bluuebunny/crossref_metadata_2025_split huggingface dataset:
A Uniform Pure Shear Testing Specimen for Adhesive Characterization
Authors: Weissberg V , Arcan M 
Published: February 2009

A new versatile stiff adherend test specimen is proposed. This specimen induces a uniform pure shear stress state practically free of tension and compression in the adhesive layer. The versatility of the specimen consists in the fact that, by loading the specimen in a rotated position, a mixed mode (MI + MII) or (MI + MIII) may be induced, but the present paper deals only with the pure shear case.
Comparative finite element calculations of stress distributions, especially at the free adhesive edge, and strain-energy-release rates of cracked specimens, were performed. Experimental determinations provided accurate stress-strain curves of the adhesive systems tested as well as direct verifications of the strain-energy-release rate concept in adhesive joints.
Deformations and Strains in a Thick Adherend Lap Joint
Authors: Post D , Czarnek R , Wood JD , Joh D 
Published: February 2009

Displacement fields in a thick adherend lap joint were measured by high-sensitivity moiré interferometry. Contour maps of in-plane U and V displacements were obtained across adhesive and adherend surfaces. Loads ranged from a modest load to a near-failure load. Quantitative results are given for displacements and strains in the adhesive and along the adhesive/adherend boundary lines. The results show nearly constant shear strain in the adhesive, nonlinear strains as a function of load or average shear stress, and viscoelastic or time-dependent response. Longitudinal normal strains in the adhesive are nearly two orders of magnitude less than the shear strains.
With its subwavelength displacement resolution and high spatial resolution, moiré interferometry is especially well suited for deformation studies of adhesive joints.
Special Mixed Finite Elements for Interfacial Stress Analysis of Adhesively Bonded Joints
Authors: Aivazzadeh S , Bichara M , Ghazal A , Verchery G 
Published: February 2009

Various special triangular and rectangular mixed finite elements for the static analysis of adhesive joints are presented. These finite elements take into account the continuity conditions at the interface, including the displacements and transverse stresses as variables, and they are developed for two-dimensional elastic behavior. Two processes have been developed to construct the finite elements through the use of Reissner's variational principle: the elimination process and the relocalization process.
Several numerical examples are presented which illustrate the accuracy of the interface finite elements by comparison with the classical finite elements displacement method.
Stress-Intensity Factors for Corner Cracks in Rectangular Bars
Authors: Raju IS , Newman JC 
Published: February 2009

This paper presents stress-intensity factors for a wide range of quarter-elliptical corner cracks in rectangular bars. Cracked configurations were subjected to remote tension, in-plane bending, or out-of-plane bending. The ratio of crack depth to crack length ranged from 0.2 to 2; the ratio of crack depth to specimen thickness ranged from 0.2 to 0.8; and the ratio of crack length to specimen width ranged from 0.04 to 0.8. The configurations analyzed varied from a square bar to a very wide plate. These particular crack configurations were chosen to cover the range of shapes and sizes that have been observed to grow in experiments conducted on rectangular bars. The stress-intensity factors were calculated by a three-dimensional finite-element method. Finite-element models employed singularity elements along the crack front and linear-strain elements elsewhere. The models had about 7000 degrees of freedom. Stress-intensity factors were calculated using a nodal-force method.
The present results were compared with other numerical results for a quarter-circular corner crack configuration. The present results along the interior of the crack generally agreed within 3% with those from the literature. Some larger differences (3 to 13%) were observed near the intersection of the crack front and the free surfaces (in the boundary-layer region). Thus, analyses were also performed to study the effect of mesh refinement in the boundary-layer region and the influence of Poisson's ratio on the distribution of stress-intensity factors.
Dynamic Measurement of Crack-Tip Opening Displacement
Authors: Sharpe WN , Waclawiw Z , Douglas AS 
Published: February 2009

Crack opening displacements were measured at two positions very close to the tip of a crack in three-point bend specimens that were loaded explosively. Indentations were placed across the fatigue precrack at locations 100 μm and 200 μm behind the tip. These indentations, when illuminated with a laser, generate fringe patterns in space, and the motion of these fringes is proportional to the displacement between them. The fringe motion was monitored with photomultiplier tubes and an oscilloscope and converted to crack-tip opening displacement (CTOD). Explosive loading of the specimens generated stress-intensity factors increasing at a rate of 3 × 106 MPa m1/2/s.
A soft tool steel was used as a prototype material for this technique development because its material response is similar to the tough materials that are to be studied in the future. Both CTOD and crack-tip opening angle were measured in a search for an appropriate measure of resistance to dynamic fracture. Quasi-static tests were also conducted using the same measurement techniques plus a clip gage. A dynamic critical stress-intensity factor (not plane strain) was determined using a slope reduction procedure based on the static tests. The results show little change in dynamic fracture toughness for this material with increasing loading rate. The experimental techniques show promise for further dynamic studies.
Line Spring Method of Stress-Intensity Factor Determination for Surface Cracks in Plates Under Arbitrary In-Plane Stresses
Authors: Yang CY 
Published: February 2009

The elastic line spring model is updated to accept arbitrarily distributed loads acting on plates to allow determination of stress-intensity factors of surface cracks under various types of loading, such as thermal stress and residual stress. The governing integral equations are modified, owing to the inclusion of the nonlinear loads. Careful numerical treatment and computer programming can make the analysis very efficient. It has been shown that a 16-point KI-distribution along a crack front can be obtained within 0.025 s (central processing unit) using Cray computer systems, which is at least four orders of magnitude faster than the finite-element analysis of the same problem. The outstanding computational efficiency makes the line spring model practical for many time-dependent fracture analyses in engineering applications.
Cracks with different shapes, namely, semielliptical, part-circular, and triangular cracks are investigated, and the results agree very well with the existing finite-element analysis solutions.
Fatigue Crack Propagation Behavior and Damage Accumulation Relationships in an Aluminum Alloy
Authors: O'Connor BPD , Plumtree A 
Published: February 2009

Damage accumulation was studied in strain-cycled aluminum Alloy 6066-T6 cylindrical fatigue specimens. The damage was assessed by measuring the ratio of cracked to cross-sectioned areas and monitoring the apparent modulus changes after different life fractions. Both these methods were found to correlate well. Stage II fatigue crack propagation was established when the surface crack length had attained a critical value of approximately 700 μm. A linear relationship with crack depth ensued. Below this value, the crack depth was small by comparison and damage levels were below 1%. Over 60% of the fatigue life was spent in Stage I (or surface-dominated) crack growth where the cracked area was insignificant. From a practical point of view, damage was considered to begin after this life fraction and a damage mechanics model was successfully applied to the experimental results.
Damage accumulation rates were related directly to crack growth rates as a result of the relationship between damage and the cracked area. Hence, damage accumulation may be described by a Paris type of equation.
Tests at low strains involving a large amount of elasticity (elastic-to-plastic strain ratios of the order of 600) were found to maintain low damage levels over longer life fractions compared with higher strain cycled tests (with ratios of 25 and less). Damage at a given life fraction in tests with elastic-to-plastic strain ratios below approximately 25 were found to be similar. Under these conditions Miner's rule may be applied.
Fatigue Crack Growth at High Load Ratios in the Time-Dependent Regime
Authors: Nicholas T , Ashbaugh NE 
Published: February 2009

Experimental crack growth rates were determined in Inconel 718 middle cracked tension [M(T)] specimens at 649°C under conditons of high frequency (10 to 100 Hz) and high load ratio, R. Under these conditions, the material experiences cycle-dependent crack growth as well as time-dependent crack growth. At very high R values approaching unity, the observed growth rates are lower than those obtained under sustained load at the same mean load in the absence of the superimposed cyclic loading. Tests on compact tension [C(T)] specimens at lower frequencies were used to demonstrate the existence of three regions of behavior—cycle-dependent, mixed mode, and time-dependent.
A linear cumulative damage model was used to predict the growth rates due to combined cycle-dependent and time-dependent mechanisms. The model was developed from 427°C data for the cyclic term and sustained load crack growth data for the time-dependent term. Although the model cannot predict the synergistic effect at high R, it provides a reasonable representation of much of the data. The authors conclude that the use of low-temperature data for the cyclic term is inadequate for representing the threshold values and growth rates at low ΔK values at the higher temperature.
An Evaluation of the Screening Level Concentration Approach for Validation of Sediment Quality Criteria for Freshwater and Saltwater Ecosystems
Authors: Neff JM , Cornaby BW , Vaga RM , Gulbransen TC , Scanlon JA , Bean DJ 
Published: February 2009

The U.S. Environmental Protection Agency (EPA) has initiated an effort to develop sediment quality criteria for both freshwater and marine ecosystems. The Screening Level Concentration (SLC) approach is one of several methods EPA is evaluating for calculating sediment quality criteria. The SLC approach uses field data on the cooccurrence in sediments of benthic infaunal invertebrates and different concentrations of the nonpolar organic contaminant of interest. The SLC method is designed to estimate the highest concentration (normalized to sediment organic carbon concentration) of a particular nonpolar organic contaminant in sediments that can be tolerated by approximately 95% of benthic infauna. As such, the SLC value could be used in a regulatory context as the concentration of a contaminant in sediment that, if exceeded, could lead to environmental degradation.
This paper describes the method for calculating the SLC and evaluates the SLC approach empirically for nonpolar organic contaminants in freshwater and marine sediments in terms of its statistical properties and its dependence on the characteristics of the data base. SLCs are calculated for five contaminants in freshwater sediments (total polychlorinated biphenyls (PCBs), dichlorodiphenyl trichloroethane (DDT), dieldrin, chlordane, and heptachlor epoxide) and nine contaminants in saltwater sediments (total PCBs, DDT, naphthalene, phenanthrene, fluoranthene, benz(a)anthracene, chrysene, pyrene, and benzo(a)pyrene). The method used to calculate SLCs is illustrated for total PCBs in freshwater and saltwater sediments. Differences in SLC values for PCBs and DDT between freshwater and saltwater sediments are discussed. The SLC approach demonstrates sufficient merit to warrant further evaluation and elaboration. Given a large enough data base and minor modifications of the methods for calculating an SLC for a specific contaminant, the approach can provide a conservative estimate of the highest concentration, normalized to sediment organic carbon, that 95% of the benthic infauna can tolerate in sediment.
Factors Affecting the Bioavailability of Hexachlorobiphenyls to Benthic Organisms
Authors: McElroy AE , Means JC 
Published: February 2009

The purpose of this study was to simultaneously evaluate several key factors which potentially affect the accumulation of hydrophobic pollutant compounds in sediment by benthic organisms. These factors were: (1) organic carbon content of the sediment; (2) equilibration time of the pollutant with the sediment; and (3) feeding strategies of the organism. [14C-U]2,4,5,2′,4′,5′-hexachlorobiphenyl (HCBP) was equilibrated with sediments from Narragansett Bay, RI containing either 4 or 2% total organic carbon for periods of either one or four weeks. Biological availability of the compound was assessed by following the kinetics of HCBP uptake into either the omnivorous deposit feeding polychaete Nephtys incisa or the deposit feeding bivalve Yoldia limatula exposed to bedded sediment.
In an attempt to normalize bioaccumulation data for differences in the lipophilic reservoirs between sediment and organism, an apparent preference factor (APF) was calculated comparing body burdens normalized to % lipid with sediment concentrations normalized to % total organic carbon (TOC) APF = (HCBPs/$TOC)/(HCBPo/%lipid) For both organisms, APF reached a constant value within 20 days. Length of isotope incubation with sediment had no observable effect on either the rate of approach to a constant APF or the value of APF reached. Even after normalizing with the preference factor calculation, significant differences were still evident between bioaccumulation from the two sediment types and between bioaccumulation from the same sediment by Yoldia and Nephtys. These data indicate that in addition to the influence of sediment TOC and lipid content of the organism, intrinsic properties of sediment and biological properties of the organism influence the transfer and bioaccumulation of hydrophobic compounds.
A Review of Inter- and Intralaboratory Effluent Toxicity Test Method Variability
Authors: Rue WJ , Fava JA , Grothe DR 
Published: February 2009

Due to the increased emphasis on the use of aquatic toxicity tests to evaluate the quality of complex effluents, there is a need to objectively evaluate the precision of effluent toxicity test methods. Based upon an extensive search of the published and unpublished literature (available through April 1985), the intralaboratory and interlaboratory precision of effluent toxicity test methods was evaluated.
Most of the inter- and intralaboratory studies obtained address the acute toxicity of effluents to three standard test organisms: Daphnia spp. (water fleas); Salmo gairdneri (rainbow trout); and the marine bacterium Photobacterium phosphoreum (Microtox). Only limited data exist for Pimephales promelas (fathead minnows); Mysidopsis bahia (opposum shrimp); and Cyprinodon variegatus (sheepshead minnows). Based on LC50 or EC50 values for 141 effluents for which interlaboratory data were available, 81.6% had coefficients of variation ≤40%, and 74.5% had coefficients of variation ≤30%. For 46 effluents for which intralaboratory data were available, 89.2% had coefficients of variation ≤40%, and 89.2% also had coefficients of variation ≤30%. To put this variability in perspective, coefficients of variation for these replicated toxicity tests with effluents are compared to published precision estimates for analytical chemistry methods.
Techniques for Environmental Modeling of the Fate and Effects of Complex Chemical Mixtures: A Case Study
Authors: Vigon BW , Wickramanayake GB , Cooney JD , Durell GS , Pollack AJ , Shook T , Frauenthal M 
Published: February 2009

A mathematical model along with physical models were used to determine the fate of complex chemical mixtures released to the multimedia environment. Transport and transformation of phosphorus compounds generated during munition testing were studied by employing the Environmental Protection Agency's (EPA) TOX-SCREEN model. The species modeled were phosphine and a representative linear condensed polyphosphate (LCP). The model predicted that a significant fraction of phosphine was volatilized. The fate of LCP is mainly governed by the sorption capacity of soils. The data gaps identified during the preliminary modeling phase included estimates of polyphosphate sorption capacity onto soil.
Laboratory experiments indicated that the adsorption of total phosphorus onto sand was well represented by Freundlich isotherms. Batch and column studies indicated that sand enhances the oxidation of burn products to orthophosphate in the aqueous environment. The leachate generated from the combustion residue was highly toxic to Daphnia magna. Passage of the leachate through a sand/gravel column removed the toxic compounds and/or transformed them to less toxic products.
A combination of mathematical and physical modeling and toxicity monitoring proved highly effective in evaluating and mitigating potential environmental impacts of phosphorus obscurant smokes.
Field Verification of Multispecies Microcosms of Marine Macroinvertebrates
Authors: Livingston RJ 
Published: February 2009

A five-year study was carried out to determine the feasibility of using multispecies microcosms of infaunal macroinvertebrates to predict the responses of estuarine systems to toxic substances. Criteria were developed to evaluate the field validation of laboratory microcosms. Experiments carried out in the Apalachicola Bay system in Florida demonstrated that infaunal macroinvertebrates can be established for short periods (five to six weeks) and that the microcosms can be used to simulate certain features of natural field assemblages.
Water quality in the microcosms essentially paralleled that in the field, although variation of certain water features and sediment characteristics was noted. These laboratory artifacts were apparently caused by the isolation of the microcosms from natural phenomena of the estuarine environment that were not replicable in the laboratory. Physical habitat features and biological responses in the study area were extremely complex and highly variable in space and time. Factors such as water and sediment quality, predator-prey relationships, recruitment, and dominance relationships among infaunal populations, influenced the community structure of benthic organisms in the laboratory and the field. The relative influence of physical and biological factors varied considerably between habitats and through time. Consequently, the extent to which the laboratory microcosms paralleled field conditions depended to a considerable degree on the time of testing and dominance/recruitment features of the system in the source area. Species richness in the laboratory microcosms appeared to be a good indicator of field conditions. Multispecies tests have certain advantages over single-species tests in terms of the expanded scope of evaluation. However, results from such experiments should be interpreted within established limits of natural environmental variation. Each microcosm should undergo a thorough calibration with field conditions to qualify the influence of laboratory artifacts and to identify the potential problems associated with isolation from key controlling factors in the field.
A Toxicity Assessment of Tar Sands Tailings
Authors: Yong RN , Ludwig RD 
Published: February 2009

Toxicity assessment was conducted on the liquid fractions of waste tailings generated from the hot water extraction process employed in recovering oil from the Athabasca tar sands. Indices of toxicity employed included a mixed culture of microorganisms indigenous to a major river flowing in the vicinity of containment ponds used to store the waste tailings. Toxicity assessment employing the mixed culture of microorganisms was conducted by monitoring the growth of microbial suspensions through turbidity measurements. Other indices of toxicity employed were the freshwater green alga Selenastrum capricornutum and the bacterium resembling Photobacterium phosphoreum. The liquid fractions considered for toxicity assessment included those of both fresh tailings and aged tailings. In addition, toxicity assessment was conducted on the fluid emanating from accumulated sludge in the containment ponds.
Fresh tailings were observed to be highly toxic to all indices of toxicity employed. At a concentration of 40% by volume, fresh tailings were observed to support on average less than 38% of the growth observed in controls for the mixed culture of river microorganisms, while at a concentration of 25% by volume the fresh tailings brought about an average light emission reduction of greater than 65% in the bacterium resembling Photobacterium phosphoreum. Toxicity assessment with Selenastrum capricornutum gave an interpolated EC50 value of 24% by volume.
Aged tailings were observed to exhibit only slight toxicity to Selenastrum capricornutum and the bacterium resembling Photobacterium phosphoreum and no toxicity to the mixed culture of river microorganisms. In fact, aged tailings at a concentration of 40% by volume appeared to stimulate growth in the mixed culture of river microorganisms over that observed in the controls. At 100% concentration by volume, an average light emission reduction of 16% was observed for the bacterium resembling Photobacterium phosphoreum, and an average 33% inhibition of growth relative to controls was observed for Selenastrum capricornutum.
Emanated sludge fluid was observed to be highly toxic only to the alga Selenastrum capricornutum with an interpolated EC50 value of 29% by volume. At a concentration of 40% by volume, the emanated sludge fluid was observed to apparently stimulate growth in the mixed culture of river microorganisms over that observed in the controls. At a concentration of 100% by volume, an average light emission reduction of only 13% was observed for the bacterium resembling Photobacterium phosphoreum.
The results suggest that, although initially very toxic, the waste tailings undergo a self-detoxification process with time. This may have important implications with regard to measures which might be implemented in the containment and treatment of the tailings.
Availability and Access to Ground-Water-Related Information and Data
Authors: Tockstein CD , Dorwart BC 
Published: February 2009

For many years it has been apparent that the ever-increasing volume of information and data accumulated in all fields of human experience is far outpacing the individual's capacity to absorb even a small part of it. It is, in fact, impossible to keep current in one's own field of expertise without a systematic approach to screening, cataloging, and retrieving pertinent information. In recent years, the use of computer technology to create automated systems has provided a means to at least partially mitigate the problem.
ASTM Subcommittee D18.95 on Information Retrieval and Data Automation has, as part of its scope of responsibilities, the charge to keep current on the status of such systems and report this information to the geotechnical community. This paper is a means of fulfilling that charge by reporting the availability and accessibility of ground-water information known to the subcommittee.
Information available to the subcommittee shows that a well-coordinated program of water-data collection and dissemination is currently ongoing under the auspices of the U.S. Geological Survey's Office of Water Data Coordination. The interests of the ground-water community can best be served by encouraging the continued and expanded use of this program to provide a means for all to benefit from the collective experience and knowledge available.