bluuebunny/crossref_metadata_2025 huggingface dataset:
Radiation Stability of WWER-440 Vessel Materials
Authors: Amayev AD , Kryukov AM , Levit VI , Sokolov MA
Published: March 2009

The main results of a complex investigation of radiation embrittlement of WWER-440 reactor vessel (RV) materials, carried out in the former USSR are presented. The object of the investigation was surveillance specimen (SS) evaluations of RV materials. It has been found that at an irradiation temperature of 270°C neither the base metal (steel 15 Kh2MFA) nor weld metal exhibits saturation of radiation embrittlement in irradiation of specimens up to neutron fluences of 7 × 1020 n/cm2 (E > 0.5 MeV). Regularities in the influence of impurity elements (copper and phosphorus) on radiation embrittlement of RV materials have been investigated. It is shown that radiation embrittlement of the weld metal is determined by at least four processes associated with the individual effects of copper and phosphorus, their joint effect, and the mechanism of direct buildup of radiation defects in the metal. The effect of dependence of the radiation embrittlement characteristics of the WWER-440 RV materials on the neutron flux has been found. It is shown that within the range of fluences from 1 to 5 × 1018 n/cm2 at a neutron flux of 4 × 1011 n/cm2˙s, radiation embrittlement is stronger than in irradiation at a neutron flux of 3 to 4 × 1012 n/cm2˙s. A tendency has been observed for the values of the radiation embrittlement coefficients AF, characterizing sensitivity of the steel to radiation embrittlement, to reduce with an increase of neutron fluence in irradiation of specimens with a neutron flux of 4 × 1011 n/cm2˙s.
Analysis of the Surveillance Results at Paks Nuclear Power Plant
Authors: Oszvald F , Trampus P
Published: March 2009

The surveillance results of the reactor pressure vessels (RPVs) at Paks Nuclear Power Plant (NPP) in Hungary are summarized. The yield strength increase has relatively high scatter because of surface anomaly of the specimens. The transition temperature shifts of the weld metals for Units 1 and 2 and for Units 3 and 4 are the same. Valid RTIc could be determined only on weld metal specimens. The dose rate was not found to have any effect on the hardness.
Analysis of Radiation Embrittlement Results from a French Forging Examined in the Second Phase of an IAEA-Coordinated Research Program
Authors: Soulat PE , Houssin B , Bocquet P , Bethmont M
Published: March 2009

Test blocks of a manganese-nickel-molybdenum (Mn-Ni-Mo) low-alloy steel, machined from a nozzle cut-out of a 230-mm-thick forging shell, were provided by France in 1978 to be investigated in the second phase of an IAEA-coordinated research program on the behavior of advanced pressure vessel steels under neutron irradiation.

The results obtained by different laboratories exhibit a great deal of scatter in Charpy-V transition temperatures, both in the initial condition and after neutron irradiation. Therefore, the shifts in Charpy-V transition curves induced by neutron irradiation at similar fluences of about 3 × 1023 n ∙ m-2 (E ⩾ 1 MeV) cover a wide temperature range from 0 up to 110°C.

A more detailed investigation of these results was undertaken, and additional Charpy tests were conducted to clarify the considerable uncertainty about the sensitivity of this forging to radiation embrittlement. The differences in results were found to be due to the various orientations and locations of the Charpy-V specimens extracted by the different laboratories, in some cases to insufficient test data in the transition region of the Charpy curve, and to the detrimental effect on Charpy-V properties of segregated zones (ghost lines) found in specific locations of large forgings.
Neutron Fluence Management to Optimize Pressure Vessel Lifetime
Authors: Lefebvre JC , Leroy P , Rieg C , Schaeffer H , Nimal JC , Lloret R
Published: March 2009

Pressure vessel steel embrittlement management is needed to predict the tearing resistance at end of life, but also to update these predictions taking into account the evolution of the principal parameters, such as fuel management, thermohydraulics of the primary coolant circuit, and lifetime extension capability.

French 900-MW units are characterized by a high neutron fluence on the inner face of the pressure vessel at the predicted end of life. Electricité de France's (EDF) purpose is to establish the appropriate knowledge and software to predict the pressure vessel embrittlement during operation.

This work is in progress in two ways. First, appropriate existing software is being used to calculate the consequences in terms of neutron flux, on the inner face of the pressure vessel, of various operating conditions and fuel patterns, and to be able to select the best of these. Second, specific software is being developed to calculate the maximum neutron flux on the inner face of the pressure vessel, according to the contribution of the major fuel elements so we can appreciate the fluence level of each refueling pattern and choose the one that is less severe. These results have shown that a benefit of about 30% can be obtained by optimized patterns with high discharge burn-up.

Neutron fluence management can be successfully integrated in the core refueling calculation procedure, but further progress is necessary for complete validation and background to optimize the steel surveillance program.
Evaluation of the Recovery Annealing of the Reactor Pressure Vessel of NPP Nord (Greifswald) Units 1 and 2 by Means of Subsize Impact Specimens
Authors: Ahlstrand R , Klausnitzer EN , Lange D , Leitz C , Pastor D , Valo M
Published: March 2009

In 1988 and 1990, the reactor pressure vessels of Units 1 and 2, respectively, of the Greifswald nuclear power station were subjected to heat treatment at 475°C for annealing of irradiation effects. To demonstrate the effect of annealing and to evaluate a new postannealing transition temperature of vessel base metal and weld metal, boat samples were removed by means of electric discharge machining (EDM) from the (unclad) inner surface of the vessel. From these samples, micronotched bar impact test specimens were fabricated and tested at different temperatures. Transition curves were evaluated from the results. By means of correlation tests, the transition temperatures evaluated from the micro-specimen tests are converted to standard Charpy-V transition temperatures. Results are available for the weld metal of Unit 1 after annealing. The transition temperature TK is lower than the value calculated by the designer of the plant. Specimens removed from Unit 2 before and after annealing are in preparation.
Continuous and Sequential Multiaxial Low-Cycle Fatigue Damage in 316 Stainless Steel
Authors: Weiss J , Pineau A
Published: March 2009

Tension and torsion low-cycle fatigue tests were carried out on thin tubular specimens of 316 stainless steel, tested at both room temperature and 600°C. Two types of experiments were performed: (1) conventional continuous isothermal tests, and (2) isothermal sequential tests with different sequences of tension/compression and torsional loading. Most of these tests were carried out under air environment at the equivalent total strain amplitude of Δεt/2 = ±0.80% in tension or Δγt/2 = ±0.80 √3% in torsion. Optical and scanning electron microscopy were used to analyze the failure modes, the orientation of microcracks and macrocracks which lead to failure, and crack density.

Continuous tests show two main results: (1) it is confirmed that, for the same equivalent von Misès strain, the fatigue lives in torsion are larger than those observed in tension; (2) detailed examinations of the microcracks' orientation showed that Stage I initiation followed by Stage II growth occurs only at room temperature or at elevated temperature under vacuum. At 600°C, however, Stage I crack initiation is bypassed due to the formation of external hematite (Fe2O3) and internal (Fe-Cr rich) oxides.

These results are used to explain qualitatively the significant deviations observed in the sequential tests from the Miner linear cumulative damage rule. A quantitative model based on a Monte Carlo simulation is developed to account for the results of sequential tests in which crack initiation and crack growth were coplanar. This model includes three fatigue damage laws: (1) a nucleation rate equation; (2) a push/pull or torsion crack growth law; and, (3) a criterion for crack coalescence. It is shown that this model is able to reproduce with good accuracy the results of sequential push/pull → torsion tests carried out at 600°C.
A Simple Test Method and Apparatus for Biaxial Fatigue and Crack Growth Studies
Authors: Zamrik SY , Davis DC
Published: March 2009

A simple method and unique test apparatus are presented for conducting fatigue and fatigue crack growth studies using plate-type specimens under biaxial bending. The test method and apparatus design make use of the concept of anticlastic bending of a plate with a rhombic configuration. The simplicity and uniqueness of the test apparatus are that with one constant load amplitude, a wide variety of stress or strain biaxial ratios can be attained by varying only the lengths of the rhombic plate diagonals. The test apparatus and rhombic plate specimens have been used for low cycle fatigue, cumulative fatigue damage, and mixed-mode fatigue crack growth studies of engineering materials under biaxial bending. Some results from these previous research studies will be discussed in this present paper to illustrate the utility of the test method and apparatus.
Viscoplasticity Theory Based on Overstress: The Modeling of Biaxial Cyclic Hardening Using Irreversible Plastic Strain
Authors: Choi SH , Krempl E
Published: March 2009

Cyclic hardening behavior of stainless steel under various loading paths is modeled by using the small-strain, isotropic theory of viscoplasticity based on overstress. The cyclic hardening is modeled by postulating a growth law of an internal variable which is equivalent to isotropic hardening of yield surface plasticity. The growth of the hardening variable is formulated in a discrete way by using changes in the direction vector of the inelastic strain rate and the concept of irreversible plastic strain. The irreversible plastic strain is given as a function of variables representing amplitude, nonproportionality, and the history of the loading path. This formulation does not use separate growth laws for proportional and nonproportional loading. They are handled by a difference of the direction vectors of inelastic strain rate before and after it changes its direction. The capability of the model is demonstrated by numerical experiments for various loading conditions.
Cycle-Dependent Ratcheting Under Multiaxial Loads Including the Bauschinger Effect and Nonlinear Strain Hardening
Authors: Garud YS
Published: March 2009

This paper presents a study of the phenomenon of cycle-dependent strain accumulation (ratcheting), especially under multiaxial steady and cyclic loads. The practical significance of ratcheting has become more apparent in recent years in dealing with the design/analysis of pressure-retaining components and structures which may be subjected to certain (reversed) thermal or seismic (dynamic) cyclic loads. A review of experimental observations on the fatigue and ratcheting response of such components suggests that the likely mode of failure (under the noted load combinations) is different from the plastic collapse (as assumed for design basis); this provides an opportunity to reduce the over-conservative safety margin requirements. Based on a brief survey of prior material test data and theoretical evaluations of the ratcheting under multiaxial stress conditions, it is concluded that a proper accounting of the material strain hardening and yield behavior (the Bauschinger effect) under multiaxial stresses is needed and can serve a useful purpose.

The nonlinear strain hardening and the Bauschinger effect are taken into account in this work by using the full implementation of incremental plasticity based on the generalized kinematic-type hardening proposed previously by the author. It is shown that, under certain combined stress conditions, the incremental plasticity predicts continued strain accumulation in each (half) cycle even for a kinematic-type hardening assumption. A number of characteristic observations on ratcheting under multiaxial loads are also predicted.

The case of triaxial steady stress with imposed cyclic strain is analyzed in detail; this is similar to typical loads on a pipe section. For such a case the theory predicts conditions of (local) wall thinning and circumferential growth (in the pipe section) that is limited mainly by the structural considerations. For Type 304 stainless steel and A333 Grade 6 carbon steel a graphical representation is developed showing allowable load combinations for various rates of strain accumulation. A simple relation is proposed between the (steady) primary stress and the (cyclic) secondary stress for a specified total ratchet strain as a criterion which is discussed with reference to the ASME Code. The extent of over-conservatism associated with the neglect of material strain hardening and with the (change in) mode of failure can be better judged by means of the results presented here. The paper is concluded with a discussion of related issues and the future direction.
Comparison in Rolling Contact Fatigue Life Between Recent Clean Through-Hardening Steels and Carburizing Steels
Authors: Tsushima N , Nakashima H , Maeda K
Published: March 2009

Rolling contact fatigue lives of through-hardening steels and carburizing steels are getting close if compared with regard to 10% life. However, carburizing steels are more reliable than through-hardening steels because they have longer life with regard to 1% life. In this way, carburizing steels show superiority to through-hardening steels under lubrication conditions less contaminated. However, they lose their superiority when used under contaminated lubrication or high loading conditions. To increase rolling contact fatigue life of carburizing steels, it is effective to increase case depth. By increasing case depth, the life of a carburized bearing increased significantly under clean oil lubrication as well as under contaminated lubrication and high loading conditions.
Tribological and Metallurgical Evaluation of Ferritic Nitrocarburized M-50 and M-50 NiL Steels
Authors: Braza JF , Pearson PK
Published: March 2009

In this paper, the ferritic nitrocarburizing process (fluidized bed and gaseous ferritic nitrocarburizing) is explored as a means to increase the rolling contact fatigue (RCF) life and sliding wear resistance of M-50 and M-50 NiL under simulated high stress, marginally lubricated conditions. Test results confirmed the detrimental quality of the surface iron carbonitride compound layer and the beneficial aspect of the diffusion zone below the surface. Test specimens with the compound layer ground off gave substantial improvement in RCF life over the baseline M-50 and M-50 NiL steels. The ferritic nitrocarburizing process had little effect on the sliding wear performance of M-50, which was far superior to the ferritic nitrocarburized M-50 NiL or untreated M-50 NiL. The hardness of the diffusion zone and the generation of large compressive residual stresses contribute to the prominent enhancement of mechanical properties by this surface modification.
Development of a Stainless Corrosion Resistant Carburizing Bearing Steel
Authors: McCaffrey TJ , Wert DE
Published: March 2009

The development of a stainless corrosion resistant carburizing bearing steel by Carpenter Technology Corporation is detailed. The alloy, Carpenter VIM-VAR Pyrowear® 675 Stainless alloy, has corrosion resistance equivalent to Type 440C stainless, combined with fracture toughness superior to any martensitic stainless steel and equivalent if not superior to normal noncorrosion resistant carburizing bearing steels such as SAE Type 8620 or 9310.

The discussion will include case and core properties, and carburizing techniques employed to optimize case structures.

The alloy is capable of maintaining a case hardness of HRC 59 at 329°C (625°F). This capability, along with superior fracture toughness compared to both the currently used M50 and the newly developed M50NiL, makes it a viable candidate for main shaft bearings for turbojet engines.
A Ferritic-Pearlitic Steel with Eutectoid Composition
Authors: Andersson-Drugge I-M , Lund T
Published: March 2009

By alloy design based on demands for formability and high martensitic hardness, a new high-carbon, low-alloy steel has been developed. The steel, which minimizes the use of all elements except carbon and molybdenum, exhibits a microstructure and properties normally not attained in high-carbon steels. On retarded cooling, the steel, which has eutectoid composition, generates substantial amounts of pro-eutectoid ferrite in combination with a coarse, degenerated pearlite. The pro-eutectoid is not ferrite, but an eutectoid itself composed of nanometer-sized, evenly distributed molybdenum carbides and ferrite.

The new steel provides a soft and formable structure in the as-rolled condition, and hardens to high martensitic hardness at austenitization conditions equal to those used for high-carbon, low-alloy steels.
Rolling Contact Bearing Steel for Operation at 120 to 250°C
Authors: Chu H , Chen C , Yang J
Published: March 2009

Differential dilatometric testing results show that the composition strengthening of chromium, silicon, tungsten, and vanadium increases the stability of overcooled austenite, shifting the T-T-C curve to the right and lowering the Ms point, thus an air-hardening phenomenon occurs. Phase analysis indicates that, in the quenched state, all of the silicon and one third of the tungsten dissolve into solid solution. This increases the softening resistance of martensite upon tempering and increases the transformation temperature as well, so that the tempering temperature range of the second stage is broadened. Addition of vanadium and tungsten changes the type, particle size, and distribution of carbides. The mutual action of the matrix and carbides makes the steel, GCrSiWV, tempered at 300°C, have superior tempering stability, dimensional stability, hot hardness, and high temperature contact fatigue life. The fatigue life, L10 of GCrSiWV steel at 250°C, is six or four times higher than that of GCrl5 or M50 steel, respectively.
Improved Properties of Bearing Steels by Advanced Metallurgical Processing
Authors: Baum R , Böhnke K , Otto J , Pflipsen HD
Published: March 2009

The completion of the EAF-Ladle Degassing (LD)-Ingot Casting (IC) route at TEW, Witten works, by a Ladle Furnace (LF) together with the aluminum predeoxidation instead of the formerly vacuum carbon deoxidation (VCD) results in further improved oxide cleanness values of through-hardening bearing steels expressed by decreased macro-inclusions and oxygen contents. In the BOF-RH-degassing-IC and CC route at Thyssen Stahl, Duisburg works, the replacement of RH-degassing by the newly installed (LD) also improves the steel cleanness. Contrary to continuous casting (CC), stream shrouding in uphill IC has only a marginal effect on steel cleanness. The use of high alumina trumpet and runner bricks in uphill IC instead of fire-clay materials also does not improve the cleanness of through-hardening bearing steels. The investigation of carbon segregation in as cast ingots and continuous casting of different shapes and sizes quantifies significant differences of segregation pattern and degree. However, after an appropriate high-temperature annealing before rolling or forging, the customer's specification of carbide size and distribution is well achieved. From the comparison of the reported results with regard to cleanness and segregation, it can be concluded that continuous casting should allow the same application as ingot casting.
Spontaneous Ignition Temperature of Tracheal Tubes
Authors: Wolf GL , McGuire JG , Nolan PF , Sidebotham GW
Published: March 2009

Operating room fires continue to be reported in the medical literature. To simulate operating room conditions, a high pressure spontaneous ignition apparatus was redesigned to allow for the determination of spontaneous ignition temperature of trachea! tubes in 100% oxygen at atmospheric pressure. Pure oxygen flowed through a test chamber at 100 cm3/min, and a temperature ramp rate of 10°C/min was used. Sample temperature, chamber temperature, chamber pressure and elapsed time were stored on-line by computer. The experimental ignition temperature was observed as a spike in sample temperature-time plot.

Five samples each of poly (vinyl chloride), red rubber and silicone rubber tracheal tubes were analyzed for spontaneous ignition temperature, which were determined to be 428°C, 371°C, 381°C, respectively.

It was concluded that the small differences in spontaneous ignition temperature for the various tracheal tube materials has little clinical relevance to the tubes chosen for the particular surgical procedure.
Effects of Diluents on Flammability of Nonmetals in High-Pressure Oxygen Mixtures
Authors: Hirsch DB , Bunker RL
Published: March 2009

NASA White Sands Test Facility recently investigated the effects of diluents on flammability of nonmetals. Downward-flame propagation flammability tests were conducted on Teflon PTFE, Kel-F 81, and Viton samples, using helium, nitrogen, argon, and neon diluents.The tests were conducted at 6.9 MPa (1000 psia), 20.7 MPa (3000 psia), and 34.5 MPa (5000 psia) using various diluent/oxygen mixtures. The test objective was to determine the minimum diluent concentration required to extinguish the burning sample. The data indicated that at pressures of 6.9 MPa (1000 psia) and higher, the materials tested (which are among the most commonly used nonmetals in oxygen systems) would burn even in low-oxygen concentrations. Large quantities of diluents, approximately 60 percent and higher, were required to prevent sustained combustion. Helium was the most effective diluent for preventing flame propagation, followed by nitrogen, neon, and argon. The effectiveness of helium could be explained by its high thermal conductivity, which could have resulted in reduced heat-feedback to the burning material. For a given pressure increase, the increase in diluent concentration required for sample extinguishment was higher for Teflon PTFE and Kel-F 81 than for Viton. At some pressure between 20.7 MPa (3000 psia) and 34.5 MPa (5000 psia), Teflon PTFE and Kel-F 81 became flammable in air, indicating that high-pressure air systems require careful selection of appropriate nonmetallic materials and design considerations to avoid ignition sources.
Evaluation of Bronze Alloys for use as Wear Ring Material in Liquid Oxygen Pump
Authors: Yentzen MJ
Published: March 2009

The selection of materials for wear parts in oxygen pumps or compressors is critical from an oxygen compatibility perspective because the function of the part is to absorb frictional energy. Part of this energy is absorbed by the sample as heat and can cause ignition of the material. There is little data on the compatibility of bronze alloys typically used for wear parts in oxygen systems, so it is difficult to ensure that the most compatible materials are used.

This paper discusses frictional heating test data obtained for seven bronze alloys which could be used in certain applications as wear parts. A test apparatus developed by the NASA test facility at White Sands to determine the resistance of materials to ignition by friction was used to obtain the data. The bronzes evaluated were selected based on the ability to function mechanically in the intended application and the anticipated resistance to ignition by friction. The alloys were ranked according to the resulting pressure-velocity (PV) product. This factor serves as a measure of the load required for ignition given a constant sample load rate, a constant gaseous oxygen pressure, and a constant sample rotational velocity. Factors influencing the test results including sample composition, material properties, and test procedures are addressed. A simple theoretical description of the phenomenon of ignition by friction is presented to explain the effects that the proposed variables may have on the PV product.
Gravity and Pressure Effects on the Steady-State Temperature of Heated Metal Specimens in a Pure Oxygen Atmosphere
Authors: Feiereisen TJ , Branch MC , Abbud-Madrid A , Daily JW
Published: March 2009

A fundamental description of the heat transfer mechanisms leading to the combustion of metals in a pure oxygen atmosphere over a range of levels of gravity is important in understanding spacecraft fire safety. In this study, a new method of metal specimen heating to the point of combustion by focused optical radiation was used. A computational model of the laboratory combustion chamber and specimen heating was developed. Accuracy of the computational software was evaluated with two test cases comparing calculated output with experimental data from the literature. Model accuracy was evaluated by comparing computational output with experimental data at 1.0 g and 0.1 MPa. A range of gravity from 0.0 g to 10.0 g and a range of pressure from 0.01 MPa to 1.0 MPa was then explored. The results indicated that for a constant input heat flux on the specimen, convection heat transfer increased and asymptotically approached a limit for both the increased gravity case and increased pressure case. This limit in convection heat transfer caused a limit in minimum specimen temperature regardless of gravity field magnitude or chamber pressure within the ranges studied. In addition, it has been shown computationally that the microgravity laminar free convection environment can be simulated in the terrestrial laboratory by reducing the ambient pressure.
Ignition of Bulk Metals by a Continuous Radiation Source in a Pure Oxygen Atmosphere
Authors: Abbud-Madrid A , Branch MC , Feiereisen TJ , Daily JW
Published: March 2009

The present work investigates the mechanisms that lead to ignition and subsequent self-sustained combustion of bulk metals. To this effect, an experimental study isolating the ignition process was conducted with the novel feature of using a short-arc lamp as a non-coherent, continuous radiation source. A 1000 W xenon arc lamp was used to irradiate the top surface of a cylindrical metal specimen 5 mm in diameter and 5 mm high in a quiescent pure-oxygen (O2) environment at an absolute pressure of 0.1 MPa. Measurement of surface temperature histories and a qualitative visual record of the ignition process and the subsequent self-sustained combustion event were obtained. Iron (Fe), titanium (Ti), zirconium (Zr), magnesium (Mg), zinc (Zn), tin (Sn), copper (Cu) and aluminum (Al) specimens were investigated. All metals exhibited ignition and sustained combustion except with the aluminum sample. Ignition temperatures below, above or in the range of the metal melting point were found. Ignition and combustion of copper rods at 0.1 MPa in normal gravity conditions revealed the dramatic effect of sample geometry, experimental configuration and ignition source on the ignitability and flammability of bulk metals.
Combustion Characteristics of Polymers as Ignition Promoters
Authors: Shelley RM , Wilson DB , Beeson H
Published: March 2009

Four polymers, which were high density polyethylene (HDPE), polytetrafluoroethylene (PTFE), unfilled polyimide (PI), and graphite-filled polyimide (GPI), were burned in high pressure oxygen over the range 0.7 to 69 MPa. Three metallic materials were used as support rods: aluminum 2216, stainless steel 316, and pure copper. Flame characteristics of the polymers are described, as well as the polymer potential for igniting the metal support.

HDPE burns at all pressures with a diffusion flame, PTFE burns at all pressures as a surface burner, PI and GPI are combined surface and diffusion flame burners. Flame compositions and temperatures were estimated based on computer calculations (Gordon McBride) and experimental melting characteristics of the aluminum rods.
Evaluation of Buna N Ignition Hazard in Gaseous Oxygen
Authors: Shelley RM , Christianson R , Stoltzfus JM
Published: March 2009

The NASA Johnson Space Center White Sands Test Facility (WSTF) evaluated the ignition hazards of a section of Buna N rubber suspected to be lodged in a gaseous oxygen system. A configuration simulation tester was used to test for the minimum mass of Buna N required to cause an ignition hazard, which meant ignition of the Inconel 718 metal structures of the oxygen system. High-density polyethylene (HOPE), a comparison material with a higher heat of combustion than Buna N, was also tested. Analytical techniques were performed on the Buna N rubber and the HOPE to investigate the polymer-to-metal ignition process. The minimum weight required to cause ignition in the Inconel 718 was 1.5 mg, which was more than the 0.1–0.2 mg of contaminant found in the oxygen system. HOPE had a lower propensity to ignite the Inconel 718 even though it has a much higher heat of combustion than Buna N; this result was explained in terms of the different structures of the two polymers. Additional testing was conducted to examine the differences of two different batches of Buna N at 10 ± 0.5-mg samples. Buna N was found to be batch sensitive in its ignition performance; batch differences were more easily discernible by analytical techniques.
Prediction of Localized Corrosion Using Modeling and Experimental Techniques
Authors: Sridhar N , Cragnolino GA , Walton JC , Dunn D
Published: March 2009

An overall approach to life prediction of a component undergoing localized corrosion involving initiation and repassivation is considered. A crevice corrosion initiation model for Fe-Ni-Cr-Mo alloys is presented in this paper. This is a finite difference model that considers the combined effects of hydrolysis and transport in predicting the evolution of the solution chemistry inside a crevice of a given geometry. Crevice corrosion initiation time is computed by equating the time it takes for the crevice-solution chemistry to evolve to a critical solution chemistry for the depassivation of a given alloy. Depassivation pH is measured on non-creviced (open) samples as a function of environmental factors such as temperature, chloride, and sulfate. The measured depassivation pH is then used as an input variable in the crevice corrosion model to calculate the initiation time. The use of crevice corrosion repassivation potential as a bounding parameter for performance prediction is also examined. The limitations of the current models and future directions are identified.
Reduced Activation Austenitic Stainless Steels: The Fe-Mn-Cr-C System
Authors: Klueh RL , Maziasz PJ
Published: March 2009

Nickel-free manganese-stabilized stainless steels are being developed for fusion reactor applications. As the first part of this effort, the austenite-stable region in the Fe-Mn-Cr-C system was determined. Results indicated that the Schaeffler diagram developed for Fe-Ni-Cr alloys cannot be used to predict the constituents expected for high manganese steels. This indicator is true because manganese is not as strong an austenite stabilizer relative to δ-ferrite formation as predicted by the diagram, but it is a stronger austenite stabilizer relative to martensite than predicted. Therefore, the austenite-stable region for Fe-Mn-Cr-C alloys occurs at lower chromium and higher combinations of manganese and carbon than predicted by the Schaeffler diagram. Development of a manganese-stabilized stainless steel should be possible in the composition range of 20 to 25% manganese, 10 to 15% chromium, and 0.1 to 0.25% carbon. Tensile behavior of an Fe-20%Mn-12%Cr-0.25%C alloy was determined. The strength and ductility of this possible base composition was comparable to Type 316 (UNS 531600) stainless steel in both the solution-annealed and cold-worked condition.
Irradiation Effects on Mechanical Properties of High Manganese Steels
Authors: Yoshida H , Miyata K , Kodaka H , Nishikawa S
Published: March 2009

Several high-manganese austenitic steels and ferritic steels were studied by means of mechanical tests in order to develop materials for reduction of radioactivity of the first wall material after irradiation in a fusion reactor. After testing the commercial high manganese austenitic steels (that is, Fe-22%Mn-13%Cr-5%Ni), a new type of high manganese austenitic steels (that is, Fe-17%Mn-6.5%Cr-4.5%Si and Fe-22%Mn-6.5%Cr-4.5%Si-0.2N) was developed. Tensile tests were performed using miniature specimens in the temperature range between 4 and 500 K. Instrumented Charpy impact tests were also performed using quarter-size specimens at 77 to 550 K. It was found that the new steels show high strength and good ductility before irradiation. Neutron irradiations were carried out in the Kyoto University Reactor (KUR) and the Japan Material Testing Reactor (JMTR) reactors. After neutron irradiation up to 1 × 1020 n/cm2, the high-manganese steels and high silicon-manganese steels still showed high strength and good ductility.
Precipitation Sensitivity to Alloy Composition in Fe-Cr-Mn Austenitic Steels Developed for Reduced Activation for Fusion Application
Authors: Maziasz PJ , Klueh RL
Published: March 2009

Special austenitic steels are being designed in which alloying elements like molybdenum, niobium, and nickel are replaced with manganese, tungsten, vanadium, titanium, and/or tantalum to reduce the long-term radioactivity induced by fusion reactor irradiation. However, the new steels still need to have properties otherwise similar to commercial steels like Type 316. Precipitation strongly affects strength and radiation-resistance in austenitic steels during irradiation at 400 to 600°C, and precipitation is also usually quite sensitive to alloy composition. The initial stage of development was to define a base Fe-Cr-Mn-C composition that formed stable austenite after annealing and cold-working, and resisted recovery or excessive formation of coarse carbide and intermetallic phases during elevated temperature annealing. These studies produced a Fe-12Cr-20Mn-0.25C base alloy. The next stage was to add the minor alloying elements titanium, vanadium, phosphorous, and boron for more strength and radiation-resistance. One of the goals was to produce fine MC precipitation behavior similar to the Ti-modified Fe-Cr-Ni prime candidate alloy (PCA). Additions of Ti + V + P + B produced fine MC precipitation along network dislocations and recovery/re-crystallization resistance in 20% cold-worked material aged at 800° for 168 h, whereas tungsten, titanium, W + Ti, or Ti + P + B additions did not. Addition of W +Ti + V + P + B also produced fine MC, but caused some σ phase formation and more recrystallization as well. These new alloys, therefore, achieved several of the initial design goals. Their fine MC precipitation and recovery/recrystallization behavior during aging is similar to that of the PCA. Calculations show that the new steels have over 103 times less long-term radioactivity than Type 316.
EB Welding of Low-Activation Vanadium-Binary Alloys
Authors: Hiraoka Y , Noda T , Okada M
Published: March 2009

Tensile properties at 298 and 77 K of the electron-beam-welded joints of low neutron activation vanadium-binary alloys were evaluated. (1) Yield and tensile strengths of the welded specimens increased with an increase of carbon of up to 1.6%, boron of up to 5.0% and chromium of up to 9.3% by weight. (2) All the materials were embrittled by the welding, though the order of embrittlement depended on the additive and its content. The order of embrittlement was the least for vanadium-boron (V-B) alloys and the most for vanadium-chromium (V-Cr) alloys. (3) The location of fracture in the tensile specimens was in the weld metal for V-C and V-Cr alloys and the heat-affected zone (HAZ) for V-B alloys. Fracture mode depended on the additive and temperature. Most of the alloys at 298 K and V-B alloys at 77 K showed the ductile fracture, while V-C and V-Cr at 77 K showed the cleavage fracture.
Diffusion Bonding Between Vanadium and Alumina
Authors: Abe K , Okamura K , Kikuchi M
Published: March 2009

Joining with ceramic materials is one of the important subjects in the application of vanadium for the fusion environment. In order to develop and understand the solid-state bonding of vanadium with oxide ceramics, conditions of diffusion bonding between vanadium and alumina were examined, and fundamental properties of bonded couples were studied. As alumina has a linear thermal expansion coefficient relatively close to the value of vanadium, enough bond strength is expected between them.

Couples of vanadium and alumina disks with 8-mm diameter and 3-mm thickness were heat-treated in a vacuum of 1 × 10-3 Pa in the temperature range of 1673 to 1873 K under the compression of 2.8 to 14.6 MPa. Both single crystals and polycrystals of alumina and a polycrystalline vanadium were used. The degree of bonding depended on the temperature and stress. In the case of alumina single crystals, relaxation of residual stress could be accompanied with crack nucleation and also twin-like deformation.

Transmission electron microscopy and electron-probe X-ray microanalysis were performed in the region including the metal/ceramic interface. Both straight and curved interfaces were observed along with several orientation relationships across the interface. No intermediate phase was observed by transmission electron microscope (TEM) and electron probe micro-analysis (EPMA), nor was a hardened layer on the vanadium side near the interface observed by the micro Knoop indentation technique.

The maximum strength of bonded couples was determined to be 83 MPa for the polycrystalline alumina by means of a miniature three-point bend test. Scanning electron microscopy showed a relatively wavy fracture mode along the interface.

The bonding mechanism and the method to improve bond properties are discussed.
Anchor Connections of Stone Slabs
Authors: Amrhein JE , Hatch RH , Merrigan MW
Published: March 2009

This paper presents the results of testing anchorage systems of stone panels onto buildings. It includes various typical anchor systems for the two most common stone thicknesses and five different classes of stones. The anchor systems and their ultimate loads allow comparisons with code requirements and factors of safety.
The Potential for Traffic Noise Reduction by Thin Masonry Panels
Authors: Mehta ML
Published: March 2009

Heavy reinforced concrete and masonry walls are commonly used as protective barriers against highway noise. Recently, prefabricated thin brick wall panels have been proposed to isolate traffic noise from city streets and highways. This paper reviews the theoretical background on noise level reduction achieved by barriers erected on one side of the road and examines its application to thin masonry panels.
Corrosion Monitoring for Reinforcing Bars in Concrete
Authors: Matsuoka K , Kihira H , Ito S , Murata T
Published: March 2009

To monitor accurately the corrosion rate of rebars in a concrete structure using electrochemical techniques, the area of the rebar surface to be measured should be well specified by taking into account the wide-spreading distribution of the polarization current. For this purpose, the double-counter electrode method proposed by some investigators is projected to be one of the most accurate methods. However, there have been few actual studies on its accuracy. Therefore, the aim of this study is to establish the basis of accuracy for the double-counter electrode method, using numerical simulation by the two-dimensional finite element method. The obtained results indicate that the corrosion rate of rebars can be accurately monitored by the double-counter electrode methods, and that its accuracy is mainly affected by the degree of confinement of the longitudinal current distribution related to the concrete cover and the polarization resistance. Finally, a graphic method to correct the raw a-c impedance data obtained by the double-counter electrode method to arrive at the true impedance data is presented in this paper.
A PC-Based Data Acquisition System for Composite Material Fracture Testing
Authors: Colvin GE , Swanson SR
Published: March 2009

Automated data acquisition is a necessity for characterizing composite materials due to the nonlinearities associated with matrix-dominated properties and measurement of multiple strains. A low-cost data acquisition system based on a Zenith 286 PC-compatible computer has been developed for characterizing the mechanical response of composite materials subjected to a variety of loading arrangements. The system utilizes a Data Translation DT2821 card that provides 16 channels of analog-to-digital conversion. An inexpensive, low-noise strain gage conditioner and amplifier was built to provide ten conditioned DC output channels for strain gage measurements. A menu-driven software package, written in the C programming language, runs the system and creates an easy-to-use operator interface. The software allows the user to access standard test configurations, standard or customized data reduction routines, and port data to an Apple Macintosh. The results of an investigation measuring the resolution and accuracy of the system are reported. Data acquisition examples are presented for testing composite I-beams in three-point bending, composite cylinders under uniaxial compressive loads, and composite tubes under biaxial loading.
A Fracture Mechanics Test Automation System for a Basic Research Laboratory
Authors: Hartman GA , Ashbaugh NE
Published: March 2009

Successful selection of a material test automation strategy, hardware, and software depends on careful evaluation of the requirements of the target laboratory. Some of the criteria include the type of testing (single event, continuous), the laboratory mission (basic research, production testing, quality assurance), the operator's level of understanding of the testing and automation system, the available laboratory space, and the financial constraints. This paper discusses automation strategy, hardware, and software that have been used to automate a basic research laboratory performing fatigue crack propagation testing under a variety of test conditions including elevated temperatures.

A microcomputer and smart peripheral equipment are used as a hardware platform to perform real-time test control. The material analysis and test environment (MATE) software has been developed in-house to satisfy a broad range of current and future requirements. MATE is discussed in terms of its ability to meet the criteria set forth for the laboratory both for real-time automated test control and for quasi-real-time analysis of the data as the test proceeds. The software is designed to provide maximum flexibility as demanded by the basic research mission of the laboratory. The software presents a logical graphical operator interface to the user that is suitable for use by the technical and scientific staff.
Simulation of Mechanical and Environmental Conditions in Fatigue Crack Growth Testing
Authors: Solin J , Häyrynen J
Published: March 2009

This paper describes testing methods and solutions to problems that are faced in laboratory tests for simulation of realistic service conditions. The methods include fatigue crack growth tests in air and aqueous environments under constant amplitude and spectrum loading. Structural testing is also briefly discussed.
Automation Software for a Materials Testing Laboratory
Authors: McGaw MA , Bonacuse PJ
Published: March 2009

An overview of the software environment in use at the NASA-Lewis Research Center's High Temperature Fatigue and Structures Laboratory is presented. This environment is composed of varying interrelated software systems, of both a NASA-designed and a commercially available nature, all of which operate on a local, distributed, mini- and microcomputer system. The software environment is designed to support the tasks involved in performing materials behavior research, principally: defining and executing materials tests, analyzing the results of these experiments, and reporting the results. The approach taken in this application was to create a method of specifying a materials test that is independent of the terminologies and conventions of the intended applications. This approach results in a useful tool for performing a wide variety of tests. The features and capabilities of this approach to specifying a materials test include: static and dynamic control mode switching, enabling multimode test control; dynamic alteration of the control waveform based upon events occurring in the response variables; precise control over the nature of both command waveform generation and data acquisition (as it relates to the command waveform), including dynamically variable waveform types, data acquisition channel sets and sampling rates; and, the nesting of waveform/ data acquisition strategies so that material history dependencies may be explored. For all practical purposes, differing waveform and data acquisition strategies may be concatenated and nested indefinitely to provide extensive control over materials test control histories. Experimental capabilities currently supported in an automated fashion include both isothermal and thermomechanical fatigue and deformation testing capabilities. A secondary goal was to introduce efficiencies into the conventional research process by eliminating tedious and repetitive tasks, that is, to increase the amount of time the researcher spends on research. The latter goal was achieved through the establishment of a communications network software system that provides (among other things) file interchange and remote console capabilities, and through the introduction of a data analysis and archiving system.
Collection and Evaluation of Fatigue and Fracture Mechanics Data According to the European High Temperature Materials Databank (Petten) Standard
Authors: Over H-H , Buchmayr B
Published: March 2009

Well-organized material databanks present obvious advantages to material scientists as well as to designers. The capacity, efficiency, reliability, and acceptance of material databanks, among others, depend on the documentation of the data sources, the structure of the data, and the sophistication of the evaluation and assessment facilities.

The European High Temperature Materials Databank (HTM-DB) of the Joint Research Centre (CEC-JRC) Petten is organized in such a way that an optimum data storage enabling rational data collection and evaluation is achieved. In the area of high-temperature materials testing, where the material behavior (for example, lifetime of components) is strongly affected by the loading conditions and control parameters, the HTM-DB relates to this by defining the appropriate terms and fields. In this sense, it contributes to the standardization of automated testing technology.

In addition, the HTM-DB offers several well-defined standardized evaluation methods for the results of tensile, creep, relaxation, fatigue, creep-fatigue, creep crack, and fatigue crack growth testing at high temperatures. The results of these evaluation programs can be implemented for the design of components using finite element calculations or for material development tasks.
Use of Stone Columns to Improve the Structural Performance of Coal Waste Deposits
Authors: Davie JR , Young LW , Lewis MR , Swekosky FJ
Published: March 2009

The Gilberton Power Project, located in central Pennsylvania, makes use of waste anthracite coal, called culm, for fuel. The culm processing area is underlain by this culm, which is generally loose, and quite unsuitable to support the heavily-loaded processing equipment. Vibro-replacement stone columns were selected for ground modification. The stone columns were installed to various depths, depending on the size and loading of the structure. The paper describes the design and Installation of the vibro-replacement stone columns, difficulties encountered during installation and how these were overcome, and techniques used to confirm the effectiveness of the modified ground, including soil borings, plate load testing, and performance monitoring.