bluuebunny/crossref_metadata_2025_split huggingface dataset:
Suitable Steady-State Methods for Measurement of Effective Thermal Conductivity in Rigid Insulations
Authors: Engelke WT 
Published: March 2009

The ASTM Test for Thermal Conductivity of Materials by Means of the Guarded Hot Plate (C 177-63) is a recognized technique for measurement of thermal conductance of insulations. This method may not be the optimum choice due to temperature range, material availability, and other factors. This paper describes three other steady-state techniques that may be used. Two are modifications of the basic comparative rod apparatus, and the third is a modification of the radial inflow apparatus. The two modifications of the comparative rod apparatus are designed to minimize or monitor or both the axial heat bypass and radial heat interchange effects. The modification to the radial inflow apparatus converts a cylindrical specimen to obtain heat flows through a plane surface. These modifications represent an improvement in the state of the art.
The advantages of these procedures over the ASTM C 177-63 apparatus are smaller specimen size and wider temperature range. The disadvantages are that the precision and accuracy are not as good as that for the ASTM C 177-63 apparatus; however, an acceptable level for most engineering data may be obtained (&lt; ±12 percent).
Data on various candidates for the reusable surface insulation of the shuttle were measured by these methods and are reported.
New Development in Design of Equipment for Measuring Thermal Conductivity and Heat Flow
Authors: Brendeng E , Frivik PE 
Published: March 2009

Thermal conductivity of materials and heat transmission through complex structures have been studied for many years at the Refrigeration Division of the Trondheim University. This paper describes some of the recent developments in test equipment design and operation.
One fully-automatic guarded hot plate apparatus of the unidirectional type for high accuracy has been put in operation. It is capable of measuring at cold plate temperatures between 80 and 330 K at a typical difference of 10 K. A special method of accelerated balancing was introduced, and is used successfully for a number of different measuring purposes. A description of the control system is given.
The study of convection influence in full-size insulations is continued. A part of this work is done using a large-scale hot box apparatus with a special edge design. Further, a large guarded hot plate equipment with a measuring area of 2 by 3 m2 for the same purpose is under construction. The temperature range for this equipment has been extended to 90 K on the cold side with a view to the testing of liquid natural gas tank insulations.
Another important project concerns the heat transmission in natural ground freezing and the use of insulation for frost protection. Three guarded hot plate apparatus of special design are built to measure thermal conductivity of soils and building materials. These apparatus operate at cold plate temperatures between 200 and 320 K.
Some work on the development of transient methods for heat conductivity measurement is also recorded.
Thermal Conductivity of Evacuated Glass Beads: Line Source Measurements in a Large Volume Bead Bed Between 225 and 300 K
Authors: Langseth MG , Ruccia FE , Wechsler AE 
Published: March 2009

Line source measurements of thermal conductivity have been made in a large tank of evacuated glass beads that were used as a thermal simulator for the Lunar Heat Flow Experiment. Measurements were made with two 3/16 inch diameter probes 87 inches long that contained five (5) evenly spaced thermocouples and a double filament heater wire. The probes were inserted vertically from the top into the bead bed, which allowed ten (10) measurements of conductivity to be made over an interval of depth of 55 inches in tank. Power densities used ranged from 1.2 to 2.2 MW/cm. The bead tank is 21 inches in diameter by 86.75 inches in depth with temperature control at the outer walls. This tank was contained in a vacuum chamber that could be evacuated to gas pressure 10−5 to 10−4 Torr. Measurements were made at various bead bed temperatures between 225 and 300 K.
Measurements at 225 K gave a range of conductivity values from 1.0 to 4.0 × 10−4 watt/cm ∙ K. The conductivity increased uniformity over the interval of depth measured. Extrapolation of the values to the surface of the bead tank indicates an average conductivity of 0.7 × 10−4 wattcm K. Measurements using the Lunar Heat Flow Experiment probes at 225 K yield values in good agreement, ± 10%, with the line source data. All of the probe qualification tests were made at 225 K. These comparisons demonstrate that valid conductivity measurements can be made with the heat flow probe.
The increase in conductivity with depth is due to an increase in compressive stress. However, the observed increase at 225 K is much greater than would be expected from “hydrostatic” loading alone. Measurements at higher bead bed temperatures, 246 K and 258 K, yield lower values of conductivity. If the increase of conductivity with depth is due to “hydrostatic” loading alone, an increase of conductivity with increasing temperature would be expected. The opposite observed effect suggests that compressive stresses from thermal contraction of the bead jacket are important.
Concept of a Bacterial Species: Importance to Writers of Microbiological Standards for Water
Authors: Farmer JJ , Brenner DJ 
Published: March 2009

A bacterial species is operationally difficult to define. There is considerable phenotypic variation in some species, such as Escherichia coli; thus, the limits of the species are difficult to determine. Other species such as Edwardsiella tarda and Serratia marcescens are “tighter” because the strains which comprise these species show little phenotypic variation. The latter species are easier to define biochemically.
Newer taxonomic techniques have been helpful in defining bacterial species. Often, the results have agreed with those obtained by conventional methods. However, species such as Enterobacter agglomerans have been shown by DNA-DNA hybridization to be composed of over twelve different hybridization groups which could be considered “new species.”
Many different bacterial species are washed from the soil into water. Some of these are soil bacteria; others make up the gut flora of insects, invertebrates, and lower vertebrates. Often, these environmental species are closely related to species known to be pathogenic for man. Sometimes environmental isolates can be differentiated from the human pathogens by simple tests; S. liquefaciens and S. rubidaea are phenotypically different from the human pathogen S. marcescens and can be recognized easily. Environmental strains of Klebsiella, for which the taxonomy has not been completely defined, cannot yet be differentiated from the human pathogens. Similarly, in Enterobacter, Citrobacter, Proteus, Vibrio, Pseudomonas, Aeromonas, and other groups, there are taxonomic gaps where species lines are not completely clear. Many isolates that have been classified in these genera may not be pathogenic for man. Consequently, to ensure that standards will have relevance in public health, writers of microbiological standards for water should proceed very carefully in their treatment of indicator organisms. Many species in water are probably not pathogenic for humans but are closely related to species which are pathogenic. Even with a complete battery of biochemical and serological tests, isolates cannot always be assigned to their correct species. We see many isolates which probably belong to new species which have not been defined.
Total Coliform Bacteria
Authors: Mack WN 
Published: March 2009

Although the total coliform bacterial count has its shortcomings, it is our best indicator of the health hazards associated with drinking water that we have today. Some of these defects can be corrected by additional bacterial tests to determine interference or identify nonconliform lactose fermenting organisms. Occasionally drinking water samples containing viruses have given negative tests for coliform bacteria when tested by the standard methods. Concentration methods used to recover viruses in water samples have shown that the coliform organisms were present but in an insufficient number to be indicated by the routine standard methods.
Suggestions are given for the search for a better method to detect bacterial pollution in drinking water.
Intergranular Corrosion in Nuclear Systems
Authors: Taboada A , Frank L 
Published: March 2009

The occurrences of intergranular stress-corrosion cracking in nuclear power plant components made of austenitic alloys are discussed. Cracks of this type have occurred in sensitized Types 304 and 316 austenitic stainless steels in a variety of components at various stages of fabrication. Historically, cracking in early reactors occurred in heavily sensitized material or were related to the presence of chlorides or caustic ions. More recently, a rash of cracks were found in boiling water reactor piping adjacent to welds. This problem is evaluated.
Wastage and intergranular cracking of Inconel 600 alloy tubing of steam generators has occurred in the secondary side in plants that have used either sodium phosphate or all volatile water treatment. Design and environmental factors have had a pronounced influence on the tube degradation. The significance of these conditions is discussed, as is action taken by the Nuclear Regulatory Commission relating to this problem.
Inelastic Micromechanical Analysis of Graphite/Epoxy Composites Subjected to Hygrothermal Cycling
Authors: Miller AK , Adams DF 
Published: March 2009

Results are presented of an inelastic finite-element analysis of the residual microstress state in a unidirectional graphite/epoxy composite subjected to temperature cycling from room temperature (294 K) to 405 K or a combined cycle of changing matrix moisture content from a saturated condition (5.6 percent water by weight) to 2.0 percent moisture content with a simultaneous temperature change from room temperature to 339 K. In the analysis, the graphite fibers are modeled as being transversely isotropic, and assumed temperature- and moisture-dependent properties of modulus and strength for epoxy are utilized.
The results indicate that relatively large residual microstresses result from the cooldown of the composite from the curing temperature (450 K) to room temperature, and that in portions of the matrix material the residual stresses nearly exceed the yield strength of the material for a 60 percent volume composite. It is shown that moisture saturation of the matrix causes matrix yielding in both 40 and 60 percent fiber volume composites. It is noted that subsequent thermal cycling, or hygrothermal cycling, promotes definite changes in these microstress states which cause dimensional instability of the composite.
Uniaxial, Biaxial, and Fatigue Properties of Polyester Fiber Glass
Authors: Irwin LH , Dunlap WA , Compton PV 
Published: March 2009

Uniaxial flexure and tension tests and biaxial flexure tests were performed on two systems of fiber glass-reinforced polyester (FRP) and also on an FRP-polyurethane foam composite to evaluate their suitability for possible use as expedient paving materials. The principal parameters studied were ultimate strength, elastic modulus, and fatigue behavior.
Results of the uniaxial tests were found to compare favorably with the results of the biaxial tests. A method of stress analysis for the biaxial tests was developed to accommodate a center loaded, clamped, circular plate subjected to large deflections and having radial forces on the boundary.
From the results of the research it was found that factors affecting the volume proportions of resin, glass, and air, and factors affecting the properties of the resin could have an influence on the properties of the FRP, in accordance with the “rule of mixtures” [11]. Both the ultimate-strength test results and the fatigue tests results indicated that Materials Systems A was superior to Materials System B.
Mechanical and Physical Properties of Advanced Composites
Authors: Freeman WT , Kuebeler GC 
Published: March 2009

The mechanical and physical properties of graphite, glass, PRD-49, and boron epoxy composites are compared with today's commonly used industrial materials to illustrate the many unique design alternatives available with advanced composite materials. Mechanical properties and the fatigue, creep, impact, thermal expansion, thermal conductivity, specific heat, electrical properties, wear, and friction characteristics of the materials are summarized. The purpose of each comparison is to show where performance improvements can be achieved by replacing present materials with advanced composite materials.
Cost advantages in the use of these materials are briefly discussed. Increased performance, increased productivity, longer service life, and less component maintenance should outweigh today's higher material costs of advanced composites.
Reinforcement of Metals with Advanced Filamentary Composites
Authors: Herakovich CT , Davis JG , Dexter HB 
Published: March 2009

This paper reviews some recent applications of the concept of reinforcing metal structures with advanced filamentary composites, and presents some results of an experimental investigation of the tensile behavior of aluminum and titanium reinforced with unidirectional boron/epoxy. Results are given for tubular and flat specimens, bonded at either room temperature or elevated temperature. The composite reinforced metals showed increased stiffness over the all-metal counterpart, as predicted by the rule of mixtures, and the results were independent of specimen geometry.
The tensile strength of the boron/epoxy reinforced metals is shown to be a function of the geometry of the test specimen and the method of bonding the composite to the metal. The ultimate strength of the tubular specimens and a flat modified dogbone specimen, both bonded at elevated temperature, and a flat coupon specimen bonded at room temperature showed good agreement with predicted values, which are well above the metal counterpart. Flat coupon specimens bonded at an elevated temperature exhibited early failures, which were as much as 40 percent below predicted values.
Plastic Deformation Processing and Compressive Failure Mechanism in Aluminum Composite Materials
Authors: Chang M , Scala E 
Published: March 2009

Analytical models are presented for: (1) monolayer composite fabrication, (2) consolidation of monolayer composites into plates, and (3) composite deformation under transverse compression. Upper-bound solutions of the models are developed by using the limit analysis of plastic theory. These solutions depend on (1) the flow stress of the matrix material, and (2) frictional coefficients for the fiber-matrix and for the matrix-die interfaces. They were determined experimentally from compression ring tests.
The analytical predictions of the average consolidation pressure are in good agreement with experimental results for an aluminum matrix from room temperature to 750°F (399°C). Transverse compression deformations were examined by several methods including scanning electron microscopy for aluminum-steel wire, aluminum-Borsic, and aluminum-nickel unidirectionally solidified composites. The analytical predictions for flow line directions from a proposed strip compression model agree with the experimentally determined angles.
Correlation Between the Fatigue-Crack Initiation at the Root of a Notch and Low-Cycle Fatigue Data
Authors: Baus A , Lieurade HP , Sanz G , Truchon M 
Published: March 2009

Fatigue-crack initiation was investigated by testing high-strength steels (AFNOR 35 NCD 16 and 35 CD 4) with 0.6-in. (15-mm) thick ASTM compact specimens having various notch-root radii between 0.003 in. (0.07 mm) and 0.04 in. (1 mm).
Measuring devices were used to detect flaws with a surface area of only a few square millimetres in their propagation planes.
In order to calculate the number of cycles required to initiate a crack, notch root behavior was investigated through several parameters. − ΔK/ √ρ, from linear-elastic fracture mechanics, which concentrate results when the initiation time is large; − KfEP, an experimental parameter derived from low-cycle fatigue data when Ni&lt;105 cycles. In this case, the ratio between theoretical and experimental values of the initiation time is between one and two for a given nominal stress.
Fatigue-Crack Propagation in Electroslag Weldments
Authors: Kapadia BM , Imhof EJ 
Published: March 2009

The paper discusses the results of an investigation of fatigue-crack propagation behavior of as-deposited electroslag weldments in two hot-rolled structural steels, ASTM A36 and ASTM A588 Grade A. Fatigue-crack growth tests were conducted on 1T wedge-opening-loading (WOL) specimens machined from six 1-in.-thick and four 4-in.-thick weldments that were representative of electroslag welds for bridges. The testing was done in air at room temperature under tension-to-tension sinusoidal loading. Various orientations and locations of the fatigue crack in relation to the weld geometry were investigated.
The fatigue-crack growth rates (da/dN) in the weldments were similar to, or up to five times slower than, the rate in the base steels. The retardation in crack-growth rate was most pronounced at low values of the stress-intensity factor range (ΔK) and was substantially greater for crack propagation in the coarse-grained heat-affected zone (HAZ) and bond-line regions than in the weld metal. Marked variations in the microstructure of the weld metal and HAZ had no signficant influence on crack-propagation behavior, which appeared to be influenced primarily by the residual stresses in the weldments as discussed in a separate paper.
The results of this study show that the upper bound of the crack-growth behavior for low-strength structural steels may be used as a conservative estimate of the crack-propagation behavior of as-deposited electroslag weldments in such steels. On this basis, the prediction of the service life of electroslag-welded structures subjected to cyclic loads, and the determination of safe inspection intervals, may be made by the same approach as that presently used for standard structural-steel weldments made by other processes.
Fatigue Growth of Surface Cracks
Authors: Cruse TA , Meyers GJ , Wilson RB 
Published: March 2009

Fatigue-crack growth in gas-turbine engines generally involves surface initiated cracks of semielliptical shape (surface crack) or quarter-elliptical shape (corner crack). Such cracks initiate in regions of locally high stresses and stress gradients. A major aspect of the design system prediction of cyclic growth of these cracks is the development of efficient yet accurate fatigue-crack growth analytical models.
A major advance in modeling accuracy and efficiency has been achieved through the combined use of boundary-integral equation models of three-dimensional crack problems and a weight function representation of elliptical crack growth. Surface and corner crack-fatigue growth data have been compared to the results predicted by the design system analytical model. In general, excellent agreement has been obtained. Some questions concerning the important features of surface and corner-crack growth as well as the weight function method are addressed.
Fatigue-Crack Propagation Through a Measured Residual Stress Field in Alloy Steel
Authors: Underwood JH , Pook LP , Sharples JK 
Published: March 2009

Fatigue crack-propagation tests were performed using 5 by 30 mm cross-section bend specimens of a nickel-chromium-molybdenum steel. The fatigue crack-propagation rate was determined from a group of stress-free specimens by measuring crack length on the specimen surfaces at intervals during cycling. Residual stress was produced in a second group of specimens by using a localized plastic deformation process. Resistance strain gages were first applied near one edge of each specimen along the line of intended crack growth. A series of 1-mm-deep plastic indentations was then made along the opposite edge of the specimen using a 25-mm-diameter pin. The strain gages provided a direct, accurate measure of the elastic, residual stress produced on one side of the specimen due to the local plastic deformation on the opposite side.
Measured crack-propagation rates in the specimens with residual stress are compared with rates in residual stress-free specimens. Crack-propagation rates are lower, as expected, near the edge of the specimen where the initial residual stress is compressive. Propagation rates remain lower even as the crack grows deeper into the specimen where the initial residual stress is tensile, which is not what would be expected from a simple superposition of stresses. However, an analysis involving the combination of the applied stress-intensity factor with that estimated from a redistribution of the residual stress in the specimens can account for the lower crack-propagation rates.
High Temperature Strain Behavior of Zircaloy-4 and Zr-2.5Nb Fuel Sheaths
Authors: Hunt CEL , Foote DE 
Published: March 2009

The ballooning behavior of Zircaloy-4 fuel sheaths at high temperatures has been reported previously by Hardy. Similar tests have been done on Zr-2.5Nb tubes. In both materials, the importance of the phase transformation from hexagonal close-packed to body-centered-cubic structure is evident. Towards the upper boundary of the two-phase (α + β) region where β-phase material would dominate, there is a marked discontinuity in the strain versus temperature results. They indicate that the solid solution strengthening in the β-phase is more effective than the second phase particle strengthening in the α-phase.
At normal operating temperatures, Zr-2.5Nb is stronger than Zircaloy-4. However, above 600°C it enters the two-phase temperature region and becomes weaker than Zircaloy-4 which is still within the α-phase. In the β-phase, where Zr-2.5Nb contains about twice as many atoms in solid solution as Zircaloy-4, the former again becomes stronger. At 1000°C, the strain rate of Zr-2.5Nb is about two orders of magnitude less than that of Zircaloy-4 at the same stress.