bluuebunny/crossref_metadata_2025 huggingface dataset:
An In Situ System for Evaluating Effects of Toxicants on the Metabolism of Littoral Communities
Authors: Lindblad C , Kautsky U , Kautsky N
Published: February 2009

A portable in situ continuous-flow apparatus for measuring metabolic activities of littoral ecosystems is described. Oxygen, temperature, light, and flow rate are continuously monitored by a microcomputer that redirects the water flow through the measurement chamber from acrylic jars containing the communities. The apparatus is especially designed for experimental purposes, since it is possible to alter the incoming waters by adding various toxicants. The application of the method is presented by an example showing the response of a filter-feeding community to cadmium.

The community showed statistically significant changes in respiration (oxygen) and excretion (nitrogen or phosphorus) as a result of treatment. Calculated ratios—such as the oxygen/nitrogen ratio, oxygen/phosphorus ratio, and perturbation index (PI), which is the relative change due to treatment, taking into account changes in the controls—were more sensitive measurements of sublethal stress than specific values of oxygen, nitrogen, or phosphorus. These indexes are independent of biomass, and PI normalizes synchronic changes in the environment due to light, temperature, and salinity variations, which affect both treated and control systems equally. The design of the system allows the communities to be placed back in the environment after being tested and also allows repeated measurements to be made of possible delayed effects or recovery from perturbations. In this paper, the authors introduce a new measurement of disturbance, the absolute disturbance index (ADI). ADI is the absolute distance between the metabolic activity of an undisturbed system and a disturbed point in a multidimensional space where each dimension represents the PI of a measured parameter.
Fish Behavioral Assessment of Pollutants
Authors: Hartwell SI , Cherry D , Cairns J
Published: February 2009

Avoidance of a blend of four metals (relative ratios: 1.00 copper, 0.54 chromium, 1.85 arsenic, and 0.38 selenium) by schools of fathead minnows (Pimephales promelas) was determined in a steep-gradient, laminar-flow laboratory chamber, an artificial stream supplied with raw river water, and a natural stream. Laboratory avoidance responses were determined seasonally during twelve months for unexposed (control) fish and for two groups of metals-acclimated fish. Field avoidance responses were determined for control fish in the artificial stream in spring and summer and in the natural stream in summer. Field avoidance responses of metals-acclimated fish were determined in the summer in the artificial stream and in the natural stream. The laboratory control fish avoided the metals blend at a concentration of 29 µg/L. The field control fish avoided 71.1 and 34.3 µg/L of total metals in the artificial stream in spring and summer, respectively, and 73.5 µg/L in the natural stream. Laboratory fish acclimated to a total metals concentration of 49 µg/L for three months did not respond to metals levels up to 245 µg/L. Laboratory fish exposed to 98 µg/L of total metals preferred elevated concentrations of 294 µg/L after three months of exposure, mildly avoided 490 µg/L after six months, and were not responsive to concentrations approaching 980 µg/L after nine months of exposure. Field-acclimated fish did not respond to metal blends as high as 1470 and 2940 µg/L in the artificial and natural streams, respectively. Water hardness, turbidity, and physical setting are implicated as possible causative factors in the differences in field avoidance levels among the control fish. The 96-h median lethal concentration (LC50) of the metals blend for acclimated fish was 1.25 and 1.41 times higher than that for control fish for the laboratory and field groups, respectively.
Solubility Parameter Prediction of the Barrier Properties of Chemical Protective Clothing
Authors: Hansen CM , Hansen KM
Published: February 2009

Solubility parameter correlations based on breakthrough times are presented. Solubility parameters have been used previously to estimate whether or not a given permeant will swell or dissolve in a given membrane. Increased solubility is predicted when the solubility parameters for the polymer and penetrant approach each other. Some experimental work is required to characterize either the permeant or the membrane if no data are already available. Since the diffusion coefficients for organic permeants in organic membranes increase exponentially with permeant concentration, there is a very strong dependence of permeation on solubility and therefore on solubility parameters. All other things being equal, penetrants with bulky structures and side groups will permeate more slowly than those with more linear and less voluminous structures. For this reason elimination of permeants with either very small or very large molecular size significantly improves most of the correlations presented, but limits their range of usefulness.
Effects of Grinding Conditions on Fatigue Behavior of 42CD4 Grade Steel; Comparison of Different Fatigue Criteria Incorporating Residual Stresses
Authors: Flavenot JF , Skalli N
Published: February 2009

Fatigue tests carried out at Centre Technique des Industries Mécaniques (CETIM) on a NF 42CD4 grade steel (G 41420) show that grinding parameters such as down feed and the type of wheel have a very clear influence on residual stresses and fatigue limit under plane bending. The stability in fatigue of residual stresses obtained by three grinding conditions were evaluated, using X-ray diffraction methods, in order to introduce values of the stabilized residual stresses into a calculation procedure developed for determining fatigue strength. This analysis contributes to a better knowledge of grinding effects in fatigue and allows the distinction between the respective influence of surface roughness and residual stresses. This project also demonstrates the importance of the reduction of the tensile residual stresses during fatigue, and the relationship between this reduction and the behavior of the metal under cyclic loading.
The New Stone Age: Overcoming the Structural Stumbling Blocks
Authors: Cantor IG , Juda MB
Published: February 2009

Structural aspects of stone cladding systems are described and compared. Conventional set stone, curtain wall, and backup truss systems are investigated schematically, with examples illustrating solutions to the structural problems of differential and lateral building movement in addition to the details of stone attachment. Systems differ in means of accommodation and tolerance of structure and/or cladding movement, resulting in various influences on structural design. System type and stone strength are major factors determining the adequacy of the design of stone attachment details. Comprehensive stone testing is recommended due to the variability of the material and the lack of applicable standards for the thinner stones currently in use. A testing program using standard tests and project-based modifications is described which aides the engineer in interpreting the data for the particular stone and system type under investigation. The interaction between structure and stone cladding system requires structural solutions (based on stone testing) engineered to efficiently and economically address the design's requirements.
Rediscovering Marble and Natural Stone
Authors: Wood RC
Published: February 2009

This paper deals with the application of thin-gauged marble and natural stone on the exteriors of buildings. The paper presents several methods of doing this, such as site applied over concrete and masonry surfaces and over lightweight steel studs using a wire-reinforced, latex modified mortar system.

The paper also presents the latest technology in exterior cladding utilizing lightweight steel panels, constructed off site where marble or natural stone may be applied to portland cement boards with a latex polymer modified mortar adhesive system. Detailed drawings of the applications are included as well as photographs of projects in various stages of construction.
The Modern Thermogravimetric Approach to the Compositional Analysis of Materials
Authors: Earnest CM
Published: February 2009

Thermogravimetry (TG) is an analytical technique that monitors the mass of a substance as it is subjected to a controlled temperature program. TG is the modern day frontier of the much older and well-established technique of gravimetry. Although many compositional analyses may be performed by conventional gravimetry, thermogravimetry offers a more rapid method because of the smaller sample size and faster heating rates. Thus, special instrumentation requirements are imposed on the more modern, rapid, and automated thermogravimetric method. Many commercial TG systems are available. The major difference in these are in the furnace (size, design, and positioning with respect to the furnace tube and sample specimen), degree of computerization, direction of purge gas flow (horizontal or vertical) with respect to the sample specimen, and microbalance type and sensitivity. Recent years have brought computerization of data handling as well as many of the hardware components of the technique. This paper will present and discuss the role of the basic components of a thermogravimetric apparatus in performing compositional analysis. Some of the aspects of computerization of the technique will be included.
Using Chemistry in Compositional Analysis by Thermogravimetry
Authors: Gillmor J , Seyler RJ
Published: February 2009

Many of the compositional analysis applications involving thermogravimetry have focused on the determination of concentrations of one or two additives to a polymeric matrix. Paramount to the utility of such a thermogravimetric approach for filled polymers is that the matrix pyrolyzes repeatably, if not completely. Equally important is the understanding of the components constituting the high temperature residue (ash) and how they are derived. Two examples will be addressed in which controlling or understanding the chemistry of the experiment highlights the significance of the above-mentioned factors in achieving useful compositional analyses. In the first example, an ammoniated atmosphere is employed to achieve repeatable pyrolysis of silicone rubber to measure the carbon black filler content. The second example emphasizes the understanding of decomposition chemistry to distinguish two inorganic fillers retained as ash. In this example the evolution of CO2 from CaCO3 is used to identify the calcium oxide portion of the ash in a polystyrene + carbon black + silicone oil + calcium carbonate + titanium dioxide system.
Thermogravimetric Analysis of Sheet Molding Compound Materials to Determine Distribution of Compound Components in Molded Parts
Authors: Allen PJL
Published: February 2009

Thermogravimetric (TG) analysis was used to investigate localized differences in the composition of complex parts molded from sheet molding compound (SMC). Localized differences in composition may arise as the SMC encounters flow restrictions in the mold such as bosses, ribs, and other design features. Conventional SMC is comprised of both mineral fillers and glass reinforcements. Therefore, preliminary work to develop equations relating weight loss to specimen composition and to define significant differences in composition was accomplished using comparisons of matrix and glass reinforced samples. Part sections taken from restricted flow areas of a complex part were then analyzed and SMC charge patterns were varied to evaluate their effect on localized composition. The information collected demonstrates that TG analysis is a viable technique for examining flow restrictions in the molding of SMC.
Compositional Analysis of Light-Duty Motor Bearings in Fuel Pumps
Authors: Pamphilis NA
Published: February 2009

A method of quantitatively determining a number of compounds in light-duty motor bearings has been developed. As a result, large amounts of carbon fibers (about 25% carbon) were found in samples containing polyphenylene sulfide (PPS), inorganic filler, and polytetrafluoroethylene (PTFE) by means of thermal analysis using both thermogravimetry (TG) and differential scanning calorimetry (DSC).

Two different, but related, methods were used to quantitatively determine the contents of the sample. The first, which was nominally called the “indirect approach,” uses DSC for the determination of the polymeric components and TG for the determination of the residue (inorganic fillers or glass). The amount of carbon is then determined based on the difference. The second method, which was nominally called the “direct approach,” uses DSC for the determination of PTFE and TG for the determination of all other components. The agreement between the two methods is good.
Usefulness of Fourier Transform Infrared Spectroscopy in the Analysis of Evolved Gas from the Thermogravimetric Technique
Authors: Khorami J , Lemieux A , Menard H , Nadeau D
Published: February 2009

The usefulness of thermogravimetry has been amply demonstrated for a wide variety of analytical applications. However, in many instances, additional information is required for adequate characterization of the sample and its thermal decomposition behavior. In this respect, the analyses of evolved gases or condensed liquids has been proven a highly useful approach. Among the various physical methods used for the analyses of thermal degradation products, infrared spectroscopy has often been found very powerful, because it is versatile, rapid, and accessible.

In this study, we report a simple and new approach to recover evolved gases and condensed liquids after the thermal degradation of fibrous organic materials, using an infrared gas cell and a polyvinyl chloride (PVC) membrane filter, respectively. The gaseous components were analyzed by transmission Fourier transform infrared (FTIR) and the condensed liquids products were examined directly on the PVC membrane by FTIR in the internal mode.

For that purpose, several types of synthetic fibers have been selected: polyvinyl alcohol, polyacrylonitrile, polyaramids, and polyolefins. The decomposition products from the combustion of the organic fibers, both in the presence and absence of oxygen, are discussed.
PCBs: The Beginning, the Muddle, the End?
Authors: Manger HC
Published: February 2009

Over the years, there have been many changes in the federal regulations regarding PCBs. From the beginning, utility personnel were in a dilemma as to how to deal with the problem.

First, we had trouble realizing that the askarel we were using in our transformers was more than 50% polychlorinated biphenyl, and even if it was, could it possibly be a toxic or a hazard to anyone's health? After all, we and those before us had been up to our elbows in the stuff for years. It may have burned our eyes a little, but as far as we know it did us no physical harm. We also found it was many things in our everyday life, at work and at home.

Soon those of use close to the situation realized that the utility industry, in particular, was in deep trouble. Congress passed the Toxic Substance Control Act in 1976 and singled our PCB to be controlled. Three years later EPA published the first of a number of rules that have changed the way utilities do business. The industry has been forced to spend millions of dollars and countless man-hours dealing with regulations that we questioned from the start and, at best, learned to live with. In addition, the rules change so often it is truly difficult to keep up with them.

This paper tries to take us from the start, thru the confusing muddle of regulations, to where we are today.
Criteria for the Interpretation of Data for Dissolved Gases in Oil from Transformers (A Review)
Authors: Griffin PJ
Published: February 2009

The analysis of gases dissolved in oil has been used as a diagnostic tool for many years to determine the condition of transformers. The criteria used in evaluating dissolved gas-in-oil data are reviewed. The criteria are based on experience from failed transformers, transformers with incipient faults, laboratory simulations, and statistical studies. The interpretation of results is enhanced by including specific information on a particular transformer, including its history. Comparison of a particular transformer of concern with a population of similar transformers provides additional information as regards “normal” gassing behavior. The interpretation of dissolved gas-in-oil data is not a simple matter and requires the integration of numerous criteria. Diagnostic gases for silicone fluids are also discussed.
Methods for Evaluating Solidified Waste
Authors: Hannak P , Liem AJ , Côtè PL
Published: February 2009

A number of methods for characterizing solidified waste are currently being assessed in the EC/EPA/AEC/Industry Cooperative Study. These are short-term laboratory tests which yield information on material properties (bulk density, specific gravity, and moisture content), ability to maintain physical integrity (unconfined compressive strength and weathering resistance—freeze/thaw and wet/dry), potentials for release of contaminants by advective transport (permeability) and dissolution (acid neutralization capacity, Toxicity Characteristic Leaching Procedure—TCLP—and equilibrium leaching), indication of long-term rate of contaminant release (dynamic leaching), and containment mechanisms (sequential extraction). A brief description is given of these tests, their rationale, and their utilization.

Some of the methods were developed elsewhere and have been adopted or adapted with minor modifications. Others have been developed specifically for the cooperative study. Emphasis is thus given to the latter, specifically to the method for quantifying resistance to wet/dry cycling. The development of this method and preliminary results are described, showing the reproducibility and ability to detect differences in weathering resistance of various solidified products.
Round-Robin Study of Leaching Methods as Applied to Solid Wastes from Coal-Fired Power Plants
Authors: Murarka IP
Published: February 2009

In 1979, the Electric Power Research Institute (EPRI) sponsored a multiple laboratory investigation of the variability and reproducibility of the U.S. EPA extraction procedure (EP) used for classifying wastes. In late 1985 and early 1986, EPRI sponsored another round-robin study to compare the results of EPA's new toxicity characteristics leaching procedure (TCLP) with the EP. In this latest study, three laboratories were used to extract and analyze the concentrations of 14 constituents (Ag, As, B, Ba, Cd, Cr, F, Hg, Mn, Pb, Se, SO4, V, and Zn) from seven utility wastes (three fly ashes, two bottom ashes, and two scrubber sludges). The results were evaluated to determine the reproducibility of the two methods, the factors contributing to the variability of the EP and TCLP extracts, and the differences in mean concentrations between the two extract types for the selected wastes. The results show that reproducibility differs by constituent, waste type, and between the two extraction methods. Generally, the concentrations measured in the TCLP results (as measured by the coefficient of variation) are equal to or better than the EP results (for example, for As, B, Cd, Cr, Mn, and V). Differences in the extractions between laboratories accounted for at least 25% of the total variability more frequently for the EP than the TCLP. For the TCLP, the analytical variability components (that is, differences in the analyses between laboratories and differences in analyses of duplicate splits by the same laboratory) accounted for at least 25% of the total variability more frequently.
On Crack Closure in Fatigue Crack Growth
Authors: McEvily AJ
Published: February 2009

A brief review of the various forms of closure is given, and the relative importance of plasticity-induced closure and roughness-induced closure is considered. On the basis of the lack of a thickness effect and an insensitivity to R in the absence of closure it is concluded that plasticity-induced closure plays a relatively minor role in affecting the rate of fatigue crack propagation with the exception of overload effects. A new form of closure, transitional closure is described and is shown to affect importantly the rate of fatigue crack growth upon a change in R ratio. The closure process for a short crack approaching a grain boundary is also discussed.
On the Role of Crack Closure Mechanisms in Influencing Fatigue Crack Growth Following Tensile Overloads in a Titanium Alloy: Near Threshold Versus Higher ΔK Behavior
Authors: Ward-Close CM , Ritchie RO
Published: February 2009

A comparative study has been made of the transient fatigue crack growth rate behavior following tensile overloads at low (near-threshold) and high stress intensity ranges in an α/β-type titanium alloy IMI 550, with specific emphasis of the role of crack closure mechanisms. After tensile overloads, fatigue cracks in both coarse-grained β-annealed and fine-grained α/β microstructures were observed initially to accelerate, followed by significant retardation, before growth rates returned to their baseline levels. The initial acceleration was attributed to an immediate reduction in near-tip closure, as indicated by metallographic sectioning, and a slight decrease in far-field closure, as measured by back-face compliance methods. Subsequent retardation was not associated with marked changes in far-field closure, although there were indications on compliance curves of a second “closure point” at a higher load, suggesting an approximate 50% increase in near-tip closure. Load interaction effects were found to be most severe where specific mechanisms of crack closure were prominant. Thus, the maximum post-overload retardations were seen in the coarse-grained α microstructure, and when baseline stress intensity ranges were close to the threshold ΔKTH, or when the maximum overload stress intensities approached the fracture toughness.
A Comparison of Measurement Methods and Numerical Procedures for the Experimental Characterization of Fatigue Crack Closure
Authors: Allison JE , Ku RC , Pompetzki MA
Published: February 2009

Accurate experimental characterization of the crack closure process is important for a number of reasons, the most important of which may be for its use in developing materials and structures that are resistant to the growth of fatigue cracks. This paper describes the results of an investigation aimed at quantifying the point of crack closure. An α/β titanium alloy, Ti-6242S, was chosen for this investigation because its microstructure can be manipulated to produce large variations in the level of asperity-induced crack closure and is thus an ideal model alloy for understanding this important crack closure mechanism. Comparisons of two “global” compliance techniques (backface strain and crack mouth opening displacement) and a near crack-tip surface technique (two-stage replication) were made. In tests conducted at low stress intensities, all three methods gave nearly identical measurements of crack closure. For the two compliance techniques, different numerical procedures were used to determine the inflection point in the load-displacement curve. The magnitude of and variations in crack closure determined using these compliance methods were found to be strongly dependent on the numerical procedure used. Studies of crack-tip opening showed that in α/β-processed Ti-6242S the crack tip is tightly closed even at positive loads, indicating that plasticity induced closure is the predominant form of closure. In contrast, measurements in β-processed material showed that the crack tip is propped open even when no load is applied to the sample, indicating that closure in this microstructure is asperity-induced.
A Method for Determining Crack Opening Load from Load-Displacement Data
Authors: Carman CD , Turner CC , Hillberry BM
Published: February 2009

The fatigue crack opening load is determined as the tangent point on the ascending load-displacement data between the curved portion and the upper linear region. A model for the “unzipping” behavior of the crack indicats that the curved portion of the load-deflection curve is second order. The opening load is determined by a nonlinear, least squares fit of the data to the model, which optimally locates the tangent point of the two curves. The method provided consistent results for determining opening load Pop for 7475-T731 aluminum using data from a crack tip opening gage.
Three-Dimensional Finite-Element Simulation of Fatigue Crack Growth and Closure
Authors: Chermahini RG , Shivakumar KN , Newman JC
Published: February 2009

A three-dimensional, elastic-plastic, finite-element analysis of crack growth and closure under cyclic loading was developed and used to study the behavior of a crack in a finite-thickness middle-crack tension specimen. The finite-element model was composed of eight-noded isoparametric, hexahedron elements. The material was assumed to be elastic-perfectly plastic. Two load histories, constant-amplitude loading and a single-spike overload, were considered. The crack front was extended one element length per cycle when the applied stress reached the maximum level. The crack was assumed to grow as a straight-through crack.

Results show that during unloading the crack front closes first on the exterior (free) surface of the specimen and closes last in the interior. Under constant-amplitude loading with a maximum applied stress level Smax of 0.25 times the yield stress of the material, the crack-opening stress levels reached a peak value of 0.34 Smax and 0.6 Smax at the interior and exterior regions of the crack front, respectively. The application of a single-spike overload caused an immediate drop in the opening stress level, but as the crack grew, the opening levels (interior and exterior) rapidly rose to values higher than those calculated under constant-amplitude loading. The calculated crack-opening stresses for the exterior and for the interior of the specimen were in quantitative agreement with previous finite-element calculations under plane-stress and plane-strain conditions, respectively. The crack-opening stresses for the interior were much lower than the exterior values.
Fatigue Crack Closure Behavior at High Stress Ratios
Authors: Turner CC , Carman CD , Hillberry BM
Published: February 2009

Fatigue crack delay behavior at high stress ratio caused by single peak overloads was investigated in two thicknesses of 7475-T731 aluminum alloy. Crack closure was measured in middle crack tension specimens with a crack-tip opening displacement gage located one-half of the specimen thickness behind the crack tip. Five overload ratios from 1.23 to 1.5 were investigated. The stress ratio was 0.7. Closure measurements indicated no closure occurred before or throughout the overload plastic zone following the overload. This was further substantiated by comparing the specimen compliance following the overload with the compliance of a low R ratio test when the crack was fully open. Scanning electron microscope studies revealed that crack tunneling and possibly reinitiation of the crack occurred, most likely a result of crack-tip blunting. The number of delay cycles was greater for the thinner mixed mode stress state specimen than for the thicker plane strain stress state specimen, which is similar to low R ratio test results and may be due to a larger plastic zone for the mixed mode case.
Three-Dimensional Aspects of Fatigue Crack Closure in Surface Flaws in Polymethylmethacrylate Material
Authors: Troha WA , Nicholas T , Grandt AF
Published: February 2009

An experimental investigation using a Newton interference method with a transparent polymethylmethacrylate (PMMA) to measure crack opening displacement and closure on surface flaw crack growth is described. Fatigue crack growth tests are conducted on rectangular plates loaded in bending using optical interferometry measurements to map the crack surface opening displacement profiles and define crack opening loads. Results are presented for an experiment of constant applied stress intensity factor along the crack face free surface. The crack opening displacement patterns and measured closure loads are found to be strongly influenced by the formation of a void internal to the crack surfaces.

Three distinct closure loads are identified and measured for surface flaws of various crack lengths. Upon loading the specimen, the first closure load is defined as the load that initially opens the crack free surface. A second closure load corresponds to the opening of the crack tip in the depth direction along the axis of symmetry. The third closure load corresponds to opening of the crack tip along the entire boundary. The crack closure loads, applied and effective stress intensity factors, and crack growth rates are presented as a function of crack length.
Diagnosis of Terra-Cotta Glaze Spalling
Authors: Thomasen SE , Searls CL
Published: February 2009

One of the most common types of deterioration observed in terra-cotta buildings is glaze spalling. This separation of the hard, fairly impermeable glaze from the underlying clay bisque exposes the clay to water infiltration and accelerated deterioration. The mechanisms responsible for glaze spalling are fabrication defects, incorrect installation, environmental exposure, and improper maintenance. The investigation of glaze spalling consists of a field survey, field tests, and laboratory analysis. Once a diagnosis of the causes is made, appropriate preventive measures can be implemented.
Defect, Constitutive Behavior, and Continuum Toughness Considerations for Weld Integrity Analysis
Authors: Matic P , Jolles MI
Published: February 2009

The failure load of a butt-welded T-frame with a lack of fusion defect is predicted and compared with experimental data. Energy density concepts are used to quantitatively describe the material toughness at the continuum scale. Particular attention is given to the determination of base metal and weld metal uniaxial stress-strain curves valid for large deformation. Finite-element results are used to predict the location where the energy density first reaches a critical value, and the corresponding applied load. The predicted initiation site and load compares favorably with the experimental results.
Nonlinear Work-Hardening Crack-Tip Fields by Dislocation Modeling
Authors: Ellyin F , Fakinlede OA
Published: February 2009

The dislocation model is extended to include nonlinear hardening of the cracktip fields. The resulting model is applied to the loaded and unloaded crack. Several factors affecting the cyclic J-integral are discussed, including mean stress, Baushinger effects, and the applied far-field strain energy density.
Evaluation of Attempts to Predict Large-Crack-Growth J-R Curves from Small-Specimen Tests
Authors: Marschall CW , Papaspyropoulos V , Landow MP
Published: February 2009

A combined experimental and analytical study was conducted to assess the ability of J-resistance curves obtained from small fracture toughness specimens to predict large amounts of crack growth in highly ductile nuclear piping materials. Tests were conducted at 288C (550F) on 25.4-mm (1-in.)-thick compact tension specimens of 1T, 3T, and 10T planar dimensions. The materials investigated included Type 304 austenitic stainless steel and ASTM A516, Grade 70 carbon steel. Resistance curves were developed from the data using both deformation J, JD, and modified J, JM, estimation schemes. Some of the tests on austenitic stainless steel also were analyzed by performing elastic-plastic finite-element calculations, and the results were used to evaluate extrapolation procedures.

Extrapolation of small-specimen JD resistance curves to large amounts of crack growth resulted in sizable underestimations of resistance to fracture for the ductile materials studied. The JM-resistance curves, on the other hand, showed much less specimen-size dependence but tended to overestimate fracture resistance when small-specimen data were extrapolated. A tentative empirical method for extrapolating small-specimen data was developed. It was found also that the finite-element far-field J-R curves were very similar to the JM-R curves, and that the far-field finite-element J-R curve for the 10T specimen was virtually an extension of the J-R curves calculated for the 1T and 3T specimens.
Further Developments on the Modified J-Integral
Authors: Ernst HA
Published: February 2009

This paper shows new developments on the modified J-integral, JM. General formulas are presented, and a physical interpretation is given in terms of energy differences. Also defined are the apparent stored energy, A, and a generalized pseudo crack driving force, Q. A general approach is presented so that for each particular material law used, the corresponding crack drive parameter is obtained.
A Closer Look at Tearing Instability and Arrest
Authors: Joyce JA
Published: February 2009

The objective of this work was to take an in-depth look at the process of ductile tearing instability and, especially, to evaluate experimentally the conditions for arrest of a ductile tearing instability. A secondary objective was to evaluate the sensitivity of a ductile tearing instability arrest to the rate at which it occurred and to the material rate sensitivity. Major conclusions are that the ductile tearing instability initiates slowly, but in a mechanical spring apparatus, it approaches drop-tower crack growth rate conditions, and hence the phenomenon is affected by the material rate sensitivity. The conditions necessary for arrest are completely stated and demonstrated by experimental data on a 3% nickel structural steel.
Elastic-Plastic Assessment of a Cladded Pressurized-Water-Reactor Vessel Strength Since Occurrence of a Postulated Underclad Crack During Manufacturing
Authors: Devaux J-C , Saillard P , Pellissier-Tanon A
Published: February 2009

The local approach to fracture is applied to analysis of the influence of fabrication and operation history on the safety margins for fracture of a pressurized water reactor vessel with an underclad reheat crack in the belt line, subjected to a severe pressurized thermal shock (PTS) transient at end-of-life. The elastoplastic analysis begins with numerical simulation of the manufacturing of the belt-line cladding, then continues with the creation of the crack during stress relief heat treatment, proof testing, loading-to-operating conditions, and, finally, occurrence of the pressurized thermal shock. Computation of the behavior of laboratory specimens at the temperature occurring at the crack tips at maximum load during the PTS transient makes it possible to translate the results obtained in terms of cleavage or tearing damage values, respectively, into the scales of the conventional KI and J toughness parameters. This analysis, which accounts for all effects of the vessel fabrication, and the operation history, discloses much larger safety margins than the conventional analysis presently used for vessel integrity assessments.
An Analytical and Experimental Comparison of Rectangular and Square Crack-Tip Opening Displacement Fracture Specimens of an A36 Steel
Authors: Sorem WA , Dodds RH , Rolfe ST
Published: February 2009

Analytical and experimental investigations of both rectangular-cross-section (t by 2t) and square-cross-section (t by t) three-point-bend crack-tip opening displacement (CTOD) fracture specimens were conducted on an A36 steel. This study is part of a long-range investigation aimed at developing criteria to evaluate the susceptibility to fracture in specific structural situations, that is, pressure vessels and structural steels with short cracks (a/W 0.15), where the square CTOD specimen must be used. Generally, the rectangular CTOD specimen is used in laboratory testing, but for weldment testing, where shallow surface cracks may exist, or for other structural applications with crack depth ratios other than a/W = 0.5, the square specimen is often required. The objective of this study is to compare the CTOD fracture toughness results of square specimens with those of rectangular specimens using equivalent crack depth ratios (a/W = 0.5).

Both analytical and experimental studies were conducted on full-size [31.8 by 31.8-mm (1.25 by 1.25-in.)] and sub-size [12.7 by 12.7-mm (0.50 by 0.50-in.)] square specimens. Static CTOD tests were conducted in the lower shelf and lower transition regions where structural steels such as A36 are typically used. Three-dimensional elastic-plastic finite-element analyses were conducted to compare the effect of specimen size and geometry on the specimen stress field.

The results of the square specimens were compared with the results of previously tested rectangular specimens that were tested and analyzed by Wellman et al. following the same procedures. In comparing these four specimen sizes, it was shown that the lower-bound CTOD values obtained experimentally were independent of either specimen size or geometry in the lower shelf and lower transition regions prior to stable crack growth. The near-crack-tip opening mode stresses at the center plane of each specimen were shown to be essentially equal for the four specimen sizes analyzed. This implies that the square and rectangular specimens with a/W = 0.5 may be used interchangeably to characterize the notch toughness prior to stable crack growth. It may also be possible to obtain the same lower-bound results using sub-size specimens which are less than the full thickness of the actual structure.
Effect of Fracture Micromechanisms on Crack Growth Resistance Curves of Irradiated Zirconium/2.5 Weight Percent Niobium Alloy
Authors: Chow CK , Simpson LA
Published: February 2009

J-integral resistance curves, determined from curved compact specimens of irradiated Zr-2.5Nb, show an unusual three-stage behavior. Immediately after initiation of stable crack extension, the crack growth resistance increases at a low rate, followed by a second stage in which the J-resistance (JR) curve rises relatively steeply. Finally, the J-resistance curve decreases its slope, eventually reaching an approximately constant (zero slope) value. To explain this behavior, a series of compact specimens were pulled to various stages of crack extension and carefully examined using metallographic techniques and scanning electron fractography. The authors conclude that the decrease in crack growth resistance due to irradiation is a consequence of shear localization behavior, and the three-stage JR curve is attributed to an abrupt transition from plane-strain conditions to the development of very flat shear lips. This peculiar shear-lip formation is shown to be a consequence of strain localization behavior.
A Combined Statistical and Constraint Model for the Ductile-Brittle Transition Region
Authors: Anderson TL
Published: February 2009

A model is presented which uses weakest link statistics to predict the fracture toughness of ferritic steels in the ductile-brittle transition region. This model is different from previous analyses in that it considers large-scale yielding and specimen geometry effects.

The model is used to predict median crack-tip opening displacement (CTOD) transition curves for American Bureau of Shipping (ABS) EH36 steel. The shape of the predicted curves agreed very well with the experimental data, but the absolute position of predicted and experimental curves differed by as much as 20C. The model was also used to predict CTOD distributions at constant temperatures, although direct comparison with experimental data was not possible. Analysis of the predicted toughness distributions indicated that a three-parameter Weibull fit of fracture toughness data may result in a nonconservative estimate of lower-bound toughness. An alternative procedure for estimating lower-bound toughness is described, together with a method for determining an upper-bound transition temperature.
State-of-the-Art Paper: Some Recent Developments in Triaxial Testing Systems for Cohesionless Soils
Authors: Tatsuoka F
Published: February 2009

The stress states and their changes that can be attained in the conventional triaxial testing method are reviewed and compared to those attained in other more sophisticated testing methods. These advanced tests have been developed to extend the ranges of the stress states and the changes in these states that can be controlled. In conventional triaxial testing on solid cylinder specimens σ2′ is equal either to σ1′ or to σ3′ and only a jump rotation of 90° in the principal stress directions can be achieved. It is argued that in spite of this limitation the triaxial testing method is still a useful means to measure the strength and deformation characteristics of soils. The results, however, should be corrected to account for the actual states of stress in the field. Furthermore, some recent advances in the methods and equipment for triaxial testing and other related kinds of testing are reviewed with an emphasis on the importance of automation and simplification. Several examples are presented where automated controlled stress and/or strain path tests can be performed by means of a simple triaxial apparatus using various electronic transducers, microcomputers, and pneumatic pressurizing systems.
A 300-mm-Diameter Triaxial Cell with a Double Measuring Device
Authors: Dupas J-M , Pecker A , Bozetto P , Fry J-J
Published: February 2009

A large-diameter triaxial cell (φ 300 mm) is presented. Its uniqueness lies in the double measuring system of all parameters: axial strain, volumetric strain, and pore pressures. Owing to this system, accurate measurements can be taken, enabling the determination of the soil constitutive relationships from very small strains (elastic behavior) to failure strains. The cell can be used either under quasistatic monotonic or cyclic dynamic loadings. The apparatus has been used to evaluate the accuracy of the measurements and the influence of sample size on elastic Young's modulus, Poisson's ratio, and variation of secant modulus with strain.

Preliminary results show that, as opposed to conventional testing, significantly improved results are obtained with the double measuring system.
Triaxial Testing of Intact Salt Rocks: Pressure Control, Pressure Systems, Cell and Frame Design
Authors: Baleshta JR , Dusseault MB
Published: February 2009

An extensive laboratory for intact salt rock behavior research (the WATSALT Laboratory) was conceived at the University of Waterloo in 1982, and by 1984 researchers here were producing results of high quality. At present, six high capacity test stations for creep behavior are operating on a continuous basis. The designs were developed to meet the requirements of constant pressure, environmentally stable creep testing. Self-regulating pressure control systems have been designed, and they are performing effectively. The WATSALT systems can test a range of specimen sizes to 100 mm in diameter, at stresses of 200 MPa axial, and 70 MPa lateral. Creep test durations have extended to 6 months on an individual specimen. The automated control systems keep temperatures constant to 0.1°C and pressure fluctuations to within 0.1%. This paper describes the approach to design, the triaxial cell and axial load frame configuration, an alternate internal axial piston cell, temperature and pressure control systems, instrumentation, and data acquisition.
Triaxial Testing of Granular Soil Under Elevated Cell Pressure
Authors: Colliat-Dangus JL , Desrues J , Foray P
Published: February 2009

A study of triaxial testing under elevated cell pressure is presented. The influence of test conditions, namely end lubrication and slenderness ratio, on such tests is discussed. Results of a tomodensitometric investigation of internal homogeneity are given. The main results of the high pressure study are presented, including time effects on isotropic compression.
Application of Multistage Triaxial Test to Kuwaiti Soils
Authors: Saeedy HS , Mollah MA
Published: February 2009

Forty-eight soil samples taken from twelve different locations in Kuwait City and the Jahra area were used in four series of drained and undrained triaxial compression tests using multistage and conventional test techniques on undisturbed and remolded specimens. Classification tests indicated that the Kuwaiti soil is predominantly sandy with various content of fines. The fines content includes silt and clay, and also clay-size particles of calcareous and gypsiferous matter. Strength test results indicated that the cohesion and angle of friction determined from both techniques are in agreement and hence the multistage principle can be applied to determine the shear strength parameters of Kuwaiti soils. Specific recommendations on applying the multistage technique on cemented soils, occasionally encountered in Kuwait, are also included.
Special Stress Paths Along the Limit Surface of a Sand Specimen with the Use of a True Triaxial Apparatus
Authors: Lanier J
Published: February 2009

This paper presents a true triaxial apparatus with rigid platens and its means of measurement and regulation. For tests performed on dry sand specimens, the loss of homogeneity by localization of deformation along shear bands is first analyzed. Then special circular paths in deviatoric stress plane are obtained. If the radius of this path is large enough, the author shows that the actual stress point moves on the limit surface which is well approximated experimentally. The more surprising result is that the volume of the specimen, on such cyclic paths, decreases. This result outlines the danger of liquefaction even for dense sand under complex stress path.
Standardized Terminology—The Use of Notes in a Common Language for Writers and Readers
Authors: Freund RA
Published: February 2009

Technical committees must consider the relationship of the terminology they define to the understanding by the general public of these same terms. Some definitions originate within the technical community and move outward to enter the general domain without any serious difficulty. For others, special care is required to avoid conflict with existing interpretations or to make internal revisions because of changes over time in common or legal usage. As examples, national and international standard definitions of the words “quality,” “grade,” “nonconformity,” and “defect” are presented with particular reference to the effectiveness of the use of notes integrated with single-sentence definitions. The need for a uniform set of definitions within ASTM is also discussed with reference to a project dealing with statistical terms.
Effect of Removing Eccentricity from Button Tensile Adhesion Tests
Authors: Anderson GP , Chandapeta S , DeVries KL
Published: February 2009

Adhesive testing is done for several reasons, including quality control, strength comparisons, and obtaining adhesive joint design data. However, the reported bond strengths often vary so much that interpretations are not clear. One reason for this variation is examined in this study. Since stress distribution and debond load are very sensitive to alignment of the test specimen, test grips have been designed to alleviate the alignment sensitivity in tensile adhesion tests. A large decrease in data variation was observed when modified test grips were used with epoxy tensile adhesion specimens.