bluuebunny/crossref_metadata_2025 huggingface dataset:
Derivation of Flight-by-Flight Spectra for Fighter Aircraft
Authors: Kaplan MP , Reiman JA , Landy MA
Published: March 2009

The importance of predicting the durability and damage tolerance capability of aircraft structures has underscored the need to derive a realistic flight-by-flight stress spectrum. This stress spectrum is generated from an analysis of the projected usage (mission profiles), combined with load factor exceedance curves that are obtained either from MIL-A-8866B or recorded data. The mission profiles are defined by the using command (the organization which flies the aircraft) and contain such information as mission length, number of times flown per aircraft lifetime, fuel load, weapons configuration, and a breakdown of the mission by segment, for example, takeoff, climb, cruise, descent, etc.

This paper describes two different approaches for obtaining load factor exceedance curves: (1) MIL-A-8866B and (2) data recorded from a different aircraft flying a similar mission. In the first example, the spectrum is derived for a ground-attack fighter that is in the design phase (that is, has never flown) and in the second case, the spectrum is derived for an aircraft that has already been built but is being used in a new mission (flight demonstration squadron). In this second case, a large amount of recorded load factor exceedance data exists from a different aircraft flying the same mission. Using either exceedance curve approach, these data are combined with the mission profile data to develop a stress-exceedance curve for each mission. The stress-exceedance information then is input to a computer program, along with some additional data such as the number of times a given mission is flown. The computer program first generates a random mission ordering and then randomly orders the stresses within each mission. The final result is a random flight-by-flight stress spectra suitable for use in performing damage tolerance and durability analyses and tests.
Factors Influencing Stage I Crack Propagation in Age-Hardened Alloys
Authors: Wilhelm M , Nageswararao M , Meyer R
Published: March 2009

This paper reviews some recent experimental results on age-hardened A1-5Zn-1Mg, A1-4Cu, and Cu-2Co alloy single crystals. Experiments were performed with unnotched specimens to study their cyclic deformation behavior and with notched specimens to investigate the crack propagation in Stage I. Since at present no quantitative statement of the formation of persistent slipbands in age-hardened alloys is available, we choose to represent this important microscopic activity indirectly in terms of the amount of cyclic hardening. It is shown that lowering the test temperature and, in the aluminum alloys, changing the type of alloy additions from zinc plus magnesium to copper have qualitatively the same influence of impeding the formation of persistent slipbands and of homogenizing their distribution. The crack propagation experiments show that the same factors decrease the velocity of and the tendency to crack propagation in Stage I. In the A1-5Zn-1Mg alloy the presence of water vapor in the environmental atmosphere, which increases the Stage I crack propagation velocity at 50 Hz, was found to prevent crack propagation in Stage I if the frequency is lowered to 5 Hz, whereas in dry nitrogen gas Stage I crack propagation is not affected by a frequency change. The experiments show that easy formation of persistent slipbands and deformation highly localized in these bands are a prerequisite for the occurrence of extended slipband (Stage I) cracking. The influence on State I crack propagation exerted by the parameters considered is attributed to their effect on the formation of the persistent slipband ahead of the crack tip in which the crack propagates.
Direct Observation and Mechanism of Fatigue Crack Propagation
Authors: Kikukawa M , Jono M , Adachi M
Published: March 2009

Fatigue crack propagation tests were carried out by using a specially designed testing apparatus in a scanning electron microscope. A grain-oriented silicon iron was used as a testing material and it was found that a nearly plane-strain state could be realized up to the specimen surface by selection of the loading axis to the specific orientation of the material. From the sequential observations of crack opening and closure behavior the mechanism of fatigue crack propagation by Mode I opening was confirmed to be an alternating slipping-off process at the crack-tip apex.

Quantitative evaluation of a relationship between crack-tip opening displacement and crack growth length is given by considering the slip direction, crack tip angle, and the amount of rewelding. Also, a relation between crack growth length and slipped length in Mode II fatigue cracks is discussed.
Direct Observations—The Essential Ingredients for Discovering Fundamental Mechanisms of Fatigue
Authors: Fong JT
Published: March 2009

Through two stories from the history of medical science, both related to the theory of bloodletting as a treatment for inflammatory diseases, the importance of direct observations and the use of a numerical scheme in all scientific work, including fatigue mechanism research, are illustrated. Brief remarks on two specific questions arising from two earlier sessions on direct observations are inserted. The two questions are: (1) What is the connection between direct observations and quantitative microscopy? (2) What could fatigue design and testing engineers learn from the direct observations of fatigue damage at microscopic levels? A cautionary note on the temptation to extrapolate from insufficient direct evidence of fatigue damage is also included.
A Review of Fatigue Fracture Topology Effects on Threshold and Growth Mechanisms
Authors: Gerberich WW , Moody NR
Published: March 2009

A review of fatigue crack propagation and near-threshold surfaces in α/β titanium and iron-base alloys reveals at least 10 types of alternate fracture processes, compared with the more common striation process. Microstructural influence was found in all materials with interactive effects of temperature, frequency, and environment. At low temperatures, alternate cleavage modes produce crack growth exponents that increase in a consistent way with either a decrease in test temperature or a decrease in fracture toughness. Such phenomena may be understood in terms of void-induced fracture strain concepts or, alternatively, with strain-rate sensitivity concepts applied to ductile ligaments. Factors of two to three increase in threshold are shown to exist through microstructural modification of either Widmanstätten colony or grain size. A semicohesive ligament zone based upon a modified Dugdale-Barenblatt model is shown to predict both of these microstructural effects. It is emphasized that such models are in their formative stages and require additional modification to include overload, R-ratio, and strain-hardening concepts.
A Mechanism of Intergranular Fracture During High-Temperature Fatigue
Authors: Min BK , Raf R
Published: March 2009

We have studied the mechanism whereby grain boundary sliding in the crack-tip region causes a triple-junction fracture type of grain boundary damage. This results in an increase in the rate of fatigue crack propagation. It is argued that since grain boundary sliding is a strain rate sensitive process, sliding damage is possible only if the strain rate is below a critical value; an expression for the critical strain in terms of the microstructure and the yield strength is obtained. It is shown, by theory and experiment, that the maximum damage condition is achieved when the tensile-going strain rate is below the critical strain rate whereas the compressive-going strain rate is above the critical value. If both strain rates are below the critical value (enough if they are unequal), then damage due to sliding in one direction is removed by sliding in the reverse direction, and the increase in crack growth rate is not observed.
Quantitative Stereological Methods for Analyzing Important Microstructural Features in Fatigue of Metals and Alloys
Authors: Underwood EE , Starke EA
Published: March 2009

This paper reviews the practical aspects of extracting quantitative microstructural data from microstructures of fatigued metals and alloys. In addition to the basic stereological information needed to characterize the essential geometrical elements of the structure, special methods are developed and described for quantifying more subtle effects. Thus, elongated structures, lamellar systems, gradients, and locational characteristics of particles are considered with respect to the fatigue process and its interactions with the microstructural features.
Fatigue Damage Mechanisms in Composite Materials: A Review
Authors: Stinchcomb WW , Reifsnider KL
Published: March 2009

Some of the earliest investigations concluded that the basic mechanisms of fatigue in composites and fatigue in homogeneous materials differ greatly. Instead of the initiation and propagation of a fatigue crack traditionally identified with homogeneous materials, fatigue in composites consists of various combinations of matrix, fiber, and interfacial cracks and debonds to form a very complex damage state. Furthermore, fatigue mechanisms are dependent upon a number of parameters, including the material system, stacking sequence of plies, geometry, stress state, and environment.

The variety of damage modes, the complexity of their interactions, and the subsequent effect on engineering properties make it difficult to interpret fatigue damage in order to define and predict fatigue failure or lifetime for composite materials. A brief synopsis of the current knowledge of fatigue damage mechanism in fiber-reinforced composite materials is presented along with some suggestions to help advance the level of understanding of the fatigue response of composite materials.
Fatigue Mechanisms in Nickel and Cobalt-Base Eutectic Composites
Authors: Stoloff NS , Duquette DJ
Published: March 2009

The high-cycle fatigue behavior of several nickel and cobalt-base eutectic composites is described. Major test variables include test temperature, frequency, alloy composition, and microstructural modifications induced by postsolidification heat-treatments. Lamellar γ/γ′-δ type eutectic alloys are shown to have superior fatigue resistance to the fibrous alloys, with regard to both total life and crack propagation rates, provided that the microstructures are perfectly aligned. Cracking at 25°C in all alloys tends to be along crystallographic planes (Stage I cracking), although striations associated with Stage II propagation were occasionally observed in solution-treated Nitac. At 825°C there is no evidence of Stage I crack growth or Cotac or Nitac. A pronounced frequency effect occurs in Nitac at 825°C (0.7 Tm) in vacuum, suggesting a creep-fatigue interaction.
Model for Prediction of Fatigue Lives Based Upon a Pitting Corrosion Fatigue Process
Authors: Hoeppner DW
Published: March 2009

The pitting corrosion fatigue process is postulated to be a possible environment/deformation synergism that might explain the initiation of Mode I cracking in materials subjected to the combined action of environment and alternating strain. A conceptual model for such a process is presented that involves utilization of an empirical pitting rate curve and a Weibull fit of the appropriate crack growth data. An experimental technique for observing the growth of pits under cyclic loading is described. Some shortcomings of the conceptual model and needs for additional research are discussed.
Delrin as a Material for Joint Prostheses—A Review
Authors: Dumbleton JH
Published: March 2009

Delrin acetal resins are thermoplastic polymers manufactured by the polymerization of formaldehyde. The use of Delrin in total hip prostheses was first suggested in the mid-1960s. The attraction of Delrin is that the creep resistance is ten times that of ultrahigh molecular weight polyethylene, the most usually used plastic material. In addition, Delrin is about five times harder than ultrahigh molecular weight polyethylene and thus will resist the abrasive action of bone chips and acrylic cement particles.

Since 1970, Delrin acetal polymer has been used in the Christiansen total hip prosthesis and in the Christiansen endoprosthesis. Up to the end of 1977, approximately 7000 surgical procedures had been carried out with the prosthesis. The results have been very good. Prostheses removed for cases of infection or loosening have not shown wear on the articulating Delrin components. Furthermore, histological studies of the surrounding tissue show a benign tissue response similar to that seen around polyethylene implants. The Christiansen prosthesis has been recommended as a Class II device by the U.S. Food and Drug Administration.

Studies on the performance of Delrin in the Christiansen total hip prosthesis have been carried out in a hip joint simulator at the University of Cincinnati. These investigations showed that the Delrin wear rate was similar to the wear rate of polyethylene in the Charnley or Charnley-Müller hip prosthesis configuration. In addition, studies on the simulator showed that although acrylic cement fragments caused deformation and scarring of polyethylene when entrapped between the joint surfaces, a similar phenomenon did not occur for Delrin.

The mechanical properties of Delrin have been investigated over many years, and a comparative table is shown, demonstrating the superiority of Delrin over ultrahigh molecular weight polyethylene, in relation to hardness, creep resistance, and strength.

Wear studies on Delrin in the laboratory have been carried out at several locations. The wear of Delrin has been shown to depend upon the test environment, the wear rate being lower with blood plasma as a lubricant than with distilled water. There is agreement on this between tests carried out at the University of Cincinnati and at the Royal National Orthopaedic Hospital in London. However, tests carried out at the Orthopedics Department of the University of California at Los Angeles (UCLA), show that the wear rate of Delrin does not depend upon the liquid test environment, although much higher wear rates will be obtained if the wear test is carried out under dry conditions. However, the tests at UCLA indicate that the wear rate of Delrin is acceptable for total hip prosthesis end use.

The results, taken in conjunction with the clinical findings, suggest that Delrin performs well in the Christiansen total hip prosthesis configuration. Work is at present under way to study the use of Delrin for a tibial plateau in an unconstrained knee prosthesis.
Degradation of Ceramic Materials in Physiological Media
Authors: Drummond JL , Simon MR , Brown SD
Published: March 2009

The literature apropos of the degradation of ceramics and ceramic-coated metal systems in physiological media is reviewed. Both in vitro and in vivo studies are involved. Generally, ceramics suffer losses of mechanical strength with time in physiological media, and ceramic-metal bonds lose adherence. Carbons seem to be exceptions to this rule. The theory with regard to the mechanisms associated with the said degradation is still in a primitive stage of development. The development of more meaningful experiments than those now in vogue is needed. Effects of material character and the nature of the environment-material interface upon the strength degradation must be investigated.
Fracture and Corrosion in Stainless Steel Total Hip Replacement Stems
Authors: Dobbs HS , Scales JT
Published: March 2009

Thirty-two stainless steel Charnley total hip replacements were examined; 23 of these had been removed from patients after a period of implantation, twelve as a result of fracture. All the components were forgings produced by the same manufacturer. The majority of the components (Type 1) were about eight years old and were manufactured from air-melted EN58J stainless steel with a maximum permitted carbon content of 0.06 percent (this steel is similar to Type 316 stainless steel). The remainder (Type 2) were about four years old and were manufactured from vacuum-melted material with a maximum permitted carbon content of 0.03 percent (similar to 316L stainless steel). The following results were noted:

1. The material in the Type 1 implants was often sensitized and contained many inclusions. The material in the Type 2 implants was never sensitized and contained fewer inclusions but had a larger grain size than the Type 1 material.

2. In both types of implant, fracture initiation was not obviously associated with corrosion, and the influence of the patient' weight and activity seemed to be more important than that of metallurgical defects.

3. In the Type 1 components, intergranular corrosion occurred in sensitized regions. and the severity of the corrosion increased with the period of implantation. The incidence of corrosion of all kinds was 35 percent for an average implantation time of 46 months. In the Type 2 material, pitting corrosion occurred, but the sample size was too small to allow a meaningful estimate to be made of the incidence of this kind of corrosion.

4. Other surface markings were observed, including fretting due to abrasion by acrylic cement.

5. It is the authors' opinion that the main consequence of corrosion may be an eventual undermining of the integrity of the clinical procedure rather than the destruction of the component itself.
Quantification of Noise from Stationary Sources
Authors: Jackson T , Lyon HH
Published: March 2009

In the measurement and quantification of noise emitted from a stationary source, one has a choice of a multitude of descriptors and methodologies. Owing to the existance of one or several “sub-sources” of either the stationary or mobile type within the physical confines of many of the total stationary sources, one is obliged to consider each source as somewhat unique and modify his measurement methodology accordingly. This paper will deal with some of the problems encountered in obtaining an accurate set of descriptors in each case and in using these descriptors to predict annoyance due to a similar facility in a different location or due to changes made at an existing facility.
Highlights of the Guidelines for Environmental Impact Statements with Respect to Noise
Authors: Johnson DL
Published: March 2009

At the request of the U.S. Evnironmental Protection Agency (EPA), the National Academy of Sciences-National Research Council Committee on Hearing, Bioacoustics, and Biomechanics (CHABA) has developed and recently published guidelines for preparing environmental impact statements (EIS) on noise. The document contains guidance on the assessment of general audible noise and criteria to describe the environmental impact of vibration, infrasound, and high-energy type impulses. The yearly average day-night sound level outdoors is the recommended measure for the general audible noise environment. One of the key concepts introduced is the single number quantification of the overall noise impact. This single number is approximately proportional to the total number of persons that would report to be highly annoyed due to the residential yearly day-night average sound levels. The implications of such a single number descriptor, as well as other key features of the guidelines, are discussed.
Technical Considerations in Federal Regulation of Aircraft Noise at the Source
Authors: Tedrick RN
Published: March 2009

With the adoption in 1969 of the Federal Aviation Regulations, Part 36 (FAR), the Federal Aviation Administration (FAA) embarked upon a program to quantify and to limit the noise impact of the nation's civil air fleets. Since that original adoption, several amendments have been issued to (a) improve or better standardize the measurement of airplane noise, (b) redefine the descriptor-effective perceived noise level, (c) lower the permissible noise levels, and (d) require application of the standard to other airplanes. This paper reviews the technological basis for these standards, the public process by which they are promulgated or amended, and how thev relate to the prediction and alleviation of community noise.
Environmental Protection Agency's Regulatory Requirements for Wildlife Toxicity Testing
Authors: Akerman JW
Published: March 2009

The Environmental Protection Agency (EPA) has broad and flexible authority under the Federal Insecticide, Fungicide, and Rodenticide Act (FIFRA). Under FIFRA, EPA determines the pesticides that may be registered and for what uses. Scientific data and knowledge serve as the basis for determinations of unreasonable adverse effects. Three elements are contained in the environmental hazard assessment: determination of toxicity, determination of fate and exposure, and the integration of the two into a determination of hazard. Basic wildlife testing requirements include an avian dietary LC50 on two species, an avian single-dose oral LD50, and a rat single-dose oral LD50. Additional testing requirements for avian and mammalian wildlife include reproduction, pen field, and full-field studies. The EPA requirements are arranged in a tier or sequential fashion. The simple short-term laboratory studies are required at the first level for all manufacturing-use products and all formulated products intended for outdoor application.
Dietary Toxicity Tests with Mallards, Simulating Residue Decline of Chlorpyrifos and Avoidance of Treated Food
Authors: Kenaga EE , Fink RJ , Beavers JB
Published: March 2009

Dietary 11-day toxicant feeding tests were used to determine the effects of chlorpyrifos on repellency, lethality, food intake, and growth responses by mallards. Avoidance of food was noted at all concentrations tested (56 to 1124 ppm) with consequential decreases in weight growth. When an option between treated and untreated food was available, very little chlorpyrifos was consumed. Tests with dietary concentrations of chlorpyrifos simulating approximately the daily five-day half-life residue rate of decline on foliage treated with chlorpyrifos were compared with tests run under standard conditions where dietary concentrations were held constant throughout the 11-day toxicant feeding period. Initial concentrations resulting in LC50's for these tests were 644 and 357 ppm, respectively. These comparisons indicate that results from standard LC50 tests have a considerable added safety factor for compounds with a short residue half-life.
Efficacy and Safety of Diphacinone as a Predacide
Authors: Savarie PJ , Hayes DJ , McBride RT , Roberts JD
Published: March 2009

Research to assess the use of diphacinone as a predacide was divided into three primary phases: (1) acute oral toxicity tests with laboratory (captive) and free-ranging coyotes (Canis latrans); (2) residue analysis in tissues from coyotes killed by diphacinone; and (3) secondary toxicity tests with diphacinone meat baits fed to male albino rats (Rattus norvegicus) and golden eagles (Aquila chrysaetos). The LD50 with 95 percent confidence limits in captive coyotes was 0.6 (0.3 to 1.2) mg/kg. Free-ranging coyotes were captured, treated, and released to determine if efficacy was different from captive animals. Each was equipped with a mortality transmitter and tracked for a minimum of 21 days. The statistical method was not appropriate to calculate an LD50 in free-ranging animals; however, there appeared to be no major differences in toxicity as compared with captive animals. One male free-ranging coyote survived a dose of 2.5 mg/kg and one male captive coyote survived a dose of 1.25 mg/kg. These data indicate high individual variation in the toxic response to diphacinone. Time to death did not differ between the two groups; that is, free- ranging coyotes averaged 9.6 days (range 8 to 16) and captive animals averaged 10.4 days (range 6 to 17). Secondary toxicity tests were conducted with male albino rats fed a meat (muscle tissue) bait for 6 days from captive coyotes killed with diphacinone. The highest diphacinone residue in these baits was 0.5 ppm and four of eight rats that fed upon it died. Hence, there is a secondary hazard to susceptible animals that feed repeatedly on tissue containing at least 0.5-ppm diphacinone. In most animals the small intestine, liver, or kidney contained more than 0.5 ppm, and these tissues have a higher potential for secondary toxicity than muscle. Seven golden eagles were fed sheep meat containing 2.7-ppm diphacinone as the sole source of food in 5- and 10-day feeding tests. All eagles survived, but various degrees of toxicity were noted.
Determination of Microbial Heterotrophic Biomass Production by Sulfate Uptake Measurement
Authors: Monheimer RH
Published: March 2009

In aerobic waters, the uptake of sulfur by microorganisms should, theoretically, reflect their uptake of carbon. Studies with pure cultures of bacteria suggest that sulfate sulfur uptake follows the kinetics of organic carbon uptake and, also, that sulfate sulfur is the only significant source of sulfur in natural microbial biomass production. Sulfate uptake should, therefore, useful for measuring microbial heterotrophy. However, partitioning photosynthetic from heterotrophic sulfate uptake is complicated, since dark sulfate uptake cannot necessarily be interpreted as heterotrophy. Ongoing studies with axenic cultures suggest that a relationship between primary production and sulfate uptake exists, thereby potentially allowing the calculation of heterotrophy in terms of the construction of sulfur biomass. Such calculations, although preliminary, are presented.
Moisture Diffusion Analysis of Microstructure Degradation in Graphite/Expoxy Composites
Authors: Leung CL , Dynes PJ , Kaelble DH
Published: March 2009

Directional diffusion coefficients, that is, D1, D2, and D3, for the principal axis i = 1, 2, 3 of a unidirectional fibrous composite were determined by moisture absorption measurements. It was shown that the initial moisture absorption of a cured dry composite is non-Fickian and may relate to microstructural relaxation of internal stresses.

Moisture effusion rates of the specimens were also evaluated. Absorption-desorption kinetics over several cycles showed that there exists a damage mechnism in the composite which enhances moisture uptake from the dry state but does not enhance moisture release from the water-equilibrated state.
Influence of Load on the Magnitude of the Life Exponent for Rolling Bearings
Authors: Lorösch H-K
Published: March 2009

Extensive realistic tests to determine rolling bearing life have previously indicated that the exponent p in the well-known formula Ln = (C/P)p is a constant, and various institutes of technology have agreed that for ball bearings in particular this constant p = 3. Acceptance of this constant means that even under low load conditions a finite life is always to be expected at rolling contact surfaces. However, the classic theory of the strength of materials states that metals, especially steel, have a virtually unlimited life under a cycling load below a defined level. Recent tests on rolling bearings confirmed that under low loads and with elastohydrodynamic lubrication there is no material fatigue, thus indicating that under such conditions bearing life is practically unlimited. The recent tests further indicate that surface damage caused by particles entering a rolling bearing is a much more important factor in limiting bearing life than had previously been believed.
Analysis of Sets of Two-Parameter Weibull Data Arising in Rolling Contact Endurance Testing
Authors: McCool JI
Published: March 2009

Frequently in conducting rolling contact endurance tests, several small samples are subjected to some kind of “treatment.” It is shown herein that if the treatment affects the rating life but not the Weibull shape parameter the data can be analyzed as a set rather than as individual samples, with considerable improvement in the precision with which the rating lives can be estimated.

Methods and supporting tables are given for the detailed analysis of sets of such data under the assumption that they represent censored data samples drawn from two-parameter Weibull populations.

The complete analysis consists of the following: (a) a test for the equality of shape parameters among the populations, and, when a common shape parameter is found to be plausible, (b) two tests for the equality of scale parameters or any fixed percentile, (c) an interval and bias-corrected point estimation of the common shape parameter and the tenth percentiles of the individual groups, and (d) a procedure for assessing which of the populations differ in their scale parameter and, hence, any percentile values.

The numerical values of key percentage points of the relevant distributions required for carrying out the analyses cover the range from k = 2 samples of size n = 5, censored at the third (r = 3) failure, to k = 5 and n = r = 30. As an illustration, the analyses are applied to two sets of rolling contact endurance data obtained with various steel materials fabricated into cylindrical rod and ball test specimens.

Two procedures for the selection of sample size are discussed, and illustrative examples are given of their use.
Crack Propagation Measurements on Glass: A Comparison Between Double Torsion and Double Cantilever Beam Specimens
Authors: Champomier FP
Published: March 2009

A simple and rapid method of measuring crack propagation in glass was sought. Double torsion (DT) and double cantilever beam (DCB) specimens that allow KIc values as well as (K, V) diagram determinations were tested successively, using relatively large testpieces (250 by 100 by 6 mm).

In the case of DT specimens, it is shown that relaxation experiments do not require the prior determination of specimen compliance. Excellent reproducibility thus is obtained. The technique is easy to master, but the crack front profile is not taken readily into account.

Relaxation of DCB specimens reveals the important role played by the specimen compliance compared to the testing machine compliance. Experiments are not conducted as easily as in the previous case.

In both cases, it is shown that the minimum speed that can be achieved practically during a relaxation experiment on glass is of the order of 10 −7 ms−1.

Results were obtained on float glass in ambient air. They are in satisfactory agreement and compare favorably with published data.
Fracture from Controlled Surface Flaws
Authors: Petrovic JJ , Mendiratta MG
Published: March 2009

The use of controlled surface flaws to examine fracture properties of brittle materials is reviewed. Surface flaws are introduced by microhardness indentation. Such flaws are semi-elliptical in shape, with dimensions dictated by the indentation load.

A single flaw of proper size placed on the tensile surface of a conventional four-point bend specimen initiates fracture because it is the “worst flaw” in the specimen. Presence of the flaw reduces both the fracture strength and its associated scatter. Because controlled surface flaw dimensions are generally visible on the fracture surface, the critical stress intensity factor, KIc , may be calculated using fracture mechanics analyses for surface flaws in bending.

Such a fracture mechanics test is experimentally convenient, adaptable to testing in severe environments, and requires a relatively simple test specimen geometry. Also of importance is the fact that the fracture flaw dimensions are close to those of the natural flaws in the material. For silicon nitride (Si3N4) and silicon carbide (SiC) the technique has been employed to determine KIc at room and elevated temperatures, as well as under dynamic loading conditions. It has also been used to study slow crack growth, environmental effects, and mixed-mode fracture in these materials. Disadvantages of the controlled surface flaw technique as well as potential new applications are discussed.
Effect of Irradiation on the Strength, Ductility, and Defect Sensitivity of Fully Recrystallized Zircaloy Tube
Authors: Pettersson K , Vesterlund G , Andersson T
Published: March 2009

The effect of irradiation on the strength, ductility, and defect sensitivity of recrystallized Zircaloy has been investigated. Plane strain burst specimens were irradiated to fast-neutron fluences between 2.4 × 1024 and 10.8 × 1024 n/m2, E > 1 MeV. A few of the specimens contained well-characterized internal surface flaws. It was shown that the effect of fluence on yield stress could not be described by the theoretical relationship σ=σ0+A[1−exp(−Bφt)]1/2. As an alternative the empirical relation σ=σ0+A(φt)1/n could be used to describe the result. It was found that irradiated Zircaloy is very sensitive to defects with pinhole failures occurring after very small plastic strains. The defect sensitivity could be explained as a combination of the loading conditions and the absense of strain hardening in the irradiated material.
Zirconium Cladding Deformation in a Steam Environment with Transient Heating
Authors: Chapman RH , Crowley JL , Longest AW , Hofmann G
Published: March 2009

Zircaloy-4 cladding is being tested under loss-of-coolant accident (LOCA) conditions to determine its deformation behavior and to provide data for verification of analytical models. Data obtained thus far from 34 single-rod tests imply less ballooning, and consequently less flow restriction, than would be predicted from earlier data.

The instrumented simulators, consisting of unirradiated Zircaloy-4 cladding with an internal heater to simulate fuel pellet heating, are tested to failure in superheated steam over a wide range of internal pressures at a temperature increase rate of about 28°C/s. Cladding surface temperature and internal pressure data are recorded during the transient and deformation measurements are obtained posttest.

An analytical expression is given for the burst temperature as a function of burst pressure. The experimental results show excellent correlation between cladding deformation and surface temperature distribution. Deformation is extremely sensitive to small temperature variations.
Variation in Response to Methylmercury by Killifish (Fundulus heteroclitus) Embryos
Authors: Weis J , Weis P , Heber M
Published: March 2009

Some female killifish (Fundulus heteroclitus) from Montauk, N.Y., produce eggs that are much more resistant to the craniofacial, cardiovascular, and skeletal effects of 0.05 ppm methylmercury than eggs of other females. The following relationships were observed in studying 128 batches of eggs from 85 females fertilized by 35 males.

Batches of eggs with a high percentage of noncleaving eggs (NCEs) tended to be most susceptible. Tolerance was also associated with the relation of the date to the lunar spawning cycle and with the number of dorsal fin rays in the females; fish that had ten fin rays produced no unaffected batches, whereas those with eleven or twelve rays produced eggs ranging from very tolerant (unaffected) to very susceptible. A weaker correlation with female weight was seen. Because of the importance of the percentage of NCEs in determining the tolerance of a batch of eggs, the data were reanalyzed after removing all those batches with high rates of (>35 percent) NCEs. This revealed a strong association of tolerance with the stickiness of the eggs in that batches which were very sticky tended to be more resistant. Correlations were also seen with female length and fecundity. No correlations were seen with any measured traits of the males.
International Study on Artemia XXII: Nutrition in Aquatic Toxicology—Diet Quality of Geographical Strains of the Brine Shrimp, Artemia
Authors: Beck AD , Bengtson DA
Published: March 2009

A reference and four geographical strains of brine shrimp (Artemia spp.) nauplii were evaluated as diets for the larvae of a marine fish, the Atlantic silverside (Menidia menidia). The survival of fish fed the various strains was significantly different and ranged from 82 to 57 percent.

Previous related studies had evaluated five other geographical strains fed to both fishes and invertebrates utilized in toxicological studies at the U.S. Environmental Protection Agency laboratory in Narragansett, R.I. Significant differences in survival and growth, related to diet, were also found in these species.

The effects on survival and growth of M. menidia are related to the size of the nauplii.

Use of a standard geographical strain of Artemia is recommended for the diet of aquatic animals utilized in toxicological studies.
Prediction of Biological Availability of Organic Chemical Pollutants to Aquatic Animals and Plants
Authors: Lockhart WL , Metner DA , Blouw AP , Muir DCG
Published: March 2009

Rainbow trout fry, chironomid larvae, and duckweed plants were exposed to a series of Carbon-14(14C)-labeled compounds in different water types in order to establish whether the water type influences the accumulation of compounds in the test organisms. Fish, insects, and plants consistently accumulated compounds less efficiently from river water than from dechlorinated city water, Suitable regression equations were found empirically to describe the accumulation of compounds in organisms, and the best equations for prediciting the accumulation of methoxychlor were presented. The effect of the water type could not be attributed to the specific chemical components in each water type. Sorption to suspended solids was thought to contribute to the differing efficiencies of uptake but not to fully explain the phenomenon. When methoxychlor was sorbed to celite particles prior to its presentation to organisms, nonfilter feeders accumulated methoxychlor much less efficiently than when this pesticide was presented as an emulsifiable formulation.
Development of Water Quality Criteria for Ammonia and Total Residual Chlorine for the Protection of Aquatic Life in Two Johnson County, Kansas, Streams
Authors: Hazel RH , Burkhead CE , Huggins DG
Published: March 2009

A study was conducted to determine water quality criteria for ammonia and total residual chlorine (TRC) for the protection of aquatic life in two streams in Johnson County, Kan. The test streams selected were Mill and Cedar Creeks. The parallel streams flow into the Kansas River and share similar watershed characteristics. However, unlike Mill Creek, Cedar Creek does not receive sewage treatment plant effluents.

Species indigenous to the streams were collected, and 96-h acute toxicity tests were conducted with ammonia and TRC. Following the laboratory work, a test was conducted in Cedar Creek whereby ammonia was introduced for 24-h. Test organisms were placed in cages in the stream, and mortalities were observed throughout the test period.

Based on this research and other existing evidence, the conclusion was reached that if un-ionized ammonia concentrations in the two streams do not exceed 0.07 mg/litre un-ionized ammonia expressed as nitrogen (NH3-N) as a 24-h average, or 0.4 mg/litre NH3-N at any time, aquatic life in the two streams will suffer no adverse effects. Nor will these organisms be adversely affected by total residual chlorine concentrations that do not exceed 0.02 mg/litre TRC as a 24-h average, or 0.03 mg/litre TRC at any time.
Control of Microstructure by the Processing Parameters and Chemistry in the Arctic Line Pipe Steels
Authors: Ouchi C , Tanaka J , Kozasu I , Tsukada K
Published: March 2009

With the increasing demand for the higher strength and superior low-temperature toughness in arctic line pipe steels, new processings as well as the new kinds of steels have been developed. Controlled rolling, accelerated cooling after controlled rolling, and heat treatment after pipe forming are included in these processes. The characteristic features of the various microstructures obtained by each processing and their relationships with the mechanical properties are described. The recent development of controlled rolling practice tends to control the wider range of rolling temperature and to utilize the various strengthening mechanisms, accompanied with improvement of toughness. The accelerated cooling after controlled rolling, developed as a new process in plate mill, gives rise to the duplex structure composed of very fine ferrite and bainite. This process enables one to decrease carbon content or alloying elements and to improve weldability of line pipe steels. The microstructural features of heat treatment after piping and welding are described, emphasizing those of weldments.
Structure-Property Relationships for Pearlite-Reduced Mo-Nb Steels Finish-Rolled Moderately Below Ar3
Authors: Coldren AP , Eldis GT , Tither G
Published: March 2009

A study of five laboratory steels was conducted to determine the relative effects of ferrite grain refinement, dislocation substructure, and niobium (carbon, nitrogen) [Nb(C,N)] precipitation strengthening on the as-rolled strength and toughness properties of 19-mm (0.75-in.) plates finish rolled in the two-phase region, moderately below the Ar3 temperature. The steels were molybdenum-niobium (Mo-Nb) pearlite-reduced steels having a nominal composition range of 0.08C, 1.4Mn, 0.1Si, 0.2/0.4Mo and 0/0.6Nb. The amount of ferrite formed prior to the last pass and the percent reduction imparted on the last pass were varied while the finishing temperature was held constant at 745°C (1375°F).

It was found that the introduction of deformed ferrite into the structure brought two strengthening effects: dislocation substructure and, in the niobium-containing steels, strain-enhanced precipitation. The combined effect of these mechanisms reached a maximum in plates containing approximately 30 to 40 percent deformed ferrite that had experienced a 20 percent reduction on the final pass. The impact toughness was not impaired by this method of upgrading strength.

Regarding grain refinement, the 0.2Mo-0.035Nb steel experienced increases in yield strength of up to 85 MPa (12.4 ksi) due to the additional grain refinement produced by rolling below the Ar3 temperature instead of finishing just above the Ar3. This type of strengthening was smaller in the 0.2Mo-0.06Nb steel and absent in the 0.4Mo-0.06Nb steel, because the initial grain sizes of these steels were finer, and lowering the finish-rolling temperature produced little or no further refinement.
Influence of Microstructure on the Temper Embrittlement of Some Low-Alloy Steels
Authors: Viswanathan R
Published: March 2009

The effect of microstructural variations produced by varying the transformation product and the tensile strength level on the temper embrittlement susceptibility of steels has been the subject of some recent studies. A review of the results pertaining to chromium molybdenum (Cr-Mo), chromium-molybdenum-vanadium (Cr-Mo-V), and nickel-chromium-molybdenum-vanadium (Ni-Cr-Mo-V) steels has been completed. Based on the review, it appears that in 2.25Cr-1Mo steels embrittled by step-cooling the transformation product does not appreciably affect the temper embrittlement susceptibility. In Cr-Mo-V and Ni-Cr-Mo steels, susceptibility to embrittlement increases in the order ferrite-pearlite, bainite, and martensite. Results on the effect of strength levels are inconclusive. In general, those structures that cause the steel to have low toughness initially also result in reduced susceptibility for further embrittlement. The limited amount of Auger data available suggest that the effect of microstructure is explainable, at least in part, by differences in grain boundary segregation of impurity elements caused by differences in microstructure.
Structure and Properties of a 19Cr-25Ni-Mo-Ti Steel
Authors: Andersson T , Törnblom H , Samuelsson A
Published: March 2009

SANDVIK 12RN72 is a 19Cr-25Ni austenitic steel with additions of molybdenum, titanium, and boron. In this paper structure, mechanical properties, and high-temperature corrosion properties of 12RN72 are presented.

The structure of 12RN72 in the solution heat treated condition consists of a fully austenitic matrix with some undissolved carbides and nitrides of type TiC and TiN. During creep, M23C6 precipitates in the grain boundaries, and both M23C6 and finely dispersed TiC-particles precipitate in the grains. The small TiC-particles, which precipitate at dislocations, are very stable and their growth rate is low.

The precipitates of TiC and M23C6 greatly contribute to a high creep-rupture strength. For instance, at 700°C the 100 000 h creep-rupture strength of 12RN72 is at least twice that of TP316 and TP347 and about 50 percent higher than that of Alloy 800H. Another prominent feature is the high creep ductility with a transcrystalline rupture behavior.

The high chromium and nickel contents of 12RN72 account for an improved corrosion resistance at elevated temperature in comparison with the standard austenitic steels. Up to about 1000°C, the corrosion properties are similar to those of Alloy 800H that has been verified by tests in air, steam, and impure helium.
Melting of Superalloys
Authors: Lherbier LW
Published: March 2009

Melting of superalloys is the initial, and perhaps most important, step in the production of materials used in critical high-temperature applications. Increasing demand for high-quality superalloys with specific characteristics has resulted in various combinations of primary, melting, refining, and secondary remelting operations. Specific characteristics of each of these process operations are used to produce superalloys that meet customer quality requirements for (1) chemistry, (2) product form, and (3) structural uniformity.

Various combinations of melting processes can be used to obtain a desired primary chemistry not only in terms of the primary elements, but also for residual and tramp elements. Product forms frequently dictate a combination of melting processes that give importance to the shape of ingots, the end product of superalloy melting processes. Additionally, it is frequently important to choose melting combinations that achieve ingot structure control for optimum primary phase distribution, cleanliness or hot workability, or both.
Physical Metallurgy and Effects of Process Variables on the Microstructure of Wrought Superalloys
Authors: Muzyka DR
Published: March 2009

Wrought superalloys that are capable of high strengths at room and elevated temperatures are characterized by complex alloy compositions and phase relationships. Alloy composition establishes which phases will occur, and composition control is critical to assure consistent phase boundary relationships. This presentation discusses the metallurgy of several important superalloys including: A-286, Alloy 901, Alloy 718, Waspaloy and René 95; and two new wrought superalloys, Pyromet CTX-1 and Pyromet 31. The achievement of property goals in these alloys, for various applications, is shown to be related to proper selection of process parameters with respect to phase relationships.
Survey of Mechanical Properties of Steel Cord and Related Test Methods
Authors: Bourgois L
Published: March 2009

This paper gives a survey of the different testing methods for the evaluation of the mechanical properties of steel cord used as tire reinforcement material.

The paper will deal with the latest findings relative to tension tests, compression tests, rotaflex test, dynamic compression tests, fretting simulation tests, and rubber penetration tests.

The steel cord properties measured in those tests will be discussed in relation to tire performance, including steel radial passenger car tires, truck and bus tires, and off-the-road tires. The principal steel cord properties will be illustrated.
Steel Tire Cord—Low Load Elongation
Authors: Lowell AC , Skolnik L
Published: March 2009

A steel cord processing problem, having the potential to affect the achievement of the proper belt geometry, occurred during the early development of steel belted radial tires. Identification of the steel cord property responsible, development of test procedures to screen incoming steel tire cord, and the successful efforts of most steel cord suppliers to correct the problem are detailed in this paper.