bluuebunny/crossref_metadata_2025 huggingface dataset:
Lower Extremity Injuries Involving Traditional Alpine Skis versus Short Skis with Non-release Bindings
Authors: Johnson RJ , Ettlinger CF , Shealy JE
Published: April 2008

This study was developed to evaluate the relative incidence of lower leg and anterior cruciate ligament (ACL) injuries in two skier populations: traditional Alpine skiers and skiboarders. Skiboards are short skis usually less than 100 cm with non-releasable bindings.

The authors evaluated injured snow sports participants in a clinic at Sugarbush ski area in Vermont. The study analyzed four seasons (1997/1998 – 2000/2001) using a casecontrol design.

A total of 34 skiboard-related injuries and 1720 injuries related to conventional skiing were evaluated. Approximately 2.2% of the population used skiboards. Although overall the risk of injury for skiboarders was nearly the same as for conventional skiers, skiboarders sustained significantly higher incidences of ankle and tibia shaft fractures than other Alpine skiers (p< 0.000001). Severe ACL injuries occurred to 19.7% (339) of the Alpine skiers and 0% (0) of skiboarders, making the risk of ACL injury among skiboarders low in comparison to conventional skiers (p< 0.000001).

The authors' analysis strongly implies that the unacceptably high risk of lower leg injury associated with skiboarding is due to the use of non-release bindings. The fact that ACL injury to skiboarders was not higher than for conventional skiers another of the authors' previous conclusion that binding function is not related to the production of ACL injuries in skiing. The fact that the incidence of ACL injury to skiboarders was much lower than for conventional skiers supports another of the authors' previous conclusions that the tail of the Alpine ski, which is largely missing in skiboards, creates a unique lever system (“Phantom Foot”) capable of applying unusual loads to the knee.
Fatigue Crack Growth of a Ni-P Amorphous Alloy Thin Film
Authors: Takashima K , Shimojo M , Higo Y , Swain MV
Published: April 2008

Fatigue crack growth behavior has been investigated for micro-sized Ni-P amorphous alloy specimens. Cantilever beam type specimens (10 μm by 12 μm by 50 μm) with notches were prepared from Ni-P amorphous thin film by focused ion beam machining. Fatigue crack growth tests were carried out in air at room temperature using a newly developed mechanical testing machine that can apply cyclic loading to micro-sized specimens. Striations were observed clearly on the fatigue surface, and fatigue crack growth resistance curves as a function of stress intensity range (ΔK) were obtained from careful measurements of the striation spacings. The fatigue crack growth rates at stress ratios of 0.3 and 0.5 were greater than that at 0.1 under a given value of ΔK. This suggests crack closure may occur even in such micro-sized specimens and may affect the fatigue crack growth behavior.
High Accuracy Measurement of Elastic Constants of Thin Films by Surface Brillouin Scattering
Authors: Beghi MG , Bottani CE , Pastorelli R
Published: April 2008

Elastic properties of thin supported films can be derived from the dispersion relations of surface acoustic waves (SAWs) of layered structures. SAW velocities can be measured by surface Brillouin scattering (SBS), i.e., light scattering by thermally excited SAWs. Since SAW velocities can be computed as functions of the elastic properties of both the film and the substrate, if film thickness and density are independently measured the elastic constants can be obtained fitting the computed velocities to the measured ones. Our data analysis technique is discussed. Accuracy of the measured velocities is crucial: the SBS measurement technique is analyzed, giving quantitative estimates of errors and uncertainties, and discussing procedures to reduce them. Some examples are considered in detail, showing that SBS measurements allow the determination of film elastic constants on films of thickness down to tens of nanometers, with precision ranging from reasonable to very good.
From Clinton to Bush: Continuity and Change in Federal Pesticide Policy
Authors: Stickle WE
Published: April 2008

As the nation experiences a shift from the Clinton to the Bush administration, here are important changes in federal pesticides policy. Conversely, there are many areas of continuity between the two administrations. First, the Bush administration has reversed the previous administration's effort to encourage full disclosure of inerts on the label. On July 18, 2001, the administration rejected the petitions of 180 environmental groups and eight Attorney Generals that called for full disclosure of inerts on the label. Second, it reversed the arsenic policy, as well as several other approaches. The Bush administration has continued to support the EPA vs. NRDC settlement decision on January 19,2001, supporting the deadlines for its implementations of FQPA. In addition, the Bush EP A has held a meeting and asked for comments on the Confidential Business Information proposal, including up-front substantiation of information submitted for pesticide-registered products. Third, Bush has continued Clinton's pesticide fee proposals and actually an enlarged the registration fee from $16 million in fiscal year 2001 to $25 million in fiscal year 2002, and increased and enlarged the tolerance processing fee from $28.3 million to $51 million for fiscal year 2002. A close examination of the Bush policy toward pesticide reveals elements of change and continuity and lays the foundation for future directions in pesticide public policy.
Pesticide Delivery: Multiple Role of Adjuvants in Foliar Application of Systemic Compounds
Authors: Bukovac MJ , Cooper JA , Whitmoyer RE , Brazee RD
Published: April 2008

The multiple role of adjuvants in spray application of systemic agrochemicals is reviewed with special reference to tree fruits. The spray application process can be viewed as a series of interdependent events, namely formulation, atomization, spray transfer and interaction with the plant surface leading to retention and penetration. Adjuvants play a role in each event for they are used extensively in formulation and as a tank mix during application. They facilitate solubilzation of the active ingredient and modify the physico-chemical properties of the spray solution. The size distribution of the spray may be shifted to a lower or higher VMD by surfactants and drift retardants, respectively. Spray retention and spreading are increased on difficult to wet plant surfaces. Foliar penetration can be increased by stomatal pore infiltration by surfactants that lower surface tension to < 30 mN m-1. Transcuticular penetration may be depressed by adjuvants that do not penetrate, but reside on the surface, in the spray droplet residue and solubilize/complex the agrochemical in micelles (or other momomer agregrates) and effectively reducing the driving force. Other surfactants penetrate into the cuticle and plasticize the waxes, leading to increased transcuticular diffusion of the active ingredient. Implications for the presence of multiple spray additives in the spray solution and droplet residue on performance of the active ingredient are stressed.
Pulse Width Modulated Sprays for Flow Rate and Droplet Size Control: Spray Dynamics and Field Performance
Authors: Giles DK , Downey D , Kolb T , Grimm JG
Published: April 2008

Agrochemical application is made under the simultaneous demands of efficacious deposit, management of off-site movement including drift, and high time and labor productivity of the operation. Control of nozzle flow rate and droplet size provides the means to maintain efficacy while increasing productivity and reducing spray drift. Additionally, the maintenance of desired droplet size spectra while applying a variable rate prescription maintains the quality of the application job. Pulse width modulation is a technique that allows independent control of flow rate, droplet size and spray dynamics. Individual nozzles are controlled by dedicated solenoid valves closely coupled to the nozzle. The working range of rate control can be expanded to approximately 8:1, far beyond that of conventional pressure modulation. The technique has been integrated into an electronic control system for retrofit to existing rate control electronics. Laboratory and field testing has established the performance and utility of the design.
Protection of the Longitudinal Member Interconnection by ASTM F 1798-97 Interconnection Mechanism and Subassemblies Standard Guide
Authors: Carson WL
Published: April 2008

The same screw-rod interconnection was tested at two labs. One used the fixed-fixed end straight rod assembly in ASTM F 1798-97. The other used a fixed-free end equivalent assembly unilateral construct. The fixed-fixed assembly consistently produced higher fatigue strength, and a different failure mode with only one exception. Freebody diagram analysis of the fixed-fixed end rod-connector assembly revealed that the superior and inferior ends of the rod shared in resisting the applied load, which resulted in lower internal forces and moments than in the inferior rod end of the fixed-free assembly. Lordotically contoured rods had lower flexion fatigue life than straight rods due to the residual tensile stress from contouring. Changing ASTM F 1798-97 to fixed-free end assembly testing is recommended since the interconnection loading conditions created are “worst case” and are more clinically relevant (particularly at ends of constructs), and tests can be performed with bent or straight rods.
Processing Platinum Enhanced Radiopaque Stainless Steel (PERSS®6) for Use as Balloon-Expandable Coronary Stents
Authors: Dennis JZ , Craig CH , Radisch HR , Pannek EJ , Turner PC , Hicks AG , Jenusaitis M , Gokcen NA , Friend CM , Edwards MR
Published: April 2008

A platinum-enhanced variant of UNS S31673 stainless steel has been eveloped for use in fabricating balloon-expandable coronary stents. PERSS® is sufficiently radiopaque to be detected by current radiographic methods and maintains compliance with ASTM requirements. Boston Scientific Corporation/Interventional Technologies (BSC/IVT) has implemented a pilot program for the development of PERSS with the intent of achieving vertical integration of the manufacturing process. PERSS ingots containing 5 wt% platinum were cast by vacuum induction melting, refined by vacuum arc remelting, upset in a forge, then hot and cold-rolled into sheet and foil. The sheet was cold-rolled on a 20-high cluster mill to a foil thickness of less than 0.25 mm (0.01 inches). While the final product otherwise meets the ASTM specification for UNS S31673 alloys, intentional addition of unspecified additional elements precludes its compliance with same.
Influence of Macrophage Cells on 316L Stainless Steel Corrosion
Authors: Parker SH , Lin HY , Zardiackas LD , Bumgardner JD
Published: April 2008

In vitro corrosion tests have not evaluated the role of cells on the corrosion of implant quality 316L stainless steel. A new cell-culture corrosion cell was used to simulate the clinical condition of cells attached to and growing on the alloy to evaluate the effects of cells on alloy corrosion and the effect of corrosion products on cells. The corrosion potential, charge transfer, and surface composition of the alloy were measured in the presence and absence of macrophage cells (RAW 264.7) or cells stimulated to release NO over 72 hours. Whereas there was no statistical difference in the corrosion of 316L stainless steel in the presence of macrophage cells as compared to culture media alone, there was a trend for higher corrosion to occur in the presence of the cells. Corrosion was further reduced when cells were stimulated to release NO which may have oxidized the implant and contributed to an enhancement of its surface oxide. These data suggest that cells may alter alloy surface oxides and affect alloy corrosion.
Fretting and Anodic Current of the Taper Interface of Stainless Steel Hip Stems/Cobalt-Chromium Femoral Heads
Authors: Zhu M , Windler M
Published: April 2008

Three types of hip stems, MS-30™ high-nitrogen stainless steel, Natural Hip™ cobalt-chromium, and APR® II porous titanium were interfaced with cobalt-chromium femoral heads. They were tested according to ASTM F 1875-98. In the initial 1 Hz cyclic loading up to 480 cycles, the average fretting current generated from the taper interface was 0.4, 0.6, and 1 μA, respectively for the stainless steel, cobalt-chromium, and titanium stems. In the following 2 Hz cyclic loading up to 3600 cycles, the average fretting current was 1.3, 0.6, and 2.25 μA, accordingly. In the potentiodynamic polarization, the titanium stems showed relatively high anodic current in the range of -100 to 500 mV. The cobalt-chromium stems had the highest anodic current in the range of 500 to 1200 mV. The stainless steel stems exhibited the best corrosion resistance in the whole potential range of polarization.
Investigation of Frog Abnormalities on National Wildlife Refuges in the Northeast U.S.
Authors: Eaton-Poole L , Pinkney AE , Green DE , Sutherland DR , Babbitt KJ
Published: April 2008

To address concerns about frog abnormalities, the U.S. Fish and Wildlife Service examined over 3,643 frogs and toads on National Wildlife Refuges (NWRs) in the Northeast U.S. The objectives were to: 1) determine if certain refuges had sites where abnormalities were frequently observed; 2) evaluate if the prevalence of abnormalities at a site was consistent within a season and among years; and 3) investigate possible causes. Sampling was conducted from 1999 through 2001. A complete sample from a site consisted of ≥50 metamorphs of one species. The prevalence of abnormalities ranged from 0 to 15% and fluctuated within season and among years. The most common external abnormalities were truncated limbs, and missing limbs, feet, and digits. Frogs with duplication of limb segments were rare (6). Based on radiographical examinations of 89 abnormal frogs, 55 had abnormalities due to trauma, 22 due to malformations, and 12 could not be classified. Metacercariae of the trematode Ribeiroia were detected in substantial numbers in two species from Iroquois NWR, with one specimen having supernumerary hindlimbs. We recommend continued sampling and integrated, causal evaluations on NWRs where the prevalence of abnormalities exceeds 5% or where the types of abnormalities warrant further study.
Determination of Malathion Aerial Drift and Associated Effects to the Endangered Wyoming Toad (Bufo baxteri) Using Surrogate Woodhouse's Toads (Bufo woodhousii) at Mortenson and Hutton Lake National Wildlife Refuges and Potential Reintroduction Sites
Authors: Dickerson KK , Hooper MJ , Huang T , Allen M
Published: April 2008

The endangered Wyoming toad is confined to Mortenson National Wildlife Refuge in southeast Wyoming. Pesticide aerial drift from mosquito control activities adjacent to the refuge may be partially responsible for the toad's decline. Spray cards had detectable malathion concentrations at three sites but survival of surrogate Woodhouse's toads was 100% and mean ChE activities in brain and plasma samples did not differ significantly among sites. Righting trial times in surrogates among sites after spraying were not significantly different. Terrestrial invertebrate abundance results were inconclusive but differences in aquatic invertebrate relative abundance before or after spraying were not significant except at the reference site and Meeboer Lake. Our results indicate that, although some malathion drift is occurring, the toads were not exposed to malathion concentrations great enough to reduce adult survival, affect predator avoidance behavior, or reduce their food source. The data also provide needed information on ChE activities in amphibians.
Synergistic Effects of a Combined Exposure to Herbicides and an Insecticide in Hyla versicolor
Authors: Mazanti L , Sparling DW , Rice C , Bialek K , Stevenson C , Teels B
Published: April 2008

Combinations of the herbicides atrazine and metolachlor and the insecticide chlorpyrifos were tested under both laboratory and field conditions to determine their individual and combined effects on amphibian populations. In the lab Hyla versicolor tadpoles experienced 100% mortality when exposed to a high combination of the pesticides (2.0 mg/L atrazine, 2.54 mg/L metolachlor, 1.0 mg/L chlorpyrifos) whereas low concentrations of the pesticides (0.2 mg/L atrazine, 0.25 mg/L metolachlor, 0.1 mg/L chlorpyrifos) or high concentrations of either herbicides or insecticide alone caused lethargy, reduced growth and delayed metamorphosis but no significant mortality. In the field high herbicide, low insecticide and low herbicide, low insecticide mixtures significantly reduced amphibian populations compared to controls but in the low herbicide, low insecticide wetlands amphibian populations were able to recover through recruitment by the end of the season.
Establishing Causality in the Decline and Deformity of Amphibians: The Amphibian Research and Monitoring Initiative Model
Authors: Little EE , Bridges CM , Linder G , Boone M
Published: April 2008

Research to date has indicated that a range of environmental variables such as disease, parasitism, predation, competition, environmental contamination, solar ultraviolet radiation, climate change, or habitat alteration may be responsible for declining amphibian populations and the appearance of deformed organisms, yet in many cases no definitive environmental variable stands out as a causal factor. Multiple stressors are often present in the habitat, and interactions among these can magnify injury to biota. This raises the possibility that the additive or synergistic impact of these stressors may be the underlying cause of amphibian declines. Effective management for the restoration of amphibian populations requires the identification of causal factors contributing to their declines. A systematic approach to determine causality is especially important because initial impressions may be misleading or ambiguous. In addition, the evaluation of amphibian populations requires consideration of a broader spatial scale than commonly used in regulatory monitoring. We describe a systematic three-tiered approach to determine causality in amphibian declines and deformities. Tier 1 includes evaluation of historic databases and extant data and would involve a desktop synopsis of the status of various stressors as well as site visits. Tier 2 studies are iterative, hypothesis driven studies beginning with general tests and continuing with analyses of increasing complexity as certain stressors are identified for further investigation. Tier 3 applies information developed in Tier 2 as predictive indicators of habitats and species at risk over broad landscape scales and provides decision support for the adaptive management of amphibian recovery. This comprehensive, tiered program could provide a mechanistic approach to identifying and addressing specific stressors responsible for amphibian declines across various landscapes.
Agricultural Applications of Structured Surfactant Formulations
Authors: Elsik CM , Perdreau L , Rollinson M , Diu ML
Published: April 2008

Structured Surfactant Formulations (SSF) are close-packed three-dimensional matrices of a liquid crystalline phase that suspend insoluble pesticide materials. The active ingredient can be either solid or liquid. Additional actives and/or adjuvants can be dissolved or suspended in the formulation if desired. The main advantage of an SSF over standard formulation alternatives is that no thickening or suspending agents are required. The SSF formulation can be solvent-free if desired, or include an oil adjuvant.

A brief introduction on surfactant phase behavior will be presented as background material. When the surfactant loading in aqueous solutions reaches high levels the surfactants begin to associate in liquid crystalline phases. Liquid crystalline phases can also be formed at low surfactant concentration by a technique known as salting out. This phase behavior can be exploited by suspending dispersions of pesticide active ingredients using economical levels of surfactant. A typical SSF contains from 0–60 w/w% active, surfactants for wetting and dispersing as well as structuring, and finally antifreeze and antifoam, if required. The typical properties of an SSF are excellent concentrate physical stability, relatively low viscosity (after the yield stress is overcome), good storage stability, good wetting, and the ability to form stable suspensions on dilution in the spray tank.

SSF technology can be applied to a wide range of pesticide materials, including herbicides, fungicides, and insecticides. The development of an herbicide SSF is presented that demonstrates how surfactant chemistry can be used to optimize the formulation efficacy. Combination packs that include both water-soluble and water-insoluble actives are also presented. Formulation adjuvants such as oils or electrolytes can also be incorporated into an SSF formulation to increase its biological activity.
Determination of Organosilicone Surfactant Phytotoxicity for Selected Vegetable Species
Authors: Sun JS , Policello GA , Paccione MA
Published: April 2008

Surfactants are widely used as components of pesticide formulations and sprays. Generally, they are classified as “inert”, although some surfactants have been shown to cause unwanted damage to plant tissue expressed as phytotoxicity. Surfactant phytotoxicity is dependent on concentration, chemical structure, spray volume, and plant species. The mode action of surfactant phytotoxicity is still not well understood.

The current experiments were conducted to evaluate the effect of organosilicones or blends with nonionic surfactants, on certain plants. A series of spray trials to assess the potential for surfactant phytotoxicity was conducted on several widely commercialized vegetable species.

In addition to adjuvant type, spray volume (200 L/ha and 800 L/ha) was also evaluated as a potential source of phytotoxicity, when considered in conjucntion with adjuvant rate.

Phytotoxic effects were not observed for standard adjuvant rates. However, excessive rates (4X normal) showed different levels of phytotoxicity, depending on adjuvant used, the crop and spray volume. One adjuvant in particular (silicone blend) was the least phytotoxic, where all treatments were essentially damage free.
Comparisons of 2-Ethylhexyl Ester Formulations of 2,4-D: Chemistry and Bioefficacy
Authors: Mack RE , Roberts JR , Volgas GC
Published: April 2008

In field trials, two formulations of 2-ethylhexyl ester 2,4-D, having different solvent systems, were applied to various crop and weed species. HM-9625-A is a traditional 2,4-D ester formulation using aromatic solvents and emulsifiers. In HM-9625-B, the aromatic solvent was replaced by a co-formulation of methylated soybean oil and organosilicone surfactant. Determinations of crop or pasture phytotoxicity and weed efficacy were observed. Also, reduced rates of the co-formulated compound (HM9625-B), were compared to higher rates of the standard material (HM9625-A), to determine differences in activity between the compounds. There was no injury observed due to applications of either formulation at all rates tested, to wheat, oats, barley, corn, orchardgrass or tall fescue. Generally, the co-formulated 2,4-D provided equivalent to slightly greater weed control at reduced rate. The field trials were conducted in 1997, 1998 and 2000 at locations in the Midwest and Northeastern regions of the United States.
Droplet Size Affects Durability of Spray Deposits
Authors: Salyani M
Published: April 2008

Field observations of less residual pest control from some low-volume applications indicate that deposits generated by fine droplets may be more susceptible to rain wash-off and solar degradation as compared to deposits of larger droplets. This implies that, in addition to spray deposition, pesticide residue distribution may also be an important factor in the efficacy of pest control. The objective of the study was to determine the effects of the droplet size on rain washoff and solar degradation of fine and coarse spray deposits.

Two experiments were conducted in five replications. Spray solutions were applied at 102–735 μm droplets, using a droplet generating system. In the first experiment, spray solution of copper hydroxide was applied on plastic card targets. The targets were exposed to 0.6–7.5 mm rain, and the remaining deposits were quantified by copper colorimetry. In the second experiment, spray solution containing a fluorescent tracer was applied on plastic and acetate targets. Sprayed targets were exposed to 0–27 MJ/m2 of solar radiation. Samples of the targets were collected at different time intervals and spray residues were measured by fluorometry. Droplet distribution patterns were characterized on water-sensitive targets.

There were clear differences among distribution patterns of various droplet sizes. While fine droplets gave more uniform deposition than the larger droplets, they also were more susceptible to rain washoff. The amount of washoff increased with the rainfall and for any amount of rain, the targets with smaller droplets were washed off at a faster rate. Deposit degradation increased with the intensity of solar radiation, however, there was no difference in degradation rate of some smaller droplet sizes. Green plastic cards, simulating leaves, showed similar degradation trends as transparent acetate cards.
Investigation of Microstructure and Mechanical Properties of 18Cr-10Ni-Ti Steel Irradiated in the Core of VVER-1000 Reactor
Authors: Neustroev VS , Dvoretzky VG , Ostrovsky ZE , Shamardin VK , Shimansky GA
Published: April 2008

Investigations of the guide channel (Fe-0.08C-18Cr-10Ni-Ti steel) of the VVER-1000 reactor fuel assembly absorbing element were carried out. The channel was irradiated in the temperature range from 284 to 322 °C and damage dose ranging from 1 to 9 dpa.

In the microstructure examination the porosity was observed at temperatures of 308 °C and 310 °C at of 8 and 4.5 dpa, respectively.

The dose dependencies of the mechanical property characteristics of Fe-0.08C-18Cr-10Ni-Ti steel at test temperatures of 20, 300 and 450 °C were obtained. With the damage dose increasing, a decrease in the steel plasticity and an increase in hardness is observed at all test temperatures.

The obtained results were compared to those of investigations on Fe-0.12C-18Cr-10Ni-Ti steel irradiated in fast reactors. It was revealed that the temperature boundary 305–315 °C, at which the porosity appears, is nearly the same for steels irradiated in both types of reactors. However, hardening of steel irradiated in the fast reactor is higher than hardening in the thermal reactor under the same irradiation conditions (280–300 °C, 7–9 dpa).
The Role of Fine Defect Clusters in Irradiation-Assisted Stress Corrosion Cracking of Proton-Irradiated 304 Stainless Steel
Authors: Busby JT , Sowa MM , Was GS , Kenik EA
Published: April 2008

The influence of small defect clusters on irradiation-assisted stress corrosion cracking (IASCC) of austenitic stainless steels has been examined. A CP-304 SS alloy was irradiated with 3.2 MeV protons to 1.0 dpa at 360°C and then annealed for 45 min. to 1 h at temperatures ranging from 400–600°C. Dislocation microstructure was analyzed using both bright field and dark field techniques and cracking susceptibility was measured in an oxygenated water environment. Intergranular cracking was mitigated following annealing at 500°C/45 min. while only the smallest dislocation loops had been removed. Analysis of the slip step bands on the surface of deformed samples indicates that deformation mode may be important in determining cracking susceptibility. Low-temperature irradiation (< 75°C) was also used to create a high population of small defects without radiation-induced segregation. Samples were then annealed at 350°C for 8 or 15 min. to grow the dislocation loop microstructure, resulting in an irradiated hardness similar to the 1.0 dpa at 360°C case. No segregation was measured in the as-irradiated specimens. The change in hardness resulting from 0.3 dpa at 75°C was 73.8 kg/mm2, greater than that for 1.0 dpa at 360°C. Following annealing at 350°C for 8 min., the change in hardness was reduced to 60.8 kg/mm2, similar to 1.0 dpa at 360°C (65.3 kg/mm2). Samples were also strained to 29.6 % strain in an oxygenated water environment at 288°C. No cracking was observed on any specimen. The small defect damage may have been annealed during the constant extension rate test.
Martensitic Transformations in Neutron Irradiated and Helium Implanted Stainless Steels
Authors: Kadyrzhanov KK , Maksimkin OP
Published: April 2008

Results of experiments aimed at revealing the phase-structure stability as well as mechanisms of the mechanical property changes formation in austenitic chrome-nickel and manganese steels irradiated with high-energy nuclear particles and subjected to elevated temperatures are presented and discussed. Influence of the phase-structure transformations on radiation hardening and embrittlement of steels used in nuclear power industry is analyzed. Change in the experimentally determined “true” values of critical strains and peculiarities of the ά-phase initiation in deformed steels Cr18Ni9Ti, 12Cr18Ni10Ti as a function of temperature and deformation rate, type and fluence of the bombarding particles are discussed. Influence of irradiation on the martensitic structure morphology, critical γ→ά transformation parameters, and thermal effects accompanying the nondiffusion phase transformation is analyzed. The revealed effects are discussed in terms of the internal strength field changes due to thermal and radiation effects.
Evaluation of Irradiation Embrittlement of A508 Gr 4N and Comparison to Other Low-Alloy Steels
Authors: Wire GL , Beggs WJ , Leax TR
Published: April 2008

A508 Gr 4N has improved fracture toughness because of the addition of 3% nickel, compared to typical low-alloy steels which have less than 1% nickel. However, there is an expectation in much of the recent literature, based mostly on low-alloy steels with nickel below 1%, that irradiation embrittlement will increase with increasing nickel (Ni) content. In contrast, the raw irradiation test data show that ASTM A508 Grade 4N containing up to 3.7% nickel, 0.1% Cu and 0.01% P does not show enhanced irradiation embrittlement. Statistical analyses of the irradiation data were performed to enable more quantitative comparisons to other steels. The peak irradiation embrittlement of A508 Gr 4N is no greater than that of A508 Gr 2, a 0.7% Ni forging material tested under similar conditions with similar limits on Cu and P. At high dose (80 mdpa) the average embrittlement of A508 Gr 4N is slightly higher (about 33%) than the lower nickel materials A508 Gr 2, A533B and A302B with similar Cu and P. The irradiation temperature dependence of embrittlement in A508 Gr 4N is nearly the same as other low copper low-alloy steels tested over a wide range of temperatures. The shift in Charpy transition temperature (TTS) in A508 Gr 4N is due to radiation hardening, and the ratio of TTS to yield strength increase in 3 Ni steels is nearly identical to that observed for conventional low-alloy steels with lower nickel. Cu and P increased embrittlement in A508 Grade 4N steel, similar to that for A508 Gr 2 steels irradiated in surveillance tests.
Examination of Postirradiation Deformation Microstructures in F82H
Authors: Gelles DS , Schäublin R
Published: April 2008

The deformed microstructures of irradiated F82H uniaxial tensile specimens have been examined following irradiation in the High Flux Reactor (HFR) to 2.6 dpa at 327°C in order to identify controlling mechanisms. Deformation following irradiation is found to occur in poorly defined channels, causing formation of discrete steps at surfaces, similar to that in unirradiated steel. Deformation is by motion of individual a/2 〈111〉 dislocations.
Incubation Period for Void Swelling and Its Dependence on Temperature, Dose Rate, and Dislocation Structure Evolution
Authors: Surh MP , Sturgeon JB , Wolfer WG
Published: April 2008

Void swelling in structural materials used for nuclear reactors is characterized by an incubation period whose duration largely determines the utility of the material for core components. Significant evolution of the dislocation and void microstructures that control radiation-induced swelling can occur during this period. Thus, a theory of incubation must treat time-dependent void nucleation in combination with dislocation evolution, in which the sink strengths of voids and dislocations change in concert. We present theoretical results for void nucleation and growth, including the time-dependent, self-consistent coupling of point defect concentrations to the evolution of both void population and dislocation density. Simulations show that the incubation radiation dose is a strong function of the starting dislocation density and of the dislocation bias factors for vacancy and interstitial absorption. Irradiation dose rate and temperature also affect the duration of incubation. These features are in general agreement with experiments for high purity metals.
Kinetics of Helium Bubble Formation in Nuclear and Structural Materials
Authors: Schaldach CM , Wolfe WG
Published: April 2008

Neutron activation of most materials results in some generation of both helium and/or hydrogen. Other cases of helium generation are encountered in materials containing tritium, and in materials which are radioactive and undergo alpha-decay. Finally, materials in accelerators, spallation neutron sources, and nuclear fusion devices are subjected to energetic beams of protons or helium ions. In all these cases, helium may be retained within the materials employed, and helium bubbles form and grow. With the exception of tritium decay, radiation damage usually accompanies the helium formation. The rates of helium formation and radiation damage are traditionally stated in terms of the ratio of appm He to dpa (displacement per atom). When this ratio approaches or exceeds about 10 appm He/dpa, a profuse population of helium clusters and bubbles appears in the material when the temperature is high enough for helium migration to occur, with or without a concomitant formation of voids.

We present here kinetic models to describe the formation and growth of helium bubbles. We find that under constant helium generation rates, the nucleation occurs very rapidly over a very short period of time during which the helium concentration in solution peaks sharply. After this initial nucleation burst, the helium concentration in solution remains low as bubbles already present quickly capture newly generated helium. The evolution of the bubble density and average radius is shown to approximately follow a universal curve when a dimensionless time and dimensionless density are introduced. The scaling relationships involved in mapping experimental bubble densities onto the universal curve provide the means to extract a helium diffusion coefficient.

In nickel-containing alloys, the helium generation rate builds up gradually, delaying the formation of helium bubbles to higher doses. Depending on the helium to dpa ratio, void swelling can intervene in bubble formation and even suppress it.
Bubble Microstructures in Helium Injected Palladium Foils
Authors: Gelles DS , Causey RA , Hertz K , Cowgill DF , Schäublin R
Published: April 2008

Microstructural characterization of helium bubble distributions is provided for a series of palladium foils that were injected with 3He under varying conditions of dose, temperature and starting foil condition. Specimens were prepared in cross section and bubble layers ∼500 nm thick are found starting ∼300 nm from foil surfaces. Bubble densities and sizes were found to vary with foil microstructure and injection conditions, with larger bubbles formed on microstructural features such as sub-grain boundaries and nearer the surface. Most surprisingly, bubble sizes are found to be as small as 1 to 2 nm in diameter. Specimen preparation details and imaging issues for very small bubbles are discussed.
Heavy Ion Fluence Measurements Based on Radiation Effects Generated in CTA Foils
Authors: Peimel-Stuglik Z , Skuratov VA
Published: April 2008

The usefulness of cellulose triacetate (CTA) foils to measure heavy ion beam fluence was investigated. Two different CTA foils: FTR-125 Fuji dosimetric foil and Polish CTA-T technical foil, were examined. Ion beam irradiation (Ar, 155 MeV and Xe, 245 MeV) were performed on a 4-metre U-400 cyclotron operated in JINR, Dubna, Russia, and optical analysis — on a UV/VIS spectrophotometer Cintra-40 in INCT, Poland. Some results of gamma ray irradiation of CTA foils are included for comparison.

It was established that an increase of optical absorbance at 280 nm was strictly proportional to the fluences of the investigated ions for both kinds of foils. No postirradiation effects were observed. The results show that cellulose triacetate foils can be used for quick and easy measurement of ion beam fluences between 109 and 1011 ions/cm2 and also for evaluation of mean absorbed dose.
Effect of Ion Irradiation on Microstructure and Hardness in Zircaloy-4
Authors: Zu XT , Atzmon M , Wang LM , You LP , Wan FR , Was GS , Adamson RB
Published: April 2008

In studies of radiation effects on materials for reactor applications, it is desirable to identify irradiation methods that induce microstructural effects similar to those of neutrons, but at reduced time and expense. In the present study, 2 MeV protons were used to introduce up to seven displacements per atom in Zircaloy 4 at 350°C. The effect on the intermetallic precipitates, the formation of dislocation loops and hardness were investigated by analytical and high-resolution transmission electron microscopy (TEM). In addition, the precipitate evolution during 600 keV Ne ion irradiation at 350°C was monitored by in situ TEM. The results are compared with literature data for neutron-irradiated Zircaloy. While Ne irradiation leads to precipitate amorphization, no amorphization or chemical redistribution is observed in the proton irradiated sample. The dislocation-loop size and density in the Zr matrix of the proton-irradiated alloy are similar to those in the neutron-irradiated alloys.
Modeling Variability in Service Loading Spectra
Authors: Socie DF , Pompetzki MA
Published: April 2008

This paper describes a methodology for statistically extrapolating a single measured service loading history to the expected long-term service usage spectra. The measured time history first is processed into a rainflow counted histogram. Nonparametric kernel smoothing techniques are employed to convert the rainflow histogram of cycles into a probability density histogram. Once the probability density histogram is obtained, Monte Carlo methods are used to produce a rainflow histogram of any desired number of cycles. A new loading history then is reconstructed from the expected rainflow histogram, which can be combined with a probabilistic fatigue analysis to obtain an estimate of the durability of a structure. Obtaining an estimate of the loading spectra for a ground vehicle is difficult because there are many users, each with different service usage. The extrapolating methodology is extended to combine data from several users to obtain loading spectra that represent more severe users in the population.
Probabilistic Fracture Toughness and Fatigue Crack Growth Estimation resulting From Material Uncertainties
Authors: Farahmand B , Abdi F
Published: April 2008

A new approach is introduced which can evaluate fracture toughness of aircraft and aerospace alloys by using static parameters that are obtainable from full stress-strain curves available in the MIL-HDBK. With this approach, the energy absorption rates related to the plastic deformation at the crack tip and near crack tip are estimated and used to extend the Griffith theory of brittle fracture to fracture mechanics of ductile metals. An equation has been established that can define the critical crack length as a function of fracture stress. Having fracture stress and critical crack length on hand, the plane strain and plane stress fracture toughness can be calculated by applying the stress intensity factor equation. The calculated fracture toughness for 2219-T8, 2014-T6 aluminums, and Ti-6Al-4V titanium alloy was compared against the experimental test data generated from reliable sources. Excellent agreement between test data and the theory was found. When fracture toughness was calculated by this method, fatigue crack growth curves for the above-mentioned alloys were then generated and compared with test data. The threshold stress intensity factor value, ΔKth, in region I of the da/dN curve, was approximated by establishing a point on the Kitagawa diagram associated with the region of linear elastic fracture mechanics. Results of ΔKth values estimated by this method were in fine agreement with values observed for many materials in the NASGRO database. Two additional points were estimated in region II that enable to establish the Paris region. Probabilistic evaluation of fracture toughness and fatigue crack growth analysis considered a 5 to 10% coefficient of variation of material Kc, and Kth random variables.
A Methodology for Assessing Fatigue Crack Growth Reliability of Railroad Tank Cars
Authors: Zhao W , Sutton MA , Penã J
Published: April 2008

A methodology for assessing structural reliability of railroad tank cars undergoing fatigue crack growth is being developed. A three-degree-of freedom (3-dof) surface crack is employed to account for an asymmetric stress field existing at a fatigue critical location in tank car structures. A fatigue life prediction program using the Walker equation to account for stress ratio effects is developed for the 3-dof surface crack model. A component reliability problem is formulated as a limit state function and solved using a first-order reliability method along with importance sampling method within the commercial reliability software, STRUREL. The methodology is demonstrated using illustrative railroad tank car examples. The results show that: (a) failure probability, Pf, increases as tank car mileage increases; (b) welding residual stresses in the tank structure can significantly increase Pf ; (c) uncertainty in the stress amplitude also has a significant effect on Pf; and (d) the correlation between initial crack depth and initial crack aspect ratio is an important parameter.
Variable Amplitude Fatigue Crack Growth Using Digital Signal Processing Technology
Authors: Donald JK , George K
Published: April 2008

An automated variable amplitude fatigue crack growth system has been developed using digital signal processing (DSP) technology to provide waveform generation, command-feedback verification, and crack growth monitoring. The system is designed to interface with existing analog or digital closed-loop servo-hydraulic mechanical test systems. An important parameter in the control of variable amplitude testing is the effect of loading errors on the fatigue crack growth rate response. A damage parameter (г) has been incorporated to quantify the magnitude and effect of loading errors. In this paper, a FALSTAFF, Mini-TWIST, and truncated Mini-TWIST aircraft spectrum were applied to an M(T) crack growth sample to demonstrate the correlation between the damage parameter and fatigue life.
Multi-Mechanism Synergy in Variable-Amplitude Fatigue
Authors: Sunder R , Ashbaugh NE , Porter WJ , Rosenberger AH
Published: April 2008

Fractographic studies on Al alloys and a nickel-base super-alloy point to the combined action of three major load-interaction mechanisms in controlling crack growth under variable-amplitude loading. These are crack closure, residual stress, and crack front incompatibility. Crack front incompatibility attenuates crack tip response to applied load and can also increase crack closure stress. Notch root residual stress affects crack closure, while crack tip residual stress moderates environment-enhanced fatigue crack extension. The latter effect disappears in vacuum. Experiments designed to isolate the effect of individual mechanisms provide a framework to model their synergistic action, consistent with microscopic observations of crack growth bands in variable amplitude fatigue.
Fatigue Design and Experimentations with Variable Amplitude Loadings in the Automotive Industry
Authors: Thomas JJ , Bignonnet A , Perroud G
Published: April 2008

The paper presented gives an overview of the various problems that should be addressed to take into account the variable amplitude loadings undergone by the car components. One of the most important point is that all the steps of the design procedure (including experiments and computations) should be consistent with each other in terms of damage. For some reasons (efficiency, robustness, capitalization,…), variable amplitude loading may be converted into damage equivalent loadings. Tools such as cycle counting ,damage summation including the mean value effect and rainflow extrapolation are therefore necessary. The paper shows how single component and full scale tests are related with both customer and test track measurements, and how these experimental data are correlated with predictive fatigue computations, including the statistical aspects for reliability purpose. The paper will illustrate that if the consistency mentioned above is guaranteed, then the variable amplitude fatigue computation (such as the ones proposed in commercial codes) is no longer useful. It requires therefore an analysis of the material behavior under variable amplitude loadings in the automotive context. One of the most important advantage of this approach is that under simple assumptions, the computations can be realized before any prototype could be driven on a track. It allows to shorten the developments delays. These assessments will be illustrated by various examples showing how the loadings are analyzed in the measurements stages, and how they are applied in the experimental and computation stages.
Comparison of the Rain Flow Algorithm and the Spectral Method for Fatigue Life Determination Under Uniaxial and Multiaxial Random Loading
Authors: Łagoda T , Macha E , Niesłony A
Published: April 2008

This paper presents the strain energy density parameter used for fatigue life calculation under random loading by two methods. The first method is based on schematization of energy parameter histories with the rain flow algorithm. The other one is based on moments of the power spectral density function of the energy parameter. The experimental data of fatigue tests of 10HNAP steel under constant amplitude and random uniaxial loading with non-gaussion probability distribution, zero mean value, and wide-band frequency spectrum used for comparison of the rain flow algorithm and the spectral method gave satisfactory results. Next, histories of the random stress tensor with normal probability distribution, wide-band frequency, and zero mean values corresponding to biaxial tension-compression, combined tension with torsion and triaxial loading with various correlation coefficients were generated, and the lifetime was calculated. It has been observed that both methods of fatigue life determination give almost the same results.
Modeling of Deformation During TMF-Loading
Authors: Affeldt EE , Hammer J , Cerdán de la Cruz L
Published: April 2008

The deformation behavior of two extremely different nickel base alloys under cyclic loading is reported and discussed with respect to the underlying micro-structural mechanisms. One is a high strength cast single crystal alloy and the other is a wrought carbide strengthened alloy with comparably low yield strength showing pronounced plasticity during cyclic deformation. A procedure for modeling of the deformation behavior is described that take this mechanism into account. It implies elastic deformation, yielding, and relaxation. For the low strength alloy, cyclic hardening is additionally accounted for. The modeling procedure, the evaluation of the necessary parameters from isothermal tests, and the predicted results for isothermal and anisothermal loading are compared with experimental results.