bluuebunny/crossref_metadata_2025 huggingface dataset:
A comparison of the Integrated Uptake Biokinetic Model to Traditional Risk Assessment Approaches for Environmental Lead
Authors: Chrostowski PC , Wheeler JA
Published: March 2009

The calculation of exposures to contaminated soil at Superfund sites has traditionally involved a steady state approach (the time-weighted average intake) which is uncalibrated and unvalidated, based on exposure factors which may be derived from risk management decisions, and which fails to take pharmacokinetics into account. Although the approach has some attractiveness from the standpoint of amenability to standardization and simplicity of operation, it has been criticized as being overly conservative, i.e. it yields chronic intake values which far exceed those actually measured through biological monitoring. Recently, USEPA has developed and published an alternative approach, known as the Integrated Uptake/Biokinetic (UBK) model for the determination of exposure to environmental lead. This model has two principal components -- one involving the uptake of lead into the body from different sources, the second involving the calculation of a blood lead level from the uptake. The blood lead level is subsequently used in conjunction with dose-response functions to predict the probability of adverse health effects. Unlike the average intake approach, it has undergone calibration and validation, is relatively free from risk management, and incorporates pharmacokinetics. The purpose of this paper is to present the results of a critical evaluation of the different approaches used to calculate exposure to lead.
The Compatibility of Slurry Cutoff Wall Materials with Contaminated Groundwater
Authors: Day SR
Published: March 2009

Slurry cutoff walls are frequently relied upon to block groundwater flows from toxic waste sites and landfills. The long-term effectiveness of slurry cutoff wall materials is critical to the successful containment of these facilities and the protection of groundwater resources. A variety of laboratory indicator tests have been attempted by engineers and academia to make compatibility determinations but at present there has been little published experience to show which tests produce meaningful results and how these tests can be used to demonstrate compatibility.

Hydraulic conductivity is a useful measure of chemica1/soil compatibility but permeability tests alone cannot assure the long-term stability of a slurry cutoff wall. A suite of indicator tests are used where the leachate and the proposed materials are combined and tested in immersion, desiccation, sedimentation, and other modes. Each indicator test attempts to model a different scenario of the slurry cutoff wall installation and operation.

This paper presents the experience of a specialty contractor from a number of projects, where an incompatibility was discovered and alternate materials were used to find a successful solution. Monitoring results from these sites has proven the effectiveness of the chosen solution. The laboratory test methods described are relatively simple and rely on worst-case scenarios, performed in a step-by-step process, that culminates with flexible wall permeability tests. Based on the methods described and the results from successful projects where these methods were used, engineers, owners and the public may better rely on long-term slurry cutoff wall performance with an increased level of confidence.
Swelling and Irradiation Creep of Neutron-Irradiated 316Ti and 15-15Ti Steels
Authors: Maillard A , Touron H , Séran J-L , Chalony A
Published: March 2009

The swelling and irradiation creep behavior of cold-worked 316Ti and 15-15Ti, two variants of austenitic steels in use as core component materials of the French fast reactors, are compared.

The use of 15-15Ti leads to a significant improvement due to an increase in the incubation dose for swelling.

The same phenomena observed in 316Ti are found in 15-15Ti. All materials that had not contained fuel that are samples, wrappers, or empty clad swell and creep less than real fuel pin cladding irradiated under the same conditions. To explain the swelling difference, as for 316Ti, a thermal gradient effect is invoked, but the irradiation creep difference is not understood. To predict the behavior of clad, it is essential to study defueled clad and to use specific rules.

All results confirm the good behavior of 15-15Ti, the best behavior being obtained with the 1% silicon-doped version irradiated up to 115 dpa.
Influence of Strain on Hydrogen Assisted Cracking of Cathodically Polarized High-Strength Steel
Authors: Scully JR , Moran PJ
Published: March 2009

Evidence is presented that confirms the role of mechanical strain in promoting surface absorption of hydrogen in two high strength steels under cathodic polarization in alkaline 3.5% sodium chloride solution. Data are reported for a 5Ni-Cr-Mo-V steel {896 MPa(130 ksi) yield strength} and is compared to data previously developed for AISI 4340 steel {1207 MPa (175 ksi) yield strength}. Strain induced bare surface generation is shown to substantially influence both alloys' hydrogen cracking susceptibility. Strain enhanced absorption is empirically observed for tensile specimens under slowly straining conditions and is also suggested to explain the hydrogen assisted cracking behavior of slowly strained DCB compact and cantilever beam fracture mechanics specimens with pre-existing fatigue cracks. Enhancement of hydrogen absorption per unit area of bare surface, as determined by straining hydrogen permeation measurements, explain the effect. In the presence of a corroded surface, the kinetics of the hydrogen evolution reaction are modified such that a lower cathodic hydrogen overpotential is observed at a given cathodic current density. This lowers hydrogen absorption at a given applied cathodic current density. Hydrogen permeation rates are increased upon straining independent of changes in the apparent bulk diffusion coefficient. These findings indicate that sustained plus cyclic loading and low-cycle fatigue of steels in seawater are more severe environmental cracking conditions than sustained loading typical of laboratory cantilever beam tests.
Procedural Considerations Relating to the Fatigue Testing of Steel Weldments
Authors: Booth GS , Wylde JG
Published: March 2009

Although fatigue design rules for welded steel joints are well developed, many cyclically loaded structures and components contain details that are not covered by these rules. It is often necessary, therefore, to generate fatigue data so that service performance may be rigorously assessed. However, for fatigue data to be of value, it is essential to identify and control many factors associated with the fatigue test itself.

The present paper summarizes the main parameters to be controlled when performing weldment fatigue tests. Four distinct areas are discussed—specimen design and fabrication, specimen preparation, testing, and, finally, reporting. Based on experience, recommendations are given regarding suitable practices in each of these areas.
Fatigue Crack Growth of Weldments
Authors: Link LR
Published: March 2009

Fatigue crack growth rate experiments were performed on compact tension specimens of base plate and weldments of 5456-H116 aluminum and of base plate and the heat-affected zone (HAZ) of ASTM A710 Grade A steel. Stress ratios for the tests were 0.1 for both materials, with the aluminum weld also being tested at R = 0.5. Crack opening levels were determined for both the weld and the base plate in the aluminum material and for the A710 material in the as-welded and stress-relieved conditions. The fatigue crack growth rates of the welds and HAZ, when the total applied load was used, were significantly less than those of plate for both materials. Using the effective stress intensity, which accounts for crack closure and thus represents the actual stress intensity at the crack tip, results in a shift of the da/dN versus ΔK curves to a faster growth rate. Comparison of the curves shows that the fatigue crack growth rates of the aluminum weld material fall in the same scatter band of data as those for base plate and that, for the A710 material, the HAZ shifts to faster growth rates than the base plate does. This shift of data leads to more accurate estimates on fatigue life, based on the intrinsic properties of the material.
Residual Tensile Strength of Graphite/Epoxy and Kevlar/Epoxy Laminates with Impact Damage
Authors: Cairns DS , Lagace PA
Published: March 2009

A study was conducted to examine the damage tolerance of composite laminates with impact damage. A model is presented to predict the residual strength of such laminates. The in-plane strain distribution near the region of damage is determined using Lekhnitskii's solution for an anisotropic inclusion in an anisotropic medium with compromised constitutive properties of the impact region used for the properties of the inclusion. The residual strength is then predicted using an average criterion based on strain. Results from experiments of impacted specimens of [±45/0]5 Kevlar/epoxy and [±45/0]25 graphite/epoxy show good correlation with the analytical predictions. The model is applied over a wide range of impactor conditions with equally good results. Although the damage was inflicted with different impactor masses, velocities, and laminate boundary conditions, the data indicates that the residual strength is only a function of the damage present and not the manner in which the damage is introduced. The use of the measured damage in conjunction with the predicted properties of the compromised region thus shows good promise for its application over a wide range of structures in a practical fashion. An overall analytical philosophy to deal with the problem of impact in composite laminates is discussed.
Thermomechanical and Bithermal Fatigue Behavior of Cast B1900 + Hf and Wrought Haynes 188
Authors: Halford GR , Verrilli MJ , Kalluri S , Ritzert FJ , Duckert RE , Holland FA
Published: March 2009

The high-temperature, low-cycle, thermal and mechanical fatigue behavior has been investigated for two high-strength, oxidation-resistant, superalloys used in aerospace propulsion systems. Experimental results were generated to support development of an advanced thermal fatigue life prediction method. Strain-controlled thermomechanical and loadcontrolled, strain-limited, bithermal fatigue tests were used to determine the fatigue crack initiation and cyclic stress-strain response characteristics of two superalloys, cast nickel-base B1900 + Hf and wrought cobalt-base Haynes 188.

Both in-phase and out-of-phase thermomechanical and bithermal fatigue experiments were conducted using computer-controlled, servohydraulic uniaxial fatigue machines equipped with diametral extensometry. The thermomechanical tests were conducted with triangular-wave diametral strain versus time and temperature versus time histories, with cycle times of 3 or 4 min. Bithermal experiments utilized a trapezoidal-wave temperature versus time profile wherein mechanical straining was imposed only during the isothermal portions at the maximum and minimum temperatures. Temperature was changed while the specimen was held at zero load, thus excluding mechanical strain application during thermal expansion straining. This testing procedure permits significantly more accurate partitioning of the mechanical and thermal expansion components of strain compared to conventional thermomechanical straining experiments. This is especially important when it is desired to further separate the mechanical strain into its elastic and inelastic components, the latter of which may be further partitioned into time-dependent and time-independent (creep and plasticity) components.

Bithermal temperatures of 483 and 871°C were employed for the cast B1900 + Hf nickel-base alloy and 316 and 760°C for the wrought Haynes 188 cobalt-base alloy. Thermomechanical fatigue tests were also conducted using maximum and minimum temperatures corresponding to those for the bithermal experiments. Lives cover the range from about 10 to 3000 cycles to failure. Comparisons are made with isothermal fatigue results obtained previously.
Nonproportional Fatigue of Welded Structures
Authors: Siljander A , Kurath P , Lawrence FV
Published: March 2009

Bending and shearing stresses in many structures are out-of-phase. A typical example is the evaluation of a fixed position in a bridge beam as a moving load crosses it. Traditional fatigue design approaches for welded structural details are generally based on inphase laboratory data. Thus the effect of nonproportional stress histories on the fatigue life of welded structural details is usually not considered. Stress-relieved tube-to-plate weldments were subjected to multiaxial in-phase and out-of-phase stress states using combinations of bending and torsion. The fatigue test results were evaluated using three local stress damage criteria modified for multiaxial loading. Finite element techniques were used to calculate the local stresses and strains. The local shear-stress based approach of Findley provided the best correlation of all test data for the loading paths considered. The unique aspects of nonproportional loading are reflected by the Findley model fatigue damage calculations, and the test data were correlated to within a factor of two. Since the scatter in the experimental data was also a factor of two for identical tests, further improvements in predictive ability are not possible. Also, the predicted direction of fatigue damage for the Findley model coincided with surface cracking characteristics.
Rheological Properties of Mineral Filler-Asphalt Mastics and Its Importance to Pavement Performance
Authors: Anderson DA , Bahia HU , Dongre R
Published: March 2009

The rheological and failure properties of eight asphalt-filler mastics were characterized using new testing techniques being developed within the SHRP program for testing asphalt binders. The mastics were prepared using four SHRP core asphalts and two fillers (calcite and quartz). The rheological measurements were used to construct rheological master curves and temperature shift functions. The failure properties were measured at different temperatures and strain rates and were shifted using time-temperature superposition to construct stress and strain-to-failure master curves. A subset of the mastics was also tested after oxidative aging with the pressure aging vessel (PAV) and after isothermal aging at low temperatures. The properties of the mastics were compared with the asphalt binder properties to describe the changes resulting from adding the fillers. The fillers were found to change the shape of the rheological master curves and to significantly increase the failure stress at all combinations of temperatures and loading times. The changes in rheological properties were observed only in the time dependency while the temperature shift functions showed only slight changes at the highest temperatures. The relative stiffening effects were observed to be asphalt-specific, especially at the lower frequencies or higher temperatures. Oxidative aging was shown to change the rheological type of the mastics, to be asphalt-specific, and to be independent of filler type. Physical hardening was observed to result in shifting the master rheological curves to longer loading times without affecting the shape of the master curves. The anticipated influence of mastic properties on the main distress types of asphalt pavements was considered. The influence of fillers on low-temperature cracking was hypothesized to be independent of filler type. Therefore, it is expected that the asphalt binder will control the cracking mechanism. Based on the energy concept, the addition of the filler is expected to improve resistance to stress-controlled fatigue while for strain-controlled fatigue the improvement, if any, is expected to be minimal. Fillers are expected to significantly improve rutting resistance as a result of increasing moduli (viscous component). Effect on rutting is expected to be asphalt-filler-specific.
A Life Prediction Model for Thermomechanical Fatigue Based on Microcrack Propagation
Authors: Miller MP , McDowell DL , Oehmke RLT , Antolovich SD
Published: March 2009

A thermomechanical fatigue (TMF) life prediction model is developed based on the concept of microcrack propagation. The model is used to correlate high temperature fatigue lives of two nickel-base superalloys.

Due to its complexity, a well-accepted framework for correlation of TMF life has been elusive. Various approaches have been taken, ostensibly nonisothermal generalizations of isothermally derived models. The proposed model explicitly accounts for damage from all three high temperature fatigue (HTF) damage mechanisms prevalent in metals, i.e. fatigue, oxidation, and creep. The general form of the microcrack propagation equation is dadN=dadN|fatigue+dadN|creep+dadN|ox No crack growth is actually monitored in the present analysis; rather the equation is integrated between an appropriate initial and final crack size. The constants and exponents in this integrated form of the equation are then fit from test data. The fatigue and oxidation components are correlated using the ΔJ parameter with an additional time and temperature dependence included in the oxidation term. The ΔJ parameter has demonstrated excellent versatility in the correlation of fatigue macrocrack growth and also implicitly contains the elastic deformation information that is so important in the life of high-strength Ni-base superalloys. The creep component of microcrack propagation is correlated using C, which is similar to the creep crack growth parameter Ct. Isothermal as well as TMF test data for MAR-M247 are analyzed. The mechanical strain versus temperature relationships for the TMF tests include in-phase (IP), out of-phase (OP), and counterclockwise diamond history (DH). Lives of the isothermal, IP, and OP tests are correlated within a factor of ± 2 of the median life. Lives of the DH tests are predicted within a factor ± 2 as well. Isothermal, hold time, and bithermal test data for as-cast MAR-M246 are also correlated within ± 2 of the median life using the approach.
Modeling the Progressive Failure of Laminated Composites with Continuum Damage Mechanics
Authors: Lo DC , Allen DH , Harris CE
Published: March 2009

A continuum-damage-mechanics-based model is proposed for the analysis of the progressive failure process in laminated composite structures. The laminate's response is determined by nonlinear constitutive equations that account for each type of matrix-dominated damage through strain-like internal state variables. Evolution of these internal state variables is governed by the damage-dependent ply-level stresses. The updated damage state and the ply-level stresses are then employed in the local-global evaluation of component failure. This model is incorporated into a finite-element analysis code to facilitate the examination of structures with spatially varying stress fields. The stress and damage distribution obtained from the analysis at various points in the loading history provide information about the progression of events leading to the failure of the component. The progressive failure of fatigue-loaded rectangular crossply-laminated plates containing a centered circular cutout has been examined with the model. Most of the predicted damage is localized in a region near the cutout. Rather than propagating outward, the damage intensifies in this region until failure occurs. The feasibility of modeling the evolution of each type of subcritical damage is demonstrated with the current framework. This ability to simulate the progressive failure process at this level of detail will assist in the design of safer and more efficient composite structures.
Unconfined and Confined Wide Width Tension Testing of Geosynthetics
Authors: Wilson-Fahmy RF , Koerner RM , Fleck JA
Published: March 2009

The thrust of this paper stems from the classical confined wide width testing work of McGown, Andrawes and their co-workers in 1981 and 1982 on geotextiles and extends it into the following geosynthetics which are currently used in various waste containment applications: • Woven and nonwoven geotextiles • Geomembranes • Geosynthetic clay liners • Geonets

Confining (normal) pressures up to 138 kPa are utilized to note the effects and, in particular, the variation from the standard unconfined behavior. A range of commercially available materials is used in each of the above categories. The test device used is based on the design principles set by McGown, Andrawes and their co-workers with some modifications being made to simplify the testing technique. The test results substantiate the successful performance of the apparatus. With the exception of nonwoven geotextiles and in particular needle-punched nonwoven geotextiles, the influence of normal stress is shown to be insignificant. This is considered to be the major finding in this study.Confinement does, however, enhance greatly the load-extension modulus of needle-punched geotextiles while it has little effect on their tensile strength.
Laboratory Investigations on the Shear Strength of Geogrid Reinforced Soils
Authors: Cazzuffi D , Picarelli L , Ricciuti A , Rimoldi P
Published: March 2009

A new apparatus for direct shear and pull-out tests was conceived to study the soil-geosynthetic and the geosynthetic-geosynthetic interaction: it consists of a testing box, having a contact area of 0.1 m2, with vertical and horizontal loads applied by an electronically controlled two-axis testing machine. Different types of geogrids (both uniaxially and biaxially oriented) were tested. Two different types of soil were used: silty sand and gravel. Particularly,direct shear tests were run using different testing rates (varying from 0.1 to 5.0 mm/min). The second part of the research concerned triaxial tests, using a very large cell (0.82 m height and 0.35 m diameter) and the same gravel soil. These tests were performed with and without the geogrid reinforcements. The direct shear tests have demonstrated that the rate of displacement does not influence significantly the soil-geosynthetic interaction. On the other hand, the triaxial tests have emphasized that the geosynthetic inclusion give a not negligible cohesion to the whole mass and determine peculiar modes of failure.
Effects of Layer Waviness on the Compression Response of Laminates
Authors: Adams DO , Hyer MW
Published: March 2009

Layer waviness was investigated in T300/P1700 carbon/polysulfone composite laminates under static compression and compression fatigue loading. A three-step procedure was used to fabricate isolated layer waves into the central 0° layer in [902/02/902/02/902/02u]s laminates. Layer wave geometries up to 1.5 layer thicknesses in amplitude and as short as 9 layer thicknesses in length were tested. The more severe wave geometries are shown to produce reductions in static strength as high as 36%, although the wavy 0° layer accounts for only 20% of the load-carrying capacity of the laminate. Moderate wave geometries produce a one-and-one half decade loss of compression fatigue life as compared to specimens without layer waviness. Specimen failures in both static compression and compression fatigue tests were sudden and catastrophic. Brooming failure, characterized by through-the-thickness splaying of the layers and numerous delaminations near the waviness, was the common failure mode.
Failure of Thick Composite Cylinders Subjected to External Hydrostatic Pressure
Authors: Starbuck JM , Blake HW
Published: March 2009

The experimental results from implosion tests of various graphite/epoxy and glass/epoxy cylinders are correlated with predictions from a performance model for thick composite cylinders subjected to external hydrostatic pressure. That performance model consists of a stress module, a stability module, and a material failure module. The stress module predicts the ply-level stresses and is based on an anisotropic elasticity solution for axisymmetric loading. The stability module predicts the critical buckling load based on a laminated orthotropic shell theory which includes transverse shear deformations. The failure module rotates the ply-level stresses computed from the stress module to the principal material coordinates and applies several existing failure criteria for determining first-ply failure. The correlation between the experimental data and analytical results led to the selection of the Hashin criteria as the most appropriate failure theory for thick-laminated composite cylinders loaded in compression. The results obtained from the Hashin criteria are consistent with the observed experimental results provided that composite material strength allowables are based on representative tests and that appropriate solutions for cylinder stresses are used. Both the failure criteria and stress solution must allow for the three-dimensional stress state and for the discrete layer construction. Further applications of the performance model are demonstrated for a range of laminate constructions. The results from these parametric studies provide insight to optimum designs for graphite/epoxy and glass/epoxy cylinders.
Response of Notched Graphite/Epoxy and Graphite/PEEK Systems
Authors: Lagace PA , Bhat NV , Gundogdu A
Published: March 2009

A test program was conducted to compare the tensile behavior of laminates made with graphite fibers and a low strain-to-failure matrix system (epoxy) versus a high strain-to-failure matrix system (PEEK), in the presence of notches. Graphite/epoxy (AS4/3501-6) and graphite/PEEK (AS4/APC-2) laminates were utilized in three different layups: [(±45)2/0/90]s, [45/02/-45/02/90]s, and [±45/0]s. These laminates represent “soft,” “stiff,” and “medium” configurations, respectively, in regard to their longitudinal stiffness as manifested by the percentage of 0° plies in each. Two different hole configurations, open and filled, were utilized with three different hole diameters: 6.35, 9.53, and 12.7 mm. All specimens were tested to failure in tension with X-ray photographs taken at various loading intervals with the aid of a dye penetrant. Semi-empirical relations were successfully used to correlate the data for both material systems. The graphite/epoxy system showed earlier and more extensive matrix damage than the graphite/PEEK system. In the case of the “soft” [( ± 45)2/0/90]s laminate, this led to a lower failure stress for the graphite/epoxy laminate as compared to the graphite/PEEK laminate; whereas, this led to a higher failure stress for the “stiff” [45/02/-45/02/90]s graphite/epoxy laminate. This is related to the number of major load-carrying plies (0°) in the laminate and the load redistribution caused by the damage. These results indicate that the in-plane “toughness” of a composite laminate is a structural property and cannot be directly correlated to the “toughness” or strain to failure of the matrix system but must account for the damage progression which occurs in the specific laminate configuration.
Management of Neutron Radiation Embrittlement: A View from the United States
Authors: Griesbach TJ , Server WL
Published: March 2009

One of the main concerns in nuclear power plant operation is protecting the reactor pressure vessel against unstable, brittle fracture. The American Society of Mechanical Engineers (ASME) Boiler and Pressure Vessel Code and U.S. Nuclear Regulatory Commission (NRC) regulations prescribe methods for determining plant operating pressure-temperature curves and radiation embrittlement limits that define safety margins for both normal and accident conditions. These limits must be updated periodically using a surveillance testing program to reflect the condition of the steel vessel wall after many years of neutron irradiation. In older plants, these limits may impose significant operational restrictions. Surveillance data may also be useful in demonstrating that, in some plants, the effects of embrittlement are minimal and the life of the vessel can be extended while maintaining adequate margins of safety for plant operation. Decisions involving both life attainment and life extension place new demands on the surveillance program. In some cases, the new demands can be met by minor program adjustments; in other cases, major adjustments are needed to obtain the requisite data. This paper discusses various approaches for managing radiation embrittlement in support of life attainment and life extension decisions. Strategies such as integrated programs, replacement surveillance capsules, and supplemental dosimetry measurements are addressed.
Surveillance of WWER-440Č Reactor Pressure Vessels
Authors: Brumovský M , áš Páv T
Published: March 2009

In Czechoslovakia there are six units of Water-Water Power Reactor (WWER)-440Č type reactors (pressurized water reactor [PWR] type) incorporated with pressure vessel surveillance specimens. These sets of specimens are kept for carrying out static tensile testing, impact notch toughness testing, and static fracture toughness testing, and are supplemented by necessary sets of neutron flux monitors.

Results of mechanical testing of these specimens evaluated after one to five years of reactor operation are summarized and discussed with respect to the effect of individual heats and welding joints, radiation embrittlement laws, and lead factor and pressure vessel lifetime assessment.
Experimental Study of the Anisotropic Behavior of the CMSX2 Single-Crystal Superalloy Under Tension-Torsion Loadings
Authors: Nouailhas D , Pacou D , Cailletaud G , Hanriot F , Rémy L
Published: March 2009

A thin tube made in single crystal is submitted to tension-torsion loading. The axis of the tube coincides with the 〈001〉 material axis. Local strain measurements made by means of strain gages experimentally demonstrate that the deformation is mainly localized in the 〈110〉 type zones. This is confirmed by microstructural observations of replicas. An experimental loading surface in these soft zones is derived. An analysis of the experimental data is successfully made through the Schmid law, involving both cube and octahedral slip.
Evaluation of Bearing Steels Produced by Powder Metallurgy Process
Authors: Tsubota K
Published: March 2009

A variety of steel powders for bearing applications, such as high-speed tool steel, M50 and 440C steels, etc., prepared through vacuum induction melting (VIM) and inert gas atomizer were canned and consolidated by hot extrusion to bars for specimens used in this experiment.

The carbide sizes of the extruded materials through powder metallurgy (P/M) route were extremely fine as compared to ingot metallurgy (I/M) materials. Nonmetallic inclusions were finely dispersed and the materials were rated to have good cleanliness per ASTM E 45-85 (Method A), Practice for Determining the Inclusion Content of Steel.

It is found that lower hardening temperature for P/M materials, with finer carbides that dissolve to the matrix rapidly, can produce hardness comparable to one of I/M materials quenched from a standard temperature. P/M materials, in addition, show significantly better impact values and bending fracture strength than I/M materials due to finer carbides and inclusions.

The rolling contact fatigue test results of M50 steel revealed that fatigue life of P/M materials is comparable to the highest class of life obtained in the same grade of I/M materials. Also, flaking leading to extremely short life, which is sometimes encountered in I/M materials, did not occur in P/M materials.
High-Nitrogen Cr-Mo Steels for Corrosion Resistant Bearings
Authors: Berns H , Trojahn W
Published: March 2009

The substitution of nitrogen for carbon distinctly improves the corrosion resistance of martensitic stainless steels with about 15% chromium and 1% molybdenum. In addition, this property becomes more stable with respect to tempering. Together with a raise in secondary hardening, the new high-nitrogen steels combine improved hot hardness and corrosion resistance for service at elevated temperatures. The new steels show better mechanical properties and bearing life as compared to conventional stainless bearing steels. Pressurized electroslag remelting allows for partial substitution of nitrogen for carbon. A full substitution is possible by powder metallurgy. Further investigations are in process.
A New Approach to Determine the Effect of Nonmetallic Inclusions on Material Behavior in Rolling Contact
Authors: Böhmer H-J
Published: March 2009

Nonmetallic inclusions have an important influence on rolling element bearing behavior. Though this has been well-known for a long time, consideration of nonmetallic inclusions is usually done on the base of empirical results. This paper shows a new approach to describe the influence of inclusions partly analytical on a mechanical base. The notch effect of inclusions due to their mechanical properties in difference to the steel matrix was calculated by finite element method (FEM). The results were used to discuss the material reaction on nonmetallic inclusions in stress fields related with Hertzian contacts. Additionally, residual stresses were considered, and the interaction of both inclusions and residual stresses in rolling contact fatigue is discussed.
Production of High Life Bearing Steels by Ladle Refining and Electroslag Remelting in Daye, China
Authors: Zhou D-G , Wang C-S , Xie Y-Q , Wan Y-S
Published: March 2009

The metallurgical characteristics and properties of bearing steel processed by ladle refining with vacuum argon deoxidation (VAD), with nonvacuum argon stirring (AS), and with electroslag remelting (ESR) are reported in this paper. Based on analysis, determination of nonmetallic inclusions in steel, and fatigue life test of steel products, the main results obtained are as follows: (1) due to low oxygen content, fine dispersion, improved characteristic and morphology of inclusions, and elimination of D-type inclusions in steel, the fatigue life of electric furnace (EF) + VAD or AS steel is twice as high as that of EF steel; (2) although the amount of inclusion and oxygen in ESR steel is higher than that of ladle-refined steel, the fatigue life of ESR steel is higher than the latter because of its fine and well dispersed inclusion.
Life Prediction of Ammonia Storage Tanks Based on Laboratory Stress Corrosion Crack Data
Authors: Nyborg R , Lunde L
Published: March 2009

Stress corrosion crack growth of carbon steel in anhydroi ammonia has been studied at both ambient temperature and at −33 %C. This has resulted in the development of a crack growth model where tl crack depth is predicted to be proportional to the square of the stress intensity factor and the square root of the exposure time. The crack growth is much slower at a low temperature of −33 %C than at ambient temperature. The crack growth model has been used together with field inspection results and probabilistic methods to obtain a quantitative measure for the probability of tank failure as function of time. This approach can be used by the ammonia storage tank operators to optimize the inspection intervals and procedures while assuring the safety of the tank.
Composite Modeling of Atmospheric Corrosion Penetration Data
Authors: McCuen RH , Albrecht P
Published: March 2009

Corrosion penetration of steel depends on the chemical composition of the material, the environment at the exposure site, and the extent to which debris accumulates on the surface of the specimen. Corrosion penetration data have traditionally been modeled with a power function over the full length of exposure time. The power model lacks the flexibility to describe a variety of behaviors and often underpredicts corrosion penetration at the end of the service life of a structure. Composite models are shown herein to better represent corrosion penetration data. Thirty-eight sets were fitted with power and composite models. In all cases, the composite model fitted the data at least as well as the power model, and in most cases better judging by goodness-of-fit statistics and errors between the predicted and measured penetrations. Errors in penetration predicted with the power model often show large local biases, suggesting the model structure is incorrect. Local biases also serve as a warning that projections of penetration to the end of the service life may be highly inaccurate. Conversely, composite models have unbiased coefficients and better represent the factors that govern corrosion penetration, thus giving greater confidence in service life projections.
The Development of an Experimental Data Base for the Lifetime Predictions of Titanium Nuclear Waste Containers
Authors: Ikeda BM , Bailey MG , Quinn MJ , Shoesmith DW
Published: March 2009

To predict the expected lifetimes of nuclear waste containers under Canadian disposal vault conditions, specific criteria upon which a predictive model can be based must be developed. The anticipated evolution of the corrosion of titanium waste containers is described. Failure is most likely to occur by a combination of crevice corrosion, hydrogen-induced cracking and general corrosion and, for long lifetimes, the duration of crevice corrosion must be limited. The crevice corrosion of Grade-2 and Grade-12 titanium has been studied using a galvanic coupling technique. The propagation of crevice corrosion on the Grade-2 material is dependent on both temperature and oxygen concentration and repassivation occurs once the oxygen is consumed. The propagation of crevice corrosion on the Grade-12 alloy appears almost independent of temperature, and repassivation occurs for T ⩽73°C even in the presence of copious amounts of oxygen. The implications for predicting the lifetimes of containers under disposal conditions are discussed.
The Importance of Subtle Materials and Chemical Considerations in the Development of Accelerated Tests for Service Performance Predictions
Authors: Palumbo G , Brennenstuhl AM , Gonzalez FS
Published: March 2009

The usefulness of accelerated laboratory tests for selecting materials for applications where corrosion is likely to be the main life limiting concern can be compromised by subtle, often ignored, microstructural and microchemical factors. Residual deformation and crystallographic orientation are metallurgical factors which can have a large effect on corrosion response and therefore must be considered when comparing materials. Microchemical differences are often addressed but there is still scope for'improvement here. Less commonly used microprobing techniques such as secondary ion mass spectrometry (SIMS) can provide additional information on the segregation of trace impurities which can have an important influence on corrosion resistance.

Another difficulty with accelerated tests is that high levels of acceleration often mask differences in corrosion response. This may lead to the best candidate material for the service environment not being selected. To minimize this problem the accelerated test should simulate as closely as possible the service environment. This may mean that data will take longer to obtain, however, this is the inevitable price of a greater degree of confidence in the material that is finally selected.
Acceleration of Stress-Corrosion Cracking Test for High-Temperature, High-Purity Water Environments by Means of Artificial Crevice Application
Authors: Akashi M
Published: March 2009

In order to study the effects of introducing an artificial crevice to the specimen on the stress-corrosion cracking (SCO test for stainless alloys in the boiling water reactor (BWR) primary coolant environments, uniaxial constant load tests were performed in a high-temperature, high-purity water environment on Type 304 stainless steel and Alloy 600 type Ni-base alloys, both sensitized. 0n analyzing the lifetime distribution data by fitting to the exponential distribution model, it was found: (1) the lifetime to initiation of SCC can be accelerated by introducing an artificial crevice to the specimen; (2) the acceleration efficacy of graphite-fiber wool as a crevice-forming material is confirmed; (3) the acceleration effect of artificial crevice is stronger for Alloy 600 type Ni-base alloys than the Type 304 stainless steel by a factor of 5 to 6; and (4) by comparison of the performance data in actual environments and the results of analysis conducted on the laboratory acceleration test data, the use of artificially-creviced specimen for the SCC lifetime test has been justified because it effectively shortened the SCC initiation lifetime without losing the factual correspondence to the SCC that occurs in actual service environments.
Quantitative Measurement of the Corrosion Rate Using a Small Counter Electrode in the Boundary of Passive and Corroded Zones of a Long Concrete Beam
Authors: Andrade C , Macias A , Feliu S , Escudero ML , González JA
Published: March 2009

Recently, in CORROSION-87, one paper was presented which, assuming the electrical model of the “transmission line” to represent the nonuniform distribution of the current in a concrete beam, demonstrated the calculation of the instantaneous corrosion rate by unit of length of the rebar through mathematical equations.

In the present contribution those equations are used in order to determine whether the equations enable distinction between the corroded zones of a rebar and those which remain passive. A concrete beam was fabricated, half of it by mixing chlorides with the cement (and therefore inducing a corrosion in the rebars) and the other half without admixtures (passivated zones of the rebars). The apparent polarization resistance was measured along the beam using a small counter electrode. Through the equations previously proposed, the corrosion rate was calculated.

The results obtained confirm that the boundary between corroded and passivated zones can be clearly identified using these formulae. Finally, some comments are given on the relative activity of galvanic macrocells compared with the corrosion microcells.
Construction and Testing of Deep Foundation Improvement Using the Deep Cement Mixing Method
Authors: Babasaki R , Suzuki K , Saitoh S , Suzuki Y , Tokitoh K
Published: March 2009

The construction of an office building (hereafter referred to as “Building N”) was planned in Kagoshima City in western Japan. The building site consisted of loose, alluvial sand called Shirasu, which is subject to liquefaction during earthquakes. It was decided that a newly developed soil improvement technique would be adopted as the foundation construction method. The technique employs the Deep Cement Mixing Method to construct a grid of hardened soil. This grid controls the generation of excess pore water pressure by reducing the occurrence of shear deformation in the native soil within the grid, thereby preventing liquefaction during earthquakes.

This paper discusses the design and construction of the improved soil foundation for Building N.
Degradation of Fluorescent Tracer Dyes Used in Spray Applications
Authors: Salyani M
Published: March 2009

Fluorescent dyes Basonyl Red 485, Eosine OJ, and Tinopal CBS-X were used to study the effect of solar radiation on dye degradation. Drops of dye solutions, prepared at 10, 100, and 1000 mg/L concentrations, were dispensed on mylar plastic and cellulose filter paper targets. Dye deposits, made with 1, 2, and 4 μL drops, were exposed to 5–120 min sunlight (0.125–3.963 MJ/m2 solar radiation). The deposits were washed with deionized water and the amount of fluorescence was determined with a fluorometer.

All three dyes showed considerable degradation under solar radiation and the effects of both dye concentration and target type were significant. Degradation was higher at lower concentrations. Basonyl deposits had higher degradation on mylar sheet while Eosine and Tinopal (except 10 mg/L) deposits showed more degradation on filter paper. Drop size did not have a significant effect on dye degradation.
Efficacy of Polymeric Controlled Release Formulations of Sulprofos Against Tobacco Budworm, Heliothis virescens (Lepidoptera: Noctuidae) on Cotton
Authors: Latheef MA , Dailey OD , Franz E
Published: March 2009

Sulprofos was microencapsulated within five different polymers [medium and low molecular weight poly(methyl methacrylate), ethyl cellulose, poly(α-methylstyrene) , and cellulose acetate butyrate] by the solvent evaporation process. The microcapsules were formulated as suspensions in an aqueous solution of 88% hydrolyzed polyvinyl alcohol. Encapsulated sulprofos formulations were compared with an emulsifiable concentrate (EC) formulation of sulprofos for efficacy against eggs and larvae of tobacco budworm (TBW), Heliothis virescens (F.), on cotton. The ethyl cellulose formulation of sulprofos caused significantly greater mortality of TBW larvae (avg 74%) than the other polymeric formulations (avg 48.2%); but there was no significant difference in mortality of larvae between sulprofos EC and the ethyl cellulose formulation of sulprofos. Xanthan gum, when added to the ethyl cellulose to increase suspension of the active ingredient, significantly decreased the efficacy of the microcapsule formulation of sulprofos against TBW larvae. Overall, microencapsulation of sulprofos did not significantly affect mortality of TBW larvae on cotton. Ovicidal mortality caused by sulprofos EC averaged 4.8%. The poly(αmethylstyrene) formulation of sulprofos exhibited significantly greater ovicidal mortality of TBW than the sulprofos EC 5 days after treatment (28.7 versus 1.8%). Overall, polymeric capsules slightly increased ovicidal mortality of sulprofos (6.1 to 14.1%), but not significantly so.
X-Ray Diffraction Characterization of Percent Crystallinity and Contaminants in Plasma-Sprayed Hydroxylapatite Coatings
Authors: Prevey PS , Rothwell RJ
Published: March 2009

Composite orthopedic and dental implants consisting of metallic substrates plasma-spray coated with hydroxylapatite (HA), are currently used in reconstructive surgery. It is believed that the crystalline form of the calcium phosphate ceramic, the presence of contaminant phases, and the degree of crystallinity affect its biological properties.

X-ray diffraction has been employed to characterize the contaminants and percent crystallinity in biological and sintered synthetic HA. However, application to plasma-sprayed coatings is complicated by the potential presence of several crystalline contaminant phases, an amorphous component, and possible instability during grinding or inhomogeneity of the coatings.

The external standard method of x-ray diffraction quantitative analysis is developed for HA plasma-sprayed coatings. A data collection and reduction strategy to allow separation of contaminant phases and the amorphous fraction is presented. Examples of applications to a variety of coating samples, typical of those in current use, are presented. Repeatability and accuracy are demonstrated with powder mixtures of known composition. Detection limits and sources of error are discussed.
Structural Changes of Plasma Sprayed Hydroxyapatite Coatings During In-Vitro Testing
Authors: Gross KA , Berndt CC
Published: March 2009

The in-vitro behavior of hydroxyapatite (HAp) coatings depends on the thermal history of the coating after thermal spraying. As-sprayed amorphous coatings degrade in Ringer's solution. Heat treatment at 800 °C for 2 hours produces a crystalline coating which upon immersion in physiological solution displays a greater stability. Coatings are characterized for surface morphology, composition, crystallinity, roughness, and weight loss. The as-sprayed coating shows changes in the coating morphology with immersion time. Individual lamellae crack and separate from the coating. Those lamellae still intact show evidence of dissolution. After a period of 8 weeks small HAp spheres cover the surface of the as-sprayed and heat treated coatings. These morphological changes are expected to influence the rate of bone bonding. Therefore post-treatment of HAp coatings is seen as a technique to alter or control implant-tissue interactions.