bluuebunny/crossref_metadata_2025 huggingface dataset:
Simulated Precipitation Reference Materials: Measurement of pH and Acidity
Authors: Koch WF , Marinenko G
Published: March 2009

The Center for Analytical Chemistry of the National Bureau of Standards has prepared and analyzed several series of simulated precipitation reference materials to be used as a means of intercalibrating atmospheric monitoring stations. In addition, research has shown serious errors in the measurement of pH and acidity determined in solutions of low-acidity and low-ionic strength. Contingent on further research pH measurements of acid rain should not be reported with greater confidence than 0.1 pH number. Titrations for total acidity should be performed to an inflection point or Gran plot endpoint and not to a fixed pH endpoint. Improved measurement protocols and reference standards are necessary to assure measurement comparability and consistency throughout the nation.
Practical Quality Control of Rainwater Analyses
Authors: Tyree SY
Published: March 2009

A detailed picture is presented of the internal consistency of the data generated by a typical acid rain monitoring system. Three independent techniques may be applied in the assessment of rainwater acidity: pH measurement, titration, and charge balance. Each is described. On the assumption that one solution can have only one acidity value, the three techniques present an excellent test for data consistency. Typical results from two extensive monitoring systems are shown.

The difficulties inherent in the titration technique are: agreement on protocol, reagent impurities, carbon dioxide interference, and weak acid end points. It will be shown that the titration technique is to be recommended in a very limited number of cases. The pH measurement technique is recommended provided it is understood that accuracy no worse than ±0.2 of a pH unit is acceptable. Methods of minimizing error are discussed. The charge balance method presumes the measurement of eight ions, minimum. Error sums and ultimate accuracy are described. Methodology recommendations are made. Practical results of analyses of real samples collected and analyzed by very inexperienced personnel under “adequate” supervision are shown.
Analysis of Rain by Ion Chromatography
Authors: Fitchett AW
Published: March 2009

Ion chromatography (IC) incorporates ion exchange chromatography coupled to eluent suppression and electrical conductivity detection for the sequential elution and determination of anions or cations. In the area of rainwater analysis, IC offers the ability to determine anion and cation profiles at below parts per million levels in very small samples. IC is being used presently in several rain sampling networks such as Environmental Protection Agency, National Oceanic and Atmospheric Administration, and the United States Geological Survey. The parameters that are commonly measured by IC in rainwater are fluoride, chloride, phosphate, nitrate, sulfate, sodium, ammonium, potassium, calcium, and magnesium.

This paper deals with all aspects of IC as it pertains to rainwater analysis and includes theory and instrumentation along with sample analysis. Details on the precision and accuracy of the technique and a comparison to other methodology are shown.
Applications of Within-Event Precipitation Chemistry Measurements
Authors: Raynor GS , Hayes JV
Published: March 2009

Chemical measurements from hourly sequential precipitation samples and simultaneous meteorological measurements and observations were analyzed to discover relationships between chemical species, infer atmospheric mechanisms, relate precipitation chemistry to meteorological events and conditions, and identify probable pollutant source regions. Analytical methods that can be applied to short-period samples, but usually not to event, weekly, or monthly samples, are described and illustrated.

Changes in concentrations of chemical species during precipitation events can be documented and used to infer atmospheric processes. These changes can be related also to meteorological conditions such as changes in rainfall rate and wind direction or to frontal passages. Source directions and probable source regions can be located by wind direction and trajectory analyses. Means of many samples taken under similar conditions can document relationships between meteorological conditions, concentrations in precipitation, and amounts of wet deposition.
The Updating Process in Precipitation Quality Networks
Authors: Still ME
Published: March 2009

With the increasing awareness of the effects on the environment of air pollution, the measurement of the various contributing processes has grown in importance. This paper looks at the monitoring of one of these processes, that of wet deposition caused by precipitation. In the design of a monitoring network measuring the quality of precipitation, there are five general factors to be considered for data quality, namely, network objectives, network design, operations, chemical and data analyses, data products, and quality assurance. A continuous evaluation of all aspects of the network must be undertaken to ensure the quality of the data. The Canadian Network for Sampling Precipitation is used as an example.
Fire Resistant Coverings
Authors: Lieff M
Published: March 2009

Thin coatings (fire retardant) are used to reduce combustibility or surface flame spread of wood or cellulosic building materials. Thick coatings are used to provide fire resistive protection of steel. The characteristics of intumescent and nonintumescent coatings, and thick insulative and energy absorbing (ablative) materials are discussed. Methods of testing are reviewed.
Spray-Applied Fibrous Material Fire Resistive Coatings
Authors: Stumpf FM
Published: March 2009

Mineral fiber compositions for spray-applied fire resistive coatings to buildings are factory mixed products consisting of manufactured inorganic fibers and proprietary binders. Air setting, hydraulic setting, and ceramic binders are used singly or in varying combinations and quantities depending on the use for which the product is designated.

The fibrous materials most commonly used for fireproofing generally range in applied density from 0.2 to 0.6 g/cm3 and range in applied thicknesses from 1.0 to 6.0 cm on decks and up to 8.0 cm on beams and columns. The spraying process is generally performed with a specially designed machine that feeds the dry mineral fiber composition to a spraying nozzle where the fiber mixture is enveloped with water as it is sprayed onto the surface to be protected. Fire resistant characteristics and other important properties such as insulation and acoustics, and resistance to air erosion and corrosion are discussed.
Evaluation of Fire Resistive Coatings Based on Small-Scale Fire Testing
Authors: Schultz N
Published: March 2009

Economics and short-time factors have forced many manufacturers of fire resistive coatings to use small-scale fire tests in accordance with ASTM Standard Method of Fire Tests of Building Construction and Materials (E 119-81) time-temperature curve. The difference between small-size and full-size furnaces is not so much in the geometry as it is in the construction. Insulation, burners, and fuel type are influencing factors when making a comparative analysis. The American Iron and Steel Institute (AISI) used a full-size column furnace and a small-column furnace in one of their programs. The correlation between data was substantial enough to focus the attention on using the small furnace as a valid means of testing.

Within the same scenario of small-scale testing, a high intensity fire test (HIFT) is established to simulate a petroleum spill fire. It is being used by the petrochemical industry and fire resistive coating manufacturers to evaluate materials under reproducible simulated thermal conditions of a petrochemical fire.
Surface Preparation of Steel for Fire Resistive Coatings
Authors: Berry PL
Published: March 2009

The preparation of steel substrates to receive fire resistive coatings has not been formally investigated. The types and conditions of steel surfaces are analyzed from a climatic, physical, and chemical point of view, and recommendations for each condition are made.
Inspection Procedure for Field Applied Sprayed Fire Protection Materials: The Need for Standards
Authors: Erwin G
Published: March 2009

This paper deals with the problems and the usefulness of “field inspections” of spray-applied fire resistive materials, which hopefully will develop a useful dialogue leading to the development of an ASTM standard procedure.

To date, neither ASTM Subcommittee E06.21 on Serviceability nor the manufacturers' association has been successful in advancing to an ASTM level, an acceptable procedure. The Association of the Wall and Ceiling Industries-International, working with manufacturers and other interested groups, has developed a procedure that appears to have gained some acceptance and is being used.

This paper will address methods of determining such physical and visual characteristics as substrate condition, thickness, density, bond strength (adhesion and cohesion), finished appearance, and reproducibility of ASTM Fire Tests of Building Construction and Materials (E 119-81) tested assemblies.

It is hoped that this presentation will generate interest in developing an ASTM industry standard procedure readily usable in the “field.”
Surface Acidity Distribution on Precipitated Silicas
Authors: Krivak TG , Clark M
Published: March 2009

Precipitated silicas are carriers for a variety of formulations used in agricultural applications. In such formulations, interaction between the agricultural chemicals and the carriers must be minimized. Precipitated silicas are known to have reactive acid sites on their surfaces, which can cause catalyzed chemical decomposition. An investigation into factors that affect the acid site distribution of precipitated silicas is described in this report.

Commercially available and laboratory-prepared precipitated silicas were suspended in isooctane treated with incremental amounts of n-butylamine solution. The distribution of acid sites of different strength was determined by using six Hammett indicators, corresponding to a range of +6.8 to −8.2 pKa, in conjunction with spectrophotometric analysis of the suspensions.

Variations in blocking agents, impurities, and salt content are shown to account for alterations in the acid site distribution on the silica surface. Control of these factors will aid the agricultural formulator in minimizing chemical/carrier interaction.
Formulation and Application of Microbial Insecticides for Forest Insect Pest Management: Problems and Considerations
Authors: Lewis FB
Published: March 2009

Aerial applications for microbial insecticides such as Bacillus thuringiensis (Bt) and the Baculoviruses differ widely in effectiveness. The size and density of the droplets, the size and feeding rates of the larvae, the behavior of the insect, and the degradation of the insecticide after its application are among the controlling factors. Distributions of droplets of different sizes have been plotted and compared with the feeding rates of gypsy moth and spruce budworm larvae. In field tests, effectiveness was not always correlated with droplet density.
Analysis of Droplet Spectra and Spray Recovery as a Function of Atomizer Type and Fluid Physical Properties
Authors: Haq K , Akesson NB , Yates WE
Published: March 2009

Drop size, as indicated by the volume median diameter (VMD), and size uniformity, noted by the relative span (RS), were correlated with (1) viscosity, (2) surface tension, (3) viscoelasticity, and also (4) liquid throughput. Two types of nozzles were used, simple orifices or jets and hollow cones. The density of the mixtures did not vary greatly and no correlations were made with this function.

Increased liquid throughput (increased orifice diameter) showed significant effects on drop size, increasing the VMD as the orifice size increased for all nozzles and mixtures tested. Of the liquid properties, viscoelasticity had the greatest effect, increasing drop size as it was increased. Increasing the surface tension increased drop size significantly, but changes in viscosity appeared to have little effect on the drop size produced.

The RS was reduced (narrow range) as surface tension, viscosity, and viscoelasticity were increased. Increased throughput reduced RS at two surface tension levels, but when the viscoelastic polymer was used, the increased throughput actually increased the RS for the nozzles tested.

The atomization process is very complex and the study using kromkote paper collection cards could have benefited significantly if the new Particle Measuring Systems Co. (PMS) in situ system had been available. Nonetheless, the data have considerable relevance to pesticide spray atomization. Further advances will be made as the PMS or similar scanners become more widely available.
Electrodyn Sprayer Pesticide Application Using Electrostatic Atomization
Authors: Sherman ME , Bone JR
Published: March 2009

The Electrodyn sprayer is being extensively tested in the United States to determine its impact on the biological efficacy of selected products. The Electrodyn sprayer uses electricity to atomize certain oil-based pesticide formulations into a spray cloud, electrically charging the resulting droplets with a no-moving-parts nozzle. The atomizing nozzle consists of a pair of electrodes (high and low voltage) and a narrow gap outlet for the pesticide liquid flow. The pair of electrodes subjects the liquid to an intense and divergent electric field as the liquid passes through the thin-slot, high-voltage nozzle. Droplets ranging in size from 25 to 200 μm form when accumulation of a surface electric charge on the liquid produces a loss of fluid surface tension. Droplets emitted from the nozzle travel toward the target along curved electric field flux lines at an average speed of 10 m/s and impinge upon the equipotential leaf surfaces at 90° angles. This results in coverage on both leaf surfaces, known as the wraparound effect. Applications as low as 0.5 L/ha give adequate biological control in some canopies. A vehicle-mounted Electrodyn unit is currently being developed that is a self-calibrating, closed system suitable for row crop spraying.
Formulation, Development, and Application of an Insecticide Granule
Authors: Synek J
Published: March 2009

The initial development of an insecticide granule began with the choosing of a granular carrier for a turf insecticide. The physical properties and application swath width had to be acceptable to both lawn service and golf course applicators.

The properties considered important were the bulk density, dustiness, particle size, number of particles per pound or kilogram, absorptive capacity, and color. The materials evaluated as possible carriers were corncobs, vermicultie, attapulgite, montmorillonite, diatomite, and bentonite.

Bentonite was chosen as the preferred carrier for the development of the granule.

When the final formula was developed, an evaluation of various rotary and drop spreaders was initiated to measure the accuracy of the spreaders as well as the effective swath width. The number of particles per square inch and analyses were compared.

Bentonite survived all the tests and was chosen as the carrier of choice.
Probabilistic Defect Size Analysis Using Fatigue and Cyclic Crack Growth Rate Data
Authors: Trantina GG , Johnson CA
Published: March 2009

The fatigue failure mechanism of many cast metals and high-strength alloys involves initiation and propagation of a crack from an initial defect to a critical size where fatigue failure occurs. Crack growth rate and fatigue data can be combined to estimate the initial size of the defect that led to failure. This technique has been developed and used to provide statistical interpretations of fatigue data and to determine the probabilistic size distribution of critical defects and the specimen size dependence of the average critical defect size.

An expression for the fatigue curve that incorporates the initial defect size (ai) is produced by integrating an analytical expression for the cyclic crack growth rate curve that includes a threshold stress intensity factor. For two different values of ai, two fatigue curves are generated that can represent scatter in fatigue data from two specimens of the same size or average fatigue curves for specimens with two different sizes. This scatter or specimen size effect is best treated along lines of constant initial stress intensity factor that have a slope of −0.5 on the log stress-log life fatigue curve. The separation between fatigue curves along lines of constant initial stress intensity factor is independent of fatigue life. This treatment of fatigue data therefore predicts the commonly observed trend of increasing scatter in fatigue life with increasing lifetime and provides a treatment of scatter that is independent of fatigue life.

Probabilistic defect size analysis has been applied to data for a nickel-base superalloy to predict the size distribution of critical defects. An initial defect size is inferred for each data point, then a distribution of initial critical defect sizes is predicted for the alloy. The Weibull distribution is used to display the data in terms of 1/√ai. The specimen size effect is treated where the square root of the average critical defect size increases with an increase in the effective area of the specimen. Thus, critical defect size distributions in components can be predicted that, in turn, allow material processing and inspection criteria to be based on required component life.
Characterization of the Variability in Fatigue Crack Propagation Data
Authors: Ostergaard DF , Hillberry BM
Published: March 2009

The variability in fatigue crack propagation is studied through the analysis of 68 sets of replica constant amplitude fatigue crack growth data. Each of the a versus N data sets are fit to the integral of a crack growth rate equation through a finite integral optimization routine. The routine determines the best fit crack growth parameters of the crack growth rate equation. Through characterization of the variability in the crack growth parameters and utilizing statistical theory, the variability in the a versus N data is predicted. The finite integral method of obtaining the crack growth parameters was shown to very accurately reproduce the a versus N data. The variability in the crack growth parameters showed a strong linear trend, and a regression analysis on the parameters provided information to accurately predict the variability in the fatigue crack propagation data.
Analysis of Structural Failure Probability Under Spectrum Loading Conditions
Authors: Bronn CE
Published: March 2009

A method is presented for computing the probability of failure of structural members exposed to spectrum loading conditions and subjected to periodic inspections.

The output is failure probability as a function of service exposure time. The effects of perturbations in the severity of service exposure and variations in inspection effectiveness and inspection period length are demonstrated.
Microstructural Origin of Flutes and Their Use in Distinguishing Striationless Fatigue Cleavage from Stress-Corrosion Cracking in Titanium Alloys
Authors: Meyn DA , Brooks EJ
Published: March 2009

Postfracture analysis does not always distinguish striationless low-stress fatigue from stress-corrosion cracking (SCC), since both are characterized by cleavage, together with other less distinct fracture modes. Studies of identical specimens of Ti-8Al-1Mo-1V broken under both conditions suggest that the presence of certain microplastic fracture features called flutes may be uniquely characteristic of SCC, and absent from low-stress striationless fatigue fractures. Some new observations concerning the microstructural origins of flutes verify that they arise from a tendency toward planar slip in α and α-β alloys and from the presence of multiple cleavage during crack propagation under certain circumstances, including SCC.
A Fractographic Investigation of Stress-Corrosion Cracking in High-Strength Steel Alloys
Authors: Fraser FW , Metzbower EA
Published: March 2009

The fracture separation processes of stress-corrosion cracking (SCC) specimens of steels with yield strengths in the 700 to 1400 MPa (100 to 200-ksi) range were investigated by scanning electron microscopy. Plates from a variety of processes were tested and examined. These included the electric furnace, electroslag remelt, vacuum induction melt-vacuum arc remelt, and electric furnace-vacuum arc remelt processes. The materials were studied both in the as-received condition and after heat treatment.

Stress-corrosion cracking tests were carried out on single-edge-notched, fatigue-precracked specimens by the cantilever beam method. The specimens were fractured under stress in an aqueous 3.5 percent sodium chloride solution while galvanically coupled to zinc. The modes of fracture at the fatigue-SCC interface, in the SCC zone, and in the overload area were investigated, and a correlation was drawn between the fracture mode, the microstructure, and the resistance of the steel alloy to stress-corrosion cracking.
Fractographic and Microstructural Analysis of Stress-Corrosion Cracking of ASTM A533 Grade B Class 1 Plate and ASTM A508 Class 2 Forging in Pressurized Reactor-Grade Water at 93°C
Authors: Provenzano V , Törrönen K , Sturm D , Cullen WH
Published: March 2009

Stress-corrosion cracking (SCC) studies were conducted in the following commonly used pressure vessel steels: ASTM A533 Grade B Class 1 (A533-B-1) plate and a fabricated forging that is equivalent in chemistry and thermomechanical processing to American-made ASTM A508 Class 2 (A508-2) forgings. The purpose of these studies was to determine the response of the materials in a simulated pressurized-water reactor environment. Round tensile specimens were bolt-loaded to 75 to 80 percent of yield and left in the water at 93°C for 2000 h. At the end of this time period, the specimens were taken out of the water, unloaded, and examined by scanning electron microscopy (SEM) and by energy-dispersive X-ray analysis. The specimen cut from A533-B-1 plate did not have any cracks as a result of the SCC tests. Several cracks, some of which were visible with the unaided eye, had developed in the specimen that was cut from the A508-2 forging. The polished and etched sections of the specimen that showed SCC, when examined with the SEM, revealed the presence of many microcracks starting from the outside surface and propagating along either inclusion-matrix or carbide-matrix interfaces; the corresponding microstructure was mostly pearlitic. The microstructure of the specimen that did not crack was bainitic; it had fewer inclusions and carbide particles, and no microcracks were observed. When the fracture surfaces of the larger cracks were examined by SEM, they revealed a cleavage-like failure propagating along inclusion bands. X-ray image scans and energy spectra of these bands showed that they were silicate and manganese-sulfide inclusions.

A hydrogen-assisted cracking model has been proposed to explain the experimental results on A508-2 forging. Produced by a cathodic reaction and aided by the stress fields, hydrogen diffuses a head of the crack tip to the inclusion sites. This causes a preferential decohesion at the inclusion—matrix interfaces and subsequent cracking along inclusion bands.

The absence of stress-corrosion cracking in A533-B-1 plate tested under identical experimental conditions is due mainly to fewer inclusion and carbide particles and to the more refined bainitic microstructure of this steel. This type of microstructure is less susceptible than the mainly pearlitic microstructure found in A508-2 forging to hydrogen-assisted cracking.
Hydrogen-Induced Brittle Fracture of Type 304L Austenitic Stainless Steel
Authors: Caskey GR
Published: March 2009

Type 304L stainless steel supersaturated with hydrogen gas fails in tension at 200 to 250 K by brittle fracture. Fracture surfaces exhibit isolated facets oriented 0 to 30 deg to the tensile axis. These facets have many of the characteristics of cleavage fracture. The threefold symmetry of Laue back-reflection photographs and trace analysis of deformation bands on the facets demonstrate that fracture is along {111} planes. The fracture paths were identified as coherent twin boundaries on polished sections through facets and on microcracks across interior grains. Although twin-boundary parting is not commonly observed in alloys with a face-centered cubic (FCC) lattice, these observations for Type 304L stainless steel and similar observations of Nitronic-40 and Tenelon demonstrate that parting is possible in austenitic steels under some circumstances.
Effect of Temperature on the Fracture Toughness Behavior of Inconel X-750
Authors: Mills WJ
Published: March 2009

The elastic-plastic J1c fracture toughness response of precipitation heat-treated Inconel X-750 was evaluated by the multispecimen resistance-curve (R-curve) technique at room temperature and elevated temperatures. The fracture toughness of this nickel-base superalloy was found to increase slightly under intermediate temperature conditions (427°C), but it decreased dramatically at the highest test temperature (649°C). Metallographic and electron fractographic examination of fracture surfaces revealed that the slight increase in J1c at intermediate temperatures was associated with an intergranular-to-transgranular fracture mechanism transition. At room temperature, crack extension occurred primarily by an intergranular dimple rupture mechanism attributed to microvoid coalescence along a grain-boundary denuded region. In the 427 to 538°C regime, the fracture surface was dominated by a transgranular morphology consisting of poorly defined dimples coupled with a rather flat, faceted appearance. At 649°C, intense heterogeneous slip initiated localized separation, which resulted in a very faceted fracture surface morphology and a severe degradation in fracture toughness.
Correlation of Fractographic and Microstructural Features
Authors: Steele JH
Published: March 2009

One of the most important aspects of fractographic analysis is the relationship between the fracture surface microtopography and the underlying microstructure. This type of correlation requires comparison of the size, shape, and spatial arrangement of both fractographic and microstructural features and identification of the specific microstructural features that adjoin the fracture surface. Two examples of qualitative fractographic-microstructural analyses conducted with a scanning electron microscope in ferrous alloys are presented. The first example involves brittle cracking of oriented Fe-3Si sheet during cold rolling and the second low tensile ductility in a hot-rolled 0.47C-1.6Mn steel.
Fractography of Laser Welds
Authors: Metzbower EA , Moon DW
Published: March 2009

A series of high-strength alloys has been laser-beam welded in thicknesses of up to 1.27 cm (0.5 in.). These welds in steels, a titanium alloy, and an aluminum alloy have been tested for their mechanical properties, fracture toughnesses, and hardness. The microstructures of these weldments have been determined in the base plate, heat-affected zone, and fusion area. The fractographic features for each alloy have been determined and correlated with the weldment's properties and structures.
Fractographic Characterization of the Effect of Inclusions on Fatigue Crack Propagation
Authors: Wilson AD
Published: March 2009

The fracture surfaces of fatigue crack propagation (FCP) test specimens of ASTM plate steel Grades A516-70, A533B-1, and A514F are characterized primarily by using the scanning electron microscope. The evaluation involved two plates of each grade with different inclusion structures. These had been produced by conventional steel-making techniques or by calcium treatment. The FCP tests were performed in the six possible testing orientations for each material and quality level. In each grade, the Type II manganese sulfide and alumina inclusions associated with the conventional quality plate resulted in faster FCP growth rates, particularly in the through-thickness testing orientations (S-T, S-L). Furthermore, the group nature of the occurrence of these inclusions was found to be the primary influence on FCP behavior. In addition, these inclusion formations were found to give greater anisotropy of FCP behavior for the steels of the higher yield strength, principally because of the fracture mode of the material between inclusions of a particular formation. For all steel grades, the calcium treatment led to improved levels and isotropy of FCP resistance.
Strength Characterization and Nature of Crack Propagation in Ceramic Materials
Authors: Govila RK , Beardmore P , Kinsman KR
Published: March 2009

A detailed study characterizing the strength and nature of crack propagation has been made in several high-temperature structural ceramics, namely, hot-pressed silicon nitride (Si3N4), Refel silicon carbide (SiC), sialons, and lithium-aluminum-silicate (LAS) glass ceramic. Fracture phenomenology was studied fractographically as a function of flaw size, temperature, and loading rate. The temperature dependence of the fracture behavior was evaluated using uncracked and precracked specimens.

All the materials showed the same general characteristics of temperature dependence of both the fracture stress and crack-growth phenomena. The only variation between the different materials was the temperature regime in which the differing phenomena occurred. Two mechanistic regimes were manifest in the temperature dependence of the fracture stress. A region of fast fracture (catastrophic crack extension) existed up to a certain temperature, in which the mode of crack propagation was primarily transgranular. Above this temperature, the strength (fracture stress) decreased considerably due to the presence of subcritical or slow crack growth (SCG) prior to the final catastrophic fracture, and the extent of SCG increased with increasing temperature. Slow crack growth is a result of microplastic deformation, which occurred by grain-boundary sliding and grain separation, and the mode of crack propagation is exclusively intergranular.

The influence of the loading rate on SCG and fracture stress was investigated. Generally, at a given temperature, the extent of SCG decreased with increasing loading rate until, at a sufficiently high rate, catastrophic fracture occurred directly from the initial crack with no slow crack extension. Directly analogous observations were made in stress-rupture studies in which the extent of SCG decreased with increasing stress level.
Fractographic Analysis of Delayed Failure in Ceramics
Authors: Mecholsky JJ , Freiman SW
Published: March 2009

Fracture surfaces of bars of glass and ceramics that failed after time under constant load were compared with those generated in rapid failure experiments. For each material, the relationship between the fracture stress, σ, and the fracture mirror radii, rj (σrj1/2 = a constant), was the same for rapid and delayed failure. The ratio of the mirror radius to the critical flaw size for delayed failure is a constant equal to that found previously for rapid failure. However, the ratio of the fractured mirror radius to the initial flaw size increased with increasing time under load due to the growth of the fracture-initiating flaw from the original size to the “critical” size before catastrophic failure. Slow crack growth in several polycrystalline ceramics occurred primarily by intergranular fracture, whereas primarily transgranular fracture occurred during rapid crack propagation. Thus, the boundary between subcritical and catastrophic flaw growth can be quite distinct. The fracture mechanics analysis presented in this paper relates the time under load to the ratio of the mirror and the initial flaw dimensions. This analysis gives good agreement with most experimental observations.
Multiple-Mist Regions on Glass Fracture Surfaces
Authors: Abdel-Latif AIA , Bradt RC , Tressler RE
Published: March 2009

Observations of the formation of multiple-mist regions on the fracture surfaces of soda-lime-silicate and fused silica glasses are reported. These regions occur only in high-strength specimens. The same empirical equation that is applicable to the basic fracture mirror-primary mist also describes secondary and tertiary mist regions, although the proportionality constants increase as the order of the mist region increases. Results suggest that these mist radii constants may be related in specific ratios, which decrease with successive mist regions. Criteria of mist-region formation are reviewed with respect to additional restrictions imposed by the consideration of multiple mists. The authors suggest that an energy criterion is most applicable, and a schematic diagram is proposed.
Localized Deformation and Fracture of Magnesium Oxide
Authors: Adler WF , James TW
Published: March 2009

Particulate erosion of brittle materials is a complex process of fracture nucleation, growth, and interaction which leads to removal of material from the exposed surface. The temporal and spatial development of the localized pressure loading imparted to a material surface by a water-drop or soft-body collision is not clearly defined. For the impact conditions investigated, the duration of the applied pressure pulse is generally less than 100 ns. Correspondingly, the exact form of the transient stress states generated within the impacted body is not easily determined. However, insights into the nature of the damage produced by these relatively short stress cycles are being obtained from microscope examinations of the residual deformation and fracture patterns in transparent materials. The response of single crystals of magnesium oxide to water-drop collisions is described. It was found that for the high strain rates imposed slip and fracture occur in the same systems and planes as are associated with quasi-static deformations. However, water-drop impacts produce slip only on the four {110}45-deg slip systems, whereas rounded solid particles produce dominant slip on two {110} 90-deg slip systems, as well as on the {110} 45-deg slip systems. The fractures associated with each condition are also distinctly different. It was also found that fracture initiation could be suppressed with the introduction of numerous active slip sources on the impact face of the crystal.
Fracture of Tungsten Wire in Metal Matrix Composites
Authors: Kim C , Phillips WL , Weimer RJ
Published: March 2009

Mechanical properties were measured for the tungsten-fiber-reinforced Type 6061 aluminum and Type 1010 steel matrix composite systems. The tensile strength of the latter system was appreciably lower than the theoretical rule-of-mixture value. Auger spectroscopy and electron microprobe analysis showed significant iron contamination in the tungsten fibers. In addition, the tensile fracture mode at room temperature was shown to change from ductile to completely brittle upon annealing at 800 to 950°C, that is, just slightly above the fabrication temperature. Quantitative microanalysis showed that penetration of the iron diffusion front into the tungsten fiber coincided exactly with an annular fracture feature observed by scanning electron microscopy of tensile fracture surfaces. The strength degradation in steel/tungsten composites was due to fiber embrittlement caused partly by microstructural polygonization during the recovery process, but primarily by grain boundary diffusion of elemental iron from the steel matrix.
Fourier Transform Techniques—Fracture and Fatigue
Authors: Passoja DE , Psioda JA
Published: March 2009

Real-time analysis of the fatigue crack growth process has been achieved by means of phase-sensitive signal detection methods used in conjunction with spectrum analysis. During crack growth, modulations of the displacement signal occur as a result of the crack's interaction with the microstructure. It was found that the character of the modulation signals was not random but periodic. Utilization of quantitative fractographic and Fourier transform techniques facilitated the formulation of the relationships existing between the microstructure and the signals measured during fatigue crack growth testing. There is a direct correspondence between the Fourier spectrum of the crack profile and the Fourier spectrum of the displacement modulations; the space-time correspondence between the test and the fracture surface was established by the determination of the microscopic fatigue crack velocity. The spectra of the fracture surface and the displacement modulations arise from secondary cracking along second-phase particles in the Type 7075-T6 alloy that was studied.
Application of Load Pulsing to the Fractographic Study of Stress-Corrosion Cracking of Austenitic Stainless Steels
Authors: Hahn MT , Pugh EN
Published: March 2009

A study has been made of stress-corrosion fracture surfaces produced in a Type 310S and a Type 304 steel tested in boiling aqueous magnesium chloride (154°C). During cracking, small load pulses were periodically superimposed onto an otherwise constant load, and, in the case of transgranular cracking, these produced markings on the fracture surfaces that delineated the instantaneous position of the crack front. A one-to-one correspondence was observed between these crack-front markings and the number of load pulses for time intervals between pulses exceeding 15 s. For smaller intervals, there were fewer markings than pulses. Moreover, the distance between the markings did not decrease to zero as the intervals decreased below 15 s but attained an approximately constant value. These observations are considered to indicate that transgranular cracking is a discontinuous process and that crack advance involves brittle mechanical fracture. No crack-front markings were detected on intergranular stress-corrosion surfaces, presumably because the crack tip is normally blunt in this case. The authors suggest that intergranular stress-corrosion cracking in this system occurs by continuous anodic dissolution at the crack tip, probably by the film-rupture model.
An Evaluation of the Round Compact Specimen for Fatigue Crack Growth Rate Testing
Authors: James LA , Mills WJ
Published: March 2009

A proposed round compact specimen was evaluated for its suitability for fatigue crack growth rate testing. The results were compared with results from standard compact specimens [per ASTM Tentative Test Method for Constant-Load-Amplitude Fatigue Crack Growth Rates Above 10−8 m/Cycle (E 647-78 T)], and the two specimens were found to yield equivalent results. A number of K-solutions have also been proposed for the round compact specimens, and these are reviewed. The agreement between the various solutions was quite good, and the Newman Equation was used to evaluate the present results.
Detecting Acoustic Emission During Cyclic Crack Growth in Simulated BWR Environment
Authors: Nakajima H , Shoji T , Kikuchi M , Niitsuma H , Shindo M
Published: March 2009

An attempt is made to detect and analyze acoustic emissions from cyclic crack growth in SA 533 Grade B steel in the simulated boiling-water reactor (BWR) water environment. Significant levels of signals caused by the environment-enhanced crack growth were obtained through appropriate noise reduction techniques. By reducing the frictional noises between the loading pins and the specimen, and by characterizing the spectrum of signals emitted from various sources, discrete signal identification was made possible. From an empirical relationship between the energy of emission and the crack growth rate, the possibility of utilizing this type of acoustic emission technique was discussed in relation to future continuous monitoring of operating nuclear plants.
Statistical Analysis of Fatigue Crack Growth
Authors: Bastenaire F , Lieurade H-P , Régnier L , Truchon M
Published: March 2009

The object of this paper, which assumes the validity of Paris's equation, is to derive satisfactory estimates of the two constants C and m in the following conditions: (1) numerical process leading to the estimates of C and m is based on a rationale that takes into account the physical and statistical aspects of fatigue crack growth, and (2) the result of the fit compares favorably with existing procedures.
Effect of Δa-Increment on Calculating da/dN from a versus N Data
Authors: Ostergaard DF , Thomas JR , Hillberry BM
Published: March 2009

Data from a previously reported study were analyzed to determine the effect of the Δa-increment on the error in calculating the fatigue crack growth rate from recorded a versus N data. The data had been recorded from 68 replicate fatigue crack growth tests on center crack panels of 2024-T3 aluminum alloy using a Δa-increment of 0.2 mm. Two different differentiation methods were considered, the secant method and the quadratic seven-point incremental polynomial method. The influence of the Δa-increment was determined by evaluating da/dN using all the data, every second, every fourth, every eighth, and every sixteenth data point. The minimum error for calculating da/dN was found to be for Δa between 0.8 and 1.6 mm. An evaluation of the type of distribution for da/dN showed that of the five distributions considered no single distribution adequately represented all da/dN regardless of the Δa-increment.
An Analysis of Several Fatigue Crack Growth Rate (FCGR) Descriptions
Authors: Miller MS , Gallagher JP
Published: March 2009

This report presents the results of a round-robin life-prediction effort conducted by ASTM Task Group E24.04.04 on FCGR Descriptions. The fatigue crack growth rate (FCGR) data supplied to the task group participants for description purposes are provided along with the definition of the life-prediction effort and results. It is shown that the majority of the participants could describe the FCGR data well enough that the resulting constant amplitude life predictions were within ±20 percent of the test lives for more than 80 percent of the tests.
A Practical Probabilistic Method for Evaluating the Fail-Safeness of Structures that May Fail Due to Fatigue
Authors: Gebman JR , Paris PC
Published: March 2009

The undetected propagation of a fatigue crack constitutes a significant cause of aircraft and other structural failures. To raise the structural failure load to a relatively high level, the manufacturer can divide the structure into many small elements, which significantly increases the ability of a structure to tolerate an element failure. This paper presents a procedure for calculating the probability that the structure has not failed, as the function of the crack propagation history for an undetected fatigue crack. The form of the procedure is so simple that computations with a desk calculator can yield reasonably accurate results. Moreover, the necessary input data are often readily available. By adopting such a procedure, aircraft manufacturers and operators can better identify those elements that pose the greatest threat to structural integrity.
A Nondestructive Method of Evaluating Adhesive Bond Strength in Fiberglass Reinforced Plastic Assemblies
Authors: Chapman GB
Published: March 2009

Two parameters used to quantify the nondestructive inspection (NDI) of adhesive lap-joint bonds are useful as reliable indicators of adhesive bond strength in certain inspection applications. The two indicators, local bond integrity index (LBI) and bond merit factor (BMF), will be defined and their relationships to bond strength demonstrated and discussed.

The LBI indicator is obtained from readings of local bond integrity made with a commercially available bond tester. The readings were made on local bond regions approximately 2.5 cm2, with a bond tester that had been calibrated to a desired sensitivity by using an appropriate reference specimen. The reference specimen was selected by a simple statistical and physical test procedure, and its use provides a reproducible relationship between LBI and bond strength. Destructive test results have shown good correlations (r = 0.9) of lap-shear strength with LBI readings for a given sample set.

The BMF indicator is an easy-to-obtain, time-efficient indicator of adhesive bond coverage. It is computed for a bond line region, generally 15 to 40 cm long, using disbond detection data obtained for instrument sensitivity based on the LBI of the reference specimen. These regional inspection results have shown fair correlation (r = 0.7) with the sum of local lap-shear strengths over the region.
Analysis of the “Joggle-Lap” Joint for Automotive Applications
Authors: Givler RC , Pipes RB
Published: March 2009

An analytical model was developed to describe the response of the “joggle-lap” joint to tensile loads. The model consisted of a combination of Euler, curved, and layered beam analysis which calculated stress profiles through the adherend thickness. A plane stress finite-element model was incorporated into the analysis to correctly determine the stress field in the adhesive zone where it was shown that beam analysis was less accurate. Elastic response of the “joggle-lap” joint due to tensile loads was verified through experimental testing, and ultimate loads were accurately predicted within experimental error. Maximum adherend flexural stress was found to determine joint failure. Fracture locations occurred within the adherend, outside the adhesive zone, primarily due to joint geometry.
Estimating the Acute Toxicity of Narcotic Industrial Chemicals to Fathead Minnows
Authors: Veith GD , Call DJ , Brooke LT
Published: March 2009

The overwhelming number of industrial chemicals either in commerce or in development precludes actual toxicity testing of each chemical and creates a need for initial screening techniques to focus efforts on those chemicals with the greatest potential for adverse environmental effects. One promising screening technique is the use of the structure-activity relationship to estimate aquatic toxicity from chemical structure.

Using five major classes of industrial chemicals from the Toxic Substances Control Act (TSCA) inventory, this paper presents a structure-activity relationship between the 96-h LC50 with fathead minnows and the n-octanol/water partition coefficient which can be computed from structure. Common industrial alcohols, ketones, alkyl halides, ethers, and benzenes are shown to cause lethality by the same mode of action of narcosis. Consequently, a single bilinear equation can predict adequately the 96-h LC50 of all classes of industrial chemicals to fathead minnows.
Environmental Influence on the Response of Aquatic Laboratory Ecosystems to a Toxicant
Authors: Woltering DM
Published: March 2009

The influence of prevailing environmental conditions on population and community responses to chronic toxicant perturbation was addressed in a 36-month laboratory ecosystem study. A series of 16 aquatic communities incorporating guppy, amphipod, snail, planaria, algal, and microbial populations were established in 750-L (200-gal) fiberglass tanks and were monitored monthly for changes in population biomasses. The environmental variables were the exploitation levels of the fish populations and the energy input and habitat availability. The development and resultant near steady states of the predator, prey, and competitor populations were presented graphically using phase plane analysis. Both the density-dependent and the time-dependent responses of the laboratory ecosystems to “established” sublethal dieldrin exposure varied according to the prevailing levels of environmental conditions. The ecologically different outcomes ranged from substantial perturbation, including mortalities but with eventual recovery to the preexposure population densities and community structure, to the extinction of a major population as a result of sublethal effects.