bluuebunny/crossref_metadata_2025 huggingface dataset:
Photoelectric Tristimulus Colorimetry
Authors: Hunter Richard S.
Published: September 2009

The possibility of using photocells to measure color has attracted widespread attention ever since the photoelectric cell became available in practical form. Photoelectric cells have now been used for a number of years in spectrophotometry to measure the spectral reflective and transmissive properties of materials. From the spectrophotometric curves of samples, one may obtain the tristimulus values of color by multiplying the separate spectral values of any sample by the three distribution functions of the standard observer and totaling the three sets of products throughout the visible spectrum (see Eq. 2, below, and (11, p. 365). Although the use of photocells has considerably diminished the time needed to obtain spectrophotometric curves, and although devices such as the one developed by Sears (19) are available to accelerate the integration, a considerable expenditure of time and effort is still required (13, p. 259) to obtain the accurate colorimetric specification of a sample by the method of spectrophotometry and integration.
Modeling the Formation and Growth of Cracks from Cold-Worked Holes
Authors: Fujimoto William T.
Published: September 2009

First generation crack formation and crack growth predictive approaches for cold-worked holes—based on the growth of a single noninteracting crack in a stationary residual stress field—fail to account fully for the physical mechanisms by which cracks form and grow from cold-worked holes. This filure leads in many cases to large differences between predicted and actual lives. Factors not accounted for in first generation approaches include the following: 1. 3-D nature of residual stress field due to mandrel pull-through. 2. Multistage crack growth involving a progressively spreading system of cracks. 3. Multiple potential initial crack sites, and the effect of site upon the multistage crack growth path. 4. Relaxation of the residual stress field due to overloads/underloads, or due to cyclic reyielding from crack growth. 5. Interaction of the hole with adjacent structural elements for multilayer joints. A physics-based second generation methodology for accounting for these factors is described. This methodology separates into individual building blocks each of the various mechanisms controlling the formation and relaxation of residual stresses, and the nucleation and progression of a system of cracks. Because it explicitly models each of these mechanisms, it is capable of eliminating or reducing the uncertainty over the life improvement potential of the cold-working process, allowing the full potential of cold-working to alleviate the aging aircraft problem to be untapped.
Thermal Residual Stress Relaxation in Powder Metal IN100 Superalloy
Authors: Buchanan Dennis J. , John Reji , Ashbaugh Noel E.
Published: September 2009

Relaxation of shot peen induced compressive residual stresses due to thermal exposure was measured using X-ray diffraction. The material used in this study was a hot isostatically pressed (HIP) powder metal (PM) IN100 nickel base superalloy. A total of 14 IN100 samples were shot peened to an Almen intensity of 6A using MI-170-R shot with 125 % coverage. The sample dimensions were nominally 16×13×4-mm thick with an irradiated X-ray region of 8×5 mm. Residual stress measurements were made at the surface and at nominal depths of 12, 25, 50, 75, 125, 175, 250, and 350 microns. The shot peened samples were thermal exposed at two temperatures (650, 704°C) and a range of exposure times (0.5–300 h). Residual stress measurements on shot peened samples without thermal exposure were used as a basis for comparison. The relaxation of shot peened compressive residual stresses under purely thermal loading was examined. The residual stresses exhibited an initial rapid decrease on the surface and in the depth at both temperatures. However, continued thermal exposure produced little or no change in surface residual stresses while peak compressive stresses in the depth continued to relax with time at both temperatures. In all cases of this study the retained peak compressive residual stress after thermal exposure was greater than 50 % of the baseline value.
Stress Intensity Factor Analysis and Fatigue Behavior of a Crack in the Residual Stress Field of Welding
Authors: Terada Hiroyuki
Published: September 2009

This paper deals with the behavior of a crack in the residual stress field induced by butt weld in a wide plate. It is known that the distribution pattern of residual stress is similar regardless of welding process, though the size and the magnitude of the residual stress depend largely on the welding process. Stress intensity factor and stress redistribution induced by the crack extension were calculated for a crack with arbitrary length and location. The stress redistributions caused by crack extension obtained by the present analysis showed good agreement with the experimental data. Fatigue crack propagation behavior in the residual stress field reported by Glinka was also examined from the ΔK point of view. In this paper, the effect of residual stress on the fatigue crack propagation rate is considered to be the effect of varying mean stress. The concept of ΔKeff, where the effect of residual stress is accounted as the correction factor by the way of simple superposition, is shown to predict the crack growth rate with sufficient accuracy.
Correlation Between Strength and Measured Residual Stress in Tempered Glass Products
Authors: Redner Alex S. , Mognato Ennio , Schiavonato Matteo
Published: September 2009

U.S. and European Standards for strength and residual stresses in tempered glass are reviewed. Experimentally established correlation between the strength and nondestructively measured residual surface stress is demonstrated.
Influence of Cold Rolling Threads Before or After Heat Treatment on High Strength Bolts for Different Fatigue Preload Conditions
Authors: Horn Nathan J. , Stephens Ralph I.
Published: September 2009

SI grade 12.9 high strength steel bolts were used to investigate the fatigue behavior of bolt threads rolled before/after heat treatment using two different thread profiles and two different high preload values. Bolts were 3/8 UNRC-16 (coarse) and 3/8 UNRF-24 (fine) and preloads were taken as 75 and 90 % of proof stress. Axial forces were applied through the nut. Axial and transverse residual stresses near the thread root were measured using X-ray diffraction. Most fracture surfaces contained crescent-shaped cracks and SEM evaluation indicated all fatigue crack growth regions contained multiple facets with no striations. Rolling after heat treatment caused little to no increase in fatigue resistance for the coarse threads. However, the fine threads finite fatigue life increased by factors of 2 to 5 and fatigue strengths based on Sa at 107 cycles increased by 40 and 50 % for the 90 and 75 % of proof stress preload, respectively. These are significant increases considering the very high preloads or Rratios. The greater preload gave better fatigue resistance when based on the maximum stress, Smax, and lower fatigue resistance when based on the alternating stress, Sa. Based on Smax, fatigue strengths at 107 cycles for 90 % of preload were equivalent to or greater than the actual proof stress. Smax at 107 cycles for fine threads rolled after heat treatment with 75 % of proof stress was also greater than the actual proof stress. The above results can be attributed to different thread root radii, thread region smoothness, original residual stress from rolling after heat treatment, and residual stress relaxation from the high preloads.
Residual Stress Measurements in Welded and Plastically Deformed Target Structural Materials
Authors: Roy Ajit K. , Venkatesh Anand , Dronavalli Satish , Marthandam Vikram , Wells Douglas , Selim Farida , Rogge Ronald
Published: September 2009

Transmutation of spent nuclear fuels (SNF) is currently being considered to transform long-lived isotopes to species with relatively short half-lives and reduced radioactivity through capture and decay of minor actinides and fission products. This process is intended for geologic disposal of SNF for shorter durations in the proposed repository at the Yucca Mountain site. The structural material (Type 304L stainless steel/Alloy EP-823) surrounding the transmutation target will be subjected to welding operation and plastic deformation during fabrication, which could induce residual stresses in it. Destructive ring-core, and nondestructive x-ray diffraction, neutron diffraction, and positron annihilation spectroscopic techniques were used to evaluate residual stresses in welded and cold-worked specimens of both materials. The results indicate that, in general, for a welded specimen consisting of Alloy EP-823 and Type 304L stainless steel on opposite sides, compressive and tensile residual stresses were observed in the former and latter materials, respectively. However, a welded specimen consisting of only Alloy EP-823 on both sides showed tensile residual stresses. The extent of residual stresses in cold-worked specimens was enhanced with increased level of cold-reduction. In case of a bent specimen, compressive and tensile residual stresses were noticed in the convex and concave sides, respectively.
Full-scale Flexural Strength Testing for Stone Cladding Design
Authors: Naggatz Steven G. , Gerns Edward A.
Published: September 2009

Beginning with the Industrial Revolution and rapidly increasing following World War II, building cladding systems changed dramatically. Exterior wall construction that had previously consisted of thick mass masonry evolved into contemporary curtain wall systems. As curtain wall systems evolved, the economics of reducing the thickness of curtain wall components became more important. The use of thin stone veneers on buildings in the modern era was not associated with increased knowledge of stone material properties based on testing and research. Rather, the reduction in thickness is attributable to advancements in fabrication technology, economy in construction, and a rational approach to design of veneer systems. This paper will discuss the evolution of the use of stone in curtain wall systems and the associated ASTM standards for building stone. Early ASTM standards for building stone were limited to tests used to evaluate the compression strength of stone which was consistent for mass bearing walls of the early 20th century. As stone was increasingly used more as a veneer, standards for modulus of rupture (ASTM C 99) were introduced. As systems continued to evolve, flexural strength (ASTM C 880) was introduced to address material variability. The evolution of ASTM C 880 included increasing specimen width to further incorporate variability of the stone. Recently, the authors have introduced full panel testing in the design and evaluation process. This paper will present data and discuss the differences in test results for three case studies where both ASTM C 880 specimens and full panel flexural strength testing was performed. The focus of this section will be to discuss the implications of performing full-size panel testing in addition to ASTM C 880 standard specimen testing on design of stone cladding systems for tall building construction as a natural evolution of the design and evaluation process for thin stone cladding systems.
Testing of Composite Stone Faced Aluminum Honeycomb Panels
Authors: Scheffler Michael J. , Kneezel Daren S.
Published: September 2009

Physical and mechanical testing was conducted on composite stone faced aluminum honeycomb panels manufactured in the United States for use as exterior veneer panels on buildings. Testing was conducted on specimens cut from new stone faced panels as well as stone faced panels removed from service. For comparison purposes specimens cut from new unfaced honeycomb panels were also tested. The purpose of the testing was to measure certain strength, durability, and performance characteristics of the faced honeycomb panel's composite construction. The stone faced specimens tested included those faced with travertine, limestone, and granite. Old travertine faced specimens had been in service for more than 18 years. The results very strongly suggest that the structural performance of the composite panel is dominated by the aluminum honeycomb portion. The stone portion is essentially a thin veneer adhered to the honeycomb that provides little if any structural strength.
Paving Design: Is Rigid-Fix External Stone Paving the Way to Go?
Authors: Hensel Hans-Dieter
Published: September 2009

Recent investigations into a number of paving failures in Australia have shown that very little is understood about the many aspects intrinsic to rigid-fix (stuck down) paving. This paper examines and documents some of the factors that can determine the success or failure of paving (assuming a high standard of workmanship). Additionally, it has become clear that most engineers who investigate paving failures fail to fully understand the complexities and interplay of the many factors. Such lack of knowledge leads to poor design, poor supervision, and ultimately poor performance. There are basically three types of paving systems—adhesive/mortar fix, sand-bedded, and setts/cobblestones in a soft mortar. All three systems are being used in Australia but there is undoubtedly an overriding rigid-fixing mentality. By fixing stone to a solid concrete base so that it cannot move is probably seen by most engineers and architects as the most straight-forward and most controllable solution. However, on analysis, it is a system that is subject to numerous potential lines of failure. Not only is there the nature of the stone itself such as the mineral composition, strengths, thermal characteristics, and porosity, but also the environment into which it is placed, the types of loading it is subject to, and how it is fixed. Stability of the base (including shrinkage), expansion/construction joints, size, thickness and shape of the pavers, the laying pattern, type of adhesive, thermal conditions at the time of fixing, influence of salts and water, and sealing, all play a significant role in determining the success or otherwise of rigid-fix paving.
Stiffness Considerations in Dimension Stone Anchorage Design
Authors: Conroy Kevin , Hoigard Kurt R.
Published: September 2009

Modern building facade design concepts consider all cladding materials, including dimension stone cladding, as nonstructural elements designed to transmit localized gravity and lateral loads to the primary building structural elements. In practice, the structural backup behind dimension stone cladding can take a wide variety of forms, including cast-in-place concrete shear walls, brick and concrete masonry units, aluminum curtain wall system framing, hot and cold rolled steel subframes, and precast concrete panels and members. The flexural stiffness of these backup systems can vary widely, with cast-in-place concrete shear walls on one end of the stiffness spectrum and aluminum curtain framing on the other. The stiffness of dimension stone cladding relative to the backup system can have a significant effect both on the stresses induced in the cladding and the loads transmitted through the cladding anchors. Likewise, the stiffness of the anchor elements and the backup system can affect the loading and stress distribution within the cladding panels. This paper addresses some of the issues associated with the interaction of dimension stone cladding panels, panel anchors, and metal backup structures, and the effects of relative stiffness on load and stress distributions. Information is presented that was obtained from laboratory tests and analyses for new designs, as well as investigations of dimension stone cladding failures.
Characteristics That Affect the Integrity of Existing Thin Stone Cladding
Authors: Lewis Michael D.
Published: September 2009

Prestigious structures began using thin natural stone panels as wall cladding to give them historic character in the late 1960s. Easier fabrication methods increased stone production and enabled larger, thinner panels that were lightweight. Unfortunately, engineering and testing did not keep pace. Inadequate initial evaluation of material durability and panel strength resulted in varying degrees of distress developing in some claddings. Because early stone cladding was installed with little structural analysis, current evaluation should predict capability by checking characteristics initial engineering likely ignored. Comprehending all characteristics that affect the integrity of thin stone cladding must be the objective of a responsible maintenance program. The program must evolve with each evaluation's findings to adapt to the specifics of that building and its changes over time. Maintaining the safety of a building's skin is essential to extending the service life of the whole structure. Verifying safety requires more than a cursory visual check for exposed elements to find them before they fall. In the past, stone cladding was completely removed from too many structures that experienced distress. Some evaluations misunderstood or misdiagnosed affect of distress on integrity. They failed to investigate some characteristics, or did not relate others, yielding an incomplete assessment. Adding evaluation of characteristics common to traditional structural assessment to a cladding program adds rigor and objectivity, avoiding misdiagnosis and unjustified expense. In rare cases, remove-and-replace-all may still be required, but only if gross problems exist with support. However, in most cases, an appropriate program will not only identify the parts creating the highest risk, but the program can prescribe selective replacement instead of complete recladding as a long-term remedy.
Travertine: Successful and Unsuccessful Performance, Preconceived Notions, and Mischaracterizations
Authors: Chin Ian R.
Published: September 2009

Travertine is a beige-colored stone with unique color variations, veining, and cavities that many architects worldwide find attractive. The word travertine was derived from an old Roman name for the town of Tivoli (Tibur) in Italy where large deposits of travertine exist. The ancient name for the stone was Lapis Tiburtinus (Tibur Stone) which later evolved into the word travertine.Travertine is a sedimentary rock that began as limestone. Underground water heated by the earth's core dissolved the limestone and brought it along with other minerals to the earth's surface to form mud beds. In time, these mud beds of limestone and other minerals cooled and crystallized into solid travertine. This cooling process caused the small unique cavities and open channels in travertine to develop and the minerals created the unique color variations and veining in travertine.Travertine has been successfully used in buildings for thousands of years. The Coliseum in Rome is among the larger buildings in the world that was constructed largely with travertine. However, the inherent small cavities, open channels, and veining in the stone that many architects find attractive are viewed by some people as cavities where water can collect and potentially cause deterioration of the stone due to freezing of this water. This preconceived notion has led to avoidance of the use of travertine in some buildings. While this condition has locally occurred with certain uses of travertine, it has not occurred on a systematic scale, and properly designed, constructed, and maintained travertine elements on buildings have performed successfully.Travertine is a form of limestone and is sometimes classified as travertine limestone because it is composed principally of calcium carbonate. However, sometimes it is commercially classified as travertine marble because it can be polished. This commercial classification of travertine as marble has sometimes led to confusion in the design of travertine on buildings because geologically travertine is a form of limestone and is not marble.This paper describes the successful and unsuccessful uses of travertine on buildings, and provides guidance on how to successfully design travertine on buildings. This paper also provides information that will help to clear up the preconceived notions and mischaracterizations of travertine.
Durability of Marble Cladding—A Comprehensive Literature Review
Authors: Grelk B. , Christiansen C. , Schouenborg B. , Malaga K.
Published: September 2009

Natural stone has been used for centuries as building material. In historical time it was mainly used as load bearing elements, but within the past 50 years a new processing technique has made it commercially feasible to produce and use thin façade cladding. Unfortunately, a number of marble facades on buildings in both Europe and elsewhere have had serious problems with deterioration of the stone material. The TEAM (TEAM = TEsting and Assessment of Marble and limestone) project consortium represents nine European countries and comprises 16 partners, representing stone producers and trade associations, testing laboratories, standardization and certificate bodies, consultants, building owners and caretakers and producers of fixing and repair systems. The project had a budget of approximately 5 million dollars and was partly funded by the European Commission under the contract no. G5RD-CT-2000-00233. Two of the main objectives in the TEAM project were: — To understand and explain the mechanisms of the expansion, bowing, and loss of strength leading to degradation of marble and limestone clad facades. — To prevent the use of deleterious marble and limestone by introducing a draft for new European standards. This paper presents some of the important conclusions drawn from a literature review carried out within the TEAM project—and was based on an extensive review of literature on marble and limestone deterioration dating from the late 1800s to 2006 and the results of the TEAM project. The comprehensive information from more than 70 selected literature references is reviewed and discussed in order to describe the present knowledge on the causes and mechanisms responsible for the bowing and strength loss of thin marble cladding. In the following, the literature and TEAM findings are grouped under a number of headings proposed to explain observations. Thus, the information from the literature is compared and supplemented with the results from the TEAM project in order to present a good overview of the existing, most relevant, knowledge in the field. The literature review reveals that only few researchers have examined the durability problem from a broad perspective. In addition, no conclusive answer about the mechanisms and influencing factors can be given. The TEAM project has made it possible to identify several of the key influencing factors in marble degradation, the relative importance of various factors, and to gain a deeper understanding of the mechanisms involved.
Comparison of Field Testing with Laboratory Testing of the Durability of Stone
Authors: Bortz S. A. , Powers Laura , Wonneberger Bernhard
Published: September 2009

Samples of three granites (Texas Pink, Mount Airy White, Academy Black), one marble (Carrara) and Indiana Limestone have been exposed to 11 years of natural weathering on the roof of a building in the Chicago area. Twice a year, the samples are visually reviewed. In addition, the changes in physical properties have been monitored using non-destructive test procedures for determination of the dynamic (sonic) modulus of elasticity. The sonic modulus measurements were recorded using procedures as outlined in ASTM C 215, “Standard Test Method for Fundamental Transverse, Longitudinal, and Torsional Frequencies of Concrete Specimens.” The sonic modulus measurements were compared to measurements of similar stone samples that were exposed to laboratory accelerated weathering testing. The exposed and protected surfaces have recently been examined petrographically, and the changes due to the natural weathering recorded. Based on this additional testing and evaluation, conclusions can be drawn which further indicate the use of accelerated weathering. Testing can effectively evaluate the long-term changes in the mechanical and physical properties of dimension stone when exposed to natural weathering.
Water Vapor Transmission Measurement and Significance of Corrections
Authors: Mukhopadhyaya Phalguni , Kumaran Kumar , Lackey John , van Reenen David
Published: September 2009

Water vapor transmission properties of building materials play an important role in the overall moisture management and durability of the exterior building envelopes. The cup method, as described in the ASTM Standard Test Methods for Water Vapor Transmission of Materials (E 96), is widely used in North America and other parts of the world for this purpose. Recently the latest ASTM standard (E 96/E 96M-05) has started taking into account various corrections (e.g., buoyancy correction, correction for resistance due to still air and specimen surface, edge mask correction, etc.) while analyzing the results obtained from the cup methods. This paper presents the results obtained from the laboratory tests carried out on more than 50 building materials. These results have been used to demonstrate the significance of various corrections on the measured water vapor permeability or permeance of various commonly used building materials or components. The results presented in this paper were discussed in the ASTM technical task group to underline the importance of various corrections for the calculation of water vapor transmission properties of various building materials.
The Statistical Nature of the Fatigue Properties of SAE 4340 Steel Forgings
Authors: Ransom J. T. , Mehl R. F.
Published: September 2009

The statistical nature of the fatigue properties of SAE 4340 gun tubes was investigated as a part of a systematic study of the mechanical properties of forging steels. Both high and low quality forgings (quality determined by transverse tensile reduction of area) of the same tensile strength level were studied. Specimens were taken in the longitudinal and transverse directions. Procedures were used to permit statistical analysis of the variability of the endurance limit and life to failure.

The variability of the fatigue properties of even high quality forgings was found to be greater than is generally estimated from the results of conventional non-statistical testing programs. This was especially true of the endurance limit. The variability of properties in the transverse direction of the low quality forgings was significantly greater than the variability of properties in the longitudinal direction of low quality forgings or in either direction of high quality forgings. The variability was greatest at stresses near the endurance limit. The variation in life to failure resulting from the variation in several experimental factors, that is, testing machine, eccentricity of rotation, stress relief, fracture criterion, stress calculation, and position of specimen in the forging, was shown to be insignificant. It was concluded that the variability in fatigue properties is an inherent characteristic of this property in this material and cannot be ignored if significant answers are to be obtained.
The Statistical Behavior of Fatigue Properties and the Influence of Metallurgical Factors
Authors: Epremian E. , Mehl R. F.
Published: September 2009

It is now well established that the fatigue properties of metals are statistical in nature. Earlier work showed that the fatigue life is variable, and very recently it was shown for the first time that the endurance limit is statistical. Since both the fatigue life and endurance limit are subject to marked variability, these quantities cannot be stated as single values, but must be represented statistically. This fact is of scientific interest as well as practical importance. In the design of parts for service in applications which involve cyclic stresses, the engineer must, in choosing a proper factor of safety, recognize the fact that some failures can occur prematurely or even at stresses below the normally determined endurance limit. In the field of research, many of the long accepted conclusions drawn from the usual investigations can be questioned since the statistical approach, now known to be necessary, was not used.

While the statistical nature of fatigue properties has been established, the influence of metallurgical factors on this behavior has not been known. The dependence of fatigue variability on such factors as composition, microstructure, hardness, and inclusion rating has not been evaluated, and it was toward this objective that considerable experimental work was directed.

The statistics of the fracture curve and endurance limit were obtained for a variety of materials, and analysis and comparison of the results by statistical methods indicated the influence of the metallurgical variables on the statistical behavior.
Master Integrated Reactor Vessel Surveillance Program
Authors: Hall J. Brian , Spond Dan F.
Published: September 2009

The B&W Owners Group Master Integrated Reactor Vessel Surveillance Program (MIRVP) was initiated in 1977 for the B&W 177 fuel assembly (FA) plants. Its purpose was to augment the existing reactor vessel surveillance programs and provide a basis for sharing information between plants. All of the early vintage B&W-manufactured reactor vessels were fabricated using the submerged arc welding process and particular consumables, which resulted in welds that are sensitive to fast-neutron exposures. The welds in these vintage B&W-manufactured reactor vessels are referred to as the Linde 80 class of materials. In 1988, the MIRVP was further modified to include a series of plants with the Westinghouse Nuclear Steam Supply System for which B&W manufactured the reactor vessels. These vessels have virtually identical welds as those used in the B&W 177 FA plants. The overall objective of the MIRVP is to provide the data necessary to ensure compliance with U.S. Federal Regulations. With the extension of operating licenses to 60 years for many of the member plants, the program was re-evaluated to ensure that data will be available for 60 and 80 years of operation. Projected reactor vessel fluence levels at 60 and 80 years were compared to available data and projected irradiations of the surveillance capsules that continue to be irradiated. This paper presents an overview of the MIRVP, data evaluation, results, and the withdrawal schedule adjustments. The program has adequate surveillance capsules to meet the irradiation needs of the participating plants for 80 years; however, the planned withdrawal schedule has been adjusted.
Monitoring of Radiation Embrittlement of the First and Second Generation of VVER RPV Steels
Authors: Shtrombakh Ya. I. , Nikolaev Yu. A.
Published: September 2009

The analysis of the current condition on the prediction of radiation embrittlement for VVER RPV materials of the first and second generation has been carried out. The radiation lifetime of a definite type of pressure vessel is determined by various parameters caused by operational features and the chemical composition of pressure vessel's metal. The emphasis on re-irradiation embrittlement kinetics is given for the first generation of VVER RPV steels (VVER-440/179 and VVER-440/230 grades). The technique for the first generation RPV materials monitoring, based on sampling and studies of metal from the pressure vessel's inner surface, is considered. The current program of cutting out templates, for the inner surface of a RPV wall, and their re-irradiation in surveillance channels of VVER-440 units with full core and dummy assembles is described. The new approaches to re-irradiation embrittlement models are analyzed. The basic problems of VVER-440/213 and VVER-1000 metal monitoring are analyzed. The representativity of VVER-440/213 and VVER-1000 RPV surveillance programs is discussed. The necessity of updating of the current standard reference dependences for the prediction of radiation embrittlement of RPV materials is shown. The most urgent questions of reactor dosimetry for VVER pressure vessel materials have been covered. The lifetime extension problem for the first and second generation of VVER units is considered.
Radiation Embrittlement of Cr-Ni-Mo and Cr-Mo RPV Steels
Authors: Nikolaev Yu. A.
Published: September 2009

Radiation embrittlement kinetics of Cr-Mo and Cr-Ni-Mo steels, used for manufacturing VVER-440 and VVER-1000 RPV steels, respectively, are under consideration. Radiation embrittlement of VVER-440 and VVER-1000 RPV steels exposed to irradiation for 17–22 years is analyzed. Extremely high levels of thermal aging of VVER-1000 RPV steels at 320°C is pointed out. The neutron flux effect problem and the problem of accelerated radiation embrittlement of welds with high nickel contents are emphasized. The effect of phosphorus, copper, silicon, manganese, and nickel contents on radiation embrittlement of VVER-440 and VVER-1000 RPV steels is studied using the Russian surveillance database and representative results of research programs. The trend curves for VVER-440 and VVER-1000 RPV steels are proposed. The mechanisms of radiation embrittlement of Cr-Ni-Mo and Cr-Mo RPV steels are supposed.
Phosphorus Segregation and Intergranular Embrittlement in Thermally Aged and Neutron Irradiated Reactor Pressure Vessel Steels
Authors: Nishiyama Yutaka , Onizawa Kunio , Suzuki Masahide
Published: September 2009

A study on phosphorus (P) segregation at grain boundaries and intergranular embrittlement of reactor pressure vessel steels due to thermal aging and neutron irradiation has been performed for A533B steel plates and weld metals doped with different bulk levels of P. The initial P concentration at grain boundaries of these materials determined by scanning Auger microscopy ranged from 9 to 33 %. The materials thermally aged at temperatures ranging from 450 to 550°C for up to 10000 h exhibited increases in P concentration described by the McLean's equation. A linear correlation was obtained between P concentration and Charpy 41 J transition temperature (T41J). Fracture toughness tests in the ductile-tobrittle transition temperature region have been conducted by the Master Curve method using 1T-CT specimens. The material subject to intergranular embrittlement exhibited the dual fracture toughness distributions typically observed in inhomogeneous materials. This was probably due to two types of initiation of cleavage and intergranular fracture. The lower tail analysis based on the Master Curve method enabled conservative fracture toughness estimates by fitting the lower fracture toughness arising from intergranular fracture. The relation between median KJc values estimated from the lower tail analysis and temperature appeared to follow the Master Curve. For neutron irradiated materials up to a fluence of 6.9×1019 n/cm2 (E>1 MeV) at 290°C by the Japan Materials Testing Reactor, an increase in grain boundary P segregation associated with decrease in carbon segregation was observed with increasing fluence. Relative significant hardening was recognized for the material with high bulk P content. Shifts in the reference temperature T0 and T41J were comparable for the thermally aged and irradiated materials.
Strain Hardening During Mechanical Twinning and Dislocation Channeling in Irradiated 316 Stainless Steels
Authors: Byun T. S. , Hashimoto N.
Published: September 2009

Localized deformation mechanisms and strain-hardening behaviors in irradiated 316 and 316LN stainless steels were investigated, and a theoretical model was proposed to explain the linear strain-hardening behavior during the localized deformation. After low temperature irradiation to significant doses, the deformation microstructure changed from dislocation tangles to channels or mechanical twins. It was also observed that irradiation hardening straightened gliding dislocations and increased the tendency for forming pileups. Regardless of these microstructural changes, the strain-hardening behavior was relatively insensitive to the irradiation. This dose-independent strain-hardening rate resulted in dose independence of the true stress parameters, such as the plastic instability stress and true fracture stress. In the proposed model, the long-range back stress was formulated as a function of the number of pileup dislocations per slip band and the number of slip bands in a grain. The calculation results confirmed the experimental observation that strain-hardening rate was insensitive to the change in deformation mechanism because the long-range back stress hardening became as high as the hardening by tangled dislocations.
Notch Strengthening and Its Impact on the Deformation and Fracture of 316L Stainless Steel
Authors: Wu Xianglin , Pan Xiao , Stubbins James F.
Published: September 2009

316L stainless steel has been widely used for structural component applications in irradiation environments. The impact of manufacturing or service-induced defects on material tensile response and fracture behavior has been a longstanding concern. In this study, electron backscattering diffraction and finite element methods have been utilized to examine and model the tensile response of 316L stainless steel with different notch geometries. The tensile response is influenced by twinning at room temperature, while it is completely absent at temperatures higher than 200°C. In addition, irradiation exposure increases the yield point of the material and reduces the ductility. It is found that the larger plastic deformation area and severe tip blunting in ductile, unirradiated material promote uniformly distributed post-yield strain hardening processes. In this case, fracture initiates internally for tensile and C-notched specimen geometries, but from the notch tip for sharp V-notched specimen geometries. When irradiation-induced hardening is considered, similar fracture modes are found, however, strains to fracture are significantly reduced.
Irradiation Hardening and Microstructure Evolution of Ion-irradiated ODS Ferritic Steels
Authors: Yutani Kentaro , Kasada Ryuta , Kishimoto Hirotatsu , Kimura Akihiko
Published: September 2009

Irradiation hardening and microstructural change of oxide dispersion strengthened (ODS) ferritic steels were investigated by using the ion-irradiation technique. The material used for the present study was K3 (16C-2W-0.3Ti-4.6Al-0.4Y2O3) ODS ferritic steel for the application to Generation IV concept advanced reactors and fusion reactors. 6.4 MeV Fe3+ ions were used to irradiate to the K3 ODS steel by using a 1.7 MeV tandem accelerator. The irradiation temperatures were 300°C and 500°C. The nominal displacement damage rate and total displacement damage were 1×10−3 dpa/s and up to 10 dpa at about 600-nm depth from the irradiated surface, respectively. Nano-indentation hardness was evaluated with a Berkovich indenter. After the ion-irradiation at 300°C up to 1 dpa, the normalized nano-indentation hardness (hardness after irradiation/hardness before irradiation) of the K3 ODS steel reached about 1.28 and the value showed no change up to 10 dpa. On the other hand, the ion-irradiation at 500°C up to 10 dpa showed no significant irradiation hardening. TEM observation revealed that dense and fine dislocation loops were formed in the ion-irradiated steels at 300°C, which were probably enough to explain the irradiation hardening.
Modelling of Radiation Damage in Fe-Cr Alloys
Authors: Malerba L. , Terentyev D. A. , Bonny G. , Barashev A. V. , Bjorkas C. , Juslin N. , Nordlund K. , Domain C. , Olsson P. , Sandberg N. , Wallenius J.
Published: September 2009

High-Cr ferritic/martensitic steels are being considered as structural materials for a large number of future nuclear applications, from fusion to accelerator-driven systems and GenIV reactors. Fe-Cr alloys can be used as model materials to investigate some of the mechanisms governing their microstructure evolution under irradiation and its correlation to changes in their macroscopic properties. Focusing on these alloys, we show an example of how the integration of computer simulation and theoretical models can provide keys for the interpretation of a host of relevant experimental observations. In particular we show that proper accounting for two basic features of these alloys, namely, the existence of a fairly strong attractive interaction between self-interstitials and Cr atoms and of a mixing enthalpy that changes sign from negative to positive around 8 to 10 % Cr, is a necessary and, to a certain extent, sufficient condition to rationalize and understand their behavior under irradiation. These features have been revealed by ab initio calculations, are supported by experimental evidence, and have been adequately transferred into advanced empirical interatomic potentials, which have been and are being used for the simulation of damage production, defect behavior, and phase transformation in these alloys. The results of the simulations have been and are being used to parameterize models capable of extending the description of radiation effects to scales beyond the reach of molecular dynamics. The present paper intends to highlight the most important achievements and results of this research activity.
Kinetics of the Migration and Clustering of Extrinsic Gas in bcc Metals
Authors: Deo C. S. , Srinivasan S. G. , Baskes M. I. , Maloy S. A. , James M. R. , Okuniewski M. , Stubbins J.
Published: September 2009

We study the mechanisms by which gas atoms such as helium and hydrogen diffuse and interact with other defects in bcc metals and investigate the effect of these mechanisms on the nucleation of embryonic gas bubbles. Large quantities of helium and hydrogen are produced due to spallation and transmutation in structural materials in fusion and accelerator-driven reactors. The long time evolution of the extrinsic gas atoms and their accumulation at vacancies is studied using a kinetic Monte Carlo algorithm that is parameterized by the migration energies of the point defect entities. First-order reaction kinetics are observed when gas clusters with vacancies. If gas-gas clustering is allowed, mixed-order diffusion limited kinetics are observed. When dissociation of gas from clusters is allowed, gas-vacancy clusters survive to steady state while gas-gas clusters dissolve. We obtain cluster size distributions and reaction rate constants that can be used to quantify microstructural evolution of the irradiated metal.
Modeling the Interaction of Helium with Dislocations and Grain Boundaries in Alpha-Iron
Authors: Heinisch H. L. , Gao F. , Kurtz R. J.
Published: September 2009

Helium is a ubiquitous impurity in nuclear materials that can have significant deleterious effects on mechanical properties, including deformation and fracture. To determine ways to mitigate the effects of helium it is necessary to understand the behavior of helium with respect to its interaction with various microstructural features. Toward that end, we have employed molecular statics, molecular dynamics, and the dimer method of potential surface mapping to study the fate of helium in the vicinity of dislocations and grain boundaries in alpha-iron. Even at very low temperatures interstitial helium atoms can migrate to dislocations and grain boundaries, where they are strongly bound. The binding energies of helium to these microstructural features relative to the perfect crystal and the migration energies of helium diffusing within them have a strong correlation to the excess atomic volume that exists in these extended defects. Helium atom migration energies within the dislocations and grain boundaries studied are in the range of 0.4–0.5 eV. Helium “kick out” mechanisms have been identified within dislocations and grain boundaries by which interstitial helium atoms replace an Fe lattice atom, creating a stable He-vacancy complex that may be a nucleation site for an He bubble.
DD Simulations of Dislocation-Crack Interaction During Fatigue
Authors: Mastorakos I. N. , Zbib H. M.
Published: September 2009

The effect of different shaped cracks on fatigue behavior in metals is investigated with the help of the discrete dislocation dynamics (DD) technique. The cracks are represented as distributions of infinitesimal dislocation loops. The distribution is determined by an integral equation satisfying stress-free boundary conditions and containing a singular kernel of the third type. The stress field in the cracked domain is calculated using a superposition principle. The derived stress field describes the interaction between the crack and the dislocations into the framework of dislocation dynamics. The simulation results provide an insight on the three-dimensional character of the dislocation structure around the crack tip and its relation to the crack shape and number of cycles. The effect of the crack on the macroscopic yield stress is also computed for various crack sizes and shapes.
Grain Growth in Nanocrystalline Metal Thin Films under In Situ Ion-Beam Irradiation
Authors: Kaoumi D. , Motta A. T. , Birtcher R. C.
Published: September 2009

In-situ observations in a transmission electron microscope (TEM) were used to study the microstructure evolution in metal Zr, Pt, Cu, and Au nanocrystalline thin films under ion-beam irradiation. Free-standing films were prepared by sputter deposition. Samples were irradiated in-situ at the Intermediate Voltage Electron Microscope (IVEM) at Argonne National Laboratory with Ar and Kr ions to fluences in excess of 1016 ion/cm2. As a result of irradiation, grain growth was observed in all samples using Bright Field (BF) imaging in the TEM. The average grain size increased monotonically with ion fluence until it reached a saturation value. Similarly to thermal grain growth, the ion-irradiation induced grain growth curves could be best fitted with curves of the type: Dn−;D0n=KΦ. The irradiations were done at temperatures ranging from 20 to 773 K. The results suggest the existence of three regimes with respect to irradiating temperature: (i) a purely thermal regime, which appears to start above the bulk coarse-grained recrystallization temperature, (ii) a thermally assisted regime where thermal diffusion and irradiation effects combine to increase the rate of grain growth relative to that resulting from either of these mechanisms alone, and (iii) an athermal regime (low-temperature regime) where irradiation can by itself cause grain growth. The transition temperature between the athermal regime and the thermally assisted regime depends on the material, but is in the range 0.14–0.22 times the melting point. The influence of the ion type was also investigated on Zr-Fe irradiated with 600 keV Kr ions versus 600 keV Ar ions.
Strategies for Control of Horseweed (Conyza canadensis) and Other Winter Annual Weeds in No-Till Corn
Authors: Armel Gregory R. , Richardson Robert J. , Wilson Henry P. , Hines Thomas E.
Published: September 2009

Field studies were conducted to determine if mesotrione alone or in combinations with other corn herbicides would control horseweed and other winter annual weeds associated with no-till corn. Mesotrione alone controlled horseweed 52 to 80% by 3 wk after treatment (WAT); however, by 7 WAT control diminished to between 37 to 68%, depending on mesotrione rate. Mesotrione at 0.16 kg ai/ha plus atrazine at 0.28 kg ai/ha controlled 99% of horseweed and annual bluegrass and 88% of yellow woodsorrel. Combinations of mesotrione at 0.16 kg/ha plus acetochlor at 1.79 kg ai/ha plus 1.12 kg ai/ha glyphosate (trimethylsulfonium salt of glyphosate) or 0.7 kg ai/ha paraquat provided 93% or greater control of all three weed species. Glyphosate alone also controlled all weed species 97 to 99%, while paraquat alone provided 99% control of annual bluegrass, 72% control of horseweed, and 36% control of yellow woodsorrel. Mixtures of paraquat plus acetochlor improved control of horseweed (93%) and yellow woodsorrel (73%) over control with either herbicide applied alone.