bluuebunny/crossref_metadata_2025_split huggingface dataset:
Effect of Material Stress Sensitivity on Backcalculated Moduli and Pavement Evaluation
Authors: Stubstad RN , Mahoney JP , Coetzee NF 
Published: March 2009

The Falling Weight Deflectometer (FWD) has become a popular device for evaluating both airfield and highway pavements. Typically, deflection tests with the FWD or HWD (Heavy Weight Deflectometer) are performed at predetermined load levels up to approximately 120 kN (27,000 Ibf) for the FWD and 240 kN (54,000 Ibf) for the HWD. This paper addresses the choice of load level for pavements exhibiting stress-sensitive behavior and the effect both on backcalculated moduli and the resulting rehabilitation designs for a number of pavement evaluation projects performed over the last few years.
It is well known that many unbound materials used in pavements exhibit non-linear behavior in laboratory tests, as discussed in the paper. The effect of such non-linear response in pavement structures suggests that deflection testing should be performed using load levels at or near the expected design loads, or in a manner which allows reasonable determination of material parameters defining the non-linear behavior.
Several pavement studies have been selected that exhibit non-linear response using various HWD test load levels, from approximately 60 kN (13,000 Ibf) to the full 240 kN (54,000 Ibf), with all tests on a given project performed on the same series of test points, at the same time. Results of backcalculation and evaluation analyses for these pavements are presented in the paper.
Analysis of deflection basins measured at the different load levels show significantly different backcalculated moduli which appear to be consistent with the stress-stiffening or stress-softening behavior exhibited by similar materials in laboratory tests. As a result, evaluation of structural capacity for a given (expected) traffic loading is significantly affected by these moduli values, and required overlay thicknesses may vary by a factor of two or more for different deflection test load levels, at a given pavement section. The analyses presented in the paper clearly illustrate the necessity for adequately defining actual material response in evaluating the pavement system response. Asphalt surfaced pavements tend to be more prone to these non-linear response characteristics, due to the significant structural contribution of the unbound layers often found in these pavements.
Phase LAG Effects on Analysis of FWD Data
Authors: Sebaaly PE , Holikatti S 
Published: March 2009

The research documented in this paper examines the effect the phase lag has on the analysis of FWD data. The research examined the use of a deflection basin generated from the peak sensors' deflections, a deflection basin generated from instantaneous deflections based on peak load, and a deflection basin generated from instantaneous deflections based on the peak deflection at sensor #1. The influence of the various analyses is evaluated by comparing the material properties produced by each individual analysis and their relative impact on the recommended overlay thickness.
The analysis of the data indicated that almost all of FWD field data have instantaneous deflection basins which greatly differ from the deflection basin generated by the peak response. The backcalculation data indicated that the type of analysis may have a significant effect on the magnitudes of the moduli of the layers. Finally, the overlay analysis showed that there are significant differences among the recommended overlay thicknesses based on the different analyses. The differences were as high as 1.5 inches in some cases.
Effects of Pavement-Falling Weight Deflectometer Interaction on Measured Pavement Response
Authors: Boddapati KM , Nazarian S 
Published: March 2009

In any linear elastic program used in backcalculation, a uniform pressure distribution is assumed for the applied load. As such, the loading system of any FWD should be designed so that the load transferred to the pavement is uniform. However, the pressure distribution is also affected by the pavement profile being impacted on.
A finite element study has been carried out to determine the cases where the imparted load would or would not yield a uniform pressure distribution and to assess its significance on the measured and backcalculated parameters. The FWD-pavement interaction has little significance when rigid pavements are tested. For flexible pavements, the deflections from the first sensor may be affected by this interaction. The softer the pavement system, the more significant this interaction will be.
The Impact of Particle Size on TCLP Extraction of Cement-Stabilized Metallic Wastes
Authors: Prange NE , Garvey WF 
Published: March 2009

EPA has introduced the Toxicity Characteristic Leaching Procedure (TCLP) in rulemakings associated with the Hazardous and Solid Waste Amendments of 1984. Limited ruggedness testing has evaluated the method's sensitivity to some test variables but has not addressed the effect of waste particle size. The TCLP method specifies a maximum particle size (9.5 mm sieve opening) and sets no lower limit.
To evaluate the effect of particle size, the authors tested an arsenic waste and a chromium waste, each stabilized with Portland cement. Five discrete particle size fractions ranging from 9.5 mm down to 0.5 mm were extracted by the TCLP procedure. For both wastes, it was found that the metals leached more readily from the larger particle fractions. Furthermore, the pH of the extraction fluid during the first 2 hours of the extraction stayed acidic for the large particles while for the smaller particles, the pH quickly became basic. Final extract pH was lower for the larger particles than for the smaller particles.
The results of this work indicate that particle size has a strong influence on TCLP extraction results for the tested wastes. This suggests that the particle size variable needs tighter controls than presently specified in the TCLP method to ensure reproducible results for at least some wastes.
Preparation of Natural Matrix Type Samples for Performance Evaluation of Resource Conservation and Recovery Act (RCRA) Contract Laboratories
Authors: Clements HA , Loebker RE , Klosterman DL 
Published: March 2009

The Quality Assurance (QA) Branch develops, analyzes, and distributes natural matrix samples to evaluate the performance of laboratories conducting analyses for the Office of Solid Waste (OSW). In these studies each laboratory is requested to analyze an organic sample and an inorganic sample using the analytical methods specified by OSW.
The sample designs and reference values are established by multiple analyses in the QA Branch laboratory and contract referee laboratories. These data are evaluated statistically and must be judged acceptable before samples are distributed to the 50–60 RCRA contract laboratories. These data are also furnished to OSW for use in evaluating the results reported by the contract laboratories.
An Analytical Comparison of Short Crack and Deep Crack CTOD Fracture Specimens of an A36 Steel
Authors: Sorem WA , Dodds RH , Rolfe ST 
Published: March 2009

The effect of crack-depth to specimen-width ratio on crack tip opening displacement (CTOD) fracture toughness is an important consideration in relating the results of laboratory tests to the behavior of actual structures. Deeply cracked three-point bend specimens with crack-depth to specimen-width ratios (a/W) of 0.50 are most often used in laboratory tests. However, to evaluate specific weld microstructures or the behavior of structures with shallow surface cracks, specimens with a/W ratios much less than 0.50 often are required. Laboratory tests reveal that three-point bend specimens with short cracks (a/W = 0.15) exhibit significantly larger critical CTOD values than specimens with deep cracks (a/W = 0.5) up to the point of ductile initiation.
In this study, finite element analyses are employed to compare the elastic-plastic behavior of square (cross-section) three-point bend specimens with crack-depth to specimen-width ratios (a/W) ranging between 0.50 and 0.05. The two-dimensional analysis of the specimen with an a/W ratio of 0.15 reveals a fundamental change in the deformation pattern from the deep crack deformation pattern. The plastic zone extends to the free surface behind the crack concurrent with the development of a plastic hinge. For shorter cracks (a/W= 0.10 and 0.05), the plastic zone extends to the free surface behind the crack prior to the development of a plastic hinge. For longer cracks (a/W &gt; 0.20), a plastic hinge develops before the plastic zone extends to the free surface behind the crack.
These results prompted further study of specimens with an a/Wratio of 0.15 using three-dimensional, elastic-plastic finite element analyses. Results of the short crack (a/W = 0.15) analysis are compared to the results of the deep crack (a/W = 0.50) analysis reported previously by the authors. In the linear-elastic regime (characterized by small-scale plastic deformation) the relationship of stress ahead of the crack tip to CTOD is identical for the short crack and the deep crack specimens. At identical CTOD levels in the elastic-plastic regime (large-scale plasticity, hinge formation), the crack tip stress is significantly lower for specimens with a/W = 0.15 than for specimens with a/W = 0.50. Correspondingly, at equivalent stress levels, the CTOD for the short crack is approximately 2.5 times the CTOD for the deep crack. This observation has considerable significance in the application of CTOD results to failure analysis or specification development where the fracture mechanism is cleavage preceded by significant crack tip plasticity.
Application of J-Integral and Modified J-Integral to Cases of Large Crack Extension
Authors: Joyce JA , Davis DA , Hackett EM , Hays RA 
Published: March 2009

The J-integral is widely accepted as a measure of elastic-plastic fracture toughness of engineering alloys. Specimen size and geometry dependence were first noted in fracture toughness measurements using the ASTM E 813 calculation of the deformation J-integral (Jd) by McCabe and Landes [1] in 1983. The modified J-integral (Jm) was introduced by Ernst [2] to attempt to minimize or eliminate size and geometry dependence. Since Jm was introduced, questions have arisen regarding the proper parameter to describe the response of a flawed body to loading. The objective of this research task is to investigate the crack growth and specimen J capacity limitations of Jd and to verify the accuracy and specimen independence of the current Jm formulation. This research is expected to affect decisions concerning the use of small laboratory specimens to predict elastic-plastic crack growth resistance in engineering structures.
The J-R curve tests have been conducted on ½T, 1T, and 2T compact specimens of materials having critical fracture toughness values ranging from JIc = 140 to 455 kJ/m2. These materials include HSLA-80 steel, A106 steel, 3-Ni steel, and two A533B steels. These tests were conducted in accordance with ASTM E 1152 except that specimen loading was continued until large crack extensions were present, in many cases exceeding 50% of the initial uncracked ligament (b). All specimen data were then analyzed using the equations of ASTM E 1152 for the standard deformation J-integral (Jd) resistance curve. Additional analysis was conducted as well in terms of the modified J-integral (Jm) using equations proposed by Ernst and Landes [3]. This latter quantity was possibly useful to larger crack extensions. The test procedure was directed towards finding the useful limits of the two J quantities for the materials listed above or for materials of equivalent strength and toughness.
Adhesive Fracture Testing
Authors: Mecklenburg MF , Arah CO , McNamara D , Hand H , Joyce JA 
Published: March 2009

The need for lightweight materials for a variety of applications has resulted in the use of structural adhesives to bond prototype structures. Adhesives developed to accommodate the stringent requirements of these high-technology applications are usually deficient in one or two of three very crucial properties: strength, moisture resistance, and toughness. So far, advances in adhesive formulation that have ameliorated one of these deficiencies have generally adversely affected the others. Hence a considerable amount of effort is being expended in the search for strong, moisture resistant, and tough adhesives.
As adhesives become tougher and less brittle, evaluating their performance in terms of fracture parameters becomes more complicated. Linear elastic fracture mechanics (LEFM), which is widely used to characterize these materials, does not fully describe adhesive performance as more and more ductility or plastic deformation is introduced. In the study reported here, we introduce the energy separation method for characterizing the fracture resistance of adhesives and compare it with currently used elastic and plastic fracture parameters such as G and the J integral. Both neat and bonded ½ CT plan specimens were tested and compared in this work.
Effect of Dynamic Strain Aging on Fracture Resistance of Carbon Steels Operating at Light-Water Reactor Temperatures
Authors: Marschall CW , Landow MP , Wilkowski GM 
Published: March 2009

This paper reviews the phenomenon of dynamic strain aging in carbon steels and considers its effects on the fracture behavior of carbon-steel pipes and pressure vessels in lightwater reactors operating at elevated temperatures near 290°C (550°F).
Dynamic strain aging is a phenomenon in which aging occurs simultaneously with plastic straining. It occurs over a range of temperatures that depends on strain rate. In tensile tests, it is manifested by increased tensile strength, increased strain-hardening rate, serrated stress-strain curves, and decreased ductility.
Evidence is presented to show that the occurrence of dynamic strain aging can significantly lower the fracture resistance of carbon steels. This lowering of fracture resistance may be manifested in several ways: (1) JIc is lower at light-water reactor (LWR) temperatures than at room temperature, (2) the tearing modulus is lower at LWR temperatures than at room temperature, and (3) stable ductile crack growth may be interrupted by unstable ductile fracture at LWR temperatures but not at room temperature.
The paper examines probable causes of dynamic strain aging and describes methods for identifying which steels are susceptible to it.
Microstructure and Fracture Toughness of Cast and Forged Ultra-High-Strength, Low-Alloy (UHSLA) Steels
Authors: Zeman J , Rolc S , Buchar J , Pokluda J 
Published: March 2009

This paper describes the fracture toughness and microstructure relations for ultra-high-strength, low-alloy (UHSLA) steels corresponding to AISI 4340 composition. The steels were either cast or forged, heat treated at austenitizing temperatures from 840 to 1100°C, oil quenched and tempered at 180 and 650°C. Fracture toughness, tensile, and Charpy impact toughness tests, and testing of apparent fracture toughness under the influence of notch root radius, were performed simultaneously. Investigation of microstructures and corresponding mechanical properties, as well as fractographic examinations and evaluation of chemical heterogeneity, made it possible to elucidate the alteration of fracture behavior.
It was found that cast low-tempered steel has higher fracture toughness (KIc) than forged steels, though its conventional mechanical properties are lower. Increasing KIc caused by the higher austenitizing temperature of forged steel was also observed. The coarsened prior austenite grains and decreased grain boundary cohesive strength are mainly responsible for the intergranular crack initiation and the related modification of the crack path, the consequence of which may be a change in the effective stress intensity factor.
The proposed model, based on assumed average probable crack path angle deflection controlled by the grain boundary, has yielded satisfactory agreement with experimental results. The mechanical properties of the more heterogeneous cast steel can be elucidated in the same sense. It has been concluded that there exists some uncertainty in the determination of “valid” plane strain fracture toughness, particularly in the case of ultra-high-strength steels, along with their more pronounced macro/microstructure heterogeneity. Due to this effect, the recommended procedure of KIc measurement can provide undesirable overestimation of the material quality being tested.
A Review of Polymer Test Methods Applicable to Geosynthetics for Waste Containment
Authors: Mores M , Cassidy PE , Kerwick DJ , Koeck DC 
Published: March 2009

The study of the environmental degradation of geosynthetic materials used in hazardous waste facilities has generated much interest in recent years. Analytical methods are used to supplement conventional structure changes and mechanisms of failure associated with the polymer. Any changes in the base polymer caused by chemical exposure may result in severe changes in strength, durability and serviceability of the geosynthetic. Chemical and physical analytical methods are used in evaluation of chemical compatibility and long-term durability of geosynthetics for several purposes: 1) to verify that geosynthetics tested in advance of landfill construction are essentially the same as those procured for the actual installation, 2) to identify and monitor changes in molecular structure caused by chemical attack, and 3) to provide accelerated assessment of the effects of long-term aging, an especially difficult and as yet, not thoroughly researched topic. These factors can be reviewed by studying the oxidation and solvation properties as well as the change in crystalline structure of the plastics.
This paper discusses “fingerprinting” methods used to characterize geosynthetics. These methods fall into four major categories of analytical techniques: thermal analysis, spectroscopy, chromatography and microscopy. The advantages of these analytical techniques are their precision, accuracy, and small sample size requirements. The methods discussed in this paper can detect small changes in molecular structure that often are not observed with traditional bulk properties testing after short aging times.
Pyramid Puncture Test for Evaluating the Protection Function of Geotextiles
Authors: Pühringer G 
Published: March 2009

At present, there are inadequate recommendations to guide the design engineer in the selection of protection geotextiles in association with geomembranes. Current recommendations generally rely on elaborate field experiments or costly laboratory studies. A relieable engineering assessment method that will yield useful puncture values is not currently available. With the pyramid puncture test, however, testing is possible on geomembranes and protective nonwoven geotextiles to determine the magnitude of the protection provided by geotextiles.
The test apparatus consists mainly of a pyramid piston, an underlaying media and a test press. The test specimens can be tested unclamped or clamped between rings. An electric circuit is applied between the piston and the underlying media to indicate the puncture force at the point of perforation.
Multispecies Methods of Testing for Toxicity: Use of the Rhizobium-Legume Symbiosis in Nitrogen Fixation and Correlations Between Responses by Algae and Terrestrial Plants
Authors: Garten CT 
Published: March 2009

Responses of the Rhizobium-legume symbiotic relationship to long-term (5- to 7-week) and short-term (2-week) exposures of copper sulfate, 2,4-dichlorophenoxyacetic acid, and streptomycin sulfate were examined in bush beans and clover. Toxic effects were evaluated by comparing plant biomass (yield), nodulation success, nitrogen fixation rate as indicated by acetylene reduction, and plant nitrogen content in controls and in plants exposed to various concentrations of the chemicals. Plants with long-term continuous root exposure were affected more than plants with short-term exposure, as indicated by reductions in nitrogen fixation rates and plant growth. Although rates of acetylene reduction (nitrogen fixation) were depressed, plant biomass and the numbers of root nodules produced were simpler, less expensive indices of exposure.
In a second test, the responses of algae (Selenastrum capricornutum and Chlorella vulgaris) and terrestrial plants (radishes, barley, bush beans, and soybeans) to 21 different herbicides were compared to evaluate the use of a short-term (96-h) algal growth inhibition test for identifying chemicals potentially toxic to terrestrial plants. Two test end points were evaluated: (1) the highest concentration resulting in no statistically significant reduction in the growth rate of algae or terrestrial plants, and (2) the concentration at which algal growth or terrestrial plant biomass was reduced by 50%. Test results were correlated for the two algae and for all pairs of vascular plants. However, results of the algal tests did not correlate with those of the terrestrial plants. Furthermore, according to tests with Selenastrum capricornutum, there was only a 50% chance of successfully identifying herbicide levels that reduced terrestrial plant biomass. For the herbicides and species examined, short-term toxicity tests with algae were not good indicators of toxicity to terrestrial plants.
Ecological Effects Evaluation of Two Phosphorus Smoke-Producing Compounds Using Terrestrial Microcosms
Authors: Tolle DA , Arthur MF , Duke KM , Chesson J 
Published: March 2009

An intact soil-core microcosm and static exposure system were used to evaluate the potential ecological effects of two obscurant smokes, red phosphorus/butyl rubber (RP/BR) and white phosphorus/felt (WP/F), used in the field during U.S. Army training exercises. The terrestrial microcosm technique differed from the test protocol prepared for the U.S. Environmental Protection Agency by using a preliminary plant stress-ethylene test to help select the dose range for microcosm testing, and by combining aspects of traditional range-finding and definitive tests into a single microcosm test.
Three plant species (white sweetclover, perennial ryegrass, and wheat) were used for both preliminary and microcosm tests. The stress-ethylene tests indicated that extremely high doses of either smoke would be required to elicit a response in the microcosm test. This information guided selection of microcosm test concentrations. Microcosms were exposed to either RP/BR or WP smoke at target concentrations of 0, 100, 300, 600, and 1500 mg/m3. These concentrations bracket typical field concentrations.
Minor ecosystem-level effects were detected in microcosms only at the highest smoke concentration and included increased nutrient (Ca) loss in leachate, increased (wheat) or decreased (sweetclover) biomass yield, and increased element (Al, As, Pb, and P) uptake in plant tissue. No negative ecological effects of either smoke were detected at smoke concentrations equal to or below 600 mg/m3, even for 16 semiweekly exposures over an 8-week period.
It was concluded that: (1) deployment of these two smokes at typical field concentrations is unlikely to cause significant problems to most terrestrial systems; (2) the terrestrial microcosm system appears to be appropriate for evaluating the static, long-term, particle-deposition effects of other aerosols; and (3) the test design produces input for hazard assessment at considerable savings in cost and time compared to the more traditional range-finding plus definitive test strategy.