bluuebunny/crossref_metadata_2025 huggingface dataset:
An Examination of the Influence of Residual Stresses on the Fatigue and Fracture of Railroad Rail
Authors: Rice RC , Leis BN , Tuttle ME
Published: March 2009

Fatigue cracks in rails can be the source of failures and subsequent derailments. The present paper examines the effect of residual stresses on the fatigue and fracture resistance of rail steel materials and the probable influence of residual stresses on the fatigue performance of rails in service. The magnitudes of residual stresses in rails were measured as a part of this study. Tensile and compressive residual (mean) stresses are shown to have a significant effect on the fatigue resistance of rail steels through tests using cylindrical smooth and compact tension specimens (free of inherent residuals) over a range of mean stress conditions. Fatigue and fatigue crack growth rate data developed are analyzed using specific damage parameters to consolidate the effect of mean stress. These data are then used in combination with measured residual stresses on rails to estimate the influence of service/fabrication induced, residual stresses in actual rail.
Effect of Surface Residual Stresses on the Fretting Fatigue of a 4130 Steel
Authors: Kudva SM , Duquette DJ
Published: March 2009

Fretting fatigue is defined as the fatigue of a material caused by the presence of a rubbing contact with a relative displacement of less than 100 micrometres. The presence of fretting results in a lowering of the fatigue life of the material. The relative displacement, also known as the slip amplitude, has a considerable effect on the life of the specimens that were investigated. Different surface microstructures were studied in order to investigate the effect of slip amplitude on the fatigue life. These treatments, namely carburization and decarburization, also induced surface residual stresses which were instrumental in causing the changes that were observed in the fatigue life.

Effects of residual stress on fretting fatigue were studied using three kinds of heat-treated specimens of a medium carbon steel. Two sets of experimental specimens were respectively decarburized and carburized to induce residual stresses on the surface. A set of control specimens of tempered martensite was used to compare results. All three structures showed a minimum in life versus the slip amplitude; the carburized specimens exhibited longer lives in general and the opposite was true for the decarburized specimens. In all cases, transverse cracks initiated on the surface, at the interface between the contacting and free surfaces, and propagated inwards, perpendicular to the loading axis. An attempt is made to explain the observed phenomena using residual stress arguments.
Volume Change Due to Freezing in Plastic Masonry Mortar
Authors: Davison JI
Published: March 2009

Scandinavian researchers have identified reduction of moisture content to 6 percent and sufficient prehardening as conditions under which mortar in masonry walls will withstand early freezing without damage. This paper reports the results of a study in which volume changes due to freezing were measured in mortars to assess these conclusions for Canadian masonry materials. Volume changes in mortar samples encased in a rubber balloon immersed in alcohol in a cylinder connected to a calibrated capillary were measured as the temperature was lowered through the freezing zone. The effect of variable moisture contents and setting times for a 1:1:6 cement-lime mortar and a 1:3 masonry-cement mortar were studied. It was found that freezing expansions of the order of 2 percent for cement-lime mortar control samples dropped sharply after a setting time of 4 h and virtually disappeared at 16 h. Expansions of 1.25 percent in masonry-cement control mortars decreased to negligible values after a setting time of 4 h. Reductions to 6 percent moisture content reduced freezing expansions to negligible values for both mortars, although problems were encountered in bringing moisture contents down to 6 percent. The possible application of the results to field conditions is discussed.
Water Permeance of Masonry Walls: A Review of the Literature
Authors: Grimm CT
Published: March 2009

Literature on permeance of brick and concrete masonry walls to wind-driven rain is reviewed. The force and quantity of rain on walls is discussed. The mode of water entry into the face of masonry through various kinds of cracks is reviewed. Wall design in several aspects is considered. Workmanshi and materials selection are discussed. Flashing, sealants, and metals in walls are reviewed. Repair procedures are outlined. Recommendations are made for materials, design, construction, and maintenance of masonry to reduce water permeance of walls above grade. More than 60 references are cited and a bibliography lists 233 entries under nine key words.
State of the Art: State Acceptance of Bituminous Concrete Production and Construction Using Quality Assurance Specifications
Authors: Hughes CS
Published: March 2009

This paper reports on the state of the art, from the standpoint of state agencies, of the use of statistical quality assurance procedures for the acceptance of bituminous concrete production and construction. Information on the procedures being used by the 50 state highway agencies, as of the spring of 1978, was obtained through a questionnaire and is reported. The paper deals with two areas involving bituminous concrete: (1) production, which primarily encompasses determining the asphalt content and gradation of the aggregate; and (2) construction, which comprises the roughness, thickness, and density of the pavement. The responses to the questionnaires showed that 25 agencies have a statistical quality assurance specification for accepting production, although three of these agencies stated that the program was still experimental. For construction, 25 states, coincidently, also reported employing a statistical quality assurance program. Most of these have a specification dealing with density. The estimated annual dollar savings were reported to be from $100 000 to $1 000 000. For those agencies not now using quality assurance specifications, the specifications of most interest were those for production and for the density and roughness of the pavement. Eleven agencies indicated that they are not now using nor are they contemplating the use of statistical quality assurance specifications.
Influence of Microstructure on Elevated-Temperature Fatigue Resistance of a Titanium Alloy
Authors: Hoffmann C , Eylon D , McEvily AJ
Published: March 2009

The strain-controlled, elevated-temperature, low-cycle fatigue behavior of a near α titanium alloy, Ti-6Al-2Sn-4Zr-2Mo-0.1Si (Ti-6242S), has been studied in both air and vacuum (10−5 torr) at 525°C over a range of frequency and strain. Of particular interest in this investigation were the influence of microstructure and environment on fatigue behavior. Two different microstructures were obtained by combinations of mechanical processing and heat treatment above and below the β-transus temperature. Particular attention was given to these microstructural variations and to the effect of environment on the high-temperature low-cycle fatigue behavior of this alloy. The nature of fatigue crack initiation sites was examined by a precision sectioning method. The microstructure was found to have a pronounced effect on fatigue life as well as on the fatigue crack initiation process. Tests performed in vacuum revealed no influence of frequency on fatigue life, which indicated that environmental factors were responsible for the observed frequency effect on tests performed in air. It was also observed that testing in vacuum led to the formation of a number of subsurface crack nucleation sites and to a longer fatigue life. Crack origins in specimens tested in air were located at the surface, and the initiation sites were larger than those observed in vacuum. The features of a fatigue resistant microstructure in addition to environmental effects at elevated temperature are identified and discussed.
Creep and Cyclic Tension Behavior of a Type 316 Stainless Steel at Room Temperature
Authors: Nomine AM , Dubois D , Miannay D , Balladon P , Heritier J
Published: March 2009

The behavior of a Type 316 L austenitic stainless steel subject to creep and cyclic tension under imposed load is examined at room temperature. Tests are carried out on the material in both the annealed and work-hardened state; in the latter case the influence of an initial hardening by cyclic tension on the subsequent creep behavior, together with the influence of creep hardening on the subsequent cyclic tension behavior, are determined. All tests are conducted with stresses from half the 0.2 percent yield stress up to a stress leading to an initial plastic strain of about 10 percent.

We demonstrate the existence of a (critical) stress limit for creep and a stress limit for (cyclic) accommodation. The creep strain, for a given time interval, increases with the applied stress and, in general, the material continues to creep after 10 000 h. The plastic elongation, between the 1st and the 1000th cycle, that occurs during cyclic tension tests on the annealed materials goes through a maximum when plotted as a function of the maximum applied stress. The creep strain obtained after prior cyclic tension (1000 cycles at the same maximum stress level) has the same stress dependence as the plastic strain that occurs between the 1st and the 1000th cycle, and exhibits a maximum. A creep pre-strain before the cyclic tension tests considerably decreases the elongation measured during cycling.
Behavior in Fatigue-Relaxation of a High-Creep Resistant Type 316L Stainless Steel
Authors: Mottot M , Pétrequin P , Amzallag C , Rabbe P , Grattier J , Masson S
Published: March 2009

In order to predict long-term behavior of a high-creep resistant low-carbon Type 316L stainless steel under low-cycle fatigue with long hold times, a series of tests of fatigue relaxation was undertaken at 550, 600, 650, and 700°C for medium strain ranges (Δεt = 0.7, 1.2, and 1.6 percent). Hold times up to 5 h were introduced at the maximum tensile strain. It has been shown that a reduction of fatigue life occurred, generally associated with intergranular cracking when hold times increased. A maximal effect was observed at 600°C.

Different methods for extrapolating results for very long hold times, such as those encountered on fast breeder reactor components (∼1000 h) were proposed. These methods were based on a time-temperature equivalence comparable to those used for extrapolating creep rupture data. A correlation between reduction of fatigue life with the amount of stress relaxation during hold times was also used. Predictions by these methods are compared with ASME N47 fatigue design curves.
Assessment of High-Temperature Low-Cycle Fatigue Life of Austenitic Stainless Steels by Using Intergranular Damage as a Correlating Parameter
Authors: Levaillant C , Pineau A
Published: March 2009

Strain-controlled continuous fatigue and creep-fatigue experiments are reported for two types of 316 steel tested at 600°C (1112°F). It is shown that, although the continuous fatigue properties of the two materials are very similar, the one containing a controlled amount of nitrogen exhibits a better creep-fatigue resistance than the other alloy. Detailed measurements of intergranular damage made either on the fracture surfaces or in the bulk of creep-fatigue specimens indicate that the susceptibility of the materials to the effect of tensile hold times can be related to their propensity to intergranular cracking. A stress relaxation-propagation reduction factor per cycle correlation is proposed in order to account for the detrimental effect of tensile hold times on the fatigue life. This correlation relies upon experimental results on austenitic stainless steels published in the literature. It is shown that the proposed approach, derived largely from the quantitative measurement of intergranular damage, holds some promise for predictive purposes.
Low-Cycle Fatigue Behavior of Thick High-Strength Steel Plates for Pressure Vessels
Authors: D'Haeyer R , Simon P
Published: March 2009

In this study of low-cycle fatigue, the following steels were evaluated: (1) two reference steels used in pressure vessel construction, A 543, Grade B (200 mm thickness) and St 52-3 (50 mm thickness); these steels were also studied after heat treatments simulating heat-affected zones of weldments with heat inputs ranging from 10 to 150 kJ/cm; (2) one structural steel, St E47 (50 mm thickness), after either normalization or quench-tempering treatment in order to compare two characteristic values of the yield strength/ultimate tensile strength ratio; and (3) fifteen experimental steels (28 mm thickness) in a thermal condition simulating the water quenching at the core of a plate 200 mm thick, this quenching being followed by a tempering.

Smooth and notched specimens were fatigue tested at 20 and 350°C under completely reversed tension-compression. The imposed diametral strain range was controlled to a constant value throughout each test.

Results were compared with ASME design curves and showed sufficient performances in all cases, so that the choice of the steel may be based upon another use property or economical argument. Nevertheless, differences between steel fatigue properties were studied by statistical methods as a function either of the tensile properties or of the chemical composition in the case of quenched and tempered steels. Concerning these last correlations, the influence of chromium at 350°C was particularly noted.
Influence of Local Strain Distribution on Low-Cycle Fatigue Behavior of Thick-Walled Structures
Authors: Grubisic V , Sonsino CM
Published: March 2009

An optimum design of thick-walled components such as high-pressure vessels and reactor vessels requires knowledge of the local strain distribution, the strain/stress state, and the material's behavior under elastic-plastic deformations. The multiaxial strain-state is transformed into a uniaxial strain-state according to Von Mises's yield criterion. Fatigue experiments on planar and cylindrical specimens with high strain concentrations and biaxial strain-states prove that low-cycle material properties as determined from unnotched specimens can be applied for design based on a defined initial crack length. A design including the stage of crack-propagation can be practiced only in special cases; in general it can not be recommended because of very high strain intensities and the resulting small critical crack depths, as service experience shows. For the functional reliability of the component it is also important that the local structural yield point, which can be a multiple of the material's yield point, is not exceeded by maximum loading. When designing such structures prestrains resulting from manufacturing or overloading must also be considered. Tests carried out with prestrained specimens show that fatigue life is decreased with increased prestrain due to cyclic softening.
Meeting Construction Aggregate Fracture Requirements with Natural Product-Sized Material
Authors: Polhemus BH
Published: March 2009

Areas of the country which are not fortunate enough to have ample accessible supplies of good quarry stone rely on diminishing gravel deposits for the bulk of their construction aggregates. This paper intends to show how producers in those areas which have strict minimum fracture requirements for asphalt material can utilize a larger portion of the natural supplies.

Wear course asphalt specifications often require 80 to 100 percent of the particles in the asphalt mix which are retained on the #4 mesh to have at least one fractured face.

Field experience has shown consistently that centrifugal impact crushing of natural aggregates that are already within this size range achieves fracture counts of 80 to 95 percent, often in a single pass. The operator can then utilize this material and reduce or eliminate the need to separate, handle, and stockpile a waste material.

A centrifugal impactor can accomplish this because it does not depend on a “closed side setting” to achieve crushing as do compression units, so virtually every particle entering the machine has an equal chance of fracturing, even if it is already product size.

On the other hand, the vertical shaft impactor has the ability to minimize the loss to fines (minus #10 mesh) often a problem with conventional horizontal shaft impactors. This is a direct result of the crusher's geometrical design and its control of the trajectory of the rock. The design minimizes scuffing on the rock and incorporates no grinding path, consequently allowing the option of reducing production of fines.

The requirement for fractured faces on asphalt aggregate is an important parameter to assure proper interlocking of particles and stability of the resulting asphalt mix. But with the proper equipment the operator can meet this requirement, waste less material, and conserve more of the often scarce high-quality aggregates.
Stresses and Strains in Roofing Membrane Caused by Substrate Movements
Authors: Guay F , Persoz B
Published: March 2009

A computer program permits the estimation of stresses and strains in multi-ply membranes. This program covers the case of membranes fully bonded on: (1) a concrete substrate: sudden opening of a crack and (2) thermal insulating materials in two different situations: (a) time-linear opening of the joint between two boards caused by the drying of the board and (b) time-sine opening of the joint due to dilatation and shrinkage of the boards (day/night cycles, sun/rain cycles).

The constituent materials of the roofing are considered as elastic (coated sheets) and viscous (adhesives). The computer program provides a better insight into the operation of multi-ply membranes. It describes also the influence of the properties and dimensions of the constituent materials on the stresses and strains in a membrane as a whole and in its constituents (coating and felt).
Lap Joint Strengths of Loose-Laid and Adhered Single-Ply Roof Systems
Authors: Dupuis RM , Moody WR
Published: March 2009

A series of lap joint strength and elongation tests were run on plastomeric, elastomeric, and modified bitumen single-ply roof materials. Various lap lengths were used; the effects of high temperature 66°C (150°F) and low temperature −29°C (−20°F) were evaluated also. Loose-laid-membrane lap joints were tested as well as adhered-modified bitumen lap joints. The behavior of modified bitumen lap joints made by torching and hot asphalt were studied as well as their behavior over built-up roofing (BUR) specimens containing a roof split.
Bonding Ethylene Propylene Diene Monomer Roofing Membranes: The Theory and Practice of Adhering Vulcanized Ethylene Propylene Diene to Itself
Authors: Westley SA
Published: March 2009

Single-ply roofing has now become a significant factor in today's industrial and commercial flat-roofing market. The single-ply roof made from ethylene propylene diene monomer (EPDM) rubber, while possessing outstanding sheet properties, does present opportunities to improve seam adhesion owing to the inert nature of the EPDM and the surface presented for on-site bonding.

The author examines the surface of several commercial EPDM sheets with the scanning electron microscope and finds an absolute requirement for cleaned surfaces for adhesion. Classical adhesion theory is used to suggest ways to improve or develop adhesive systems that would be more compatible with EPDM. Of all adhesive systems available, the neoprene-phenolic contact adhesive is the predominant class used on site.

Results from peel and shear testing of adhesive joints made from EPDM membranes with contact adhesive are revealed with and without a proprietary primer designed to bridge the polarity between rubber and adhesive. This primer is suggested for further study to improve adhesion on field applied lap seam joints.
Eight-Year Atmospheric Corrosion Performance of Weathering Steel in Industrial, Rural, and Marine Environments
Authors: Townsend HE , Zoccola JC
Published: March 2009

Weathering steel (ASTM A588, Grade B) and steels with 0.021 and 0.21 percent copper were tested for corrosion resistance in marine, rural, and two industrial environments. The results of these tests are represented well by kinetic equations of the form C = AtB, where C is the corrosion loss, t is time, and A and B are constants. On the basis of the time required to achieve a 250-μm (0.01 in.) thick ness loss that is calculated using these equations, the weathering steel is 6 to 19 times more durable than the 0.021 percent copper steel and 2 to 10 times more durable than the 0.21 percent copper steel.
Methods for Using Nymphs of Burrowing Mayflies (Ephemeroptera,Hexagenia) as Toxicity Test Organisms
Authors: Fremling CR , Mauck WL
Published: March 2009

Burrowing mayflies (Hexagenia), which are widespread in the Western Hemisphere, are important members of aquatic ecosystems, where they convert organic detritus and its contained biota into food for many fish species. Their distribution has been altered by pollution, and they offer distinct advantages over fish as concentrators and indicators of aquatic contamination. Their biology is well known. Because they are easily cultured, handled, and observed, Hexagenia nymphs are excellent toxicity test organisms. When supplied with inert artificial substrates, nymphs are useful in a variety of static and flow-through bioassay procedures (acute or chronic).
Review of Freshwater Bioassay Procedures for Selected Amphipods
Authors: Arthur JW
Published: March 2009

Methods previously used for performing gammarid bioassays and several important life-cycle requirements are reviewed. The discussion is largely based on methodology for the amphipods Gammarus fasciatus, Gammarus lacustris, and Gammarus pseudolimnaeus, but additional evidence, gathered from other selected freshwater crustacean tests, is included. The survival rate, acclimation period, test chamber size, and age of the amphipods are discussed for short-term tests. The survival rate, isolation versus nonisolation of gravid females, sex ratios during the reproductive period, and test duration are considered for the long-term tests. Primary emphasis should be placed on flow-through methods. The particular problem under investigation will ultimately determine the methods and species required. At present, the choice of species may be G. lacustris because a higher success in laboratory culturing has been achieved for this species, and more information is available about its life-cycle requirements.
Reference Toxicants in Quality Control of Aquatic Bioassays
Authors: Lee DR
Published: March 2009

Use of a reference toxicant promises to improve the usefulness of toxicity tests. Criteria such as <10 percent mortality during a pretest acclimation period indicate only that the test organisms can survive the holding facility. A more reliable and logical method is to use a reference toxicant to estimate the fitness of organisms. Coupled with other standard bioassay procedures, a reference toxicant enables interlaboratory and intralaboratory comparisons of toxicity information to be made. In the context of invertebrate toxicity tests, where the available space and numbers of organisms are not so limiting as in fish bioassays, routine testing of a reference toxicant, conducted in conjunction with routine bioassays, is a realistic expectation.

One problem with reference toxicant information is the question of what can be done when the test organisms are inexplicably abnormal in their resistance. A proposed solution is to use a “sensitivity factor” to adjust the LC50 values obtained with the abnormal test group.

Sodium pentachlorophenate is recommended as a reference toxicant. It has a convincing history of use in toxicity testing, it is fast acting and nonselective in its toxicity to both invertebrates and fish, and it is recognized as an environmental contaminant. Other potential reference toxicants are also considered.
Assessment of Fire Risk for Exterior Structural Members
Authors: Gewain RG
Published: March 2009

The traditional fire exposure in fire tests used to evaluate the performance of construction materials is the standard time-temperature curve specified in ASTM Fire Tests of Building Construction and Materials (E 119-80). There is growing concern that the severity of a fire defined by ASTM Method E 119-80 may not be representative of most fires which occur in buildings such as offices, schools, hotels, apartments, and other similar occupancies. Extensive research on postflashover conditions in building compartments supports this concern. However, the heating conditions in ASTM Method E 119-80 are not appropriate for exterior structural members. Therefore, research described in this paper provides a simple method for describing fire exposure of structural members located outside the enclosing walls of buildings.

The following procedure establishes the intensity of the fire in the compartment under ventilation-controlled or free-burning conditions, the shape and size of the flame emerging from openings in exterior walls of the fire compartment, and the temperature of the flame, all of which are needed to calculate the heat transfer to structural members outlined by the American Iron and Steel Institute.
Analysis of Load Tests on Instrumented Steel Test Piles in Compressible Silty Soil
Authors: Bozozuk M , Keenan GH , Pheeney PE
Published: March 2009

Axial compression and tension tests were performed on two end-bearing piles (one pipe and one H-pile) and two friction piles (one pipe and one H-pile) 3 months after they were driven through a granular test fill into compressible clayey silts. In analyzing the behavior of the piles, skin friction equations were developed based upon effective stresses in the soil, the soil-pile friction factor and the Poisson's ratio of the pile. These equations satisfactorily estimated the distribution of negative skin friction loads mobilized on the piles before they were test loaded and the skin friction mobilized in the axial compression and tension pile tests at failure. The equations were also applied to some well-documented pile tests, and showed that the skin friction that can be mobilized to resist axial compression loading can be estimated from pullout tests. This paper discusses the pile test procedures and the observed relative movements between the pile tips and the surrounding soil at various loads applied to the piles and describes a laboratory test method for measuring the coefficient of friction between the pile and the soil.
Capacity of Reinforced and Prestressed Concrete Pile Sections
Authors: Gamble WL
Published: March 2009

Information needed to compute the nominal strengths of various pile cross sections that are subjected to combined compressive thrust and bending moments is presented, with examples of moment-thrust interaction diagrams for several typical kinds of pile sections.

The components of the factor of safety are examined, with particular emphasis on the reliable strength of the pile section. The use of a “strength reduction factor,” a multiplier that is less than 1.0, to establish a reliable or minimum expected failure load that is somewhat lower than the nominal failure load to be expected from an ideal member is discussed.

This strength reduction factor may vary with the number of piles in an individual footing and should be higher for piles that can be inspected than for those that cannot be inspected after completion. Precast piles and piles that are cast in permanent metal cylinders are examples of members that can be inspected to different extents, while piles cast-in-place in unlined holes or that have the liner pulled out of the hole after the concrete is cast are examples of members that cannot be easily inspected after construction.
Design of High-Performance Prestressed Concrete Piles for Dynamic Loading
Authors: Gerwick BC , Brauner HA
Published: March 2009

Although prestressed concrete piling have given exemplary performance as foundation piling and there exists ample guidance as to their design, manufacture, and installation for such purposes, recent extensions of their application to more demanding situations requires a renewed look at the criteria for longitudinal prestress (precompression) and spiral confinement.

Problem areas include the occasional occurrence of transverse cracking under heavy driving into erratic soils, longitudinal cracking during and after installation, and the need for ductile response to imposed deformations due to earthquakes.

A more rational analysis is attempted to explain and quantify these phenomena and the stresses and strains developed. Recommendations are then made giving values of prestress and steel requirements that will enable these severe criteria to be met. Some of these recommendations are supported by tests that are as yet unreported elsewhere.

It is believed that these recommendations will enhance the capabilities of prestressed concrete piling and thus make practicable their extension to more demanding applications.
The U.S. Army's Industrial Hygiene Sampling Guide
Authors: Belkin F , Bishop RW
Published: March 2009

The U.S. Army Environmental Hygiene Agency (USAEHA) has developed an industrial hygiene (IH) sampling guide for collecting over 100 types of air and bulk samples. The guide includes the minimum, maximum, and optimum air volumes, recommended sampling rates, and sampling methods for air samples. For bulk samples, the types of containers and amounts of sample required are noted. This sampling guide is used by all Army industrial hygienists and industrial hygiene technicians involved in IH sampling. It provides a summary of sampling procedures and provides a range of flow rates and volumes which enables the field personnel to sample using methods which are compatible with the Agency's state-of-the-art laboratory procedures.
Evaluation of Employee Exposure to Trinitrofluorenone from Electrophotographic Printers and Copiers in a User Environment
Authors: McCullen RE , Sanghvi AN
Published: March 2009

A method has been developed for analyzing 2,4,7-trinitrofluoren-9-one (TNF) emission from electrophotographic printers and copiers. This method evaluates air, swipe, and bulk samples which have been extracted in tetrahydrofuran (THF). Analysis is performed by high pressure liquid chromatography (HPLC) using an ultraviolet (UV) detector. Air particulate samples are collected on 0.8-μm silver membrane filters. The air sampling method and analysis allows the detection of 100 nanograms of TNF in one cubic meter of air with an equivalent sensitivity of 0.5 ng per injection.
Passive Colorimetric Dosimeter Tubes for Ammonia, Carbon Monoxide, Carbon Dioxide, Hydrogen Sulfide, Nitrogen Dioxide, and Sulfur Dioxide
Authors: McConnaughey PW , McKee ES , Pritts IM
Published: March 2009

Colorimetric, stain length, personal dosimeters operating by gas diffusion have been developed to determine worker exposure for up to an 8-h period for several inorganic airborne contaminants in the range of their threshold limit values. Length of stain, colorimetric dosimeters have been made for the detection of ammonia (NH3), carbon monoxide (CO), carbon dioxide (CO2), hydrogen sulfide (H2S), nitrogen dioxide (NO2), and sulfur dioxide (SO2) in air. For each gas detection system, the sampler depends on the transfer of the gas by diffusion into a glass tube containing a colorimetric length of stain indicator. The stain length developed in a given period of time is compared to a calibration chart to determine, on the spot, the average gas concentration to which the dosimeter has been exposed. These dosimeters are known by the trade name Vapor Gard.
Effects of Moisture, Residual Thermal Curing Stresses, and Mechanical Load on the Damage Development in Quasi-Isotropic Laminates
Authors: Kriz RD , Stinchcomb WW
Published: March 2009

This investigation demonstrates how moisture absorbed in [0/±45/90]s and [0/90/±45]s graphite epoxy laminates significantly alters the stress state and chronology of damage development along the laminate edge during static tension and tension-tension cyclic loading.

Emphasis is placed on using reasonable approximations for wet and dry elastic properties, including out-of-plane properties (v23 and G23), since these properties are required by finite element and shear lag models to predict the stress state at the laminate edge.

Moisture was observed to alter the dry edge stress state in the 90-deg plies of the [0/±45/90]s laminate such that delaminations occurred at a lower load and transverse cracks occurred at a higher load. A model was developed which predicted the differences in loads required to initiate damage in the 90-deg plies of the two laminates in the wet and dry conditions.

Although moisture can alter the chronology of damage development, the damage state in each laminate observed prior to fracture appeared to be independent of moisture content.
Mechanisms of Fatigue Damage in Boron/Aluminum Composites
Authors: Johnson WS
Published: March 2009

Fatigue damage mechanisms have been investigated using a series of tension fatigue tests on several laminates of boron/aluminum (6061-0). This study focuses on four aspects of the fatigue response. First, in laminates with 0-deg fibers on the outside, an analysis that identifies “shakedown” conditions is shown to predict the stress amplitude below which no fatigue damage accumulates. Second, a simple fatigue damage accumulation model which relates matrix fatigue cracking and the overall laminate properties is described. A model for the saturation damage stage development is presented. Third, data illustrate that identical laminates, tested in directions 90-deg apart (such that one layup has 90-deg outer plies and the other 0-deg), have different fatigue behaviors due to the stacking sequence. The 90-deg plies on the surface develop cracks earlier than predicted by shakedown. An attempt is made to explain this stacking sequence effect. Finally, variable load history effects on the fatigue damage response are investigated by simple tests. These tests reveal that for a given stress ratio the specimen seeks the saturation damage state for the largest stress range to which it is subjected. It also was found that little damage is generated by shifting a given stress range down, whereas significant damage may be created by shifting it upward.
Stiffness-Reduction Mechanisms in Composite Laminates
Authors: Highsmith AL , Reifsnider KL
Published: March 2009

It now is recognized widely that stiffness changes during the service loading of composite laminates can be significantly large, especially as those changes affect deflections, dimensional changes, vibration characteristics, and load or stress distributions. Several generic sources of stiffness change can be identified, in various degrees, in fibrous composite materials. The source which occurs quite early in the life of a specimen or component is matrix cracking, the subject of this paper. While most laboratories now report stiffness changes, very little systematic philosophy has been developed to account for and explain such stiffness changes. The complexity of this situation requires systematic study, and motivates the search for a model, or models, which can describe the behavior and predict unfamiliar response. The present paper reports the results of an experimental program and an analytical modelling exercise which indicate that much of the observed matrix cracking can be predicted and the effects on stiffness calculated with various degrees of accuracy depending upon the sophistication of the model used.
The Dependence of Transverse Cracking and Delamination on Ply Thickness in Graphite/Epoxy Laminates
Authors: Crossman FW , Wang ASD
Published: March 2009

(25/-25/90n)s, n = 1/2, 1, 2, 3, 4, 6, 8, and (252/-252/902)s T300/934 graphite/epoxy laminate coupons were tested in tension and examined periodically by di-iodobutane (DIB) enhanced X-radiography following progressively larger increments of applied load. The tensile strain required to initiate transverse cracking in the 90-deg ply was found to depend on the thickness of the 90-deg layer. For n ≤ 3 delamination was initiated at the edge of the coupon. The onset of delamination occurred before or after transverse cracking, depending on the laminate construction. For n ≥ 4 delamination at the 25/90 interface was initiated across the entire width of the coupon by the formation of a transverse crack in the 90-deg ply. In some laminate constructions the location of specimen separation during final fracture was associated with the growth and coalescence of edge delaminations under either incrementally increasing or constant strain cyclic loading. Comparisons of experiments to the fracture sequence predictions by stress and energy analysis are made to assess our ability to account for the ply thickness dependence of fracture in these laminates.
Characterizing Delamination Growth in Graphite-Epoxy
Authors: Wilkins DJ , Eisenmann JR , Camin RA , Margolis WS , Benson RA
Published: March 2009

As part of an overall effort to develop durability and damage tolerance methodology for graphite-epoxy composites, coupon specimens have been developed to measure the fundamental static fracture and subcritical growth behavior of delaminations. Two basic designs, one for the tensile opening mode (Mode I) and one for the forward shear mode (Mode II), are described. These specimens were used to characterize the behavior of two types of interfaces (0/0 and 0/90) for static fracture, constant amplitude fatigue, and spectrum fatigue. Fracture mechanics technology was applied through the principles of strain-energy release rate. Three-dimensional finite-element analyses were employed to interpret the experimental results. A simple growth law was shown to correlate the constant-amplitude and spectrum-growth data. It was found that the applied cyclic load must be nearly equal to the critical static load to obtain observable growth in the tensile opening mode. On the other hand, the graphite-epoxy delamination growth rate in the forward shear mode is comparable to the aluminum growth rate in tension, which suggests that shear is the chief subcritical growth mode for graphite-epoxy.
An Assessment of DDT Toxicity on Osmoregulation and Gill Na, K-ATPase Activity in the Blue Crab
Authors: Neufeld GJ , Pritchard JB
Published: March 2009

The sodium, potassium adenosine triphosphatase (Na,K-ATPase) of the gill is responsible for the ability of the blue crab (Callinectes sapidus), to maintain serum osmolality in dilute environments. Thus, the inhibition of this enzyme might lead to osmoregulatory failure. To determine whether this mechanism plays a role in DDT toxicity in the blue crab, the effects of DDT on gill Na,K-ATPase activity and osmoregulation were examined in adult crabs. When DDT was presented to gill homogenates in vitro, Na,K-ATPase was significantly inhibited at a concentration of 1.0 ppm DDT. Essentially maximal inhibition occurred at 9.0 ppm. The injection of a sublethal dose of DDT (0.3 ppm) into the live animal produced a temporary decline in hemolymph osmolality. However, by 28 h after transfer of the animal to a dilute environment, the values for osmolality and Na,K-ATPase activity were virtually identical to those of controls. Since the intact animal showed only a transient osmoregulatory response to DDT, even though the Na,K-ATPase was sensitive to DDT in vitro, the authors suggest that, in vivo, either (1) rapid induction, or activation, of new Na,K-ATPase activity or (2) excess sodium transport capacity protects the crab from osmoregulatory difficulty.
Acephate and Fenitrothion Toxicity in Rainbow Trout: Effects of Temperature Stress and Investigations on the Sites of Action
Authors: Duangsawasdi M , Klaverkamp JF
Published: March 2009

The detection of organophosphate (OP) insecticide pollution in natural waters requires knowledge of the physiological target sites and the mechanism of action of these chemicals in fish. This study was designed to determine the acute lethality of acephate (ATE), a phosphoramidothioate, and fenitrothion (FTN), a phosphorothionate, on rainbow trout fingerlings at three test temperatures; the sublethal effects of ATE and FTN on heart rate (HR), ventilation rate (VR), buccal amplitude (BA), and cough frequency (CF) in adult rainbow trout; and the effects of ATE and FTN on the brain, erythrocyte, gill, heart, serum, and skeletal muscle cholinesterase inhibition (ChEI) in these fish. From our results, the LC50 values of ATE were approximately 600 to 1000 times greater than those of FTN. Temperature affected the LC50 values, median survival times, and slopes of mortality curves of FTN, but not those of ATE. Both insecticides produced a decrease in HR, and an increase in VR and BA. FTN produced an increase in CF, but ATE did not. The cholinesterase activity in the erythrocytes, gill, heart, and serum showed marked inhibition after 3 h of exposure to ATE, compared with 1 h of exposure to FTN. More time was required to attain maximal inhibition in the brain and skeletal muscle than in other tissues. This study indicates that the cardiovascular and respiratory systems in fish are important sites of action for OP toxicity, and that this toxicity depends on physicochemical properties, for example, lipid solubility, and on environmental factors, for example, temperature.
Uptake, Depuration, and Toxicity of Hexamethylphosphoramide in Aquatic Organisms
Authors: Schneider PW , Gibson JR , Cramm GC , Shrivastava SP
Published: March 2009

Aquatic toxicity tests were undertaken to evaluate the environmental significance of hexamethylphosphoramide (HMPA), an industrial solvent which has been shown to be an animal carcinogen.

Hexamethylphosphoramide's 48-h LC50 to Daphnia magna and 96-h LC50 to bluegill sunfish (Lepomis macrochirus) were 4220 mg/litre and 7420 mg/litre, respectively. In concentrations up to and including 5140 mg/litre, HMPA did not interfere with the normal development of Eastern oyster (Crassostrea virginica) embryos to the veliger stage. Both sheepshead minnows (Cyprinodon variegatus) and Eastern oysters developed concentrations of HMPA in their tissues rapidly from 0.5, 8.4, and 40.4 mg/litre treatments, with the plateau concentrations rarely exceeding the exposure concentrations. Whole-body residues peaked in about three to seven days after the initiation of exposure. Sheepshead minnows demonstrated a greater ability to metabolize HMPA than oysters, while oysters depurated HMPA and its metabolites more rapidly than fish. Both species largely eliminated HMPA and its metabolites within one day of depuration. The bioconcentration factors for fish and oysters were less than four, which suggests that HMPA does not pose a substantial environmental hazard from the standpoint of its accumulation in aquatic organisms. The oyster mortality in the 8.4 and 40.4 mg/litre treatments was appreciably greater than that in the controls, while the fish mortality was similar among all the treatments and the control.
Considerations in Assessing the Potential for, and Significance of, Biomagnification of Chemical Residues in Aquatic Food Chains
Authors: Macek KJ , Petrocelli SR , Sleight BH
Published: March 2009

The relative importance of dietary and aqueous exposure of bluegill sunfish to di(2-ethylhexyl) phthalate, 1,2,4-trichlorobenzene, and leptophos are quantitatively evaluated at steady state. The results of this investigation indicate that the incremental steady-state body burden due to dietary exposure is statistically indistinguishable from that due to aqueous exposure. Critical analyses of similar studies with cadmium, endrin, and Kepone support the hypothesis that biomagnification of chemical residues within aquatic food chains is quantitatively insignificant when compared with the process of bioconcentration of chemical residues directly from water. Dichlorodiphenyltrichloroethane (DDT) appears to be the only chemical of those evaluated with a potential for significant accumulation of residues through an aquatic food chain. Data on the biological persistence of chemicals in aquatic organisms, as measured by the rate of depuration from tissues, appear to offer a mechanism for identifying those few chemicals which may have potential for measurable accumulation through food chains. All of the data presented indicate that the process of biomagnification, as classically defined, probably does not occur within communities of aquatic organisms.
An Approach to the Toxicological Evaluation of a Complex Industrial Wastewater
Authors: Pearson JG , Glennon JP , Barkley JJ , Highfill JW
Published: March 2009

The U.S. Army is currently conducting research to develop the data base required to establish water quality criteria for wastewater discharged from 2, 4, 6-trinitrotoluene (TNT) production facilities. Because over 30 munitions-related compounds are involved, a traditional compound-by-compound approach to the toxicological evaluation of this complex wastewater was considered both technically unacceptable and economically prohibitive. An alternate approach was developed that placed research emphasis on the toxicological evaluation of a representative wastewater mixture. The initial task, therefore, was to conduct a detailed wastewater chemical characterization study over a period of several months. Wastewater constituents were identified and quantified, and, through the use of statistical procedures, a mixture representative of the actual wastewater was defined. Only 22 of the compounds identified in the actual wastewater were detected consistently above the parts-per-billion detection limit. These were included in the mixture designated for detailed toxicological testing. To identify possible trace constituents with extraordinary toxicological properties, all the identified compounds received screening-type toxicological testing. In addition, in attempting to relate the toxic properties of the mixture to its components, detailed toxicological studies are continuing to be conducted on selected components of the mixture, that is, on major components and on extremely toxic minor components.

We believe that this combined approach of single compound and mixture testing provides both an economical and scientifically acceptable approach to the development of water quality criteria for complex industrial wastewaters that remain relatively constant over time. In this approach the “no-effect” level determined from chronic toxicity studies with the mixture will be the principal basis for the water quality criteria. This will be supplemented with the identification of components with extraordinary toxicological properties and the definition of the dose-response relationship for the major toxic compounds in the mixture.
Criteria for Trap Evaluation
Authors: Temme Manfred , Jackson WB
Published: March 2009

The trap is one of man's oldest devices for animal control. The effectiveness of a trap is usually considered to be determined by extrinsic factors rather than by an animal's behavior. The effect of rodent instinctive and social behavior on trap success is little studied or understood. In considering how behavior studies might affect trap design or placement, aspects of rodent behavior, such as neophobia, dominant and subordinate group relationships, trap approach and contact, and duration of “trap shyness,” deserve attention. With the frequent appearance of new and modified traps, a comparative basis for efficacy evaluation is desirable. General observations on the behavior of a population of Norway rats (Rattus norvegicus) toward two varieties of traps form the basis for suggestions on an evaluation protocol.