bluuebunny/crossref_metadata_2025 huggingface dataset:
Frequency Effects on Flawed-Composite Fatigue Reliability
Authors: Reifsnider KL , Stinchomb WW , Williams RS , Turgay HM
Published: March 2009

Variations in the degradation and subsequent fatigue reliability of laminated composite plate specimens with a center hole due to changes in cycle frequency have been identified and investigated. Boron-epoxy and boron-aluminum specimens were examined, principally for stiffness and strength variations. Various combinations of stiffness and strength changes were observed as a function of cycle frequency and specimen material, including a mode wherein stiffness decreased significantly while residual strength increased. A kinetic damage model was developed and combined with a Weibull extreme value expression to attempt to represent the stochastic aspects of the fatigue process. The model shows some promise, especially from the standpoint of representing widely varying fatigue behavior, including the unusual situation of stiffness drop with strength increase. Frequency dependence is included in the model.
Some Observations on the Dynamic Fracture Behavior of Carbon Fiber-strengthened Epoxy Resin
Authors: Beaumont PWR , Server WL
Published: March 2009

The dynamic fracture behavior of 0/90 carbon fiber-strengthened epoxy resin composites is described in terms of the dynamic fracture toughness parameters KId and GId as a function of temperature and strain rate. It is shown that the fracture toughness is dependent on the elastic characteristics of the fibers and is insensitive to strain rate and temperature. The crack propagation energy is controlled by the properties of the epoxy resin and fiber-matrix interface and is sensitive to changes in strain rate at elevated temperatures.
Molecular Correlations with Fracture in Fibers and Granular-Filled Composites
Authors: DeVries KL , Lloyd BA , Wilde TB
Published: March 2009

Failure in polymeric materials might be envisioned as occurring by any of several molecular mechanisms. Where homolytic bond rupture occurs, free radicals (unpaired electrons) result. This paper presents results of electron spin resonance studies of chain-scission kinetics in (1) oriented nylon fibers and (2) in granular-filled elastomer composites.

The most extensive work to date has been done on high-strength oriented fibers. It has been concluded that many of the desirable properties of fibers can be attributed to their own microscopic physical composite nature. A reaction-rate molecular model is proposed and is successfully used as a failure criterion to predict failure under various loadings.

The model assumes a statistical distribution in stress on the polymeric chain structure. Failure first occurs in the more highly stressed regions with a subsequent redistribution of the load among the unfractured elements in the fiber. Once the physical parameters are determined for a given material, behavior for other loading is predicted by numerical techniques. Electron spin resonance was used also to investigate interfacial failure in filled composites. Depending on the magnitude of the interactive forces, failure at the interface between the filler and the matrix may be largely adhesive (dewetting) or cohesive in nature. In the former case little or no detectable bond rupture occurs while in the latter case significant free radical concentrations may be produced. Electron spin resonance and scanning electron microscopy are used to systematically investigate the role of the surface interaction, dewetting, etc. on the strength and toughness of composites.
Fracture Behavior of Unidirectionally Solidified Ti-Ti5Ge3 Eutectic Composites
Authors: Yue AS , Kaba BT
Published: March 2009

A titanium-21 weight percent germanium eutectic alloy was unidirectionally solidified at two different rates to produce a composite material strengthened by intermetallic Ti5Ge3 fibers. The higher solidification rate produced a composite with fibers of finer diameters. The fracture behavior of this material was determined from work of fracture and impact experiments. A brittle-to-ductile transition was found, through the work of fracture experiments, to be 1150°F (621 °C). This transition was raised by some 450°F (232°C) under impact loading. The large increase in the work of fracture corresponding to this transition has been attributed to the increased ductility of the titanium matrix. It was also found in this experiment that the composite with larger fiber diameters was tougher than that with smaller fiber diameters. Macroscopic and microscopic observation of the fracture surface revealed that failure occurred in a brittle fashion below 800°F (427°C) and by normal rupture between 800 and 1200°F (427 and 649°C).
Fracture Behavior of Thornel 300/5208 Graphite-Epoxy Laminates—Part 1: Unnotched Laminates
Authors: Sendeckyj GP , Richardson MD , Pappas JE
Published: March 2009

Basic stress-strain and strength data generated as part of a systematic investigation of the fracture behavior of 8-ply Thornel 300/5208 graphite-epoxy laminates are compared with theoretically predicted response curves based on single-ply stress-strain curves. Results are given for (±θ)2s, (0/±θ/0)s, (90/±θ/90)s, (0/±45/90)s, and (90/±45/0)s laminates where θ = 0, 15, 30, 45, 60, 75, and 90 deg.
Fatigue, Creep, and Impact Resistance of Aramid Fiber Reinforced Composites
Authors: Miner LH , Wolffe RA , Zweben CH
Published: March 2009

Kevlar® 49 a high-strength, high-modulus, low-density organic fiber has gained significant acceptance as a weight-reducing replacement for E-glass in aircraft applications and for S-glass in filament-wound missile components. New end-use applications require a better understanding of the static and dynamic fatigue and impact resistance of these composites. The tension-tension fatigue life of both unidirectional fiber and fabric-reinforced laminates was greater than that of comparable glass-reinforced composites. The creep rate under continuous tensile stress was comparable to that of glass composites. The ball-drop impact resistance of Kevlar 49 fabric laminate-faced sandwich panels was dependent on fabric weave construction and number of face sheet plies. This relationship was significantly different for sandwich beams having glass-reinforced facings.
Properties of Filamentary-Reinforced Composites at Cryogenic Temperatures
Authors: Kasen MB
Published: March 2009

This paper presents a review of a series of significant publications on the mechanical and thermal properties of filamentary-reinforced structural composites in the cryogenic temperature range. The objective, scope of work, and significant conclusions of the selected works are discussed. The temperature dependence of the ultimate tensile strength, tensile modulus, thermal conductivity, and thermal contraction (expansion) is presented for selected composites developed in each program. Problem areas are defined and suggestions are made for future work.
Tensile Properties of an Ultrahigh-Strength Graphite Fiber in an Epoxy Matrix
Authors: Chiao TT , Hamstad MA , Jessop ES
Published: March 2009

The fiber performance and potential as a reinforcement for fiber composites of a special PAN-based graphite fiber were evaluated by testing the fiber's tensile properties in an epoxy matrix. Representative strand samples were taken from 30 spools (∼4 kg) of single-end, 1500-filament fiber to make over 5000 fiber-epoxy strand specimens using the filament-winding process. Characteristics studied were fiber uniformity, strength and modulus distributions at room and liquid nitrogen temperatures, stress-strain behavior, the effect of strain rate on fiber strength, and acoustic emission during tensile loading to failure. The fiber was found to have a 3570-MPa (517 ksi) failure stress, a 1.7 percent failure strain, a 206-GPa (30 × 106 psi) modulus, and a density of 1.77 Mg/m3 at 23 °C (73 °F). Liquid nitrogen temperature and various strain rates had no significant effect on fiber tensile properties.
Heat-Treatable Cladding for New Aluminum Alloy 7050-T76 Sheet
Authors: Staley JT
Published: March 2009

Four alloys were evaluated as candidates for a cladding on aluminum alloy 7050-T76 sheet. An alloy containing nominally 5 percent zinc, 1.2 percent magnesium, 0.1 percent zirconium, 0.1 percent maximum silicon, and 0.1 percent maximum iron, balance aluminum, provided good electrochemical protection to alloy 7050, and the composite of 7050-T76 clad with this alloy developed a useful combination of static and cyclic mechanical properties. Composites of 7050-T76 sheet clad with alloys containing higher amounts of zinc and magnesium developed comparable static mechanical properties and greater fatigue strengths, but were susceptible to stress-corrosion cracking of the cladding, and, consequently, are unacceptable.
Aggregates Manufactured from Waste Materials
Authors: Aleshin E , Bortz SA
Published: March 2009

Aggregates can be produced from diverse waste materials such as fly ash, waste clay, foundry effluent, phosphate slime, and municipal refuse. Finely divided particulates are characterized for the ability to form an aggregate using either a rotary kiln or traveling grate sintering machine. If the material does not possess the required characteristics for making an artificial aggregate, various additives can be used to upgrade the processing parameters. Residues from incineration of municipal refuse can be used either upon separation and classification, or after incineration. Qualities for a good concrete aggregate are strength, particle shape to promote good workability, low water absorption, and chemical and physical stability.
Qualification of Source Test Methods as Reference Methods
Authors: Howes JE , Pesut RN
Published: March 2009

Air pollution measurements require test methods that have a demonstrated capability to yield reliable data when the procedures are carried out by people with different backgrounds and experience. Collaborative testing can provide “real world” situations in which the performance of test methods can be evaluated and useful measures of the accuracy and precision of data obtained by a given method can be obtained. For methods designed to measure emissions from stationary sources, this form of round robin approach requires that the samples be collected on-site and simultaneously by the various teams involved. Laboratory analyses of the samples can then be performed on an individual basis. Statistical analysis of the collaborative test data from properly designed experiments should yield estimates of within-laboratory and between-laboratory precision and accuracy of the method under test. It should also be possible in some cases to separate the overall accuracy and precision into the individual components due to sampling techniques and laboratory analytical procedures.

This discussion is concerned with measurement methods for gaseous emissions from stationary sources. The circumstances and data cited are based on experience with the American Society for Testing and Materials Project Threshold test program. Collaborative testing of methods for sulfur oxides and nitrogen oxides is discussed specifically; however, the considerations involved with the experimental design, conduct of the testing, and data analysis are applicable to testing of other methods. Collaborative sampling was performed at both an oil- and coal-fired power station, a foundry, a cement plant, and using a pilot-plant furnace unit with gas and oil firing. Samples which were spiked with known amounts of the pollutant gases were included at the pilot plant site to provide a measure of the accuracy of the methods.

Sampling for sulfur oxides was accomplished by a continuous method in which the sulfur trioxide was condensed from the gas stream and the sulfur dioxide was absorbed and reacted with a hydrogen peroxide solution. Both sulfur oxides were then determined by the barium chloranilate method. The nitrogen oxides were samples by a “grab” technique in which an evacuated bulb was used to collect the gas sample. The nitrogen oxides were reacted with acidified hydrogen peroxide in the bulb, and then determined by the phenol disulfonic acid method.

Statistical analysis of the collaborative test data provides equations which express the accuracy and precision of the methods as functions of the gas concentration. Accuracy and precision of the analytical procedures also were measured from analyses of standard reference materials by the participating laboratories.
Statistical Implications of the Environmental Protection Agency Procedure for Evaluating the Accuracy of Sulfur Dioxide and Nitrogen Oxide Monitors of Stationary Sources
Authors: Reeves JB
Published: March 2009

The statistical parameter identified in the Federal Register for evaluating the accuracy of monitoring systems of sulfur dioxide (SO2) and nitrogen oxide (NOx) from stationary sources is the absolute value of the mean plus the 95 percent confidence interval for a set of test data. The test data are derived by differencing simultaneous measurements by the monitoring system and a reference method. The probability that a system will fail the evaluation is a function of the mean and standard deviation of the errors in the system, the mean and standard deviation of the errors in the reference method, the number of data points used in the evaluation, and the acceptance level. An equation defining the probability of rejection is derived, and curves are presented showing this probability when nine measurements are used in the evaluation. The influence of errors in the reference method on the probability of rejection are discussed. Data from the evaluation of SO2 and NOx monitors at a power plant are presented and discussed briefly.
Ultra Low-Level Calibration Gas Generation by Multistage Dilution Techniques
Authors: Lucero DP
Published: March 2009

More precise and accurate parts-per-billion level calibration gases are obtained dynamically from concentrated sources such as permeation tubes and pure pressurized gases. Calibration gas production is accomplished by multistage dilution steps, comprised of combinations of pneumatic and diffusion processes. Zero air is defined relative to an analyzer response including interferent molecular response. Dilution precision and stability can be obtained within ±1 percent over ±15°C variations with pneumatic/pneumatic and pneumatic/diffusion networks. Nitric oxide calibration gas is generated from a nitrogen dioxide permeation tube and a molybdenum converter. Dilution factors larger than one billion are obtained with multistage pneumatic/diffusion techniques. The parametric relationships at each dilution stage are defined and the theoretical performance limits of multistage dilution techniques established.
An Industrial Approach to Evaluating Environmental Safety of New Products
Authors: Kimerle RA , Levinskas GJ , Metcalf JS , Scharpf LG
Published: March 2009

A systematic approach is presented for evaluating the safety of new products to employees, customers, consumers, and the environment. Upon initiation of a project to commercialize a new product, a safety assessment schedule is prepared which considers physical and chemical properties, use patterns, environmental persistence, physical and biological accumulation potential, interaction with environmental components, and toxicity. Safety data are obtained in a logical scheme from simple screening to confirmative studies, thus enabling hazard evaluations to be made continuously during product development. Application and utility of this concept to assess aquatic safety is demonstrated using results from a current detergent builder program.
A Mechanical Toxicant Injector for Flow-Through Toxicity Tests
Authors: Ozburn GW , Smith AD
Published: March 2009

An injector is described for delivering a series of constant concentrations of toxicant in a flow-through toxicity test. The apparatus can be employed either as a single channel unit for use with a proportional diluter or as a multichannel injector for use with an equal-volume water delivery system. The multichannel approach is emphasized for pesticide addition because the test concentrations are independent of each other. This allows the establishment of an unlimited range of toxicant concentrations.

Water is passed through a series of buckets which are capable of downward vertical displacement. The dropping buckets operate a series of pipettes which introduce the toxicant material to the system. Each channel is calibrated independently by controlling the stroke distance of the pipette plunger. A return spring mechanism automatically reprimes the pipettes for the subsequent water cycle.

Although the system is suitable for toxicity tests employing freshwater diluent, the metal components of the injector may be susceptible to corrosion under saltwater conditions.
A Flow-Through System for Studying Interaction of Two Toxicants on Aquatic Organisms
Authors: Auwarter AG
Published: March 2009

An intermittent-flow, proportional diluter system has been designed for the study of synergistic and antagonistic effects of two toxicants on aquatic organisms. The system consists of two diluters mounted side by side, each of which produces three toxicant concentrations plus a solvent control. Below the diluters are two additional mixing, sample-splitting levels. The first divides each concentration of each toxicant into four equal volumes. The second consists of 16 compartments, each of which receives a measured volume from 1 of the 4 concentrations of each toxicant. This produces a 4 by 4 matrix of all 16 possible combinations. This final level also serves as a series of sample-replicating chambers from which the toxicant mixtures flow to 32 test aquaria.
Method for Assessing Additive Toxicity of Chemical Mixtures
Authors: Marking LL
Published: March 2009

Mixtures of chemicals or pesticides may produce unexpected effects; some are hazardous and some are beneficial. A method was divised in which individual toxic contributions of chemicals are summed, and the additive toxicity is defined by an index for two or more chemicals in combination. This linear index expresses the toxicity quantitatively: zero indicates simple additive toxicity, negative values indicate less than additive toxicity, and positive values indicate greater than additive toxicity. The significance of index values near zero is assessed by substituting values from the 95 percent confidence intervals into the formula to determine whether the range for the additive indices overlaps zero (simple additive toxicity). The range is derived by selecting values of the 95 percent confidence interval yielding the greatest deviation from the additive index.

Mixtures of malathion and Delnav were found to be extremely toxic, and the additive index for the mixture against rainbow trout (Salmo gairdneri) was 7.20; that is, highly synergistic. Mixtures of copper, zinc, and nickel were additive in toxicity to rainbow trout. Mixtures of commercial synergizers sulfoxide or piperonyl butoxide with rotenone produced greater than additive toxicity against rainbow trout (indices = +2.13 and 2.36).
Suitability of Sheepshead Minnows (Cyprinodon variegatus) for Life-Cycle Toxicity Tests
Authors: Hansen DJ , Parrish PR
Published: March 2009

Entire life-cycle toxicity tests are practical with sheepshead minnows, Cyprinodon variegatus. This is the only estuarine fish that has been utilized successfully in life-cycle toxicity tests, using methods formulated only since 1973. Salinity, temperature, and spawning requirements were determined, and initial life-cycle toxicity tests with endrin were conducted at the U.S. Environmental Protection Agency Gulf Breeze (Florida) Laboratory. Subsequent tests with heptachlor, carbofuran, methoxychlor, and malathion were conducted at Gulf Breeze or at EG&G, Bionomics. All studies confirmed the feasibility of using this estuarine fish for determining maximum acceptable toxicant concentrations and application factors. Results of our tests also corroborate data on application factors obtained in studies completed elsewhere with freshwater fishes and the same pesticides.
Utility of Toxicity Tests with Embryos and Fry of Fish in Evaluating Hazards Associated with the Chronic Toxicity of Chemicals to Fishes
Authors: Macek KJ , Sleight BH
Published: March 2009

The hypothesis that concentrations of toxicants safe to fish over their entire life cycle can be estimated from the results of continuous exposure of embryos and newly hatched fry has been examined critically in the light of recent data. The assumptions underlying the proposed hypothesis appear to be: (a) the chemical does not exhibit significant cumulative toxicity; (b) there is a single mode of action through which the effect of the chemical is manifested in a relatively short time frame; and (c) the effect is most severe on the critical life stages (that is, embryos and newly hatched fry), where parameters such as hatchability, survival, and growth can be measured readily.

The majority of available data indicate that the hypothesis is valid. In most cases, estimates of specific application factors derived from exposure of critical life stages reasonably approximate specific application factors empirically derived from chronic toxicity studies with much less cost, effort, and time required. Other data suggest that exposure of critical life stages of fish can indicate to the researcher certain of those chemicals for which the underlying assumptions are not valid and for which the hypothesis is not applicable. In all cases, estimates of specific application factors derived from critical life stage studies provide information equal or greater in predictive value than information derived from the use of an arbitrary general application factor.
An Evaluation of Fenitrothion Toxicity in Four Life Stages of Rainbow Trout, Salmo gairdneri
Authors: Klaverkamp JF , Duangsawasdi M , Macdonald WA , Majewski HS
Published: March 2009

Lethal and sublethal effects of fenitrothion, an organophosphate insecticide, were investigated in rainbow trout (Salmo gairdneri) embryos, sac fry, fingerlings, and adults. Embryos first exhibited cholinesterase activity 14 days before hatch. Embryos and sac fry at various ages subjected to 34 mg/litre fenitrothion for 24 h under static exposure conditions first exhibited mortality 6 days after hatch. A 24-h lethal concentration of 50 percent of organisms (LC50) of 3.4 mg/litre and a 96-h LC50 of 2.0 mg/litre were obtained using fingerlings exposed to fenitrothion in a flow-through system. Fingerlings surviving 96 h of exposure exhibited cholinesterase activities ranging from 13 to 25 percent of controls (brain) and 30 to 51 percent (skeletal muscle). Adult trout were monitored for electrocardiogram and respiratory responses to fenitrothion concentrations of 5.0, 1.0, and 0.5 mg/litre. At 5 mg/litre, heart rate decreased initially but recovered within 24 h. Cough frequency was directly related to fenitrothion concentration. Based on acute mortality tests, the embryological life stage was the least sensitive, the sac fry stage was intermediate, and the life stages of fingerlings and adults were the most sensitive. The sublethal responses, cholinesterase inhibition in fingerlings and the cough response in adult trout, were sensitive to 0.75 and 0.5 mg/litre fenitrothion.
Acute Toxicity to and Bioconcentration of Endosulfan by Estuarine Animals
Authors: Schimmel SC , Patrick> JM , Wilson AJ
Published: March 2009

Acute (96-h) flow-through toxicity tests with endosulfan (Thiodan) were conducted with several estuarine animals. The test species and their 96-h lethal concentration for 50 percent of the organisms (LC50) values were: pink shrimp (Penaeus duorarum), 0.04 μg/litre; grass shrimp (Palaemonetes pugio), 1.3 μg/litre; pinfish (Lagodon rhomboides), 0.3 μg/litre; spot (Leiostomus xanthurus), 0.09 μg/litre; and striped mullet (Mugil cephalus), 0.38 μg/litre. In a 56-day bioconcentration study (28-day uptake, 28-day depuration), striped mullet were exposed to 0.008 and 0.08 μg endosulfan/litre seawater. The two endosulfan isomers (endosulfan I and II) were rapidly metabolized to endosulfan sulfate; only trace amounts of each isomer were detected in edible tissue or offal of mullet exposed to 0.08 μg/litre (0.035 μg/litre measured) for 28 days. Maximum bioconcentration factors of endosulfan were 2249 in edible tissue and 2755 in whole-body analyses. After 48 h in pesticide-free seawater, endosulfan was not detected in the previously exposed mullet. Our studies suggest that endosulfan in the estuarine environment would be a hazard because of its acute toxicity and bioconcentration potential, but animals surviving exposure and moving to areas free of endosulfan would lose the chemical rapidly.
Comparison of Residual Strength of Composite and Metal Structures after Ballistic Damage
Authors: Suarez JA , Whiteside JB
Published: March 2009

The residual static and impact fracture strengths of boron/epoxy laminates were obtained from tests using .30 and .50-caliber AP and 23-mm API projectiles. These strengths were compared to the static fracture and impact fracture strengths of 6A1-4V titanium, 7075-T6 aluminum, and 2024-T81 aluminum. Results have shown that the boron/epoxy system possesses residual and impact fracture tension strengths as high or higher than those exhibited by metals of similar strength, when maximum structural damage envelopes are considered. All testing was performed using composite panel thicknesses and projectile diameters which resulted in thickness to diameter ratios in the range, 0.051 < T/D < 0.153.
Impact Strength and Toughness of Fiber Composite Materials
Authors: Broutman LJ , Rotem A
Published: March 2009

The drop weight impact energy for beam specimens has been studied using various unidirectional and cross-ply glass fiber laminates. The strength and impact energy of these laminates are strain rate sensitive. The orientation of the lamination planes with respect to the impact load (perpendicular or parallel) is important and determines the failure mode as well as the impact energy. Cross-ply laminates, although weaker than unidirectional laminates, provide the same impact energy absorption in flexure since the dominant failure mode is delamination between layers. Failure models are described to account for the differences in impact energy absorbed for the various composite structures which were tested.
Methods for Improving the Impact Resistance of Composite Materials
Authors: Beaumont PWR , Riewald PG , Zweben C
Published: March 2009

A three-phase program to improve the impact resistance of composite materials was undertaken. In the first phase, the Charpy impact test was investigated for its utility in characterizing impact performance. It was found that the results of the standard Charpy test can be misleading, but the addition of instrumentation to provide load and energy histories can make this test a useful one. The importance of differentiating between initiation energy and propagation energy is shown, and a new parameter (the “Ductility Index”) is proposed, along with maximum stress and total energy, as a useful measure for comparing impact behavior of materials.

The instrumented Charpy test was used to investigate impact behavior of unidirectional, epoxy-matrix composites reinforced with fibers of E-glass, Kevlar 49, and graphite. In addition, two unidirectional hybrid composite materials consisting of graphite and Kevlar 49 fibers in epoxy were investigated. Comparisons were made with quasi-static three-point bend tests. It was found that the hybrid materials had significantly higher impact energies, ductility indices, and maximum stresses than the all-graphite fiber material.

Impact behavior of [±45] graphite/epoxy and hybrid Kevlar 49-graphite/epoxy panels, representative of aircraft fuselage shear panels, was studied using a ball-drop test. Results indicate a significant improvement in impact resistance with hybrid construction.
Analysis of Impact Stresses in Composite Plates
Authors: Kubo JT , Nelson RB
Published: March 2009

In this paper an analytical study is presented of the two-dimensional response of an elastic laminated composite plate to an impact load applied to its surface. The surface load is arbitrarily distributed along the extent of the plate surface and varies sharply in time to model the impact loading. Each layer of the laminated plate is of arbitrary (constant) thickness with specified density and orthotropic material properties, with the material axes coincident with the plate axes.

The physical behavior of the plate is exactly represented along the extent of plate in the form of a Fourier series, and its behavior in the thickness direction is modeled by a sufficiently large number of generalized coordinates to capture quantitatively the propagation and dispersion of stress waves due to the surface impact, with emphasis directed to calculating stresses on laminate interfaces. This method of analysis results in a sequence of algebraic eigenvalue problems, the solutions of which are used to decouple the equations of motion into a large number of simple differential equations in time. This procedure is quite straightforward and computationally effective and may be used to study the impact problem for an arbitrarily laminated plate.

An isotropic plate with a specified surface impact loading is presented to indicate both the accuracy of the results obtained and the time domain for which they are valid. A two-layer boron-epoxy plate is examined in detail to indicate the quantity and quality of information which may be generated by this method for composite material structures in impact environments. The results for this problem also reveal potentially harmful effects which develop during impact.

Sufficient information is presented to permit an experimental verification of the results obtained, for regions of time where the magnitudes of the impact stresses are most critical to material integrity.
Fatigue Crack Propagation Behavior of the Ni-Ni3 Cb Eutectic Composite
Authors: Mills WJ , Hertzberg RW
Published: March 2009

Room temperature four-point-bending fatigue studies of the unidirectionally solidified Ni-Ni3Cb eutectic composite have been conducted to better understand fatigue behavior in composite materials. Fatigue crack propagation (FCP) data for this eutectic composite alloy revealed a power relationship between the stress intensity factor range and the crack growth rate from 10-7 to 10-4 in./ cycle. This application of fracture mechanics concepts to FCP data represents the first such reported information of its kind for eutectic composites. Fatigue behavior of this eutectic alloy was found to be sensitive to solidification parameters, thermal history, and the mean stress intensity level.

Metallographic and electron fractographic examination of the fatigue fracture revealed the FCP mechanism to be a function of the prevailing stress intensity factor at the crack tip with a fatigue fracture mechanism transition occurring between 5 × 10-6 and 1.5 × 10-5 in./cycle. At low growth rates, the Ni(γ) phase exhibited faceting indicative of Stage I propagation along active slip planes, while above 5 × 10-5 in./cycle, the γ fracture surface was characterized by the presence of fatigue striations which laid parallel to the Ni-Ni3Cb interface. At both high and low growth rates, the fatigue response of the Ni-Ni3Cb composite was controlled by the γ lamellae.
Fatigue Crack Growth in Dual Hardness Steel Armor
Authors: Kula EB , Anctil AA , Johnson HH
Published: March 2009

Crack growth tests under cyclic loading conditions were conducted on samples from different lots of dual hardness steel (DHS) armor. The results showed that the growth rate increased with stress level, and the cracks grew at a different rate in the frontal and backup layers of the armor. This difference in growth rate became progressively greater with increases in the stress level. The crack growth rate also increased with reductions in the frequency of loading and temperature increases over the range of -60 to +200°F.

Attempts are made to explain the crack growth behavior of the composite in terms of the behavior of each component. The growth rates in the composite are related to the stress intensity factor, ΔK, calculated from the surface crack length assuming that there was no interaction between the layers and the displacement in each layer was the same on the crack line. The latter procedure yielded better results and suggested that the interface plays an important role in retarding crack growth in the frontal layer of DHS.
Effects of Frequency on the Mechanical Response of Two Composite Materials to Fatigue Loads
Authors: Stinchcomb WW , Reifsnider KL , Marcus LA , Williams RS
Published: March 2009

A new class of mechanical response characteristics in composite materials is reported. These characteristics were found to come about because of a nonlinear dependence of the fatigue response of biasply boron-aluminum and boron-epoxy flawed plate specimens on the frequency of load (or strain) oscillation. This nonlinear frequency effect was found to alter such properties as fatigue strength, stiffness, residual strength, and energy dissipation by as much as an order of magnitude. Several conceptual interpretations are developed and compared with data correlations.
Axial Fatigue Properties of Metal Matrix Composites
Authors: Christian JL
Published: March 2009

Axial fatigue properties were determined on a number of filament reinforced metal matrix composite materials. Results indicated that each of the composite materials possessed excellent fatigue properties when tested parallel with reinforcing filaments (that is, fatigue strengths at 106 cycles of 50 to 80 percent of ultimate tensile strengths). Transverse fatigue properties were found to be similar to those of the unreinforced matrix material. The type and size of filaments and the matrix material and its condition were found to significantly affect fatigue properties. For example, boron-reinforced composites possess higher fatigue strengths than Borsic-reinforced composites at high-stress, low-cycle fatigue, but the reverse is true in the low-stress, high-cycle region; large diameter (5.6-mil) filaments impart superior fatigue properties to composites than do 4.0-mil fila- ments; aluminum matrix composites possess better fatigue properties in the longitudinal direction (that is, parallel with reinforcing filaments), however, titanium matrix composites possess higher fatigue strengths in off-axis directions; disbonds result in lower fatigue strengths; and, heat treatment of the matrix improves transverse fatigue properties but has little or no effect on longitudinal fatigue strength. The fatigue properties of boron 6061 aluminum, Borsic 6061 aluminum, boron stainless steel 6061 aluminum, Borsic stainless steel 6061 aluminum, Borsic titanium 6061 aluminum, and Borsic 6Al-4V titanium are presented and compared to facilitate use by design and materials engineers.
X-Ray Diffraction — A Versatile, Quantitative, and Rapid Technique of Metallography
Authors: Zwell L
Published: March 2009

X-ray diffraction is used to delineate the structure of materials, their chemical and phase analyses, grain and domain sizes, internal strain (stress), texture, imperfections, homogeneity, etc. In this paper, the practicality of the methods is emphasized; diffractometer techniques can be simple, quantitative, and rapid, and together with film techniques, permit examination of a wide range of materials. Examples are given of the characterization of structure by X-ray diffraction techniques and of the applications of the results in such different investigations as mechanical and physical properties of solid solutions, recrystallization of steel, pore structure of carbons, creep properties, surface stresses, and transformation of austenite to bainite.
Examination of Materials by Coherent Light Techniques
Authors: Schaefer RJ , Blodgett JA , Glicksman ME
Published: March 2009

The diffraction and interference of coherent light from lasers can be used to record and analyze metallographic structures. Optical transforms, holography, optical correlation, and other coherent light methods are presently being applied to materials problems ranging from basic research to testing and inspection. This paper describes the basic concepts used in some of these methods and describes examples of their application. Holography is a particularly attractive method for measuring changes in the shapes of objects, especially because it allows interferometric measurements without special surface preparation. The use of holography for studies of crystal growth and electropolishing is described in some detail, and reconstructed holograms are shown. Holography and other coherent light techniques can often reveal the presence of defects or inhomogeneities even when quantitative evaluation of the optical output is difficult.
The Electron Microprobe as a Metallographic Tool
Authors: Goldstein JI
Published: March 2009

The electron microprobe (EMP) is an electron optical instrument in which compositional and topographic information are obtained from regions ⩽1μm in diameter on a specimen. Photographs of compositional and topographic changes in 1-mm2to 20-μm2 areas on various types of specimens can also be obtained which are strikingly similar to optical photomicrographs. This paper discusses the various signals that are measured in the EMP (X-rays, secondary electrons, backscattered electrons, etc.), their resolution, and the types of information that can be obtained. In addition to elemental analysis, the solid state detector and scanning techniques will be discussed. The last sections will cover characterization of phases-homogeneity-trace element analysis-quantitative metallography and various techniques which extend the instrument capabilities such as deconvolution and soft X-ray analysis. Various applications will be discussed and illustrated.
Phase Separation as a Technique for the Characterization of Superalloys
Authors: Kriege OH
Published: March 2009

Specific anodic dissolution procedures are detailed for the quantitative separation of carbides, topologically close-packed (TCP) phases, and γ′ from high temperature nickel-base superalloys. Reagents are suggested for the isolation of phases from mixed anodic deposits through selective dissolution techniques. Methods for the chemical analysis of separated phases are discussed. The application of phase separation to specific metallurgical studies is described in detail.
Automation Trends
Authors: Frazer JW
Published: March 2009

There are many forces in the scientific community which are gradually encouraging changes in laboratory automation. These forces and some of the anticipated changes are discussed briefly. The main topic is the new evolving methodology that will be required to effectively implement the computer systems of the future. ASTM Committee E-31's contributions to the development of this methodology is discussed as a prelude to the other papers in the book.
Recommended Procedure for System Specification and Design: Automation of a Gas Chromatograph — Mass Spectrometer System
Authors: Perone SP , Ernst K , Brand HR , Frazer JW
Published: March 2009

Too often the development of laboratory automation systems has proceeded without adequate specifications or design. It is not unusual to find systems which are orders of magnitude too powerful—or, conversely, grossly inadequate—for the automation tasks required. A typical pitfall involves the specification of computer hardware independent of any detailed consideration of the real requirements of the laboratory instrumentation. Presented here will be an outline of a recommended approach to laboratory automation design. This approach recognizes three steps in the development of an automation system: user-level specifications of objectives and constraints; preparation of a hardware-independent functional design; and implementation of the design with specific hardware/software components. Thus, the selection of system components is not made until after the functional characteristics of the system are defined. At this point, hardware/software tradeoffs can take place to achieve an optimum configuration. A specific example will be discussed here to illustrate this approach. The example involves the development of a computer-automated gas chromatograph-mass spectrometer laboratory instrument for nonroutine analytical investigations.
The Need for Automated System Specifications and Designs
Authors: Frazer JW , Kray AM , Boyle WG , Morris WF , Fisher ER
Published: March 2009

The development of system specifications and functional and implementation designs for one chemistry system at the National Environmental Research Center in Cincinnati is discussed. Technical details are presented to illustrate the form and context of these three phases of the laboratory automation project. The principles used for this work are the same as those being followed by ASTM Committee E-31 in the development of “guidelines and recommended practices.”
Development of a Computerized Laboratory System
Authors: Lothrop EW Jr , Starr SS
Published: March 2009

Our experience in the integration of a computer into the regular daily operation of a conventional, research and development, physical properties laboratory is described— from the conception of the idea through planning, design, implementation, and startup to on-line operation. Development of the system paralleled closely the guidelines currently being formulated by ASTM Committee E-31 on Computerized Laboratory Systems. Detailed considerations of laboratory objectives and computer capabilities resulted in the design of a system based on a minicomputer. The system has the flexibility to handle various types of laboratory instruments within the design limits of data acquisition rate, storage capacity, and analysis program size. Experience has shown that the computerization of the laboratory has been readily accepted by both professional scientists and laboratory technicians, test results are more accurate, consistent, and error-free, costs to acquire the same type test results as were previously obtained are lower, and additional useful data may be acquired from each test without incurring additional costs.
An Automated Remote Marshland Water Sampling Station
Authors: Thomas DF
Published: March 2009

In cooperation with the Virginia Institute of Marine Sciences, NASA-Langley Research Center has developed a water sampling station for use in remote tidal marshlands. This paper presents the results of this effort including recommendations pertinent to the use of the station and fabrication of additional stations.
Monitoring of Wastewater Discharges Aboard Navy Ships
Authors: Talts A , van Hees W
Published: March 2009

The U.S. Navy has taken an early initiative in bringing about the development of shipboard wastewater treatment systems. Liquid wastes generated aboard Navy ships originate from man related activities (sanitary and “hotel” wastes) as well as industrial activities associated with the particular mission of any ship.

This paper discusses the problems encountered in the characterization of aqueous waste streams, other than bilge and ballast waters, that are generated on Navy ships. Monitoring methodology is discussed in terms of quantitative assessment of potential waste sources, the selection of flow monitoring methods, sampling procedures, shipboard constraints on analytical methods, and data collection. Waste flow profiles have been determined for major shipboard contributors. A pragmatic approach of hardware applications and survey procedures was employed under unique circumstances. These are discussed in light of the practical application of such acquired information in the development of the most practicable wastewater management systems for Navy ships.
Continuous Liquid-Liquid Extraction of Organic Pesticides from Aqueous Solutions
Authors: Wu C , Suffet IH
Published: March 2009

Liquid-liquid extraction (LLE) is considered by most residue analysts to be the best method for quantitative recovery of organic pesticides from aqueous solutions. Continuous liquid-liquid extraction is a logical extension of the process. This paper reviews the LLE process especially the alternative of continuous LLE for the isolation of organic pesticides from aqueous solutions. Trends and user problems are noted.

A continuous liquid-liquid extraction apparatus with capabilities for continuous solvent recycling and sample enrichment is described. The principal parts of this design are a helix Teflon coil mixing chamber, a column phase-separator, and an evaporative concentrator.

Initial experiments were made to evaluate the design. Extraction efficiencies ranging from 85 to 93 percent were obtained for five organophosphate pesticides extracted from water with benzene under the optimized conditions of coil length, helix diameter, flow rate, and water to solvent ratio.

The apparatus is simple and economic to build. It is contamination-free as all parts in contact with water and solvent are made either of Teflon or glass. Complete automation of this apparatus is possible by adding liquid-level controllers, solenoid valves, and electronic relay systems.
A Monitor for the Continuous Measurement of Suspended Solids in Liquids
Authors: Liskowitz JW , Richardson ASC
Published: March 2009

A development suspended solids monitor based on measurement of the depolarization of backscattered polarized light has been designed and constructed. Limited field testing indicates that this monitor when submerged in a waste stream can continuously monitor the suspended solids concentration under a variety of conditions.
Influences of Chemical and Thermal Environments on Delay in a Ti-6Al-4V Alloy
Authors: Shih TT , Wei RP
Published: March 2009

The influences of chemical and thermal environments on delay in fatigue crack growth under elemental load spectra were examined for a mill-annealed Ti-6Al-4V alloy. The results indicate that delay is significantly affected by the hold time at high load in 3.5 percent NaCl solution at room temperature, and by both temperature and thermal history. In 3.5 percent NaCl solution, delay may be increased by 40 times through increasing the hold time from zero to 900 s, the specific amount depends on the overload ratio (Khmax/Kℓmax) and the maximum value of the low-amplitude fatigue load (or Kℓmax. Delay is generally higher at the higher test temperature (560°F or 293°C), although the trend in behavior associated with changes in loading variables is similar to that observed at room temperature. Delay is significantly increased when the high load is applied at a high temperature, with subsequent fatigue at room temperature. It is reduced by intermediate heating at a high temperature following a high-load excursion at room temperature, and is lowest when fatigue loads are applied at high temperature following a high-load excursion at room temperature. The significance of these results in terms of modeling and life prediction procedures is discussed.
Effect of Various Programmed Overloads on the Threshold for High-Frequency Fatigue Crack Growth
Authors: Hopkins SW , Rau CA , Leverant GR , Yuen A
Published: March 2009

A threshold value of crack tip stress intensity range (ΔKth) exists below which Mode I cracks do not propagate in high-frequency fatigue. The response of ΔKth, in a commercial nickel-base and titanium-base alloy, to single and multiple cycle overloads (that is, the behavior of an overload modified threshold, ΔKth*) has been defined for a variety of fatigue conditions. Both alloys responded similarly and showed an exponential increase of ΔKth* with increased magnitude of the overload. The effects of overload rate, temperature, cycle shape and number, and the fatigue conditions of mean stress and cyclic frequency have lesser, but significant, effects on ΔKth*. Metallography and scanning electron fractography have been used to define the changes in crack size and tip shape which contribute to the overload effects.