bluuebunny/crossref_metadata_2025 huggingface dataset:
Application and Description of a Portable Calibration System
Authors: Debbrecht FJ , Neel EM
Published: March 2009

A newly introduced calibration system for air pollution monitors and its field use will be discussed. The system is based upon the Environmental Protection Agency's developed permeation tube technique and is fully portable, allowing intercalibration of monitors at different locations.

Two major requirements are necessary for accurate use of permeation tubes in the generation of primary standard quality calibration gas mixtures. The temperature of the permeation tube must be held within 0.1°C of the temperature at which it was calibrated to ensure accuracy within 1 percent. Also the flow rate of the gas across the permeation tube must be readable to within 1 percent accuracy.

The portable calibration system described controls the permeation tube at 35°C to well within 0.1°C. This temperature is fixed and is read out on the expanded scalemeter that is 0.4°C full scale to ensure that the permeation tube is within 0.1°C of the fixed 35°C.

The calibration system draws in ambient air through a particulate filter by an internal dual headed pump. One head provides a flow of 10 ml/min through a restriction, a charcoal scrubber, the permeation chamber, and a flow directional valve. The other head provides a diluent flow, settleable on the front panel, from 300 to 1500 ml/min. This flow is read out on a special dual ball rotameter, individually calibrated, with settleability to within 1 percent. This diluent flow can provide a fivefold change in concentration available for calibration, permitting calibration at a number of points. In addition the flow direction valve has a high concentration position in which all of the permeation effluent is mixed with the diluent air, a low concentration position in which only 20 percent of the permeation effluent is mixed with the diluent air, and a “zero” air position in which no permeation effluent is used. This last position provides only air that has passed the charcoal scrubber for the analyzer to be calibrated. The high/low concentration positions provide a 5 to 1 concentration range and when coupled with the diluent air flow range provide a 25 to 1 concentration range.

This calibration system can operate for at least 8 h from internal batteries, indefinitely from 110 V lines, while the batteries are recharging, or from an auto cigarette lighter adapter supplied as standard.

The present emphasis and concern on data correlation among the various locations and agencies involved in the air pollution effort requires the instrumentation used to be calibrated properly. A portable calibration system provides the necessary common demoninator between a number of remote monitoring systems. This common standardization is the first crucial step before data can be compared.
Certification Experience with Extractive Emission Monitoring Systems
Authors: Bonam WL , Fuller WF
Published: March 2009

The relative influences of the absolute mean value error, the confidence interval value, and the instrument calibration accuracy is examined using on-site instrument certification data acquired in the past three years. Confidence interval has strong influence based on existing certification data. The trend emphasizes the importance of the sampling technique. Properly calibrated instruments provide low values of absolute mean value error. An induced error related to calibrating instruments to 1.5 times the applicable emission standard for full scale has been observed when the relative mean value (reference average of sampling values) is low. The effect of the induced error will be amplified when the instrument calibration is performed improperly. Extractive emission monitoring systems using ultraviolet visible absorption detection techniques have successfully met the performance criteria proposed by the Environmental Protection Agency based on evaluations conducted in power plants, nitric acid plants, and sulfuric acid plants.
Interagency Comparison of lodometric Methods for Ozone Determination
Authors: DeMore WB , Romanovsky JC , Feldstein M , Hamming WJ , Mueller PK
Published: March 2009

In 1973 it was learned that measurements of oxidants by the Los Angeles Air Pollution Control District (LAAPCD) were about 30 percent lower than measurements by the California Air Resources Board (ARB) and that the discrepancy was due to differences in the calibration methods of the two agencies. To resolve this problem, the ARB appointed an Oxidant Calibration Committee for the purpose of evaluating the accuracy of the different agency calibration procedures.

The committee selected ultraviolet absorption photometry as the reference method for ozone measurement. Interagency comparisons of the various iodometric methods were conducted relative to the ultraviolet standard. The tests included versions of the iodometric methods as employed by ARB, LAAPCD, and the Environmental Protection Agency (EPA). An alternative candidate reference method for ozone measurement, gas phase titration, was also included in the test series.

Under the conditions of these tests, which were considered to be representative of procedures employed by the California agencies, the ARB method read high by 25 to 30 percent, and the LAAPCD method read low by about 4 percent. The EPA method, which is similar to the ARB method, also read high. The gas phase titration results were about 9 percent higher than the reference ultraviolet standard.

Based on the results of these tests and other considerations, the committee has recommended that future ozone calibration procedures in the State of California be referenced to an ultraviolet standard.
Evaluation and Collaborative Testing of a Continuous Colorimetric Method for Measurement of Nitrogen Dioxide in Ambient Air
Authors: Margeson JH , Fuerst RG , Constant PC , Sharp MC , Scheil GW
Published: March 2009

A continuous colorimetric method for measurement of nitrogen dioxide (NO2) in ambient air, which uses Saltzman type absorbing solutions, was evaluated and then subjected to a collaborative test.

The evaluation shows that dynamic calibration is required to obtain reliable results. Static calibration is not reliable. The method write-up specifies dynamic calibration.

The collaborative test was carried out by having ten collaborators sample ambient air and the same ambient air spiked with a reliable source of NO2 for four days at a common site in Kansas City, Missouri; NO2 concentrations of 50 to 370 μg/m3 were sampled.

The results show that, based on 1-h avg concentrations, the within-laboratory standard deviation is 6 percent of the concentration over the range 90 to 370-μg NO2/m3, and the between-laboratory standard deviation is 14 percent of the concentration over the same range. The results also show that the method has a significant positive bias. This bias cannot be accurately quantitated because different collaborators give widely different biases, that is, the bias is collaborator dependent. The “average” bias ranges from +3 to +15 percent of the NO2 concentration over the just mentioned range.

The lower detectable limit of the method is 19 μg/m3.
Calibration of Permeation and Diffusion Devices by an Absolute Pressure Method
Authors: Dietz RN , Smith JD
Published: March 2009

By following the change in absolute pressure above a permeation device, calibration of such sources can be performed in substantially less than one hundredth the time required using conventional gravimetric procedures. The sensitivity of the Brookhaven calibration procedure is achieved by combining high resolution pressure and temperature measuring instruments with newly designed permeation wafer devices giving low total volume when connected to the pressure measuring device. Using Brookhaven low (<20 nl/min at 30°C) and ultra-low (<1 nl/min) calibrated permeation devices, the inaccuracies and expense associated with the use of exponential dilution flasks and large quantities of diluent “zero” gas for providing part-per-billion calibration gases are reduced markedly. In addition, controlled flow rates of noncondensable gases such as carbon monoxide and methane can be provided at microlitre-per-minute rates using Brookhaven porous glass diffusion devices.
Use of the National Bureau of Standards Standard Reference Gases in Mobile Source Emissions Testing
Authors: Paulsell CD
Published: March 2009

The Mobile Source Air Pollution Control (MSAPC) program has developed a system of primary gas standards which permits commercial gas blends to be named within 2 percent of true value and a computer program which documents the path and traceability relationship of each gas to the National Bureau of Standards (NBS) standard reference material (SRM).

The MSAPC program incorporates gravimetric gas blending as a primary means to verify and extrapolate the work of the NBS. These blends comprise the reference points for a two-point linear interpolation procedure for gas analysis and correlation. The advantages and limitations of this procedure are outlined and quantified.
Gas Standards, How Standard Are They?
Authors: Wechter SG , Grieco HA
Published: March 2009

Not everyone who works with ultra-high purity gases is aware of the difficulties involved in establishing a primary gas standard. The problems associated with the necessary correlation procedures, the instability of certain gases, reaction of gas mixtures, etc., are complicated further by the fact that many firms maintain their own primary standards, with little or no effort given to correlate values with others. It is obvious, therefore, that the only remedy for this haphazard situation is to establish a single repository for primary standards. Because of its history and experience in such matters, the U.S. National Bureau of Standards (NBS) is the only likely choice to serve as this repository. As is commonly known, this is no panacea. All firms involved in the specialty gas business must work continuously to maintain the effectiveness of the primary standards established. An absolute, by definition, is impossible to attain. However, by diligent efforts in correlating gases, we, as an industry, can approach that absolute as closely as possible.

The use of by-weight mixtures is not always as accurate as one may think. This paper intends to point up, by way of specific examples, several correlation techniques we have found necessary in certifying a primary standard, and to point up our present and future needs for standard reference materials supplied by NBS.
Development of Synthetic Standard Samples for Trace Analysis of Air Particulates
Authors: Pradzynski AH , Rhodes JR
Published: March 2009

Synthetic, “homogeneous,” and particulate standard samples in the form of deposits on filters have been developed for use in quality control of analytical methods and for calibration of X-ray emission spectrometers.

The standards for X-ray emission spectrometer calibration comprise membrane filters with single element or multielement solutions homogeneously deposited and dried, and membrane filters with known amounts of single mineral powders of well-defined particle size ranges deposited and fixed on them.

For quality control of analytical methods and laboratories, synthetic standards for sulfates, nitrates, and trace elements have been developed. The standards for sulfates, nitrates, and volatile trace elements were deposited in the form of solutions on glass fiber filters and dried. The standards for nonvolatile trace elements were prepared from -10-μm quartz powder spiked with compounds of the elements and deposited from air suspension.
Methods for Calculating an LC50
Authors: Stephan CE
Published: March 2009

A variety of graphical and computational methods can be used to derive a median lethal concentration (LC50) from concentration-mortality data produced by an acute mortality test. In the selection of a method, practical considerations should receive as much attention as the usual theoretical and statistical considerations. No method should be used that does not calculate both the LC50 and its 95 percent confidence limits. Unfortunately, several computational methods will not calculate an LC50 from some concentration-mortality data that are practically and statistically useful to aquatic toxicologists. Useful, statistically sound information about the LC50 and its 95 percent confidence limits can be calculated from the data produced by any acute mortality test that meets published criteria of acceptability, by using an internally consistent scheme based on the moving average method and the binomial test.
Diet Quality in Fish Toxicology: Effects on Acute and Chronic Toxicity
Authors: Mehrle PM , Mayer FL , Johnson WW
Published: March 2009

The importance of diet quality in toxicological research with fish was illustrated in several studies. The acute toxicity of chlordane to rainbow trout was dependent upon the type of diet fed before toxicity testing. Rainbow trout were fed four commercial diets or a low (23 percent) or high protein (45 percent) synthetic diet. After 42 days, the trout were tested against chlordane in static toxicity tests. The 96-h median lethal concentration (LC50) for the synthetic 45 percent protein group was statistically higher (P = 0.05) than values for all other groups. Also, differences in LC50S existed among groups fed commercial diets. In flow-through toxicity studies, rainbow trout, bluegill, and channel catfish fed a diet containing casein and gelatin as a protein source had a greater tolerance to polychlorinated biphenyls (PCBs) than those fed a diet with fish meal and soybean meal as the primary protein sources. By increasing the concentration of the amino acid methionine in the diet of rainbow trout, the toxicity of dichlorodiphenyltrichloroethane (DDT) increased while dieldrin toxicity decreased. In studies with channel catfish, the concentration of vitamin C in the diet influenced the chronic effects of toxaphene on growth and skeletal development. These studies illustrate that the type of diet fed before acute toxicity testing and during chronic toxicity testing is important, and that consideration for nutritious standard diets in toxicological research with fish is needed.
Comparisons of the Ballistic Impact Response of Metals and Composites for Military Aircraft Applications
Authors: Avery JG , Porter TR
Published: March 2009

This paper compares the ballistic impact response of advanced fiber composites and metals. These comparisons are made within the framework of a methodology that defines the necessary data and analysis requirements for evaluating the survivability of combat aircraft designs.

A side-by-side comparison was made of the available residual strength and damage size test data for metals and fiber composites damaged by small arms projectiles. In addition, the available composite data was used to extend a model for predicting the ultimate strength of composite tension panels damaged by bullets. This model was used in conjunction with an existing model for metals to extend the comparisons to equal strength, equal stiffness, or equal weight structural panels.

The results show that both metal and fiber composite panels lose a significant percent of their undamaged strength (50 percent or more) when impacted with small arms projectiles. For the cases considered, the percent reduction in the fiber composite panels was greater than in the metal panels. These results are considered to be preliminary for structural evaluations, however, because only simple panel data were used in the comparison.
Impact Damage Tolerance of Graphite/Epoxy Sandwich Panels
Authors: Oplinger DW , Slepetz JM
Published: March 2009

The resistance of graphite/epoxy sandwich panels to low energy, foreign object impact damage was studied. Falling weight impact tests were performed on 104 rectangular sandwich panel specimens. The effect of several material, geometry, and loading parameters on damage susceptibility was explored. Damage observed visually was related to residual strength of specimens taken from the impact region, and in some cases, to static indentation tests carried out on companion specimens.

Sandwich test specimens were fabricated with face sheets of graphite or S-glass/epoxy with a 1-in. depth nomex honeycomb core. Fiber type, core density, and laminate orientation were fabrication variables. Drop weight tests were accomplished using a 2-in.-diameter steel ball. Initial and residual static shear strength were measured on notched, four-point bend specimens.

Impact tests showed that graphite sandwich panels are much more susceptible to foreign object damage than S-glass panels. The impact energy required to sustain the same relative damage level was an order of magnitude greater for the S-glass than for the graphite panels. The failure characteristics observed suggest that this is due primarily to the low strain to failure of graphite composites. Local core crushing occurred in all tests, and all but the S-glass panels suffered fiber fracture and permanent indentation at low energy levels. Core stiffness had an observable effect on impact resistance, but other parameters studied did not appear to significantly affect damage tolerance.

An analysis was carried out in which the sandwich panel was represented as an orthotropic sheet on an elastic foundation, and a classical, double Fourier series approach was taken. The load condition was approximated by an influence function technique to effect a constant radius of bending curvature, simulating the region around the drop weight ball. The capability exists to vary the material constants of the face sheet and core to investigate the nature of indentation failure, and to identify factors contributing to impact resistance. Numerical results were obtained for some of the material parameters employed in the impact tests.
Failure Mechanisms in Composite Plates Impacted by Blunt-Ended Penetrators
Authors: Cristescu N , Malvern LE , Sierakowski RL
Published: March 2009

Tests of 0–90° ply fiberglass roving-epoxy plates, impacted by hard steel cylindrical penetrators, have revealed a sequential delamination mechanism, especially well developed in plates having more than one layer of fibers in each unidirectionally reinforced lamina. In these plates the sequential delamination mechanism was the principal mechanism of spreading the deformation to parts of the plate distant from the impact point.

In impacts by a cylinder of radius R, at moderate velocities such that the shear cut-out of a plug does not extend all the way through the plate, the sequential delamination is begun when a strip of width 2R of the first lamina is pushed forward by the penetrator, initiating two shear cracks through the thickness of the lamina parallel to the fibers of the first lamina. This strip in turn loads transversely the second lamina and initiates a separation between the first two laminas. This interlaminar crack spreads until it is stopped by the cutting-through of the loading strip by the penetrator. The process is then repeated by the second and third laminas, followed by the third and fourth, and continues through the thickness of the plate, with each subsequent delamination covering a larger area than the one before it.

Other failure mechanisms in composite-plate perforation are also discussed, especially fiber stretching and tensile breaking. Recommendations for further analytical and diagnostic testing are made.
Response of Isotropic and Composite Materials to Particle Impact
Authors: Greszczuk LB
Published: March 2009

This paper is devoted to determination of damage mechanisms in isotropic and composite materials subjected to particle or projectile impact. The approach consists of three steps: (1) determination of time-dependent surface pressure distribution under an impacting particle, (2) determination of internal stresses in the target caused by the surface pressure, and (3) determination of failure modes in the target caused by the internal stresses. The pressure distribution under an impacting particle is obtained by analytically combining the dynamic solution to the problem of impact of bodies with the static solution for the pressure between two bodies in contact. Having the time-dependent surface pressure, available static analyses are used to obtain the time-dependent triaxial stresses in the targets made of isotropic materials, whereas, for targets made of composite materials the internal stresses are determined using finite-element computer solution. The internal stresses in targets made of isotropic and composite materials are expressed in terms of target and projectile properties, impact velocity, and impactor shape, and are used to determine the threshold velocities to initiate target damage. Types of target failures considered include tensile cracking, compression/crushing, and subsurface shear failure. Curves are presented that show the relationship between target properties (strength and modulus) and threshold velocity to initiate damage. The results are applied, in an approximate manner, to composites to establish their relative impact resistance. Types of composites considered include: fiberglass, boron-epoxy, and graphite-epoxy. Predictions are made of the threshold velocities to initiate tensile, compressive, and shear failures in the three types of composites and of the order of occurrence of these failure modes.
Microcrack Growth in Graphite Fiber-Epoxy Resin Systems During Compressive Fatigue
Authors: Kunz SC , Beaumont PWR
Published: March 2009

Transfibrile crack extension in graphite fiber-epoxy resin composites was investigated in notched beams under cyclic compressive loading. Compressive fatigue crack growth was evaluated using selected linear elastic fracture mechanics parameters. A model was used to correlate observed micro-fracture processes with compressive crack extension behavior. Crack propagation underwent periods of deceleration and acceleration, and the crack growth rate dependence on material and environmental variables was determined. Transfibrile fatigue crack extension in unidirectional composites is a result of axial cracking and frequently resulted in crack arrest. Comparison of unidirectional composites with different epoxy resins showed the composite with the higher bond strength to be less susceptible to axial cracking along the fiber-matrix interface than the one with the lower bond strength. Crossplied (0°/90°) composites had lower compressive strengths, and through-specimen fractures resulted from axial cracking in the 0° plies, splitting in the 90° transverse plies, and splitting between plies. Exposure to a saline solution greatly increased axial cracking in all the composites and enhanced transverse ply splitting in the cross-plied material. Crack tip blunting and crack arrest due to solution-induced interfacial degradation was frequent.
Nonlinear Response of Boron/Aluminum Angleplied Laminates Under Cyclic Tensile Loading: Contributing Mechanisms and Their Effects
Authors: Chamis CC , Sullivan TL
Published: March 2009

The nonlinear response of boron/aluminum angleplied laminates subjected to cyclic loads was investigated. A procedure is outlined and criteria are proposed which can be used to assess the nonlinear response. The procedure consists of testing strategically selected laminate configurations and analyzing the results using composite mechanics. Results from the investigation show that the contributions to nonlinear behavior are due to: premature random fiber breaks where the ply orientation angle (POA) is small relative to the load direction, ply relative rotation (PRR) at intermediate values of the POA, and nonlinear aluminum matrix behavior at large values of the orientation angle. Premature fiber breaks result in progressively more complaint material; large PRR result in progressively suffer material; and, pronounced matrix nonlinear behavior results in no significant change in the modulus of the initial portion of the stress-strain curve.
Fatigue Behavior of Carburized Steel
Authors: Landgraf RW , Richman RH
Published: March 2009

This paper represents the first part of a systematic investigation of factors affecting the fatigue resistance of surface-hardened steel components. The adopted approach is to view a surface-hardened member as a composite material consisting of a high strength, low ductility case and a lower strength, higher ductility core. A series of smooth axial specimens, representing case and core carbon contents, were prepared to determine cyclic stress-strain and strain-life curves. The cyclic properties obtained from these tests were then used to analyze and interpret the cyclic behavior of carburized specimens. Both axial and bend specimens were carburized and subjected to constant amplitude, strain-controlled fatigue tests. A discontinuity in the resulting strain-life curves, representing a shift from surface to subsurface crack initiation, is predictable from comparison of the strain-life curves for simulated case and core material. Finally, a relation is developed to determine optimum casexore ratios taking into account cyclic material properties, residual stresses, strain gradient, and applied stress or strain level.
Fatigue and Shakedown in Metal Matrix Composites
Authors: Dvorak GJ , Tarn JQ
Published: March 2009

Simple mechanical models of unidirectional metal matrix composites are used to analyze elastoplastic deformation and shakedown in the matrix under cyclic composite loads. Both axial and off-axis loadings of a lamina are considered. It is shown that the fatigue limits of as-fabricated boron-aluminum, beryllium-aluminum, tungsten-copper, and other composites generally coincide with the composite shakedown limits because the matrix yield stresses and fatigue limits are equal.

In heat-treated composites, the matrix yield stress is usually much higher than the fatigue limit, and matrix fatigue failure can take place in the shakedown state. The residual microstresses caused by heat treatment are estimated, and their influence on fatigue is discussed. A method for improvement of the fatigue resistance of heat-treated composites is discussed.

The theoretical predictions of fatigue limits are verified by an extensive comparison with available experiments, and a very good agreement is obtained. It is concluded that, in principle, the composite fatigue failure can be avoided if each of the constituents is stressed within its particular fatigue limits during a cyclic loading program of the composite.
Effects of Environment on the Fatigue of Graphite-Epoxy Composites
Authors: Sumsion HT , Williams DP
Published: March 2009

Torsional and flexural fatigue tests were performed on both uniaxial (0°) and crossplied (±45°) graphite-epoxy materials at temperatures of 24 and 7°C in environments of air and water. The results of the torsion testing showed that the number of cycles required to cause an initial decrease in stiffness as well as the rate of stiffness loss was a function of temperature and environment; the most significant losses were noted for tests at the higher temperature in water. The torsional fatigue specimens were subsequently tested in four-point bending to determine the effect of torsional damage on longitudinal properties. This damage caused changes in the flexural stiffness, failure stress, and failure energy, depending on the stress and environmental histories. The flexural fatigue tests also showed a significant effect of water (at 24°C) on the material behavior. These results are compared with the results of previous investigations and are discussed in terms of proposed damage mechanisms.
Foreign Object Damage and Fatigue Interaction in Unidirectional Boron/Aluminum-6061
Authors: Gray TD
Published: March 2009

An experimental program was conducted to study the effects of foreign object damage (FOD) on the bending fatigue characteristics of a composite material, unidirectional boron/aluminum-6061. Fatigue curves were generated for a control group and each of four levels of FOD. The composite was further, characterized by static tensile and nondestructive tests. All tests were carried out at room temperature. A similar damage and fatigue experiment was done for a titanium alloy, Ti-6A1-4V, to provide baseline data with which to compare the composite. It was concluded that the composite suffers a greater percentage reduction in fatigue strength than does Ti-6A1-4V for a given impact energy.
Debond Propagation in Composite-Reinforced Metals
Authors: Roderick GL , Everett RA , Crews JH
Published: March 2009

Strain energy release rates were used to correlate cyclic debonding between metal sheets and composite reinforcement. An expression for the strain energy release rate was derived and applied to fatigue test results for three material systems: graphite bonded to aluminum with both a room temperature and an elevated temperature curing adhesive; and, S-glass bonded to aluminum with an elevated temperature curing adhesive. For each material system, specimens of several thicknesses were tested with a range of fatigue loads. Cyclic debonding was monitored using a photoelastic technique. A close correlation was found between the observed debond rates and the calculated strain energy release rates for each material system.
Reliability After Inspection
Authors: Davidson JR
Published: March 2009

Because materials and structures cannot be made to always be perfect, they are inspected to determine if they contain flaws or defects large enough to influence their strength, reliability, or economic life. Inspection methods and procedures depend upon the part configuration, possible flaw type, orientation, location, and accessibility. The procedure will depend upon prior knowledge of possible defects and whether or not the inspector is to decide if a single flaw is at a specific location or if no significant flaws exist anywhere in some distributed area or volume.

Long-lived structures require that initial flaws be small so that the flaws will not grow to a critical size during the structure's life or between inspections. Consequently, nondestructive inspection methods are commonly pushed to their limits. For example, the size of a permitted flaw might be just less than the size flaw which will be detected 90 percent of the time. As a result, nondestructive engineering (NDE) methods are not infallible, and some flawed parts might pass inspection. The question, then, is how to calculate the reliability of a part or a structure that has passed inspection.

Three analyses have been developed to calculate this a posteriori reliability. Each handles an increasingly complex situation. The first and simplest gives the reliability based upon the efficiency of the detection method and the probability that the part was unflawed when it reached the inspector (a priori reliability).

The second deals with the problem where flaws are distributed over an area or throughout a volume. Here, the mean number of flaws per unit area or volume (a priori) is a parameter; the actual number in a part is assumed to be Poisson distributed.

The third analysis predicts the a posteriori reliability for a structure with distributed flaws but where some portions are inaccessible and cannot be inspected.
Transmission Electron Microscopy in Materials Research
Authors: Wells MGH , Capenos JM
Published: March 2009

This paper very briefly reviews the development of transmission electron microscopy (TEM) including instrumentation and specimen preparation techniques, and generally describes typical examples of the use of TEM today in the study and understanding of the st ructure of materials. New observation techniques such as energy loss analysis, dark field imaging, the weak beam technique, Kikuchi line analysis, and computer generation of dislocation images are discussed. In addition to forefront work, many illustrations are given where TEM has greatly contributed to the optimization of properties and general improvement of many commercially important materials.
Definition, Functional Design, and Implementation of a Dedicated Computerized Laboratory System: The GC Computing Recorder
Authors: Zawadowicz ST , Kegg AL
Published: March 2009

This paper describes the process employed in defining and creating an integrated instrument with computing and recording capability that generates a document containing a full chromatogram juxtaposed with its quantitative on-line analysis. This selfcontained system, called the GC Computing Recorder, operates from the raw gas chromatograph detector signal through appropriate signal conditioning, analog-to-digital conversion, microcomputer-based digital integration and postintegration calculation to generate the final analytical report, termed the integrated chromatogram.

The paper briefly reviews the historical development of gas chromatographic quantitation technology and it postulates the system requirements for single channel quantitation instrumentation. Then, it summarizes the specific design approaches considered for the computing recorder, the evolution of the system architecture from the point of view of its inputs and outputs, and the selection of the architectural approach adopted for the final design. Particular attention is devoted to man/machine interface considerations, signal conditioning design, digital filtering, analog-to-digital conversion techniques, and firmware integration treatments.

Criteria developed to enhance the integration portion of the system firmware are explored, and the algorithmic treatments of overlapping peaks, drifting baselines, area recovery, and multiple peak resolution are discussed. The detailed systems description also covers the areas of postintegration calculations including area normalization, response factors, and relative retention times, as well as the application of internal standard methods for precision determinations of component concentration levels.

Experience with the instrument under actual laboratory conditions is summarized, and observations are made concerning possible system extensions.
Feasibility Study and Functional Design for the Computerized Automation of the Central Regional Laboratory EPA Region V, Chicago
Authors: Frazer JW , Barton GW
Published: March 2009

A feasibility study and functional design is presented for the computerized automation of the Central Regional Laboratory of Region V of the Environmental Protection Agency. The system recommended, which meets all the stated objectives, is built around a Data General Nova 840 computer operating in a time-share mode using the BASIC high-level language operating system for applications programs. Instruments to be automated include Technicon Auto Analyzers, atomic absorption spectrometers, and an electronic balance. The system will include file management programs to take care of the laboratory needs. Data will be transferred to STORET on magnetic tape.

This paper is divided into several sections. The first section includes (1) an overview of the functions selected by the laboratory for our consideration with a discussion of the benefits expected from automation of these functions, and (2) a detailed cost and benefit breakdown of ten alternatives, each meeting the same or all of the objectives. The final sections are functional designs for each of the instruments and the sample file control, detailing the desired interaction between the operators, instruments, and data.

The goals of this project are to: (1) increase instrument capacity, (2) improve the accuracy and precision of analytical results, (3) save analysts' time, (4) reduce clerical time and associated errors, and (5) provide ready access to the analytical data.
Performance of Portable Automatic Wastewater Composite Sample Collectors
Authors: Keffer WJ
Published: March 2009

A summary of the reliability of eleven commercially available wastewater sample collectors is presented. Installation procedures are reported which resulted from about 90 000 h of operation with sampling equipment at municipal and industrial waste treatment facilities under summer and winter conditions.

Water chemistry data, primarily five-day biochemical oxygen demand (BOD5), chemical oxygen demand (COD), and nonfilterable solids (NFS), for time and flow-proportional samples collected concurrently by piston pump, peristaltic pump, vacuum, and pressure operated compositors were compared to results obtained with manual sampling techniques.

Variations in nonfilterable solids levels exceed 100 percent in some instances for composite samples collected at the same point and over the same time span by different models of commercially available compositor equipment. Variations in five-day biochemical oxygen demand and chemical oxygen demand levels were also significant but ranged, generally, from 35 to 50 percent.

A proposal is presented for the development of a standardized test procedure for evaluation of sampler performance based on suspended solids recovery. Equipment features which the “ideal” sampler would incorporate are recommended.
Observations on the Prediction of Fatigue Crack Growth Propagation Under Variable-Amplitude Loading
Authors: Schijve J
Published: March 2009

The paper starts with a discussion on loads in service, after which a survey is given of various types of variable-amplitude loading as applied in test programs. The various phenomenological aspects of fatigue damage associated with fatigue cracks are indicated. Interaction effects between cycles of different magnitudes are defined. Methods for measuring interaction effects, examples of interaction effects, and possible explanations are reviewed. This includes both tests with simple types of variable-amplitude loading (overloads and step loading) and more complex load-time histories (program loading, random load, and flight-simulation loading). New evidence on crack closure is presented. Various types of prediction methods are discussed. The paper is primarily a survey of the present knowledge, with an analysis of the consequences for prediction techniques.
Mechanisms of Overload Retardation During Fatigue Crack Propagation
Authors: Bernard PJ , Lindley TC , Richards CE
Published: March 2009

The effect of single overloads on room-temperature fatigue crack growth has been studied in two steels of markedly different yield stresses. The observed retardation effects have been presented and the evidence suggests that overload retardation is primarily due to residual compressive stresses generated in the crack tip region, and associated with crack closure effects. The results have been rationalized in terms of a fatigue crack growing through overload plastic zones of different shapes and sizes associated with plane stress and plane strain deformation.
Prediction of Fatigue Crack Growth under Irregular Loading
Authors: Nelson DV , Fuchs HO
Published: March 2009

Fatigue crack growth under irregular loading is calculated from constant-amplitude test data. The results of such calculations are compared with measurements of crack growth in modified compact tension specimens made of two commonly used structural steels and subjected to three different irregular load histories, each applied at several load levels.

Two crack growth rate relations are utilized: I, the Forman relation, and II, a relation based on an effective stress intensity range concept. The Forman relation is used with two different methods of “counting” load ranges, that is, crack growth is calculated: (a) for all rising tensile load ranges as they occur in the load history and (b) for the load history condensed by a method which forms overall ranges and includes only the top decile of all rising tensile ranges. Crack growth rate Relation II is used only with counting Method a. The three resulting prediction methods are designated Ia, Ib, and II. Methods Ia and Ib disregard sequence effects, while Method II includes them.

Predictions of crack growth using Methods Ia and Ib agree with average test lives to within a factor of two in nearly all cases, with the exception of those instances where large compressive loads cause gross yielding and accelerated growth. Predictions based on Method II are superior to those for Ia and Ib when such gross yielding occurs and are comparably good for the other cases investigated here.
Spectrum Crack Growth Prediction Method Based on Crack Surface Displacement and Contact Analyses
Authors: Dill HD , Saff CR
Published: March 2009

A method for prediction of crack growth behavior has been developed, based on evaluations of stress intensity caused by crack surface contact. The potential interference of the crack surfaces is determined from analyses of elastic displacements during loading and unloading and of the permanent deformation left in the wake of a growing crack. The potential interference is treated as a wedge acting behind the crack tip and the contact stresses created by this wedge are computed through an elastic-plastic analysis. The effective stress intensity range used for crack growth prediction is found by subtracting the stress intensity caused by these contact stresses from the applied stress intensity range. Comparisons of crack growth behavior predicted by this method and that measured in constant amplitude tests, with and without high loads, and in block spectrum tests have shown that the method accounts for load interaction effects in these cases. These effects include delayed retardation following high loads, crack growth acceleration during high loads, and dependence of growth rates on number of high loads.
Fatigue Behavior of Aluminum Alloy Weldments
Authors: Sanders WW , Lawrence FV
Published: March 2009

During the last eight years, a number of research studies have been conducted on the fatigue behavior of aluminum alloy weldments under the guidance of the Aluminum Alloys Committee of the Welding Research Council. The initial study was a comprehensive review of the current (1970) state of knowledge and the development of research needs. The additional studies have included investigations into the effect of weld orientation (longitudinal versus transverse), thickened plates, and weld defects on fatigue behavior. This paper provides a summary of these five studies.
Fatigue Crack Propagation in A537M Steel
Authors: Sandifer JP , Bowie GE
Published: March 2009

Fatigue crack propagation rates are presented for weldments in A537M steel at room temperature. Rates are determined for cracks propagating along the fusion line, in the melt zone of welds made with two shielding gas ratios, and in the base metal. Static tension and Charpy impact tests conducted on specimens from the base material and melt zone also are presented. Results indicate that crack growth resistance of A537M steel is not degraded by proper welding procedures, and the weld zone may impede growth rates. Shielding gas ratios, which affect tensile properties, are shown not to affect fatigue crack growth rates significantly. An interim da/dN versus ΔK design curve is computed for the data sets, and its application to flawed plate life prediction is discussed.
Procurement and Contracting
Authors: Abert JG
Published: March 2009

There have been few successful procurements of resource recovery systems. Of those which have led to contract only a few have been for the provision of recovery on a fee-for-service basis. This paper discusses some of the problem areas that must be overcome if recovery is to become a significant aspect of the municipal solid waste management program. A plea is made for a “fairness” doctrine and more openess in the procurement process.
Materials Recovery Systems
Authors: Bernheisel JF
Published: March 2009

A system representing the state-of-the-art has been formulated to separate various materials contained in municipal solid waste. This materials recovery system uses equipment which is either in production or in pilot operation. The system utilizes the different physical properties of paper, glass, ferrous metals, aluminum, and other nonferrous metals to achieve mechanical separations. The first operation of the system is shredding which produces a relatively uniform particle size and liberates individual materials from composite structures. This is followed by a series of equipment which operate on size, density, magnetism, lift/drag, electrical conductance, and light reflectance to achieve separation. The materials so recovered can be utilized by industry as raw materials, thereby conserving natural resources.
Glass in Solid Waste Recovery Systems
Authors: Seeley CE
Published: March 2009

The author discusses the basic principles of glass melting and the role of cullet or reclaimed glass from solid waste systems in glass melting. He provides limits or quality specifications for reclaimed glass and explains the reasons for the strictness of the specifications. The author is optimistic for the possible development of new technology for upgrading the reclaimed glass to a more widely acceptable material for reuse in glass manufacture.
Report on the Glass Workshop
Authors: Scott P
Published: March 2009

The workshop concluded that the prospect for recovery of glass cullet from the solid waste stream is technically and economically feasible. The paper describes the major markets for waste cullet including glass containers, glass wool, flat glass, and the building materials industry. A discussion of standards and specifications for limiting contamination and color-sorting glass in the future is included.
Neutron Sources for Radiography and Gaging
Authors: Cutforth DC
Published: March 2009

The paper is mainly a review of technical and economic characteristics of various types of neutron sources that could be considered for neutron radiography and gaging. Minimum application requirements along with sources that may be used to satisfy the requirements are presented. The primary organizations in the United States that offer commercial neutron radiography services are listed. Contacts at some organizations that manufacture and/or distribute neutron sources are also included.
Neutron Gaging Systems
Authors: Reynolds GM
Published: March 2009

A review is presented of neutron gaging concepts and applications. The gaging systems are restricted to those that measure elastic or inelastic scattered source neutrons, in either a transmission or scattering geometry. Neutron gaging, in this sense, is not selective. It cannot identify particular materials, but is useful in monitoring particular isotopes (hydrogen, boron) in otherwise known matrices.

Discussions are given of the many areas where neutron gaging has been applied: moisture measurements in soil, food, and the steel industry; detonating cord; metals; nonmetallic mines; well logging; and explosive ordnance and fuzes.

Although neutron gaging is inherently more sensitive than neutron radiography and presents the results in real-time, it is less commonly used than radiography. The advent of digital imaging tubes could allow two-dimensional information to be obtained from gaging systems and thereby increase their relative importance.
Neutron Radiography of Fuel Pins
Authors: Jackson CN , Powers HG , Burgess CA
Published: March 2009

Neutron radiography performed with a reactor source has been shown to be a superior radiographic method for the examination of unirradiated mixed oxide fuel pins at the Hanford Engineering Development Laboratory. Approximately 1700 fuel pins were contained in a sample that demonstrated the capability of the method for detecting laminations, structural flaws, fissile density variation, hydrogenous inclusions, and voids in assembled fuel pins.

The nature, extent, and importance of the detected conditions are substantiated by gamma autoradiography and by destructive analysis employing alpha autoradiography, electron microprobe, and visual inspection. Also, a series of radiographs illustrate the response of neutron radiography as compared to low-voltage and high-voltage X-ray and gamma source iridium-192 radiography.
Neutron Radiographic Enhancement Using Doping Materials and Neutron Radiography Applied to Museum Art Objects
Authors: Hillig OR
Published: March 2009

Two different areas are covered in this paper which demonstrate other applications for neutron radiography. The first, “Neutron Radiography Enhancement Using Doping Material,” shows how the radiographic image can be enhanced in the area of interest to provide greater contrast and thereby show more detail. The second, “Neutron Radiography Applied to Museum Art Objects,” describes work Atomics International has done with the Los Angeles County Museum of Art to examine ancient castings to reveal the internals of the castings.