bluuebunny/crossref_metadata_2025 huggingface dataset:
Hydraulic Conductivity of Solidified Residue Mixtures Used as a Hydraulic Barrier
Authors: Pamukcu S , Topcu IB , Guven C
Published: March 2009

The feasibility of using a solidified product of steel process residue in construction of a barrier system was investigated in the laboratory and in-situ. A solidified product of the dewatered sludge residue, filter cake, which exhibited high strength and low hydraulic conductivity was considered as a barrier cap for an existing lagoon. Variations in the placement and curing methods in the field, along with additive composition of the base mixture, influenced the strength development, hydraulic conductivity and durability of the resulting material. Strength of the material did not correlate well with hydraulic conductivity. However, high material strength appeared to increase resistance to freeze-thaw effects, thus demonstrating resistance to deterioration of the desired low permeability. Compositional variations such as proportion of surface reactive agents, water to cement ratio and the proportion of cement influenced strength as well as the measured hydraulic conductivity in the laboratory. Finally, a comparative analysis of fraction of three heavy metals removed by water permeation of three different composite samples demonstrated that chemical processes during the solidification may play an active role in the performance of the final product. Three slightly different composites of fairly high strength and low hydraulic conductivity showed selective release of cadmium from the solidified material.
A Field-Scale Study of the Use of Paper Industry Sludges as Hydraulic Barriers in Landfill Cover Systems
Authors: Maltby V , Eppstein LK
Published: March 2009

Four field-scale landfill cover test cells have been constructed in order to facilitate a comparison of the field performance of sludge and clay hydraulic barriers. Two covers contain clay as the barrier material, one contains a paper mill primary sludge, and one contains a paper mill combined (primary and biological) sludge. One of the clay cells is designed to allow for a field verification study of the Hydrologic Evaluation of Landfill Performance (HELP) model.

Both sludge cells have produced smaller volumes of seepage and greater volumes of runoff than the clay cells to date. Calculated barrier hydraulic conductivities for the paper mill sludges are somewhat lower than those values calculated for the clay.
A Unified Creep-Plasticity Theory for Solder Alloys
Authors: McDowell DL , Miller MP , Brooks DC
Published: March 2009

Sn-Pb solders exhibit creep-plasticity interaction and significant strain-rate dependence at operating temperatures of electronic circuits. A major problem is fatigue and creep-fatigue interaction due to thermomechanical cycling. Reversed plasticity, creep, and creep-plasticity interactions dominate the behavior for these types of histories. Furthermore, thermal softening plays a strong role in the time dependence of the mechanical behavior. However, classical forms of decoupled plasticity and creep theories have been shown to be quite inferior for modeling cyclic plasticity, creep, and interaction effects. The goals of this study were to: (a) develop a thermomechanical unified creep-plasticity model which can characterize the response of solders, and (b) characterize a selected solder alloy through mechanical testing and correlation with the model across a range of strain rates, temperatures, aging times, and loading-unloading conditions.

Solder alloys in general are mechanically soft and are employed routinely at very high homologous temperatures. The microstructure is often unstable at normal circuit board operating temperatures and the extent of alteration to the microstructure is a function of the applied stress or strain, temperature, etc. Many alloys recrystallize below 77°F (25°C) and therefore can change with time at room temperature.

A program of characterization involving tension tests at various temperatures and strain rates, creep tests, cyclic loading tests, and tension tests after prior high-temperature exposure was pursued to develop a broad-based understanding of the behavior of eutectic Sn-Pb solder, the most commonly used industrial solder alloy. A model for thermomechanical temperature and rate-dependent behavior of metallic alloys has been developed. Many of the typical, complex behaviors of solders can be addressed with this model, including temperature dependence and strain-rate dependence, creep-plasticity interaction, viscous cyclic strain ratchetting, softening effects due to static thermal recovery, and potential effects of aging (microstructural changes due to exposure at high temperature).
Stress and Thermal Analysis of Resistance Temperature Detectors
Authors: Wilson DA , Katherisan A
Published: March 2009

In many industries the failure of temperature devices such as resistance temperature detectors (RTDs) are of significance to process control. Therefore, a study was instituted to evaluate these failures. RTDs from various manufacturers were monitored and periodically calibrated until failure. Sensors that developed open circuits were then examined. Upon examination of the sensors, it was found that failures were occurring at or near the solder connection between the platinum lead-out and copper wire. A two-dimensional (2-D) finite element analysis of this joint was then developed.

Finite element models were created to evaluate stresses at 100, 200, and 300°C. The thermal expansion mismatch between the wires joined by the solder results in high-stress gradients at the corners of the solder joint. Photomicrographs were produced of the joint failures with a scanning electron microscope to study the crack nucleation and propagation. Aging of the solder due to long-term temperature exposure may also play a key role in the fracture behavior. The need for improved joint design and special coating materials is of primary importance to improve the life of the solder joints in many applications. This will improve the reliability of the components.
Meeting Future Power Needs in Licensing Space
Authors: Rossin AD
Published: March 2009

The United States and the other nations of the world will need more electric power in the future. It is important to establish the principle that currently operating plants can continue to operate beyond their original 40-year license periods. The only component that really should influence this licensing decision is the ability of the pressure vessel to maintain assurance of integrity. Nuclear power operates in “licensing space”. It is different from most other technologies. To sustain operation, or ever to begin to build new nuclear plants in licensing space, we, the technologists, must document the answers to the critical questions of material performance over time.
Effects of Fission and Fusion Neutron Irradiations on Mechanical Properties and Defect Recovery Behavior in α-Iron
Authors: Aono Y , Kuramoto E , Yoshida N , Kurishita H , Kayano H
Published: March 2009

Comparison is made of data on mechanical properties of high-purity iron single crystals irradiated with fission neutrons at the Japan Materials Testing Reactor (JMTR) and 14-MeV D-T neutrons at the Rotating Target Neutron Source (RTNS-II) at low fluences below 1022 n/m2. Both irradiations below 363 K led to irradiation hardening and the suppression of a hump appearing on the temperature dependence of yield stress of unirradiated high-purity iron, which suggests that radiation-induced defects formed at low temperatures significantly influence thermally activated deformation of iron.

In the isochronal annealing experiments of yield stress, the RTNS-II-irradiated irons showed a high annealing resistance accompanied by three recovery stages: stage I (RT to 450 K), stage II (650 to 750 K) and stage III (900 to 950 K). Recovery stages of the JMTR-irradiated irons were observed in the temperature ranges of 500 to 600 K (state Ij) and 700 to 780 K (stage IIj), followed by no radiation effect above 800 K. These recovery stages, except for stage III, were explained from a series of annealing of interstitial clusters with size distribution. Defects responsible for stage III were associated with complex vacancy type defect-nuclear reaction products (helium or hydrogen).
Comparison of Drop-Weight and Instrumented Charpy Impact Test Results for Irradiated RPV Steels
Authors: Pachur D
Published: March 2009

Reactor Pressure Vessel (RPV) steels of different chemistry and specification were irradiated in the FRJ-1 research reactor at various neutron fluences. The irradiation temperature was 288°C. The results of instrumented impact tests of normal Charpy V specimens and the results of drop-weight tests are reported. Load signals of instrumented impact tests were evaluated and the transition temperatures of the different energy fractions were compared with the related Nil Ductility Transition Temperature (NDTT) measured by the drop-weight tests. It is shown that the NDTT is coupled with the impact energy fraction describing the ductile behaviour of the impact test. NDTT and RTNDT can be evaluated from the instrumented Charpy test alone. This requires testing temperatures to be achieved at which the total impact energy does not/does contain energy of the ductility fraction — similar to the break/no break criterion of the drop-weight test.
Effects of Neutron Irradiations at Temperatures Below 500°C on the Properties of Cold Worked 316 Stainless Steels: A Review
Authors: Van Duysen JC , Todeschini P , Zacharie G
Published: March 2009

Many components used in the pressure vessel of French pressurized water reactors are made of austenitic stainless steels : 316L for screws, 304L for core barrel and baffle assembly, etc. Among these components, the most irradiated ones undergo an average damage rate of about 1 dpa/an at temperatures which may reach about 400°C. Such irradiations may have very detrimental effects on the in-service behaviour of austenitic steels. In order to forecast these effects, Electricité de France has defined important programmes of studies. In the framework of these programmes, we have carried out a review concerning the effects of irradiations at relatively low temperatures (i. e. 500°C) on cold-worked 316 stainless steel. We were particularly interested in the evolution of microstructure as well as tensile (with or without notch), creep, fatigue (with or without creep) and fracture toughness properties. In some cases, we have also analysed the influence of cold-work level, irradiation temperature and test temperature. For some mechanical properties, the data was sufficient to qualitatively predict the properties of cold worked 316 stainless steels after long — term irradiations under PWR conditions.
Stress Corrosion Cracking Susceptibility of Irradiated Type 304 Stainless Steels
Authors: Chung HM , Ruther WE , Sanecki JE , Hins AG , Kassner TF
Published: March 2009

Slow-strain-rate tensile tests and microstructural analysis by Auger electron spectroscopy were conducted on specimens of high- and commercial-purity (HP and CP) heats of Type 304 stainless steel obtained from neutron absorber tubes and a control blade sheath after irradiation up to 2.5×1021 n∙cm-2 (E>1 MeV) in boiling water reactors (BWRs). The susceptibility of the HP absorber tubes to intergranular stress corrosion cracking (IGSCC) was higher than that of the CP absorber tubes or the CP control blade sheath. IGSCC susceptibilities of the BWR components could not be correlated with segregation of impurities on grain boundaries. However, for comparable fluence levels, the susceptibilities could be correlated to concentrations of Cr on grain-boundaries.
Isotopic Tailoring with 59Ni to Study Helium Generation Rates and Their Effect on Tensile Properties of Neutron-Irradiated Fe-Cr-Ni Alloys
Authors: Garner FA , Hamilton ML , Greenwood LR , Stubbins JF , Oliver BM
Published: March 2009

Tensile testing on three model Fe-Cr-Ni alloys removed from four discharges of the 59Ni isotopic doping experiment in FFTF-MOTA indicates that helium/dpa ratios typical of fusion reactors do not produce changes in the yield strength or elongation that are significantly different from those at much lower helium generation rates. It also appears that tensile properties approach a saturation level that is dependent only on the final irradiation temperature, but not prior temperature history or thermomechanical starting condition. The saturation in mechanical properties reflects a similar saturation in microstructure that is independent of starting condition.

The successful conduct of an isotopic doping experiment was found to require post-irradiation measurement of the helium levels in order to compensate for uncertainties in the cross sections for burn-out and burn-in of 59Ni and for uncertainties in neutron flux and spectra in the vicinity of the edge of the core.
The Effect of Phosphorus on the Microstructure of an Fe-16Cr-17Ni Austenitic Ternary Induced by Fast Neutron Irradiations
Authors: Watanabe H , Muroga T , Yoshida N
Published: March 2009

The effects of phosphorus on void swelling in austenitic stainless steels under fast neutron irradiation have been investigated. Three model alloys (Fe-16Cr-17Ni, Fe-1BCr-17Ni-0. 024P, Fe-16Cr-17Ni-0. 1P) were irradiated to 40 dpa in the Fast Flux Test Facility (FFTF) using Materials Open Test Assembly (MOTA). The irradiation temperatures were 679K, 793K and 873K. Addition of phosphorus resulted in a suppression in void swelling at all temperatures. At the higher temperatures (793K and 873K), radiation enhanced formation of M2P-type phosphides were observed. These phosphides are expected to act as strong defect sinks, causing suppression of void swelling at these temperatures. On the other hand, at the lower temperature (679K), the suppression of void swelling appeared to be related to the reduction of vacancy mobility by phosphorus addition.
High-Temperature Irradiation of Alumina-Base Ceramic Materials in a Water Cooled Fission Reactor
Authors: Shikama T , Narui M , Kayano H , Sagawa T , Tanabe T , Fujitsuka M
Published: March 2009

The so-called improved temperature-controlled irradiation was attempted at 1073 K with an electrical heater in a water cooled fission reactor and alumina-magnesia ceramics were irradiated. They were sintered from the highly pure powders without sintering-aid agents. Preliminary results indicated that re-crystallization or re-structuring took place during the high temperature irradiation. The alumina and the magnesia phases appeared in the nearly stoichiometric spinel of MgAl2O4 after the irradiation.
Influence of Overload and Temperature on Stress Corrosion Crack Growth Behavior in a Low-Alloy Steel
Authors: Venugopal V , Putatunda SK
Published: March 2009

An investigation was carried out to examine the influence of temperature and overload plastic zone size on stress corrosion crack (SCC) growth behavior in a low-alloy steel. Compact tension specimens with TL orientation prepared from SAE 4140 steel in hardened and tempered condition were used. Two pertinent variable conditions were chosen: (1) cold deionized water at 23°C and (2) hot deionized water at 80°C. The specimens were precracked in fatigue and then overloaded to various extent (5, 10, 25, and 50%). The SCC behavior of these specimens was studied, keeping them submerged in hot and cold deionized water.

The results of the present investigation demonstrate that the incubation period for crack growth decreases with increasing initial stress intensity factor and increasing temperature. The incubation period for crack growth was found to increase as an exponential function of the overload plastic zone size. In overloaded specimens, once the crack growth initiated, the crack growth rate was observed to be much higher than in the non-overloaded specimens. The crack growth rate in Region I was found to increase with increasing initial stress intensity factor andtemperature. The crack growth rate in Region II was also found to increase with temperature, but was independent of the stress intensity factor.
Effects of Electrochemical Potential on the Slow Strain Rate Fracture of 4340 Steel in a Combustion Product Residue
Authors: Daniels RD , Sadarangani AP , Magner MS , Kennelley KJ
Published: March 2009

Steel breech chambers in cartridge-ignition aircraft engine starters have failed in service by fracture of the chamber dome during firing. The interior surface of the dome is subject to corrosion because of accumulation of combustion products and moisture behind heat shields in the chamber. The residue collected from behind the heat shields of 25 used but still serviceable breech chambers was employed as an environment for slow strain rate tension tests of 4340 steel heat treated to the strength of the chamber. The residue contained ammonium chloride, potassium chloride, and the oxides of iron as major components. The slow strain rate tests were carried out at controlled electrochemical potentials both anodic and cathodic to the corrosion potential of -550 mV SCE (saturated calomel electrode). The tests demonstrated that the corrosion potential is at the edge of the stress-corrosion cracking potential range for the steel in this environment. Thus, stress-corrosion cracking appears to be a factor in service failures of the chambers.
A Model for Environmentally Assisted Crack Growth Rate
Authors: Gabetta G , Rinaldi C , Pozzi D
Published: March 2009

A superposition model for corrosion fatigue formulated for reactor pressure vessel (RPV) steel is described in this paper. The three components of crack growth rate are associated to pure fatigue, true corrosion fatigue, and stress corrosion.

The true corrosion fatigue behavior can be correlated with the material properties with regard to the resistance to generalized corrosion: the stress corrosion behavior can be correlated to the stress corrosion susceptibility of the material/environment couple.

While in pure fatigue and true corrosion fatigue the crack growth rate is depending on the applied ΔK (following Paris law), the stress corrosion component is time dependent. The onset of the stress corrosion component is associated with a critical ΔK (ΔKC), whose is depending on frequency.

The meaning of ΔKC is discussed and compared with the classical stress corrosion parameter KISCC.

The good prediction obtained for RPV steels suggests to extend this approach to other materials; an application to AISI 304 stainless steel is proposed.
Evaluation of KISCC and da/dt Measurements for Aluminum Alloys Using Precracked Specimens
Authors: Domack MS
Published: March 2009

The results of an interlaboratory program conducted to evaluate variability in measurements of the threshold stress intensity factor (KISCC) and stress corrosion crack growth rates (da/dt) for aluminum alloys are summarized. Precracked specimens machined from 7075-T6 aluminum alloy plate are exposed to a 3.5% NaCl (sodium chloride) solution by eleven participating laboratories. The effects of specimen configuration, starting stress intensity level, precracking procedure, and surface grooving are statistically evaluated, and sources of both interlaboratory and intralaboratory variability are identified. Data analysis indicates that variations in crack growth rates were related to difficulties associated with visual crack length measurements, especially on face-grooved specimens, and that more effective measurement techniques would more accurately characterize stress corrosion crack growth. In addition, test duration should be determined systematically, accounting for crack length measurement resolution, time for crack arrest, and experimental interferences. Variations in KISCC were related to the procedure used to measure the final bolt load. Final load measured by specimen reloading did not correlate well with that determined by compliance and appeared sensitive to factors such as corrosion product wedging and metallurgical features on the stress corrosion crack faces. Miniature instrumented load cells were used in several tests in a parallel program to monitor load relaxation during specimen exposure and to provide an indication of final load prior to specimen reloading. The load cell output during specimen exposure indicated that perturbations observed in crack length versus time curves may be related to real changes in load and should not be considered due only to crack length measurement difficulties. Compliance solutions were experimentally determined for both modified compact and double-beam wedge loaded specimens with different face-groove geometries and the results compared with published solutions. Both crack-mouth and load-line crack opening displacements were measured, and the data were used to define a relationship to correlate deflections at these measurement locations. The resulting relationship is compared with a previous solution determined by boundary collocation. No significant statistical variation in KISCC was observed with regard to specimen type, surface grooves, or specimen orientation, indicating both specimen configurations are suitable for stress corrosion testing and differences in KISCC determination were attributed to test procedures. Results of both the interlaboratory program and the additional studies should provide important contributions toward the development of a standard test method for stress corrosion testing and analysis using precracked specimens.
Cyclic Tension Corrosion Fatigue of High-Strength Steels in Seawater
Authors: Jones WJD , Blackie AP
Published: March 2009

Four low-alloy steels with nickel contents varying from 0.2 to 4.0% (BS 970:722M24, 817M40, 976M33, and 835M30) quench hardened and tempered to give yield or 0.2% proof strengths of approximately 800 MPa were tested in cyclic tensile loading (R = 0.05) at a frequency of 0.167 Hz in plain and notched (SCF = 2) forms in air, freely corroding in ASTM synthetic seawater (temperature 8°C and pH 8.2) and with cathodic protection of - 850 mV and - 1050 mV to establish S-N data for offshore platform design.

The steels suffered considerable reductions in fatigue performance in the freely corroding condition. Cathodic protection at — 850 mV improved the performance of all four steels and in one case (817M40) restored it to that in air. Notched specimens were not improved to the same degree as plain specimens.

Cathodic protection at - 1050 mV fully restored the fatigue performance of plain and notched steel 817M40 but the others showed a reduction in performance due to intergranular cracking in initiation and early crack propagation life in place of the otherwise ductile transgranular fracture; this was attributed to hydrogen absorption.
Wide-Plate Testing of Weldments: Introduction
Authors: Denys RM
Published: March 2009

No one single source currently exists which gives an overall picture of the meaning and usefulness of wide-plate test data. The intent of this series of papers is to provide a summary of the status of available knowledge—attained by the author as the result of almost 20 years of experience and study of the literature in the field of wide-plate testing—relating to the prevention of (brittle) fracture initiation.

In terms of organization, this series of papers begins with a short general introduction to show why the papers were written. The wide-plate test is then reviewed from various viewpoints. As the reader will see, the subject is presented in three self-contained papers, bearing the following titles: Part I—Wide-Plate Testing in Perspective Part II—Wide-Plate Evaluation of Notch Toughness Part III—Heat-Affected-Zone Wide-Plate Studies

Part I is concerned with a brief review of the historical development of wide-plate testing in relation to the major achievements of wide-plate/small-scale test correlations. From these considerations, the future role of wide-plate tests in fracture performance evaluations and design practice are discussed. Part II presents the various wide-plate and defect designs for evaluating the overall stress/strain behavior of plain and welded plates. Furthermore, the performance requirements in relation to the purpose of the test are critically reviewed. Part III considers the present state of the art in heat-affected-zone wide-plate testing procedures. The presentation provides a step-by-step analysis of the actual testing requirements. Particularly, emphasis is given to detailed metallographic posttest validation requirements for the crack tip location.
A Rational Development of Lamina-to-Laminate Analysis Methods for Fibrous Composites
Authors: Peterson DA , Hart-Smith LJ
Published: March 2009

This paper addresses the issue of analytically predicting the strength of cross plied composite laminates on the basis of effective, rather than measured, lamina properties. In particular, the typically nonlinear transverse properties are replaced by linear elastic properties with secant moduli selected to predict the correct strength when the transverse strains match the longitudinal strain of the fibers at failure. The basic lamina-to-laminate theory is the classical linear model for predicting Young's moduli and Poisson's ratios. However, the usual one-phase homogeneous model of orthotropic laminae for strength predictions is rejected as inappropriate for fiber-reinforced resin matrices. Failure occurs in one constituent or the other, and not in accordance with any homogenized mathematical theory. The theory developed here is a pseudo-single-phase model in which the fiber dominates under some stress states and the resin matrix may dominate under others. A complete two-phase theory is needed to account properly for matrix-dominated failures and residual thermal stresses. The theory is illustrated with extensive examples of carbon-epoxy cross-plied laminates but, with appropriate different choices of material properties, it can be applied to almost any fiber-reinforced composite.
Fatigue Growth, Deflections, and Crack-Opening Displacements in Cracked Lap Shear Specimens
Authors: Poursartip A , Chinatambi N
Published: March 2009

Results are presented for a cracked lap shear AS4/3501-6 unidirectional laminate geometry, with a strap thickness of 2.19 mm and a lap thickness of 1.17 mm. There is some fiber bridging across the delamination crack surfaces, which can lead to lower than expected compliance values and crack arrest in fatigue. Analysis of the fatigue crack growth rates in terms of the energy release rate range yields an exponent of 6.02 in the power law, and no apparent mean load influence. However, analysis in terms of the applied load suggests a large mean load influence. Deflections and crack-opening displacements (COD) near the crack tip were measured successfully with adequate resolution. The crack remains closed up to a load of 5000 N, corresponding to a strain energy release rate of 29 J/m2 and a crack growth rate of 10-7 mm/cycle. In principle, COD results can be used to determine the Mode I energy release rate, but the results presented here were not of sufficient accuracy.
Comparison of Metrological Techniques for Charpy Impact Machine Verification
Authors: Schmieder AK
Published: March 2009

Different measuring techniques were used to determine some of the specified characteristics of nine Charpy impact machines. In general, the techniques used were specified or recommended by one or more national standards. For example, the elevation of a raised pendulum was determined by direct measurement with a ruler and also by calculation from the measured angle of the pendulum rod. Both methods gave equal values with about the same reproducibility. On the other hand, significant differences were found when the friction loss in the pendulum was measured by a single swing and by multiple, successive swings. Significant differences in the period of oscillation were also found when the maximum angle of swing was 15 degrees as compared with 5 degrees. Both values were specified as permitted maximums in some national standards.
Quantitative Comparison and Evaluation of Various Notch Machining Methods and How They Affect ASTM E23 and ISO R442 Testing Equipment Results
Authors: Fink DA
Published: March 2009

The differences obtained when conducting Charpy impact tests using an ASTM method E23 specification, versus the ISO type impact tester have been reported with little agreement upon the comparisons. There has also been historically much controversy as far as the proper method of machining the notch into the Charpy specimen. This paper compares the effects of the two different types of impact testing equipment and evaluates machining of the notch by the methods of grinding, broaching and milling with a single toothed fly cutter.

It was determined that results obtained with the ISO type impact machine were elevated by approximately 4%. It was also determined that a slightly lower impact value was obtained with broached specimens. Photomicrographs of typical notch profiles were also obtained.
Cumulative Creep-Fatigue Damage Evolution in an Austenitic Stainless Steel
Authors: McGaw MA
Published: March 2009

A model of cumulative creep-fatigue damage has been developed which is based on the use of damage curve equations to describe the evolution of creep-fatigue damage for four basic creep-fatigue cycle types. These cycle types correspond to the four fundamental cycles of the StrainRange Partitioning Life Prediction approach of Manson, Halford, and Hirschberg. A concept referred to as Damage Coupling is introduced to analytically account for the differences in the nature of the damage introduced by each cycle type. For application of this model, the cumulative creep-fatigue damage behavior of Type 316 stainless steel at 816°C has been experimentally established for the two-level loading cases involving fatigue and creep-fatigue, in various permutations. The tests were conducted such that the lower life (high strain) cycling was applied first, for a controlled number of cycles, and the higher life (lower strain) cycling was conducted at the second level, to failure. The proposed model correlated the majority of the observed cumulative creep-fatigue data.
Application of a Thermal Fatigue Life Prediction Model to High-Temperature Aerospace Alloys B1900 + Hf and Haynes 188
Authors: Halford GR , Saltsman JF , Verrilli MJ , Arya V
Published: March 2009

This paper presents the results of the application of a newly proposed thermomechanical fatigue life prediction method to a series of laboratory TMF results on two high-temperature aerospace engine alloys: cast B1900 + Hf and Haynes 188. The method, referred to as TMF/TS-SRP, is based upon three relatively recent developments: the Total Strain version of the method of Strainrange Partitioning (TS-SRP), the bithermal testing technique for measuring TMF behavior, and advanced viscoplastic constitutive models. The high-temperature data reported in a companion paper are used to evaluate the constants in the model and to provide the TMF verification data to check its accuracy. Predicted lives are in agreement with the experimental lives to within a factor of approximately 2.
Elevated Temperature Crack Growth in Aircraft Engine Materials
Authors: Nicholas T , Mall S
Published: March 2009

Crack growth rate characteristics in Inconel 718 and a Ti3Al titanium aluminide alloy are compared at 650°C under conditions of cyclic loading and superimposed hold times at maximum load. Whereas a decrease in frequency increases the growth rate in both materials, addition of hold times has different effects in the two materials. Hold times increase the growth rate in Inconel 718, but cause anywhere from a slight increase to a very slight decrease in growth rate in Ti3Al, depending on the cyclic frequency. A simple empirical model is proposed which accounts for crack growth retardation due to creep blunting from hold time effects and considers the environmental degradation of the material with exposure time. The model is seen to provide reasonable capability to reproduce most of the growth rate characteristics observed experimentally while using the stress intensity factor, K, as the correlating parameter.
Near-Threshold Fatigue Crack Growth Prediction under Spectrum Loading
Authors: Sunder R
Published: March 2009

A constant crack closure stress-based model assuming the absence of a threshold stress intensity range under spectrum loading forms the basis for a simple procedure to predict crack growth under spectrum loading. The procedure requires material constants that can be derived from constant amplitude fatigue crack growth tests at two stress ratios: (1) at a high stress ratio in the absence of fatigue crack closure, and (2) at a stress ratio corresponding to the most severe cycle under the load spectrum of interest. Crack growth estimates were compared with available experimental data for a variety of materials and load spectra.
Contribution of Individual Load Cycles to Crack Growth under Aircraft Spectrum Loading
Authors: Sunder R
Published: March 2009

Fatigue crack growth in airframe materials under a variety of aircraft wing load spectra is numerically analyzed using a simple crack closure based model. An integrated load/damage-exceedance diagram is used to graphically describe the load spectrum as well as crack growth damage distribution. Characteristic features of crack growth damage contribution from individual load cycles are associated with the nature of the load spectrum. The significance of fatigue crack closure and its impact on damage distribution are studied.
Fatigue Crack Growth from Narrow-Band Gaussian Spectrum Loading in 6063 Aluminum Alloy
Authors: Veers PS , Van Den Avyle JA
Published: March 2009

Constant amplitude and narrow-band Gaussian loadings are applied to extruded 6063 aluminum crack-growth specimens in an effort to characterize the effective stress intensity levels during random loading. Crack-growth rates are determined for constant amplitude loadings at stress ratios (R) of 0.09, 0.3 and 0.5, and for a variable amplitude loading simulated to match a narrow-band Gaussian spectrum. Crack-opening stress levels measured by the compliance method during the constant amplitude loading are found to differ substantially for -T5 and -T6 heat treatments due to a change from intergranular to transgranular crack growth. Crack-opening load ratios correlate well with the maximum applied stress intensity factor, Kmax, for the -T5 material. The Kmax dependence leads to an effective halving of the crack-growth exponent. Calculated variable amplitude lives are much shorter when this correlation is taken into account (an acceleration effect) and show a greater difference between loading blocks condensed by racetrack filtering at threshold levels of two and four standard deviations, similar to what was observed in the tests. Crack-opening-load measurements in one specimen with the narrow-band Gaussian (variable amplitude) loading failed to detect any closure. A substantial difference in the closure behavior of nominally identical R = 0.3 tests indicates that closure may occur irregularly in the extruded aluminum. Calculated crack-growth lives, assuming no closure in the variable amplitude tests, are much shorter than the test results. Including closure in the variable amplitude loadings greatly improves the predictions.
Electric-Potential-Drop Studies of Fatigue Crack Development in Tensile-Shear Spot Welds
Authors: Swellam MH , Kurath P , Lawrence FV
Published: March 2009

The development of fatigue cracks in galvanized low carbon and high-strength-low-alloy steel, tensile-shear-spot weldments was investigated using a d-c electrical-potential-drop technique which sensed the depth of fatigue cracks as they propagated through the thickness of the specimens. These resistivity changes were correlated with the actual crack depths measured on sectioned specimens. This correlation was used to identify lives at which certain crack depths were achieved: the duration of Stage I (initiation) corresponded to a crack depth of about 18% of the sheet thickness (≈0.16 to 0.48 mm), and the duration of Stage II (through-thickness propagation) corresponded to a crack depth equal to the sheet thickness (0.89 to 2.72 mm). The final failure of the specimen determined the conclusion of Stage III (cross-width crack propagation).

The effects of sheet thickness, specimen width, and nugget diameter were studied. Sheet thickness was found to have the largest effect on fatigue life, while the nugget diameter had the least. The fatigue life of the galvanized high-strength-low-alloy specimens was found to be dominated by through-thickness propagation (Stage II), while the fatigue life of the galvanized low carbon specimens was dominated by Stage I. The fatigue life of all specimens tested at a given R ratio could be correlated with the initial value of stress intensity factor for the combined effects of Mode I and II loading conditions.
Reliability Centered Maintenance for Metallic Airframes Based on a Stochastic Crack Growth Approach
Authors: Manning SD , Yang JN , Pretzer FL , Marler JE
Published: March 2009

A Reliability Centered Maintenance Analysis (RCMA) method for determining structural inspection requirements, in terms of risk, is proposed for metallic airframes. Preventive maintenance tasks and inspection options can be evaluated using this method to ensure the operational readiness of airframes against the consequences of fatigue crack growth accumulation. The RCMA method, based on a stochastic crack growth approach (SCGA), can be implemented using: (1) deterministic crack growth analysis results, (2) an estimate of the crack growth life dispersion, (3) allowable risk rate, and (4) an estimate of the probability of a Class A mishap. It accounts for material properties, cracking resistance, stress level, load spectra usage variations, etc. Essential elements of the RCMA method are described and discussed. The RCMA is demonstrated for a structural control area from a full-scale metallic aircraft. RCMA results—their meaning, implications, and practical applications—are discussed in terms of current Air Force Aircraft Structural Integrity Program (ASIP) requirements.
What is a Geographic Information System(GIS)?
Authors: Dangermond J
Published: March 2009

Geographic information systems (GISs) and some of their major features are defined, the present status of some of the major technical elements of these systems are described, and some aspects of the standards appropriate to their technology are discussed. The history of GIS development is summarized and their present technological success is sketched. The present situation of each of their three major elements, computer hardware, computer software, and geographic data, is described. The major GIS hardware platforms (mainframes, minicomputers, workstations, microcomputers, and networked hardware), and their special peripheral devices (digitizers, plotters, scanners, etc.) are mentioned. GIS software is described, including its organization, major functions, and use in modeling and analysis in various applications. Their data and databases are described. Present major technological applications are listed and standards are discussed. The notion of GISs as “data integration machines” is introduced and implications are indicated.
Addressing Data Standards: The Northwest Land Information Systems Network
Authors: Wright RA , Yee M
Published: March 2009

The Northwest Land Information System Network (NWLISN) began in 1987, with an initial group of 11 Federal and State land management agencies developing a formal Charter and Memorandum of Understanding. The group has now grown to 19 agencies, is cochaired by the Bureau of Land Management (BLM) and the U.S. Geological Survey (USGS), and has several very effective pilot projects accomplished or underway. The purpose of the NWLISN is to promote interagency cooperation and cooperative activities on issues that impact land information systems (LIS) related issues in the Northwest, including joint funding of projects and solutions to regional problems. One of the major issues addressed by the group has been the need for data standards. Several pilot projects have addressed this problem and will be outlined in this paper. Pilot projects have demonstrated that cooperative efforts such as the NWLISN can have a strong effect on issues that impact their land management responsibilities, and in their collective use of LIS.
Geographic Information System Application Development for Utility Infrastructure Systems
Authors: Chang JC , D'Antoni JM , Pettersson CB
Published: March 2009

Application of data and information to solve municipal infrastructure problems and enhance system operation is the ultimate key to a successful geographic information system (GIS) program. This paper highlights a number of application issues to be considered in developing GIS application packages used in the planning, design, operation, and management of water resource and utility infrastructure systems. Some areas that require standardization in the application of GIS are also addressed.
Development of a Geographic Information System in Support of the St.-Lawrence Action Plan
Authors: Lamarche A
Published: March 2009

The continuous degradation of the quality of the St.-Lawrence river has been a major concern of the federal and provincial authorities in Canada. In order to correct the situation, the federal government has put forward in 1988 the five year St.-Lawrence Action Plan. The St.-Lawrence Centre was created to manage a part of the plan. The development of a decision support system based on geographical information system (GIS) technology was recognized as an important need for the St.-Lawrence Centre early in the plan. A description of the users and major operational needs is given, followed by the elaboration of a data structure and description of the system design. The system was developed on microcomputers with a “modular data-set” approach. The data structure is conceptually very close to an object-oriented database, where each dataset can be considered as an object with spatial, temporal, quantitative, and qualitative attributes. In the prototyping stage, the system comprises a collection of loosely connected datasets of raster based maps linked via small programmed interfaces to attributes managed by a relational database. Documentation of each dataset and related map construction is maintained in a relational database. Future developments will address the problem of temporal data, consolidation of the database due to the implementation of environmental monitoring networks, amelioration of the user interface and use of multimedia technology to integrate text, image, and sound.
Updating a Land-Planning Database from Landsat-5 Thematic Mapper Data
Authors: Blaser TJ , Lyon RJ P , Lanz K
Published: March 2009

Lansat-5 Thematic Mapper (Landsat-5 TM) images are evaluated for their use to upgrade a land-cover/land-use database in Switzerland. The Hectometric Information Grid or Hectaraster consists of a database, covering all of Switzerland according to 12 Level-I landcover/land-use categories. In this study Level-I and Level-II “build-up” and “forest” classes are computed using Landsat-5 TM spectral data of the study area of Switzerland. A procedure has been developed that automatically determines the dominant land-cover/land-use inside each hectare or “hectel” of the Hectaraster. The newly created Hectaraster results in a more accurate representation of the actual land-cover/land-use situation in the Nyon test area, as compared to the traditional 1972 Hectaraster. Also, more detail is available, since Level-II categories have been added to the Level-I land-cover/land-use categories.

The study indicates how classified Landsat-5 TM images can efficiently contribute to the management and planning of low density build-up zones. The integration of classified remote-sensing data into a geographic information system (GIS) allows the extraction of new land-use categories by examining their spatial relationships. Thus, in addition to built-up categories, computed from automated classification procedures, potential construction sites and nonused construction areas have been determined through GIS operations.

Methods are presented, which allow the classification of forest stands according to their surface and their shape. The perpendicular vegetation index (PVI) is computed for deciduous and coniferous forest stands. Deciduous and coniferous forests are studied separately. Coniferous forests revealed essentially low PVI values. Dense deciduous forest had the highest PVI values, while open deciduous and deciduous/coniferous stands had intermediate PVI values.
Development and Analysis of Cement-Coated Aggregates for Asphalt Mixtures
Authors: Bayomy FM
Published: March 2009

Aggregate quality has a central role in the performance of hot mix asphalt concrete (HMAC) mixtures. The availability of good quality aggregates is of concern in many countries including the U.S.A. One of the solutions to the aggregate depletion problem is to upgrade and improve the properties of the available abundance of marginal aggregates. This paper introduces a new aggregate upgrading technique for the use in HMAC mixtures. The proposed technique is referred to as “Cement Coating Technique” (CCT). The CCT addresses the surface texture of aggregate particles and improves the bond between the particle surface and the asphalt binder. The concept of the CCT is based on shielding the surface of the aggregate particles by a hydrated Portland cement film. The new cement coated aggregates can then be used in asphalt mixtures following the usual mix procedures. Asphalt concrete mixes made with cement coated aggregates are referred to as “CEMPHALT” mixtures. Cement content, water cement ratio and hydration time were found to be the three main parameters influencing the coating process. The optimum values of these parameters were determined. Performanceevaluation of CEMPHALT mixtures indicated significant improvements achieved in permanent deformation, fatigue and moisture damage resistance.
Effects of Aggregate Properties on Flexible Pavement Rutting in Alabama
Authors: Parker F , Brown ER
Published: March 2009

Pavement rutting which results in a distorted pavement surface is the accumulation of permanent deformation in all or a portion of the layers in a pavement structure. The objective of this study was to examine the effects of aggregate properties on the rutting of asphalt concrete mixtures. This objective was accomplished by analyzing rutting data from the Alabama Highway Department's pavement condition database. Field sites were evaluated and sampled and laboratory tests performed on aggregate from field samples.

Analyses of the Department's pavement condition database indicate that rutting in Alabama is increasing, and that this increase is attributable to either increased loading intensity or increased asphalt concrete rutting susceptibility. The analyses also indicate that rutting varies geographically and that this variation can be explained by quality of locally available aggregate. Those areas with crushed stone and angular natural sands are less susceptible to rutting.

Analyses of data from field test sites indicate that permanent deformation causing rutting is generally confined to the top 7 to 10 cm (surface and binder courses). There was little evidence that lower base/subbase courses or subgrade were significant contributors to rutting. A rate of rutting of 5.0 × 10-4cm/√ESAL or 2.5 × 10-7cm/ESAL delineated good and poor performing pavements.

Aggregate properties studied include: gradation, coarse aggregate percent fractured faces, and fine aggregate particle shape and texture. The correlation coefficients for most of these properties were low, however, there appeared to be definite trends. The poor correlations show that rutting is a very complicated process that is affected by multiple factors, and demonstrates the importance of both aggregate properties and asphalt content during material selection and mix design.