bluuebunny/crossref_metadata_2025 huggingface dataset:
M-ROCLE Diesel and Biodiesel Fuel Lubricity Bench Test
Authors: Munson JW , Hertz PB
Published: April 2008

Environmental concerns have prompted sulfur reductions in diesel fuels. These changes can decrease unadditized fuel lubricity, resulting in higher wear of diesel injection pumps and engines. Actual diesel pump and engine tests are costly, and existing diesel fuel lubricity bench tests appear to be failing to evaluate the fuel lubricity adequately. This has prompted the described development steps for the M-ROCLE bench test. It employs a crossed roller on cylinder geometry and computer data acquisition systems. The measured wear scar area stress is divided by the theoretical elastic Hertzian contact stress, and friction coefficient, to yield a dimensionless Lubricity Number (LN) indicating the lubricating property of the test fuel. Based on previous work and from correlation with HFRR test data, an LN > 1.0 was established as the pass value for a diesel fuel of sufficient lubricity. The overall coefficient of variation in published Lubricity Numbers, based on six individual test runs for some hundred fuels surveyed to date, was 5.3%. This is indicative of high precision in the M-ROCLE method.
Effects of Friction Modifiers on Wear Mechanism of Some Steels Under Boundary Lubrication Conditions
Authors: So H , Hu CC
Published: April 2008

The effects of some commercial friction modifiers on antiwear performance of some steels were assessed experimentally under high contact pressures. The main compounds of the friction modifiers were, respectively, calcium carboxylate compound, organic molybdenum compound, phosphorous/sulfur (P/S) chemistry and polytetrafluoroethylene (PTFE). A ball-on-disk configuration was employed in the wear tests. The sliding speed of the disk on the stationary ball ranged from 0.785 m/s to 1.885 m/s and the applied load ranged from 39.2 N to 78.5 N. Bearing steel, high-carbon steel and medium-carbon steel were used to make the members of sliding pairs. The results show that only the additives that can produce chemical films on rubbing surfaces can reduce friction more effectively. Except PTFE, the other three additives have such an effect, but not as significant as claimed. Among these, P/S chemistry is the best, but this additive can cause excessive wear on rubbing surfaces in long-time use. Mo compound can provide a significant effect of antiwear on all three types of steel subjected to high contact pressures, while Ca compound has an antiwear effect only at comparably low pressures. Both Ca and Mo compounds cause wear on rubbing surfaces in a form of parallel deep grooves. PTFE neither improves antiwear performance, nor reduces friction on the rubbing surfaces of steel.
Aircraft Hydraulic Pump Tests with Advanced Fire-Resistant Hydraulic Fluids
Authors: Sharma SK , Snyder CE , Gschwender LJ
Published: April 2008

During the development of the fire-resistant hydraulic fluids for DoD (Department of Defense) aircraft, candidate fluids were formulated and then characterized initially by various laboratory bench tests. Endurance pump tests were then conducted on the candidate fluids to validate their performance. Pump tests under accelerated conditions were conducted on three candidate fire-resistant hydraulic fluids and several candidate nonflammable hydraulic fluids, using pressure-compensated axial flow piston pumps and an instrumented, small-volume, closed-loop hydraulic test stand. Case-drain temperature and signal-noise on the pump outlet pressure and the case-drain flow provided better failure indicators than the case-drain flow. The fluids containing viscosity-index-improvers underwent large viscosity losses. No viscosity loss was observed for the fluids that did not contain the viscosity-index-improvers. Lower viscosity fluids performed as well as the higher viscosity fluids in these pump tests. However, the ball-bearing material and the heat treatment had a bigger impact on pump life. Use of an M-50 bearing in place of the AISI-52100 bearing doubled the pump life.

Based upon the laboratory screening tests and the validation pump tests, the best performing fire-resistant hydraulic fluid was recommended for use in the DoD aircraft. Performance of the recommended fluid was further demonstrated in successful aircraft flight tests. Only limited hydraulic system simulator and aircraft subsystem testing has been conducted on the best-performing nonflammable hydraulic fluid candidate to date, but the performance was acceptable.
Influence of Test Parameters on Tribological Results — Synthesis from Round Robin Tests
Authors: Woydt M
Published: April 2008

A series of cooperative interlaboratory tests (round robins) was conducted in 1997, 1998 and 1999 by the DIN 51834 Working Group on Tribological Tests in Translatory Oscillation Apparatus. The statistical analysis of these test results shows the influence of cleaning solvent, machine model and evaluation criteria on the tribological properties of the lubricants tested. Coefficients of friction and wear results are ranked according to the effects of ten different cleaning solvents, where isopropanol gave the lowest values and isoparaffin solvents the highest. The effect of machine model on coefficients of friction varied from about 0.2 % to 0.9 % of the average. Wear results were not affected. The tests also showed that the seizure criteria and methods of measuring wear required for in the test procedure do not provide a suitable measure of the tribological properties of some lubricants.
Investigation of Frictional Properties of Lubricants at Transient EHD-Conditions
Authors: Åhrström B-O
Published: April 2008

In assessment of lubricant properties and in various contact applications, it is of importance to know the frictional qualities. Under quasi-static conditions, normal and transverse forces are measured using force transducers, but the task is more difficult when loads are high and transient as they often are in elastohydrodynamic conjunctions. The experimental method presented in this paper is based on analysis of propagating waves in a beam, due to an impact on its end surface, using FFT analysis. Since the impact is oblique, both non-dispersive compression waves and dispersive flexural waves are generated. The normal force originating from the axial wave is measured using strain gauges, while the transverse force is derived from the FFT's of two lateral acceleration histories using Timoshenko dynamic beam theory. The relation between normal and tangential force histories displays the frictional properties at the impact as a function of time; i.e., variations in frictional properties during loading and unloading (typically 200– 400 μs in ball bearings and gears) can be observed. A variety of lubricants has been studied up to a Hertzian pressure of 2.5 GPa, and the method and results are presented.
A Mechanistically-Based Model of Irradiation Damage in Low Alloy Steel Submerged Arc Welds
Authors: Williams TJ , Ellis D
Published: April 2008

A model of irradiation damage in low alloy steel submerged arc welds has been developed by fitting test reactor data to physically reasonable mathematical equations. The model is underpinned by a substantial amount of microstructural data obtained using small angle neutron scattering, atom probe microscopy and other techniques. These data have been used qualitatively to show that the basic assumptions of the model are reasonable, and assessed quantitatively using the Russell and Brown modulus hardening model.

The model predicts hardness change in welds irradiated at high neutron dose rates as a function of irradiation dose, irradiation temperature and chemical composition. Correlations have been developed to enable Charpy or fracture toughness shift to be predicted from hardness change. In addition, a simple modification to the basic model allows estimation of damage at power reactor dose rates. This has enabled comparison with US surveillance programme data. Possible reasons for the observed differences in data and predictions are discussed. Plans to validate the model by testing material from a decommissioned RPV are outlined.
Vessel Investigation Program of “CHOOZ A” PWR Reactor after Shutdown
Authors: Brillaud C , Grandjean Y , Saillet S
Published: April 2008

In October 1991 the CHOOZ A PWR plant, operated by the French and Belgian company SENA, was shut down after 24 years. It was the first PWR shutdown in France. According to the EDF life duration project it was decided to perform an examination program on samples taken from the wall of the vessel in order to complete the feedback.

The results obtained show the following: • The embrittlement measured by the pressure vessel surveillance program is representative of that of the Shell determined at different axial and angular locations for the 1/4 of the internal thickness. This observation is consistent with the relative homogeneity of the embrittling elements (Cu, P, Ni) throughout the entire Shell, • The mechanical properties evolution through the wall thickness of the Shell measured after irradiation is interpreted in relation with fluence variation and unirradiated mechanical properties profile through the thickness, • The comparison of direct toughness measurement with the French code RCCM evaluation confirms the safety nature of the conventional approach. For the weld, after an irradiation damage of 2 1019 n.cm-2 (E>1MeV), a margin of the order of the irradiation effect seems to exist.
Development of Reconstitution Technology for Surveillance Specimens in Japan Power Engineering and Inspection Corporation
Authors: Kataoka S , Kato N , Taguchi K , Yamamoto M , Oka Y
Published: April 2008

In order to establish reconstitution technology for the surveillance specimens of RPV steels, a project was started in 1996FY. We focus on a correlation between the reduction of absorbed energy and the interaction of heat affected zone (HAZ) and plastic zone, to establish applicable reconstitution conditions for Charpy specimens. The plastic zone width was estimated from the hardness distribution of the Charpy specimens, and then the correlation between the plastic zone width and absorbed energy was obtained. Within the limits of 100J, there was no reduction of absorbed energy for the Charpy specimens reconstituted with 10 mm insert length using surface a ctivated joining method (SAJ). By comparing the length of insert material with the sum of HAZ width and plastic zone width, it is clear that the interaction causes the reduction of absorbed energy. The applicable conditions of reconstituted Charpy specimens could be assessed by comparing the insert length with HAZ width + plastic zone width.
Master Curve Characterization of Irradiation Embrittlement Using Standard and 1/3-Sized Precracked Charpy Specimens
Authors: Lee B-S , Yang W-J , Huh M-Y , Chi S-H , Hong J-H
Published: April 2008

Cleavage initiation fracture toughness (KJC) tests have been performed in the transition temperature ranges of five different heats of reactor pressure vessel steels. The main purpose of this study is to investigate the applicability of the ASTM Standard Test Method for Determination of Reference Temperature, To, for Ferritic Steels in the Transition Range (E1921-97) to small specimens available in normal surveillance capsules. Precracked Charpy-type specimens with the standard size (10×10×55mm, PCVN) and 1/3-size (3.3×3.3×18.3mm, 1/3-PCVN) are mainly investigated. Results from more than 300 fracture toughness test data are presented including 120 unirradiated PCVN specimens and 100 unirradiated 1/3-PCVN specimens in addition to some CT specimen data and two sets of irradiated PCVN data. The test materials are the IAEA reference steels, so-called JRQ and JFL, and three Korean SA508-3 forging steels that were made by different refining processes. JRQ and a Korean steel, SKA-1, are also evaluated after neutron irradiation by PCVN specimens as well as Charpy impact tests. Fracture toughness data showed that the master curve and its probabilistic bound lines represent the population of the test data measured from different materials and specimens with good accuracy. However, there are still the effects of specimen geometry and size on the measured To values. These effects seem to be more significant in microscopically less homogeneous materials. Smaller bend type specimens may give slightly less conservative results than the larger CT type specimens. One of the important findings is that ultra small 1/3-PCVN specimens are also valuable as the standard size PCVN specimens for determining reference temperatures since the differences are rather systematic and predictable. The T28J correlation, based on the PCVN data only, works well for the current data sets including irradiated materials.
An Evaluation of Through-Thickness Changes in Primary Damage Production in Commercial Reactor Pressure Vessels
Authors: Stoller RE , Greenwood LR
Published: April 2008

An extensive database of atomic displacement cascades in iron has been developed using the method of molecular dynamics (MD). More than 300 simulations have been completed at 100K with energies between 0.1 and 100 keV. This encompasses nearly all energies relevant to fission reactor irradiation environments since a 100 keV MD cascade corresponds to the average iron cascade following a collision with a 5.1 MeV neutron. Extensive statistical analysis of the database has determined representative average values for several primary damage parameters: the total number of surviving point defects, the fraction of the surviving point defects contained in clusters formed during cascade cooling, and a measure of the size distribution of the in-cascade point defect clusters. The cascade energy dependence of the MD-based primary damage parameters has been used to obtain spectrum-averaged defect production cross sections for typical fission reactor neutron energy spectra as a function of depth through the reactor pressure vessel. The attenuation of the spectrum-averaged cross sections for total point defect survival and the fraction of either interstitials or vacancies in clusters are quite similar to that for the NRT dpa. However, the cross sections derived to account for the energy dependence of the point defect cluster size distributions exhibit a potentially significant variation through the vessel. The production rate of large interstitial clusters decreases more rapidly than dpa whereas the production of large vacancy clusters is slower than dpa.
Hardness and Microstructure Changes with Thermal Annealing of Neutron-Irradiated Fe-Cu Alloys
Authors: Kawanishi H , Suzuki S
Published: April 2008

In order to investigate mechanisms in recovery of irradiation-induced hardness by thermal annealing for pressure vessel steels containing copper, Fe-0.6 wt.% Cu model alloys irradiated to a dose of 0.0055 dpa at 290°C in JMTR were isochronally annealed at temperatures ranging from 250 to 600°C (ΔT = 50°C, Δt =15 min). Vickers hardness measurements showed that 70% of the irradiation-induced hardness was eliminated by the annealing. TEM examinations revealed that three kinds of precipitates were formed in the specimens; those are small copper precipitates (disk-shaped, 3–8 nm in diameter), ordered structures of possibly Cu3Fe (L12-type, a0 = ~0.343 nm) and Fe3O4 particles (structure of spinel-type). Copper precipitates slightly increased the number density and size with the post-irradiation annealing below 400 °C, indicating clearly that copper precipitates contributed to hardening, though the degree may be small. The ordered structure was proven by the occurrence of superlattice reflections in selected area diffraction patterns. The post-irradiation annealing reduced the intensities of the superlattice reflections and the zone of Cu3Fe-structure. The ordered structure of Cu3Fe was observed to be destroyed by thermal annealing, resulting in a remarkable decrease in hardness. The hardness during thermal annealing was concluded to be governed by two competitive processes of hardening by the growth of copper precipitates and softening by the order-disorder transformation of Cu3Fe.
Effects of Neutron Irradiation and Thermal Annealing on Model Alloys Using Positron Annihilation Techniques
Authors: Cumblidge ES , Catchen GL , Motta AT , Brauer G , Böhmert J
Published: April 2008

We present the results of a systematic investigation of neutron-irradiated and thermally annealed Fe-Cu-Ni-P model alloys using positron annihilation spectroscopy (PAS), including lifetime and Doppler broadening techniques, and Rockwell hardness. These alloys were examined in the as-fabricated state, after irradiation at 270° C to 1 × 1019 n.cm-2, and to 8 × 1019 n.cm-2, and after successive post-irradiation isochronal anneals at temperatures from 200 to 600° C. The results can be qualitatively explained by invoking an irradiation-induced microstructure consisting of a combination of small dislocation-type defects or defect clusters (matrix damage) and dense precipitation of fine scale irradiation-induced precipitates. The matrix damage anneals between 350° C and 450° C. The irradiation-induced precipitates also evolve with annealing, but at higher temperatures. The combined effect of high Cu and high Ni concentrations leads to more extensive irradiation-induced precipitation than in cases where either element is missing, whereas the effect of P is less pronounced. We analyze and compare the results with similar measurements performed on irradiated pressure-vessel steels and with other positron measurements on model alloys, reported in the literature.
Relation Between Resistivity and Mechanical Properties in Heat Affected Zone of Welded Pressure Vessel Steel
Authors: Kasada R , Suzuki T , Itoh K , Naruse Y , Kimura A
Published: April 2008

The relation between resistivity and mechanical properties, such as hardness and the ductile-brittle transition temperature (DBTT), in heat-affected zone (HAZ) of welded A533B pressure vessel steel (PVS) has been investigated by means of a small specimen test technique before and after neutron irradiation. A submerged arc welded thick plate of A533B for plant use was supplied by Japan Steel Works, Ltd. Neutron irradiation was performed in the Japanese Materials Test Reactor (JMTR) at 290°C up to 1.3 × 1024 n/m2. Resistivity measurements with a pair of potential probes, 1 mm distance apart, were performed on the surface of specimens at different locations across the fusion boundary. Before the irradiation, the resistivity of the weld was higher than that of the base metal and the resistivity in the HAZ gradually reduced with increasing distance from the fusion boundary. After the neutron irradiation, the resistivities at all the locations were reduced. Post-irradiation annealing experiments revealed that resistivities of base metal and HAZ almost recovered after annealing to 500°C, while only a part of the recovery was observed for the resistivity of the weld. On the contrary, the recovery of irradiation hardening was faster in the weld than in the base metal. It is considered that the reduction of resistivity is due to precipitation of solute elements, such as manganese, nickel and copper. The correlation between resistivity change and irradiation hardening is also discussed.
Composition Effects on the Radiation Embrittlement of Iron Alloys
Authors: Böhmert J , Ulbricht A , Kryukov A , Nikolaev Y , Erak D
Published: April 2008

The effects of copper, phosphorus and nickel on radiation embrittlement were investigated using an irradiation experiment at surveillance positions in two Russian VVER-type reactors with 8 iron-base testing alloys. Chemical composition varied between 0.015 to 0.42 % Cu, 0.002 to 0.039 % P, 0.01 to 1.98 % Ni, 0.09 to 0.37 % Si, and 0.35 to 0.49 % Mn. Charpy-V impact tests and tensile tests were performed with specimens machined from these alloys. The specimen were tested in the as-received state, in the irradiated state (fluence: 1×1019 and 8×1019 cm-2 [En > 0.5 MeV]) and in the post-irradiation annealed state.

Irradiation produces significant hardening and embrittlement. The effect increases with the Cu and P content. Ni causes an additional embrittlement. It does not depend on the Ni content within the range of 1.1 to 2 % Ni. The irradiation effect can be eliminated by annealing at 475 °C / 100 h but not absolutely in the case of high Cu or P content.

Small angle neutron scattering experiments of these alloys show that not only the volume fraction but also the type of the radiation defects vary in dependence on the composition of the alloys.
The Determination of Bias Factor Stress Dependence from Experimental Data on Irradiation Creep and Stress-Affected Swelling in Austenitic Stainless Steels
Authors: Konobeev YV , Pechenkin VA , Garner FA
Published: April 2008

The measured irradiation creep strain ε in structural materials is usually fitted with the equation: E/σ B0dpa+DS, where σ is the applied stress, S the void swelling, and B0 and D are the material parameters. The stress dependence of swelling is sometimes described using the equation S = S0(l+Mσhyd), where S0 is the stress-free swelling and σhyd is the hydrostatic stress component. On the basis of the SIPA mechanism of irradiation creep it is shown in this paper that the parameter D depends on stress as follows: D = D(1+Mσhyd), where D0 is a constant and the parameter B0 depends on dose. Knowing the constant M, one can determine the constant D0 from experimental data on dose dependence of creep tube diametral strain at several hoop stress levels. This permits the determination of the stress dependence of the bias factor. Such a determination was made in this paper for the austenitic stainless steel 316, for which a complete set of data became available recently. One of the important results of the present paper is the conclusion that to a reasonable approximation the irradiation creep rate εic can be determined from data on the stress-free swelling rate and stress-affected swelling.
Radiation-Induced Segregation and Void Swelling in 304 Stainless Steel
Authors: Allen TR , Cole JI , Kenik EA
Published: April 2008

Void swelling and radiation-induced segregation have been measured in 304 stainless steel. Samples were irradiated in the outer regions of the EBR-II reactor where displacement rates of 2.0×10-8 and 6.6 ×10-8 dpa/s are comparable to those in pressurized water reactor components. Samples were irradiated at temperatures from 371-390°C to total doses of up to 20 dpa. Void swelling reached a maximum of 2 % at 20 dpa. Nickel enrichment and chromium depletion to of 20 at% and 12 at% respectively were measured. Both void swelling and radiation-induced segregation were dependent on dose rate, increasing as the dose rate decreased. Grain boundary compositions were measured both near and in areas free of precipitates. The presence of a precipitate significantly changes the grain boundary compositions near the precipitate.
Irradiation Creep Deformation of Modified 316 and 15Cr-20Ni Base Austenitic Fuel Elements Irradiated in FFTF
Authors: Uehira A , Ukai S , Mizuta S , Puigh RJ
Published: April 2008

Irradiation creep of modified 316 (PNC316) and 15Cr-20Ni base austenitic stainless steels was determined using the diametral change of the fuel pins, which were irradiated under the fission gas pressurized condition in FFTF to a peak displacement damage of 107 dpa in PNC316 and 120 dpa in 15Cr-20Ni base. The creep compliance B0 and creep-swelling coupling coefficient D were found to be 1.1 to 3.0 × 10-6 MPa-1 dpa-1 and up to 1.3 × 10-2 MPa-1 for instantaneous volumetric swelling rate, respectively. Those are almost the same level as those derived using the pressurized tubes irradiated in FFTF-MOTA. D values tend to decrease and disappear with developing void swelling.
Post-Irradiation Deformation Microstructures in Fe-9Cr
Authors: Gelles DS , Hamilton ML , Schäublin R
Published: April 2008

The deformed microstructures of both irradiated and unirradiated Fe-9Cr uniaxial tensile specimens have been examined to identify controlling mechanisms. Deformation following irradiation is found to occur in poorly defined channels, causing formation of discrete steps at surfaces and delineated by nonuniformly distributed highly elongated voids. Deformation is by motion of a∕2<111> dislocations, which interact with and decompose irradiation-induced a<100> loops. The structure formed after extensive deformation consists of highly complex cell walls and moderate densities of individual slip dislocations.
Correlation Between Creep Properties and Microstructure of Reduced Activation Ferritic/Martensitic Steels
Authors: Sakasegawa H , Hirose T , Kohyama A , Katoh Y , Harada T , Hasegawa T
Published: April 2008

Reduced activation ferritic steels (RAFs), JLF-1 (9Cr-2W-V,Ta steel) had been studied as one of the reference materials in the IEA RAF R&D activity, because of its superior resistance to high-fluence neutron irradiation up to 100 dpa.

Recently, JLS-series (9Cr-xW-V,Ta steels; x=2.5, 3.0 and 3.5) have been produced as options for RAFs for use at higher temperatures in advanced blanket systems. In this series, improved high temperature mechanical properties were intended by increased tungsten contents.

The creep properties improved with the tungsten contents. A microstructural examination after creep rupture test revealed differences with a increase of tungsten content from 2.0 (JLF4) to 3.0 wt% (JLS-2). According to the examination of tested specimens (100 MPa, 700°C), more intragranular fine precipitates and more intergranular precipitates formed preferentially on prior austenite boundaries and martensite lath boundaries were found in JLS-2 than in JLF-1, martensite lath widths became narrower and dislocation density increased with the increase of tungsten content.

Such microstructural features are likely to improve the creep properties by inhibiting grain evolution, microstructural recovery and strengthening grain boundaries at elevated temperatures.
Comparison of Thermal Creep and Irradiation Creep of HT9 Pressurized Tubes at Test Temperatures from ∼490°C to 605°C
Authors: Toloczko MB , Grambau BR , Garner FA , Abe K
Published: April 2008

Pressurized creep tubes were used to evaluate the thermal creep behavior and the irradiation creep behavior of several variants of HT9 ferritic-martensitic steel in the temperature range from ∼490°C to 605°C. Examination of the thermal creep data as a function of time showed classic thermal behavior at all the test temperatures. A creep transient was followed by a period of steady state creep which, in some instances, was then followed by tertiary creep. The irradiation creep behavior also displayed a transient followed by steady state creep, but no tertiary creep was observed.

while the thermal creep behavior and the irradiation creep behavior were qualitatively similar, the magnitude of both the transient and the steady state creep rate were often different. At ∼490°C, the thermal creep specimens exhibited a greater transient strain, while at 600°C, the irradiation creep specimens exhibited a greater transient strain. For both the thermal creep specimens and the irradiation creep specimens, the transient strain was observed to increase with increasing applied stress. The steady state creep rates of both the thermal creep specimens and the irradiation creep specimens were observed to increase with increasing temperature. At lower stresses, the steady state creep rates of the thermal creep specimens and the irradiation creep specimens were often equal. At the higher test stresses, the steady state creep rate of the irradiation creep specimens was always higher.

At ∼490°C, the steady state thermal creep rate was observed to have a linear stress dependence up to the highest applied stress of 250 MPa. At 575°C, the stress exponent was between 1.5 and 2 for effective stresses less than 200 MPa. At 605°C, the stress exponent was ∼1 for effective stresses less than 70 MPa. For the irradiation creep specimens, a stress exponent between 1.5 and 2 was observed at ∼490°C and 550°C. At 600°C, the stress exponent was observed to be ∼1.
The Effect of High Energy Protons and Neutrons on the Tensile Properties of Materials Selected for the Target and Blanket Components in the Accelerator Production of Tritium Project
Authors: Maloy SA , James MR , Willcutt GJ , Sommer WF , Johnson WR , Louthan MR , Hamilton ML , Garner FA
Published: April 2008

The Accelerator Production of Tritium (APT) project proposes to use a 1.0 GeV, 100 mA proton beam to produce neutrons via spallation reactions in a tungsten target. The neutrons are multiplied and moderated in a lead/aluminum/water blanket and then captured in 3He to form tritium. The materials in the target and blanket region are exposed to protons and neutrons with energies into the GeV range. The effect of irradiation on the tensile properties of candidate APT materials, 316L and 304L stainless steel (annealed), modified (Mod) 9Cr-1Mo steel, and Alloy 718 (precipitation hardened), was measured on tensile specimens irradiated in the Los Alamos Neutron Science Center accelerator, which operates at an energy of 800 MeV and a current of 1 mA. The irradiation temperatures ranged from 50–164°C, prototypic of those expected in the APT target/blanket. The maximum achieved proton fluence was 4.5 × 1021 p/cm2 for the materials in the center of the beam. This maximum exposure translates to a dpa of 12 and the generation of 10,000 appm H and 1,000 appm He for the Type 304L stainless steel tensile specimens.

Specimens were tested at the irradiation temperature of 50-164°C. Less than 1 dpa of exposure reduced the uniform elongation of Alloy 718 (precipitation hardened) and mod 9Cr-lMo to less than 2%. Approximately 4 dpa of exposure was required to reduce the uniform elongation of the austenitic stainless steels (304L and 316L) to less than 2%. The yield stress of the austenitic steels increased to more than twice its non-irradiated value after less than 1 dpa. These results are discussed and compared with results of similar materials irradiated in fission reactor environments.
Dimensional Characteristics of Displacement Cascades in Austenitic Steels under Neutron Irradiation at Cryogenic Temperature
Authors: Kozlov AV , Portnykh IA , Skryabin LA , Lapin SS
Published: April 2008

Samples of 16Cr - 15 Ni - 3 Mo - 1Ti steel were irradiated to a fast neutron fluence of 1.5 ∙ 1018 cm-2 and 1.5 ∙ 1019 cm-2 (E>0.1 MeV) in the IVV - 2M reactor and investigated by transmission electron microscopy methods. Electron microscopy patterns were obtained. It was shown that the size distribution of clusters had a form close to a Gaussian after irradiation to a fluence of 1.5 ∙ 1018 n∙cm-2. There were several peaks in the distribution histogram of the sample irradiated to 1.5∙1019 n∙cm-2.

The formation of the low temperature irradiation clusters in austenitic steel was analyzed with a model of displacement cascades overlapping under cryogenic neutron irradiation. All the clusters formed were differentiated into two groups: low-temperature radiation clusters formed by not overlapped displacement cascades (LTRC - 1) and radiation clusters formed by overlapped cascade regions (LTRC - 2). Analytical expressions were obtained to describe the relationships of the average dimensions of LTRC of both groups and the dynamics of cluster accumulation.
Effect of Final Irradiation Temperature and Frequency of Irradiation Temperature Cycles on Microstructural Evolution of Vanadium Alloys
Authors: Nita N , Fukumoto K , Matsui H
Published: April 2008

Effects of varying temperature on microstructure of materials under irradiation can be very complicated. In this paper, evolution of microstructure in vanadium alloys during temperature changes is closely examined with emphasis on the effect of frequency of the temperature changes and the final temperature.

Pure vanadium, V-5Cr and V-5Nb were prepared. Neutron irradiation was conducted in JMTR at constant temperatures of 200°C, 400°C and under cyclic temperature changes of 200/400°C. The numbers of temperature cycles were 0.5, 5.5 and 6 cycles. TEM observations, Positron Annihilation Spectroscopy and micro-Vickers hardness test were performed.

By comparison between 0.5 and 5.5 temperature cycle, coarser microstructures are observed in 5.5 cycles. Frequent temperature change is considered to have restricted the defect growth. By comparison between 5.5 and 6 temperature cycle irradiation, which is focused on the effect of the final temperature, coarser microstructures are observed in 6 cycle irradiation.
Hardening of Vanadium Doped with Nitrogen by Heavy Ion Irradiation and Post-Irradiation Annealing
Authors: Nagasaka T , Takahashi H , Muroga T , Yoshida N , Tanabe T
Published: April 2008

Copper ion irradiation at room temperature and at 573 K up to 1 dpa was conducted on vanadium doped with controlled levels of nitrogen ranging from 12 to 770 weight ppm (wppm). Micro-indentation test was performed to make a quantitative estimation of hardening of the irradiated surface layer. Microhardness of the unirradiated and as-irradiated vanadium increased with increasing nitrogen content. They showed linear relationship when nitrogen was singly varied. Irradiation hardening was independent of nitrogen content and of irradiation temperatures. This fact agrees with microstructure observations. After post-irradiation annealing at 573 K, radiation anneal hardening (RAH) was observed at the nitrogen contents of 170 wppm and above. In comparison with the previous anneal hardening experiments with cold-worked specimens, stepwise increase in the anneal hardening with nitrogen content at about 100 wppm was commonly derived for cold-worked and irradiated vanadium.
The Influence of Temperature, Fluence, Dose Rate, and Helium Production on Defect Accumulation and Swelling in Silicon Carbide
Authors: Kishimoto H , Katoh Y , Kohyama A , Ando M
Published: April 2008

Swelling and microstructure of silicon carbide (SiC) are studied by means of MeV-range ion irradiation. The material used is chemical vapor deposited high purity polycrystalline cubic (3C)-SiC. The swelling behavior is characterized by precision interferometric profilometry following ion bombardment to the diamond-finished surface over a molybdenum micro-mesh. Irradiation was carried out at temperatures up to 873 K, followed by profilometry at room temperature. Microstructural characterization by means of cross-sectional transmission electron microscopy has also been finished for selected materials. Irradiation induced swelling was increased with increasing the displacement damage level up to 0.3 dpa at all evaluated temperatures. At 333 K, the swelling was increased with increasing the damage level up to 1 dpa, and irradiation-induced amorphization was observed over 1.07 dpa. At the higher irradiation temperature, swelling was saturated over 0.3 dpa. The temperature dependence of saturated swelling obtained so far appeared very close to the neutron irradiation data. For the study of the synergism of displacement damage and helium production, a dual-beam experiment was performed up to 100 dpa at 873 K. Swelling of the dual-beam irradiated specimen was larger than that of single-beam irradiated specimen. The result also suggested the onset of unsteady swelling in high He/dpa conditions after “saturated point defect swelling” is once achieved at displacement damage levels over 50 dpa.
Microstructural Stability of SiC/SiC Composites under Dual-Beam Ion Irradiation
Authors: Katoh Y , Kishimoto H , Ando M , Kohyama A , Shibayama T , Takahashi H
Published: April 2008

Microstructural evolution of silicon carbide fiber-reinforced silicon carbide matrix composites (SiC/SiC composites) during dual-beam ion irradiation was studied. The composites had been fabricated by means of chemical vapor infiltration (CVI) and polymer impregnation and pyrolysis (PIP) methods using advanced fibers, i.e., Hi-NicalonTM Type-S and TyrannoTM-SA, as well as conventional fibers. Dual-beam ion irradiation was performed to 10 dpa at 873K and 60appmHe/dpa. Composites with advanced low-oxygen near-stoichiometric SiC fiber with high crystallinity and beta-SiC matrix exhibited superior irradiation resistance, in contrast to that amorphous Si-C-O based fibers and conventional polymer-derived matrix exhibited microstructural instability in association with irradiation-induced crystallization. Pyrolytic carbon deposited as the fiber-matrix (F-M) interphase exhibited irradiation-induced amorphization and the helium co-implantation enhanced it. Post-irradiation heat treatment caused significant microstructural changes across the F-M interphases at temperatures as low as the composites are supposed to retain their mechanical strength.
Effect of Mass and Energy on Preferential Amorphization in Polycrystalline Silicon Film during Ion Irradiation
Authors: Takeda M , Ohnuki S , Suda T , Watanebe S , Abe H , Nashiyama I
Published: April 2008

In-situ transmission electron microscopy was applied for clarifying radiation-induced amorphization, the behavior of grain boundaries under ion irradiation. The effect of mass and energy of several ions on preferential amorphization was discussed. The critical fluence for amorphization strongly depended on the temperature, where it increased with increasing temperature. Further, with increasing ion mass and decreasing energy, the critical fluence was reduced. The onset temperature for preferential amorphization increased in the case of heavier mass and lower energy ion irradiation. All of the results imply the importance of the balance between damage production and recovery.
Crack Growth Resistance of Irradiated Zr-2.5Nb Pressure Tube Material at Low Hydrogen Levels
Authors: Davies PH , Himbeault DD , Shewfelt RSW , Hosbons RR
Published: April 2008

The primary factors influencing the crack growth resistance of irradiated Zr-2.5Nb pressure tube material at low concentrations of hydrogen/deuterium are reviewed. These factors include the initial characteristics of the material, which have brought about improvements in the toughness, and the operating conditions in reactor. The paper presents an update on the current status of this work using J-R curves. Such curves are determined from curved compact and rising-pressure burst test specimens at 250°C, i.e., the lower end of the operating temperature range. Some of the challenges encountered in assessing the crack growth toughness of this high-strength, thin-walled material are discussed. The role of chlorine, known to be responsible for the presence of Zr-Cl-C particles and preferential decohesion and fissuring, is also highlighted. The results from the curved compact specimens suggest a limiting level of chlorine above which no further significant degradation in crack growth resistance occurs. This level of chlorine is about 3 wt ppm for material having a low concentration of zirconium phosphide (P < 20 wt ppm). Such results require confirmation using burst tests on material with intermediate levels of chlorine and low levels of zirconium phosphide.
Study of Profile Measurements Using Six Different Devices
Authors: Chiu C-T , Lee M-G , Chen D-H
Published: April 2008

One of the top priorities for transportation authorities is to build a smooth pavement. A smoother pavement provides a better ride and reduces damage from dynamic traffic loading. Many different profilers have been selected by various transportation agencies to measure roughness. Roughness has been used in many specifications to determine if the contractor should obtain a bonus or penalty. Thus, a reliable device is needed to collect repeatable and defendable roughness values. The purpose of this study is to review, evaluate, and analyze six existing devices. Repetitive tests were conducted on both flexible and rigid pavements to determine the repeatability, correlation and limitations of these devices. Excellent correlations among devices have been developed with high R2. The 0.1 in. (2.54mm) blanking band yielded approximately 20% higher profile indexes than the 0.2 in. (5.08mm) band, and was more sensitive to roughness. The ARRB walking profiler yielded the highest precision, and is easy to operate and transport. Thus, the ARRB walking profiler was recommended for use on newly constructed pavement. The ARRB multiple laser profiler can be used for collecting profiles on existing pavements for management purposes.
Effect of Temperature Differentials on Density and Smoothness
Authors: Gardiner MS , Wagner CT , Hodgson DT , Sain J
Published: April 2008

A Roadware ARAN inertial profiler was used to calculate the International Roughness Index (IRI) for the Auburn University National Center for Asphalt Technology (NCAT) test track tangent sections as well as three paving projects in Michigan. IRI values were calculated for short intervals [4.6 to 7.6 meters (15 to 25 feet)] rather than for the traditional 160 meters (0.1 mile). These short intervals were able to identify easily localized anomalies in the pavement smoothness due to changes in the construction activities. They were also useful in evaluating relationships between IRI and mix variables in the short NCAT test track test sections [60 meters (200 feet)].

IRI repeatability (standard deviation for three replicates) immediately after onstruction was found to be 0.063 m/km (3.99 inches/mile) in the right wheel path for mixes at the test track. The left wheel path tended to have higher and more variable IRI values. This was attributed to the left laser path being close to potentially segregated mix at the edges of the screed extension. The IRI variability increased with traffic. Using this nitial estimate of variability, some statistically significant differences due to mix variables such as aggregate source and/or binder grade can be seen.

Results from the test track indicate that the finer mixes tended to have IRI values that ncrease slightly as density increases. This suggests that working the fine mixes to obtain higher densities results in a higher initial roughness.This observation was also generally seen in the data from the Michigan field projects. IRI values decreased significantly within 6 months of trafficking for the majority of the mixes at the test track. This suggests that traffic can have a smoothing affect on the pavement for up to 6 months after the start of trafficking.

All results from this research were based on the construction of test track sections. These results should be verified on actual paving projects.
Characterizing Pavement Profile Using Wavelets Analysis
Authors: Attoh-Okine NO , Mensah S
Published: April 2008

Pavement smoothness can be described by the magnitude of the profile measurements and their distribution over measurement intervals. Surface smoothness, especially on newly constructed pavements, is a major concern for the highway industry. The smoothness is a measure of the quality of the constructed pavements. Measured data from profilographs are inherently multiscale in nature owing to different contributions from events occurring at different locations and with different localization frequency. Therefore, a data analysis method that can represent the measured data at multiple scale is better suited for extracting information and making inferences. This paper presents a mathematical tool, a wavelets analysis, that has the potential to extract information atdifferent scales. The multiscale property and structure of the wavelet algorithm can lead to a method of analysis and display that highlights changes in the profile measurements.
Transition Toughness Modeling of Steels Since RKR
Authors: Kirk MT , Natishan ME , Wagenhofer M
Published: April 2008

In this paper we trace the development of transition fracture toughness models from the landmark paper of Ritchie, Knott, and Rice in 1973 up through the current day. While such models have become considerably more sophisticated since 1973, none have achieved the goal of blindly predicting fracture toughness data. In this paper we suggest one possible way to obtain such a predictive model.
Constraint Correction of Fracture Toughness CTOD for Fracture Performance Evaluation of Structural Components
Authors: Minami F , Arimochi K
Published: April 2008

A correction of CTOD for constraint loss in large-scale yielding conditions is made on the basis of the Weibull stress fracture criterion, that eliminates an excessive conservatism in the conventional fracture assessment and material fracture toughness requirement. A CTOD ratio β = δ3P/ δWP (< 1) is proposed, where δWP is the CTOD of a wide plate component and δ3Pis an equivalent CTOD of the fracture toughness specimen at which the toughness specimen gives a compatible Weibull stress with the wide plate. The CTOD ratio β is decreased to a large extent after full yielding of the wide plate component, which is more significant for a high yield ratio YR and a deep surface crack in the wide plate. The Weibull modulus m exerts a marginal influence on β. A case study is presented on the application of the CTOD ratio β to the fracture performance assessment of full-scale column-to-beam connections subjected to cyclic and dynamic loading.
A Physics-Based Predictive Model for Fracture Toughness Behavior
Authors: Natishan ME , Wagenhofer M , Rosinski ST
Published: April 2008

Using the Zerilli-Armstrong (ZA) constitutive model for BCC materials and a combined strength-strain model of fracture, a physics model suitable for predicting the fracture toughness transition behavior of ferritic steels has been developed. The model predicts an exponential dependence of the plastic work on temperature and thus is comparable to the exponential dependence of plastic work predicted by Wallin et al. for the Master Curve. Exploring the limits of applicability of the ZA equation used as the basis for this model provides the information required to firmly establish the limits of material condition applicability of the Master Curve. Calculations based on limited data provide validation of the proposed model. The models ability to predict shifts in transition temperature with irradiation and its application to RP vessel integrity assessment will also be discussed.
Sensitivity in Creep Crack Growth Predictions of Components due to Variability in Deriving the Fracture Mechanics Parameter C*
Authors: Nikbin KM
Published: April 2008

In this paper the uncertainties in estimating C* creep fracture mechanics parameter, on component defect assessment, is considered. Comparisons of reference stress σref and the stress intensity factor K for a surface cracked plate under tension and bending and a pipe geometry under internal pressure and external bending using formulae from available codes of practices such as the R5/R6 [1–2], BS7901 [3] and A16 [4] are made with three-dimensional Finite Element (3D FE) analysis calculations. It is shown, using the same material properties and specimen dimensions, that the uncertainty associated with calculating σref could be as much as ±40% whereas for the stress intensity K it is about ±10%. The σref values are used to calculate C* using the mean properties of a base 316LN type stainless steel plate tested at 650 °C and a cross-weld P22 circumferentially welded pipe tested at 565 °C. Both the pipe and the plate were tested within a European collaborative programme ‘HIDA’ between (1996–2000) [5]. The tendency is that ‘global’ limit load analysis will give a lower and more conservative C* than the ‘local’ analysis. From the comparisons of the pipe and plate initial cracking rates, using different C* estimations, with standard creep crack growth rate data on compact tensions (CT) specimens, using the ASTM E1457-2002 to evaluate C*, it is shown that predictions of cracking rates could vary by as much as two decades in magnitude. This inconsistency yields itself to an analysis based on an empirical model for predicting crack growth in components.