bluuebunny/crossref_metadata_2025 huggingface dataset:
Nucleation and Growth of Intermetallic Precipitates in Zircaloy-2 and Zircaloy-4 and Correlation to Nodular Corrosion Behavior
Authors: Maussner G , Steinberg E , Tenckhoff E
Published: December 2008

One of the fundamental aspects in the history of the development of zirconium alloys for nuclear applications is the corrosion behavior under in-pile conditions. In boiling-water reactors (BWRs) and pressurized-water reactors (PWRs) the zirconium alloys Zircaloy-2 and Zircaloy-4 are the most commonly used materials, permitting attainment of a very high level of integrity and reliability. Nevertheless, efforts are required to optimize these well-established alloys with regard to their resistance to nodular corrosion, where improvements will give long-term advantages in fuel integrity and fuel economy. Phenomenological studies allow correlation of the nodular corrosion behavior with the morphological appearance of precipitated intermetallic phases in the microstructures of Zry-2 and Zry-4.

To understand the fundamental processes of precipitation, particle nucleation-and-growth studies were made with Zry-2 and Zry-4 in different fabrication dimensions and with variations in β-quenching rates followed by isothermal and isochronical heat treatments. The microstructural characteristics of the precipitates were investigated by optical and transmission-electron microscopy. The macroscopic behavior was studied by electrical-resistivity measurements and hardness measurements. The nodular-corrosion susceptibility was determined by weight-gain and nodule distribution measurements after a 500°C laboratory-autoclave test. Precipitation of the intermetallic phases (Zry-4: hexagonal (Fe, Cr)2 Zr; Zry-2: hexagonal (Fe, Cr)2 Zr and Zr2 (Fe, Ni)) occurs at the β/α transition.

Particle size and particle distribution depend on the β-quenching rate. Rapid quenching results in complete supersaturation. The isothermal and isochronical aging heat treatments are used for evaluation of the thermodynamic parameters for nucleation and growth of the precipitates.

Nucleation and growth of the precipitates lead to characteristic hardness effects and an increase in electrical resistance, which are superimposed on matrix recovery. The nodular corrosion effects in the 500°C test can be correlated with the size and distribution of the precipitates. This correlation results in a limit to the particle size for desired nodular corrosion behavior in the final product. A strong influence of cold work on particle growth appears to exist and is expected to cause a significant increase in the particle growth velocities determined in this study.
Nodular Corrosion Resistance of Zircaloy-2 in Relation to Second-Phase Particle Distribution
Authors: Andersson T , Thorvaldsson T
Published: December 2008

A large number of Zircaloy-2 standard tube lots and tube lots beta-quenched in intermediate size were corrosion tested in steam at 490 to 515°C. In addition, specimens heat treated in the temperature range 675 to 850°C were corrosion tested in steam at 500°C. To study the correlation between nodular corrosion susceptibility and type and size distribution of second phases, specimens from one beta-quenched and two standard tube lots, one with high resistance and one with low resistance to nodular corrosion, were examined by optical and electron microscopy. In addition, specimens from the heat treatment program were studied in order to investigate heat treatment effects. For quantitative analysis, a JEOL 200 CX scanning transmission electron microscope (STEM) equipped with a Link Systems energy dispersive X-ray spectrometer (EDX) was used.

The STEM studies showed that two main types of second phases exist irrespective of heat treatment. These are hexagonal Zr(Cr,Fe)2 and tetragonal Zr2(Ni,Fe). Of the different microstructural features studied, the size distribution of particles was found to be the main factor distinguishing the different materials. In the low susceptibility standard tube lot, the particles were smaller than in the high susceptibility lot. The smallest particles were found in the beta-quenched lot, where no particles coarser than about 0.2 µm could be seen. The coarsest particles, about 1 µm, were observed after annealing at 750°C, which was the temperature showing a dramatic weight gain peak in 500°C steam testing.

It is evident that material with coarse second-phase particles is particularly susceptible to nodular corrosion. The STEM observations support the idea that there is a critical particle size for nucleation of a nodule, a size which is directly related to the test temperature. This model can explain the lot-to-lot variation observed for standard material and the improved resistance for tubing beta-quenched in intermediate size.
Deformation and Fracture Properties of Neutron-Irradiated Recrystallized Zircaloy-2 Cladding under Uniaxial Tension
Authors: Yasuda T , Nakatsuka M , Yamashita K
Published: December 2008

Sufficient evaluation of the changes in mechanical properties, such as elastic, plastic, and failure properties, due to neutron irradiation in service is required to precisely predict fuel performance. This paper presents the results of the uniaxial tensile tests performed for recrystallized (850 K, 2.5 h) Zircaloy-2 claddings irradiated in commercial BWRs to fluences of 5 × 1023 to 4 × 1025 n/m2 (E > 1 MeV). The material constants of irradiated Zircaloy-2 were obtained precisely, using a high temperature elongation detector in a hot-cell and computer analyses of digital stress-strain data.

The tensile tests were carried out at 298 to 673 K at strain rates of 0.05 to 5%/min, using tubular specimens cut to 135 mm lengths from the claddings. From these tests, Young's modulus, strain hardening exponent, strain rate sensitivity, and fracture behavior were obtained and evaluated.

Young's modulus of specimens irradiated to 1024 n/m2 is nearly equal to that of unirradiated ones, but irradiation to 1025 n/m2 shows values 7% higher than for unirradiated ones. The irradiation-induced increments in yield stress are rapid below 1 × 1024 n/m2, then slow down above this fluence becoming proportional to (φt)0.1 for fluences of 1 × 1024 to 4 × 1025 n/m2, where φt is fluence.

The strain hardening exponent before irradiation is 0.15 and a constant which is independent of strain levels, but after irradiation it decreases depending on strain increase. The strain rate sensitivity at the 0.2% plastic strain decreases from 0.037 to 0.021 by irradiation.

There are two types of fracture morphologies after irradiation: necking and spiral types. In the latter, a shear band propagates along only one direction. Both are accompanied by localized deformation bands caused by dislocation channelling. The spiral type is predominant at about 573 K, in high irradiation and at high strain rate. The fracture surfaces of the unirradiated and irradiated materials are all ductile, while the number of small dimples, whose nuclei appear to be irradiation defects, increases with fluence. The ratio of the number for unirradiated, irradiation to 1 × 1024 n/m2, and irradiation to 1 × 1025 n/m2 is 1:2.7:2.9.
Experimental Observation and Computer Simulation of the Microstructure of Vapor Deposited Thin Films
Authors: Guenther KH
Published: December 2008

The microstructure of thin films applied by conventional physical vapor deposition for use as optical coatings is columnar for most of the materials commonly used. This has been established for about a decade through numerous experimental observations employing microfractographical replication for use with high resolution transmission electron microscopes. Scanning electron microscopes are more useful investigating coating defects, the most remarkable of these defects being known as nodules. From fundamental considerations of nucleation and growth of thin films, the origin of both columns and nodules, and the dependence of their appearance on the deposition conditions, are discussed in some detail. A simple 2-D simulation model assuming very limited surface mobility of adatoms or admolecules shows striking similarities to peculiar properties of both columnar and nodular growth seen in actual investigations. Conclusions are drawn as to how the two types of microstructures described influence general thin film properties, but in particular as to how they influence possible laser damage mechanisms.

This paper is of a tutorial nature, although most of the results presented are from the author's own work, some of them having been published previously.
Effects of Rotary Peening and Surface-Conditioning Products on Structural Steel
Authors: Claus JJ
Published: December 2008

Structural steel surfaces have traditionally been prepared with blasting techniques or with a combination of chemical etching and mechanical surface scouring. More recently, portable power tool systems using three-dimensional nonwoven surface conditioning products and an impacting and peening flap wheel are finding increased usage in the surface preparation of steel structures because they are efficient and effective. The profile, microhardness, and chemical nature of the surfaces generated by the power tool products and the traditional blasting technique are reported.
Zinc-Plus-Paint System for Corrosion Protection of a Steel Bridge
Authors: Lwin MM
Published: December 2008

Steel bridges are commonly protected from corrosion by the use of weathering steel (unpainted), paints, or zinc. The use of zinc and paints in combination has not received much attention in bridge construction. This paper describes the factors influencing the selection of a zinc-plus-paint system for corrosion protection of the structural low-alloy steel lift spans of the Hood Canal Floating Bridge. This bridge is situated in a marine environment and is designed to have a service life of 75 years.

A zinc-plus-paint system consisting of 1.07 kg/m2 (3.5 oz/ft2) of zinc and two coats of paint each 0.005 mm (2 mils) thick is predicted to provide corrosion protection in a marine atmosphere for more than 70 years. The initial cost for this system is higher than for a three-coat paint system, but the long-term advantages and cost savings are substantial.
Spray-Applied Fluoroelastomers for Protection of Carbon Steel Structures in Flue Gas Desulfurization Service
Authors: McClain CA , Dolan T
Published: December 2008

Since the passage of the Clean Air Act of 1970, flue gas desulfurization (FGD) or scrubber systems have come into common use in fossil fuel power generation plants. Linings used in such systems must be able to withstand harsh service conditions that include wide fluctuations in temperature; acidic gases; a wide range of contaminants, both organic and inorganic; abrasion from fly ash and limestone slurry; and vibration. The properties of fluorelastomers, a relatively new material for such systems, are explored in detail and compared with four other types of materials used in FGD service: specialized alloys, inorganic monolithic cements, acid-resistant masonry, and other organic coatings.
Paint Research Institute Paint Corrosion Inhibitor Research
Authors: Hendry CM
Published: December 2008

From a series of Dr. Henry Leidheiser's papers and a Paint Research Institute (PRI) research proposal, an overview is presented of paint corrosion inhibition and potential research to clarify inhibition mechanisms and develop more accelerated testing methods. Possible mechanisms for corrosion inhibition in organic coatings by oxidizing inhibitors and metallic cations are discussed, as are the requirements for an ideal inhibitor for use in organic coatings. The writer suggests sponsorship by paint producers, steel companies, and firms with major steel structure investments of PRI research programs aimed at developing accelerated corrosion tests of paint inhibitors and defining the mechanisms by which the effective inhibitors protect steel.
Measurement and Prediction of the Effectiveness of Oil Spill Chemical Dispersants
Authors: Mackay D , Chau A , Hossain K , Bobra M
Published: December 2008

Recent developments in effectiveness testing of dispersants are discussed, with emphasis on the Mackay-Nadeau-Steelman laboratory test. A novel flume test system is described in which an attempt is made in the laboratory to simulate a sea test involving continuous application by boat. Some recent findings of test programs are discussed and a detailed mechanism proposed for the dispersion process. It is proposed that a mathematical model be sought to express effectiveness as a function of the volumes of oil, water, and dispersant, oil viscosity, water salinity, and application method. It is suggested that this model could form the basis of a procedure for correlating effectiveness and linking laboratory tests to application conditions at sea.
The Status of the Warren Spring Laboratory's Rolling Flask Test
Authors: Martinelli FN
Published: December 2008

This paper discusses the use of dispersants in the United Kingdom and describes the work undertaken to improve the laboratory test for the assessment of oil spill dispersant efficiency together with some of the supporting ongoing work in the field of dispersant evaluation. The revolving flask test used to measure the efficiency of oil spill dispersants was originally developed by Petrofina Ltd., but has been modified to meet the requirements of a simple test procedure to select dispersants for use at sea in accordance with the regulatory requirements of the U.K. Ministry of Agriculture, Fisheries and Food. Test results depended on operator technique and equipment. A program involving manufacturers, oil companies, and users was undertaken to improve the technique and precision of the test. Reproducibility between laboratories was on the order of ±10% mean. The test has been correlated with spraying trials at sea in which a carpet of oil was sprayed with a commercially available dispersant and the amount of oil dispersed into the sea by wave action was visually assessed.
California Study of Asphalt Concrete Density Measurement—Nuclear Versus Core Density
Authors: Alexander ML , Doty RN
Published: December 2008

The lack of a fast, reliable method for accurately determining in-situ density has been the major obstacle in the California Department of Transportation's (Caltrans) effort to develop an end-result compaction requirement for asphalt concrete pavement. Although the nuclear gage provides a rapid method of determining inplace densities, the results have not proven consistent with the densities determined by the generally accepted water displacement method of testing core specimens. This paper discusses factors contributing to these inconsistencies. It is concluded that the water displacement method is incorrectly described as a measure of bulk density and is not measuring the same properties as the nuclear method. It is also concluded that the Caltrans procedure for calibrating backscatter nuclear gages is introducing inconsistencies into the nuclear density determinations.

Several procedures for measuring the density of thin layers (less than 50 mm) of asphalt concrete have been examined. These procedures are described and their weaknesses discussed.
Fatigue Life Estimation of Notched Members
Authors: Socie DF , Dowling NE , Kurath P
Published: December 2008

From an engineering view, it is convenient to separate the total fatigue life of notched members into two portions: crack initiation, which is spent nucleating and growing small cracks, and the crack propagation life, which is spent growing these cracks to final fracture. The difficulty in applying this concept has been in defining the size of an initiated crack in a smooth specimen and dealing with small crack growth in the plastic zone near the notch root.

These difficulties may be overcome by considering a simple model where the total fatigue life is the summation of the portion of life controlled by notch plasticity and the portion controlled by nominal stress and crack length. The local strain approach is used to compute the initiation life. Growth of small cracks in the notch plastic zone is assumed to be part of the initiation life. Fracture mechanics concepts are employed to estimate crack propagation lives assuming an initial crack size equal to the notch depth.

Twelve sets of fatigue data reported in the literature were analyzed to assess the validity of the model. These include variations in specimen type, notch size, notch acquity, and material properties. Good correlation between the analytical estimate and experimental data was observed.
Fracture Analysis of Stiffened Structure
Authors: Swift T
Published: December 2008

A method, based on displacement compatibility, is presented for the fracture analysis of cracked stiffened structure. The method provides an economical means for the determination of crack-tip stress intensity factors and stiffener stress concentration factors that can be used for parametric crack growth and residual strength studies during the initial design phase of an aircraft structure. The results of a typical parametric study are included. Emphasis is placed on the need to account for stiffener bending stresses in residual strength calculations. This need is supported by test evidence. Fastener shear failure known as unzipping is discussed. An example, supported by test evidence, is shown where this phenomenon can precipitate failure of stiffened structure containing cracks. A method of analysis, based on fastener nonlinear shear displacements, is described, which can account for the effect of fastener failure during the failure process of a cracked stiffened panel. The method is verified by test.
Properties of Tantalum for Applications in the Chemical Process Industry
Authors: Hunkeler FJ
Published: December 2008

A comparison of the basic properties of tantalum with other high-performance metals and alloys used in the chemical process industry (CPI) is given. It is pointed out that the electrochemically passivating oxide film that spontaneously forms on tantalum is responsible for its extraordinary performance. It is the premier example of this type of corrosion resistance and accounts for tantalum having the most effective resistance over the broadest range of acidic media conditions. The fabrication characteristics of tantalum and the variety of equipment available are described. Tantalum's performance characteristics and limitations in several CPI environments are discussed in relation to other commonly used metals.
Application of a Dynamic Leaching Test to Solidified Hazardous Wastes
Authors: Côte PL , Isabel D
Published: December 2008

A dynamic leaching test using a fixed leachant renewal schedule developed for testing nuclear waste forms was not found to be widely applicable to solidified hazardous wastes because of the large range of leachability encountered and because of limitations in the analytical detection of the chemical species in the leachate. The data generated could be interpreted using a simple diffusion model. The range of measured diffusivities, from 10−15.5 to 10−8.4 cm2/s, was covered by using a variable leachant renewal schedule. The precision associated with any single determination was approximately one order of magnitude.
Effect of Chemical Treatment of Fly Ash on the Leaching of Metals
Authors: Young HW , Young JC , Boybay M , Demirel T
Published: December 2008

An investigation was conducted to determine the ability of chemical treatment to reduce the leaching of metals from fly ash. A further objective was to determine the effect of cofiring refuse-derived fuels with coal on leachate composition. Samples of fly ash were treated with portland cement, chemically pure lime, and phosphoric acid and subjected to a column leaching process. The leachates were composited weekly and analyzed using X-ray fluorescence and atomic absorption spectrometry.

Portland cement or lime reduced the quantity of leached arsenic 40 to 80% from the control samples, whereas those samples fixed with phosphoric acid yielded 50 times more arsenic. Generally, the samples treated with portland cement showed the most uniform reduction in leachate concentrations.

Leachates from fly ash produced upon cofiring refuse-derived fuel with coal showed consistently higher concentrations of all elements except for calcium, selenium, and alkalinity.

Compaction and curing of the chemically treated ash samples showed little improvement in the ability to control the amount and types of metals appearing in leachates.
Attenuation of Heavy Metals Within Municipal Waste Landfill Sites
Authors: Young PJ , Baldwin G , Wilson DC
Published: December 2008

The Waste Research Unit has developed several laboratory tests to investigate the attenuation of toxic species disposed to landfill, to provide pragmatic guidance for environmentally acceptable codisposal of industrial and municipal wastes. Sevencolumn experiments were set up to investigate the fate of eight metals (cadmium, chromium, copper, iron, lead, mercury, nickel, and zinc) released in solution onto pulverized municipal waste. Leachate and destructive analysis revealed that only nickel migrated through 0.5 m of waste, giving typical leachate concentrations of 20 mg/dm3, although upwards of 80% of the nickel was removed from solution. The other metals were precipitated or absorbed very rapidly and were mainly found in the top 0.2 m. Fatty acid production was completely inhibited by the immobilized metals, leading to near-neutral pHs in these areas. Penetration of the dissolved metals was greater with a continuously applied dilute solution than with a brief dose of comparable loading.
Energy Recovery from Agroindustrial Wastes with Prevalently Solute Pollutants Using Fixed-Bed Anaerobic Reactors
Authors: Sanna P , Camilli M
Published: December 2008

A process for anaerobic digestion of agroindustrial wastes containing mainly soluble pollutants has been developed utilizing fixed-bed reactors.

A pilot plant at a sugar refinery with two reactors in parallel, respectively of 10 and 50 m3 operating volume, has functioned successfully in treating wastes produced in regenerating ion-exchange columns used to purify the sugar juices. With an hydraulic retention time (HRT) of less than one day, a maximum gas production of 11.5 volumes per operating volume of reactor per day was obtained together with a reduction of up to 80% of the biological oxygen demand for five days (BOD5), and volatile solids and up to 70% of the chemical oxygen demand (COD).

The gas contained from 70 to 75% methane.

On the basis of these results, a full-scale industrial plant was built which has produced up to 7500 m3 a day of biogas. The process has been found suitable for a large number of industrial wastes, especially when plants are seasonally operated.
Hazardous Waste Landfill Research
Authors: Schomaker NB
Published: December 2008

The hazardous waste land disposal research program is collecting data necessary to support implementation of disposal guidelines mandated by the Resource Conservation and Recovery Act of 1976 (RCRA) (PL 94-580). This program, relating to the categorical areas of landfills, surface impoundments, and underground mines, encompasses state-of-the-art documents, laboratory analysis, economic assessment, bench and pilot studies, and full-scale field verification studies. Over the next five years the research will be reported as technical resource documents (TRDs) in support of the Permit Writers Guidance Manuals. These manuals will be used to provide guidance for conducting the review and evaluation of land disposal permit applications. This paper presents an overview of this program and reports the current status of work in the various categorical areas.
Effect of Warm Prestressing on Fatigue Crack Growth Curves at Low Temperatures
Authors: Katz Y , Bussiba A , Mathias H
Published: December 2008

Low-temperature fatigue crack extension is studied in precracked single-edge-notched specimens of AISI 4340 steel. Steady-state crack extension in tension-tension fatigue and cyclic loading in conjunction with warm prestressing (WPS) are particularly emphasized. Effects of WPS on the fatigue crack growth curve are demonstrated and discussed. Special attention is given to the cleavage fracture mode, which dominates the features of the fatigue crack growth curve below the ductile-brittle transition (DBT) temperature. In AISI 4340 steel, which is characterized by DBT, WPS affects the alternative fracture mode and therefore alters the lower and upper bound values Kth and KIfc, respectively. For a more complete view, the behavior of AISI 304 stainless steel is discussed. The experimental results at low temperatures are mainly interpreted in terms of a transition in the cumulative crack tip damage process, induced by characteristic values of the stress intensity range amplitudes (ΔK).
Design of Laminated Fibrous Composite Plates with Required Flexural Stiffness
Authors: Miki M
Published: December 2008

A new material design method of laminated fibrous composite plates with required flexural stiffness is proposed. The selection of kinds of fibers and matrices and the determination of fiber orientation angles can be done directly from the imposed conditions on flexural stiffness of laminated plates.

The laminated composites intended for this study are multiple balanced angle-ply symmetric laminates with one kind of unidirectional lamina.

A newly constructed diagram for flexural lamination parameters which are functions of the fiber orientation angles, and which appeared in Tsai's expression for evaluating the flexural stiffness of laminates, made it possible to determine the design specifications based on flexural effective engineering constants of laminates. A certain stacking sequence of laminates is indicated as a point in the diagram on which contours of flexural stiffness can be drawn. Using these contour lines, the design specification is easily determined as a point on this diagram. Thus, the point can be called a design point.

It became possible to specify the fiber orientation angle of each ply and the stacking sequence using the flexural lamination parameters indicated as the point on the diagram.
Design for Ultimate Strength with a Chopped Glass-Filled Phenolic Composite: Critical Flaw Sensitivity, Residual Stress, Fiber Orientation
Authors: Nimmer RP , Trantina GG
Published: December 2008

Because they retain strength and stiffness at temperatures as high as 180°C (356°F), injection molded, glass-filled phenolic composites have been used in structural applications. However, the strength of this material as measured with ASTM three-point flexure tests may be as much as 80% higher than the strength measured in tension tests. The objects of this investigation were to study the relative effects of fiber alignment, residual stress, and flaw distribution upon these measured values of strength and to assess the application of these data to the design process. There was no differential alignment of fibers observed between skin and core areas of the specimens which might lead to elevated flexural strengths. Residual compressive stresses between 7 MPa (1.0 ksi) and 14 MPa (2.0 ksi) were measured at the surface of the bend specimens. Finally, although the tensile strength data are well represented by a two-parameter Weibull model, there remains a 30% unexplained discrepancy between predicted and measured flexural strength.
The Effects of Pore Pressure and Confining Pressure on Pore and Bulk Volume Compressibilities of Consolidated Sandstones
Authors: Zimmerman RW , Haraden JL , Somerton WH
Published: December 2008

A computer-controlled system has been devised that allows measurement of pore and bulk compressibilities of porous rocks over a full range of pore and confining pressures. Pore compressibilities have been measured for Bandera, Boise, and Berea sandstones. It is shown from these data that the pore compressibilities of these sandstones are functions of the difference between the confining pressure and the pore pressure. A simple physical explanation for this behavior is then given in terms of the closure of very fine microcracks in the rock.
A Flat Insulation Tester That Uses an Unguarded Nichrome Screen Wire Heater
Authors: McElroy DL , Graves RS , Yarbrough DW , Moore JP
Published: December 2008

An unguarded, unidirectional heat flow technique is described for measuring the apparent thermal conductivity (λa) of insulating materials in the range 300 to 330 K. Vertical heat flow is generated by a 0.9 by 1.5 m electrically heated nichrome screen that is instrumented and sandwiched between two specimens. The specimens are bounded by two temperature-controlled copper plates. The system has been used to measure λa of fiber glass batts and obtain data that show the effects of density, temperature, temperature difference, thickness, plate emittance, and heat flow direction on λa. A determinate error analysis indicates a λa measurement uncertainty of ±1.7%. The system repeatability and reproducibility were found to be ±0.2%. The measured performance of the tester agrees with that predicted by a thermal model. Analysis of the transient characteristics of the screen when it is subjected to a step change in power suggests that the apparatus can be used to determine apparent thermal diffusivity.
Indentation Hardness and Its Measurement: Some Cautionary Comments
Authors: Tabor D
Published: December 2008

This paper discusses some of the main developments in our understanding of indentation hardness during the last 20 years and indicates the limitations of several current models. In particular, it deals critically with the expanding spherical cavity as applied to elastic-plastic solids and to solids with marked creep. It also discusses the problem of load application, the indentation behavior of single crystals, the hardness of semiconductors, and recent developments in crack formation by indentations in plastic-brittle solids. Finally, it deals with the more specific problem of hardness at extremely small loads and the practical as well as theoretical difficulties involved in characterizing microhardness in terms of depth of penetration.
Biodurability Evaluation of Medical-Grade High-Performance Silicone Elastomer
Authors: Frisch EE , Langley NR
Published: December 2008

A new silicone elastomer provides maximum resistance to flexural fatigue, crack growth, and the high durability required in an elastomer used as a material of construction for the flexible-hinge finger and toe joint implants designed by A. B. Swanson, M. D. The high-performance characteristics of this new elastomer are derived from its excellent physical properties, particularly its exceptionally high tear propagation strength (ASTM Test for Tear Resistance—Rubber Property (D 624-73), Die B) and high resistance to crack propagation (ASTM Test for Rubber Deterioration—Crack Growth (D 813-59)). In vitro testing indicated its use in finger joint implants would provide excellent flexural durability. Biocompatibility evaluations to qualify this new material for clinical use included chronic biodurability studies. Test specimens were implanted subcutaneously in dogs and retrieved at various time intervals for periods up to two years. Physical properties of test and control specimens were compared. The properties measured included tensile strength, tensile stress, ultimate elongation, tear strength (Die B), and flaw propagation characteristics. All testing was done by ASTM standard methods except for flaw propagation measurements where implantability limitations in specimen size mandated use of a smaller specimen than required in standard test methods. Thus, a flaw propagation test method was specifically designed for this experiment.

The findings indicated that this new high-performance silicone elastomer had excellent biodurability. The performance characteristics evaluated in test and control specimens were stable over the two-year implant time. Lipid absorption stabilized at approximately 1.5%, a level reached relatively early after implantation and remaining constant thereafter, apparently representing the lipid saturation level when this elastomer is implanted subcutaneously in the dog.
Void-Precipitate Association During Neutron Irradiation of Austenitic Stainless Steel
Authors: Pedraza DF , Maziasz PJ
Published: December 2008

Microstructural data have recently become available on a single heat of 316 stainless steel irradiated in EBR-II and HFIR, over a wide range of irradiation temperatures (55 to 750°C), doses (7 to 75 dpa), and several helium generation rates (0.5 to 55 atomic ppm He/dpa). Results on just one heat of steel minimize effects that may be related to compositional differences. In this work we present these data in order to offer a characterization of precipitate-void association within the context of the overall microstructural evolution. Observations on a second heat of steel are also presented here to allow us to assess which microstructural correlations are general. The analysis of experimental results leads us, first, to conclude that precipitate-void association is not only dependent upon local conditions at the precipitate interface but is also strongly related to the overall microstructural evolution. Second, we suggest a precipitation mechanism that helps to understand precipitate-void codevelopment.
A Comparison of the Relative Importance of Helium and Vacancy Accumulation in Void Nucleation
Authors: Stoller RE , Odette GR
Published: December 2008

Void nucleation in irradiated austenitic stainless steels generally requires the presence of either residual or transmutant gases. Classical nucleation rates are much too low to account for the number of voids observed at temperatures greater than about 450°C. An alternate path is generally believed to be responsible for void formation; namely, the growth of gas-stabilized bubbles until they reach a critical size beyond which further gas accumulation is not required to promote growth. Two limiting paths can be envisioned for void nucleation on a population of sub-critical helium/vacancy clusters; one is limited to growth by helium accumulation alone and the other to growth by stochastic fluctuations in the vacancy accumulation. As bubbles approach the critical size, stochastic processes could begin to contribute to the void nucleation rate. A comparison is made of nucleation rates along these two limiting paths as a function of the gas content of the clusters. The calculations indicate that the gas accumulation path is generally dominant, particularly at higher temperatures and for lower gas contents. The fraction of the critical size required for the vacancy path to contribute to the total nucleation rate increases with temperature. The results confirm the important role of transmutant helium in promoting void swelling.
Performance of Dolostone and Limestone Concretes at Sustained High Temperatures
Authors: Carette GG , Malhotra VM
Published: December 2008

This report gives results of a laboratory study undertaken to evaluate the relative performance of limestone and dolostone aggregate concretes under sustained exposure to high temperatures. For each type of concrete, three water/cement (W/C) ratios ranging from 0.33 to 0.60 were investigated. The test specimens were exposed for up to four months to temperatures ranging from 76 to 600°C. The conditioning of the specimens prior to any temperature exposure consisted of moist curing for 28 days followed by storage under room conditions for 26 weeks.

The test results show the dolostone aggregate to be unstable under a sustained temperature of 150°C, confirming the results of a previous investigation. Such instability is again attributed to the slow oxidation of the pyrite contained in some of the aggregate particles. The resulting expansion causes disintegration of the aggregate and rupture of the concrete. Under similar exposure, concrete made with a limestone aggregate is found to be unaffected.

Except for these results, the loss of compressive strength of the specimens under exposure is generally independent of the type of aggregate and is proportional to the temperature. At temperatures of 150°C and higher, an increase in the length of exposure from 48 h to four months results in further decrease in strength. In all cases, however, any major strength loss is found to occur within the first month of exposure. In general, the leaner concretes are slightly less affected than the richer concretes in terms of relative strength loss after exposure.

Both pulse velocity and resonant frequency measurements appear to provide excellent means of monitoring the compressive strength loss during exposure.
Welding Institute Research on the Fatigue Precracking of Fracture Toughness Specimens
Authors: Towers OL , Dawes MG
Published: December 2008

Three techniques are described for growing uniform fatigue cracks in fracture toughness specimens originally containing welding residual stresses. These are local compression, reverse bending, and the use of a high R-ratio in the fatigue cycle. The possible effects of the techniques on the subsequent measurements of fracture toughness are assessed. The relative merits of the three techniques are summarized, and the main conclusion reached is that local compression is the best defined technique at present, and that reverse bending and high R-ratio, although probably more convenient, require further research and development.
Cleavage Fracture of Steel in the Ductile-Brittle Transition Region
Authors: Rosenfield AR , Shetty DK
Published: December 2008

Fracture-toughness experiments on ASTM A508 (Unified Numbering System [UNS] K13502) steel within the ductile-brittle transition region are a combination of both ductile and brittle behaviors, leading to severe data scatter. Both crack blunting and dimpled rupture are terminated by unstable cleavage. At a lower test temperature, cleavage during blunting predominates, whereas at a higher test temperature, cleavage tends to occur after some stable crack growth. It is suggested that this behavior results from the existence of a distribution of “trigger” sites in the microstructure (for example, inclusions and carbides). Methods for eliminating the dimpled-rupture contribution to the test record are discussed and are shown to be useful for predicting large-specimen behavior.
A Study of the Thermal Behavior of Brick Under Service Conditions in a Structure
Authors: Yi FL , Carrasquillo RL
Published: December 2008

The main purpose of this paper is to present results of a three year research project conducted at The University of Texas at Austin on the development of a test procedure for determining the coefficient of thermal expansion of brick under service conditions in a structure. Many currently used masonry design and construction practices are the result of past experience. With the development of new design methods and construction techniques for brick masonry, a better understanding of the thermal behavior of brick is needed. Unaccounted thermal-induced movements in brick masonry have been the reason for observed cracking in brick masonry walls in many structures in service today.

In the study reported herein, the effects of moisture conditions including dry, 50 percent of saturation, and saturated, and of number of temperature test cycles ranging from −18 to 60°C (0 to 140°F) under a given moisture condition on the observed thermal behavior of new (unused) bricks in three directions (length, height, and width) was determined. Strain gages bonded to the surface of each specimen in the direction of measurement were used to monitor temperature-induced movements in the brick continuously during testing. The effect of location of the strain gages on the surface of the brick in each direction on the observed behavior was also determined. The thermal behavior of several brick specimens removed from existing structures after years in service was also observed in order to correlate the results obtained using new brick specimens.

A proposed test method in the form of ASTM standards was developed for determining the coefficient of thermal expansion of bricks under expected service conditions in the structure. Information obtained from this test is needed by practicing engineers in the design of expansion joints in brick masonry to ensure safe and durable structures.
Fixed-Wall Versus Flexible-Wall Permeameters
Authors: Daniel DE , Anderson DC , Boynton SS
Published: December 2008

Permeameters are of two general types: fixed-wall and flexible-wall cells. A controversy has developed over which type of cell is best suited for measuring the hydraulic conductivity of relatively impermeable, fine-grained soils. The various types of permeameters are discussed and their relative advantages and disadvantages are listed. Differences in applied stress, boundary leakages, and degree of saturation are the major differences between cells. It is concluded that no one type of cell is best suited to all applications. Data show that the type of permeameter used has little effect for laboratory-compacted clay permeated with water but can have a major effect for clays permeated with concentrated organic chemicals. Fixed-wall cells are perhaps best suited to testing laboratory-compacted clays that will be subjected to little or no effective overburden pressure in the field. Flexible-wall cells are better suited to testing undisturbed samples of soil (to minimize boundary leakages) and testing soils that will be subjected to significant effective stress.
Sediment Toxicity, Contamination, and Macrobenthic Communities Near a Large Sewage Outfall
Authors: Swartz RC , Schults DW , Ditsworth GR , DeBen WA , Cole FA
Published: December 2008

Sediment toxicity, contamination, and macrobenthic community structure were examined in 1980 at seven stations along a pollution gradient from the Los Angeles County Sanitation Districts' sewage outfalls on the Palos Verdes Shelf, CA, to control conditions in Santa Monica Bay. Sediment toxicity was determined by laboratory bioassays with the phoxocephalid amphipod, Rhepoxynius abronius. Distribution and abundance of the macrobenthos were generally consistent with the Pearson-Rosenberg model and the Bascom-Mearns-Word quantitative classification of macrobenthic assemblages. Species richness, density, and biomass increased greatly in areas of moderate sediment organic enrichment, but decreased to or below control conditions near the outfalls. The Infaunal Index of changes in benthic community structure in response to organic enrichment increased with distance from the outfalls. Dominant species changed from the opportunistic polychaete, Capitella capitata, near the outfalls; to the clam, Parvilucina tenuisculpta, and the polychaetes, Mediomastus californiensis and Tharyx sp. A in areas of moderate organic enrichment; to the brittlestar, Amphiodia urtica, at the control station. Sediment toxicity was significantly greater than control levels at the three stations closest (≤3 km) to the outfalls. There were significant increases in the concentration of most sediment contaminants and significant decreases in the richness and abundance of the benthos at stations where sediment was actely toxic to Rhepoxynius abronius. Organic enrichment and anaerobic sediment conditions appear to be the dominant anthropogenic influences on the macrobenthos of the Palos Verdes Shelf. Toxicity caused by chemical contamination may contribute to the absence of amphipods near the sewage outfalls.
Application of the Standard Fire Curve for Expressing Natural Fires for Design Purposes
Authors: Wickström U
Published: December 2008

A method suitable for design purposes is presented which allows postflashover compartment fires to be expressed in one single curve; time is then modified or scaled to take into consideration ventilation conditions and wall properties. Ventilation-controlled combustion, uniform temperature, and wall losses proportional to the thermal inertia of the wall material are assumed. Although the proposed method allows the designer to consider important parameters, it is still very approximative and must be used with care. Several assumptions are made, and many parameters are difficult to assign values in the general case. The method therefore should be looked upon as an improvement of the current technique of carrying out fire engineering design by simply employing a standard curve like ISO 834.

An analysis of the postflashover compartment fire, basically the same as has been presented elsewhere, is summarized. The parameters of ventilation and wall properties are grouped together in such a way that their influence on the temperature development may be expressed as a time factor. It is further shown that for certain parameter values the fire temperature response in the heating phase nearly coincides with the ISO 834 standard curve. Therefore, as this curve is well-established in fire engineering, it is suggested that it be employed with the here suggested method; the time scale, however, is modified with a compartment time factor depending on the properties of the fire compartment.

The assumed fire temperatures may be used to estimate the temperature in fire-exposed structures. It is demonstrated how very compact diagrams may be used for concrete structures, which allows the designer to take into account various fires and thermal material properties of the structure. The diagrams were obtained from finite-element computer calculations in which various fires and material properties were simulated. By then plotting the temperature response versus suitable parameter groups, it was possible to present the results in a very compact way. Corresponding diagrams have earlier been presented for insulated steel structures [1].
Fatigue Crack Path Behavior Under Polymodal Fatigue
Authors: Hourlier F , d'Hondt H , Truchon M , Pineau A
Published: December 2008

The study is devoted to the prediction of crack path direction in polymodal fatigue. First experimental and theoretical results published in the literature are reviewed. It is shown that proportional and nonproportional loading conditions should be distinguished. Then, the experimental results obtained in cyclic Mode III and biaxial nonproportional Modes I + II loading are presented. These tests were carried out on two alloy steels and an aluminum alloy. The biaxial tests were performed on cruciform type specimens.

In Mode III loading, it is shown that, at low applied torque, the crack surface adopts a “factory-roof” appearance with facets characteristic of local Mode I extension. It is suggested that the flat surfaces corresponding to apparent macroscopic Mode III extension observed in this study as in other ones might be an artefact. In Modes I + II loading, it is shown that the two investigated materials exhibit very different crack bifurcation angles. The results are discussed in terms of possible extended forms of the maximum tangential stress criterion, ΔkImax*, KImax* and (da/dN)max. It is shown that, as a general rule, the latter criterion gives results in better agreement with the experiments. The difficulties associated with crack closure effect are also shortly discussed.
Multistage Triaxial Testing: A Rational Procedure
Authors: Nambiar MRM , Rao GV , Gulhati SK
Published: December 2008

It is difficult to obtain enough undisturbed submarine samples from a particular location to carry out triaxial compression tests in the conventional manner using three samples at three different cell pressures. Multistage triaxial tests offer an attractive means for determining shear strength parameters of submarine soils since they use only a single sample. This paper presents a study through which a rational procedure for multistage undrained triaxial testing of submarine soils has been evolved.

For this purpose tests were conducted on laboratory sedimented kaolinite. This rational procedure was then used to determine shear behavior of a submarine soil from off the west coast of India and then verified by comparing it with conventional tests. It is shown that to ensure sufficiently good correspondence between results obtained from conventional and multistage testing, the sample in multistage testing must not be sheared to failure in each stage. The sample should be sheared to about 2 to 4% axial strain in each stage, and then failure condition predicted by using Kondner's hypothesis and extrapolating to a finite strain. The influence of finite strain as well as the cell pressure to be used in successive stages of the multistage test has been studied and suitable recommendations have been made.