bluuebunny/crossref_metadata_2025_split huggingface dataset:
Final Stretch Model of Ductile Fracture
Authors: Wnuk MP , Sedmak S 
Published: March 2009

The differential equations defining the material resistance developed during the early stages of a ductile fracture process are derived from the concept of “final stretch.” The model suggests a certain near-tip distribution of displacements associated with a quasi-static Mode I crack such that the resulting strains are logarithmically singular at the crack tip.
The final results, which are illustrated by the diagrams of J-resistance curves, are equivalent to analogous data obtained by other researchers on the basis of the incremental plasticity theory. Similarities between the present results and the solutions due to Paris and co-workers as well as the most recent data obtained by Shih and co-workers are pointed out.
Effect of Higher-Order Stress Terms on Mode-I Caustics in Birefringent Materials
Authors: Phillips JW , Sanford RJ 
Published: March 2009

A general theory is developed for determining the sizes, shapes, and locations of the double caustics produced in statically loaded birefringent plates containing Mode-I cracks. Particular attention is paid to the effect of the first few higher-order, non-singular stress terms on the determination of the stress-intensity factor KI associated with the singular stress field.
It is found that the transverse diameters of the inner and outer parts of the double caustic have an average value essentially equal to the transverse diameter of the single caustic produced by an optically isotropic material having the same optical constant. Furthermore, with the superposition of a constant (tensile or compressive) stress parallel to the crack, each part of the double caustic deforms independently but in such a way as to maintain this average transverse diameter.
Other higher-order effects are also investigated and it is concluded that birefringent materials offer the potential of “feature extraction” concerning crack-tip stress fields, in addition to being suitable for the accurate determination of KI-values experimentally.
Development of a Method for Determining the Leachability of Organic Compounds from Solid Wastes
Authors: Warner JS , Hidy BJ , Jungclaus GA , McKown MM , Miller MP , Riggin RM 
Published: March 2009

This study was undertaken to develop a method for assessing the potential mobility (leachability) of purgeable and semivolatile organic priority pollutants from solid waste materials. The objective was to develop a method that would (1) model the leachability that might occur in a municipal landfill environment, (2) be relatively simple and easily implemented by production-type laboratories at a relatively low cost, and (3) give reproducible results.
The solid wastes studied included aqueous sludges, organic chemical wastes, and inorganic solids. The leaching media studied included distilled water, acetate and citrate buffers, reducing agents, and surfactants. A tumbling device designed by the National Bureau of Standards was used to achieve reproducible mixing of the specimen and the leaching medium with a minimum of particle-size reduction. The device tumbles the mixture of the specimen and leaching medium end over end in a closed container, and is applicable to nearly all solid waste materials.
Previous studies reported in the literature on solid waste leaching tests have generally emphasized the leachability of toxic metals. In order to permit a comparison of our results with previously reported results, the leachates generated were analyzed for metals as well as for organic compounds. Metals were determined by inductively coupled argon plasma spectroscopy (ICAP) and by flame atomic absorption spectroscopy (AAS). Purgeable organics were determined by gas chromatography-mass spectrometry (GC-MS) using Environmental Protection Agency (EPA) Method 624. Phenols, pesticides, and neutral organics were determined by GC-MS using EPA Method 625 with minor modifications. Studies on the precision of the leachability, metal analyses, and GC-MS analyses were performed as an important part of the overall analytical program.
The solid waste leaching procedure developed was shown to be reproducible, easy to use, and suitable for many types of wastes and analytes. Distilled water was found to be as effective as other media studied for leaching organic compounds. Citrate buffer was often much more aggressive than acetate buffer for leaching metals. The aggressiveness of citrate buffer was highly metal and specimen dependent. The degree to which the procedure reproduces the leaching of components in a codisposal environment, which would depend upon the leaching medium used and site-specific conditions, is unknown at this time.
Hot Isostatic Pressed Powder Metal Titanium Implant Devices
Authors: Chandhok VK , Rizzo FJ 
Published: March 2009

In recent years, Crucible Compaction Metals Operation has performed a considerable amount of work in developing a ceramic mold process for the production of near-net shape hardware from powder metal with consolidation by hot isostatic pressing (HIP). A detailed description of the process is given herein. Examples of the many configurations made to date are presented along with the comparison of mechanical property data obtained on as-HIPed parts versus conventionally produced material.
Based on the information generated, the ceramic mold process appears to be a viable alternative process for producing titanium implant devices.
Implantable Titanium Feedthrough Reliability
Authors: Dixon DE 
Published: March 2009

Implantable titanium feedthrough reliability is characterized by hermetic integrity, optimum mechanical design, and critical process requirements.
Hermetic integrity of a titanium electrical feedthrough depends on the coefficients of linear thermal expansion (CLTE) of the titanium, the sealing material, and the center conductor metal and on the degree of bonding obtained at seal-to-metal interfaces. Microscopic examination of the bond interface between titanium and the sealing material indicated fusion of the titanium oxide with the polycrystalline ceramic. Dilatometer measurements of titanium, a polycrystalline ceramic, and pure platinum (center conductor metal) showed similar CLTE for titanium and platinum, whereas the polycrystalline ceramic CLTE was less, thus ensuring some degree of compression in the sealing mechanism.
Optimum mechanical design was determined by thermal stress methods, which stressed designs through increasing thermal shocks until loss of hermeticity occurred in 50 percent or more of the specimen population. Two designs, one with mechanical reinforcement and the other without, were subjected to thermal shock ranges as severe as 755 K (900°F) to 78 K (−320°F). The plotted data indicated the design with mechanical reinforcement sustained higher levels of thermal shock without loss of hermeticity.
In vitro experiments on titanium feedthroughs with various surface configurations were conducted at low applied voltages (constant and pulse). The data indicated minimal electrochemical degradation at surfaces with maximum electrical leakage paths obtained by addition of ceramic standoff. Electrochemical degradation was measured in terms of insulation resistance between the titanium housing and the platinum pin and correlated to the accelerated battery depletion of a cardiac pulse generator. The battery life was observed to decrease rapidly as the electrical resistance across the titanium feedthrough decreased from 100 000 Ω.
Certain levels of temperature were shown to affect the grain size of titanium. Titanium (Grade 4) feedthrough housings were exposed to different temperature levels for the same 1-h duration. Scanning electron microscopy (SEM) photomicrographs verified by ASTM grain size determinations indicated substantial grain growth above the 1255 K (1800°F) temperature level. Conservative sealing conditions were recommended at less than the titanium beta transus temperature, 1158 K (1625°F), and less than 1-h exposure.
Comparison of Loading Behavior of Femoral Stems of Ti-6Al-4V and Cobalt-Chromium Alloys: A Three-Dimensional Finite Element Analysis
Authors: Tarr RR , Clarke IC , Gruen TA , Sarmiento A 
Published: March 2009

Large stiff, small moderately stiff, and small flexible femoral total hip components cemented in the proximal femur have been investigated using a three-dimensional finite element model and validated using experimental strain gage techniques. A physiological load of three times body weight (2000 N), 18 deg from vertical was utilized to compute stresses in the bone, cement, and metal construct.
For a well-fixed total hip replacement, the results show stem stresses to be between 5 and 20 percent of the reported fatigue limits for the metals analyzed. Cement stresses in the proximal-lateral region were negligible for all stems tested. In looking at the failure stress for cement, the proximal-medial cement stresses were seen to be only 4 to 6 percent of the reported compression failure criteria and the distal stresses only 5 to 10 percent of tensile failure criteria.
The proximal-medial bone stress was 30 percent of normal for a titanium alloy small stem, 21 percent of normal for a moderately stiff small stem, and only 6 percent of normal for a large stiff stem. Distal bone stress on the medial cortex was 39 percent higher for the stiff stem than for the flexible stem and 20 percent higher laterally.
In viewing these results in light of the stem design or femoral component failure criteria, the cement does not appear to be the weak link for the well-fixed total hip replacement, regardless of the stem design. If failure initiation does not begin within the cement in a well-fixed hip, physiological changes in the bone may be responsible for loosening at the cement-bone interface, and the cement may then be prejudiced. Some advantages of load transfer to bone are gained with the use of flexible stems, but the significance of these changes can only be confirmed or disputed with detailed clinical and radiographic follow-up.
Surface Preparation and Corrosion Behavior of Titanium Alloys for Surgical Implants
Authors: Fraker AC , Ruff AW , Sung P , Van Orden AC , Speck KM 
Published: March 2009

Surface preparation and corrosion behavior of titanium alloys were studied; both topics deal with the formation of surface oxide films. When metals are prepared for surgical implant use, an effort is made to produce an optimum surface. Effects of the surface treatments on surface morphology, surface film composition, and structure are shown in transmission electron photomicrographs and electron diffraction patterns. Roughened surfaces were produced, and surface films of titanium oxide (TiO) or titanium dioxide (TiO2) or both occurred on some specimens. Sodium titanate (NaO · xTiO2) occurred on the specimens washed in sodium hydroxide (NaOH) solution.
Open circuit potential versus time curves have been measured to show some electrochemical effects of various surface treatments. The results show that titanium alloys immersed in Hanks' physiological solution reach the same final open-circuit potential after approximately two weeks' exposure regardless of prior surface treatment. Measurements of the anodic polarization behavior of titanium alloys and other surgical implant alloys show the effects of alloy composition and the testing solution on the passive region and breakdown potentials of these materials. In general, for titanium alloys, the differences are not great, but the presence of nickel results in a significant lowering of the breakdown potential. The materials studied were titanium, Ti-6Al-4V, titanium-nickel (memory alloy), Ti-13Cu-4Ni, and Ti-4.5Al-5Mo-1.5Cr. In all cases titanium materials are more corrosion resistant in Hanks' solution than cobalt-chromium-molybdenum Type 316L stainless steel, or cobalt-nickel-chromium alloys. Repassivation measurements show the rapid formation and the high degree of stability of the protective film on titanium and titanium alloys.
Future Distillate Fuel Trends in Canada and Some Preliminary Gas Turbine Test Results on Tar Sand Products
Authors: Whyte RB , Grimsey RG , Glew CAW 
Published: March 2009

The forecast for distillate fuels in Canada projects a trend towards lower quality brought about by the falling demand for gasoline and heating oils and the increasing demand for aviation jet fuel and diesel fuel. The problem is compounded by the increasing aromaticity of the crude supply and the increasing volumes of heavy crudes being processed. The changes in quality predicted include a lower flash point, higher viscosity, broader distillation range, and lower cetane number, smoke point, and hydrogen content.
There is an urgent need to evaluate the power plant performance of such fuels, and as a first step, the Canadian Forces (Navy) have compared the performance of a Solar Saturn gas turbine when burning blends of tar sand crude fractions and a conventional diesel distillate.
No abnormal carbonization of the fuel injectors, or hot-end components, occurred when the engine was running on the tar sand blends. However, there was an increase in fuel consumption of between 4% at no load and 2% at full load, and associated decreases in combustion efficiency and increases in exhaust smoke level.
The combustor liner metal temperature increased by 30 deg Celsius at full power when the engine was running on either of the tar sand blends. These performance changes are attributed to the high aromatic content of tar sand products, and it may prove necessary to derate slightly certain types of gas turbines if they are required to operate on highly aromatic fuels.
Properties of Synthetic Fuels Evaluated for Combustion Turbines
Authors: Streed CW , Mulik PR , Ambrose MJ , Cohn A 
Published: March 2009

Under a comprehensive synthetic fuels program sponsored by the Electric Power Research Institute, Westinghouse Electric Corp. has evaluated the turbine combustion properties of over twelve coal-derived liquid (CDL) fuels, three shale-derived liquid (SDL) fuels, and six petroleum-derived surrogate fuels.
The combustion performance effects have been reported elsewhere. This paper compiles the properties of the various classes of synthetic fuels that were combustion-tested and discusses the significance of the analytical methods utilized by the Mobil Research and Development Corp. to characterize the physical and chemical properties, trace metal content, and aromaticity of these test fuels. The authors have concluded that certain modifications to the current ASTM turbine fuel specification tests will be required to accommodate CDL and SDL fuels.
Effect of Sodium and Potassium on the Hot Corrosion of Gas Turbines
Authors: Haskell RW , Doering HvonE , Grzybowski DF 
Published: March 2009

The determination of a specification for trace metal corrosion-causing contaminants in coal-derived fuels depends on the corrosion resistance of gas turbine hot gas path materials to the deposits produced during the combustion of such fuels. The contaminants of principal concern are compounds of sodium and potassium, which produce deposits of sodium and potassium sulfate.
This report gives the results of small burner rig (SBR) accelerated corrosion tests with state-of-the-art alloys and coatings for the combustion of distillate fuel doped with sodium and potassium chlorides. The SBR data on the deposit chemistry and corrosion rates are analyzed to give corrosion data for turbine hot gas path components as a function of fuel trace metal contamination. The modes of corrosion attack when sodium and potassium are present in comparison with those when only sodium is present (distillate case) are discussed.
A Projection of Coal Gas Properties Considered from the Viewpoint of a Coal Gas Combined-Cycle Plant
Authors: Marlow JH , Pavel J , Vidt E 
Published: March 2009

Four factors affect the quality of coal gas in the type of total gasification plant used for generation of electricity. The coal gas properties investigated here are considered in relation to the effects of these four factors: (a) coal type, (b) fluidized-bed type of gasifier, (c) wet (cold) and dry (hot) gas cleanup systems, and (d) gas turbine requirements.
The properties given are for gases having a heating value range of 3.4 to 11.3 MJ/m3 (90 to 300 Btu/ft3) and include gases from both air-blown and oxygen-blown gasifiers.
The chemical makeup of the gases is considered in terms of the nitrogen gas, hydrogen gas, carbon dioxide, carbon monoxide, and water content. Also the trace material content is given in both quantity and size of particles. The amounts of sodium and vanadium and both the size and the concentration of potentially erosive particles are discussed.
The measurement methods required for these types of fuels are also briefly discussed.
Tissue-Culture Methods for Determining Biocompatibility
Authors: Fehn J , Schottler D 
Published: March 2009

Tissue-culture test methods are used as acute screening for biocompatibility testing of materials and solutions used in the manufacture of our biomedical devices at Medtronic, Inc. Presently, we are capable of performing three methods, they are: agar overlay, minimal essential medium (MEM) elution, and low cell density. In all the test methods performed we use L-929 mouse fibroblasts as our cell line.
Tissue-culture procedures are used for screening the safety of materials that are being evaluated in the following situation: (1) new material and vendor qualification, (2) process change or qualification or both, (3) vendor audit, and (4) incoming inspection. Medtronic basically follows the guidelines of the Health Industry Manufacturers Association (HIMA) Report 78-7, which classifies devices into four categories based upon usage. These are intended to be guidelines, but ultimately the criteria to classify materials and the testing done on the material are dependent upon (1) the intended end use of the material and its application, (2) whether it has direct or indirect body tissue, or fluid contact or both, (3) whether it will be short term or long term or both, and (4) if the material is put through a process that may change or affect the material or both.
The decision as to which tissue-culture method to use by which to screen a material is determined by (1) the nature of the material, (2) information required of testing, and (3) history of material and which test method is most applicable. The results of tissue-culture testing are meant to be screening and do not replace in vivo testing. If the results of a tissue-culture test are questionable, it is the decision of the study director of how to proceed. Medtronic has been doing tissue-culture testing for more than ten years and has a good data base to support our test methods.
Statistical Aspects of Fatigue Failure Due To Alloy Microstructure
Authors: Morris WL , James MR 
Published: March 2009

The elements of a methodology are described to calculate the scatter in fatigue lifetime which arises from statistical variations in alloy microstructure from sample to sample within a uniform heat of material, and from variations in mean grain size and in the ductility of the alloy surface from heat-to-heat. The modeling is formulated for certain structural aluminum alloys for which the dominant mode of crack initiation is by fracture of constituent particles near the alloy surface. For one of these, an Al 2219-T851 alloy, small amounts of internal hydrogen at contents less than 1 ppm are found to affect surface ductility and both crack initiation and early growth. The application of models of crack initiation and short crack growth to predict the combined effects of grain size and hydrogen on fatigue lifetime is demonstrated for smooth bar specimens of two heats of Al 2219-T851. Experiments confirm predictions that fatigue lifetime is increased by decreasing both grain size and alloy hydrogen content.The models used to predict fatigue lifetime are discussed individually and deal with both the initiation and the early growth of surface fatigue cracks. They are evaluated by comparing predicted and measured mean and stochastic trends in rates of initiation and growth in Al 2219-T851 and Al 7075-T6. The paper concludes with a short treatment of the implication of the statistical nature of the fatigue failure process to prediction of the occurrence of failures of low probability, very early in the service lifetime.
Measurement of Fatigue Damage by Randomly Distributed Small Cracks Data
Authors: Kitagawa H , Nakasone Y , Miyashita S 
Published: March 2009

During the fatigue process of unnotched smooth materials, small surface cracks often initiate, grow, and coalesce; these cracks are randomly distributed over the material surfaces in terms of size and location. This paper investigates the probabilistic laws these cracks follow, and proposes a quantitative method for the fatigue damage evaluation and residual-fatigue-life prediction of the materials. This method can be carried out in two ways. One is based on the variation of the statistical parameters (for example, the mean etc.) of the crack surface-length distribution with the number of load cycles. The other is based on the growth rate of the distributed small cracks and on the crack length distribution function.The procedures of the method are described by taking the example of corrosion fatigue of a weldable structural steel, HT 60. The first step is the preparation of specimens having small cracks randomly distributed over their surfaces; the second step is the sampling of statistical data on the cracks from these specimens and from real structures; and, finally, the third step is fatigue damage evaluation and residual-life prediction based on various statistical treatments of the data obtained.For the test of the goodness of the model and data in the present study, a Monte Carlo simulation analysis was made, which can deal with the initiation, growth, and coalescence behavior of distributed cracks.Finally, the characteristic features and the scope of application of the method are described, and some comments are made on its applications to other fatigue fracture processes.
Interaction of Gage and Hardenability on the Properties of Quenched and Tempered 2¼Cr-1Mo Steel Plate
Authors: Swift RA 
Published: March 2009

A study of the hardenability of 2¼Cr-1Mo steel shows that the strength of this steel in the quenched and tempered condition can be correlated with the calculated hardenability, as defined by the ideal diameter, D1, but not with an inflection point in the Jominy end-quench hardness-distance curve, J1, for plates in gages from 140 to 214 mm. No correlation is found for plates 76 to 91 mm in gage or when the heavier plates are tempered to a Holloman-Jaffee parameter of 20.7 × 103. These trends are explained by the degree of through hardening and the sequence of precipitations that occur when the quenched steel is tempered.
The 50 percent martensite microstructure in an end quench test has been found to correlate with J1 but not D1. This, and the lack of correlation between J1 and D1 are explained by the methods used to develop each indicator. Both are indicators of 50 percent martensite. J1 indicates the location of the 50 percent martensite microstructure in an end quench bar regardless of the second constituent. D1 calculates the diameter for 50 percent martensite-50 percent pearlite. Since 2¼Cr-1Mo is bainite hardenable, a straightforward correlation is not expected.
Flowable Pesticide Formulations: Development, Process, and the Need for Standard Testing Procedures
Authors: Halliday CG 
Published: March 2009

Over the period of the last decade, numerous flowable (suspension concentrates) pesticide formulations have been developed using various manufacturing processes.
This paper deals briefly with the reasons for development of this type of formulation and the process and development problems encountered by the author and outlines the physical test procedures.
Physical tests such as specific gravity, particle size analysis, viscosity, and pH are mentioned, along with sampling problems which have been encountered in the field after these products were stored in a warehouse for some time. The need for standardization of physical test methods is mentioned.