bluuebunny/crossref_metadata_2025 huggingface dataset:
A Multifaceted Approach to Applying Dispersants
Authors: Crain OL
Published: December 2008

A comprehensive oil spill response plan has been developed partially to deal with accidental discharges of oil into the Arabian Gulf. The spill response capabilities of contractor companies in the area are fairly limited. The response plan relies on chemical agents and recovery as cleanup tools. The key to effective response is a rapid response and deployment of cleanup equipment. Initially, marine vessels equipped with portable dispersant spray booms patterned after the Warren Springs equipment were used. To improve existing oil spill response, an extensive modernization of dispersant deployment equipment has been developed. The areas of modernization include (1) upgrading the marine vessel equipment, (2) dedicating boats and vessels of opportunity for dispersant application, (3) using helicopters for spill response, (4) using large fixed-wing aircraft for spill response, and (5) establishing dispersant and refueling stockpiles. This paper discusses the use of dispersants in response to an oil spill. It is intended not as a scientific paper but as a paper on a local response capability.
Physical Testing of Gypsum Board Per ASTM C 473
Authors: Acker RF
Published: December 2008

This work was performed to investigate modernization of the equipment used for the physical testing of gypsum board that has not been basically changed over a period of many years and is not commercially available. A comprehensive study has been made using a commercially available machine for three strength tests, with the expectation that this type of equipment might be incorporated into ASTM methods and specifications in the future. Technical advances in the methods of evaluating gypsum board are desirable in a progressive industry.

The procedure used was to run the three major physical tests: flexural strength; core, end, and edge hardness; and nail pull resistance on a machine using constant strain rate loading and compare those results with those obtained on the commonly used ASTM specified machine that uses a constant stress rate. A TM 51008 tester made by Testing Machines, Inc. was used for the work reported in this paper. Comparative tests were made on equipment conforming to the specifications of ASTM Physical Testing of Gypsum Board Products, Gypsum Lath, Gypsum Partition Tile or Block, and Precast Reinforced Gypsum Slabs (C 473). Preliminary work was done in a research laboratory to develop the fixtures and procedures necessary to use the new equipment. The machine was then placed in a manufacturing plant and duplicate tests on all types of board products were run for a period of several months.

Data will be presented to show that the constant strain rate method of testing can give equally precise results with a very substantial saving in time and physical effort. For flexural strength, nail pull resistance, and core hardness there is a simple linear correlation between the results with the two machines. The constant strain rate machine can more accurately determine the maximum load causing failure than the constant stress rate machine. Correlation between the results of tests on either machine shows that the core hardness and nail pull resistance tests tend to duplicate information on core properties.
Gypsum Analysis with the Polarizing Microscope
Authors: Green GW
Published: December 2008

The fastest and most accurate method for the qualitative analysis of gypsum is use of the polarizing microscope. Five bits of optical data can be used for identification of gypsum and its most common impurities such as natural anhydrite, calcite, dolomite, and silica. The optical data are morphology, refractive index, birefringence, angle of extinction, and dispersion staining. Gypsum can be identified by its refractive index of 1.521 and 1.530, its oblique extinction angle, its birefringes of 0.009, and a blue dispersion staining color when mounted in a refractive index liquid of 1.528. Natural anhydrite is normally seen as blocky crystals with a refractive indices of 1.570 and 1.614. The birefringence of 0.044 gives it much higher order polarizing colors than gypsum, and it has parallel extinction. Silica has the same birefringence as gypsum; so it is hard to distinguish with crossed polars. However its refractive index of 1.544 is higher than gypsum and has a yellow dispersion color to contrast with the blue of gypsum when mounted in 1.528. Limestone may be either calcite or dolomite. Limestone may be distinguished mainly by its very high birefringence of 0.172, which renders even very fine particles colorful with crossed polars—larger particles are high order white. Calcite may be distinguished from dolomite by mounting in a refractive index liquid of 1.660 rendering the dolomite orange with the calcite blue.

The phases of gypsum can be distinguished also. Beta hemihydrate has the same shape as the dihydrate from which it was made but is porous and cloudy rather than clear and solid. Alpha hemihydrate may be blocky or acicular and has a refractive index of 1.558 and 1.586. The birefringence is 0.028. When mounted in 1.564 liquid, the dispersion colors will change from orange to blue as the stage is rotated. Soluble anhydrite is difficult to identify, but dead-burned gypsum has a refractive index close to natural anhydrite, and the dispersion colors are red and blue when mounted in a liquid of 1.596. The qualitative analysis of natural anhydrite may be done by direct estimation, or by estimating a series of fields and averaging the results. A more precise method is to count and measure the diameters of all particles then calculate the weight percent of each.
The Effect of Sorbed Water on the Determination of Phase Composition of CaSO4 · H2O Systems by Various Methods
Authors: Turk DH , Bounini L
Published: December 2008

The efficiency of calcination processes is monitored by careful phase analysis of CaSO4 · H2O systems. The usual method of determining a small amount of gypsum in such systems involves the determination of sorbed (free) water, water of crystallization (combined water), and Ca++/SO4−− ratio. The removal of free water from CaSO4 · ½H2O and active orthorhombic calcium sulfate occurs at about the same temperature range as the decomposition of CaSO4 · 2H2O, which then becomes a most critical stage in the phase analysis of these systems. This paper discusses (1) relative merits of various methods utilized in removing free water, which includes several thermal methods and microwave drying, and (2) the state of the sorbed water as it develops from exposure to radically varying relative humidity conditions.
Determination of Sulfur Trioxide in Gypsum
Authors: Goswami S , Chandra D
Published: December 2008

This paper deals with the various sources of error in different steps of the procedure for determination of sulfur trioxide in gypsum samples, using hydrochloric acid as solvent for gypsum and barium chloride to precipitate barium sulfate. The paper suggests reduction in the amount of acid and barium chloride used in order to minimize errors. Thus, it justifies the need for the revision of Section 12 of ASTM, Chemical Analysis of Gypsum and Gypsum Products (C 471).

ASTM C 471 recommends use of 50 mL of 1 + 5 hydrochloric acid (sp gr 1.19) as solvent for a 0.5-g gypsum sample and 20 mL of 10% barium chloride as precipitant. This results in too high a concentration of acid and chloride ions in reaction solution before and after precipitation, justifiable only for dissolution of impure gypsum samples and formation of coarse barium sulfate crystals to give rapid filtering. The method is silent about the final volume to be made of reaction solution, which determines the acidity before precipitation. It is also silent about the use of and the type of filtering crucibles.

The greatest source of error is the occlusion of chloride ions caused by both hydrochloric acid and barium chloride in addition to adsorption of H+, coprecipitation of barium chloride and Ca++ ions, and increased solubility of barium sulfate in acidic solution.

Therefore, the following suggestions have been made (1) reduce the initial amount of hydrochloric acid used as solvent to 25 mL of 1 + 5 hydrochloric acid for the 0.5-g test sample, (2) use 20 mL of 6% barium chloride solution (preferably old), (3) make the volume of the reaction solution up to 400 to 500 mL before precipitation of barium sulfate, and (4) use filtering crucibles. These changes will increase the accuracy of the sulfate determination by minimizing error caused by high acid and chloride concentration and by maintaining quick dissolution and filtering. Analyses performed with these changes have been found to be consistent and accurate.
The Relationship Between Water Demand and Particle Size Distribution of Stucco
Authors: Luckevich LM , Kuntze RA
Published: December 2008

In gypsum board production, the amount of water required for a stucco slurry with a suitable fluidity is considerably greater than the amount necessary for hydration of the stucco. Since excess water must be removed by drying, it is advantageous, from an energy point of view, to reduce the consistency or water demand of stucco. Constant board density is maintained thereby through increased addition of foam.

The high water demand of stucco produced by conventional calcination methods is due largely to the ability of the stucco to disintegrate, a process during which larger stucco particles break down into smaller particles upon contact and subsequent mixing with water. The water demand of stucco may be reduced by aging, that is, the exposure of stucco to water vapor over a period of time, which reduces the ability of the stucco to disintegrate. However, aging also has a negative effect on both setting characteristics of the stucco and, as a result, on the strength of the gypsum formed.

The objective of the work described in this paper was to study the relationships between water demand and particle size distribution as affected by changes in disintegration during aging. Particle size analysis and several methods of consistency measurement were used for this purpose. It was found that a direct relationship exists between water demand of stucco and particle size distribution as defined by percent disintegration, with minor deviations at initial stages of aging. In contrast, nonlinear relationships were found, with preliminary experiments, for stuccos containing aridizing agents or surfactants, which indicates that the water demand of stucco is also affected by surface properties. The water demand of stucco is not a function of the surface area of the stucco, that is, other properties, such as particle shape and surface characteristics, play a significant role. Similarly, the magnitude of the differences in water demand of various types of stucco indicates that particle size distribution, although the major factor, is not the only one influencing this property.
Retardation of Gypsum Plasters with Citric Acid: Mechanism and Properties
Authors: Koslowski T , Ludwig U
Published: December 2008

The object of the investigation was the retardation of gypsum plasters with citric acid. For that purpose measurements were carried out to get information about the mechanism of set retardation and the influence of citric acid on the microstructure and properties of gypsum plasters. Citric acid acts as a retarder by forming citrate. The citrate affects the nucleation and the crystal growth of gypsum by adsorption. That entails the retardation of the hydration period and the habit modification. The influence on the microstructure was investigated by means of the quantitative image analyses and by X-ray methods. Citric acid changes the properties of fresh and hardened mortars. The volume of setting and hardening gypsum plaster passes through a minimum. Increasing citric acid additions raise the minimum and decrease the following expansion. Strength formation was measured by binding and compressive strength tests and by Brinell hardness determination. With increasing citric acid addition, paralleled by higher humidities, a strong decrease in strength can be observed. In addition, the influence of citric acid on the creep behavior of hardened gypsum was examined.
Assessment of Environmental Impacts Associated with Phosphogypsum in Florida
Authors: May A , Sweeney JW
Published: December 2008

In its role to provide technology to prevent or limit adverse environmental impacts associated with mining or minerals processing, the U. S. Bureau of Mines has conducted research at its Tuscaloosa Research Center to assess the environmental impacts of phosphogypsum produced by the Florida phosphate industry. Over the years, stockpiles containing 304 million metric tons of phosphogypsum have accumulated, and the industry continues to generate an additional 30 million metric tons a year. Samples from approximately 300 m of drill core, obtained from nine stockpiles were characterized using chemical, X-ray diffraction, emission spectrographic, radiological, and physical means. The data developed indicated that phosphogypsum is not a corrosive or toxic hazardous waste as defined by the Environmental Protection Agency (EPA) criteria. Radium analyses averaged 21 pCi/g and its content was inversely related to particle sizes. Thirty-nine elements were detected in phosphogypsum; concentrations of these elements did not vary with depth within the stockpiles.
Drying and Agglomeration of Flue Gas Gypsum
Authors: Wirsching F
Published: December 2008

Flue gas gypsum is obtained as a moist finely divided powder from the desulfurization of combustion gases in power plants. From its upgrading by drying and agglomeration, a material is produced very similar in its properties to that of natural gypsum. The drying is carried out very successfully by using rapid driers. Agglomeration can be done by the process of briquetting, compaction, or pelletizing. Briquetting, the most reliable of the agglomeration processes, will be described in more detail. Flue gas gypsum briquets can be used by both the gypsum and the cement industry. In case of a surplus, these briquets can easily be stored in the open, especially during winter months. This puts the power plant operator in a position whereby he can produce by-product gypsum with a variety of application properties and at the same time contribute to the gypsum being reliably and economically utilized.
Quality Assurance Aspects of Environmental (Aerometric) Data Management
Authors: Beebe RC , McDaniel AS , Clement DW
Published: December 2008

Considerable attention has been directed towards techniques and procedures which facilitate the high quality of field-collected ambient environmental data.

This study addresses the quality control methods used to assure data quality after the data have been recorded. The two major elements associated with the validation of much of Tennessee Valley Authority's (TVA's) environmental data are: (1) initial computer flagging of physically/chemically questionable and outlying data and (2) analyst review and feedback to field technicians to implement corrective actions. Examples of these procedures as applied to aerometric data will be discussed.

The benefits of this approach include timely feedback to the field technicians to resolve potential problems with a monitoring system and assignment of quality code ratings and precision and accuracy to all archived and reported data.
Quality Assurance for Microbiological Analyses of Water
Authors: Bordner RH
Published: December 2008

The establishment of microbiological contaminant limits for water and wastewater and the implementation of enforcement programs which require monitoring of these limits have emphasized the need to develop and practice quality assurance (QA) programs. A broadscope QA program is essential for microbiological determinations. The basic elements of an intralaboratory quality control (QC) program are described, which include controls over personnel, facilities, sampling techniques, laboratory operations, analytical procedures, and data reporting. Formal, written analytical procedures, a QA protocol, and complete QC records are indispensable to a QA program. The laboratory should participate in an interlaboratory QC program established to maintain minimal analytical and operational standards. The U.S. Environmental Protection Agency (EPA) certification program for analyzing public drinking water supplies is described as an example of a national interlaboratory program. Guidelines provided by the EPA for laboratory QA programs are outlined.
Steps to Valid Particle Size Data from Emissions Sources
Authors: McCain JD , Felix LG , Farthing WE
Published: December 2008

This presentation is directed toward applications of those devices most commonly applied in the measurement of industrial source particle size distributions: cascade impactors and cyclones. Quality assurance (QA) in field programs set up for the determination of particle size distributions includes many of the same steps as those for the determination of particulate concentration and emission rates such as would be applicable to Environmental Protection Agency (EPA) Methods 5 and 17. However, a number of additional levels of QA must be added. These include specifying and verifying protocols for withdrawing a representative sample from the gas stream, steps to minimize and correct for the effects of interferences, operating protocols to ensure that the sampling conditions fall within the constraints of the hardware being used, sampler preparation, sample handling, and record-keeping.

Examples of specific problem areas to be addressed are (1) traverse methodology; (2) the number of samples required to obtain a given confidence level in the results; (3) the selection of samplers and the choice of operational parameters such as sampling flow rate; (4) inteferences, controls, and blanks; (5) sample recovery and handling; and (6) post-test verification that the actual sampler operation fell within the limits for reliable performance for the device(s) used.
Development of Statistics and Limits for DMR-QA Studies, and Summary of Experience in DMR-QA Study 2
Authors: Britton PW
Published: December 2008

The U.S. Environmental Protection Agency (EPA) has conducted two Discharge Monitoring Report — Quality Assurance (DMR-QA) studies to evaluate the performance of laboratories doing analyses required in major National Pollution Discharge Elimination System (NPDES) permits. The object of these studies is to identify laboratories that appear to be having significant analytical problems and that should receive follow-up contact by the state or EPA region with primacy.

Participants receive a set of sample concentrates to be diluted to volume with distilled water. The resulting samples can be analyzed for 26 of the analytes most frequently limited in permits. Analytical results are submitted to EPA for evaluation against appropriate acceptance limits and a report is returned to each participant. The acceptance limits are constructed as 99% confidence intervals based upon the state-of-the-art analytical capabilities demonstrated by participating EPA and state laboratories. The statistical basis for the acceptance limits in the most recent study, DMR-QA Study 2, is discussed in detail.

DMR-QA Study 2 included data representing 5157 major NPDES permits and all 50 states. On the average, 22% of these data were beyond the acceptance limits, indicating there is considerable potential for improvement. Results from DMR-QA studies focus the limited follow-up resources of the primacy agencies to maximize the improvement in DMR data quality. Whether any improvement actually occurs, however, depends entirely upon the commitment of the responsible state and EPA enforcement offices, as well as the major NPDES dischargers, to make the changes necessary to improve the quality of monitoring data.
Quality Assurance of Meteorological Measurements
Authors: Lockhart TJ
Published: December 2008

The quality assurance (QA) program for meteorological measurements must begin with a QA plan which identifies the purposes for which the measurements will be made. Assume a monitoring task where a one-year data set of hourly values of wind speed, wind direction, air temperature, relative humidity, and precipitation amount is needed to describe the air quality measurements being automatically recorded.

The QA plan will define the accuracy needed for this description and will give the quality control tasks necessary to produce data of this accuracy. The plan will also address the auditing tasks necessary to assure that the data, in their final use form, meet these requirements.

Each variable must be addressed in terms of measurement method or instrument type, sensor siting, data handling (especially averaging or editing), and representativeness. The question of representativeness has many facets. First, one must be sure that the measurement itself has no bias or that the bias is understood. Given an unbiased measurement at the sensor location, one must be sure that location is what the use requires. Finally, the hourly value used should represent the time period the use requires. For example, if a back-trajectory analysis is needed to estimate the volume location from which the air quality instrument was sampling, the hourly wind data should be a vector average for the hour and not an instantaneous or few-minute average taken once an hour.
Quality Assurance Considerations in Conducting the Ames Test
Authors: Williams LR
Published: December 2008

This paper provides general and specific guidance for the development and implementation of a quality assurance program for Ames testing. An effective quality assurance program is needed to assure that data produced from short-term mutagenicity testing (e.g., the Ames test) are of known quality and comparable among laboratories conducting the testing. The success of such a program begins with a personal and organizational commitment to data quality. Next, standardized procedures for the conduct and control of the testing process should be adopted and rigidly followed. Finally, participation in an external quality assurance program is necessary for independent confirmation of testing performance and confirmation of interlaboratory data comparability. Comparability of test data is required if there is to be confidence in the results of testing activities and acceptance of the resulting interpretation of test findings.

Detailed quality control procedures are outlined for the Ames test. These include procedures for confirming the genotype and responsiveness of tester strains, confirming the absence of bacterial contamination, providing appropriate positive and negative test controls, confirming the enzymatic activity of metabolic activators, and determining the adequacy of test data.

The functions and responsibilities of an effective quality assurance program are outlined. Primary functions include development of standards based upon technically attainable criteria, assistance to participating laboratories in adopting those standards, and independent evaluation of the success of the laboratories in meeting those standards.
The Use of Natural Waters as U.S. Geological Survey Reference Samples
Authors: Janzer VJ
Published: December 2008

The U.S. Geological Survey conducts research and collects hydrologic data relating to the Nation's water resources. Two water quality laboratories in Atlanta, Georgia, and Denver, Colorado, support the national research programs, and provide chemical analyses of natural waters for the data program. Additional chemical water quality data are provided by cooperator and contract laboratories.

Continuous quality assurance efforts with these laboratories require several thousand reference samples each year. Reference samples approximating actual field samples provide the most realistic quality assurance for the laboratories. Seven types of natural matrix reference water samples are prepared for use in the Survey's quality assurance program. These include samples containing major constituents, trace metals, nutrients, herbicides, insecticides, trace metals in a water and suspended-sediment mixture, and precipitation (snowmelt). To prepare these reference samples, natural water is collected in plastic drums and the sediment is allowed to settle. The water is then filtered, selected constituents are added, and if necessary the water is acidified and sterilized by ultraviolet irradiation before bottling in plastic or glass. More than 1000 1-L samples of a given type may be prepared at a time. These reference samples are distributed twice yearly to more than 100 laboratories for chemical analysis. The most probable values for each constituent are determined by evaluating the data submitted by the laboratories using statistical techniques recommended by ASTM.

A stockpile of several thousand reference samples is maintained by the preparation of new samples as needed. Periodically, some of these samples are submitted to laboratories as “unknowns”. When the analytical data for these samples are reported and evaluated, problem areas detected are promptly reported to the respective laboratory.

Use of both identified and unidentified reference samples provides some of the quality assurance data necessary to ensure the continuing accuracy of chemical analyses obtained to support the Survey's basic water-data collection and research program activities.
Development and Distribution of Reference Materials for Ambient Air Measurements
Authors: Mitchell WJ , Puzak JC
Published: December 2008

The procedures used and the costs incurred in developing and distributing Reference Materials for use in air monitoring programs are discussed. Reference Materials currently available for use in determining the quality of ambient air measurements are described in relation to type, source, cost, and concentration. Ongoing and planned programs to develop new Reference Materials are described.
Compaction Equipment for Asphalt Mixtures
Authors: Geller M
Published: December 2008

The development of different types of compaction equipment over the past 30 years is briefly reviewed. Certain types of static steel wheel rollers and certain sizes of pneumatic rollers are shown to have lost ground to vibratory rollers for asphalt pavement compaction. An empirical method is presented for purposes of comparing the linear-load rating for static steel wheel rollers with the contact pressure rating of pneumatic tire rollers, with the indication that both types are capable of the same range contact pressures in practice. The dynamic effect of vibration is discussed to indicate the economic benefits of vibratory rollers providing they are properly used. The various limitations of each basic type of asphalt compaction equipment are also discussed. The inability to predict material behavior before running the roller pattern is mentioned in terms of recent developments in end result specifications, nondestructive testing, and statistical sampling control. The paper concludes that compaction problems of the past, present, and future can result not only from improper application of compactors, which is correctable with training and education, but also from inability to predict unsuitable mix behavior for compaction. This lack of predictability combined with problems of mix confinement will continue to cause compaction problems, but such problems are not compactor related.
Reliability Evaluation of Sampling Electrorefined Copper Cathodes
Authors: Hsu YT , Starbuck FL
Published: December 2008

The reliability of routine cathode sampling procedure at Nassau Recycle Corporation was evaluated. The evaluation was conducted on both in-house and supplier's cathodes. Sampled cathodes were charged into the shaft furnace to make continuous cast wire rod, and the analyses of the cathodes and the rod from the same batch were compared. Test results indicated a good correlation between the cathode analysis and the composition of the wire rod for both in-house and suppliers' cathodes. The good correlation may be attributed to the low and fairly uniform distribution of impurities in these cathodes.
Sampling of Copper Cathodes
Authors: Lamela M , Palacios C
Published: December 2008

In order to devise a system for the sampling of copper cathodes using a mechanical punch it was first necessary to establish the distribution of impurities between individual samples and their location. To do this a cathode was divided into 171 pieces and each piece melted individually. Samples for analysis were then taken from the melt by suction through a 3.8-mm-ID glass tube and analyzed for impurities by emission spectrometry. The results obtained were summarized and studied statistically to determine the average content and standard deviation.

It was then essential to correlate this information with the results obtained when sampling plant production using a mechanical punch. For this purpose a total of 578 cathodes (60 tonnes) was sampled, a template was used to locate 30 sampling points across the diagonal of a cathode, and 5 buttons were taken from each cathode in such a way that all 30 sampling points were punched an equal number of times. The 5 buttons from each cathode were melted, sampled and analyzed in a similar manner to that used for the sampling of the individual cathode. These results were also studied statistically, and in combination with the first results an overall standard deviation was determined statistically under various combinations of number of cathodes selected, number of buttons from each sample cathode, and number of samples per final sample.

From this work it has been determined that, at this particular plant, it is satisfactory when sampling a lot of approximately 60 tonnes to punch 5 buttons from each of 6 selected cathodes, to melt the 30 samples together, and to figure an arithmetic average of 3 analyses of the sample taken from the resultant melt.
Analysis of Cathode Sampling and Analytical Variance of Electrowon Copper
Authors: Kline JT
Published: December 2008

This paper summarizes the findings of a study of sampling and analytical variance associated with various grades of electrowon copper produced at Noranda's Lakeshore Mine. Production control sampling methods, cathode analyses, variability of precision and accuracy of cathode analysis as a function of cathode quality, and analytical methods are discussed. A general review of customer sampling methods and the effect on settlement assays is included. Also discussed are on-site cathode production analyses and their relationship to wire bar product analyses.
Characterization of High-Purity Cathodes for Plant Control and Marketing Purposes
Authors: Hunter TC , Mitchell RJ
Published: December 2008

The distribution of some key impurities in high-purity copper cathode was found to be significantly biased towards edges of the cathodes. It is therefore necessary that the laboratory sampling technique applied to primary sampled cathodes proportionately contain edge materials. Even with high-purity cathode lots, variation within and between cathodes in the lot is large; thus sampling accuracy requires that both primary sampling frequency and the laboratory sampled portion of whole cathodes be relatively high compared with most other metallic materials. There appears to be no low-frequency simple sampling procedure that is a reliable in-plant indicator of general quality.
Simultaneous Multielement Determination of Trace Metal Impurities in Refined Copper by Argon Direct-Current Plasma Atomic Emission Spectroscopy (DCPAES)
Authors: Jordan DE
Published: December 2008

Development of the stable argon direct-current plasma atomic emission spectrometer has provided a rapid alternative technique for the simultaneous multi-element analysis of refined copper for trace metal impurities. The trace metals (bismuth, arsenic, antimony, selenium, tellurium, iron, tin, lead, and nickel) are determined in various refined copper matrices. Results of analyses of National Bureau of Standards' Standard Reference Materials 457 and 494–496 for trace metals agree well with the certificate values. Results between direct-current plasma atomic emission spectroscopy and spark emission spectroscopy for production samples of refined copper also agree.
Transition of Part-Through Cracks at Holes into Through-the-Thickness Flaws
Authors: Grandt AF , Harter JA , Heath BJ
Published: December 2008

This paper describes results of a numerical and experimental study of the behavior of part-through cracks located at holes as they transition into uniform through-the-thickness flaws. Fatigue crack growth tests are conducted with transparent polymer specimens which allow the crack plane to be photographed during the fatigue test. Stress intensity factors are computed by the three-dimensional finite-element-alternating method for the measured crack shapes. Both analysis and experiment indicate that the crack growth rate varies along the flaw perimeter in a manner which encourages the trailing edge of crack advance to “catch up” with the leading edge. Once a uniform through-thickness configuration is achieved, the trailing point then slows down to the growth rate occurring at the point of maximum crack advance.
Part-Through Flaw Stress Intensity Factors Developed by a Slice Synthesis Technique
Authors: Saff CR , Sanger KB
Published: December 2008

Part-through-the-thickness flaws are the most common type of flaw occurring in metal structure. Accurate prediction of their growth is vital to ensure adequate life. The majority of stress intensity factor solutions for these flaws are developed through finite-element analyses, iterative techniques, or less accurate superposition of simple solutions. Recently the authors have developed and extended a slice synthesis technique for computation of stress intensity factors for part-through flaws. This technique is far less expensive than finite-element methods, yet provides excellent accuracy. This paper presents the derivation of the method and recently obtained solutions for surface flaws, corner cracks at holes, and corner cracks at the edge of plates in tension and bending. Simple analytical expressions have been fit to these solutions which can be incorporated into computer routines for crack growth prediction.
Dynamic Crack Branching—A Photoelastic Evaluation
Authors: Ramulu M , Kobayashi AS , Kang BS-J
Published: December 2008

A necessary and sufficient condition for crack branching based on a crack branching stress intensity factor, KIb, accompanied by a minimum characteristic distance of rc is proposed. This crack branching criterion is evaluated by dynamic photoelastic experiments involving crack branching of six single-edged notch specimens and six wedge-loaded rectangular double cantilever beam specimens. Consistent crack branching at KIb = 2.04 MPa√m and rc = 1.3 mm verified this crack branching criterion. The crack branching angle predicted by this crack branching criterion agreed well with those measured in the crack branching experiments.
A Failure Assessment Approach for Handling Combined Thermomechanical Loading
Authors: Bloom JM , Malik SN
Published: December 2008

This paper presents a failure assessment approach for the handling of combined thermomechanical loading of nuclear pressure vessels. The proposed approach is based on a failure assessment curve that accounts for the thermal and mechanical stresses in terms of the elastic stress intensity factor with a plastically corrected crack length. The square of this stress intensity factor divided by the effective elastic modulus is added to a J-integral deformation plasticity solution term. The result is valid for the full range of material/structural behavior, from linear elastic to fully plastic. The fracture behavior parameter, the total J-integral, can then be formulated in terms of a failure assessment curve to account for the combined loading states.

The proposed approach was benchmarked using a modified Babcock & Wilcox version of the ADINA computer program. The program generated incremental plasticity finite element crack solutions for a single edge cracked plate and a circumferentially flawed cylinder subjected to thermomechanical loadings. The ADINA finite element results agreed quite well with the proposed failure assessment approach.

The failure assessment approach is illustrated by a sample problem of a postulated accident condition, based on the occurrence of an overcooling transient (thermal loading) combined with an uncontrolled repressurization (mechanical loading) of a typical nuclear reactor vessel.
Fatigue Crack Growth Behavior of 7XXX Aluminum Alloys under Simple Variable Amplitude Loading
Authors: Bretz PE , Vasudévan AK , Bucci RJ , Malcolm RC
Published: December 2008

This investigation examines the influence of temper and purity on the fatigue crack growth (FCG) behavior of four 7XXX aluminum alloys (7075-T6, 7075-T7, 7050-T6, 7050-T7) tested using a periodic single overload spectrum at low stresses. The loading sequence consists of a periodic single overload spike occurring once every 8000 constant amplitude cycles; the overload spike is 1.8 times the constant amplitude load peak. All tests have been performed in high humidity (>90% relative humidity) air at a frequency of 20 Hz and a constant amplitude load ratio of R = 0.33. The observed microstructural effects on transient (that is, spectrum) FCG behavior are contrasted with those for steady-state (constant load amplitude) fatigue performance.
Effects of Specimen Configuration and Frequency on Fatigue Crack Propagation in Nylon 66
Authors: Lang RW , Hahn MT , Hertzberg RW , Manson JA
Published: December 2008

Fatigue crack propagation (FCP) rates were measured in nylon 66 as a function of test frequency using center-cracked-tension (CCT) and wedge-open loading (WOL) specimens. In order to enhance any effects of stress- and frequency-induced changes in the dynamic modulus and to maximize the capability for hysteretic heat generation, the nylon was equilibrated to a water content of 4.7% by weight. For this water content the glass transition region of the material occurs at around the fatigue test temperature. FCP rates determined using CCT specimens were found to be consistently higher at all frequencies than those using WOL specimens. In addition, hysteretic heat-up measured at the crack tip and across the whole unbroken ligament was higher in the CCT specimens. These results are related to the differences in the far field stress profiles and their effect on the relative specimen stiffness and on the heat generation capability. Effects of test frequency are discussed in terms of changes in strain rate and the beneficial and detrimental effects of local crack tip and general specimen heating.
Effects of Constraint Variation on the Fatigue Growth of Surface Flaws
Authors: Jolles M , Tortoriello V
Published: December 2008

Studies have shown that fatigue growth of semielliptic surface flaws in plates is not adequately predicted solely by stress intensity factor analysis. The variation in stress field triaxiality along the flaw border must be an important factor contributing to differences between predicted and observed fatigue crack growth behavior. An analysis is formulated to examine surface flaw fatigue growth accounting for constraint variation using the concept of crack closure. The extent of crack closure is quantified for plane stress versus plane strain conditions. Changes in the geometric parameters describing flaw size and shape are studied. Applications of the analysis are compared with experiments. The use of the concept of crack closure to account for constraint variation along the border of a surface flaw yields excellent results.
Temperature Dependence of Fracture Toughness of Large Steam Turbine Forgings Produced by Advanced Steel Melting Processes
Authors: Swaminathan VP , Landes JD
Published: December 2008

Three advanced steel melting processes—low sulfur vacuum silicon deoxidation, electroslag remelting, and vacuum carbon deoxidation—were applied to produce three Cr-Mo-V ASTM A470, Class 8 steel forgings for steam turbine application. Plane strain fracture toughness (KIc) values were obtained using 2T and 3T compact specimens between 24 and 93°C (75 and 200°F). The elastic-plastic fracture toughness (JIc) was obtained using 1T-CT and round compact specimens at 149, 260, and 427°C (300, 500, and 800°F). Both multiple specimen “heat-tint” techniques and single specimen “unloading compliance” techniques were employed at 149°C (300°F) to generate J-R curves. Both of these techniques yielded results with excellent agreement. Round CT specimen results agree well with standard CT specimen results.

These advanced technology forgings show significant improvement (factors of two to three higher) in fracture toughness over conventionally produced forgings. This increase in toughness is attributed mainly to the ability of these processes in producing cleaner steel, especially with very low sulfur content, and the associated reduction in the amount of nonmetallic inclusions. Minimums in toughness and the tearing modulus at 260°C (500°F) were observed. These minimums correspond to the occurrence of minimum in the tensile ductility at the same temperature which may be due to the dynamic strain-aging phenomenon.
Fracture Toughness of Stainless Steel Weldments at Elevated Temperatures
Authors: Garwood SJ
Published: December 2008

This paper comprises a study of the resistance to the propagation of a ductile tear in 316 stainless steel parent plate in all six orientations, and submerged-arc and manual metal arc weld metal and heat-affected zone (HAZ) regions in stainless weldments at 370 and 540°C. Tests were carried out in bending and tension in both load and displacement control at 370°C. The propagation resistances of the various regions are assessed from the measurement of resistance curves and maximum load toughness using both crack tip opening displacement (CTOD) and J-integral parameters.

The T-L orientation appears to have the poorest resistance to tearing of the four normal cracking orientations for parent plate. The S-L orientation, however, has the worst toughness overall. Heat-affected zone toughness of both manual and submerged-arc welds is equivalent to parent plate. Submerged-arc weld metal toughness is comparable with the T-L orientation in plate material. Manual metal arc weld metal toughness is inferior to the toughness exhibited by submerged-arc and the four normal cracking orientations in parent plate. Increasing the test temperature from 370 to 540°C for manual metal arc weld metal appears to produce a distinct increase in resistance to ductile crack propagation.

Provided adequate thickness constraint is ensured, maximum load toughness determinations from the standard laboratory three-point bend geometry would appear to give conservative estimates of tensile instabilities under load control. The relevance of this behavior is discussed in terms of the use of single-parameter design curve methods for the estimate of tolerable flaw sizes in structural applications
Influence of Inclusions on the Fracture Properties of A588A Steel
Authors: Wilson AD
Published: December 2008

The influence of nonmetallic inclusions on the fracture properties of A588 Grade A steel plate is investigated by evaluating one plate produced by conventional steel-making practices and another using calcium treatment. The two plates had differing inclusion structures and their characterization included: tensile, Charpy V-notch, dynamic tear, and J-integral testing; JIc, tearing modulus, and J-Δa and J-T curve determinations on the upper shelf; and fatigue crack propagation and near-threshold fatigue evaluations. Testing of up to six specimen orientations was used, depending on the testing method. Of all the test methods used in this investigation the JIc and J-T curve determinations were found to be the most sensitive to changes in inclusion structure in all testing orientations. The fatigue crack growth rate of the calcium-treated steel was primarily improved in the through-thickness (SL) orientation at higher ΔK levels. Testing at higher load ratios accentuated these differences. Oxide and roughness-induced crack closure had a significant effect on the near-threshold fatigue behavior of the conventional steel as a result of the inclusion-induced roughness on the fracture surface. Fractography and crack closure measurements were used to explain this behavior.
Effect of Fast-Neutron Irradiation on Fracture Toughness of Alloy A-286
Authors: Mills WJ
Published: December 2008

The effect of fast-neutron irradiation on the fracture toughness behavior of Alloy A-286 was characterized at 24 and 427°C using linear-elastic KIc and elastic-plastic JIc fracture mechanics techniques. The fracture toughness was found to decrease continuously with increasing irradiation damage at both test temperatures. In the unirradiated and low fluence conditions, specimens displayed appreciable plasticity prior to fracture, and equivalent KIc-values were determined from JIc fracture toughness results. At high irradiation exposure levels, specimens exhibited a brittle KIc fracture mode. The 427°C fracture toughness fell from 129 MPa√m in the unirradiated condition to 35 MPa√m at an exposure of 16.2 dpa (total fluence of 5.2 × 1022 n/cm2). Room-temperature fracture toughness values were consistently 40 to 60% higher than the 427°C values. Electron fractography revealed that the reduction in fracture resistance was caused by a fracture mechanism transition from ductile microvoid coalescence to channel fracture.
Wide Range Creep Crack Growth Rate Behavior of A470 Class 8 (Cr-Mo-V) Steel
Authors: Saxena A , Shih TT , Ernst HA
Published: December 2008

Wide range steady-state creep crack growth rate behavior of an A470 Class 8 steel was characterized at 538°C (1000°F) using constant load and constant deflection rate methods of testing. Both methods yielded mutually consistent results. Crack growth rates in the range of 10−4 to 10−1 mm/h were successfully correlated with the energy rate line integral, C*. Results are discussed in light of the recent analytical studies that have appeared in the literature for growing cracks in creeping materials. Various methods of determining C* for CT specimens are also discussed.
J-Integral R-Curve Testing of High Strength Steels Utilizing the Direct-Current Potential Drop Method
Authors: Vassilaros MG , Hackett EM
Published: December 2008

J-integral R-curve tests were performed on 1T compact specimens of 3Ni and 5Ni steels under both quasi-static and rapid loading. A direct-current potential drop technique was developed for the crack extension measurements. This technique accounted for specimen plasticity and correlated well with crack extension measurements determined from elastic compliance. Potential drop proved to be a valid technique for the determination of R-curves under rapid loading. Increasing the loading rate elevated the JI-R curves for both the 3Ni and 5Ni steels with respect to the quasi-static case.
Effect of Specimen Dimensions on Critical J-Value at the Onset of Crack Extension
Authors: De Roo P , Marandet B , Phelippeau G , Rousselier G
Published: December 2008

This paper presents the experimental results of a test program designed to evaluate the effect of specimen dimensions on the critical J transition curve. These tests were conducted, along with KIc measurements, on four quenched-and-tempered medium strength steels with 15 to 200 mm thick specimens. In the cleavage fracture domain, Jc yielded toughness values that overestimated KIc, especially with the smallest specimens. Although ASTM E 813 requirements were met, the cleavage to ductile tearing transition temperature increased with increasing the J-specimen size. The level of the ductile plateau was found to be strongly dependent on the uncracked ligament length. It is pointed out that JIc measurements may overestimate the plane-strain fracture toughness, the ASTM E 813 size requirements being not restrictive enough.