bluuebunny/crossref_metadata_2025 huggingface dataset:
Assessment of the Tribological Function of Lubricants for Sheet Metal Forming
Authors: Filzek J , Groche P
Published: April 2008

Tribology plays a significant role in enlarging the process limits and ensuring process stability as well as good quality of the forming parts in deep drawing. This paper focuses on assessing lubricant behavior and its influence on tribological conditions during the forming process. A basic condition for efficient usage of the potentials offered by lubrication is the availability of test methods allowing fast and safe evaluation of products. Two specific test stands for sheet metal processing are presented in this paper. These test stands are based on the strip drawing principle. Using these model tests, the capability of a lubricant can be tested under all relevant conditions and its suitability for certain applications can be determined. The experimental results of several tested lubricants will be shown. Subsequently, the results are verified with deep drawing tests of real forming parts.
Determination of Gear and Bearing Material Scuffing Limits Using High-Speed Disk Machines
Authors: Snidle RW , Evans HP , Alanou MP
Published: April 2008

The paper describes the design of disk machines which are used to simulate the contact and scuffing conditions in high-speed aerospace gears and rolling contact bearings. In ground gears the surface finish of the teeth is predominantly in the direction perpendicular to that in which rolling and sliding takes place, and in order to reproduce this configuration in disk tests it is necessary to axially grind the specimens. This has been achieved using a novel grinding/generating process which also gives a self-aligning crowned geometry, thus avoiding spurious edge effects. In the case of rolling element bearings, surface finish is generally of a much higher quality with finish predominantly in the rolling direction. The disk machine developed for simulation of this type of contact therefore uses honed/polished surfaces. Results obtained from the disk machines are shown corresponding to typical high-speed/high-temperature conditions found in aerospace practice.
Identification of Boundary Friction Coefficient Under Mixed Lubrication in Block-on-Ring Friction Tester with Aid of Partial EHL Analysis
Authors: Tanaka S , Nakahara T , Kyogoku K , Momozono S
Published: April 2008

This paper describes an estimation method of the boundary friction coefficient of sliding parts under mixed lubrication condition. The boundary friction coefficients in a mixed lubrication regime have been identified by comparing the measured frictional characteristics with the calculated results obtained from the mixed lubrication analysis solving simultaneously the elastohydrodynamic lubrication equations and the contact ones. A block-on-ring friction tester set in a pressure vessel has been developed which is able to measure frictional characteristics in various lubrication conditions and many kinds of atmosphere. The test has been carried out in a refrigerant atmosphere.
A New Look at an Old Idea: The Torque Curve Revisited
Authors: Helmetag KM
Published: April 2008

Current lubricant testing methods for the pin and vee block machine produce only two data points, the torque at the final failure load, and the final failure load. Lubricant designers have had trouble correlating these single point data with field results. To obtain correlation of bench testing with field performance, it is imperative to examine all of the data produced during the course of the Extreme Pressure test, and appropriate plots of the data. An improved correlation of the laboratory test to industrial machinery performance has been found when plots of torque versus load are compared for lubricants under development. There are certain features in the torque versus load curve which can provide additional information and further improve correlation of bench test results to field data. An example metalworking process will be described.
Radiation Damage Assessment by the Use of Dynamic Toughness Measurements on Pre-Cracked Charpy-V Specimens
Authors: Lucon E , Chaouadi R
Published: April 2008

The small size of Charpy-type surveillance specimens can make it difficult to obtain fracture toughness measurements which are directly transferable to real-life structures. FEM calculations show that the pre-cracked Charpy specimen (PCCv) tends to lose constraint before the onset of cleavage. However, if the PCCv specimen is loaded under impact conditions, even for moderately strain-rate sensitive materials the deformation level at which loss of constraint occurs is significantly higher, due to the increase in flow properties. This implies that the ductile-to-brittle transition temperature measured under high rate conditions is shifted to higher temperatures with respect to quasi-static toughness tests. This circumstance has been verified through instrumented impact tests on PCCv specimens of two reactor pressure vessel steels, in both baseline and irradiated conditions. The dynamic reference temperature shift due to irradiation has been evaluated and compared with its static counterpart and with index temperature shifts based on conventional impact parameters. Furthermore, the possibility of predicting the dynamic To from the knowledge of the static values, the loading rate and the material's yield strength, has been investigated.
Comparison of Transition Temperature Shifts Between Static Fracture Toughness and Charpy-v Impact Properties Due to Irradiation and Post-Irradiation Annealing for Japanese A533B-1 Steels
Authors: Onizawa K , Suzuki M
Published: April 2008

It is assumed in the integrity analysis of reactor pressure vessel (RPV) that the irradiation-induced shift of fracture toughness in the ductile-brittle transition region is the same as the Charpy transition temperature shift. To confirm this assumption, both shifts are compared using irradiated and post-irradiation annealed RPV steels made by Japanese manufacturers. Five ASTM A533B class 1 plates having high- and low-level impurities, which correspond to first generation and modern Japanese reactors are used in this study. Neutron irradiation of precracked Charpy-v (PCCv) specimens as well as standard Charpy-v specimens was carried out at the Japan Materials Testing Reactor (JMTR). The values of fast neutron fluence for this study are 2 to 13×1019 (n/cm2, E>1MeV) considering typical fluence values at the EOL and extended operation of Japanese PWRs. The irradiation temperature was controlled within the range of 290±10°C. Thermal annealing treatments at 350°C and 450°C for 100 hours were performed for irradiated PCCv and Charpy-v specimens. The master curve approach according to ASTM Test Method for Determination of Reference Temperature, T0, for Ferritic Steels in the Transition Range (E1921) was applied using PCCv specimens. The irradiation-induced shifts of the reference temperature, ΔT0, obtained in this study were spread in the range of 10 to 200°C. The annealing recoveries of the reference temperature were compared with those of the Charpy transition temperature. Although large scatter was seen in the relation between ΔT0 values and Charpy 41J shifts, both shifts were almost the same in the average.
Yield and Toughness Transition Predictions for Irradiated Steels Based on Dislocation Mechanics
Authors: Wagenhofer M , Gunawardane HP , Natishan ME
Published: April 2008

An abundance of empirical data supports the use of the Master Curve, as proposed by Wallin, Saario and Törrönen, to describe the fracture toughness transition behavior of ferritic steels, particularly the notion of a curve shape that is invariant with steel microstructure (other than lattice structure). However, nuclear surveillance programs do not always contain samples of the steel that most limits reactor operations, making direct measurement of fracture toughness impossible. This suggests that a purely empirical argument cannot define the limits of applicability of the Master Curve or validate its use for all conditions of interest. In previous papers a microstructural basis for the existence of a single “Master” fracture toughness transition curve for all ferritic steels was established and limits of applicability have begun to be explored from a theoretical viewpoint. These previous papers established that all steels with the same lattice structure and cleavage fracture mechanism should be expected to adhere to transition behavior that can be defined by a single curve shape with variations in microstructure accounting only for a shift in the transition temperature. In this paper we explore the basis for “Master Curve” validity for irradiated steels by exploring how irradiation affects the microstructure and fracture mode and using the Zerilli-Armstrong constitutive model as the basis for predictions of irradiated steel behavior.
Fracture Toughness Characterization of 304L and 316L Austenitic Stainless Steels and Alloy 718 After Irradiation in High-Energy, Mixed Proton/Neutron Spectrum
Authors: Sokolov MA , Robertson JP , Snead LL , Alexander DJ , Ferguson P , James MR , Maloy SA , Sommer WF , Willcutt G , Louthan MR
Published: April 2008

This paper describes the fracture toughness characterization of annealed 304L and 316L stainless steels and precipitation hardened Alloy 718, performed at the Oak Ridge National Laboratory as a part of the experimental design and development for the Accelerator Production of Tritium (APT) target/blanket system. Materials were irradiated at 25 to 200°C by high-energy protons and neutrons from an 800-MeV, 1-mA proton beam at the Los Alamos Neutron Science Center (LANSCE). The proton flux produced in LANSCE is nearly prototypic of anticipated conditions for significant portions of the APT target/blanket system. The objective of this testing program was to determine the change in crack-extension resistance of candidate APT materials from irradiation at prototypic APT temperatures and proton and neutron fluxes. J-integral-resistance (J-R) curve toughness tests were conducted in general accordance with the American Society for Testing and Materials Standard Test Method for Measurement of Fracture Toughness, E 1820-99, with a computer-controlled test and data acquisition system. J-R curves were obtained from subsize disk-shaped compact tension specimens (12.5 mm in diameter) with thicknesses of 4 mm or 2 mm. Irradiation up to 12 dpa significantly reduced the fracture toughness of these materials. Alloy 718 had the lowest fracture toughness in both the unirradiated and irradiated conditions. All irradiated specimens of Alloy 718 failed by sudden unstable crack extension regardless of dose or test temperature. Type 304L and 316L stainless steels had a high level of fracture toughness in the unirradiated condition and exhibited reduction in fracture toughness to saturation levels of 65 to 100 MPa√m. The present reduction in fracture toughness is similar to changes reported from fission reactor studies. However, the currently observed losses in toughness appear to saturate at doses slightly lower than the dose required for saturation in reactor-irradiated steels. This difference might be attributed to the increased helium and hydrogen production associated with irradiation in the high-energy, mixed proton/neutron spectrum.
Review of Phosphorus Segregation and Intergranular Embrittlement in Reactor Pressure Vessel Steels
Authors: English CA , Ortner SR , Gage G , Server WL , Rosinski ST
Published: April 2008

This paper presents a systematic review of the behavior of phosphorus (P), highlighting the implications of P segregation to grain boundaries under neutron irradiation. The review focuses on Mn-Mo-Ni steels employed in US pressurized water reactors (PWRs), and other PWRs worldwide. Segregation of P to grain boundaries in reactor pressure vessel (RPV) steels can occur during fabrication (especially during the slow cooling stage of a post-weld heat treatment), and as a result of in-service exposure to high operating temperature and irradiation. This segregation of P to grain boundaries can promote a change in the brittle fracture mode from transgranular (TGF) to intergranular (IGF), and a degradation in the mechanical properties. In US RPV steels, most data are on thermal aging of the heat-affected zone (HAZ). Studies in coarse-grained HAZ have shown that the embrittlement arising from segregation of P to grain boundaries is approximately linearly related to the proportion of the brittle fracture that is IGF, and/or the P concentration at the grain boundary. Data are sparse on the effect of irradiation at 288°C on P segregation, and on the contribution of IGF to the total shift in the 41J transition temperature, T41J. In general, the bulk P content appears to be less than about 0.028 wt% P, with base metals having lower levels than weldments. In addition, the consequences of vessel annealing are considered at temperatures around 475°C. It is certain that the annealing treatment will have the consequence of reducing the irradiation hardening, but may significantly increase the grain boundary phosphorus coverage and the likelihood of IGF.
Grain Boundary Phosphorus Segregation Under Irradiation and Thermal Aging and Its Effect on the Ductile-to-Brittle Transition
Authors: Song S , Faulkner RG , Flewitt PEJ
Published: April 2008

Embrittlement of low-alloy steel components used in the nuclear power industry is classified into hardening embrittlement and non-hardening embrittlement. Hardening embrittlement stems from precipitation of carbides or copper-rich compounds. Non-hardening embrittlement results mainly from grain boundary segregation of phosphorus. To examine the non-hardening embrittlement in 2.25Cr 1Mo steel, phosphorus intergranular segregation in samples subjected to neutron irradiation and thermal aging at 270°C and 400°C is determined by modelling and transmission electron microscopy. The ductile-to-brittle transition temperature for the steel is determined by means of small punch testing with 3 mm diameter disc specimens. It is indicated that there is a reasonable agreement between the behavior of intergranular phosphorus segregation and shifts in the ductile-to-brittle transition temperature. Measured and predicted phosphorus intergranular segregation in a range of pressure vessel steels is also discussed.
Effects of Copper Concentration and Neutron Flux on Irradiation Hardening and Microstructure Evolution in Fe-Cu Model Alloys
Authors: Kasada R , Kitao T , Morishita K , Matsui H , Kimura A
Published: April 2008

Irradiation hardening and microstructure evolution under neutron irradiation have been investigated for pure Fe, Fe-0.15Cu, Fe-0.28Cu and Fe-0.46Cu alloys. All the alloys were annealed at 780°C for 20 min and quenched in iced water. Neutron irradiations were performed in the Japan Material Test Reactor (JMTR) up to a fluence of about 1 × 1022n/m2 at different fluxes (3.0 × 1016 and 1.5 × 1015 n/m2s) at 290°C utilizing a so-called “multi-division temperature control irradiation rig” to investigate flux effects under controlled irradiation temperature and flux. The irradiation hardening increased with increasing copper concentration. Positron annihilation lifetime spectrometry (PAS) revealed that the second lifetime component (τ2) was observed only in pure iron and Fe-0.15Cu alloy irradiated at the low flux condition. As for the flux effect, the irradiation hardening was larger at the lower flux condition in all the model alloys and A533B steel. Post-irradiation annealing experiments indicated that there were two recovery stages: the first was above 350°C and the second was around 550°C. The amount of hardening recovery in the first stage decreased with increasing copper concentration and depended on the flux; a larger recovery was observed at the lower flux condition. In contrast, the amount of recovery in the second stage increased with increasing copper concentration and was independent of the flux. It is considered that the first recovery is related to the annealing out-of-matrix defects and the second one is due to dissolution of copper precipitates. The τ2 of PAS disappeared after the annealing at 350°C, indicating that microvoids decomposed during the annealing.
Microstructural Evolution in High Nickel Submerged Arc Welds
Authors: Hyde JM , Ellis D , English CA , Williams TJ
Published: April 2008

The effect of nickel on irradiation sensitivity in ferritic steels is substantial, complex, and not yet fully understood. In this study, the evolution of irradiation induced microstructures in high nickel submerged arc welds has been examined in a series of small angle neutron scattering (SANS), field emission gun scanning transmission electron microscopy (FEGSTEM) and optical position sensitive atom probe (OPoSAP) experiments. For a low (~0.05%) copper content weld, SANS measurements showed that a high density of small features had been formed during irradiation. It was expected that clustering would be evident from visual examination of the OPoSAP elemental maps, but this was not the case. However, a statistical assessment of the data revealed that the manganese atoms were non-randomly distributed. For a medium copper (0.15%) weld, clusters were again not visible in OPoSAP, but non-randomness of both manganese and nickel could be detected at a low dose; at higher doses copper was non-random also. At high levels of copper (0.24% and 0.56%), clusters microalloyed with nickel, manganese, copper, silicon and iron were visible. The SANS data showed that the feature size tended to increase with copper and dose, but the number density remained fairly constant. The paper discusses how the differences between the SANS and OPoSAP data might be reconciled, and the implications in relation to the mechanisms of irradiation damage.
An Evaluation of the Effect of Radiation Environment on Linde 80 Reactor Vessel Welds
Authors: DeVan MJ , Pavinich WA
Published: April 2008

The B&W Owners Group (B&WOG) developed the Master Integrated Reactor Vessel Surveillance Program (MIRVP) to encompass all domestic operating pressurized water reactors (PWRs) with reactor vessels that contain Linde 80 submerged-arc welds. These PWRs include the reactor vessels fabricated by Babcock & Wilcox (B&W) that include B&W-designed 177-Fuel Assembly (FA) plants and Westinghouse-designed plants. The B&WOG Reactor Vessel Working Group has sponsored studies over the past several years to develop an understanding of the mechanisms and trends of radiation embrittlement for reactor vessel submerged-arc welds fabricated using Linde 80 weld flux. As part of the MIRVP, a Westinghouse-designed capsule was included to provide a comparison of irradiation data in the Westinghouse neutronic environment with the B&W 177-FA environment. This paper presents the effect of irradiation environment on the embrittlement trends of Linde 80 submerged-arc welds based on mechanical test data available through the B&WOG and the literature, and existing trend curves.
Reirradiation Response Rate of a High-Copper Reactor Pressure Vessel Weld
Authors: Iskander SK , Nanstad RK , Baldwin CA , Heatherly DW , Miller MK , Remec I
Published: April 2008

The Charpy impact response of reirradiated Heavy-Section Steel Irradiation (HSSI) Program Weld 73W has been determined at three fluence levels. The Charpy specimens had previously been irradiated at 288°C to 1.8 × 1019 cm-2 (E > 1 MeV) and annealed at 454°C for 168 h. The results show that the change in the 41-J Charpy energy level transition temperature (ΔTT41-J) of the reirradiated specimens is slightly higher than predicted by the vertical shift method, but significantly less than predicted by the lateral shift method. Previous results have also shown that the upper-shelf energy (USE) overrecovers as a consequence of annealing, which may explain why the USE value after a significant amount of reirradiation is approximately equal to the USE value in the unirradiated condition.
Fracture Toughness and Tensile Properties of Irradiated Reactor Pressure Vessel Cladding Material
Authors: Horsten MG , Belcher WPA
Published: April 2008

A comprehensive testing programme was undertaken to evaluate the effects of irradiation, thermal ageing, specimen orientation, and test temperature on the fracture oughness and tensile behaviour of a Type 309L/308L stainless steel strip clad deposit. Specimens were irradiated in the high flux reactor (HFR) Petten to nominal neutron doses of 0.05 dpa and 0.1 dpa at 295°C. Testing was performed at room temperature, 100, 200 and 295°C. The fracture resistance properties of the clad material were unaffected by irradiation to 0.1 dpa, which is approximately twice the predicted end-of-life dose. The same neutron dose resulted in an increase in 0.2% yield stress (15-20 MPa) and a small loss of ductility (3%). Thermal ageing to the simulated pressurised water reactor (PWR) end-of-life thermal condition (1000 hrs at 400°C) had no significant effect on the fracture resistance behaviour or tensile properties of clad material in either irradiated or unirradiated condition. Clad fracture resistance properties were unaffected by orientation in the plane of the clad layer and were only dependent on test temperature.
True Characteristics of Strength and Ductility for Neutron-Irradiated Metals and Alloys
Authors: Maksimkin OP , Tivanova OV
Published: April 2008

The results of comparative investigations of variations in engineering and true characteristics of strength and ductility for austenitic stainless steel 12Crl8NilOTi, high-nickel alloy 03Cr20Ni45Mo4, and commercially pure molybdenum irradiated by neutrons in the WWR-K reactor core at a temperature lower than 370 K and the fluences ranging from 5.1022 to 2.1024 n/m2 (E>0.1MeV) are presented.

In tensile experiments at 293 K at the constant strain rate ~10-4 c-1 the curve showing variations in geometrical dimensions of specimens was recorded together with the strengthening diagram. This revealed regularities in deformation-induced change of specimen diameters measured at various cross-sections over the specimen operating length, and allowed us to determine true values of the yield strength and the failure stress, and to find the value of narrowing related to the start of the localized plastic deformation.

For steel specimens, true values of strains and stresses (with the specimen diameter and length variations taken in account), corresponding to onset of recording the martensite ferromagnetic phase, are determined. It has been shown that, under the present test conditions, true stresses of á-phase formation in deformed steel are found to decrease as the neutron fluence increases.
Effect of Irradiation Environment of Fast Reactor's Fuel Elements on Void Swelling in P, Ti-Modified 316 Stainless Steel
Authors: Akasaka N , Yamagata I , Ukai S
Published: April 2008

The difference in swelling behavior of P, Ti-modified 316 stainless steel (PNC316) between sample irradiation using material irradiation vehicle (e.g. FFTF/MOTA) and fuel assembly irradiation in FBR was investigated. From the evaluation of the dose dependence in the swelling of PNC316, it is clearly shown that swelling of claddings irradiated by fuel assemblies occurred earlier than the swelling of samples irradiated by material irradiation vehicle in the range of irradiation temperatures from 723K to 823K. The microstructural evolution of the claddings irradiated by fuel assemblies, which is represented by void formation, should be mainly affected by the irradiation environments: irradiation temperature history, temperature gradient within the thickness of the claddings, and by the primary and secondary stresses within the cladding during irradiation.
The Swelling Dependence of Cold Worked 16Cr-15Ni-2Mo-lMn Steel on Neutron Irradiation Temperature, Fluence and Damage Rate During Its Use as a Cladding Material in the BN-600 Reactor
Authors: Kozlov AV , Kinev EA , Bryushkova SV , Portnykh IA
Published: April 2008

The radiation swelling of samples of fuel element cladding made of steel 16Cr-15Ni-2Mo-lMn after its use up to a maximum damage dose 73 – 93 dpa in the reactor BN -600 was studied. The samples were cut out from areas of different location in the core, so the irradiation temperature of various samples varied from 390 to 610 °C. The damage dose varied from 40 –92 dpa and the radiation damage rate varied from 0.9 ∙ 10-6 to 2 ∙ 10-2 dpa/s.

The conditions necessary to have the radiation swelling occurred were considered theoretically within the statistical thermodynamics of solids. An analytical expression connecting the incubation period of swelling with a temperature, fluence, radiation damage rate, and characteristics of material microstructure was obtained. The swelling rate at the post-incubation stage at various irradiation temperatures was estimated. The character of swelling dependencies on temperature, dose, and radiation damage rate obtained from the experimental data agreed well with the results of the theoretical analysis. In the range of 390 to 600 °C the nucleation damage dose initiating swelling increased with irradiation temperature. The swelling rate in the post-incubation phase also increased. Decreasing radiation damage rate shifted the fluence dependence of swelling into a region of lower fluences and temperatures.
High-Energy Spallation Neutron Effects on the Tensile Properties of Materials for the Target and Blanket Components for the Accelerator Production of Tritium Project
Authors: James MR , Maloy SA , Sommer WF , Johnson WR , Lohmeier DA , Hamilton ML
Published: April 2008

The Accelerator Production of Tritium (APT) project proposes to use a 1.0 GeV, 100 mA proton beam to produce neutrons by spallation from a tungsten target clad with Alloy 718. The neutrons are multiplied and moderated and then captured in 3He to form tritium. In this process, the materials in the target and blanket (T/B) region are exposed to a wide range of irradiation conditions. To test the effects of spallation neutrons on APT candidate materials, ASTM subsize samples were irradiated in a spallation neutron spectrum created from the interaction of an 800 MeV, 1 mA proton beam on a tungsten target at the Los Alamos Neutron Science Center (LANSCE). Specimens were located in controlled-temperature furnaces that were placed in proximity to the proton beam, but in locations where spallation neutrons would form the bulk of the exposure. The materials irradiated were the candidate APT materials 316L and 304L annealed stainless steels (SS), modified 9Cr-1Mo steel, and Alloy 718 (precipitation hardened). Irradiation temperatures varied from 100 to 280 °C and the approximate proton fluences were 4 × 1018 p/cm2. The neutron fluences were ∼5 × 1019 n/cm2 for energies < 0.1 MeV and 6×1019 n/cm2 for energies > 0.1 MeV with the spectra including a high-energy tail up to the proton beam energy (800 MeV). The samples experienced an exposure range of 0.023 to 0.051 dpa.

The tensile tests were conducted in air at ambient temperatures (∼20° C). The results indicated that even for low exposures (> 0.05 dpa), there was a decrease in ductility for the all of the alloys. Increases in yield and ultimate strength were observed in the austenitic stainless steels and the 9Cr-1Mo alloy. The Alloy 718 showed no change in yield strength but a marked decrease in the ultimate strength. The results are discussed and compared with results of the in-beam irradiated materials where smaller S-1 type tensile samples were used. Comparison also is made with irradiations of materials in fission environments in a similar dose and temperature environment.
On the α+γ↔γ-Phase Boundary in Nickel and in Manganese Containing Stainless Steel Alloys
Authors: Schüle W
Published: April 2008

The α-ferrite-phase in nickel and in manganese containing stainless steel alloys is very brittle. Its formation is connected with a huge decrease in volume, which also causes stresses in the alloys that are very dangerous if the materials cannot accommodate them. The α-ferrite-phase is formed in stainless steel alloys only if nucleation sites are provided, α′-martensites are nucleation sites for the formation of α-ferrite, even at temperatures at which α-ferrite is not stable. If α′-martensite is dissolved during an anneal, no new α-ferrite is formed, and the remaining α-ferrite transforms back into γ-austenite.

In “pure” nickel or in “pure” manganese containing stainless steel alloys the martensitic temperature is above 100°C and thus α′-martensite is always present at ambient temperature in these materials, giving rise to the formation of α-ferrite during a subsequent anneal. It was established in the present work that the γ↔γ+α-phase boundary in iron-chromium-nickel alloys is also almost independent of the temperature as in iron-chromium-manganese alloys. Thus the existing phase diagram for nickel containing stainless steels has to be revised. The various elements added to “pure” stainless steel alloys, as we find them in EUR-316L, US-316L, US-PCA, and in AMCR, cause a drastic decrease of the martensitic temperature so that neither α′martensite nor α-ferrite is found in these alloys.

However, in all these four alloys α-ferrite is formed readily during irradiation with high energy particles and a tentative γ↔γ+α-phase boundary, valid during irradiation with high energy particles, is derived. The amount of α-ferrite formed during irradiation increases with decreasing irradiation temperature and with decreasing applied stress. The alloys EUR-316L, US-316L, US-PCA, and AMCR do not survive one reactor cycle, if irradiated at 100°C.
Hydrogen and Helium Gas Formation and their Release Kinetics in Tungsten Rods after Irradiation with 800 MeV Protons
Authors: Oliver BM , Garner FA , Hamilton ML , Sommer WF , Maloy SA , Ferguson PD , James MR
Published: April 2008

In the Accelerator Production of Tritium Program, thermalized neutrons produced from multiplication and moderation of spallation neutrons will be absorbed in 3He gas to produce tritium. The spallation neutrons will be generated by the interaction of high energy (∼1 GeV) protons with solid tungsten rods. An unavoidable byproduct of the spallation reactions is large amounts of helium and hydrogen gas generated in the rods. The release kinetics of these gases during various proposed off-normal scenarios involving loss of coolant and afterheat-induced rises in temperature are of particular interest. In addition, the magnitude of the gas generation cross sections and the fractional retention of these gases is necessary for extrapolation of these data to higher exposures.

Tungsten rods irradiated with 800 MeV protons in the Los Alamos Neutron Science Center (LANCE) to rather high exposures have been sectioned to produce small specimens suitable for measurement of both helium and hydrogen. Hydrogen evolution was measured both by dropping the specimen into a small ceramic crucible at 1200°C and also by subjecting the specimen to a simulated temperature ramp from ∼200 to ∼1200°C, as has been calculated to be induced by loss of cooling and subsequent afterheat in an APT plant. The latter technique showed four distinct hydrogen release peaks at temperatures of approximately 500, 800, 1000 and 1200°C, suggesting a variety of trapping sites with different binding energies. Helium release and total content were easured by subjecting the specimens to the same temperature excursion, followed later by melting to release the remaining helium. Approximately 99% of the helium was retained until melting occurred. For both gases, release measurements were conducted using mass spectrometric techniques.

The measured amounts of helium agreed well with predictions. The hydrogen measurements were somewhat lower than predicted. This may reflect diffusional losses from the rods or some needed modifications in the evaporation model employed in the LAHET code.
Irradiation-Induced Amorphization and Its Recovery Behavior in Cold-Rolled and Aged Ti-Ni Shape Memory Alloys
Authors: Kimura A , Hirose T , Matsui H
Published: April 2008

The materials used were Ti-50.0, 50.5 and 51.0at%Ni alloys which were cold rolled and aged at 400°C for 1 hr. Neutron irradiation was performed in the Japan Materials Test Reactor (JMTR) up to a dose of 1.2 × 1024n/m2 at cooling water temperature (about 60°C), which meant the specimens were irradiated in the parent phase (B2). After the irradiation, micro-Vickers hardness measurements, microstructure observations by transmission electron microscope (TEM) and positron annihilation spectrometry (PAS) measurements were carried out. Differential scanning calorimetry (DSC) measurements were taken at temperatures between -120°C and 120°C. After the irradiation, all the alloys show extremely high irradiation hardening: the estimated increase in the yield stress of Ti-50Ni alloy is almost 1GPa. Although the hardness of the Ti-Ni alloys depends on the alloy composition in the unirradiated condition, all the alloys reach the same hardness value after the irradiation. DSC measurements revealed that the martensitic transformation was completely suppressed by the irradiation in all the alloys. PAS study revealed that no structural vacancies existed in the alloys before the irradiation, and that vacancies were formed after the irradiation. Microstructural observations indicate that disordered regions, which were considered to be amorphous, were homogeneously distributed in the irradiated parent ordered phase, accompanied by an appearance of the halo ring on the diffraction pattern. The irradiation effects disappeared following a post-irradiation anneal at 250°C for 1 hr. The recovery of the martensitic transformation by post-irradiation annealing is attributed to the migration of vacancies that causes the reordering. It is expected that Ti-Ni alloys are potential self-restorative materials for the irradiation above 250°C where vacancies are mobile.
Asphalt Concrete Smoothness Incentive Results by Highway Type and Design Strategy
Authors: Delton J , Li Y , Johnson E
Published: April 2008

The Arizona Department of Transportation (ADOT) implemented an incentive/disincentive asphalt concrete (AC) smoothness specification in 1990. Since then hundreds of projects have been tested for smoothness. These projects have included a wide variety of layer combinations of one or more of the following: overlay, remove, replace, and finishing course. The number of projects and variation in design allows comparisons of the smoothness results for different design strategies as well as trends in smoothness results over time. In addition to the tests on the final surface, many projects were also tested on intermediate lift surfaces.

A statistical analysis of the smoothness data is conducted to study the smoothness distribution and to compare the pavement smoothness of different categories. The smoothness correlation between various layers is also studied. The economic benefits of the implementation of ADOT's smoothness specification are evaluated. The results of this study can be useful in establishing target levels for newly implemented or revised pavement smoothness specifications.
Use of Automated Profilers to Replace NJDOT Rolling Straightedges
Authors: Zaghloul SM , Vitillo N
Published: April 2008

A study was performed to evaluate the applicability of using automated profilers to replace the Rolling Straightedges (RSEs) currently used by NJDOT to implement the department smoothness specifications. Two categories of profilers were considered in the study, two lightweight and three full size profilers, in addition to two NJDOT RSEs. Several analyses were performed on the collected data, which include preliminary analysis, RSE simulation, statistical analysis, speed effect analysis and correlation analysis. The RSE simulation analysis consisted of simulating a 10-ft (3.048 m) straightedge over the profile and calculating the deviation at the mid-point of the straightedge. The statistical analyses were performed to investigate the equipment repeatability and the differences among devices, including the two RSEs. Three correlation analysis studies were performed to correlate the RSE measurements with the results of the simulation analysis, to correlate IRI measured with different devices and to correlate the IRI and % defective length.
VDOT's IRI-Based Ride Quality Specification: From Inception to 2001
Authors: Clark TM , McGhee KK
Published: April 2008

In 1990, the Virginia Department of Transportation (VDOT) purchased its first South Dakota-type inertial road profiler. At that time, the profiler's primary function was to collect data required for the Federal Highway Administration's Highway Performance Monitoring System. By early 1995, however, the need to collect initial smoothness data safely, efficiently, and more accurately led VDOT to look to inertial profilers as a replacement for the California-type profilograph. In 1996, VDOT introduced a new special provision for smoothness, one that incorporated high-speed profilers and the International Roughness Index. In addition to chronicling those initial efforts, this paper discusses factors associated with achievable smoothness, as well as some deficiencies identified in the first generation of the new specification. The discussion then moves to a second generation of development, which focuses on enhancing the incentive/disincentive component of the specification, revising the smoothness targets, and reducing the pay lot size to combat excessive variability in ride quality.
Smoothness Index Relationships for HMA Pavements
Authors: Evans LD , Smith KL , Swanlund ME , Titus-Glover L , Bukowski JR
Published: April 2008

A recent Federal Highway Administration survey indicated that 48 states and Puerto Rico use smoothness specifications for hot-mix asphalt (HMA) pavement construction. As this is a relatively new concept, many states have adapted the Portland cement concrete pavement specifications of Profile Index using the standard 5-mm blanking band (PI5.0) for use on HMA pavements. However, PI5.0 may not provide a reproducible or portable smoothness measure for HMA pavements because of the technical limitations of the equipment and procedures.

The International Roughness Index (IRI) or the Profile Index using a 0.0-mm blanking and (PI0.0) seem to provide a more repeatable and portable smoothness standard. However, one barrier to more widespread implementation of these new smoothness standards is the lack of objective, verifiable correlation methods for use in establishing specification limits using the IRI or PI0.0. Assistance in selecting appropriate IRI and PI0.0 specification limits is needed to provide a basis for modifying current specifications to these more reproducible and portable smoothness indices.

This research effort has developed a relationship between IRI and PI that can assist in transitioning to a reproducible and portable initial IRI or PI0.0 smoothness specification for HMA pavement.
A Comparison of Devices Used to Measure Smoothness of Newly Constructed HMA Pavements
Authors: Wagner CT
Published: April 2008

The construction of the National Center for Asphalt Technology (NCAT) track was utilized to evaluate the possibility of using the automated walking Australian Road Research Board (ARRB) profiler, the McCracken (a California style profilograph), and the South Dakota Profiler for analyzing pavement smoothness. Results indicate that there was a poor correlation between the ARRB unit and the McCracken profilograph. The data from these two units should be evaluated independently. There was a fair correlation between the ARRB and the South Dakota profiler. Because the ARRB unit uses an inclinometer for determining the profile, use of this profiler should be limited to sections without severe superelevations.
Transferability Properties of Local Approach Modeling in the Ductile to Brittle Transition Region
Authors: Laukkanen A , Wallin K , Nevasmaa P , Tähtinen S
Published: April 2008

Qualitative descriptive potential of local approach models for upper shelf and transition region has been well established. Models such as the Gurson-Tvergaard-Needleman and the Beremin model have been demonstrated to enable characterization of fracture phenomena over the entire transition regime. The foundation for consistent local approach characterization of material failure has been set, but quantitative application is still at developing stages. Current work addresses properties of a modified Beremin model in terms of material parameter consistency and transferability, which are taken as measures of performance with respect to quantitative applicability. Three-point bend specimen fracture toughness data of sizes 3×4×27 mm, 5×5×27 mm, 5×10×55 mm and 10×10×55 mm are simulated in the ductile to brittle transition region using finite element methods and inference of local approach parameters is performed using pointwise collocation and stochastic methods. The suitability of the calibration methods and overall model performance are evaluated and demonstrated.
Temperature-Modulated Calorimetry of Polymers with Single and multiple Frequencies to Determine Heat Capacities as Well as Reversible and Irreversible Transition Parameters
Authors: Wunderlich B
Published: April 2008

Temperature-modulated differential scanning calorimetry (TMDSC) generated with a centrosymmetric saw-tooth oscillation can be considered to be a sinusoidal modulation with multiple frequencies. Different harmonics of the Fourier series of the heat-flow rate and heating rate of a single sawtooth-modulation can be deconvoluted to extract data pertaining to different frequencies. In order to give the higher harmonics similar amplitudes, a complex, but simple-to-program, sawtooth-modulation is generated for the harmonics 1,3,5,7 and 9. In this fashion a single experiment can produce a frequency-dependent analysis under identical thermal history. Application of this method to TMDSC includes the calibration for heat capacity determination of high precision, even if steady state and a negligible temperature gradient are not achieved. The measurement of the frequency (ω) dependence of the heat-flow rate (AHF) and sample temperature (ATs) allows to evaluate the expression: CP=AHF/(ATsνω)[1+(τνω)2]0.5 where the relaxation time τ is to be determined empirically from the multiple data generated by the single run. Typical values for the relaxation time for commercial calorimeters are between 3 and 9 s rad-1. Frequency-dependent, apparent reversing heat capacities in the glass transition region and within first-order transition regions may also be analyzed to study local equilibria in globally metastable polymeric solids.
Evaluation of the Curing Process in a Fiber-Reinforced Epoxy Composite by Temperature-Modulated and Step Scan DSC and DMA
Authors: Bilyeu B , Brostow W , Menard KP
Published: April 2008

Fiber-reinforced epoxy prepregs are commonly processed using isothermal curing. Although processing appears simple, the development of properties during curing is a complex multistep process. In addition, the relationship between the curing temperature and time to a specific conversion value is not linear. Industrial processing control can be simplified using a time-temperature-transformation (TTT) diagram. However, construction of a TTT diagram requires knowledge of the rate and degree of conversion as well as the time to reach gelation and vitrification at each isotherm. The rate and degree of conversion are determined either with a series of DSC isotherms which show the change of enthalpy in time or with the change in glass transition temperature (Tg) during the isothermal cure. Since gelation appears as a change in physical properties, it is conveniently determined by DMA. Vitrification is a rubber-to-glass transition and appears in both DMA and DSC. Although vitrification is commonly determined by DMA, DSC offers increased temperature accuracy and control. However, since vitrification occurs before complete conversion, the Tg is usually masked by the curing exotherm in traditional DSC. Since vitrification and curing are thermodynamically different effects, the two signals can be separated using either Temperature Modulated DSC (TMDSC) or Step Scan DSC.
Effects of TMDSC Variables on the Observed Glass Transitions of Elastomers- a Statistical Analysis
Authors: Ludwig KN , Burkholder KE , Willey JF , Riga AT
Published: April 2008

A two-level, three-variable full factorial experimental design was employed to probe the effects of temperature-modulated differential scanning calorimetry variables (heating rate, modulation frequency, and modulation amplitude) on the observed glass transitions of polybutadiene, poly(styrene-co-butadiene) and polystyrene. The statistical significance of individual variables was ascertained by Student's t-tests. Standard least-squares fitting of the model was employed to determine interaction effects between the variables. Frequency was determined to have a statistically significant effect on extrapolated onset glass transition temperature, half- height glass transition temperature, and the change in heat capacity across the glass transition for all three polymers. Within the confines of these experiments, changes in heating rate and amplitude did not have a statistically significant effect on glass transition measurement. No synergistic interaction effects were observed between the variables.
Application of Theory to Prediction and Analysis of Dynamic Mechanical Properties of Polymer Composites
Authors: Goldman AY
Published: April 2008

A comparison was made between experimental and computed dependencies of the dynamic modulus, and the mechanical loss tangent of the composites with a glassy polymer matrix - styrene-acrylonitrile (SAN) or (SAN-P) acrylonitrile-methacrylate-styrene in ASA plastic (acrylonitrile-styrene-acrylic) copolymer with particles of a peroxidic butylacrylate rubber (BAR-P). The composite material was obtained by emulsion polymerization.

An algorithm was developed for determining, prediction and optimization of the viscoelastic properties of composite materials with spherically layered inclusions by varying microstructure parameters.

The dynamic mechanical characteristics of the grafted copolymer that form a part of the ASA plastic allow the viscoelastic properties of ASA plastic to be predicted with better precision than if the dispersed face were identified with the BAR-P itself.
Glass Transition Temperature of Selected Polymers by TMDSC, DMTA and DETA Analyses
Authors: Righetti MC , Pizzoli M , Ceccorulli G
Published: April 2008

Dynamic glass transition, related to the cooperative motions of amorphous polymeric segments, can be investigated by means of periodic techniques. Recently, temperature modulated differential scanning calorimetry (TMDSC) has offered the possibility to obtain α relaxation data at very low frequency (below 0.2 Hz). In this paper dynamic glass transition temperatures of an amorphous and two semicrystalline polymers, obtained by means of TMDSC, have been compared with dynamic mechanical (DMTA) and dielectric (DETA) results. The DMTA and DETA scans were performed at 3 Hz and in the frequency interval 102–104 Hz respectively. The frequency dependence of calorimetric, dynamic mechanical as well as dielectric data has been found successfully described by the Vogel-Fulcher-Tammann equation in the whole range of frequency investigated.