7.9 Å and c = 3.3 Å can be developed by quenching from the temperature range 840 to 870°C. This phase is metastable and transforms into a zirconiumiron compound by aging at 600 to 650°C.
Long-Term Test Results of Promising New Zirconium Alloys
Authors: Castaldelli L , Fizzotti C , Lunde L
Published: March 2009

A series of new alloys has been long-term tested in different reactors and environments together with other alloys, including Zr-2.5Nb, Ozhennite 0.5, and Zircaloy-2. One of the new alloys with the composition of Zr-1Nb-1Sn-0.5Fe has significantly improved properties.

The zirconium-niobium alloys have corrosion properties similar to Zircaloy-2 in the temperature range 240 to 400°C while they are better at 450°C and above. Conditions leading to nodular corrosion in Zircaloy-2 did not produce nodular attack on the Zr-1Nb-1Sn-0.5Fe alloy, or on Zr-2.5Nb. The niobium-containing alloys fail to suffer intergranular cracking in iodine-methanol solution even when stressed to 80 percent of their yield strength for more than 60 days. The other alloys failed at 30 percent of yield strength in a few hours. Preliminary iodine-argon iodine-pressurized burst tests indicate some improvement for the Zr-1Nb-1Sn-0.5Fe alloy compared with Zircaloy-2 with a five to ten times increase in time to failure for the same stress level.

Elongation was markedly reduced by irradiation in all the alloys. Uniform elongations of about 1 percent were observed in the 2.5Nb alloy while the highest uniform elongation of 2 to 3 percent was shown by the Zr-1Nb-1Sn-0.5Fe alloy.
Effects of Temperature and Pressure on the In-Reactor Creepdown of Zircaloy Fuel Cladding
Authors: Hobson DO , Thoms KR , Dodd CV , van der Kaa T
Published: March 2009

Descriptions and results for seven of the eight in-reactor creepdown tests of Zircaloy fuel cladding, which were part of a joint program between the U.S. Nuclear Regulatory Commission and Energieonderzoek Centrum Nederland, are presented. These tests were conducted to study the behavior of Zircaloy fuel cladding under conditions that approximate those found in an operating pressurized-water power reactor.

Radial surface displacement values as functions of time, average diametral-circumferential strain as a function of time, and isochronal deformation surfaces are presented. Tests were conducted at 343°C with external pressures from 13.3 to 18.7 MPa. Three of the specimens were subjected to stress reversal during their test runs, wherein they were pressurized internally from 3.5 to 6.9 MPa. Fast flux [E > 1.0 MeV (0.2 pJ)] ranged from 3.8 × 1017 to 5.0 × 1017 neutrons (n)/(m2·2). Maximum fluence was approximately 7 × 1025 n/m2.

The most important conclusion to be drawn from this study involves the deformation of the cladding during testing. Contrary to similar tests conducted out-of-reactor, the in-reactor specimens did not deform uniformly, that is, by diametral contraction and smooth ovalization. Rather, the deformation surfaces were nonuniform with hills and valleys being formed at irregular intervals. This implies that conventional concepts of creep rate and simplified modeling procedures will not work for predicting cladding behavior. Sufficient data have been generated in this program to supply modelers with detailed descriptions of the cladding surface shapes from which new interpretations can be derived to predict cladding behavior.
High-Strength, Creep-Resistant Excel Pressure Tubes
Authors: Cheadle BA , Holt RA , Fidleris V , Causey AR , Urbanic VF
Published: March 2009

Pressure tubes for CANada Deuterium Uranium Pressurized Heavy Water reactors are made from Zr-2.5Nb by extruding preheated hollow billets into tubes that are cold-worked 30 percent to size. The fabrication process produces fine elongated α-grains with a high dislocation density which makes a large contribution to the tensile strength of the tubes but increases in-reactor creep and growth rates.

The alloy Excel (Zr-3.5Sn-0.8Mo-0.8Nb) is stronger and more creep resistant than Zr-2.5Nb and is being developed as a pressure tube material. Tubes have been fabricated that are as strong as the Zr-2.5Nb tubes but they have more equiaxed α-grains with much lower dislocation densities. The tubes corrode faster than the Zr-2.5Nb tubes and will require 0.1 mm more corrosion allowance on the 4.1-mm-thick walls. However, their in-service axial elongation and diametral expansion due to irradiation creep and growth will be 70 percent less than the Zr-2.5Nb tubes.
Zircaloy-4 Cladding Deformation During Power Reactor Irradiation
Authors: Franklin DG
Published: March 2009

The four primary Zircaloy fuel cladding deformation phenomena—axial elongation, circumferential creep, ovalization, and ridging—have been investigated for fuel irradiated in four modern pressurized water reactors. The axial elongation of fueled and nonfueled rods is examined by a regression fit for dependence on fluence, clad texture, yield stress, applied stress and, for fuel rods, fuel pellet length to diameter ratio. For fueled rods, only fluence and stress are found to be important, although the range of texture data is small. For nonfueled rods, the texture is found to influence elongation.

The circumferential creep strain data from nonfueled rods are also analyzed by a regfression analysis to estimate the effects of time, flux, applied stress, temperature, yield stress, and texture. Time and flux have weaker than linear influence on strain, while the stress has a stronger than linear influence. The strain rate is almost athermal. The creep strain clearly increases with preirradiation yield strength. However, the primary difference is between recrystallized and stress-relief-annealed cladding with the degree of retained cold work having less effect. The creep rate clearly decreases with an increase in the angle between the basal poles and the radial direction. The effects of carbon content and grain size are also discussed.

Ovalization of fueled and nonfueled rods is observed although analysis is difficult. The sensitivity of post-irradiation ovality to initial ovality and the relatively large uncertainty in initial ovality have precluded effective regression analysis although the general effects of applied stress, yield stress, and initial ovality are given. Clad ridging develops in fueled rods, usually in a time period between one and two reactor cycles and almost always after three cycles. However, the maximum ridge height occurs before the end of two reactor cycles.
An Experimental Study of the Deformation of Zircaloy PWR Fuel Rod Cladding Under Mainly Convective Cooling
Authors: Hindle ED , Mann CA
Published: March 2009

In a loss-of-coolant accident (LOCA) the temperature of the cladding of some fuel rods may rise to levels [650 to 810°C (1202 to 1490°F)] where the ductility of Zircaloy is high (∼80 percent). The net outward pressure which will obtain if the coolant pressure falls to a small fraction of its normal working value produces stresses in the cladding which can result in large strain through secondary creep. An earlier study of the deformation of specimens of pressurized water reactor (PWR) Zircaloy cladding tubing 450 mm (18 in.) long under internal pressure had shown that strains of over 50 percent could be produced over considerable lengths (greater than 20 tube diameters). Extended deformation of this sort might be unacceptable if it occurred in a fuel assembly. The previous tests had been carried out under conditions of uniform radiative heat loss, and the work reported here extends the study to conditions of mainly convective heat loss, believed to be more representative of a fuel assembly following a loss of coolant.

Zircaloy-4 cladding specimens 450 mm (18 in.) long were filled with alumina pellets and tested at temperatures between 630 and 915°C (1166 and 1679°F) in flowing steam at atmospheric pressure. Internal test pressures were in the range 0.69 to 11.0 MPa (100 to 1600 lb/in.2). Maximum strains were observed of the same magnitude as those seen in the previous tests, but the shape of the deformation differed; in these tests the deformation progressively increased in the direction of the stream flow.

The length of cladding strained 33 percent or more was greatest (about 20 times the original diameter) when the initial pressure was 1.38 ± 0.17 MPa (200 ± 25 lb/in.2). It is though that this results from oxidation strengthening of the surface layers acting as an additional mechanism for stabilizing the deformation or partial superplastic deformation, or both. For adjacent rods in a fuel assembly not to touch at any temperature, the pressure would have to be less than about 1 MPa (145 lb/in.2). These results are compared with those from multirod tests elsewhere, and it is suggested that heat transfer has a dominant effect in determining deformation. The implications for the behavior of fuel elements in a LOCA are outlined.
Effect of Hydrogen on the Oxygen Embrittlement of Beta-Quenched Zircaloy-4 Fuel Cladding
Authors: Seiffert SL
Published: March 2009

Zircaloy cladding embrittlement was evaluated from data derived from the postirradiation examination of 47 light-water reactor type fuel rods irradiated under postulated accident conditions. The previously irradiated and unirradiated rods were tested in 15 separate in-pile experiments in the Power Burst Facility reactor at the Idaho National Engineering Laboratory as part of the Thermal Fuels Behavior Program. Film boiling conditions ranged in duration from a few seconds to about 15 min, with cladding peak temperatures ranging from 1315 to ≥ 2100 K in the most severely oxidized Zircaloy. Quenching from film boiling temperatures through the β → α′ phase transformation was at rates of about 50 to 100 K/s, depending on test conditions.

The Zircaloy-4 cladding showed rapid oxygenation of the β-phase Zircaloy and hydriding in excess of the pretest characterization. Cladding embrittlement in the intact rods was consistent with previously established oxygen embrittlement criteria. Fuel rods operated with a cladding defect were embrittled to a greater extent than intact rods oxidized under similar conditions. A modified background prior β-phase and precipitation of rim-α was typically observed in the failure region of breached rods. The fracture resistance of breached rods appears to be related to enhanced hydrogen absorption and its influence on both the β-phase transformation and the α′-morphology during rapid (∼ 100 K/s) quenching.
A Comparison of the High-Temperature Oxidation Behavior of Zircaloy-4 and Pure Zirconium
Authors: Pawel RE , Campbell JJ
Published: March 2009

Oxidation rate data for Zircaloy-4 in steam under isothermal conditions in the temperature range 1000 to 1500°C indicate that the kinetics of layer growth and oxygen consumption can be described by virtually ideal parabolic behavior. Thus, the growth of the two product phases, oxide and oxygen-stabilized α, is presumed to be controlled by diffusion processes leading to uniform layer thickening. We have measured the oxidation rate of pure, arc-melted, crystal-bar zirconium under similar conditions and have found differences in the reaction characteristics compared with Zircaloy-4. At temperatures from 1098 to 1416°C, while parabolic kinetics are still observed, the growth rates for both phases are measurably different. Our analysis of these data in terms of a multilayer diffusion model suggests that the effective chemical diffusion coefficient for oxygen in the oxide phase has been altered. Despite the kinetic differences, however, the analysis also concludes that the diffusion coefficient of oxygen in the α layers is identical, a finding consistent with the results of independent measurements.

In addition to the decreased oxygen diffusivity in the oxide phase on pure zirconium compared with that on Zircaloy-4, a higher activation energy was also observed, implying that some mechanistic differences exist. Without additional information, it is not possible to attribute these differences to changes in the oxide defect structure resulting from alloying. However, significant morphological and grain size differences exist in the columnar oxide growing on the two materials, and it is possible that the relative contributions to oxide growth from short-circuit diffusion differ in the two oxides.
Long-Term In-Reactor Corrosion and Hydriding of Zircaloy-2 Tubing
Authors: Hillner E
Published: March 2009

Three original Zircaloy-2 clad blanket fuel bundles from the pressurized-water reactor (PWR) at the Shippingport Atomic Power Station were discharged after continuous exposure during Cores 1 and 2. Detailed visual examination of these components after ∼6300 calendar days of operation (51 140 effective full power hours) revealed only the anticipated uniform light gray (posttransition) corrosion products with no evidence of unexpected corrosion deterioration, fuel rod warpage, or other damage. All corrosion films were found to be tightly adherent to the underlying cladding.

An extensive destructive examination of a selected fuel rod from each of three fuel bundles produced, as expected, significantly greater end-of-life rod average oxide film thicknesses when compared with corresponding values calculated from the time-temperature history of each component, employing a set of empirical equations generated from the out-of-pile (autoclave) testing of Zircaloy coupons. It is shown that the pretransition region and the time to transition are in adequate agreement with the empirical equations generated from the ex-reactor data but that there is a significant acceleration of the posttransition corrosion rate due to the irradiation exposure. Post-transition corrosion rate data were used to develop an empirical expression of the form R′=A(φ)n·R where R′ is the in-reactor posttransition corrosion rate for Zircaloy-2 tubing, A and n are experimentally determined constants, φ is the posttransition fast flux exposure, and R is the posttransition temperature-dependent corrosion rate generated from exreactor (autoclave) testing. The Multipurpose Extended Life Blanket Assembly cladding in the mid-sections of the rods (α microstructure) was found to have corroded at a rate that is approximately 25 percent greater than the corresponding welded end cap regions (β-quenched struture).

It has been observed that the total hydrogen content of the cladding was less than that calculated from the ex-reactor expressions, using the measured oxide film thickness. It has also been found that the hydrogen pickup per unit weight gain is two to three times greater in the late posttransition period than that observed in the early posttransition region, possibly casting doubt on the validity of the application of the ex-reactor hydrogen pickup expression (that is, a constant ΔH/Δ0 ratio for the entire posttransition region) to in-reactor exposures.
Stress Relaxation of Steel Tendons Used in Prestressed Concrete Under Conditions of Changing Applied Stress
Authors: Glodowski RJ , Hoff GE
Published: March 2009

Several methods have been proposed for predicting the total prestress loss in prestressed concrete structures. Inherent in all of these methods is the concept that the applied elastic strain on the steel tendons changes with time due to creep and shrinkage of concrete. A procedure most often used to determine the steel tendon's stress relaxation contribution to total prestress loss is a time iteration technique. The stress relaxation that occurs in each time interval is predicted from an equation describing stress relaxation as a function of time and initial stress level. This equation is normally derived from data obtained from constant-strain tests as per ASTM E328. During the time iteration program, however, the initial stress level is different for each time interval because of changing elastic strains in the steel tendons due to concrete creep and shrinkage. In some procedures under consideration by the prestressed concrete industry, the actual stress on the tendon at the start of each time interval is assumed to be the correct value for initial stress. Total relaxation is then determined by a summation of the relaxation during each time interval.

The object of the present research is to investigate the effects of variable applied elastic strain on stress relaxation results during a continuous test and to evaluate procedures for assessing these effects. To accomplish this, stress relaxation tests were carried out on 6.35-mm (0.250-in.) diameter prestressing wire. Results of variable elastic strain application during the test were compared with constant-strain stress relaxation data. Based on these results, a new procedure is proposed for predicting the effects of variable elastic strain on the stress relaxation-time relationship. This new procedure incorporates the effect of stress relaxation in prior time intervals on predicted stress relaxation in a given interval. This is accomplished analytically by defining an “effective initial stress” and an “effective time” to be used in the mathematical expression for stress relaxation during each time interval. This new procedure is shown to be more accurate in predicting actual stress relaxation results under conditions of changing applied elastic strain.
Evaluation of Slow Strain-Rate Stress Corrosion Tests Results
Authors: Payer JH , Berry WE , Boyd WK
Published: March 2009

Slow strain-rate technique provides a rapid and reliable method to determine stress corrosion cracking (SCC) susceptibility of metals and alloys for a broad range of applications. Procedures are discussed for using the technique to (a) determine if an alloy is susceptible to SCC, (b) express SCC severity quantitatively, (c) rank alloys with respect to SCC susceptibility, and (d) evaluate the consequences of SCC susceptibility. Metallography or fractography is essential to confirm the presence or absence of SCC. Once SCC is confirmed, a number of parameters are available to express SCC severity quantitatively. Slow strain-rate technique is a conservative measure in that alloys exhibiting SCC in the test can be acceptable in service if stresses are controlled; however, no SCC in the test indicates no SCC in service under the conditions tested.
Slow Strain-Rate Stress Corrosion Testing for Liquid Metal Fast Breeder Reactor Steam Generator Applications
Authors: Indig ME
Published: March 2009

A high-temperature slow strain-rate facility was developed to evaluate the stress corrosion resistance of alloys considered for the construction of liquid metal fast breeder reactor (LMFBR) steam generators. The primary concern was stress corrosion that might occur on the water side during steam generator operation in locally faulted caustic environments. Most of the studies were performed at 316°C in 5 or 10 percent sodium hydroxide (NaOH) solutions with 2¼Cr-1Mo steel and Incoloy-800.

With minor modification, the slow strain-rate test was converted to a straining electrode test. Experiments conducted by the straining electrode test permitted the study of stress corrosion behavior in the high temperature caustic solutions over a range of oxidizing potentials.

It was found that 2¼Cr-1Mo steel was extremely resistant to caustic cracking at 316°C in all metallurgical conditions tested by the slow strain-rate test and the straining electrode test. A few slow strain-rate tests performed at 232 °C in 5 to 10 percent NaOH resulted in intergranular and transgranular stress corrosion failures of 2¼Cr-1Mo steel.

Unlike 2¼Cr-1Mo, Incoloy-800 was susceptible to caustic cracking at 316°C. The susceptibility depended on the metallurgical condition and to some extent, the oxidizing potential. The cold-worked and Grade 1 conditions exhibited excellent resistance to caustic cracking in the slow strain-rate test. However, limited studies in the straining electrode test showed the Grade 1 condition could be readily cracked at anodic oxidizing potentials.
Validity of the Slow Straining Test Method in the Stress Corrosion Cracking Research Compared with Conventional Testing Techniques
Authors: Buhl H
Published: March 2009

The appearance of a minimum in the susceptibility to stress corrosion cracking (SCC)/strain-rate curves obtained by slow strain-rate experiments has been examined carefully and a relationship between the repassivation rate of the material under investigation and the position of this minimum has been established.

For aluminum alloys, the results of the slow strain-rate experiments are not in complete agreement with the results of the conventional testing techniques. To explain this behavior, further experiments have to be carried out. At this moment, it seems to be doubtful whether the slow strain-rate testing technique is applicable to aluminum alloys.

The results with titanium alloys and high alloyed chromium- and chromium-nickel stainless steels obtained with different testing techniques (slow strain rate and constant load) are in very good agreement with each other.
Some Comparisons of the Slow Strain-Rate Method with the Constant Strain and the Constant Load Methods of Stress Corrosion Testing
Authors: Andrew JF , Heron JT , Stringer J
Published: March 2009

Two practical stress corrosion investigations are outlined in which the results of slow strain-rate tests are compared with the results of other test methods.

The possibility of formulating a specification to cover the slow strain-rate stress corrosion test method is considered.
Portable Slow Strain-Rate Stress Corrosion Test Device
Authors: Hauser F , Abbott SR , Cornet I , Treseder RS
Published: March 2009

A portable test device has been constructed for determining the stress corrosion cracking (SCC) characteristics of process environments. The device may be inserted and retrieved from laboratory, plant, and field equipment operating at pressures up to 13.8 MPa (2000 psi) and temperatures not exceeding 204°C (400°F) without shutting down the system. Specimens are loaded by the slow strain-rate method which has the advantage of producing SCC in a short period of time. The device is small enough to be inserted through a 2.54 cm (1 in.) diameter valve. A hydraulic cylinder, which requires a compressed gas supply as a power source, loads the specimens.

Initial testing was performed using low carbon steel specimens in air at room temperature. The hydraulic method of specimen loading performed smoothly and allowed constant strain rates as low as 4 × 10-7s-1-1 to be maintained ± 5 percent at a hydraulic system pressure of 2.76 MPa (400 psi).

Tests with AISI Type 304 stainless steel specimens in boiling (45 weight percent) magnesium chloride at 155°C (311°F) confirmed the applicability of the device for SCC studies. Indicators used include time to fracture, ultimate tensile strength, percent elongation, and visual observations for secondary cracks.
A Bursting Tube, Slow Strain-Rate Stress Corrosion Test
Authors: Poulson B
Published: March 2009

The construction of a facility to perform slow strain-rate stress corrosion tests by slowly increasing the pressure in a tubular specimen is described. Advantages of this bursting tube stress corrosion test are outlined and preliminary results reported.