bluuebunny/crossref_metadata_2025 huggingface dataset:
An Examination of Interactions Between Various Dispersants and Other Surfactants in Wettable Powder Formulations
Authors: Butler BJ , Miller DJ , Sowa C , Zerrer R
Published: April 2008

The purpose of this study was to identify combinations of dispersants and wetting agents that may show broad utility in dry flowable formulations. The study tested four types of dispersants in combination with six types of wetting agents. Wettable powder formulations using four different active ingredients were made with either kaolin clay or silica as a diluent. Each test formulation was evaluated for suspensibility at 1 and 2 hours, with promising surfactant and diluent combinations being chosen based on maximum suspensibility as a function of time. Surface tension data for the surfactant combinations are also presented.

The study demonstrated that diluent selection is important and influences the surfactant combination needed for adequate suspensibility. The study also revealed that certain combinations of surfactants show broad functionality. There was considerable variability in terms of surfactant requirements for adequate suspensibility as a function of the active ingredient, with some actives showing suitable suspensibility with a wide range or very narrow set of surfactant combinations.
2,4-D Salts and Adjuvants-Review and Perspectives
Authors: de Ruiter H
Published: April 2008

The herbicide 2,4-D is an important herbicide at a global level. In 1999, the herbicide was ranked as the fifth herbicide in the United States regarding sales. The 2,4-D amine salts are generally not applied in combination with adjuvants. An effective and inexpensive adjuvant, either as built-in or as tank-mix adjuvant, can create a new product with benefits for the user and the environment. Such a product can be an alternative for the 2,4-D esters requiring emulsion-type formulations. The objective of this study is to investigate whether a review of published data, insight in the adjuvant-action and knowledge of the weed species may result in a list of adjuvant types being effective for 2,4-D amine salts. The lipophilicity of the 2,4-D molecule depends on the pH-dependent dissociation of the carboxylic group. Both hydrophilic and lipophilic adjuvants can be effective for 2,4-D amine salts. It will be discussed in how far this is related to the pH- dependent ionic character of 2,4-D. Ion-pair formation by association of the 2,4-D anion with a cationic counter ion as a tool for improving herbicide performance will be discussed. Calcium ions in the water used as carrier may reduce the performance of 2,4-D. It will be discussed in how far adjuvants may overcome this antagonistic effect of calcium.
Ready-to-use Aqueous Formulations and Concentrates for Strobilurin Class of Fungicides
Authors: Beestman GB , Narayanan K , Jon D
Published: April 2008

Water-based Ready-to-use formulations and concentrates were developed for a commercial fungicide. A systematic screening approach was used to develop the formulations. Control of crystal growth and chemical stability of the fungicide were primary challenges. The concentrate consists of an optimized combination of pyrrolidone copolymers, water-insoluble or sparingly water-soluble cosolvent, and anionic emulsifiers. A rationale for the unique Ready-to-use compositions will be provided. The formulations were successfully applied to the strobilurin fungicides Kresoxin-methyl and Azoxistrobin. The formulation approach can be extended to deliver other hydrophobic compounds in water at high dilution.
Proposed Definitions, Specifications, and Data Requirements for Identical or Substantially Similar Pesticide Products
Authors: Malak S
Published: April 2008

The Federal Insecticide, Fungicide, and Rodenticide Act (FIFRA) Section 3(c)(3)(B)(i)(I) requires the Office of Pesticide Programs (OPP) of the Environmental Protection Agency (EPA) as expeditiously as possible to review and act on any application received proposing initial or amended registration of an end-use product that, if registered as proposed, would be identical or substantially similar in composition and labeling to a currently registered pesticide identified in the application, or that would differ in composition and labeling from such currently registered pesticide only in ways that would not significantly increase the risk of unreasonable effects on the environment. OPP is proposing some definitions, specifications, and product chemistry data requirements for identical or substantially similar pesticide products, applicable to all pesticides regulated by the EPA. They are required in part to regulate pesticide registrations, reregistrations, and amendments for repacks, alternate formulations, and “me-too” registrations, all require similarity determination by the Agency. The criteria used in the review and decision-making process on initial or amended registration and reregistration of a pending product claimed to be identical or substantially similar to a registered product are based on the chemical composition, physical/chemical properties, and labeling. The purpose of the paper is to make it easier for regulators and the regulated pesticide industry to follow the proposed guidance when applying for “me-too” registration in compliance with FIFRA Section 3(c)(3)(B)(i)(I) and for “alternate formulations” as per the regulations of 40 CFR Part 152.43. The present regulations are general and contain several caveats. Regulations pertaining to acute toxicology, risk assessment, toxicological, ecotoxicological, environmental fate, minor formulation amendments regulated by PR Notice 98-10, are not within the scope of this guidance.
EPA Regulation of Inerts Under the Bush Administration: A New Departure
Authors: Stickle WE
Published: April 2008

During the second term of the Clinton Administration, despite the signing into law of the Food Quality Protection Act of 1996 (FQPA) on August 3, 1996, few initiatives were undertaken by the Administration on inerts. The Bush Administration, however, has begun a series of new initiatives that appear to be elevating inert issues to a new plateau. The new Bush initiative includes the following: 1) adding new resources to the inerts program within the U.S. Environmental Protection Agency (EPA); 2) denying the petitions from the State Attorneys General and the environmental groups to require the full disclosure of inerts on the label; 3) launching a discussion of a new risk assessment model for inerts; 4) focusing on the framework of a federal policy to provide data compensation for inerts; 5) making significant progress on the tolerance reassessment of inerts by completing 87 in 1999 and 287 in 2002 of some 825 food-use inerts that are required to be finalized by August 3, 2006 under FQPA; and, 6) encouraging an international dialogue on harmonization of inert policy within NAFTA, by facilitating the creation of the Non-Agricultural Working Group (NAWG).
Properties of 20 % Cold-Worked 316 Stainless Steel Irradiated at Low Dose Rate
Authors: Allen TR , Tsai H , Cole JI , Ohta J , Dohi K , Kusanagi H
Published: April 2008

To assess the effects of long-term, low-dose-rate neutron exposure, tensile, hardness, and fracture properties were measured, and microstructural characterization was performed on irradiated 20 % cold-worked Type 316 stainless steel. Samples were prepared from reactor core components retrieved from the EBR-II reactor following final shutdown. Sample locations were chosen to cover a dose range of 1–56 dpa at temperatures from 371–390°C and dose rates from 0.8–3.3 × 10-7 dpa/s. Irradiation caused hardening, with the ultimate tensile strength (UTS) reaching about 800 MPa near 20 dpa and appearing to saturate at higher doses. The yield strength (YS) follows approximately the same trend as the ultimate tensile strength. The work-hardening capability of the material decreases with increasing dose. While the material retained respectable ductility at 20 dpa, the uniform and total elongation decreased to < 1 and < 3 %, respectively, at 47 dpa. Fracture in the 30 dpa specimen is mainly ductile but with local regions of mixed-mode failure, consisting mainly of dimples and microvoids. The fracture surface of the higher-exposure 47 dpa specimen displays more brittle features. Changes in yield strength predicted from the microstructural components are roughly consistent with the measured changes in yield strength.
Influence of Oversized Solute Additions on Radiation-Induced Microstructure and Microchemistry in Austenitic Stainless Steel
Authors: Sencer BH , Was GS , Fournier L , Kenik EA , Simonen EP , Bruemmer SM
Published: April 2008

Oversized solute additions (0.3 at% of either Pt or Hf) were found to have a significant effect on microstructural and microchemical evolution in ultra high-purity 316 stainless steel model alloys after proton irradiations at 400°C to nominal doses of 2.5 and 5 dpa. The radiation-induced microstructure of the 316SS base alloy consisted of voids and faulted Frank loops at both dose levels. Platinum addition enhanced void nucleation and increased the loop density and the mean loop diameter. Hafnium addition to 316SS delayed void formation, decreased the mean loop diameter and increased loop density. Grain boundary composition was measured using analytical transmission electron microscopy. Strong radiation-induced grain boundary Cr depletion and Ni enrichment was found in the 316SS base alloy, while oversized element additions reduced segregation levels at low dose. The Pt-doped alloy showed only minor radiation-induced changes in grain boundary composition and no evidence of segregation was observed in the Hf-doped alloy at 2.5 dpa, however, increasing dose resulted in significant radiation-induced segregation in the Hf-doped alloy.
Solute Addition Effect for Fe-15Cr-20Ni Austenitic Steels Irradiated in Joyo
Authors: Fukumoto K , Matsui H , Donomae T , Yamagata I , Akasaka N
Published: April 2008

The relationship between the addition of minor element and the swelling behavior was investigated using six heats of Fe-15Cr-20Ni austenitic model alloys and a PNC 1520 steel irradiated at 480, 570, 620 and 700°C in the Joyo to doses of 20–56 dpa. Phosphorus and boron suppressed the appearance of swelling for these experimental irradiation conditions. Additions of titanium and niobium were effective for suppression of swelling at low temperature, below 570°C. Radiation -induced precipitation is an important factor for controlling the appearance of swelling. The radiation-produced phases in PNC1520 during neutron irradiation are classified into four groups: (1) Frank loops with Ti aggregation on the habit plane, (2) Rod-type precipitates of Fe2P, (3) Large bulk-type precipitates of M23C6, and (4) Blocky-type precipitates of MC with Ti, M6C, Ni-Laves and TiP. The phosphide precipitates strongly suppressed swelling in the low temperature regime as cavity formation started only after phosphide dissolved during neutron irradiation.
The Effect of Hardening Source in Proton Irradiation-Assisted Stress Corrosion Cracking of Cold Worked Type 304 Stainless Steel
Authors: Hash MC , Busby JT , Was GS
Published: April 2008

The goal of this study is to discern whether the irradiation-assisted stress corrosion cracking (IASCC) susceptibility depends on the source of hardening rather than hardening alone. A set of five hardened conditions of commercial 304SS were studied in which the level of hardening remained fixed while the contributions from irradiation and cold work (CW) varied. The extremes of this set were hardening by either proton irradiation at 1.67 dpa only or 35% cold work only. Between these extremes the same value of hardness was reached with a combination of cold work and irradiation. Cold work/proton irradiation combinations used to achieve the target level of hardness were 10% CW + 0.55 dpa, 20% CW + 0.25 dpa, and 25% CW + 0.09 dpa. Proton irradiation was conducted with 3.2 MeV protons at 360°C at a rate of 7 × 10-6 dpa/s. The specimens were then subjected to stress corrosion cracking (SCC) tests in 288°C water typical of normal water chemistry in boiling water reactor (BWR) service conditions. Only the 0% CW + 1.67 dpa and the 10% CW + 0.55 dpa samples showed any sign of IASCC as manifested by intergranular (IG) cracking despite all of the specimens being at the same hardness. All other samples failed without any evidence of IG cracking. Results from this study suggest that radiation hardening, in contrast to cold work, has the most pronounced effect on IASCC.
On the Mechanism of Irradiation Embrittlement Enhancement in Reactor Pressure Vessel Steels at High Neutron Fluences
Authors: Pechenkin VA , Konobeev YV , Stepanov IA , Nikolaev YA
Published: April 2008

The DBTT shift in irradiated VVER pressure vessel steels is represented by standard guidelines with a power law dependence on fast neutron fluence multiplied by a material constant. However, from recent data on surveillance specimens for several units of VVER-440, an irradiation embrittlement enhancement has been observed at neutron fluences above (2–3)×1020 n/cm2 (E>0.5 MeV) with a significant deviation from the standard guideline. This suggests an additional mechanism of irradiation embrittlement at high fluences.

In the present work it was supposed that such a mechanism could be intergranular embrittlement caused by grain boundary phosphorus segregation. A threshold dose was used that accounts for intergranular embrittlement, that occurs after sufficient phosphorus segregation, when the critical stress for intergranular fracture falls below that for cleavage fracture. The modeling of phosphorus accumulation on grain boundaries is performed taking into account the radiation-enhanced phosphorus diffusion by both vacancy and interstitial mechanisms, the radiation-induced segregation in the matrix near grain boundaries, and the Gibbsian adsorption on grain boundaries. Predictions of such a composite model are in agreement with surveillance data for VVER-440.
Irradiation and Post-Annealing Reirradiation Effects on Fracture Toughness of RPV Steel Heat JRQ
Authors: Nanstad RK , Tipping P , Kalkhof RD , Sokolov MA
Published: April 2008

A plate of A533 grade B class 1 steel designated heat JRQ has been used for many research studies around the world, especially those sponsored by the International Atomic Energy Agency. In this study, groups of Charpy impact, tensile, and precracked Charpy specimens of the JRQ plate were irradiated by the Paul Scherrer Institute to four different fast neutron fluences [from 0.39 to 5.0 × 1023 n/m2 (>1 MeV)] in a test reactor. Additional specimens were given a post-irradiation thermal annealing treatment at 460°C for 18 h when 50% of the target fluence was reached, followed by reirradiation to the same target fluences for the four groups of irradiated specimens. Additionally, Oak Ridge National Laboratory has thermally annealed some of the reirradiated specimens, as well as some of those in the irradiated only condition. Charpy impact, tensile, fracture toughness, and hardness tests have been performed to evaluate material response in the various conditions and for comparison with the unirradiated material. Except at the highest fluence, the results show that the material given an intermediate annealing treatment exhibited irradiation-induced transition temperature shifts about the same as those that were only irradiated. However, the upper-shelf energies were generally higher and the yield strengths were generally lower for the reirradiated groups. At the highest fluence, the Charpy 41-J temperature shift was significantly lower for the reirradiated group relative to the irradiated group at the same total fluence. The intermediate thermal annealing resulted in less reirradiation embrittlement of fracture toughness than Charpy impact toughness, while annealing after reirradiation resulted in significant increases in Charpy upper-shelf energy above that in the unirradiated condition. Comparisons of Charpy impact and fracture toughness results are mixed relative to transition temperature shifts for irradiated and reirradiated conditions.
Dependence of Re-embrittlement Rate After Annealing on the Copper, Nickel and Phosphorus Contents in Model Alloys
Authors: Valo M , Ehrnstén U , Kohopää J , Debarberis L , Kryukov A , Rintamaa R
Published: April 2008

Irradiation embrittlement rate as well as the re-embrittlement rate after annealing of pressure vessel steels can in general be described by the copper, phosphorus and nickel contents of the materials. In the current study embrittlement and re-embrittlement rate of 32 different model alloys were measured using sub-size CH-V specimens of dimensions 3 × 4 × 27 mm. The impurity and alloy elements of the model alloys were varied within the limits Cu: 0–1.0 wt-%, P = 0–0.040 wt-% and Ni: 0–2.0 wt-% relatively evenly. The specimens were originally irradiated in the high flux reactor in Petten into a neutron fluence of 0.3×1019n/cm2, E >1 MeV and re-irradiated after the annealing treatment in the Loviisa power reactor into a fluence of 1.0 × 1019n/cm2, E > 1 MeV. In the paper the irradiation and re-irradiation embrittlement rate has been modeled based on the Cu, P and Ni contents of the alloys. Re-irradiation rate was found to be clearly lower than the original irradiation rate except for small corner in the element space, i.e., no nickel, low copper and high phosphorus alloys. Phosphorus coefficient in the re-irradiation shift function is relatively two times higher than in the original irradiation shift function. Many of the alloys in the IAI-condition show intergranular type fracture (IGF). However, the effect of the change of the fracture mode from cleavage to IGF on transition temperature shift remains open. The dependence of irradiation embrittlement, annealing and re-embrittlement behavior on the copper, phosphorus and nickel contents is still not solved, one reason being the relatively limited variation of the key elements in the materials. Model alloys offer a good variation matrix of the elements even, if the measured data cannot be directly applied to real steels.
Critical Review of Through-Wall Attenuation of Mechanical Properties in RPV Steels
Authors: English CA , Server WL , Rosinski ST
Published: April 2008

This paper reviews the current state of knowledge on attenuation of damage parameters in reactor pressure vessels (RPVs). There are two methods for evaluating attenuation of properties through a reactor pressure vessel wall. The first is by direct measurement of the change in mechanical properties from decommissioned RPV sections or from simulated RPV wall experiments. It is shown that, although this approach is appealing, issues associated with knowledge of the start-of-life properties throughout the vessel wall sample and material property data scatter have made past measurements non-definitive in establishing attenuation changes. There is a need for further data on the direct measurement of attenuation, and an experiment is described, that is planned in 2002 under IAEA sponsorship. An alternative method for evaluating embrittlement is the use of a neutron damage exposure parameter and attenuation model coupled with an embrittlement correlation developed from surveillance capsule testing. The significant change in neutron flux spectrum when neutrons are attenuated through the RPV wall defines the need for a suitable neutron exposure damage parameter. The best available neutron exposure damage parameter is dpa. It is shown that plant-specific calculation of dpa through the RPV wall is the best method to be used for the neutron exposure. However, it can lead to slightly less attenuated values for damage at 1/4-T and 3/4-T for the vessel, as compared to using the simple exponential model quoted in Regulatory Guide 1.99, Rev. 2. Finally it is concluded that when using a surveillance correlation model to predict the attenuation of mechanical properties through the RPV wall, the use of a mechanistically guided model appears to be more appropriate than the embrittlement correlation provided in Regulatory Guide 1.99, Revision 2.
A Mechanistically-Guided Charpy Embrittlement Correlation for Reactor Pressure Vessel Integrity Assessment
Authors: Rosinski ST , Server WL , Lott RG
Published: April 2008

The current neutron irradiation embrittlement trend equation used in the U.S. is contained in Nuclear Regulatory Commission (NRC) Regulatory Guide 1.99, Revision 2. The database used to establish this correlation was compiled in the late 1980s. Since that time there has been about a five fold increase in data. Through the EPRI Materials Reliability Program a new and improved transition temperature shift embrittlement correlation has been developed. The recommended model is mechanistically-guided, statistically robust, and stems from earlier work on a mechanistic/statistical model proposed by the NRC. From the independent reviews performed on the NRC proposed correlation, the evaluations of mechanistic understanding and statistical testing were combined to assess the most appropriate form for a mean correlation model. The process of evaluating and reducing the number of fitting parameters was not a simple decision. Engineering judgment, through the development of gating criteria and value/magnitude considerations, led to the development of the proposed correlation. This paper discusses the proposed embrittlement correlation and its mechanistic/statistical bases.
Irradiation Hardening and Microstructural Evolution in Fe-Cu Model Alloys
Authors: Kitao T , Kasada R , Kimura A , Nakata H , Fukuya K , Matsui H , Narui M
Published: April 2008

Irradiation hardening and microstructural evolution und neutron and electron irradiation have been investigated for pure-Fe and Fe-Cu model alloys. Neutron and electron irradiations were performed in the Japan Material Test Reactor (JMTR) and with using Phodtron electron accelerator at about 290°C and 270±30°C, respectively. Irradiation hardening of pure-Fe and Fe-Cu model alloys is saturated at about 1 × 10-3 dpa in both the neutron and electron irradiation. Irradiation hardening recovered in two temperature ranges. The recovery in the lower temperature range depends on copper concentration and electron irradiation dose, while the recovery at a higher temperature range does not. Recovery behavior of the irradiation hardening suggests indirectly that copper atoms suppress the growth of interstitial clusters. The recovery behavior of positron lifetime does not coincide with that of the hardness, suggesting that the vacancy clusters are not the direct main factor controlling the hardening by matrix damages.
Fatigue Response and Life Prediction of Selected Reactor Materials
Authors: Li M , Stubbins JF
Published: April 2008

This paper analyzes experimental fatigue response for selected unirradiated and irradiated reactor materials: AISI 316 stainless steel, ferritic/martensitic MANET and HT9 steels. Available tensile test results on the same or similar materials are used to predict changes in fatigue response using the Universal Slopes method. The predictions are compared with the experimental data to assess the potential for using tensile data to predict reactor component fatigue response. It was found that the effect of irradiation on fatigue life was less severe than on tensile properties. However, tensile properties are useful for qualitative predictions of fatigue response.
Detection of Radiation-Enhanced Diffusion by Means of Neutron-Irradiated Diffusion Couples of Fe-Cr-Ni System
Authors: Akasaka N , Tanaka K , Ohnuki S , Takahashi H , Watanabe S , Itoh M
Published: April 2008

Radiation-enhanced diffusion is one of the most important parameters for the understanding and modeling the effect of radiation on materials. In this study, the average effective interdiffusion coefficients of Ni and Cr in pure iron, an Fe-15Cr-15Ni model alloy and a modified 316 stainless steel for fuel subassembly of FBR were evaluated under neutron irradiation by using “miniature diffusion couples” which were electroplated with Ni or Cr. The miniature diffusion couples were irradiated in the experimental fast reactor JOYO at temperature ranging from 400 to 550°C for 4 220 hours, to doses between 1.4 and 14 dpa. The interdiffusion was enhanced by irradiation. In particular, Ni diffusion increased by several orders of magnitude. The enhancement of diffusion depends on the point defect flux, which is affected by solute elements and the microstructure development under irradiation.
Surprisingly Large Generation and Retention of Helium and Hydrogen in Pure Nickel Irradiated at High Temperatures and High Neutron Exposures
Authors: Greenwood LR , Garner FA , Oliver BM , Grossbeck ML , Wolfe WG
Published: April 2008

Hydrogen and helium measurements in pure nickel irradiated to 100 dpa in HFIR at temperatures between 300 and 600°C show higher gas concentrations than predicted from fast-neutron reactions and the two-step 58Ni(n,γ)59Ni (n,p and n,α) reactions. This additional gas production suggests previously unidentified nuclear sources of helium and possibly hydrogen that assert themselves at very high neutron exposure. The elevated hydrogen measurements are especially surprising since it is generally accepted that hydrogen is very mobile in nickel at elevated temperatures and therefore is easily lost, never reaching large concentrations. However, it appears that relatively large hydrogen concentrations can be reached and retained for many years after irradiation at reactor-relevant temperatures. These new effects may have a significant impact on the performance of nickel-bearing alloys at high neutron fluences in both fission and fusion reactor irradiations.
The Influence of Pre-Irradiation Heat Treatments on Thermal Non-Equilibrium and Radiation-Induced Segregation Behavior in Model Austenitic Stainless Steel Alloys
Authors: Cole JI , Allen TR , Was GS , Dropek RB , Kenik EA
Published: April 2008

The effect of pre-irradiation heat treatments on thermal non-equilibrium grain boundary segregation (TNES) and subsequent radiation-induced grain boundary segregation (RIS) is studied in a series of model austenitic stainless steels. The alloys used for this study are based on AISI 316 stainless steel and have the following nominal compositions: Fe-16Cr-13Ni-1.25Mn (base 316), Fe-16Cr-13Ni-1.25Mn-2.0Mo (316 + Mo) and Fe-16Cr-13Ni-1.25Mn-2.0Mo-0.07P (316 + Mo + P). Samples were heat treated at temperatures ranging from 1100 to 1300°C and cooled at four different rates (salt brine quench, water quench, air cool and furnace cool) to evaluate the effect of annealing temperature and quench rate on TNES. The alloys were then processed with the treatment (temperature and cooling rate) that resulted in the maximum Cr enrichment. Alloys with and without the heat treatment to enrich the grain boundaries with Cr were characterized following irradiation to 1 dpa at 400°C with high-energy protons in order to understand the influence of alloying additions and pre-irradiation grain boundary chemistry on irradiation-induced elemental enrichment and depletion profiles. Various mechanistic models will be examined to explain the observed behavior.
Grain Boundary Phosphorous Segregation and Its Influence on the Ductile Brittle Transition Temperature in Reactor Pressure Vessel Steels
Authors: Kimura A , Shibata M , Kasada R , Nakata H , Fujii K , Fukuya K
Published: April 2008

The materials used for this work were two sorts of reactor pressure vessel (RPV) steels, which contain different amounts of phosphorous (P), namely 0.011 and 0.002 wt%. The specimens for Charpy V-notch (CVN) impact test, Auger electron spectroscopy (AES), and tensile test were thermally aged at 400, 450, and 500°C for 1000, 3000, and 5000 h. After the thermal aging, the AES specimens were broken in the AES chamber to measure the P concentration at grain boundaries. The AES measurements for as-received specimens were carried out following hydrogen charging so that grain boundary facets were available even without P segregation. The AES measurements revealed that the peak height ratio (PHR) of P/Fe at the grain boundaries of the high-P steel were 0.066, 0.141, and 0.120 in the specimens aged at 400°C for 3000 h, 450°C for 3000 h, and 500°C for 1000 h, respectively. The ductile-brittle transition temperature (DBTT) was measured for the aged specimens, and the ▵DBTT of 15K was observed only for the specimen aged at 450°C for 3000 h, although no changes in the hardness and tensile properties were observed. The grain boundary fracture ratio (GBFR) increased with increasing the PHR of P/Fe. Grain boundary fracture mode was located at the area close to the V-notch root. There was a good relationship among PHR, GBFR, and DBTT, indicating directly that the shift in the DBTT was due to grain boundary embrittlement caused by P segregation.
The Modeling of Radiation-Induced Phosphorus Segregation at Point Defect Sinks in Dilute Fe-P Alloys
Authors: Stepanov IA , Pechenkin VA , Konobeev YV
Published: April 2008

Both the intergranular and intragranular segregation of phosphorus may significantly contribute to irradiation embrittlement of reactor pressure vessel steels. The modeling of phosphorus radiation-induced segregation at cylindrical (dislocations), spherical (precipitates and voids) and flat (sample surfaces, grain boundaries) point defect sinks has been carried out in order to compare the kinetics and extent of segregation at various point defect sinks. Dilute Fe-P alloys relevant to model and VVER-440 pressure vessel steels were considered.

It is shown that the time to reach steady state phosphorus concentration near dislocation or precipitate is much less than that near grain boundary. Although the steady state phosphorus concentration near dislocations or precipitates is much less than that near grain boundary, a “fast” phosphorus segregation at these sinks may lead to decreasing the free phosphorus content in the matrix and to reducing its subsequent accumulation on grain boundaries at high densities of internal sinks. A more significant effect on the kinetics of grain boundary phosphorus segregation could be caused by the contribution of precipitates to point defect sink strength.
Irradiation Induced Vacancy-Cu Aggregations in Fe-Cu Model Alloys of Reactor Pressure Vessel Steels Studied by Positron Annihilation
Authors: Nagai Y , Takadate K , Tang Z , Ohkubo H , Hasegawa M
Published: April 2008

Fe-Cu model alloys (0, 0.05, 0.15, 0.30 and 1.00 wt.%Cu) of Nuclear Reactor Pressure Vessel Steels irradiated by fast neutrons (8.3×1018 n/cm2) at about 100°C are studied by positron annihilation spectroscopy, positron lifetime and coincidence Doppler roadening, in order to analyze the irradiation-induced vacancy-Cu aggregation. We have observed nanovoids (vacancy clusters) whose inner surfaces are covered by Cu atoms in not only high and medium Cu (0.15–1.0 wt.%) alloys but also low Cu (0.05 wt.%) alloys. The typical size of the nanovoids and the fraction of the covering with Cu on the inner surfaces depend on the Cu content. The dissociation of vacancies from the nanovoids by the post-irradiation isochronal annealing at about 400°C leads to the formation of the ultrafine Cu precipitates even for the Fe-0.05wt.%Cu alloy.
Precipitation and Amorphization in Boron Carbide Irradiated by High Energy Helium Ions
Authors: Maruyama T , Iwanami M , Ohnuki S , Suda T , Watanabe S , Ikezawa K
Published: April 2008

Two kinds of hot-pressed B4C specimens were irradiated with 15MeV He+ from 4.3×1014 to 1.13×1016ion/cm2 at 400–760 °C, and with 100keV He+ from 1.0×1013 to 2.0×1017ion/cm2 at room temperature. After ion irradiation, the microstructure of specimens was analyzed by transmission electron microscopy (TEM). The ion-irradiation by 15MeV helium ions produced a radiation-enhanced precipitation with Fe-rich composition and the radiation-induced amorphization in the B4C matrix, but the irradiation by 100keV helium did not make amorphization. This result suggests that the inelastic scattering (electron excitation), rather than elastic scattering, plays an important role in amorphization of B4C. The annealing of ion irradiated B4C above 1000°C indicated incineration of precipitated crystals and a formation of a small numbers of helium bubbles.
Changes in Mechanical Properties of High-Purity V-4Cr-4Ti-Si, Al, Y Alloys after Neutron Irradiation at Relatively Low Temperatures
Authors: Chuto T , Satou M , Hasegawa A , Abe K , Muroga T , Yamamoto N
Published: April 2008

Mechanical properties after neutron irradiation of V-4Cr-4Ti-0.1Si-0.1Al-0.1Y and V-4Cr-4Ti-0.1Si-0.1Al-0.3Y alloys (nominal weight percentage) were studied. Neutron irradiation was carried out at 290°C to 8×1022 n/m2 (E>1 MeV, about 0.014 dpa) in the Japan Materials Testing Reactor (JMTR). Tensile tests were carried out using miniaturized specimens at ambient temperature and irradiation temperature. Charpy impact tests were conducted at temperatures from -196 to 0°C using an instrumented machine. There is little difference in tensile properties after neutron irradiation between the two alloys. Increase in yield stress was relatively small (∼100 MPa), and uniform elongation remained more than 10%. Because of a low concentration of interstitial impurities, good tensile properties could be retained even after neutron irradiation at 290°C. Ductile-to-brittle transition temperature (DBTT) of V-4Cr-4Ti-0.1Si-0.1Al-0.1Y alloys hardly changed, whereas absorbed energy was slightly reduced after neutron irradiation.
Microstructure Response in Copper and Copper Alloys Irradiated with Fission Neutrons with Controlled Temperature Variations
Authors: Muroga T , Watanabe H
Published: April 2008

The effects of temperature variation on microstructural evolution were investigated for Cu, Cu-5Ni, Cu-3.5Zn, and Cu-5Ni-2Zn irradiated in JMTR and HFIR. The low temperature pre-irradiation at 477 K to 533 K was shown not to influence microstructural evolution significantly during the following irradiation at 613 K to 693 K. On the other hand, downward temperature shift during irradiation was shown to produce void formation in Cu and Cu-3.5Zn. The mechanism of the temperature variation effects was discussed based on the defect properties and the details of the temperature transient history during irradiation.
Extension of a Microstructure-Based Fatigue Crack Growth Model for Predicting Fatigue Life Variability
Authors: Enright MP , Chan KS
Published: April 2008

Most of the existing crack growth models rely on empirical constants derived from curve fits of data at specific test conditions. Although statistical information can be obtained for many of these constants, multiple experimental tests typically must be performed to represent the wide range of the response. In this paper, an alternative approach is presented that links fatigue crack growth parameters to material and microstructural size parameters via a microstructure-based fatigue crack growth (FCG) model. In addition, variation of initial crack size due to microstructural variation is modeled in terms of a crack-size-based fatigue crack initiation model. Variations of microstructural parameters are described in terms of a probabilistic framework. The probabilistic, microstructure-based, FCG approach is illustrated for a Ni-based superalloy in which the influence of changes in the main descriptors of the individual microstructural parameters on initial crack size, crack growth rate, and fatigue life is shown. Stochastic model results are compared with existing experimental data to illustrate the feasibility of the approach for predicting da/dN variability due to microstructure variations.
Scatter in Fatigue Crack Growth Rate in a Directionally Solidified Nickel-Base Superalloy
Authors: Highsmith S , Johnson WS
Published: April 2008

Directional solidification of nickel-base superalloy components for gas turbine rotor blades offers a significant improvement in creep strength while at the same time yielding an anisotropic, heterogeneous microstructure. In such a material, some of the continuum assumptions of linear elastic fracture mechanics begin to break down, and local (microscopic) conditions can lead to significant deviation in fatigue crack growth rate from the global (macroscopic) trend. Fatigue crack life prediction for a large population of fielded components requires a probabilistic treatment of the material fatigue crack growth behavior. A common approach to probabilistic fatigue crack life prediction involves sampling the Paris law coefficients from a large number of crack growth experiments, which can lead to effectively “smoothing” the local intraspecimen variability out of the model. The length scale of variability is discussed as it relates to material microstructure and crack life prediction. Results from fatigue crack growth experiments on a directionally solidified superalloy are presented and spatial variation in the fatigue crack growth rate is examined. Periodicity of the crack growth rate variation is compared with the scale of microstructural heterogeneity.
Mechanism-Based Variability in Fatigue Life of Ti-6Al-2Sn-4Zr-6Mo
Authors: Jha SK , Larsen JM , Rosenberger AH , Hartman GA
Published: April 2008

The variability in fatigue life of a Ti-6Al-2Sn-4Zr-6Mo alloy was studied. The cumulative life distribution plot was found to be composed of two distinct failure mechanisms, designated as Type-I and Type-II. The likelihood of Type-I vs. Type-II failure shifted with respect to the stress level, such that at lower stress levels, there was increased probability of Type-II failure. It also was found that the variability in life was introduced primarily at the crack nucleation stage, specifically, formation of a stage-I crack across an equiaxed primary-α particle.
Corrosion Risk Assessment of Aircraft Structures
Authors: Liao M , Komorowski JP
Published: April 2008

This paper presents a comprehensive summary of IAR/NRC research on risk assessment of aging aircraft structures in the presence of corrosion and fatigue. Extensive test data, especially for fuselage splices containing corrosion and multiple site fatigue damage (MSD) and coupons cut from service exposed aircraft lap joints, have been generated under previous projects. Based on these test data, an empirical stochastic crack growth model was first developed to analyze the probabilistic fatigue characteristics of the splices. Risk analysis was then performed on the fuselage splices using the computer codes PRISM (Bombardier Aerospace, Inc.) and PROF (United States Air Force). Holistic life assessment methodology (HLAM), which aims to quantify structural integrity in the entire life cycle by addressing the interaction effects of corrosion and fatigue, has advanced considerably during the past five years. Risk analysis based on HLAM was carried out on the fuselage splices. The analytical results, which were obtained at different stages, are compared with the test results. It is shown that corrosion in lap joints, even at the levels less than the typical maintenance limit (i.e., 10% material loss), could significantly increase the risk level of structural failure.
Role of Variable Amplitude Fatigue Standards in Improving Structural Integrity
Authors: Hopkins SW , Mitchell MR , Ménigault J
Published: April 2008

Fatigue failures of structural components continue to be a serious concern to the well-being and economics of our worldwide society because the majority of all such components fail by this mechanism. If some of these failures could be prevented through better design with our understanding of how materials behave, it would have a major impact on the economics of society.

American Society for Testing and Materials International (ASTM) Committee E08 on Fatigue and Fracture, International Organization for Standardization, Technical Committee 164, Subcommittee 5 (ISO/TC164/SC5) on Fatigue Testing of Metallic Materials and other relevant committees interested in the fatigue phenomena are involved in developing standards for testing and analysis under variable amplitude loading. Currently no variable amplitude fatigue testing standards exist. The organizational structures of some committees are provided along with examples of variable amplitude fatigue failures. There is some interaction between ASTM, European Structural Integrity Society (ESIS), and ISO, and it is hoped that additional interaction will occur so that all of the vast knowledge on fatigue from around the world may be focused to develop standards that will benefit everyone.

To demonstrate the need for such international standards, several examples of variable amplitude-type failures are presented and discussed. As a result of such failures, there is an obvious need to translate the constant amplitude and variable amplitude laboratory test data into the design of real structures.
The F/A-18E/F Full-Scale Static and Fatigue Test Programs — An Overview
Authors: Sullentrup MG
Published: April 2008

The structural certification of F/A-18E/F airframe included fullscale fatigue and static test programs. This paper outlines the test programs, discusses test objectives, discusses test results, highlights some significant advancements in the state-of-the-art developed to support this test program, and offers recommendations for future full-scale certification test programs.

The method used to correlate static test measured strains to finite element model predictions is discussed. The method used to certify redesigned structural components without the benefit of a full-duration fatigue test is discussed. Innovations involving real-time data monitoring, rapid post-test analysis of results, characterization of measured endpoint strains during fatigue cycling, and comparison of block-to-block measured strain response are discussed.

There were many lessons learned during these test programs. These are summarized and discussed. Recommendations for future full-scale certification test programs are also discussed.
Spectrum Fatigue Testing and Small-Crack Life Prediction Analysis on a Coupon Similar to a Critical Design Detail of a CF188 Hornet Component
Authors: Yanishevsky M , Everett RA
Published: April 2008

Numerous studies have shown that small-crack methodology can be used to predict the total fatigue life of laboratory type (KT = 1 and 3) specimens under variable amplitude loading. Prior to investigating how well this fatigue life prediction capability could be extended to “real” aircraft structures, an intermediary step was taken where total fatigue life was predicted for a laboratory type specimen similar to a critical design detail in a fighter aircraft fuselage bulkhead. Using the small-crack analysis in the computer code called FASTRAN and assuming an initial crack size of 20 microns, the time to catastrophic failure of the test coupons was predicted to within 10 % of the average test times.
Spectrum Coupon Testing of Fatigue-Resistant Fasteners for an Aging Military Aircraft
Authors: McMaster FJ , McKeighan PC
Published: April 2008

An experimental program of work was undertaken to assess the life improvement gained through utilizing cold expansion technology to enhance the resistance of cracking at fatigue critical locations (FCLs) in an aging military trainer aircraft. The FCLs considered included a countersunk hole and nutplate on two different wing spars. The overall goal of the experimental work was to provide a comparative assessment of the influence of the major variables examined, which included cold expansion method and process, hole size, countersink size, nutplate geometry, flight spectrum, and joint configurations. The results of this work clearly illustrated the inherent sensitivity of life improvement factors to the myriad of variables involved. Nevertheless, the foregoing experimental work clearly demonstrated the valuable life improvement that is provided by cold expansion for nearly all cases examined.
Crack Initiation at a Notch under Constant and Selected Variable Amplitude Loading Conditions
Authors: Gérard N , Leroy R , Girard O , Ranganathan N
Published: April 2008

In a previous study, we showed that crack initiation life at a notch tip can be modeled as the micro crack propagation life from an initial microstructural defect up to a crack size of about 500 μm. This model is based upon the assumption that short cracks at a notch propagate without any significant closure effects. In our present experimental study, the results of fatigue tests to verify this hypothesis are presented and discussed.

The fatigue tests were conducted in ambient air on single edge notched specimens with a theoretical stress concentration factor of 3.14 on thin sheets of 1.2 mm thick Aluminum alloy 2024 T351. The test conditions studied are: constant amplitude tests at stress ratios of 0.1, 0.3, and 0.5 and variable amplitude tests using an extract from the TWIST spectrum. The tests were carried out at a nominal frequency of 10 Hz. At selected intervals, micro crack advance (if any) was determined using replicas. The measurements were made at the maximum stress for constant amplitude tests and at a chosen positive stress for variable amplitude tests (avoiding any overload). The smallest crack size detected is about 10 μm.
Fatigue Resistance Evaluation and Crack Kinetics Study for Aero Engine Fan Blades under Random Vibration
Authors: Tumanov NV
Published: April 2008

Various types of violent random vibration of aero engine fan blades were investigated. Technique for random fatigue resistance evaluation of the blades has been developed which is based on the relation obtained between amplitude of equivalent sinusoidal stresses, parameters of random stress envelope, and data of conventional constant amplitude tests. Experimental validation of the technique has been carried out on the base of comparison between the calculated and experimental values of equivalent amplitude. For this purpose fatigue tests were performed in the course of which the features of intense service random vibration of the blades were simulated. Some peculiarities of fatigue crack kinetics under random loading were studied.
High Cycle Variable Amplitude Fatigue of a Nodular Cast Iron
Authors: Marquis GB , Rabb BR , Karjalainen-Roikonen P
Published: April 2008

This paper provides a brief summary of life prediction methods for variable amplitude fatigue. Special attention is given to cracks propagating from nominally defect free components in the high cycle regime where a significant portion of the fatigue damage can be attributed to cycles with amplitude less than the fatigue limit observed under constant amplitude loading. Constant and variable amplitude fatigue data for a nodular cast iron are presented. An effective stress method for variable amplitude loaded similar to the Topper model is developed. Most model parameters are derived from constant amplitude S-N curves and the Haigh diagram, but two sets of long life variable amplitude tests are needed to derive the variable amplitude interaction parameters.