bluuebunny/crossref_metadata_2025_split huggingface dataset:
Statistical Approaches to Screening Hazardous Waste Sites for Toxicity
Authors: Thomas JM , Athey LA , Skalski JR 
Published: March 2009

The kinds of questions bioassays can answer, as well as their advantages, are given. The ability to answer questions, such as “where is the waste?” or “is it toxic?” results from field studies based on twelve procedural steps for conducting remedial action studies. Simple or stratified random, systematic, and judgment sampling are presented as three possible paradigms for field sampling.
Bioassay results from two previously reported field studies illustrate how maps of toxicity can be prepared based on systematic sampling and show how cleanup decisions can be made using bioassay results based on few samples.
In the first study, logarithmically spaced soil samples (0–15 and 15–30 cm depths) were obtained along four parallel transects (90 m long and 15 m apart) at the Rocky Mountain Arsenal. A total of 72 soil samples (36 at each of two depths) were subjected to phytoassay using lettuce seeds; most samples were also subjected to Daphnia, Microtox, algal, earthworm, and lettuce root elongation bioassays. These latter bioassay results (exception earthworms) were inconclusive regarding toxicity, but allowed us to ignore several classes of compounds (i.e., water-soluble heavy metals, herbicides, and insecticides) single prior results [1] using pure chemicals showed depressed algal growth in the presence of these contaminants.
In order to depict the spatial pattern of observed seed mortality at each depth, we used kriging (a statistical technique developed for use in the mining industry) to produce contour maps. The results clearly showed that lettuce seed mortality was higher in the 15–30 cm fraction, that waste-trench soil was highly phytotoxic, and that toxicity decreased as a function of distance from the trench. In addition, we found that mortality contours produced by kriging could be useful in site cleanup decisions.
The second study used a series of water and sediment samples collected from a narrow stream adjacent to a wood treatment plant in Canton, Mississippi. Both creosote and pentachlorophenol were used for wood treatment. Sediment samples (15 cm) were collected every 20 m in the visibly contaminated zones. Based on sample linear interpolation of bioassay results, we found that different bioassays led to different conclusions regarding the toxicity of different areas, suggesting that contaminants other than creosote may have caused the observed toxicity. Moreover, chemical analysis was an inaccurate predictor of toxicity.
Evaluation of SW-846 Cold-Vapor Mercury Methods 7470 and 7471
Authors: Beckert WF , Messman JD , Churchwell ME , Livingston RL , Sgontz DL , Wallace GF 
Published: March 2009

The protocols for Methods 7470 and 7471 in the SW-846 methods manual are designed for the cold-vapor atomic absorption spectrometric (CV-AAS) determination of total mercury in aqueous (extracts, wastewater, ground water, etc.) and solid (soils, sediments, sludges, etc.) materials, respectively. Aqueous samples are digested with a combination of nitric and sulfuric acid plus permanganate and persulfate solutions at elevated temperature; solid samples are heated either on a steam bath with aqua regia and permanganate, or in an autoclave with sulfuric acid, nitric acid and permanganate. The mercuric ions in the digests are then reduced with hydroxylamine, and the elemental mercury is aerated into the AAS cell, either in a closed (recirculating) or an open system, where the absorption at 253.7 nm is determined.
The topics of this presentation are the results of a performance evaluation study of these methods conducted, without and with changes, by the Battelle Columbus Division Laboratory. The methods were evaluated using aqueous and solid environmental samples of homogeneous and known compositions in order to assess the accuracy and precision of the methods without introducing uncertainties due to sample inhomogeneities. The methods, as originally written, were satisfactory for the analyses of samples containing relatively high concentrations of mercury. However, the method quantification limits for the closed and open systems were inadequate for the determination of mercury in environmental samples such as ground-water samples, when low concentrations were encountered. Spectral interferences which are caused by nonspecific absorption of the analytical radiation degraded the accuracy of the recirculating CV-AAS method.
The protocols in Methods 7470 and 7471 were modified to improve mercury detectability and to minimize the additive effect of nonspecific background absorption. The use of an amalgamation CV-AAS system operated in an open configuration resulted in an improvement of one order of magnitude in instrumental detection limit for mercury over the recirculating method. The results of the analyses of four reference sediment materials and a simulated aqueous waste sample by the amalgamation CV-AAS method indicated acceptable accuracy and precision for most of the environmental samples tested. As expected, the amalgamation CV-AAS method revealed no spectral interferences resulting from nonspecific absorption of the analytical radiation by organic vapors.
The modified protocols are at present the subject of a multilaboratory evaluation with the Battelle Columbus Division Laboratory as the coordinating laboratory. Seven laboratories are participating in this study.
Application of the Method of Caustics to J-Testing with Standard Specimen Geometries
Authors: Sanford RJ , Judy RW 
Published: March 2009

The optical caustic technique offers unique opportunities for experimental measurement of fracture parameters under conditions where conventional instrumentation either can not be used or is not available. The apparent simplicity of the method has attracted the interest of metallurgists and materials scientists. However, there are subtle problems with the method which complicate the interpretation of results. Some of the problems have not been fully explored and others need clarification before the method can be routinely applied. Of particular concern is the fact that existing theories for caustic behavior apply only in special cases which are rarely, if ever, attained in test specimens of practical dimensions for fracture testing. Nonetheless, the potential promise of the method justifies a systematic study of the influence of various parameters, both physical and optical, on the observed behavior of the caustic.
In previous work, the authors demonstrated that there is a correlation between the measured caustic diameter and the value of the J-integral parameter obtained from mechanical measurements for planar 1T compact tension specimens in various steels, subject to some restrictions. As might be expected, this correlation did not agree with existing theoretical relations since the theories are all based on plane stress assumptions. In the present paper, these correlations are studied further and the influence of imaging distance and specimen thickness examined in detail. In addition, the characterization of caustic behavior in standard bend specimens is investigated.
For these studies, a new four-lens caustic camera was used which permits the simultaneous determination of four caustics with varying image distances at each increment of applied load. With the aid of this camera, sufficient data were obtained to determine empirical relations for the calculation of the J-integral values from optical measurement of the caustic.
Impact Fracture of a Tough Ductile Steel
Authors: Douglas AS , Suh MS 
Published: March 2009

The impact fracture of a tough ductile material is examined by comparing the results of static and dynamic viscoplastic finite element computations with experimental observations of the crack tip opening displacement (CTOD) during static and dynamic (impact) fracture. Experiments measured the relative displacement of two small indents 100 μm behind a fatigue crack tip in a three-point bend specimen to determine the CTOD as a function of load (in static tests) or as a function of time (in dynamic tests).Static computations show that a two-dimensional simulation can capture both the overall structural response, as measured by boundary quantities (such as the applied load and the crack mouth opening displacement), and the near-tip CTOD when crack closure is accounted for. Dynamic finite element simulations also use a two-dimensional model of the three-point bend specimen, but must include the projectile and loading tup to account for the complex stress wave interactions generated during impact loading in order to simulate the CTOD versus time response. Since the finite element model correlates with the observed CTOD history, it can be used to determine relevant field quantities, such as the J-integral, as well as stresses and strains of interest.The finite element model shows that it is essential to include the effects of viscoplasticity in order to capture the correct CTOD response in the dynamic experiments. These calculations show that the rate of change of the stress intensity factor is K ∼ 5 × 106 MPa √m/s in the impact fracture tests. The fracture initiation time has not been unambiguously determined; therefore a unique fracture toughness has not been established.
Dynamic Key-Curves for Brittle Fracture Impact Tests and Establishment of a Transition Time
Authors: Böhme W 
Published: March 2009

Impact tests with precracked bend specimens were performed, and the crack tip loading was measured utilizing the shadow optical method of caustics and high-speed photography. Some results are presented in comparison to a quasi-static solution for the crack loading history, which is based on a simple mass-spring model. The deviations obtained are a quantitative measure of dynamic effects acting at the crack tip and they define dynamic correction functions kdyn. In a normalized form these time-dependent functions are very general curves for impact tests; therefore they can be considered as dynamic key-curves. They allow the prediction of the dynamic crack tip loading history for arbitrary impact test conditons so far as the usual restrictions of the linear elastic fracture mechanics are fulfilled.
The dynamic key-curves show clearly the decrease of dynamic effects with increasing time, allowing us to define transition times tdyn. For times larger than tdyn the crack loading history can be described sufficiently accurately by the quasi-static solution. The established transition time tdyn is compared with transition times defined by Ireland and by Nakamura, Shih, and Freund.
Effects of Warm Pre-Stressing on the Transition Toughness Behavior of an A533 Grade B Class 1 Pressure Vessel Steel
Authors: Lidbury D , Birkett P 
Published: March 2009

It is now well recognized that pre-loading a ferritic steel structure at a temperature above its ductile-brittle transition range may result in an effective increase in toughness on loading at a lower temperature where fracture occurs by cleavage. Of particular significance is the fact that cleavage failure has never been reported in a cracked structure at a low temperature, following pre-loading at a higher temperature, for cases where the applied crack driving force was constant or decreasing with time. This is the basis of the so-called “conservative” warm pre-stressing (WPS) principle. Although this principle is of considerable practical importance, much work is still needed to further understand all aspects of WPS phenomena in order that analysts be better able to assess their effects quantitatively in safety cases.
In the present work, WPS experiments have been carried out using 20-mm-thick, plain-sided compact specimens sectioned from 150-mm-thick A533 Grade B Class 1 pressure vessel steel. The effects of load-unload-cool-fracture (LUCF) and load-cool-fracture (LCF) pre-loading cycles (KWPS ≈ 100 to 350 MPa √ m; TWPS = 25 or 290°C) on cleavage fracture resistance have been investigated over a range of temperatures spanning the ductile-brittle transition range.
A particular objective of the work was to investigate the combined effects of WPS and strain ageing on transition toughness behavior; therefore, in addition to WPS experiments, tests were carried out on “virgin” specimens to obtain base-line data and on specimens sectioned from material which had been uniformly pre-strained by 2% at ambient temperature and then aged for 1.25 h at 290°C to obtain control data.
The main results were as follows. The validity of the conservative WPS principle was confirmed: In every test performed, an increase in loading was required to cause cleavage fracture at low temperature following a severe pre-load at a higher temperature. Moreover, in the case of pre-loading carried out at 25°C, conferred WPS margins were observed even for those tests where pre-loading had resulted in ductile tearing (0 ⩽ Δa ⩽ 1.0 mm) under conditions of ligament yielding; and the Case 1 and Case 2 solutions of Chell's Q1 -integral theory of WPS yielded reasonably accurate predictions of final fracture. A deleterious effect of pre-loading at 290°C on effective transition toughness below a level of ≈ 200 MPa√m was demonstrated by a combination of control and LUCF and LCF WPS data, and found to be consistent with the expected embrittling effect of strain ageing. However, all toughness data generated by the study were bounded by the ASME KIc versus temperature curve indexed to the value of RTNDT (=-30°C) appropriate to the material in the non-strain-aged condition.
Unique Elastic-Plastic R-Curves: Fact or Fiction?
Authors: Etemad MR , Turner CE 
Published: March 2009

A simple model is presented for the effect of size and geometry on fracture toughness when represented as J-R curves in the fully plastic region. The model, which is little more than dimensional analysis, refers to growth beyond anyJ-controlled regime. It suggests that the abscissa of a J-based R-curve should be Δa/c, where c may be thickness, ligament, or material toughness (expressed as a plastic zone size) according to circumstance. The analysis is consistent with the well known picture in the LEFM regime where thickness is the only geometric term that affects toughness.
Comparison is made with many published results, in most cases satisfactorily. The agreement is best for tests of various ligament widths with constant thickness. The reason for this is the limited understanding of how the shear lips develop before a steady-state pattern of growth is reached and the likelihood that the controlling factor may change when thickness is a variable. Since for the fully plastic state the increment of work from which toughness is derived involves only the limit load and dq/da, the relation between an increment of displacement and the corresponding crack growth, the latter seems to be the factor that contributes most to the differing trends of fully plastic J-R curves as initial geometry is varied. The near total lack of published data for dq/da needs urgent remedy if these geometric effects are to be understood.
Finite Element Meshing Criteria for Crack Problems
Authors: Gerstle WH , Abdalla JE 
Published: March 2009

Rules for the meshing of finite element problems with elastic cracks have never been established. Therefore finite element results for crack problems presented in the literature are of uncertain accuracy. This paper establishes the finite element meshing criteria, based upon a “least dimension” concept, necessary to calculate mixed-mode stress-intensity factors in linear elastic crack problems to a pre-specified accuracy.
Finite element convergence studies, using meshes which consist of eight-noded quadrilateral elements and corresponding six-noded quarter-point singularity elements, are presented for several benchmark problems with known stress-intensity factor solutions. It is assumed that the stress-intensity factors are extracted from the analysis using the displacement correlation method, a common practice in the analysis of mixed-mode problems.
The convergence studies give the analyst valuable information about meshing requirements for arbitrary crack problems. In performing a convergence study for such analyses, three key meshing parameters associated with a given crack tip must be considered: size of the crack tip elements, number of crack tip elements surrounding the crack tip, and size of regular elements near the crack tip. Recommendations for each of these three parameters to achieve an efficient mesh and a prespecified accuracy are presented.
Performance Test Methods for Geomembranes and Geocomposites Used in the Design of Waste Containment Facilities
Authors: Sprague RT , Frobel RK 
Published: March 2009

During the design process for today's generation of waste containment facilities, the design engineer must consider the use of geosynthetics, whether required by regulatory guidelines or sound engineering judgement. Just as with other civil engineering materials, geosynthetics are tested and evaluated using a variety of test methods.
This paper describes three performance test methods, two of which are draft test methods which are currently being used to evaluate performance properties of geomembranes and selected geocomposites: 엯 Wide strip tensile test; 엯 Direct shear test; and 엯 Large scale hydrostatic pressure test.
The paper will attempt to correlate performance test methodswith actual field performance based upon case histories of success and failure in geomembrane systems.
Three Dimensional, Axi-Symmetric Geomembrane Tension Test
Authors: Koerner RM , Koerner GR , Hwu B-L 
Published: March 2009

Presented in this paper are details of a three dimensional, axi-symmetric, tension test used to determine the stress-vs-strain behavior of geomembranes. From this data the modulus, strength and elongation can be obtained. After evaluating the effect of load rate, the accuracy of the test was illustrated by a series of 10 tests on VLDPE geomembranes. This test series resulted in a standard deviation of approximately ± 10%. A variety of different HDPE geomembranes were evaluated with only nominal differences resulting from different manufacturing processes. Lastly, a variety of different geomembrane types were tested and compared to one another. All of these test results show a marked contrast to the usually performed one dimensional tension tests and result in substantially different behavioral trends.
The test details and procedures are presented along with the theory that is required to convert the pressure-vs-deflection readings into stress-vs-strain values. The test is recommended for the type of out-of-plane loading conditions that occur at the bottom of reservoirs and landfills, and for liners used for covers over subsiding landfills and other compressible subgrade materials.
Direct Shear Friction Testing for Geosynthetics in Waste Containment
Authors: Bove JA 
Published: March 2009

Sliding stability for landfills, heap leach pads and caps constructed using geosynthetics is of critical importance for both short and long term performance of these facilities. For layered facilities, instability along critical slip planes must be considered for construction and operation of the facility.
The direct shear friction test, now being developed under ASTM D35, is the test used to generate important performance data for use in stability determinations.
This paper addresses the main elements of direct shear friction testing and analysis including discussions on the required test apparatus, specimen preparation and soil placement. Differences in testing geosynthetics in contact with other geosynthetics or soils are highlighted. Sources of potential bias in test data are discussed along with recommended solutions. Interpretation of direct shear friction data for use in performance evaluation is included.
Biological Activity and Potential Remediation Involving Geotextile Landfill Leachate Filters
Authors: Koerner GR , Koerner RM 
Published: March 2009

This paper presents the results of a biological growth study in geotextile filters used in landfill leachate collection systems. After reviewing the first year's activity, a completely new experimental approach has been taken. Using 100 mm diameter columns for the experimental incubation and flow systems, the effects of six landfill leachates are evaluated. Aerobic and anaerobic states, four different geotextiles, and soil/no soil conditions above the geotextiles are involved in the testing program. This results in 96 individual test columns. Flow data is measured regularly, and over the first six months of evaluation the following trends have been observed. • no clogging (0%–25% flow reduction) 6 of 96 columns = 7% • minor clogging (25%–50% flow reduction) 4 of 96 columns = 4% • moderate clogging (50%–75% flow reduction) 37 of 96 columns = 38% • major clogging (75%–95% flow reduction) 35 of 96 columns = 36% • severe clogging (95%–100% flow reduction) 14 of 96 columns = 15%For two of the landfill leachates, backflushing has been attempted so as to reinstitute flow. This procedure works well for the geotextile alone while not as well for the geotextile/soil columns. The exception is the nonwoven heat set geotextile. All tests are still ongoing and will be dismantled and further investigated at the end of 12 months exposure time. The experimental setup and procedure has been written up as a tentative ASTM test method and is currently in task group review.
Comparison of Short- and Long-Term Toxicity Test Results for the Green Alga, Selenastrum capricornutum
Authors: Versteeg DJ 
Published: March 2009

Algae are important components of many aquatic communities that can be sensitive to effects of aquatic pollutants. Standard algal toxicity tests quantify effects on population growth over 3 to 14 days. These population growth tests are useful for environmental hazard assessment but have limitations. These limitations include test duration, pH, nutrient and metabolite changes during toxicity testing, inability to test at the community level, potential interaction between algal media and test materials, and poor control or understanding of the effects of sample volatilization, sorption, biodegradation, photolysis, or hydrolysis on test material toxicity. These test limitations can be addressed in short-term (&lt;4 h duration) toxicity tests.
Short-term algal toxicity tests were conducted with seven pure compounds and three municipal wastewater treatment plant effluents, and the results were compared to those obtained in a standard four-day population growth test (PGT). The short-term tests involved exposure of the green alga, Selenastrum capricornutum, to test materials and quantification of effects on oxygen generation (O2) in a 30-min exposure and 14CO2 fixation in a 35 min exposure. For test materials used in this research, the short-term tests were consistently less sensitive than the PGT, with ratios of the EC50 (effective concentrations) for the CO2:PGT and the O2:PGT ranging from 1.4 to &gt; 161. However, short-term to long-term test ratios were consistently less than 20, indicating that these tests may be appropriate systems to study effects of test material on algae without the limitations of the long-term test. Although the short-term algal test methods have their own set of limitations for environmental hazard testing, the information gained in the short-term approaches can be used to complement information gained in long-term toxicity tests. This research has demonstrated the relative sensitivities of two short-term tests.