bluuebunny/crossref_metadata_2025 huggingface dataset:
Laboratory Methods for Evaluating Bird Repellents Applied to Ripening Fruits
Authors: Tobin ME , DeHaven RW
Published: March 2009

Tests with caged wild birds for evaluating repellents applied to ripening fruits to reduce bird damage should include (1) sufficient time before testing for the birds to become acclimated to captivity, the test surroundings, and the test procedures; (2) environmental control to reduce stress and variation of results; (3) sufficient length of testing time to identify changes in performance which may occur with time; (4) techniques for measuring variation among individual fruits in size, color, and stage of maturity; (5) evaluation techniques which are appropriate for achieving the objectives of the test; (6) repellency criteria, which will permit a valid comparison of test birds; and (7) treatment concentrations that are at levels far enough apart to minimize overlap. Some general guidelines for complying with these recommendations are given. In addition, an actual test design recently used for comparing the repellency of methiocarb-treated grapes among starlings (Sturnus vulgaris), house finches (Carpodacus mexicanus), and American robins (Turdus migratorius) is described and evaluated.
Development of a Preferred Bait for Quelea Control
Authors: Shumake SA , Gaddis SE , Garrison MV
Published: March 2009

Three factors that could influence bait acceptance and palatability (seed size, hardness, and color) were evaluated on small groups of African red-billed quelea (Quelea quelea). The birds were first adapted to feeding on mixed grain from automatic two-choice preference testing devices that alternated positions of the standard and test baits every 5 min. Before testing, the birds were exposed to all levels or formulations of bait for 6 h per day for five days. Preference test data were obtained in four 6-h sessions by using relative consumption (percent preference for test bait) as the dependent measure. Particle sizes tested ranged from 0.3 to 1.8 mg/granule; 6.0 mg hulled proso millet was the standard. All quelea preferred standard whole seed to granules of millet. Ground millet flour, bentonite, and different moisture levels (8, 10, 14, or 16%) were used to achieve different bait pellet textures. This variable had an effect on preference at the lowest (8%) moisture level, indicating that soft, dry pellets are significantly rejected by quelea. Color preference data indicated that red or yellow-green colored millet seed was rejected when compared with the standard yellow millet; however, these effects were not within acceptable levels of statistical significance (P < 0.07). When light levels were reduced and the color-preference test replicated, significant (P < 0.01) preference changes were noted, suggesting that feeding behavior tended to be random with the color stimuli made less visible.
A Simulated Burrow System for Laboratory Evaluation of Vertebrate Control Fumigants
Authors: Elias DJ , Savarie PJ , Hayes DJ , Fall MW
Published: March 2009

A simulated burrow system for laboratory testing of vertebrate pest control fumigants was constructed of readily available plastic pipe and other inexpensive materials. The device is versatile in that it can be easily modified to different configurations. In addition, the device permits controlled comparative evaluation of fumigant agents, test animals can be directly observed during exposure, access to them is immediate, and fumigant dispersal and concentrations can be monitored quickly and accurately.
Criteria for the Development of Coyote Lures
Authors: Fagre DB , Howard WE , Barnum DA , Teranishi R , Schultz TH , Stern DJ
Published: March 2009

The behavioral responses that coyote lures must elicit to attract coyotes to control devices and the chemical characteristics of lures that are required for practical field use are described. These criteria are being applied to the development of a new lure, designated the W-U lure. The first phase involves isolation, identification, and bioassay of key attractants found in coyote urine and anal sacs. Some of these chemicals have been formulated into the W-U lure, which elicits a greater degree of response from captive coyotes than any other synthetic lure and all but one commercial lure tested to date. The second phase of lure development entails standardized evaluations of the W-U lure by comparing it with other attractants in the field using a modified scent station survey. Distributing the W-U lure to field personnel responsible for controlling coyote damage also provides invaluable feedback, but standardized comparisons cannot be made. Preliminary results from both sources of field evaluation indicate that the W-U lure can contribute to improving coyote management.
Oxide Films: Quantitative Sensors of Metal Fatigue
Authors: Baxter WJ
Published: March 2009

An electrochemical technique is described that images and quantitatively measures the distribution and severity of fatigue damage. The technique is based upon (1) the creation of microcracks in a surface anodic oxide film during fatigue of the underlying metal, and (2) the detection of these microcracks by contacting the surface with a gel electrode. When a voltage pulse is applied, current passes through the fatigue-induced microcracks in the oxide film. An image of the sites of current flow is retained in the surface of the gel, while the total charge flow is a measure of the extent of rupture of the oxide film. The capabilities of the technique are illustrated by measurements on aluminum alloys. The distribution of surface fatigue damage may be mapped as early as 1% of the fatigue life, while fatigue cracks ≥ 10 µm long are easily imaged.
Fatigue Crack Initiation and Early Propagation in 3% Silicon Iron
Authors: Tanaka K , Hojo M , Nakai Y
Published: March 2009

The etching susceptibility of dislocations in 3% silicon iron is used to study the initiation and early propagation of small fatigue cracks in smooth specimens subjected to completely reversed cyclic bending. The condition for crack initiation along grain boundaries, which is the dominant mode of crack initiation, is derived from the crystallographic relationship of adjacent grains relative to the stress axis and grain boundary. The propagation behavior of small cracks was compared with that of long through-cracks. Most of the small cracks begin to decelerate, departing from the relation between the rate and the effective stress intensity range for long cracks when the growth path changes from the grain boundary or slip band to the noncrystallographic or transitional path. Some cracks become nonpropagating, while others accelerate again in accordance with the relation between the rate and the stress intensity range for long cracks. Since the crack growth rate is expressed as a unique power function of the size of the highly strained region near the crack, except for slip band cracks, it is concluded that the crack closure is primarily responsible for the anomalous growth behavior of small cracks. Some discussion is given on the influence of the grain size on the fatigue process of the smooth specimen.
Tailoring Ti-6Al-4V Alloy for Energy Applications
Authors: Jaffee RI
Published: March 2009

The process of tailoring an alloy to an optimum composition and microstructure is illustrated by the substitution of Ti-6Al-4V alloy for 13Cr steel in the transition row blading of low-pressure fossil steam turbines. Through control of the processing parameters, the microstructure and texture of Ti-6Al-4V alloy may be controlled to produce fine-grained equiaxed or bimodal microstructures of constant texture.
Research on Sputter-Deposited Selective Absorber Coatings
Authors: Thornton JA
Published: March 2009

The recent development of magnetron sputtering technology has made this coating method applicable to large substrate areas and therefore to selective absorber applications. This paper describes work conducted at our laboratory to investigate the application of magnetron sputtering for depositing selective coatings for both low-temperature and high-temperature collectors. The coatings incorporate metal, oxide, and cermet materials arranged into various combinations of discrete and graded layers. Both d-c reactive sputtering and direct r-f sputtering from oxide and cermet targets have been investigated. The materials have ranged from stainless steel reactively sputtered in carbon monoxide, to cermets formed by cosputtering from alumina (Al2O3) and platinum targets. Coatings on flat plate substrates of glass and stainless steel are described. The coatings typically yield solar absorptance values of greater than 0.90 with room temperature emittances of less than 0.10. Of particular interest are (1) reactive-sputtered multilayer metaloxide coatings, which have thermal stabilities comparable to those of electroplated black chrome (300 to 400 °C in air) and show promise for application in low-cost collectors, and (2) Pt-Al2O3 cermet coatings that are stable at 600 °C in air and applicable to medium and high temperature collectors.
Package Selection, Testing, and Transportation Regulations
Authors: Schaefer RB
Published: March 2009

Agchem package selection, as done by a large company, is reviewed, including methodology, cost study, and specification development. Certain testing methods, standards, and regulatory problems are discussed in detail.
Physical and Biological Responses for Several Suspension Formulations
Authors: Smith DB , Harris FD , Hostetter DL
Published: March 2009

The deposition of suspension particles was studied using scanning electron microscope, neutron activation analysis, and gas chromatograph-fluorometer methods. The quantity of suspension particles deposited was always less than should have been deposited when evaporation did not confound the results. The importance of several materials used as gustatory adjuvants for Heliothis zea larvae is identified. In general, inclusion of a flour in a virus-gustatory adjuvant suspension increased insect mortalities more than other materials evaluated. Mortality increased almost linearly with the flour concentration (up to about 10 percent) for a given virus dosage. The virus half-life was greater for a cottonseed flour adjuvant (Coax) than for a soybean adjuvant, and both adjuvants resulted in longer half-lives than a virus-water suspension.
New Concepts and Discoveries Related to the Strength Characteristics of Plasticized Sulfur
Authors: Gannon CR , Wombles RH , Hettinger WP , Watkins WD
Published: March 2009

The objective of this study was to determine the physical reasons for the high-strength characteristics of plasticized sulfur concrete and to define practical manufacturing techniques.

The results of this study reveal some very interesting phenomena. The Vroom process of sulfur plasticization exhibits a very unusual display of ordered angular crystallization. The Bureau of Mines' plasticized sulfur shows a different crystallization pattern consisting of bonded spherical bodies. These crystallization phenomena indicate a logical physical explanation for the superior strength characteristics inherent in plasticized sulfur concretes manufactured by entirely different processes. These new discoveries are revealed by microscopic examinations utilizing both the stereomicroscope and the scanning electron microscope. These unique microscopic phenomena offer to the scientific community a different explanation as to why unusually higher strengths are obtained in plasticized sulfur concretes. Classical chemical and physical concepts concerning properties of plasticized sulfurs are complemented by factual microscopy. Practical methods of manufacturing sulfur concretes have been defined.
A Numerical Procedure for Predicting Creep and Delayed Failures in Laminated Composites
Authors: Dillard DA , Brinson HF
Published: March 2009

A numerical procedure is described for predicting the viscoelastic response of general laminates. A nonlinear compliance model is used to predict the creep response of the individual laminae. A biaxial delayed failure model predicts ply failure. The numerical procedure, based on lamination theory, increases by increments through time to predict creep compliance and delayed failures in laminates. Numerical stability problems and experimental verification are discussed. Although the program has been quite successful in predicting creep of general laminates, the assumptions associated with lamination theory have resulted in erroneous bounds on the predicted material response. Delayed failure predictions have been conservative. Several improvements are suggested to increase the accuracy of the procedure.
Long-Term Fatigue Behavior of Composite Materials
Authors: Reifsnider KL , Schulte K , Duke JC
Published: March 2009

There is now a significant body of literature that provides a fairly detailed account of the types of damage that commonly develop during the tensile and compressive fatigue loading of high-modulus fibrous composite laminates. Although this body of information is by no means complete, many detailed descriptions of microevents that accompany such loadings are available, and some models have been developed, including successful attempts to represent and predict the stiffness changes which accompany certain types of damage. However, at least two basic and essential questions concerning such fatigue response remain unanswered. First, exactly how does damage reduce laminate strength during long-term fatigue loading? And, second, how does damage (during a long-term fatigue test) combine to cause the fracture event which defines the life of a laminate? The present paper addresses these two questions. Laminates of several types and materials were loaded in cyclic tension or compression at load levels which corresponded to long times to failure. At these “high cycle” levels, the reduction in residual strength was maximized. The corresponding damage states were monitored using an array of nondestructive and destructive techniques. Special attention was given to the damage states that developed just prior to failure. Various concepts and models were applied to the interpretation of the data. Damage development in tension and compression was contrasted.
Modeling Stiffness Loss in Boron/Aluminum Laminates Below the Fatigue Limit
Authors: Johnson WS
Published: March 2009

Previous research has shown that boron/aluminum can develop significant internal matrix cracking when fatigued. These matrix cracks can result in a 40% secant modulus loss in some laminates even when fatigued below the fatigue limit. The present study shows that the same amount of fatigue damage will develop during stress- or strain-controlled tests. Stacking sequence has little influence on secant modulus loss. The secant modulus loss in unidirectional composites is small, whereas the losses are substantial in laminates containing off-axis plies. This paper presents a simple analysis that predicts unnotched laminate secant modulus loss due to fatigue. The analysis is based upon the elastic modulus and Poisson's ratio of the fiber and matrix, fiber volume fraction, fiber orientations, and the cyclic-hardened yield stress of the matrix material. Excellent agreement was achieved between model predictions and experimental results. With this model, designers can project the material stiffness loss for design load or strain levels and assess the feasibility of its use in stiffness critical parts.
Prediction of Long-Term Failure in Kevlar 49 Composites
Authors: Gerstle FP , Kunz SC
Published: March 2009

Creep rupture data in Kevlar 49 epoxy usually exhibit considerable scatter: the coefficient of variation (CV) about the mean failure time at a given stress often exceeds 100%. In this paper, analysis of existing creep rupture data on Kevlar epoxy vessels at four storage pressures has produced an interesting and useful result. It was found that a significant portion of the scatter in failure times for pressure vessels is due to spool-to-spool variation in the eight spools of Kevlar fibers used to wind the vessels. The rank order of mean times to failure was consistent over a pressure range from 23.4 to 29.7 MPa (3.4 to 4.3 ksi), 68 to 86% of short-term burst. Also, the coefficient of variation about the mean failure time for each spool was less than that for the total sample. The statistical inference that the sample is nonhomogeneous was supported by a nonparametric check using the Kruskal-Wallis test and by a parametric analysis of variance. The rank order found in long-term tests did not unequivocally agree with static strength ranks; several spool sets were distinctly high or low. The implication is that, while static strengths are not valid predictors of long-term behavior, short-term creep-rupture tests at high stress definitely are.

The material difference that causes the spool-to-spool variations has not yet been identified for all eight spools. However, it appears that Kevlar behavior at lower pressures may be predicted through the use of curves fitted to the data for each spool. A power law relating failure time to pressure, t = t0(p/p0)m, was found to fit the data reasonably well. From these fits were constructed design-allowable life values with an expected reliability of 0.999999; these predictions are supported by data on vessels at 17.2 MPa (2.5 ksi), where no failures have occurred after 4½ years. The power law fits also demonstrated the extreme sensitivity of failure time to pressure (m ≈ −15 to −25). This implies that, both in composite vessel design and in creep-rupture experiments, the pressure (or stress) level must be carefully controlled.
Status of Knowledge of Radiation Embrittlement in U.S. Reactor Pressure Vessel Steels
Authors: Hawthorne JR
Published: March 2009

Advances in experimental research in the United States toward an improved understanding of property changes in steel by elevated temperature (∼288°C) irradiation are summarized. Four areas of investigation are reviewed, including the confirmation and demonstration of guidelines for radiation-resistant steels, the isolation of metallurgical factors contributing to variable radiation embrittlement sensitivity, the qualification of in situ heat treatments for periodic vessel embrittlement relief, and the correlation of notch ductility and fracture toughness changes with irradiation. Overall, the current state of the art provides both a high capability for tailoring steels for radiation service in new vessel construction and a promising method for controlling radiation embrittlement buildup in existing vessel construction.
Thermal Aging Capsule Results from Oconee Nuclear Station—Unit 1
Authors: Lowe AL
Published: March 2009

At the Oconee Nuclear Station—Unit 1 a thermal aging capsule was removed and tested at the same time a second reactor vessel surveillance capsule was removed for testing. The thermal aging capsule had received a thermal exposure of 15000 at 580°F (305°C) and the irradiated capsule had received an exposure of 1.5 × 1018 n/cm2. The capsule contained Charpy V-notch and tension specimens of SA-302 B modified base and weld metal and SA-533 B1 correlation monitor material.

The SA-302 B base metal exhibited no significant changes in Charpy V-notch impact properties as a result of thermal aging. The heat-affected-zone data indicated a drop in upper shelf properties. This drop was attributed to limited thermal aged data points and large scatter in the base data, since the notch lateral expansion and shear fracture data did not indicate the same trend. The SA-302 B weld metal exhibited a slight increase in upper shelf energy, and the SA-533 B1 correlation material exhibited a slight decrease in upper shelf energy. No tension data are reported. The conclusions of this study agree with the results reported from the Big Rock Point reactor.
Rapid Screening Luminescence Techniques for Trace Organic Analysis
Authors: Vo-Dinh T
Published: March 2009

This paper provides an overview of the principles and applications of two spectroscopic methods, synchronous luminescence (SL) and room temperature phosphorescence (RTP), used as rapid screening tools for monitoring polynuclear aromatic compounds in real-life samples. Two practical examples, a screening procedure of various coal products and a characterization procedure of the total particulate matter from cigarette smoke condensates, will illustrate the efficacy of the SL and RTP techniques. The paper will also briefly review other applications of the SL and RTP techniques in the areas of environmental and industrial process control.
Investigations on the Use of Laser Dyes as Quantum Counters for Obtaining Corrected Fluorescence Spectra in the Near Infrared
Authors: Duggan JX , DiCesare J , Williams JF
Published: March 2009

Several laser dyes were evaluated as quantum counters for obtaining corrected fluorescence spectra in the near infrared regions. Preliminary results indicate that hexamethylindotricarbocyanine (HITC) and LDS-798 (Exciton Chemical Co., Overlook, OH) both have quantum yields that are independent of wavelength and can extend the limits of spectral correction to 800 and 700 nm, respectively. A binary quantum counter containing a mixture of Rhodamine B (RhB) and HITC was also evaluated. The quantum yields of HITC and LDS-798 were estimated to be 0.28 and 0.14, respectively, compared to a value of 0.95 attributed to RhB. Examples of corrected spectra obtained using LDS-798 and HITC are compared with absorbance spectra and other accepted standards. Preliminary stability tests are discussed and further studies suggested.
A Comparison of Fire Resistive Coatings in ASTM E 119 and Proposed ASTM E 5 Hydrocarbon Pool-Fire Test Environments
Authors: Gratzol OK , Diliberto MC
Published: March 2009

The exposure of proprietary fireproofing materials and concrete to the proposed ASTM Standard Hydrocarbon Pool-Fire Test Environments (E 5) does not exhibit any significant difference for thermal shock from ASTM Fire Tests of Building Construction and Materials (E 119-76).

The duration of protection is reduced in the hydrocarbon pool-fire environment, but the areas under the furnace time/temperature curves are essentially unchanged. The shorter duration is offset by the area under the curve attributed to the more rapid heat rise for specimens compared with those tested using ASTM E 119. There appears to be a measurable relationship between the proposed ASTM E 5 hydrocarbon pool-fire and ASTM E 119 tests, which provides data to forecast the result of one to the other for a given furnace and set of circumstances.

This work was undertaken to compare the effects of the proposed ASTM E 5 simulated hydrocarbon pool-fire on fire resistive coatings and poured-in-place concrete versus the standard ASTM E 119-76 time/temperature criteria. Specimens of similar construction were tested in both environments. A hose stream, similar to that used in petrochemical industry fire-fighting practices, was used on the specimens tested in the hydrocarbon type fire to evaluate the erosive effect and thermal shock characteristics of the generic proprietary products in the marketplace. All specimens showed some erosion.

The test program showed no reason to incur the cost of testing to the proposed ASTM E 5 Hydrocarbon Pool-Fire Test Standard, as 3-h ASTM E 119 rated fireproofing, and 50-mm (2-in.) poured-in-place concrete provided similar correlations between both tests.
A Comparison of Critical Properties of Magnesium Oxysulfate and Magnesium Oxychloride Cements as Used in Sprayed Fire Resistive Coatings
Authors: Herrera ME
Published: March 2009

Magnesium oxysulfate cements although not as strong as magnesium oxychloride cements are better suited for fire resistive uses. Magnesium oxysulfate cements start to decompose at temperatures more than two times higher than magnesium oxychloride cements decompose giving longer fire protection. Their products of decomposition at elevated temperatures are less noxious (sulfur dioxide) than those of oxychloride (hydrochloric acid) and less corrosive.

Weather conditions (humidity, temperature, and wind) during application are not as critical with oxysulfates as with oxychloride, which may partially form unstable magnesium hydroxide instead of magnesium oxychloride. Commonly known as “burnout” or “dry set,” this unwanted reaction can be the cause of loss of bond, cracking, loss of volumetric stability, poor physical properties, and corrosion. Since fire resistive coatings are generally light in density, they are not expected to be as strong as flooring products where the oxychlorides are normally used and are superior. For the intended use as fire resistive and insulative coatings, when those properties are compared, magnesium oxysulfate cements are preferred.
Fire Resistive Coatings in the USSR: An Overview
Authors: Lieff M
Published: March 2009

The use of fire resistive coatings in wood and steel construction is reviewed by the author, who visited the Union of Soviet Socialist Republics (USSR) in July 1981, as a member of the US-USSR Panel on Fire Protection. Included are English translations of two Soviet standards (GOST) for Fire Protective Phosphate Coatings for Wood and for Steel.
Automatic Sprinklers Versus Direct Applied Fire Protection: Can There Be Trade-offs?
Authors: Anderson GT
Published: March 2009

Trading off one form of fire protection for another is becoming a common place occurrence in construction today. On both a national and local level, building codes are allowing direct substitution of one form of fire protection for another. The objective of this paper is to question the justification of this concept as it applies to automatic sprinklers versus direct applied structural steel fire protection. It is important to keep in mind that structural steel fire protection is intended to maintain structural integrity in a fire while automatic sprinklers are a mechanical extinguishing system. The end result is that both systems complement each other and were never intended to replace one another.
Formulations of Entomopathogens
Authors: Sawicka EM , Couch TL
Published: March 2009

A brief history of the development of entomopathogens will be presented. Descriptions of unusual problems faced by researchers when formulating, stabilizing, and testing biological materials, specifically Bacillus thuringiensis formulations, will be presented. The importance of adjusting the physical and biological properties of a formulation for delivery to the target species will be discussed. Environmental aspects of the use of biological pesticides will be presented.
A Quality Control Program Used for Agricultural Formula A Production
Authors: Keim WA
Published: March 2009

The goal of a quality control program is to obtain data on each production lot efficiently to provide assurance that it meets the product specification. A program is reported that uses a minimum number of control sample analyses to generate the data required for application of statistical methods. The proper combination of the assay product specification, analytical methods, and statistical methods is illustrated through use of the cumulative-average chart in the production of Formula A. The procedures for product approval, starting the quality control program, the number and evaluation of control sample analyses, rejection of analytical results and blunders, and preparing the laboratory report are defined. This quality control program provides cost-effective quantification of data from costly and complex analytical methods.
Evaluation of Tank Mix Compatibility Using the Laboratory Sprayer
Authors: Smith NR
Published: March 2009

This paper describes an instrument, the Laboratory Sprayer, which has been designed to evaluate the compatibility of pesticide tank mixes by a method significantly more representative of field application than the commonly used ball jar test. The Laboratory Sprayer has been designed to incorporate as many features of the full-scale equipment as possible, including constant agitation, circulation through a filter, and spraying through a nozzle to simulate the dynamics of a field application. In contrast to the static ball jar test, this sprayer has been found to show excellent correlation with field conditions.
Spray Drift Exposure Assessment
Authors: Holst RW
Published: March 2009

The Pesticide Registration Guidelines and certain regulations governing the application of pesticides under the Federal Insecticide, Fungicide, and Rodenticide Act (FIFRA) have undergone changes in recent years. In the area of spray drift evaluation, the U.S. Environmental Protection Agency (EPA) is still actively pursuing technical and scientific questions associated with pesticide drift and the possible exposure of humans, animals, and plants to spray drift. A problem still to be addressed is that of building a comprehensive data base of downwind quantification and droplet distribution data through the use of wind tunnel studies or direct in-flight assessments. The specific data requirements for these studies have not as yet been completed. In the areas of application safety and precautionary statements, the EPA has increasingly worked with the individual states and through the State-Federal Issues Research and Evaluation Group (SFIREG). Coordinated work is continuing with other federal agencies and interested groups in the areas of spray drift research and pesticide application methodology through such programs as Self-Regulating Application and Flight Efficiency (SAFE) and Pesticide Applicator Training (PAT). Also within this effort is the application of numerous exposure models in a broad spectrum of environmental fate determinations. These models are based on an ever-increasing amount of data with corroboration by monitoring studies. The spray drift models will be used for exposure analysis by registrants and EPA personnel and by pesticide applicators for application safety and efficiency. These various aspects of pesticide data generation, modeling, and group interaction comprise part of the EPA's continuing effort to provide sensible and current regulation of pesticide application and use in order to ensure the availability of necessary pesticides and still protect the environment.
Statistical Scatter in Fracture Toughness and Fatigue Crack Growth Rate Data
Authors: Johnston GO
Published: March 2009

The use of probabilistic fracture mechanics to assess the reliability of engineering structures requires knowledge about the statistical scatter of the parameters used in the models.

A review is given of the statistically defined tanh reference toughness curves. This method is then used to aid an investigation into the effect of tighter chemical specifications. The predicted curves and small quantity of available published data do support the hypothesis of improved brittle/ductile transition temperatures with controlled chemistry. An experimental program has been undertaken to obtain plain plate data that are then used to derive an empirical correlation between KIc and Charpy energy, assuming the distributions of crack tip opening displacement and Cv can be related for lower shelf temperatures. Tolerance limits and sample size estimates are also obtained for specified confidence levels.

Data on fatigue crack growth rates have been reviewed and the effects of parameters, such as stress ratio, temperature, and irradiation, studied qualitatively. A statistical analysis of published data has enabled a distribution for C in the Paris law to be derived assuming a linear ℓn C versus m relationship.

Finally, an illustrative example calculates the change in failure probability with the number of accumulated cycles.
Statistical Methods for Estimating Crack Detection Probabilities
Authors: Berens AP , Hovey PW
Published: March 2009

To characterize the uncertainty in nondestructive evaluation (NDE), a probability of crack detection (POD) as a function of crack length is postulated where POD is defined as the proportion of cracks of a given length that would be detected by the NDE technique when applied by inspectors to structural elements in a defined environment. This paper presents a statistical framework for describing the uncertainty in the NDE determinations, and evaluates various characterizations of NDE reliability. The data from a recent Air Force study on NDE reliability are used to estimate the parameters of the NDE model. For these representative capabilities, NDE reliability experiments are simulated. Different NDE capability characterizations are computed for each simulated experiment and are statistically compared.
Method for Determining Probability of Structural Failure from Aircraft Counting Accelerometer Tracking Data
Authors: Larson CE , Shawver WR
Published: March 2009

This study develops a methodology that puts the aircraft's stress at critical or reference locations on a probability basis that includes the variability effects of Mach number, altitude, and gross weight. The stress variation due to these variables is then handled probabilistically and applied to the material's cycles to failure (S-N curve) variation to obtain a fatigue life expended (FLE) probability distribution. This FLE probability distribution may be used to derive FLE values that can be expected for the aircraft instead of the single high conservative value that is now being calculated.
Development of a Proposed ASTM Standard Test Method for Near-Threshold Fatigue Crack Growth Rate Measurement
Authors: Bucci RJ
Published: March 2009

Results are summarized which provide the basis for development of the proposed ASTM standard test method for measuring and presenting very slow cyclic rates of fatigue crack propagation. The technique for obtaining very slow rate data as K decreases with crack extension is described. Data are reviewed that show the individual and combined effects of various precracking and testing procedures, loading rates, and other testing parameters. The data are used to demonstrate the utility of the method and its limitations. Guidelines are given for the minimization of transient growth rate processes which can confound interpretation of the data. Analytical procedures for fitting near-threshold data are also discussed.
Specimen Size Considerations in Fatigue Crack Growth Rate Testing
Authors: James LA
Published: March 2009

The effect of specimen size upon the fatigue crack growth rate behavior of annealed AISI Type 304 stainless steel was studied at two stress ratios at an elevated temperature. The resulting data were examined in the light of the present ASTM size criterion (based upon monotonic yield strength) and a proposed criterion based upon the material flow strength. The flow stress criterion is considerably less restrictive than the present ASTM criterion. The results of this study indicate that the flow stress criterion is entirely appropriate for strain-hardening materials such as austenitic stainless steels.
Procedures for Precision Measurement of Fatigue Crack Growth Rate Using Crack-Opening Displacement Techniques
Authors: Yoder GR , Cooley LA , Crooker TW
Published: March 2009

This paper describes experimental and analytical procedures whereby the conventional commercial fracture mechanics clip-gage can be used for precision measurement of fatigue crack growth rate in compact-type specimens. Potential sources of error in measuring crack length via crack-opening displacement (COD) techniques are delineated. Comparisons are made between crack-length data obtained via specimen surface observations and COD techniques. Comparisons are also made between data analyzed by the secant and 7-point incremental polynomial methods. It is emphasized that COD techniques can enhance the accuracy of the secant method of data reduction. Steploading procedures using COD techniques are described. Proposed amendments to ASTM Tentative Test Method for Constant-Load-Amplitude Fatigue Crack Growth Rates Above 10−8 m/Cycle (E 647-78 T) regarding incrementing of crack-length measurements via COD techniques are discussed.
Prediction of Structural Crack Growth Behavior under Fatigue Loading
Authors: Hopkins SW , Rau CA
Published: March 2009

Structural components which undergo operational fatigue cycles have historically been designed for fatigue resistance based upon crack initiation data generated on smooth and notched laboratory speimens. More recently, reliability has been improved by using linear elastic fracture mechanics (LEFM) to assure that flaws, even if present, cannot grow to a dangerous size during service. The methodology and input data utilized for LEFM evaluation are described, and the impact of variations in key input parameters are discussed in detail. Specifically, the paper describes the sensitivity to (1) loading parameters: applied cyclic stresses, mean stresses, residual stresses, load spectrum, and stress distributions, (2) local crack driving force: crack size, shape, orientation, growth, and growth mode, (3) materials properties: crack growth rate constants, crack growth threshold, and response to spectrum overloads, and (4) initial flaw size, with and without nondestructive inspection.

Presently, LEFM analyses are often deterministic and utilize conservative (worst-case) assumptions for all input parameters which are not known. The assumptions that all worst-case conditions occur simultaneously lead to extremely conservative designs which may be economically unacceptable. Probabilistic fracture mechanics methods have been developed which incorporate the statistical variations or uncertainties that actually exist and establish a more realistic quantitative basis for design allowables and accept/reject criteria, which optimize the cost/risk trade-offs that must be made.
Fatigue Considerations for Steel Bridges
Authors: Barsom JM
Published: March 2009

This paper discusses the characteristics of the discontinuities that are the origins of fatigue cracks in various welded details, and presents the American Association of State Highway and Transportation Officials (AASHTO) fatigue-design curves for those details. The paper also presents a summary of the fatigue-crack-propagation data that have been obtained for bridge steels and weldments, and discusses some of the problems that need to be resolved to better predict the fatigue life of welded bridge details by using fracture-mechanics technology. It is suggested that until these problems are rectified the AASHTO fatigue-design curves present an excellent alternative to fracture-mechanics technology to ensure the structural integrity of welded details subjected to cyclic loadings.
Further Developments in the Design and Analysis of Adhesive-Bonded Structural Joints
Authors: Hart-Smith LJ
Published: March 2009

Previous elastic-plastic analysis of adhesive-bonded joints has covered double-lap, single-lap, scarf, and stepped-lap joint configurations in which the adhesive was considered to be uniform throughout. As part of the Primary Adhesively Bonded Structure Technology (PABST) program, the earlier computer programs for analyzing stepped-lap adhesive-bonded joints and doublers, A4EG and A4EH, were modified to permit the inclusion of variable adhesives as well as nonuniform adherends. This paper presents the results of the modifications. The features of the latest version of the analysis program, A4EI, are described, and examples show the effects of load redistribution around flaws and porosity. These examples are significant in establishing realistic inspection and acceptance criteria for bonded structures. The loss of strength associated with pinched-off edges is illustrated, and the benefits of deliberately thickening the adhesive layer in the immediate vicinity of the ends of the overlap are documented. The changes in shear load transfer due to softening of some of the adhesive by moisture absorption while the remainder either has never been soaked or has dried out locally are discussed. PABST experience and the analyses indicate that bonded structure is more tolerant of bond flaws than was once believed. Other new features of the A4EI program include the provision for applying a running shear load along the length of the joint, as for a wing spar, and a separate calculation for the residual thermal stresses in the absence of external load, when bonding fibrous composites to metal fittings. A modification of the coding logic has shortened run times for the various cases, which now include analysis of internal stresses associated with specified load levels in addition to the elastic and elastic-plastic strengths which could be computed by the earlier programs. Both single and double-bond surfaces can be specified.
Development of a Mechanistic Model of Acute Heavy Metal Toxicity
Authors: Szumski DS , Barton DA
Published: March 2009

A theoretical model of heavy metal toxicity based on inhibition of respiratory functions is proposed. The model is based on the concept that heavy metals competitively interfere with respiratory carbon dioxide (CO2) excretion at carbonic anhydrase enzyme sites in the gill membranes of fish. In this regard, the model presents equations which are descriptive of toxification and detoxification processes within the organism. It is proposed that the death of the organism is caused by buildup of CO2 in the blood, reduced oxygen-carrying capacity within the blood, and, ultimately, acute hypoxic stress. The implications of this work in developing water quality criteria for heavy metals are also discussed.
Validation of Exposure Models: The Role of Conceptual Verification, Sensitivity Analysis, and Alternative Hypotheses
Authors: Burns LA
Published: March 2009

Available methods for evaluating the veracity and reliability of exposure models extend far beyond simple comparisons of observed and predicted values. To be valid, model tests must, first, be tailored to evaluate a model within its intended range of operation. Appropriate tests must then be developed to ensure that the model performs in accord with its designers'; intentions and that significant phenomena have not been neglected or oversimplified. Finally, comparisons between model predictions and realworld data sets can be used to compare the performance of competing models, but such studies usually cannot serve as general proofs of the reliability or validity of an individual model. These points can be elucidated by means of a discussion of some of the “validation” studies executed during the development of the exposure analysis modeling system (EXAMS). The EXAMS was designed to evaluate the probable long-term behavior of newly synthesized organic chemicals in aquatic systems. This design constraint strongly influenced the structure of the computer program and constrained the choice of appropriate tests of the program's capabilities. Conceptual verification, that is, comparison of program outputs with defined special cases, was used to evaluate and modify the program's description of chemical exchanges across the benthic boundary layer. Sensitivity analysis was used to assess the potential error induced by using reaction quantum yields as summary descriptors of the effects on photochemical reactivity of sorption to suspended sediments. “Validation,” in the sense of direct comparisons with observational data, was used to test the relative success of several versions of a two-resistance volatilization model. Complex exposure models can never be fully validated in the dictionary sense of establishing the conclusive truth. Instead, we must rely upon a history of successful applications to impart increasing confidence in the reliability and applicability of the tools of environmental chemistry and computer modeling to environmental problems.
Do Organisms in Laboratory Toxicity Tests Respond Like Organisms in Nature?
Authors: Chapman GA
Published: March 2009

Laboratory toxicity test results predict the responses of natural organisms with varying degrees of accuracy. The selection of test species and dilution water can greatly influence the applicability of the data in different situations. Other factors, such as nutrition, acclimation, and genetic selection, may influence the accuracy of predictions based on laboratory data. The relative importance of factors influencing the responses of organisms in the laboratory and in the field depends on whether the goal of the laboratory tests is to determine relative toxicity, to estimate safe levels, or to predict actual effects. When appropriate test parameters are chosen, the response of laboratory organisms is a reasonable index of the response of naturally occurring organisms.
Translation of Laboratory Results to Field Conditions: The Role of Aquatic Chemistry in Assessing Toxicity
Authors: Lee GF , Jones RA
Published: March 2009

One of the most significant problems facing the water quality management field today is the translation of laboratory-derived aquatic toxicology criteria and standards to natural water field conditions. This problem is caused, in part, by the markedly different chemical environments that frequently exist in laboratory toxicity tests and the field. Normally, laboratory-developed water quality criteria are derived from bioassays in which the contaminant is presented to the organism in a completely or nearly completely available form or forms; however, under field conditions, many contaminants exist in a variety of forms only some of which are available to aquatic organisms.

Guidance is provided on how to use knowledge of the aqueous environmental chemistry of the contaminant or contaminants of concern to detect situations in which there may be markedly different toxicity levels under field and laboratory conditions. A hazard-assessment approach is outlined by which maximum use can be made of existing laboratory bioassay data and environmental chemistry in site-specific water quality evaluation.
Evaluation of Technical Limitations to Determining Organic Contamination in Subsurface Soils
Authors: Baty CJ , Perket CL
Published: March 2009

The major technical impediments to quantitative determination of organic contamination in subsurface soils are the following: lack of an established procedure, heterogeneous specimens with unconfirmed representativeness, and difficulty in assessing method accuracy. These technical limitations have been discussed with respect to a specific case study at the site of a former wood-preserving plant.

Subsurface soil specimens were obtained from the former wastewater drainage trench and lagoons, Soxhlet extracted with methylene chloride, and analyzed by gas chromatography (GC) and high-pressure liquid chromatography (HPLC) for phenolic compounds and polynuclear aromatic hydrocarbons (PNAs), respectively. Interlaboratory and intralaboratory precision was evaluated and was shown to be poor. Accuracy was not determined.

Excavation and soil test borings were compared for utility and sensitivity in subsurface sampling. Data obtained from soil test borings alone did not adequately depict the subsurface patterns of contamination evidenced by the excavation.
Rapid GC/MS Identification of Hazardous Organic Compounds in Complex Extracts
Authors: Dymerski PP
Published: March 2009

An analytical laboratory scheme has been designed specifically to support the rapid and cost effective characterization of complex hazardous waste materials. Rapid analysis includes “compatibility” testing of the gross characteristics of the material, identification and quantitation of metals, and the identification and semi-quantitation of organic compounds in water, soil, sludge, and organic matrixes. Organic compounds can be screened by gas chromatography and characterized by halogen or nonhalogen content. The former includes poly(chlorinated biphenyls) (PCBs), which are quantitated using a novel basic computer program. Other halogenated compounds are identified using gas chromatography/mass spectrometry (GC/MS) with the aid of a halogen isotope cluster survey program. Nonhalogenated compounds are identified by fingerprint chromatograms or searching the GC/MS spectral library.