bluuebunny/crossref_metadata_2025 huggingface dataset:
Laser Beam Beta Heat Treatment of Zircaloy
Authors: Sabol GP , McDonald SG , Nurminen JI , Jacobsen WA
Published: December 2008

A commercially viable process of beta-phase heat treatment of Zircaloy tubing has been developed that circumvents the problems of dimensional stability at the treatment temperature, protection from oxidation, and control of beta grain size. The method utilizes a high-power, geometrically shaped laser beam that impinges on the surface of the tubing as the tubing is rotated and translated through the focused beam. Beam energy, surface temperature, and translation speed are chosen such that the zone of beta-phase formation penetrates approximately 30% of the wall thickness, and the self-quenching provided by the underlying material produces a uniformly rapid cooling rate. The laser treatment is performed in an argon-filled chamber on next-to-final-sized tubing, and tube properties are recovered by cold working to final size and final annealing. Tubing of Zircaloy-2 and Zircaloy-4 produced by the laser beam beta-phase treatment is immune to nodules on both the inside and outside surfaces in the 24 h, 773 K steam test, and post-transition corrosion rates of Zircaloy-4 are lower than those of conventionally processed tubing by factors of two to three in the 633 to 673 K temperature range. The laser beta heat treatment process and the resultant tubing properties are described.
Prevention of Delayed Hydride Cracking in Zirconium Alloys
Authors: Cheadle BA , Coleman CE , Ambler JFR
Published: December 2008

Zirconium alloys are susceptible to a mechanism for crack initiation and propagation called delayed hydride cracking. From a review of component failures and experimental results, we have developed the requirements for preventing this cracking. The important parameters for cracking are hydrogen concentration, flaws, and stress; each should be minimized. At the design and construction stages hydrogen pickup has to be controlled, quality assurance needs to be at a high enough level to ensure the absence of flaws, and residual stresses must be eliminated by careful fabrication and heat treatment.
Oxidation of Zircaloy-4 in Steam at 1300 to 2400°C
Authors: Prater JT , Courtright EL
Published: December 2008

The oxidation kinetics of Zircaloy-4 in steam have been extended to 2400°C. Growth of the ZrO2 and α-Zr(O) layers display parabolic behavior over the entire temperature range studied; however, a discontinuity in the oxidation kinetics above 1510°C causes rates to increase above those previously established by the Baker-Just relationship. This increase coincides with the tetragonal-to-cubic phase transformation in ZrO2−x. No additional discontinuity in the oxide-growth rate is observed upon melting of Zr(O). The effects of temperature gradients have also been taken into account, and corrected values representative of near-isothermal conditions have been computed.

Experiments have been performed in steam-hydrogen mixtures at 1565 and 1815°C. Concentrations of hydrogen up to 90 mol% have no effect on the oxidation kinetics. The rate-controlling factor appears to be the available flux of oxygen atoms incident to the reaction surface and is not dependent upon hydrogen content.
Fracture Behavior and Microstructural Characteristics of Irradiated Zircaloy Cladding
Authors: Chung HM , Yaggee FL , Kassner TF
Published: December 2008

Zircaloy cladding tube specimens from commercial power reactor fuel assemblies (burnup >22 MWd/kgU) have been deformed to fracture at 325°C by either the internal gas-pressurization or the expanding-mandrel technique in a helium or argon environment containing no fission product species (e.g., I, Cs, or Cd). The fracture surfaces of ten irradiated specimens fractured by internal gas pressurization were examined by scanning electron microscopy; six specimens were found to contain various degrees of the pseudocleavage feature that is characteristic of pellet-cladding interaction failures. Out of ten test specimens fractured by expanding-mandrel loading, five were found to contain regions of pseudocleavage on the fracture surfaces. The specimens exhibited “X-marks” on the outer surface and brittle incipient cracks distributed on the inner surface, which are also characteristic of pellet-cladding interaction failures. Transmission/high-voltage electron microscope examinations of the thin-foil specimens obtained from regions adjacent to the failure sites showed that the ductile-failure specimens were characterized by a high density of dislocations which showed normal →α-type Burgers vectors. In contrast, the brittle-type specimens were characterized by comparatively few dislocations which formed substructures. The dislocations in the brittle specimens were decorated by Zr3O precipitates 2 to 6 nm in size, and cubic-ZrO2 precipitates ≲ 10 nm in size were also observed in high density. These observations indicate a general immobilization of the dislocations. The low-ductility brittle-type failures appear to have been produced primarily as a result of the Zr3O and cubic-ZrO2 precipitates, augmented by precipitates of bulk hydride 35 to 100 nm in size. The bulk nature of these precipitates, which contrasts with the surficial nature of monoclinic ZrO2 and χ-hydride precipitates, was indicated from stereomicroscopy of weak-beam dark-field images. In situ irradiation of the spent-fuel cladding specimens by 1-MeV electrons at 325°C indicates that the Zr3O and cubic-ZrO2 precipitation is irradiation-induced, whereas the bulk hydride is not.
Round-Robin Testing of Low-Scatter Optics
Authors: Bennett JM , Stowell WK
Published: December 2008

For high quality laser optics it is important to compare measurements of surface quality made in different laboratories, determine how scattering levels of silver coatings produced by different groups compare, and what effects, if any, are introduced by stripping the silver coatings and by handling and transporting samples between laboratories. A round-robin study attempted to answer these questions. Participating laboratories included the Avionics Laboratory at the Air Force Wright Aeronautical Laboratories (AFWAL), Dayton, Ohio, Michelson Laboratory at the Naval Weapons Center (NWC), China Lake, California, and the Air Force Weapons Laboratory (AFWL), Albuquerque, New Mexico. Fourteen very low-scatter, optically polished synthetic fused silica (Suprasil) and natural fused quartz (Homosil) samples were purchased from Robert M. Silva of VTI, Dayton, Ohio. Angular scattering, i.e., bidirectional reflectance distribution function (BRDF), was measured on all the uncoated samples and three silver-coated samples at AFWAL using a variable angle scatterometer. Eleven additional samples were silver coated at NWC, and total integrated scattering (TIS) was measured on all silver-coated samples. Transmission electron micrographs were made of the surfaces (silvered and also stripped) of two samples, and selected coated and uncoated samples were profiled. TIS was then measured on the instrument at AFWL. At AFWAL BRDF measurements were made on all the samples, both silver coated and then stripped, and TIS measurements were repeated on selected samples at NWC. It was found that the TIS measurements made at NWC and AFWL were in good agreement. Scattering from bare substrates increased after silver coating and stripping, and there was a large variability in the silver coatings, particularly those made at NWC. Critical factors in obtaining low-scatter silver surfaces appeared to be the cleaning and coating of the samples. The results of the round-robin measurements are discussed in detail in this paper.
Charge Emission and Related Precursor Events Associated with Laser Damage
Authors: Becker MF , Domann FE , Stewart AF , Guenther AH
Published: December 2008

Charge emission and surface photoconductivity were used to investigate possible precursors to laser damage, including surface cleaning and hardening. Experiments were conducted with a 1.06 micron ND:YAG laser with 5 nsec pulses. A wide range of samples were investigated, including diamond-turned copper mirrors, silicon wafers, and half-wave dielectric films of ThF4, Al2O3, and Ta2O5 on fused silica.

Charge emission at 1/10 of the single pulse damage threshold was observed for the copper mirrors. Declining emission for successive pulses was characteristic of surface cleaning. Emitted charge quantities increased monotonically with fluence prior to damage, but the charge emission was noisy with site-to-site variations. For silicon, damage was simultaneous with charge emission for both l-on-l and N-on-l tests. The damage morphologies for the two cases were distinctly different. Nonlinear absorption measurements were conducted on silicon for fluences below the single pulse damage threshold.

The two oxide dielectric films had gold electrodes evaporated on them leaving gaps of 0.75 to 2.0 mm for measuring surface conduction. Charge was collected from this configuration at 1/20 of the single pulse threshold. The charge quantity was very noisy and apparently uncorrelated with fluence. Surface hardening was observed for the ThF4 film and it did not emit until damage was initiated.
Characterizing the Effect of Delamination Defect by Mode I Delamination Test
Authors: de Charentenay FX , Harry JM , Prel YJ , Benzeggagh ML
Published: December 2008

Delamination is an important step in the fracture of laminates. In order to characterize this phenomenon, tension opening (Mode I) tests have been carried out. Monitoring by acoustic emission allows the determination of an initiation fracture energy that is characteristic of the material bonding. Analysis by fracture mechanics of the delamination propagation shows that the resistance curves description is a very useful presentation of the delamination behavior. Results of experiments on glass-polyester, carbon-epoxy, and kevlar-epoxy are presented. The influence of moisture content on the R-curves of carbon-epoxy laminates is included.
A Mixed-Mode Fracture Analysis of (±25/90n)s Graphite/Epoxy Composite Laminates
Authors: Law GE
Published: December 2008

An investigation of the fracture mechanisms and behavior of sub-laminate cracking in graphite/epoxy composite laminates is presented. A series of laminates of the form (±25/90n)s is chosen for analytical modeling and compared with experimental results. By varying the number of 90-deg plies, indicated by n, several important and distinct fracture modes are identified. The thickness of the 90-deg layer is the single parameter that separates these fracture events. The present work focuses in particular on the mechanisms of transverse ply cracking and free-edge delamination.

The energy release rate approach of classical fracture mechanics is applied to describe the crack initiation fracture process. The cracking process is numerically simulated using a finite-element procedure formulated within the framework of ply elasticity and on the assumption of a generalized plane-strain state. The numerical procedure explicitly calculates the Mode I, Mode II, and Mode III components of the strain-energy release rate as a function of crack length. Unit mechanical and unit thermal load conditions are solved, and the results are superposed to obtain the general load case. The analytical model predicts the sequence of occurrence of the fracture modes and the critical onset loads.

The theoretical model is then correlated with published experimental data including tension tests on (±25/90n)s (n = ½, 1, 2, 3, 4, 6, and 8) laminate coupons manufactured using the T300/934 graphite/epoxy system and with fracture tests using double-cantileverbeam and cracked-lap-shear specimens. Good agreement is obtained between the theoretical and experimental results. The general nature of the present analytical method is readily applicable to composite laminates of more complicated structural geometry or loading conditions or both.
Criticality of Disbonds in Laminated Composites
Authors: Chatterjee SN , Pipes RB , Blake RA
Published: December 2008

Usefulness of analytical methodologies and nondestructive tests for assessing criticality of disbonds in laminated composties is examined. Fracture mechanics approach and critical energy release rate concepts are employed for the prediction of catastrophic growth due to quasi-static transverse shear loading. Semi-empirical growth laws are considered for modeling slow growth under cyclic loading.

Brief descriptions of the analytical methods utilized for calculation of energy release rates are given. Sizes and locations of implanted disbonds in graphite/epoxy laminates are determined from ultrasonic C-scans. Analytical results and quasi-static destructive test data for beams subjected to three-point bending are correlated for determining the critical value of energy release rate. Effects of initial flaw size, location, sharpness of disbond tips, as well as mixed-mode (I and II) loading conditions are studied. Ultrasonic C-scans are also used for monitoring growth of disbonds in plate-type structures under cyclic transverse shear. Least square fits are attempted with the disbond growth rate data.
Strain-Energy Release Rate Analysis of Cyclic Delamination Growth in Compressively Loaded Laminates
Authors: Whitcomb JD
Published: December 2008

Delamination growth in compressively loaded composite laminates was studied analytically and experimentally. The configuration used in the study was a laminate with an across-the-width delamination. An approximate superposition stress analysis was developed to quantify the effects of various geometric, material, and load parameters on Mode I and Mode II strain-energy release rates GI and GII, respectively. Calculated values of GI and GII were then compared with measured cyclic delamination growth rates to determine the relative importance of GI and GII. High growth rates were observed only when GI was large. However, slow growth was observed even when GI was negligibly small. This growth apparently was due to a large value of GII.
Influence of Ply Cracks on Fracture Strength of Graphite/Epoxy Laminates at 76 K
Authors: Kriz RD
Published: December 2008

Quasi-isotropic laminates ([0/90/±45]s and [0/±45/90]s) were fabricated from graphite/epoxy and quasi-statically loaded in tension at 76 K until fracture occurred. Fibers in 0-deg plies carry the largest portion of the tensile load; the weaker 90- and 45-deg plies crack at loads much lower than fracture strength. The effect of ply cracks on fracture of load-bearing 0-deg plies was examined to understand how defects affect laminate strength. A generalized plane-strain finite-element model was used to predict stress gradients in the 0-deg ply near the crack tip. Variations in residual stress caused by changes in temperature and absorbed moisture were included in the analysis. The experiments indicated that absorbed moisture significantly alters the fracture strength and fracture surface of a dehydrated [0/90/±45]s laminate tested at 76 K. The 0-deg plies of dehydrated laminates fractured along several 90-deg ply cracks. When moisture saturated a [0/90/±45]s laminate, a single 90-deg ply crack dominated the fracture of the 0-deg ply and the laminate fracture strength decreased 8%. Analysis of residual stresses indicated that a higher residual stress state existed near the 90-deg ply crack when moisture was absorbed.
Treatment of Oil Spill Fire Hazards with Chemical Dispersants: A Case History
Authors: Kaufmann S
Published: December 2008

Federal contingency plans include the use of chemical dispersants to ameliorate hazardous situations caused by spills of flammable or explosive petroleum products. The closing of the Williamsburg Bridge in New York City, when a gasoline tanker exploded and sank under it, was nearly overshadowed by the leakage of 7 750 000 L (2 000 000 gal) of gasoline from a storage facility in Boston. The threat to a densely populated neighborhood of six-family tenement houses and a large racetrack that stabled hundreds of Thoroughbred horses led to the use of a chemical dispersant to neutralize the fire hazard. Favorable results by fire departments in recent years, as a result of training, have established dispersants as the method of choice to handle nonburning spill incidents. Even though the teams that responded to several such emergencies of course held the protection of life and property as paramount, no toxicological environmental effects were noted during subsequent observations.
Evaluation of Radium and Toxic Element Leaching Characteristics of Florida Phosphogypsum Stockpiles
Authors: May A , Sweeney JW
Published: December 2008

The U.S. Bureau of Mines conducted studies to determine if phosphogypsum, a waste material from the processing of phosphate rock, contains hazardous toxic materials as defined by the Environmental Protection Agency (EPA) and whether leaching of these toxic materials and radium may occur. Samples of the phosphogypsum stockpiled material were evaluated using the EPA extraction procedure, atomic absorption, neutron activation, X-ray diffraction, and chemical and physical means. Radiological tests performed used both the germanium-lithium and emanation methods. The data show that the phosphogypsum stockpiles are not hazardous toxic waste as defined by EPA criteria. Trace elements and radium are not leached from the phosphogypsum stockpiles. Absorption of trace elements and radium by phosphogypsum is the major reason for their not being leached. The standard error of measurement of radium concentrations was 4.7 pCi/g.
Stress and Fracture Analysis of Tapered Attachment Lugs
Authors: Kathiresan K , Hsu TM , Rudd JL
Published: December 2008

Attachment lugs are frequently used in aerospace applications to connect major structural components. It is important to assess the structural integrity of such lugs with cracks present. These assessments are necessary to prevent abrupt failure of the lugs before their intended service lives are reached. The estimation of the associated fatigue life of a lug, which consists of crack initiation and crack growth periods, demands stress and fracture analyses of the lug. In this paper, the results of two-dimensional stress and fracture analyses of tapered attachment lugs subjected to symmetric and off-axis loadings are presented. The effects of various parameters such as the outer-to-inner diameter ratio, crack length, and crack location on the tangential stress distribution, pin contact pressure distribution, stress concentration factor, fatigue critical location, and stress intensity factor are investigated. The finite element method utilizing a crack-tip singularity element is used in the analyses.
The Ball Bond Shear Test: Its Methodology and Application
Authors: Charles HK , Clatterbaugh GV , Weiner JA
Published: December 2008

Results of a comprehensive ball shear testing program are presented including methods for ball shear implementation and wire bonding machine optimization. Both destructive and non-destructive ball shear are considered as complementary test methods to the more familiar wire bond pull test. Techniques for on-line production testing are presented along with suggested guidelines suitable for incorporation in a standard test method. The use of ball shear testing as a method for studying the effect of both thermal processing and contamination on the strength and morphology of the aluminum-gold interface is also considered.
Vapors, Odors, and Toxic Gases from Landfills
Authors: Young P , Parker A
Published: December 2008

Landfill gas from eight different sites in the United Kingdom was analyzed for trace constituents. Municipal, industrial, and liquid codisposal sites were included. A hazard assessment was made on the basis of the concentrations of potentially toxic components, and some of the causes of landfill odors were identified.

Three trapping methods were used to provide samples for analysis by gas chromatography/mass spectrometry. Supplementary techniques were employed to quantify the bulk gases, hydrogen sulfide, and metallic elements present.

Over 100 organic constituents were identified, but only 10 exceeded their individual recommended toxicity threshold limit values. Toxic compounds were more abundant at industrial sites. Odors were strongest from recently deposited waste, with methanethiol exceeding the odor threshold by a factor of more than 106. Hydrogen sulfide was not a significant cause of odor. Odors from the compounds identified and quantified depend more on the stage of decomposition than on the nature of the waste, and industreal wastes did not exacerbate the smell.
Chromium-Bearing Waste Slag: Evaluation of Leachability When Exposed to Simulated Acid Precipitation
Authors: Kilau HW , Shah ID
Published: December 2008

Waste slag dumps constitute a large potential source of chromium contamination of groundwaters, particularly under the enhanced leaching action of acid precipitation. Laboratory leaching experiments were carried out to determine the composition factors controlling the chromium leachability of waste slags when exposed to acidic solutions designed to simulate acid precipitation.

Two critical slag composition factors were found to control the chromium leachability: (1) the calcium oxide (CaO)/silicon dioxide (SiO2) ratio and (2) the magnesium content. It was determined that above a 2.0 CaO/SiO2 ratio, chromium exists in slag as calcium chromite, which can be vulnerable to leaching by acid precipitation, especially if it is oxidized to calcium chromate when exposed to the environment over an extended period.

Experimental results showed that maximum chromium leachability from industrial slags occurred when the composition of the slag was at about a 2.0 CaO/SiO2 ratio. Between a 1.0 and 2.0 CaO/SiO2 ratio, in the presence of sufficient magnesium, picrochromite (MgO · Cr2O3) was formed, which is very stable towards oxidation and was resistant to dissolution by simulated acid precipitation.
Trace Metal Interactions Affecting Soil Loading Capacities for Cadmium
Authors: Baker DE , Rasmussen DS , Kotuby J
Published: December 2008

The goal of this investigation was to establish a theoretically applicable model of, and develop an approach for, the direct measurement of cadmium loading capacities under laboratory conditions. Data from the literature were fitted to a model indicating a direct, linear relationship between the logarithm of the activity of Cd2+ in the soil solution and the logarithm of plant uptake of cadmium. These results support the model for passive absorption of cadmium by plants. It was postulated that the diffusion of Cd2+ from the soil-adsorbed phase to plant roots results from the electrochemical potential gmCd, gradient established between soil-adsorbed Cd2+ and that in solution, which is depleted as a result of passive absorption by plants.

Laboratory methods for relating the negative logarithm of the activity of Cd2+ in solution, pCd, to soil-adsorbed cadmium and plant-absorbed cadmium were developed, and test results for each are presented. It was concluded that this approach is theoretically valid and will provide routine laboratory methods for measuring soil loading capacities to protect the human food chain from undesirable concentrations of cadmium.
Disposal of Oil-Containing Sludges on Farmlands
Authors: Mucsy G , Kránicz-Pap E , Urbányi G
Published: December 2008

The response of soils and plants to oil-containing sludges was studied by pot, small plot, and field experiments. The objective was to develop a simple method of farmland disposal without detrimental effects on the environment.

Dewatered sludge from a petroleum storage plant, in combination with nitrogen fertilizer, was found most suited to farmland disposal. The sludge was applied to sandy soil at rates from 3 to 8 g oil per kilogram of soil, and during a single growing season (six months) 60 to 90% of the oil was decomposed. No oil was detected below a 60-cm depth. Some physical properties of the soil, particularly the texture and water-retaining capacity, were improved. The plants were analyzed for protein, phosphate, and potassium oxide and found to have suffered no detriment and no loss in crop yield. The method of disposal by conventional agrotechnical operations proved environmentally safe and economically superior to other alternatives.
Management of Solid Wastes in the Iron and Steel Industry
Authors: El-Gohary F , El-Khouly MS
Published: December 2008

Wastes from a local iron and steel factory are the subject of this study. The manufacturing operations in the plant under consideration are agglomeration of iron ore and sintering, pig iron manufacture, steel making, rolling mill operations, and pickling.

Liquid slag, produced in the blast furnace, is granulated in water and used as a concrete additive. Other wastes are directed separately to sedimentation tanks. The settleable solids are reused, and the treated effluents are pumped to a cooling tower for recycling.

As a result of the new manufacturing expansion, existing waste treatment facilities are not adequate, and it was found necessary to provide additional treatment techniques.

Departmental, as well as composite wastes were treated using plain sedimentation, centrifugal sedimentation, or chemical coagulation, or a combination of these methods.

The results obtained showed that the use of the hydrocyclone for solid-liquid separation is much more efficient than plain sedimentation. When this process was followed by coagulation, very promising results were obtained. The use of pickling liquor as a coagulant gave comparable results with alum and ferric chloride.
Three-Dimensional Finite and Boundary Element Calibration of the Short-Rod Specimen
Authors: Ingraffea AR , Perucchio R , Han T-Y , Gerstle WH , Huang Y-P
Published: December 2008

The results of numerical calibration of a proposed standard short-rod specimen are reported. Three-dimensional finite and boundary element approaches were used to compute compliance and average stress-intensity factor as a function of crack length. Local variation of stress intensity along the crack front was computed for nine crack lengths. Calibration constants for fracture toughness evaluation were found to be: ¯Ymin = 28.3 and Amin = 23.4. A convergence study indicated that these values are lower bounds accurate to within 1%. Stress intensity was found to be minimum at the specimen centerline and maximum at the chevron edge for each crack length analyzed. At the critical crack length, the edge value was about 20% higher than the centerline value for an assumed straight crack front. Comparison of the boundary and finite element approaches indicated that, for the same stress intensity factor accuracy, the boundary element solution time was about 15% less than that of the finite element method.
A Short-Rod Based System for Fracture Toughness Testing of Rock
Authors: Ingraffea AR , Gunsallus KL , Beech JF , Nelson PP
Published: December 2008

A system for fracture toughness determination of rock using a short-rod specimen is described and evaluated. The calibration of the specimen by finite-element analysis for two loading cases is reviewed. A description of the preparation procedure is given showing the practicality of the testing system. Verification of the system is accomplished through testing of polystyrene, Indian limestone, and Westerly granite. The results from these tests compare favorably to fracture toughnesses measured by other more expensive and time consuming methods.
The Use of the Chevron-Notched Short-Bar Specimen for Plane-Strain Toughness Determination in Aluminum Alloys
Authors: Brown KR
Published: December 2008

An extensive study of the use of the chevron-notched short-bar (CNSB) specimen for measuring plane-strain fracture toughness in high-strength aluminum alloys is reported. The toughness measured in a CNSB specimen, KSB, correlates closely with plane-strain fracture toughness, KIc, for toughnesses less than 35 MPa m1/2. At higher toughnesses KSB is higher than KIc for two reasons; first, sample heterogeneity causes the different sized specimens to sample different material, and second, an effect of rising crack growth resistance in the toughness range 40 to 55 MPa m1/2; these latter test results should be considered invalid; however, within this range the KIc, KSB correlation, although largely empirical, is still useful for screening purposes.

The toughness in high-strength aluminum alloy rolled plate may vary markedly through the plate thickness. Examples of these variations are presented.
Fracture Toughness of an Aluminum Alloy from Short-Bar and Compact Specimens
Authors: Eschweiler J , Marci G , Munz DG
Published: December 2008

Fracture toughness of a 70-mm-thick plate of the aluminum alloy 7475-T7351 was measured with short-bar and compact specimens. The compact specimens with thicknesses of 25 and 38 mm and the short-bar specimens with thicknesses of 12.5, 25, and 50 mm had T-L orientation and were machined at different distances from the surface. Different heats of the same alloy tested in T-L and L-T orientation furnished a series of fracture-toughness values ranging from 40 to 60 MPa m1/2 in increments of approximately 2 MPa m1/2. For each of the selected heats KIc and KIcSB was determined. Both fracture toughness test methods confirmed a fracture-toughness profile through the thickness direction of the plate. The fracture toughness was highest in the midsection and lowest in the surface region of the plate. Increasing fracture toughness with increasing specimen size was found for both testing methods, but KIcSB was consistently higher than KIc for specimens of identical thickness. The difference between KIc and KIcSB increases with increasing fracture toughness. From the results it is concluded that the through thickness variation of KIc is not the main reason for the higher short-bar values.
A Chevron-Notched Specimen for Fracture Toughness Measurements of Ceramic-Metal Interfaces
Authors: Mecholsky JJ , Barker LM
Published: December 2008

A new double cantilever beam specimen with a chevron notch (short bar) has been developed to measure the fracture toughness, (or resistance), GIc, of ceramicmetal interfaces. The analysis of the specimen is based on previously developed compliance calibrations for homogeneous materials. Toughness measurements on a zinc-silicate glass ceramic-molybdenum system demonstrated that the bond at this interface is as tough (13 J/m2) as the glass ceramic alone. Measurements on a lithium silicate glass ceramic-Hastelloy 276 metal system showed that the toughness of the interface depends on the degree of bonding ranging from 19 J/m2 for weak bonding to 54 J/m2 for strong bonding. This specimen is being suggested for use in the study of the effect of heat treatment and bonding chemistry on fracture of metal-ceramic interfaces.
Fatigue Crack Propagation of 25Mn-5Cr-1Ni Austenitic Steel at Low Temperatures
Authors: Yokobori T , Maekawa I , Tanabe Y , Jin Z , Nishida S-I
Published: December 2008

A study has been carried out on the fatigue behavior of a newly developed high-manganese steel intended for low-temperature applications in the range from 0 to −174°C. As-rolled and solution-treated high-managanese steel were tested. The fatigue behavior of commercial austenitic steel was also presented for comparison.

The fatigue life of high-manganese steel was found to increase with decreasing temperature from 0 to −174°C. Crack growth rates were expressed in terms of the Paris relation da/dN = C(ΔK)n, and the power coefficient n was shown to depend on temperature. The temperature dependence of crack growth rate and n, as well as the linear dependence of apparent activation energy of the fatigue crack growth rate on the logarithm of the stress intensity factor range, are explained by the dynamic theory of fatigue crack growth.

Fatigue fracture toughness (Kfc) was found to increase with decreasing temperature. The effect of welding on Kfc is also shown.
Profiles of Fatigue Damage in Graphite/Epoxy Composites from Ultrasonic Transmission Power Spectra
Authors: Cantrell JH , Winfree WP , Heyman JS
Published: December 2008

Early fatigue damage in non-unidirectional multi-ply graphite/epoxy composites is manifested by a distribution of cracks and disbonds through the bulk of the material. Such damage is subtle and is difficult to detect with conventional ultrasonic technology. Consequently, a new ultrasonic measurement technique called phase-insensitive tone-burst spectroscopy has been developed. The new technique eliminates problems associated with phase cancellation and pulse shape artifacts inherent to conventional broadband ultrasonic spectral measurement systems and produces clean spectral information irrespective of specimen inhomogeneity or irregularities in surface geometry. Application of the new technique to measurements of graphite/epoxy composites has yielded frequency-domain profiles that show distinct differences in ultrasonic attenuation, attenuation slope, and velocity for each specimen experiencing a different level of fatigue damage.
Structure and Properties of an Integrated 3-D Fabric for Structural Composites
Authors: Ko FK , Pastore CM
Published: December 2008

Based on experimental observations, a theoretical framework has been established to quantify the geometry of a three-dimensional braided fabric. Predictions of the strength of the fabric and composite were made using a geometric model.
Evaluation of Asphaltic Pavements for Overlay Design
Authors: Deen RC , Southgate HF , Sharpe GW
Published: December 2008

To evaluate projects involving approximately 200-route-miles of interstate and primary pavements in Kentucky and Tennessee in relatively short time frames, it was decided to test, analyze, and design overlays using test equipment (Road Rater®) and procedures developed by the University of Kentucky Transportation Research Program. This paper presents the analysis methodology and the evaluation and overlay designs for selected projects, including the before and after analysis of milling on one project.

The Road Rater applies a dynamic sinusoidal loading of known force and frequency. The velocity of the vibration waves are measured by sensors and integrated electronically to obtain surface deflections. An analysis of the shape and magnitude of the deflection bowl permits an assessment of whether the structure is performing as anticipated or whether some component is significantly weaker than designed. Analyses permit the determination of the “behavioral” or effective thicknesses of the asphaltic concrete layers and the in-place subgrade moduli. Strip charts of effective thickness and subgrade strength (or alternatively, overlay thicknesses) along the length of a project permit delineation of the project into relatively uniform segments. The arithmetic mean and standard error are determined for each segment to estimate design parameters. The required overlay thickness is the difference between the total thickness required for new construction to carry the anticipated traffic and the behavioral thickness of the existing pavement.
Pavement Friction Measurements and Vehicle Control Reparations for Nontangent Road Sections
Authors: Balmer GG , Zimmer RA , Tonda RD
Published: December 2008

Several measurement systems were evaluated to determine their applicability for measuring wet-pavement friction on transitional roadway sections. It was found that the two-wheel trailer is capable of such measurements if it is instrumented to measure the vertical dynamic test-wheel load as well as the longitudinal drag force during locked-wheel braking. A less desirable approach is to use accelerometers to measure the lateral and vertical accelerations on the trailer and compute the wheel load from these measurements.

There is greater friction deterioration on curves, ramps, intersections, and other transitional roadway areas from traffic wear and the environment than on tangent sections. When these roadway sections become slick or have marginal skid resistance, they can be milled, grooved, resurfaced, or overlaid applying a sprinkle treatment to restore adequate friction characteristics. This paper addresses both the measurement and the restoration aspects of this problem.
The Use of an Asphalt Polymer/Glass Fiber Reinforcement System for Minimizing Reflection Cracks in Overlays and Reducing Excavation Before Overlaying
Authors: Rowlett RD , Uffner WE
Published: December 2008

Many techniques have been used in an attempt to prevent reflection cracking in asphalt overlays including stress relieving membranes, fabrics, bond breakers, and changes in mix design. Glass fiber reinforcements have been used in the plastics industry for increasing the fatigue life and fracture toughness of plastic products for many years. This paper describes the successful development of the use of glass fiber reinforcement in conjunction with an asphalt polymer to minimize reflection cracks in an asphalt overlay. The system is also used to reduce excavation of deteriorated cracks and joints before overlaying.

The glass fiber reinforcement is a high strength woven glass with a tensile strength of 1750 N/cm (1000 lb/in.) width. The asphalt polymer was specially designed for use with the glass fiber reinforcement and has excellent properties of adhesion, low-temperature flexibility, and high softening point.

The combined properties of the system are the key to performance. The asphalt polymer adheres to the old road, the glass fiber reinforcement, and the new overlay, protects the glass fiber reinforcement, acts as a stress relieving membrane, and transfers the stresses to the reinforcement. The glass fiber reinforcement distributes the stress over the width of the repair to a level below the fracture point of the overlay. Laboratory tests were used to determine the physical properties and characteristics of the system, but no laboratory tests were found to predict the field performance. Evaluation of the system was performed through field trials. Over a five-year period 150 field trials were installed in 21 states. These trials included transverse and longitudinal cracks in bituminous roads and transverse joints, longitudinal joints, and interslab cracks in portland cement concrete base roads. Approximately 30 480 m (100 000 ft) of the repairs were monitored for crack reflection. The asphalt polymer/glass fiber reinforcement system was 89% effective in reducing reflection cracks. The average age of the trials was 21 months with a range of 6 to 56 months. All trials were exposed to a minimum of one winter.

In recent trials this system has been used to reinforce badly distressed areas around joints or cracks in lieu of partial or full depth excavation. Cost savings greater than ten to one have been demonstrated for the asphalt polymer/glass fiber reinforcement system with equivalent or better performance than excavation.
The Use of a Gyratory Testing Machine in the Evaluation of Cold-Recycled Asphalt Paving Mixtures
Authors: Tia M , Wood LE
Published: December 2008

This study evaluated the feasibility of using the gyratory testing machine in the fixed roller mode for evaluating the long-term behavior of cold-recycled asphalt mixtures. Cold recycled asphalt mixtures were compacted with the gyratory machine, and gyratory strain indices were obtained from the gyrograph recorded during the compaction process. The resilient modulus, Hveem stabilometer R value, and Marshall stability were obtained on the compacted recycled mixes at various curing times and were correlated to the gyratory strain indices. The scope of study presented in this paper covered two types of pavement material and five types of added softening agents, which included a high-float asphalt emulsion AE-150, a foamed asphalt and the rejuvenating agents, Reclamite®, Mobilsol®, and Dutrex 739®.

The results of the study indicated that the gyratory stability index (GSI) and the gyratory elasto-plastic index (GEPI) could be used to detect unstable mixtures when the binder content was too high. The GSI and GEPI correlated fairly well with the Hveem stabilometer R value of the recycled mix. However, they correlated poorly with the resilient modulus and Marshall stability of the recycled mix. Similar to the R-value test, the gyratory testing machine can be used to determine the optimum binder content of a cold-recycled mix.

The scope of this study was limited to the use of the gyratory testing machine in the fixed roller mode. Tests using the oil filled roller mode had not been conducted in this investigation.
Vickers Indentation Curves of Elastoplastic Materials
Authors: Loubet JL , Georges JM , Meille G
Published: December 2008

Studies of Vickers indentation curves of elastoplastic materials give information about the relationship between plasticity and elasticity. We have built equipment which gives a record of the applied depression depth, h, as a function of the carried load, P (range, 0.5 to 20 N).

Investigation of the Vickers indentation curves, P(h), during loading and unloading and microscopic observations shows that the phenomena occurring during indentation are complex. We first discuss the loading curve. A comparison with a theoretical analysis is made. Young's modulus, E, and the Vickers indentation pressure during loading can be calculated from the unloading and loading curves. The meaning of the different characteristic parameters of the depth-load graphs is debated. Their correlation with optical measurements of the remanent Vickers indentation is proposed.
Use of the Scanning Electron Microscope in Microhardness Testing of High-Hardness Materials
Authors: Westrich RM
Published: December 2008

Thin coatings of titanium nitride (TiN), zirconium nitride (ZrN), and hafnium nitride (HfN) are difficult to measure for hardness by any technique other than microhardness measurement. The question of apparent hardness increase with decreasing load has been the subject of much discussion, and many explanations have been offered, such as those of Gane and Cox and of Bulter. Impressions measured at high and low loads on a single hardness standard typically show higher hardness readings with lower loads. Correction factors have been suggested, however, there is still some question concerning the absolute hardness at low loads.

The purpose of this work is to show a technique, using the scanning electron microscope (SEM) and a diffraction grating for a measurement standard, that produces more accurate microhardness readings. Further, data suggest that very thin coatings, on the order of 2 to 5 μm, can be measured for hardness. A hardness standardization and comparison technique was also developed to relate microhardness readings from different hardness scales more accurately. Computer techniques were utilized to fit the hardness data for hardness scale comparisons.
Polarization Studies on Surgical-Grade Stainless Steels in Hanks' Physiological Solution
Authors: Ogundele GI , White WE
Published: December 2008

The corrosion resistance of a wrought Type 316L stainless steel (WSS316L) and a surgical-grade stainless alloy (SG2SA) were studied. The behavior of the alloys, as influenced by chloride (Cl−) and bicarbonate (HCO3−) ion concentrations, as well as pH and temperature in Hanks' physiological solution, were explored using electrochemical techniques.

The results show that SG2SA exhibited a more noble response and higher passive breakdown potential than WSS316L. Both materials were significantly affected by changes in Cl− and HCO3− ion concentrations. The corrosion and breakdown potentials shifted to more negative values with increasing Cl− ion concentrations, but to more positive values with increasing HCO3− ion concentrations. The alloys displayed most noble characteristics in neutral solutions and at higher temperature conditions.

The alloys were found to be active only in highly acidic solutions at potentials below −300 mV versus saturated calomel electrode (SCE). Furthermore, the materials were found to experience an early passive film breakdown at higher temperatures, indicating that the passive film is more stable at lower temperatures.

Cyclic polarization tests on WSS316L showed that the chance of repassivation of actively growing pits is very limited in environments containing variable Cl− and HCO3− ion concentration as well as at higher temperature.

As both of the test materials were determined, from chemical analyses, to conform to AISI Type 316L stainless steel, the observed differences in corrosion behavior are explained on the basis of different chemical composition and microstructural differences as observed by metallographic analyses.
Surface Fissuring of Polyurethanes Following In Vivo Exposure
Authors: Szycher M , McArthur WA
Published: December 2008

Compared to standard silicone elastomers, polyurethanes offer enhanced mechanical properties, improved durability, and reduced wall thickness for pacing leads. These thinner-wall polyurethane leads can be used in smaller vessels, or will allow multiple leads to be introduced into a single vein.

Recent reports have shown that pacing leads made with Pellethane 2363-80A exhibit shallow surface fissuring; some pacemaker or lead constructions have failed, particularly at areas of chronic mechanical stress. Several mechanisms have been proposed as the cause of surface fissuring: protein absorption with associated swelling, leaching of low molecular weight substances to the surface, or lipid absorption. However, there is little evidence supporting any of these mechanisms.

Our studies suggest that polyether-based polyurethanes are susceptible to in vivo oxidation of the polyether chain. In this chain, the most susceptible group is the -CH2 group in the alpha position to the ether oxygen, which undergoes peroxidation, free radical dissociation, and, eventually, chain cleavage, possibly leading to a reduction in molecular weight averages. Attenuated total reflectance infrared (ATR-IR) studies at the surface of the fissured polyurethanes have shown the presence of oxidative byproducts such as hydroxyl end groups (-OH).

Based on these preliminary results, we hypothesize that progressive surface degradation is caused, in part, by stress-induced oxidation of the polyether macroglycol used in the synthesis of polyurethane elastomers. Our hypothesis has been reinforced by experimental evidence that surface cracking can be significantly reduced, if not eliminated, by using higher-durometer polyurethanes, because these polymers contain fewer polyether macroglycol chains in the molecular backbone.
An Engineering View of Laboratory Corrosion Tests
Authors: Treseder RS
Published: December 2008

Many laboratory tests designed to assist in engineering decisions regarding materials selection have not received the desired user acceptance. Possible explanations for this situation are discussed with examples taken from test methods for evaluating stress corrosion cracking of alloys and crevice corrosion susceptibility of stainless steels in chloride systems. Suggested means of improving tests include: (1) improved definition of the limits of the corrosion system for which the test is designed, (2) use of the rank ordering concept in evaluating materials, (3) selecting rank ordering factors that are mechanistically sound and that have engineering significance, (4) correlating laboratory data with field experience to establish acceptable/unacceptable criteria for alloys for specific environments, and (5) standardizing test details so that comparable results can be obtained by different laboratories.