bluuebunny/crossref_metadata_2025_split huggingface dataset:
Elastic Torsional Buckling of Thin-Walled Composite Cylinders
Authors: Marlowe DE , Sushinsky GF , Dexter HB 
Published: March 2009

The elastic torsional buckling strength has been determined experimentally for thin-walled cylinders fabricated with glass/epoxy, boron/epoxy, and graphite/epoxy composite materials and composite-reinforced aluminum and titanium. Cylinders have been tested with several unidirectional-ply orientations and several cross-ply layups. Specimens were designed with diameter-to-thickness (D/t) ratios of approximately 150 and 300 and in two lengths (L), 10 in. (25.4 cm) and 20 in. (50.8 cm).
The results of these tests were compared with the buckling strengths predicted by the torsional buckling analysis of Chao. In this analysis, the instability loads of heterogeneous anisotropic cylinders are calculated with Timoshenko's equilibrium equations. The computer program associated with the analysis seeks the solution with the lowest buckling strength by iterating on the number of circumferential buckling waves. For the cylinders considered (L/r = 3.3 and L/r = 6.1), the experimental buckling torques were approximately 85 percent of the torques predicted by the Chao analysis. In the cross-ply laminate cylinders, the stacking sequence of the plies was found to have a marked effect on the elastic buckling torque.
Reversal of the stacking sequence of the cross-plied cylinders resulted in buckling torques which differed by a factor of 2. Similar results were obtained by reversal of the direction of twist on the original stacking sequence. This observation may be important in applications where reversal of loading can occur. The size effect of linear scaling was investigated for cylinders whose dimensions were different but whose L/r and D/t ratios were the same. As expected from the analysis, the experimental buckling stress remained constant.
A Correlation Study of Finite-Element Modeling for Vibrations of Composite Material Panels
Authors: Thornton EA , Clary RR 
Published: March 2009

A correlation study has been made to evaluate the effectiveness of finite-element modeling for vibrations of composite material panels. The three types of composite material panels studied were: (1) Symmetrically laminated cross-ply panels, (2) unsymmetrically laminated cross-ply panels, and (3) a 1/6-scale sandwich wing model. Correlations of finite-element predictions for frequencies and vibration modes were made with Rayleigh-Ritz analyses and experimental data.
For the symmetrically laminated panels the finite-element representation predicted vibration modes very accurately. For the unsymmetrically laminated panels it was found that predictions using uncoupled finite-element plate bending elements did not give good agreement with experimental data. The constant-chord, swept-wing model was effectively analyzed by finite-element presentations using either sandwich elements or ribs and spars.
Low-Weight, Impact-Resistant Helicopter Drive Shafts
Authors: Figge IE , Henshaw J , Roy PA , Olster EF 
Published: March 2009

The advantages and disadvantages of all composite helicopter drive shafts are discussed. Previous research has shown that all graphite/epoxy torque tubes severely delaminate under low-velocity, low-energy impact tests simulating accidental “tool drop” conditions.
In response to the need for weight savings without the sensitivity to low-energy impact, two composite metal hybird drive shafts have been designed and tested. These are constructed with unidirectional (parallel to the tube axis) boron epoxy composite, for increasing the flexural stiffness, sheathed with an inner and outer metal tube, for torsional strength and damage resistance.
A limited number of ballistic and low-energy impact tests were conducted. Damage from a 12 ft-lb simulated “tool drop” test was minimal. The same tube while sustaining 1/3 of its undamaged design torque was perforated by a fully tumbled 30-caliber projectile and subsequently failed at 2/3 of its undamaged ultimate load.
The hybird drive shaft is considered to have a significant weight savings potential. As compared to an all-aluminum drive shaft, its specific flexural stiffness is increased by a factor of 2.6 and its specific critical buckling stress by a factor of 1.5. As compared to an all-boron epoxy drive shaft, its specific flexural stiffness is approximately equal and the critical buckling stress is reduced by 40 percent. In addition to the advantage of impact resistance, the hybrid designs offers the advantage of metal-to-metal attachment with conventional splicers and nuts and bolts.
Fracture Characteristics of Plain and Welded 3-In.-Thick Aluminum Alloy Plate at Various Temperatures
Authors: Nelson FG , Brownhill DJ 
Published: March 2009

The tensile, notch tensile, tear, and, in some cases, fracture-toughness properties (KQ and KIc, ksi √in.) have been evaluated for 3-in.-thick 5083-H321, 5086-H32, 6061-T651, and 7005-T6351 plain plate and gas metal arc (GMA) welds in 5083-H321 (5183 filler), 6061-T651 (4043 and 5356 fillers), and 7005-T6351 (5356 filler) with no subsequent thermal treatment. The tests were made in the longitudinal, long-transverse and short-transverse orientations for the plain plate and in the “cross-weld” orientation for the welded panels. The tests were made at room temperature and generally at −100 and −320°F.
The fracture indexes, that is, notch-yield ratio and unit-propagation energy values, rank the plate and welds. The KQ and KIc values have been developed for the 6061-T651 and 7005-T6351 plate.
For the relatively tough materials in this investigation, the notch-yield ratio versus KIc relationship was not useful in estimating KIc values. However, the unit-propagation energy values versus KIc relationship does appear to provide a satisfactory means of estimating KIc values. Estimates of KIc values for all the materials tested in this program have been made from this correlation.
Influence of Metallurgical Variables on the Performance of Zircaloy Fuel Sheathing
Authors: Hardy DG , Bain AS 
Published: March 2009

In 1969, analysis of fuel defects in the Douglas Point power reactor indicated that the power ramp defects tended to occur preferentially in fuel with high strength/low ductility sheathing. The sheathing specification for all CANada Deuterium Uranium (CANDU) reactor fuel was changed to a lower strength/higher ductility Zircaloy which was found to retain a greater proportion of its ductility after irradiation than the high strength/low ductility tubing. Subsequently, more detailed mechanical testing failed to substantiate the relationship between the mechanical properties and the defect behavior.
Experimental fuel irradiations were undertaken to investigate the ability of fuel with high ducitility sheathing to survive power ramps after undergoing significant burnup at low power. Defects occurred in the experimental fuel bundles regardless of the mechanical properties of the sheathing, even in bundles annealed after the low power soak, but before the power ramp. These defects are attributed to stress corrosion cracking at areas of localized stress, not tensile failure.
Brazing is used to attach appendages to the fuel sheaths. Defects have been found in the as-received material, but a majority of defects have occurred in the two braze heat affected zones near the element ends. Because nonbrazed bundles have experienced defects in similar locations, it appears the defect location is related primarily to end-flux peaking. The low overall defect rate in CANDU fuel (0.03 percent since 1972) shows that the brazing process is not affecting fuel performance adversely.
We conclude that the initial metallurgical properties of the tubing have little influence on the defect behavior of power ramped fuel; thus the limits on mechanical property requirements of the sheath have become less stringent. Good fuel management to limit maximum powers and power increases, and an interfacial layer (referred to as a CANLUB layer) between fuel and sheath have proved more effective in reducing defects.
Oxidation of Zirconium Alloys in Steam at 1000 to 1850°C
Authors: Urbanic VF 
Published: March 2009

Oxygen embrittlement of fuel sheathing resulting from high temperature oxidation in steam is a potential fuel failure mechanism during a loss-of-coolant accident (LOCA). In high temperature steam, zirconium alloys form an outer layer of zirconium oxide (ZrO2) and an inner layer of oxygen-stabilized α-Zr immediately below. The metal/steam reaction for Zr-2.5Nb in the temperature range 1000 to 1600°C was studied and compared with earlier results for Zircaloy-2 and Zircaloy-4.
Reaction kinetics and the rate of growth of the combined (ZrO2 + α-zirconium) layers were measured. The reaction rates for all three alloys were similar and obeyed parabolic rate laws. The reaction rates were consistently less than those given by the Baker and Just correlation for zirconium oxidation in steam. A discontinuity was observed in the temperature dependence of the rate of growth of the combined (ZrO2 + α-zirconium) layer, and this discontinuity was attributed to a change in the oxide crystal structure. The thickness ratio ZrO2/α-zirconium also varies with temperature.
A method for estimating oxidation temperature and time from metallography, based on these observations, is discussed.
Irradiation Response of the Ordered Phase Zr3Al
Authors: Causey AR , Fidleris V , Rosinger HE , Schulson EM , Urbanic VF 
Published: March 2009

The ordered face-centered cubic (fcc) zirconium-aluminum phase (Zr3Al, Ll2 type) is being evaluated as a future CANada Deuterium Uranium (CANDU) reactor pressure-tube material on the hypothesis that ordering may lead to a reduction in rates of atomic diffusion and dislocation climb, and, hence, to a reduction of in-reactor creep. Experiments have been performed to measure the effects of fast neutrons on the dimensional stability, tensile properties, and corrosion resistance, in addition to measuring the in-reactor creep rates of a Zr-8.6Al alloy.
Irradiation-induced dimensional changes (in the absence of an applied stress) occurred which differed significantly in nature from those of Zircaloy and Zr-2.5Nb. The changes appear to have been caused by a combination of growth and swelling and decrease with increasing temperature; the dimensional changes appear to level off at 0.3 percent after 2 × 1024 neutrons (n)/m2 at 600 K. The long-term creep resistance at 570 K, deduced from bent-beam stress relaxation, is expected to be better than that of Zr-2.5Nb provided that the dimensional change does in fact level off. The tensile strength and ductility are superior to those of Zr-2.5Nb, while the resistance to aqueous corrosion is as good, provided that the α-zirconium phase content is ⩽1 percent by volume.
Yield and Fracture of Biaxially Stressed Zircaloy-4 Cladding Tubes at Room Temperature and at 400°C
Authors: Dressler G , Matucha KH 
Published: March 2009

Zircaloy-4 cladding tubes differing in texture only (Materials I and II were loaded simultaneously by internal pressure and axial forces at different stress ratios, α = axial stress, σa, and tangential stress, σt. Each stress ratio a was kept constant during the whole test, that is, from the beginning of elastic deformation to the fracture of specimens.
At room temperature the axial and tangential strains ϵa and ϵt, respectively, were measured as a function of σa and σt respectively (α = constant). These stress-strain diagrams were used to determine the apparent Young's moduli and the yield loci. At 400°C the yield locus was measured for Material I. Furthermore, for each stress ratio, α, those stresses σa and σt were measured at which fracture occurred. These “fracture” loci were determined for both materials at room temperature and 400°C.
Although the uniaxial data (stress ratio α = ∞) were very similar for both materials, a marked difference in yield and fracture behavior at a α ≠ ∞ was observed. Therefore, the criteria valid for isotropic materials turned out to be unsuitable for a satisfactory description of the measured data and relations.
Fracture of Zircaloy Cladding by Interactions with Uranium-Dioxide Pellets in Water Reactor Fuel Rods
Authors: Smith E 
Published: March 2009

The paper summarizes the main features of a detailed theoretical study of Zircaloy cladding fracture that is caused by the growth of stress corrosion cracks which form near fuel pellet cracks as a consequence of a power increase after a sufficiently high burn up. It is shown that unless stress corrosion crack growth in irradiated Zircaloy is able to proceed at very low stress intensifications, fracture is unlikely when there are uniform friction effects at the fuel-cladding interface, when the interfacial friction coefficient is less than unity, when a symmetric distribution of fuel cracks exists, and when symmetric interfacial slippage occurs (that is, “uniform” conditions). Otherwise, the observed fuel rod failures must be due to departures from uniform conditions, and this investigation shows that a very high interfacial friction coefficient, and particularly fuel-cladding bonding, are means of providing sufficient stress intensification at a cladding crack tip to explain the occurrence of cladding fractures.
The results of the investigation focus attention on the necessity for reliable experimental data on the stress corrosion crack growth behavior of irradiated Zircaloy and for further investigations on the correlation between local fuel-cladding bonding and stress corrosion cracking.
Estimating the Total Number of Species in a Biological Community
Authors: Slocomb J , Dickson KL 
Published: March 2009

The lognormal distribution has figured prominently in the description of species-abundance relationships and in assessing effects of perturbation on aquatic ecosystems. Diatom communities, in particular, have been shown to conform relatively well to a normal law subsequent to grouping individuals on a logarithmic scale. Fitting of the distribution to sample data entails estimation of location and scale parameters. A more interesting and, indeed, ecologically important estimate that can be obtained is the total number of species in the community, S*. Unfortunately, estimates of S* are currently unsatisfactory since an estimator of the variance of S*, var (S*), is not available. Moreover, it is often the case that several different theoretical distributions are found to fit the same sample data equally well but provide discrepant estimates of S*. On this basis then, comparisons between different communities are impossible. In addition, a cautious attitude is warranted in certain applications of the Shannon-Wiener diversity index where knowledge of S* is required.
The purpose of this paper is to report on the results of a computer simulation study which was designed to mimic the sampling and identification of diatom species from idealized, fully censused collections where the value of S* was known as was the proportional abundance of each species. Each simulation run consisted of sampling the idealized collections a total of 100 (independent) times; each sample being fit by a lognormal distribution and an estimate of S* calculated. It was thus possible to compute an estimate of var (S~*) and monitor its behavior as the sample sizes for various types of communities were increased. The results indicate that the precision of S~* depends on the relative size of the sample and that var (S~*) decreases asymptotically as the number of species sampled approaches S*. It is shown that, for some types of communities, species sample sizes on the order of S = 0.8 (S*) yield imprecise estimates of S*. The implications of these results have importance for the biologist who is faced with distinguishing between two or more similarly diverse communities on the basis on an index of evenness such as H/Hmax (in the case of Shannon-Wiener). Unless reliable knowledge of S* can be obtained, misleading conclusions regarding a community's diversity could result.
Statistical Methods Applied to a Four-Year Multivariate Study of a Florida Estuarine System
Authors: Meeter DA , Livingston RJ 
Published: March 2009

A four-year study (1972 to 1976) was carried out to determine the long-term changes of organochlorine compound concentrations and of associations of epibenthic fishes and invertebrates in a river-dominated north Florida estuary.
We assessed the relative effectiveness of a number of statistical techniques for describing the effects of key physicochemical variables on the estuarine biota. Techniques used included transformations, correlation, regression with dummy variables, two and three-way analysis of variance, multivariate analysis of variance, principal components analysis, factor analysis, canonical correlation, and cluster analysis.
Several problems were encountered peculiar to studies of this type: missing observations, the sheer size of the data base in numbers of variables and observations, the domination of other effects by river flow, and extreme and noncyclical variation of some measures over the four-year study period.
In Situ Seismic Shear-Wave Velocity Measurements and Proposed Procedures
Authors: Statton CT , Auld B , Fritz A 
Published: March 2009

Determination of dynamic shear modulus in situ has been an increasingly important source of data for ground response analysis for earthquake design studies. Historically, shear modulus is calculated from in situ measurement of seismic shear-wave velocity. A downhole impact energy source has been developed which maximizes the shear-wave energy produced and minimizes compressional-wave energy for purposes of crosshole in situ seismic shear-wave velocity measurements. The geometry of the energy source permits reversal of the polarity of shear-wave arrivals without changing the polarity of compressional-wave arrivals.
The energy source is described and in situ measurement data are presented. Based on more than three years experience using the downhole source, a procedure for in situ measurement of seismic shear-wave velocity is suggested.
Logistic Requirements for Aerial Application of Oil Spill Dispersants
Authors: Ross CW , Hildebrand PB , Allen AA 
Published: March 2009

The study has taken a detailed look at selected components involved in establishing the feasibility of aerially applying dispersants on oil spills. The approach has purposely been focused onto only those areas affecting operational feasibility. Little attention has been given to other critical areas such as ecology, comparisons with alternative countermeasures, or even a detailed comparison with alternative dispersant platforms.
The study attempts to include a wide scope in that it has purposely been based on general assumptions and mathematical formulas and could be used to evaluate other spill configurations, volumes, locations, or even other dispersant platforms. The formulas are used to discuss a scenario to disperse the main oil slick resulting from a blowout. Many other scenarios, oil volumes, periods of operation, etc. could be evaluated using these equations.
Based on the developed scenario, the total cost to disperse 20 000 m3 of oil is in the neighborhood of $10.22 million or $511/m3. This figure consists of about $1.3 million for equipment rental and fuel and $8.85 million for dispersants. No allowance has been made for other costs such as manpower or ancillary logistics such as shelter, food, waste disposal, and development of airstrips.
Assessment Problems of Whether or Not to Treat Oil Spills
Authors: Wilson MP 
Published: March 2009

Any decision to treat or not to treat an oil spill with dispersants involves a multiplicity of biological, chemical, physical, and meteorological inputs. Knowledge concerning the fate of treated and untreated spills is a prerequisite for estimating environmental impacts. Biological data concerning acute toxicity levels and the inter-relationship of the affected marine biota must be understood and quantified, as well as the weathering of the oil, the modification of it by microorganisms, and the change in the chemical and physical nature of the oil spill by various types of dispersants.
Most of the information required to conduct such an assessment is not presently available and must be obtained from a series of laboratory, meso-scale, and in situ types of experiments. The type of information obtainable from each type of experiment is discussed and the role it plays in the assessment process is presented.
Oil Spill Control Chemicals—Oil Spill Control A Current View
Authors: Linblom GP 
Published: March 2009

Oil spill control chemicals are still a subject of considerable contention in many parts of the world. Because of the reactions raised by news of oil spills, their potential effects, and the methods used in their control and cleanup, a body of misinformation and misunderstanding about these chemicals and their use has accumulated. Further, there are honest differences of opinion between and among various manufacturers, regulatory agencies, environmental groups, and users.
This paper attempts to provide a basis for further discussion by examining the current status of oil spill chemicals under five categories: definition of terms, classification of products, the mode of action of various-type chemicals, potential ecotoxicity, and the application methods required to obtain optimum results.
The term “oil spill control chemical,” as used herein, includes dispersants, collecting agents, shoreline protection chemicals, and post-spill cleaners. Dispersants are further categorized depending on the solvent type used or on the recommended method of use. The concept of chemical dose per unit area is suggested as most realistic for development of application systems based on the mode of action of various chemicals, and for tests to determine their efficiency and toxicity. Boat and aerial dispersant spray systems are examined in detail to emphasize critical design criteria and to identify limitations.
Ecological Effects of Dispersants in the United Kingdom
Authors: Cowell EB 
Published: March 2009

The problems associated with the toxicity of dispersants at the time of the Torrey Canyon disaster are described together with subsequent developments to reduce toxicity. The problems of laboratory bioassay and its limitations in ecological prediction are reviewed in relation to dispersant concentrations that are reached under field use.
Problems of the use and ecological effects of dispersants in shore cleaning are described in association with practical aspects of safe application and limitations. The author concludes that modern dispersant formulations can be used with minimum ecological risk provided the application is done with care by trained operators. It is stressed that even the most recently developed materials should not be used on areas of vascular plants such as salt marshes and mangroves. The lack of adequate research precludes recommending dispersants to treat oil spillage in freshwater rivers and lakes unless the bodies of water are extremely large.
Fibrous Insulating Materials as Standard Reference Materials at Low Temperatures
Authors: Bertasi M , Bigolaro G , De Ponte F 
Published: March 2009

A model is proposed to describe the thermal behavior of relatively high-density fibrous materials. The theoretical approach is compared with experimental results on glass fiber insulating specimens. The results point out the limits of other oversimplified models and the excessive complexity of other models with respect to the precision of results. The agreement between experimental and computed data was considered satisfactory when near to 1 percent.
The theoretical model may be used for computing some limits to obtain reliable standard reference materials with regard to production variations.
The problem of the influence of moisture on measured data is then analyzed, starting from a large set of experimental data obtained on specimens in controlled atmospheres.