bluuebunny/crossref_metadata_2025 huggingface dataset:
Using NDT Aided by an Expert System to Evaluate Airport and Highway Systems
Authors: Greenstein J , Berger L
Published: December 2008

The paper presents the methodology currently used by the authors for the evaluation of flexible and rigid airport and highway pavements. Using this methodology, one can determine economically and accurately the elastic modulus of: (a) the subgrade; (b) the subbase and base materials, and (c) the asphalt layer of a flexible pavement. To improve the accuracy and to reduce the sensitivity of the calculated moduli of old pavements with nonuniform characteristics, the subgrade modulus is calculated, and then the combined modulus of the pavement structure is completed. In the third step the moduli of the asphalt and granular materials are determined. The alternative way of calculating the three moduli exactly and simultaneously is sensitive to minor changes in pavement performance in terms of either deflection basin or layer thicknesses. The Hogg model of a thin plate on an elastic foundation, the Burmister two-layer model, the Odemark-Ullidtz method of “equivalent thicknesses,” and the theory of strength of materials are all used to calculate the elastic moduli of the subgrade and pavement layers. Comparison of the elastic moduli determined by the simplified methods and such “exact” computer programs as CRANLAY showed very good agreement. The Hertz-Westergaard models are used in the evaluation of rigid pavement. An expert system in airport and highway pavement evaluation projects is used to minimize the testing errors and to better calibrate the nondestructive testing (NDT) results with standard test pits. The NDT methodology presented in this paper is independent of equipment type and has been successfully used with the Pavement Profiler, the falling weight deflectometer, the 16-kip vibrator, and the Benkelman beam. This NDT methodology has been used worldwide as: (a) a design tool of pavement strengthening and rehabilitation, and (b) a quality control tool to analyze and predict the performance of adequate and marginal materials that do not meet standard specifications.
Numerical and Optimization Techniques Applied to Surface Waves for Backcalculation of Layer Moduli
Authors: Hossain MM , Drnevich VP
Published: December 2008

This paper eontains two methods of determining the pavement moduli and thicknesses using a computer prograrri written in FORTRAN 77. The first method, a simple finite difference technique, is developed for the analysis of generalized Rayleigh waves in multilayered elastic media. The method, which leads to an eigenvalue problem, is very effective in determining theoretical dispersion curves for pavement systems modeled as layered composite plates with free surfaces at both top and bottom or free surface of the top and rigid base at the bottom. Backcalculation of moduli and thicknesses is done by an optimization routine developed by Powell [1] based on least squares criterion.

The second method determines a theoretical dispersion curve based on Knopoff s technique [2]. Since phase velocities of the waves observed experimentally on pavement structures are complex, suitable modification of Knopoff's algorithm for the geologic model has been made by the authors to account for this effect. For optimization, the same technique is used as mentioned above.

Numerical results obtained in the two cases show excellent agreement with previously published solutions obtained by other theories.
Overview of Coating Materials, Surface Treatments, and Screening Techniques for Tribological Applications—Part 1: Coating Materials and Surface Treatments
Authors: Bhushan B
Published: December 2008

This paper reviews the commonly used coating materials and surface treatments for tribological applications. The coating materials considered are plastics, such as polytetrafluoroethylene, polyamide-imide, polyphenylene sulfide, and polyimide; molybdenum disulfide; graphite; cadmium oxide-graphite-silver; calcium fluoride-silver-glass-nickel-chrome; hard chrome; electroless nickel; silver; and some selected carbides, nitrides, borides, and oxides. Surface treatments considered are carburizing, nitriding, carbonitriding, boriding, induction hardening, flame hardening, and laser hardening. Some examples of industrial applications are presented.
Ring Shear Testing of Deposited Coatings
Authors: Dini JW , Kelley WK , Johnson HR
Published: December 2008

This paper discusses ring shear tests for quantitatively measuring the adhesion between metal coatings and their substrates. Details are presented on the testing procedure and the various substrate-coating combinations that have been evaluated by this method. A number of applications are also included wherein ring shear tests have been used to define optimum cleaning/activating procedures for substrates such as 6061 aluminum, beryllium, and 304 and 440C stainless steel.
Soil Reinforcement Design Using Geotextiles and Geogrids
Authors: Bonaparte R , Holtz RD , Giroud JP
Published: December 2008

This paper provides an overview of the design of soil structures reinforced with polymeric materials. Applications for soil reinforcement are reviewed and categorized according to the type of soil structure, type of load, and function and location of reinforcement. Approaches to design are reviewed, and it is shown that most current design procedures are based on simple extensions of classical limit equilibrium analyses.

Properties of polymeric reinforcement relevant to design are presented. They are subdivided into tensile properties and soil-reinforcement interaction properties. Use of wide-strip, constant-load creep tests are recommended for evaluation of tensile properties for design of permanent soil structures. Soil-reinforcement interaction characteristics are evaluated in terms of direct sliding of soil over reinforcement and pullout of reinforcement from soil. Direct sliding characteristics should be evaluated using the direct shear test. Pullout characteristics for geotextiles can be approximated from direct shear test results; however, pullout characteristics for geogrids must be evaluated using pullout tests.

The paper concludes with a detailed presentation of simple limit equilibrium design analyses for three of the most commonly encountered types of reinforced soil structures: reinforced slopes, reinforced soil walls, and reinforced embankments over weak foundations. Specific recommendations are made on determination of reinforcement properties for design of these three types of structures.
A Process for Solidifying Sodium Nitrate Waste in Polyethylene
Authors: Heiser JH , Franz E-M , Colombo P
Published: December 2008

A laboratory-scale process has been developed for the solidification of nitrate salt wastes in polyethylene. The process uses a commercially available single-screw extruder which continuously discharges prescribed polyethylene-waste mixtures from the hoppers to the output die, where it is extruded into a container while still in the molten form. The molten mixture (̃110 to 120°C) conforms to the shape of the container and solidifies upon cooling. Proportional feeders maintain waste-to-binder ratio and homogeneity of the waste form. Present studies use dry wastes, although wet solid wastes can be processed using vented extruders of the type used for the bitumen solidification process.

Tests were performed to determine leachability and mechanical stability. Emphasis is placed upon leaching of nitrates from the waste forms. Leach tests were performed according to ANS 16.1 as well as the EPA extraction procedure (EP). For polyethylene waste forms containing 30 to 70 weight percent sodium nitrate, ANS 16.1 leach indices range from 11 to 7.8, respectively. Compressive yield strengths range from 18 to 5 MPa (after 90 days' water immersion). The results of the EP indicate that the nitrate release levels for waste forms containing as much as 70 weight % sodium nitrate are not defined as characteristically hazardous waste.

Differential scanning calorimetry (DSC) was used to confirm the compatability of polyethylene and simulated salt wastes at elevated temperatures. Components of the polyethylene/sodium nitrate system, alone and in combination, were tested by DSC at temperatures to 400°C. At these temperatures, no chemical interactions were observed between polyethylene and nitrate waste compositions.
Evaluating the Freeze-Thaw Durability of Portland Cement-Stabilized-Solidified Heavy Metal Waste Using Acoustic Measurements
Authors: El-Korchi T , Gress D , Baldwin K , Bishop P
Published: December 2008

The use of stress wave propagation to assess freeze-thaw resistance of portland cement solidified /stabilized waste is presented. The stress wave technique is sensitive to the internal structure of the specimens and would detect structural deterioration independent of weight loss or visual observations.

The freeze-thaw resistance of a cement-solidified cadmium waste and a control was evaluated. The control and cadmium wastes both showed poor freeze-thaw resistance. However, the addition of cadmium and seawater curing increased the resistance to more cycles of freezing and thawing. This is attributed to microstructural changes.
A Physical Testing Program for Stabilized Metal Hydroxide Sludges
Authors: Forslund BL , Smith LJS , Bergstrom WR
Published: December 2008

A proposed method of closing two Resource Conservation and Recovery Act surface impoundments containing metal hydroxide (F006) sludges involved stabilization and on-site disposal. A sample testing program was developed as part of an evaluation of processes offered by various firms interested in performing the stabilization. For this application, the stabilized material was to have sufficient strength to support construction and cover loads, low permeability, long-term durability, and low settlement under anticipated loads.

The test procedures developed to determine those properties were based on standard soil and soil-cement test methods to the extent possible. The standard test methods proposed for use included the ASTM Test Methods for Unconfined Compressive Strength of Cohesive Soil (D 2166), for One-Dimensional Consolidation Properties of Soils (D 2435), Wetting-and-Drying Tests of Compacted Soil/Cement Mixtures (D 559), and Freezing-and-Thawing Tests of Compacted Soil/Cement Mixtures (D 560). A falling-head test was used to determine the coefficient of permeability. Appropriate molds and specimen preparation procedures were sent to each firm with a sample of the raw sludge in order that the stabilized sludge specimens would be prepared in the same manner.

Modifications to the proposed test procedures were required due to the condition of several sets of samples. The procedures for evaluating the freeze-thaw and wet-dry durability were altered by eliminating the brushing and weighing of samples between cycles. This sample handling was eliminated so that the relative effects of environmental exposure could be more readily compared. A few of the samples suffered significant expansion, shrinkage, cracking or some combination of these to a degree that made them unusable.

In general, the specimen preparation procedures and test methods developed worked well for the stabilized sludge samples. The unconfined compressive strength test results were highly variable and ranged from 0.5 kg/cm2 (100 lb/ft2) to over 35 kg/cm2 (70 000 lb/ft2). The compressibility under a load of 1.5 kg/cm2 (3000 lb/ft2) ranged from 0.5% to 5%. The permeability of the stabilized material was generally low and in the range of 10-6 to 10-7 cm/s. The specimens generally withstood more freeze/thaw cycles than wet/dry cycles; several of the specimens lost much of their strength and integrity upon saturation. No strong correlation between any of the physical properties was observed. However, specimens which included cement as an additive tended to fail at low strain, have higher unconfined compressive strength, and were less compressible.
Column Leach Testing of Phenol and Trichloroethylene Stabilized/Solidified with Portland Cement
Authors: Kolvites B , Bishop P
Published: December 2008

The ability of portland cement to stabilize/solidify organic wastes was evaluated by conducting column leaching tests on portland cement pastes containing phenol and trich loroethylene (TCE). Synthetic solidified waste was manufactured by mixing dilute aqueous solutions of phenol and TCE with Portland Type II cement at a 0.5 liquid-to-cement ratio. The liquid consisted of either 4000 mg/L phenol or 1100 mg/L TCE in purified water. The cement was cured for 3 days and 28 days at 100% humidity at room temperature. Thirty grams of particles approximately 5 to 10 mm in diameter were placed in an enclosed leaching ap paratus. Purified water was pumped upward through the column at a rate of 0.08 to 0.18 mL/ min. Every 48 h for eight days, samples of the leachate in the collection flask and samples of the vapor in the head spaces above the collection flask and leaching column were analyzed by gas chromatography. The concentrations of phenol and TCE found in these samples were used to calculate the total mass of the organic compound which was released from the solidified waste during eight days of leaching.

An empirical mathematical model was used to predict the long-term leaching characteristics of the stabilized phenol waste. The leachability indexes calculated for phenol in cement paste cured 3 days and 28 days were 7.7 and 8.2, respectively. This index rates the relative mobility of the contaminant on a uniform scale that varies from 5 (very mobile) to 15 (immobile). Similar leachability indexes could not be calculated for cement paste containing TCE due to unquantified losses of TCE by volatilization prior to the start of the leach tests and suspected decomposition of TCE in the highly alkaline environment. Gas chromatograms of the TCE waste leachates contained unidentified peaks which were thought to represent the products of TCE decomposition.
A Study of Tritium Release from Encapsulated Titanium Tritide Accelerator Targets
Authors: Landolt RR , Bauer LR
Published: December 2008

Titanium tritide accelerator targets were encapsulated in several types of waste-disposal solidification media. The resulting monoliths were subjected to a standard leach testing procedure. A bare tritium target was also immersed in water and evaluated for tritium release. As anticipated, more tritium was released from the bare target than from the encapsulated targets, but not by a large factor. Of the encapsulating media tested, gypsum cement, coated and uncoated, performed slightly better than epoxy or microsilica cement. A gypsum cement-encapsulated target was also tested in air, and its tritium release was compared with that of the gypsum cement-encapsulated target which had been subjected to the leach test. Significantly more tritium was released from the specimen suspended in air. The results indicate that tritium can move through these barrier materials and may be released from an encapsulated target exposed to water or to air.
Solubility and Stability of Inorganic Iodides: Candidate Waste Forms for Iodine-129
Authors: Taylor P , Lopata VJ , Wood DD , Yacyshyn H
Published: December 2008

Iodine-129 and carbon-14 are of lesser importance than many other radionuclides in nuclear waste management because of their relatively low radiotoxicity. Their safe immobilization and disposal, however, is a significant challenge because their chemical properties are quite different from most other components of nuclear fuel waste. The authors have sought thermodynamically defensible inorganic waste forms for both of these radioisotopes.

This paper discusses the stability and solubility of inorganic iodides as they relate to the selection of a waste form for iodine-129. The best candidates appear to be silver iodide (AgI), either alone or in combination with silver chloride (AgCl), and a combination of Bi5O7I and Bi2O3. Neither is completely satisfactory. The principal drawback of AgI is its relative ease of reduction. High chloride concentrations also increase the solubility of Agl, but it is insensitive to carbonate. The main disadvantage of bismuth oxyiodide is its susceptibility to displacement reactions with dissolved chloride and carbonate; also, it is unstable under strongly reducing conditions.
Stabilization of Mixed Waste at the Idaho National Engineering Laboratory
Authors: Boehmer AM , Gillins RL , Larsen MM
Published: December 2008

EG&G Idaho, Inc. has initiated a program to develop safe, efficient, cost-effective treatment methods for the stabilization of some of the hazardous and mixed wastes generated at the Idaho National Engineering Laboratory. Laboratory-scale testing has shown that Extraction Procedure toxic wastes can be successfully stabilized by solidification, using various binders to produce nontoxic, stable waste forms for safe, long-term disposal as either landfill waste or low-level radioactive waste, depending upon the radioactivity content.

This paper presents the results of drum-scale solidification testing conducted on hazardous, low-level incinerator fly ash generated at the Waste Experimental Reduction Facility. The drum-scale test program was conducted to verify that laboratory-scale results could be successfully adapted into a production operation.
Spray Droplet Size Effect on Mortality of Citrus Rust Mite
Authors: Salyani M , McCoy CW
Published: December 2008

A laboratory study was conducted to determine the effect of spray droplet size and distribution on control of citrus rust mite under moist and dry post-treatment conditions. Using a droplet generator, different droplet sizes of AGRI-MEK EC (abomectin) were sprayed toward pairs of targets (mite infested Valencia oranges and water sensitive papers). The length mean diameters of spray droplets ranged from 43.9 to 693.1 μm. One half of the treated fruit received a daily spray mist of distilled water to simulate dew condition in the field; the other half were maintained in dry condition. On each fruit adult mites were counted at 3 locations representive of full coverage, partial, and no coverage. Counts were made prior to spraying and at 1, 2, and 6 days post-treatment. All acaricide treatments reduced mite populations significantly compared to untreated checks. Small droplets gave higher mite mortality than larger droplets. Mite mortality increased by wetting fruit. There were uniform coverages for small and medium size droplets and random-clustered distributions for large droplets.
Computerized Infrared: The Need for Caution
Authors: Hirschfeld T
Published: December 2008

So much can be done in infrared (IR) spectroscopy with computers that we are beginning to lose the healthy paranoia that should accompany their use. Even when we are careful, our precautions are quite unequal to the sophisticated and unobvious errors computers can generate. Even such apparently unobjectionable statements as “this algorithm should only be used by experts” often can be translated upon reflection to “since the program will track your prejudices, you better start with the right ones.” Searching algorithms, trial and error optimizations, multilinear regressions, and factor analysis all have higher order failure modes that are briefly reviewed. Computer simulation requires far more brute force in its application than we normally employ. And the very severe problem of flow frequency bugs can be approached only by redundant algorithmic pathways.
Injury of the Anterior Cruciate Ligament of the Knee in Downhill Skiing: Its Pathomechanism and Treatment
Authors: Shino K , Horibe S , Nagano J , Ono K
Published: December 2008

We reviewed 26 skiers who underwent a repair or reconstruction of the anterior cruciate ligament because of tears of the ligament to study how the ligaments were torn in downhill skiing and how the lesion should be treated. It was pointed out that isolated tear of the ligament was more common than a tear combined with medial collateral ligament injuries and that vigorous contraction of the nearby quadriceps femoris muscle during extension was a major cause of injury to the ligament. For maximum recovery, early corrective surgical treatment seemed to be essential.
Epidemiology of Eye Injuries in Hockey
Authors: Pashby T
Published: December 2008

Collection of hockey eye injury data revealed an alarming number of severe eye injuries suffered by Canadian players. In two hockey seasons, 63 blinding eye injuries were recorded. Rule changes and the development of Canadian Standards Association-certified eye protectors has eliminated the injury problem. When all hockey players wear certified protectors, the eye injury problem will be solved.
Rule Changes: Their Effect on Safety in Ice Hockey
Authors: Rudolph M
Published: December 2008

This paper discusses the procedures used by the Amateur Hockey Association of the United States (AHAUS) for developing changes and for dealing with proposals for changes in the official playing rules sponsored by AHAUS for amateur ice hockey in the United States. The development of the rule requiring face guards is described as an illustration of the process.
The Effect of Rules and Officiating on the Occurrence and Prevention of Injuries
Authors: Parayre R
Published: December 2008

From past and present experiences in Canadian hockey, there seems to be a definite link between the rules of the game and their application (or lack thereof) and the potential for injuries of any type as a result of playing the sport.

Most people feel, rightly or wrongly, that the focal point of our sport with regard to injury incidence and prevention is officiating. The major roadblock which has confronted various hockey constituents, and which is still very much present to this day, is a variety of attitudes towards the way a game should be played. For the official as well as for the administrator, the task often becomes difficult, as they both have to deal with a wide gamut of attitudes towards the sport and try to maintain order and harmony among players, coaches, team and league executives, fans, the media, and the general public.

Clear progress was evident with the advent of facial protection. However, it seems that this positive step has brought on a false sense of security on the players' part and a permissive attitude on the part of officials (among others). The ensuing spinal injuries have recently forced the Canadian Amateur Hockey Association (CAHA) to toughen up rules on checking from behind and to initiate a national movement to cut down on stick infractions. At the present time, we seem to be going in the right direction. The key to success, the CAHA has found, is public awareness and education. Specifically, it recognizes the necessity for the officials to enforce the rules as intended, thereby putting the onus on the coaches, the players, and several other game constituents to adjust their attitudes and habits accordingly.
Performance of a Thin-Surfaced, Crushed-Stone Base Pavement
Authors: Barksdale RD , Greene RL , Bush AJ , Machemehl CA
Published: December 2008

An experimental pavement approximately 200 m (650 ft) long was constructed in May of 1978 consisting of a 19-mm (0.75-in.) triple surface treatment over a 460-mm (18 in.) crushed-stone base. By 1985 the pavement had been subjected to about 1.4 million equivalent 80 kN (18 kip) American Association of State Highway and Transportation Officials (AASHTO) single-axle loads neglecting front axle effects. The straight segment of the pavement had a present serviceability rating of 3.0 to 3.5 in 1985. About 6.5% surface cracking had developed mostly within the last two years (1984 to 1985). The pavement is constructed on a clayey and sandy silt subgrade which is relatively dry and has a field California bearing ratio (CBR) of 10. The crushed stone base is well graded, has a maximum aggregate size of 30 mm (1.5 in.), and contains less than 2.0% fines. Field tests performed on the pavement included static plate load tests, Benkelman beam, surface strain measurements, and falling weight deflectometer (FWD) tests.

Using the AASHTO design method, a base course layer coefficient for the upper 305 mm (12 in.) was backcalculated to be 0.18, and 0.16 for the remaining stone base. The elastic modulus of the base was backfigured from the FWD test results to be 406 MN/m2 (59 ksi) using the Waterways Experiment Station (WES) approach; other methods of backcalculation gave widely varying results. The elastic moduli of the base and subgrade depend upon the test method and also the mean stress and shearing strain to which the material is subjected. Because of the difference in loading conditions, the elastic modulus of the base will be somewhat lower under a dual-wheel, 80-kN (18-kip) axle loading than under the single, 40-kN (9-kip) FWD test loading.
Prediction of Permanent Deformation in Flexible Pavement Materials
Authors: Tseng K-H , Lytton RL
Published: December 2008

This paper presents a method to predict the permanent deformation (rutting) in pavements using a mechanistic-empirical model of material characterization. Three permanent deformation parameters are developed through material testing to simply represent the curved relationship between permanent strains and the number of load cycles. Equations are developed by regression analysis which determine how these three parameters are affected by the material properties, environmental conditions (moisture and temperature), and stress state. These relations are important in calculating the permanent deformation of pavement layers since the relation between permanent deformation and cycles of load from the laboratory is usually examined in test conditions that are significantly different from field conditions. The permanent deformations calculated from the method presented are compared with results measured in the field in Florida and are found to be accurate.

The permanent deformation is calculated as the sum of the resilient strains multiplied by the fractional increase of total strains for each material layer of the pavement. The resilient strains of pavement structures under highway loadings are calculated using a finite-element analysis which incorporates both linear and nonlinear stress-strain behavior of the pavement component materials. The fractional increase of total strains is basically in terms of three parameters which characterize the permanent deformation relations from the laboratory. The values of these parameters are developed for pavement materials such as asphalt concrete, gravel and crushed-stone base course materials, and subgrade soils from a variety of data sources. The statistical equations for the three parameters are developed for each type of material represented in the data. The most important terms in the equations are the asphalt content, temperature, resilient modulus, and stress state for asphalt concrete material, and the water content, resilient modulus, and stress state for base and subgrade soils, respectively. These equations and the method as mentioned above has been programmed into a modified ILLI-PAVE program to calculate the resilient strains and permanent deformation in each layer of pavement, taking into account realistic distributions of tire contact pressures, both vertical and horizontal.

The permanent deformation obtained is shown to be in reasonable agreement with the measured results. It is demonstrated that this method provides an appropriate and realistic analysis of prediction of the permanent deformation, and further, the results are used in the prediction of the loss of serviceability index of pavements using the American Association of State Highway and Transportation Officials (AASHTO) Road Test relation. The paper demonstrates the importance of accurate materials characterization in predicting the rutting of asphalt concrete pavements on granular base course.
Resin Impregnation During the Manufacture of Thermoplastic Matrix Composite Materials
Authors: Coulter JP , Güçeri SI
Published: December 2008

A numerical investigation was performed into the resin flow that occurs during the manufacture of thermoplastic matrix composite materials. Specific attention was directed towards modeling the fiber/matrix consolidation that occurs during resin film stacking/compression molding processes. The understanding of these processes is important to the field of composite materials because it is desirable to know the proper processing conditions to apply during manufacturing to obtain completely consolidated, void-free thermoplastic resin composite parts.

The numerical study was based on the assumption of two-dimensional Darcy flow through stationary porous media. Fiber motion was neglected and quasi-steady state flow conditions were assumed. Inhomogeneity and anisotropy of fibrous preforms were allowed for. Due to the degree of geometrical complexity inherent to impregnation processes, the computational technique of boundary-fitted coordinate systems encompassing numerical grid generation was used and was found to be suitable for solving flow problems involving moving boundaries. The boundary conditions chosen for the investigation include constant applied pressure at the inlet, no-slip flow conditions along all walls, and vanishing shear stress along the impregnation front. Resin front/mold wall contact point movement was accomplished using either a no-slip based relocation algorithm or an imposed orthogonality method.

Results are presented in the forms of temporal impregnation front positions and neat resin depth distributions for two sample process configurations. From the analysis of this information, processing parameters are suggested with which the successful manufacturing of thermoplastic composite materials can be accomplished. The need for further experimental and analytical work in this area is also discussed.
Interlaminar Fracture Toughness of Thermoplastic Composites
Authors: Hinkley JA , Johnston NJ , O'Brien TK
Published: December 2008

Edge delamination tension (EDT) and double cantilever beam (DCB) tests were used to characterize the interlaminar fracture toughness of continuous graphite-fiber composites made from experimental thermoplastic polyimides and a model thermoplastic. Residual thermal stresses, known to be significant in materials processed at high temperatures, were included in the edge delamination calculations. In the model thermoplastic system (polycarbonate matrix), surface properties of the graphite fiber were shown to be significant. Critical strain energy release rates for two different fibers having similar nominal tensile properties differed by 30 to 60%. The reason for the difference is not clear. Interlaminar toughness values for the thermoplastic poly-imide composites (LARC-TPI and polyimidesulfone) were 400 to 700 J/m2. Scanning electron micrographs of the EDT fracture surfaces suggest poor fiber/matrix bonding. Residual thermal stresses account for up to 32% of the strain energy release in composites made from these high-temperature resins.
Assessment of Squirrel-Caused Power Outages
Authors: Hamilton JC , Johnson RJ , Case RM , Riley MW
Published: December 2008

Squirrel-caused power outages in Lincoln and Omaha, Nebraska, were evaluated by examining company power outage reports and by consulting with power company representatives. Reports showed that squirrel-caused outages at pole-mounted transformers were most prevalent during May, June, and October (48% of total) and between 1 and 4 h after sunrise (38%), patterns that coincide with squirrel dispersal or morning activity periods. In Lincoln, 1980 and 1981, squirrels caused 177 outages per year, which was 24% of all outages and 90% of animal-caused outages. Estimated minimum annual costs were $23 364 for repairs, public relations, and lost revenue while meters were not running. In Omaha, 1985 and 1986, squirrels caused 332 outages per year, costing at least $47 144 annually. Squirrel-caused outages at substations cost an additional $400 (Lincoln) to $810 (Omaha) annually. Between 1982 and 1985, squirrel guards were installed on all 13 000 Lincoln transformers at an estimated minimum cost of $20 per guard, or $260 000 total. Records from Lincoln after all guards were installed (1986 and 1987) indicate that annual costs were reduced 78% to $5148. Life expectancy of the guards is unknown. The extent of squirrel-caused outages and associated costs may vary among cities and regions. Assessment of these outages as described here can be used for timing biological studies and as a procedural structure for making similar economic assessments in other areas.
SEM Fractography of Pure and Mixed-Mode Interlaminar Fractures in Graphite/Epoxy Composites
Authors: Arcan L , Arcan M , Daniel IM
Published: December 2008

The objective of this study was to characterize the morphology of interlaminar fractures in unidirectional graphite/epoxy composites. The specific objective was to correlate characteristic fractographic patterns for different pure and mixedmode loadings with the loading parameters and fracture mechanisms. Two graphite/epoxy composite materials were investigated, one with a brittle matrix and the other with a rubber-toughened matrix. The tests were conducted with a specially designed loading system which allows the application of pure Mode I or Mode II loadings or any combination thereof. SEM fractographs, including stereo pairs, were taken of the specimens after failure at various points across the width of the crack and at various distances from the initial crack front. In the case of the brittle matrix composite, the fibers are, in general, covered with a film of matrix. The matrix fracture surface consists of hackles resulting from interfacial tensile or shear failure and tensile failure normal to the maximum tensile stress. The hackle density increases from Mode I, to Mode II, to mixed Mode I and II. In the case of the toughened matrix composite, the fibers are covered with matrix for Mode I and mixed Mode I and II fractures, whereas they are clean under Mode II and mixed Mode II with compression loading. Matrix fracture is granular or consists of hackles with a low degree of orientation and regularity increasing from Mode I to Mode II. Failure mechanisms include interfacial shear and high ductile or plastic elongation of the matrix.
Correlations Between Micromechanical Failure Processes and the Delamination Toughness of Graphite/Epoxy Systems
Authors: Hibbs MF , Bradley WL
Published: December 2008

A combination of macroscopic delamination fracture toughness, scanning electron microscope (SEM) real-time fracture observations, and postfracture morphology were used to study the micromechanical processes of delamination failure in several graphite/epoxy systems.

Strain energy release rate GIc, GIIc, and mixed mode GI&IIc were obtained from unidirectional double cantilever beam specimens. Comparisons of these energy release rates with the resulting fracture surface mophology are used to clarify the relative importance of the formation of hackles and the fiber matrix interface adhesion to delamination toughness under Mode I, Mode II, and mixed Mode I & II loading conditions.

Real-time fracture observations of composite delamination in the SEM revealed the microprocesses of microcrack formation and coalescence. These observations coupled with GIc for the neat material, determined from compact tension specimens, provide insight on how resin toughness can be translated into composite delamination toughness.

The implications of hackle formation and their importance in the failure analysis of graphite/epoxy systems are discussed.
A Fractographic Investigation of the Influence of Stacking Sequence on the Strength of Notched Laminated Composites
Authors: Harris CE , Morris DH
Published: December 2008

A study of the fracture processes in T300/5208 notched laminated composites concentrated on characterizing the influences of laminate stacking sequence on the formation of notch-tip damage zones and the subsequent mode of fracture of each ply of the laminate. The results revealed that laminate notched strength varied considerably with both a specified set of ply fiber orientations as well as the order in which the specific plies were arranged in the laminate. The fractographic examinations identified differences in the laminate fracture process which are believed to be the primary contributor to the differences in notched strength. The twelve laminates exhibited varying degrees of notch sensitivity as a result of the ability of a laminate to develop “subcritical” damage in a manner that relieved the high stress concentration at the notch tip.

The percent of laminate fracture by broken fibers was in direct correlation with the laminate notched strength. Laminates which were not characterized by damage zones containing major delaminations exhibited higher percentages of failure by broken fibers and higher notched strength. Conversely, when delaminations resulted in widespread ply uncoupling, relatively few plies of a laminate failed by broken fibers producing a weaker laminate.
Analysis of the In-Reactor Creep and Rupture Life Behavior of Stabilized Austenitic Stainless Steels and the Nickel-Base Alloy Hastelloy-X
Authors: Wassilew C , Ehrlich K , Bergmann HJ
Published: December 2008

An overall evaluation of several in-reactor creep and creep-rupture experiments in BR2 and FFTF on pressurized tubes of the stabilized austenitic stainless steels 1.4970, 1.4981, 1.4988 and the Ni-base alloy Hastelloy-X is given in this report. Even at temperatures around and above 0.5 Tm the analysis of the data implies that for low stress levels the stress-induced preferred absorption (SIPA) creep process is the predominant deformation mechanism. The results show that the in-reactor rupture lives of the austenitic steels as well as the Ni-base alloy Hastelloy-X are reduced compared with the rupture lives of the corresponding material in the unirradiated and post-irradiation tested conditions, so that an additional damage mechanism via helium has to be assumed to account for the reduction in rupture life.

Analytical models have been developed, which accounts for the critical variables stress, temperature, and dpa rate and which describes in a more general way the in-reactor creep and creep-rupture life behavior of the materials mentioned above. The analysis of the results indicates clearly that the use of the unirradiated and post-irradiation data for predicting in-reactor creep and failures is invalid for these materials.
Effect of Interstitial Impurities on Fracture Characteristics of A533-B Class 1 Pressure Vessel Steel
Authors: Jung YH , Murty KL
Published: December 2008

The effect of interstitial impurities through dynamic strain-aging [DSA] on the mechanical and fracture characteristics of A533-B Class 1 steel was examined using tensile, subsize Charpy three-point bend and single specimen unloading compliance J-integral tests. The tensile and fracture properties were studied as a function of the test temperature and applied strain-rate on the as-received pressure vessel [PV] steel material. The effect of neutron radiation exposure on both the tensile and fracture behaviors was investigated. The effect of DSA was noted to result in decreased fracture energies in the upper-shelf region. Neutron irradiation suppressed DSA resulting in improved mechanical and fracture properties of this steel at some temperatures and strain-rates. However, at very high temperatures DSA exhibited embrittlement in addition to that caused by radiation. Temperatures corresponding to fracture energy minima and the applied strain-rates followed an Arrhenius equation with activation energy identifiable with that for diffusion of C and N in steels plus their binding energy with alloying elements such as Mn and V.
Sixteen-Year Atmospheric Corrosion Performance of Weathering Steels in Marine, Rural, and Industrial Environments
Authors: Shastry CR , Friel JJ , Townsend HE
Published: December 2008

Weathering steels ASTM A 242-Type 1 and ASTM A 588-Grade B and steels with 0.21 and 0.021% copper are tested for atmospheric corrosion resistance in marine, rural, and industrial environments. The 16-year atmospheric exposure test results obey well the kinetic equations of the form C = AtB, where C is the corrosion loss, t is time, and A and B are constants. The corrosion resistance of steels is compared on the basis of times required to achieve a 250 μm thickness loss calculated using the rate equations. In these environments, weathering steel ASTM A 242 is at least 16 times more corrosion resistant than the 0.021% copper steel and at least four times more corrosion resistant than the 0.21% copper steel. Similarly, weathering steel ASTM A 588 is about eight times more durable than the 0.021% copper steel and at least two times more durable than the 0.21% copper steel.
Atmospheric Corrosion Problems with Weathering Steels in Louisiana Bridges
Authors: Raman A
Published: December 2008

ASTM A-588 weathering steels, grades A and B, used in bridge structures in the United States and abroad, are not as immune to atmospheric corrosion as originally predicted. Under dry conditions and wet and dry cycles of nearly equal length, the steel forms a protective rust layer and corrodes the least. However, under wetter conditions and in the presence of stagnant water, more rusting and the formation of nonprotective rust layers are found. The presence of chloride as well as other acid-forming pollutants in the atmosphere enhances corrosion. The rust layer forms coarse flakes, which lose adherence and protectiveness. Excessive flaking and a greater-than-expected loss of section thickness result. The presence of salt and high humidity, favorable for water condensation, promotes pitting under the flakes and sheets of rust. The rust develops in the form of small mounds and grows stepwise in layers, with the iron for the growth of the rust mound obtained from the metal underneath these mounds. Because of this, wide pits develop under the mounds and corrosion proceeds by the differential aeration cell mechanism. In areas where water stagnates, rusting occurs over the entire surface and a continuous rust layer develops from a sedimentary deposit. The presence of chloride and soluble salts derived from atmospheric contaminants promotes corrosion by not only increasing the conductivity of the condensed water, but by reducing the availability of oxygen at the corroding anodic sites as well.
Effects of Weathering of Chromate Passivation Films on Aluminum-Zinc Alloy Coated Sheet Steel
Authors: Cleary HJ
Published: December 2008

This paper presents a study of the effects of surface chromate passivation treatments on the corrosion rate and appearance of 55% Al-Zn coatings on sheet steel after weathering in an industrial atmosphere for a period of six years. Weight loss measurements were employed to determine corrosion rates, and surface appearance was evaluated by photoelectric reflection meter measurements and visual observations. It was found that increasing amounts of chromium (Iridite 9L6) applied to the surface of 55% Al-Zn coated sheet steel markedly decrease both the corrosion rate of the coating and the rate at which the surface gradually darkens in appearance and loses reflectivity caused by weathering. The bright reflective surfaces observed on six-year-old specimens with 14 mg/m2 chromium on the surface indicate that this level is a suitable minimum for preventing nonuniform weathering appearance problems and for optimizing the corrosion resistance. The applied surface chromium should not exceed about 31 mg/m2 chromium because of yellow surface discoloration at these higher levels.
The Corrosion of Stainless Steels in the Atmosphere
Authors: Kearns JR , Johnson MJ , Pavik PJ
Published: December 2008

A total of 38 types of stainless steel have been exposed for 1 to 15 years at a coastal site and 32 years in a semirural atmosphere. The resistance of stainless steels to degradation in the atmosphere was directly related to alloy chromium and molybdenum contents. Only American Iron and Steel Institute (AISI) Type 410 showed any signs of corrosion in the semirural environment. Significant corrosion product tarnishing occurred on all nonmolybdenum-bearing stainless grades after only one year of exposure in the marine atmosphere. Stainless grades that had been sensitized by an autogenous welding operation were susceptible to preferential corrosion at weld and heat-affected zone surfaces when exposed at the 250-m lot on Kure Beach, NC. Galvanic attack and corrosion product staining was observed for certain dissimilar metal couples between AISI Type 304 and other commercially pure metals, nickel-base and copper-base alloys. A photometric technique was used to quantitatively describe subtle changes in the appearance of three stainless steel surface finishes during exposure in a semirural atmosphere.
Long-Term Atmospheric Corrosion Behavior of Various Grades of Stainless Steel
Authors: Baker EA , Lee TS
Published: December 2008

Several grades of stainless steel are evaluated after 26 years of exposure in the marine atmosphere at Kure Beach, NC. The alloys evaluated include 1% Ni + 16% Mn, 5% Ni + Mn, 7 to 10% Ni, 12 to 13% Ni + Mo, 12Cr and 17Cr alloys. The test specimens are in the form of flat panels, with spot welds, arc weldments, and Erickson cup deformations.

An assessment is made of the degree of rust, rust stain, and pitting attack on the boldly exposed surface.

The materials exposed 25 m from the ocean have from 20% rust, 70% rust stain, (Type 316 stainless steel) to 100% rust (Type 410 stainless steel). Surface pitting is insignificant (<0.01 mm) on all material except Type 410 stainless steel, which has surface pits 0.06 mm in depth.

The materials exposed 250 m from the ocean have from 1% rust stain (Types 304 and 316 stainless steels) to 80% rust, 20% rust stain (Type 410 stainless steel), and surface pitting is insignificant.

The spot welded materials have a crevice area between the overlapped surfaces where significant pitting and intergranular corrosion occurs. The attack ranges between 0.08 to 0.17 mm in depth at the 25-m site, and between <0.01 to 0.10 mm in depth at the 250-m site. Spot weld failure caused by corrosion is found only on Type 430 stainless steel.

The arc welded materials show no evidence of weld failure. The weld and HAZ did have greater rust and rust stain cover than the panel surface.

The materials with Erickson cups show no evidence of stress corrosion failure. However, pitting is more severe in the stressed areas.
An Overview of Microstructural and Experimental Factors That Affect the Irradiation Growth Behavior of Zirconium Alloys
Authors: Fidleris V , Tucker RP , Adamson RB
Published: December 2008

This paper presents an overview of factors affecting irradiation growth of zirconium alloys. Recent data obtained from irradiation programs in EBR-II, ATR, and NRU reactors are used to illustrate the effects of various microstructural and experimental factors on the growth of Zircaloy, zirconium, and zirconium-niobium alloys irradiated to fluences up to 2 × 1026 nm−2 (E > 1 MeV) over the temperature range 330 to 720 K. Open literature results are also used to confirm or illustrate various effects. Important factors are texture, grain boundary parameters, residual stresses, original dislocation density, microstructure evolution, temperature during irradiation, solute effects, and fluence.