bluuebunny/crossref_metadata_2025_split huggingface dataset:
A Comparison of Pure Mode I and Mixed Mode I–III Cracking of an Adhesive Containing an Open Knit Cloth Carrier
Authors: Ripling EJ , Crosley PB , Johnson WS 
Published: February 2009

A modified TDCB specimen was used to compare crack resistance in pure mode I and mixed mode I–III loading. Static and fatigue tests were conducted on two commercial, modified epoxy film adhesives (FM 73 and FM 300K) having a wide open knit polyester carrier. The fatigue tests were conducted at 10 Hz in a low humidity and at 3 Hz in a high humidity.
The fracture toughness of both adhesive systems, in terms of Gtotal, was 1 ⅔ to 2 times higher for the mixed-mode specimens than for the pure mode I specimens. For the dry fatigue tests, ΔGT for a fixed crack growth rate was also much higher for mixed mode than for Mode I cracking. A fracture law based on these data would be quite different from one based on the large amount of mixed mode I–II data now available. These differences appear to be the result of differences in fracture behavior produced by different types of carrier cloths. For Mode I cracking in the present study, separation occurred between the adhesive and the carrier cloth, which lowered both the cyclic and static debond resistance to values less than those reported earlier for FM 300 with a tricot knit carrier. For the mixed-mode specimens, on the other hand, the carrier cloth, rather than separating from the adhesive, shredded, which increased the crack resistance above the mixed-mode values reported previously for FM 300. This behavior suggests that the carrier cloth in film adhesives has a greater influence on crack resistance than generally thought. Thus fracture laws for adhesive joints may also be more complex than previously thought.
Understanding Effects of Adhesive Ductility and Bondline Geometry on Tube-and-Socket Joint Performance
Authors: Miller JM , Hammill JL , Luyk KE 
Published: February 2009

Tube-and-socket joints are commonly used in adhesively bonded structural assemblies. Three parameters which can affect the structural performance of bonded tube-and-socket joints are overlap length, bondline thickness, and adhesive properties. Adhesive shear behavior and the effects of overlap length and bondline thickness on tensile failures and stress distributions in a round tube-and-socket joint are evaluated. Bondline thickness is varied using finite element models to determine its effect on maximum radial and shear stresses and stress variations through the adhesive thickness. Measured tensile failure loads are compared with predictions from a fully plastic closed-form analytical model.
Results show the measured tensile failure loads of tube-and-socket joints to be dependent on bondline thickness and adhesive ductility. Joints with thin bondlines develop higher tensile failure loads than joints with thick bondlines. The combination of thick bondlines and the brittle adhesive resulted in the lowest tensile failure loads. Predicted stress distributions from finite element analyses show the magnitude of the maximum radial stresses in tube-and-socket joints to be strongly dependent on bondline thickness. Maximum radial stresses are higher in thick bondlines than in thin bondlines. The brittle adhesive is sensitive to the high radial stresses occurring in thick bondlines, as evidenced by tensile failure loads and predicted stress distributions. The ductile adhesive is not as sensitive to the magnitude of the radial stresses.
Computation of the Amplitude of Stress Singular Terms for Cracks and Reentrant Corners
Authors: Szabó BA , Babuška I 
Published: February 2009

The theoretical basis and performance characteristics of two new methods for the computation of the coefficients of the terms of asymptotic expansions at reentrant corners from finite-element solutions are presented. The methods, called the contour integral method (CIM) and the cutoff function method (CFM), are very efficient: the coefficients converge to their true values as fast as the strain energy, or faster.
In order to make the presentation as simple as possible, we assume that the elastic body is homogeneous and isotropic, is loaded by boundary tractions only, and, in the neighborhood of the reentrant corner, has stress-free boundaries. The methods described herein can be adapted to cases without such restrictions.
Role of Damage Tolerance and Fatigue Crack Growth in the Power Generation Industry
Authors: Coffin LF 
Published: February 2009

The problem of intergranular stress-corrosion cracking (IGSCC) in boiling water reactor (BWR) piping is discussed and the body of work undertaken in the author's laboratory to solve that problem is described. Particular attention is given to the development of electrical potential crack monitoring techniques and their application to surface crack growth, particularly under conditions approaching those found in service. The important role of water chemistry and its control is described in this context.
The concept and description of sensors to monitor in situ the degree of damage containment from intergranular stress-corrosion cracking is then described, with reference to use in piping components and other types of monitoring.
Finally, a concept for the life management of structures is described where damage processes are identified and monitored in situ using appropriate sensors to measure the damage rate continuously. In conjunction with damage monitoring, an applicable life prediction model is used to forecast the future damage state and to assist in the decision process for appropriate required actions to optimize plant operation.
Application of the J Concept to Fatigue Crack Growth in Large-Scale Yielding
Authors: Lambert Y , Saillard P , Bathias C 
Published: February 2009

Fatigue crack propagation tests were performed on compact tension specimens of AISI 316 steel, in the elastic-plastic and plastic regions. The parameter ΔJ was chosen to characterize propagation. Results show that there is a Paris law type correlation between propagation rate and ΔJ. An effect on propagation rate, which is attributed to the R = Pmin/Pmax ratio, has been noted.
A numerical verification of the applicability of the ΔJ concept was determined by use of a theoretical equation. These results were compared with experimental results.
Fracture Toughness of Stainless Steel Welds
Authors: Mills WJ 
Published: February 2009

The effects of temperature, composition, and weld-process variations on the fracture toughness behavior for Types 308 and 16-8-2 stainless steel (SS) welds were examined using the multiple-specimen J-resistance-curve procedure. Fracture characteristics were found to be dependent on temperature and weld process, but not on filler material. Gas-tungstenarc (GTA) welds exhibited the highest fracture toughness, a shielded-metal-arc (SMA) weld exhibited an intermediate toughness, and submerged-arc (SA) welds yielded the lowest toughness. Minimum expected fracture properties were defined from lower bound fracture toughness and tearing modulus values generated here and in previous studies.
Fractographic examination revealed that microvoid coalescence was the operative fracture mechanism for all welds. Second-phase particles of manganese silicide were found to be detrimental to ductile fracture behavior because they separated from the matrix during the initial stages of plastic straining. In SA welds, the high density of inclusions resulting from silicon pickup from the flux promoted premature dimple rupture. The weld produced by the SMA process contained substantially less manganese silicide, while GTA welds contained no silicide inclusions. Delta ferrite particles, present in all welds, were substantially more resistant to local failure than the silicide phase. In welds containing little or no manganese silicide, delta ferrite particles initiated microvoid coalescence, but only after extensive plastic straining.
Genetically Engineered Microorganisms in the Aquatic Environment: Environmental Safety Assessment
Authors: Molak V , Stara JF 
Published: February 2009

The deliberate release of genetically engineered microorganisms (GEMs) into the environment is a promising approach to the amelioration of environmental problems such as pollution and pest control.
GEMs may find their way into the aquatic environment, (oceans, streams, groundwaters, lakes, wastewaters, and sludges) either by direct release into that environment or, after uses on land, via surface runoff and soil seepage into groundwaters, streams, lakes, and estuaries. Since experience with the deliberate release of GEMs is very limited, it is necessary to develop approaches for risk assessment of the potential adverse effects that could be caused by the introduction of a large number of novel microorganisms into the aquatic environment. The accepted approach to risk assessment (hazard identification, exposure, and dose-response assessment, leading to risk characterization) has been used to develop models for risk assessment of the deliberate release of GEMs into the aquatic environment. The new concept introduced in this risk assessment is that of “critical mass,” defined as the number of GEMs applied at a specific site that would result in replacement of endogenous microorganisms. This “critical mass” would depend both on the properties of GEMs and on the number and properties of endogenous microorganisms at the site of GEMs application. An experimental assessment of critical mass may be possible by using aquatic microcosms corresponding to the aquatic environment into which GEMs would be released.
Paleoecology and Environmental Analysis
Authors: Cowgill UM 
Published: February 2009

A discussion is presented which shows the types of information that may be gleaned from the chemical, mineralogical, and biological analyses of lake muds. Illustrations are taken from a variety of studies carried out in various countries.
Substantial rises in the concentration of sulfur in the recently deposited mud as well as in the surface water of Linsley Pond (North Branford, Connecticut) are indicative of industrial expansion in the region over the past five decades. Similarly, stack emissions produced by the combustion of fossil fuels have caused rises in sulfur concentrations and subsequent changes in pH in unbuffered waters of Southern and Southwestern Scandinavia. These phenonmena have brought about shifts in population size and distribution among the lake plankton.
Recent technological growth has resulted in a progressive increase in mercury in the sediments of Lake Windermere, United Kingdom, Lake Huleh, Israel, and Lake Biwa, Japan. No doubt reflecting man's global activities, similar rises in concentrations of lead, cadmium, and silver have been noted in recently deposited muds in various sections of the world. The steady rise of phthalates noted in recently deposited sediments is indicative of the advent of the use of plastics in the many areas of human endeavor.
To ascertain which of the various hypotheses advanced to explain the sudden collapse of the ancient Mayan culture in Central America were valid, a series of lake cores were taken in Guatemala and subjected to chemical and biological analyses. The ecologically oriented hypothesis appears to be invalid. Furthermore, these studies showed that a high agricultural civilization developed and that under modern conditions a larger agricultural population employing indigenous methods can be supported. In addition, these investigations showed that early man changed a savanna to a tropical forest and that his activities brought about only a small increase in the erosion rate.
Additionally, paleoecological methods may be used to elucidate past climates, the advent of agriculture in a region, processes of plant selection and domestication, effects of slash and burn agriculture, the size of one time plankton populations, the chemical concentration of the atmosphere in ancient times, the history of a landscape, and the effect of road building on nearby lakes.
Environmental Persistence/Degradation of Toxicity in Complex Effluents: Laboratory Simulations of Field Conditions
Authors: Degraeve GM , Clement WH , Arthur MF , Gillespie RB , O'Brien GK 
Published: February 2009

A laboratory method to monitor the persistence or degradation of toxicity in complex effluent/receiving water mixtures was developed and preliminarily field-validated. The objective of this research was to develop a method for possible future use in the National Pollutant Discharge Elimination System (NPDES) effluent permitting process that recognizes differential rates of toxicity degradation in effluent/receiving water mixtures.
Initial studies were made with the toxicant 2,4-dichlorophenol (DCP) added to a natural receiving water in the laboratory. After incubation under conditions similar to the field, toxicity (as measured periodically by Microtox®) paralleled the degradation (or persistence) of the toxicant as measured chemically. Loss of DCP in the laboratory was similar to predicted field-loss rate. Receiving waters and industrial and municipal effluents were then incubated in the laboratory in proportions similar to those observed in the field. Environmentally relevant conditions of temperature, photoperiod, light intensity, humidity, and aeration were maintained. Periodically, samples were analyzed for toxicity using the Microtox® system to monitor persistence (or degradation). Following development of test protocol with the DCP and effluents, the laboratory unit was field-validated using chlorine in Mississippi River water in the field and in the laboratory. Other field validations using complex effluents are underway.
This simple laboratory method can be used to predict the persistence (degradation) of effluent toxicity in natural receiving waters. Ultimately, one may be able to model effluent toxicity behavior in natural systems by tracking toxicity degradation in the laboratory, which could result in a cost-effective, toxicity-based method for use in the NPDES permitting process.
Evaluating Ecosystem Response to Toxicant Stress: A State Space Approach
Authors: Johnson AR 
Published: February 2009

Ecosystems can be regarded as complex biogeochemical systems maintained in a state of thermodynamic nonequilibrium by the flow of materials and energy. The state of such a system at any given time is generally assumed to be characterized by a finite set of measurable quantities. If these variables are taken to be the components of a vector, the instantaneous state of an ecosystem can be represented by a single point in an abstract multidimensional space. As an ecosystem undergoes changes in state, changes in the position of the corresponding vector will result, tracing out a state trajectory over time.
Within a state space representation, the response of an ecosystem to a perturbing influence, such as a toxicant, can be viewed as a displacement of the state vector away from its unperturbed trajectory. Such an approach was used to analyze data from a study of the response of experimental ponds and microcosms to chronic additions of a coal-derived synthetic oil. Ecosystem-level response surfaces and dose-response curves were derived based upon the average separation (distance of displacement) of exposed ecosystems relative to controls. The results exhibited patterns analogous to those observed in classical toxicology based on organismal response and could be used to define acceptable exposure conditions. The state space approach described here provides a coherent and objective framework for summarizing a large multivariate data set, and it should be of general use in providing both qualitative and quantitative descriptions of the behavior of perturbed ecosystems.
What Constitutes Field Validation of Predictions Based on Laboratory Evidence?
Authors: Cairns J 
Published: February 2009

The term validation has appeared in the literature with great regularity in the last few years, but the process has yet to be explicitly stated. Most of the predictions of environmental hazard are based primarily, and sometimes entirely, on laboratory toxicity tests involving single species. While this may change over the years, it will remain true for the immediate future. Therefore, the validation process must start with an explicit statement of the types of predictions being made on the basis of single species laboratory toxicity tests. Unfortunately, the terms no-adverse-biological-effects concentration or biologically safe concentration, or no-observable-effects level might lead the unwary to believe that all possible adverse effects were unlikely to occur at concentrations below the one stated. In fact, I have never seen a body of evidence in a scholarly professional journal that would convince reviewers that these assertions had been confirmed in a scientifically sound way. Some more modest but more explicit predictions and validation criteria, for illustrative purposes only, follow. 1. Only the test species is expected to be protected fully in natural systems, and validation means confirming this assumption in the field. 2. Other species than the one(s) actually tested are thought to be protected at the no-observable-effects concentration, and a list of these species inhabiting the natural systems in question is included. Validation is carried out with field observations on all of these species. 3. No adverse effects at the community level of biological organization will occur, and the characteristics used to validate this assumption are listed. Validation may be carried out in microcosms or mesocosms under certain circumstances but should be based on field observations whenever possible. 4. No adverse effects will occur at the ecosystem level of organization, and the characteristics at the ecosystem level used to validate this assumption are listed. Validation in field enclosures or natural systems should probably be mandatory.
By coupling the explicit predictions being made with the explicit end points being used to validate these predictions, a more systematic and orderly process of validation will ensue. Until more hypothesis testing is carried out in the field of hazard evaluation than is in place presently, it is unlikely that the field will get the recognition it deserves.
Interlaboratory Testing of a Standardized Aquatic Microcosm
Authors: Taub FB , Kindig AC , Conquest LL 
Published: February 2009

The “Standardized Aquatic Microcosm” (SAM) Protocol is being tested in three laboratories as well as in the laboratory where it was developed (University of Washington). Each laboratory has used a control and three concentrations of copper sulfate and has completed at least one experiment.
The successional sequence in the controls has consistently included nitrate depletion and an early algal bloom terminated by increases in grazer populations, especially Daphnia. In all experiments analyzed to date, low copper sulfate concentrations were associated with temporary reduction in Daphnia and concurrent algal blooms; at higher concentrations, the algae were inhibited to a greater extent and for a longer duration.
The concept of a “days-weighted-by-variable” statistic (DWV) is introduced to assess variation between experiments. The DWV, as a measure of the center of gravity of a microcosm time trace, is useful to detect shifts in timing under increased copper concentrations.
Evaluation of the Indicator Species Procedure for Deriving Site-Specific Water Quality Criteria for Zinc
Authors: Parkerton TF , Stewart SM , Dickson KL , Rodgers JH , Saleh FY 
Published: February 2009

The indicator species procedure enables modification of a national water quality criterion to account for differences in the biological availability/toxicity of a chemical introduced into site waters. To evaluate this procedure, a case study was conducted with zinc using the Trinity River near Denton, Texas as an example site.
Acute and chronic toxicity tests were performed with Pimephales promelas and Daphnia pulex in both natural river and reference waters. Toxicity results were expressed as a function of both total and soluble metal.
An acute water effects ratio (WER) was used to calculate the site-specific criterion maximum concentration. The site-specific value showed excellent agreement with the national water quality criterion adjusted for the site water hardness when based on total zinc. These findings were altered when toxicity results from a different reference water were used in calculations, but were unaffected if test organisms were not acclimated in site water prior to testing. Three different methods were used to calculate the site-specific criterion continuous concentration, which was found to be up to four times lower than the national criterion. Toxicological differences observed between lab and site waters were reduced when expressed in terms of mean soluble metal.
Additional experiments demonstrated that particulate zinc was not biologically available under test conditions and that soluble zinc may vary in its toxicity. Data also suggest that kinetic factors influence zinc toxicity. The implications of this research for the development of site-specific metal criteria are discussed.
A Method for Evaluating Effects of Toxic Chemicals on Fish Growth Rates
Authors: Crossland NO 
Published: February 2009

Provided that environmental factors and the food supply are not limiting, the growth rate of fish is more or less constant from the fry stage until the onset of maturity. It is independent of the initial size of the fish and the duration of the period between measurements. This paper describes a method which uses the growth rate of juvenile rainbow trout as a sensitive response for evaluating chronic toxicity.
Groups of 16 fish per 40-L aquarium were anesthetized, weighed, measured, and individually marked using freeze brands. Fish were fed a ration of pelleted food equivalent to 4% of wet body weight per day, given in two feeds per day. They were exposed under flow-through conditions to 3,4-dichloroaniline (DCA) at concentrations of 0, 19, 39, 71, 120, and 210 μg/L for a period of 20 days. Effects on length, weight, and growth rates were determined after 14 and 28 days exposure to DCA.
After 14 days there were no significant effects (P &gt; 0.05) on length or weight, but there was a highly significant depression of growth rate (P &lt; 0.01) among fish exposed to the highest concentration of DCA (210 µg/L). After 28 days there were statistically significant effects on length and growth rate at all concentrations between 39 and 210 µg/L, and there was a clear relationship between concentration and response. Growth rate was affected to a greater extent than length, and overall it proved to be a much more sensitive response than either weight or length.