bluuebunny/crossref_metadata_2025 huggingface dataset:
Gyratory Evaluation of Aggregate Blends to Determine their Effect on Shear Resistance and Sensitivity to Asphalt Content
Authors: Ruth BE , Shen X , Wang L-H
Published: March 2009

Transverse and longitudinal shoving of asphalt paving mixtures is primarily related to the inability of current test methods to identify the properties of mixtures at different levels of traffic densification and the influence that aggregate properties have on the mixtures' resistance to plastic deformation (shoving). Research was conducted to investigate the use of the air roller equipped Gyratory Testing Machine for evaluation of asphalt mixtures containing aggregates from the same sources with varying amounts of crushed and natural sand aggregates (different blend proportions) to produce both identical gradations as well as different gradations. Analyses performed on the test results indicated overall excellent correlation between Gyratory shear (Gs) after 200 revolutions of densification and asphalt content (A/C), voids in mineral aggregates (VMA), and air void content (AV) at as-compacted densities. Similarly, statistical regression analyses indicated that asphalt, mineral filler, fine aggregate, and coarse aggregate contents have a significant effect on the Gs value for the different mixtures. As a result it is concluded that VMA and AV contents are not absolutely essential for mixture design or mixture evaluation. It is suggested that the GTM air roller procedure for testing of asphalt mixtures is probably all that is needed for evaluation of a mixture's resistance to plastic deformation.
Effect of Aggregate Size and Other Factors on Refusal Density of Asphalt Concrete by Vibratory Compaction
Authors: Shuler TS , Huber GA
Published: March 2009

The physical behavior of asphalt concrete is related to the volumetric characteristics of the mixture. A significant challenge facing asphalt pavement engineers is predicting the future density and air voids of asphalt paving mixtures after construction and during service. How rapidly changes in density and voids occur during service can be related to the ability of the pavement to withstand forces imposed from vehicles and the environment. Densification of asphalt concrete after construction and during trafficking varies between mixtures and is related to the method of laboratory compaction, design criteria, and construction technique. This study describes a procedure for quantifying compactibility of mixtures and suggests a procedure for considering densification rate as a criteria for describing optimum asphalt mixtures.

The so-called refusal density of six types of asphalt concrete mixtures was evaluated in this study as function of vibratory hammer compaction. Three aggregate gradings ranging from 1–1/2 inch to 3/8 inch (37.5 to 9.5 mm) maximum aggregate size were compacted in the laboratory using three models of portable vibratory compactors administered by two operators. The resulting factorial experiment was analyzed to determine effect on volumetric properties due to hammer, aggregate grading, asphalt content and operator.

Vibratory compaction was compared with Marshall, kneading, and gyratory compaction procedures to determine differences between each method and for each grading with respect to density and voids characteristics. A new procedure is outlined for using the vibratory compaction technique for development of a new asphalt concrete design method and for adapting the technique for determining the sensitivity of asphalt concrete mixtures to further densification under traffic.

Results of the study indicate that all three vibratory hammers evaluated compacted asphalt concrete to higher levels of density than achievable by conventional Marshall, Hveem or gyratory methods and therefore, should be capable of producing mixtures with higher density than could be obtained after trafficking. The implication of this efficiency during laboratory compaction is a design tool that could provide information regarding the potential for mixtures to reach a plastic condition in service as related to void content.
Factors Affecting the Durability of Sealants in Contact with the Finish Coating of EIF Systems
Authors: Kenney RJ , Piper RS
Published: March 2009

Failure of relatively new joint seals where the sealant was applied directly to the finish coat of the exterior insulation and finish system (EIFS) was first noted by the authors in 1975. During 1984, the failure of horizontal sealant joints in vertical surfaces on various projects with various types of sealants prompted an investigation into the cause or causes of joint seal failure.

From 1984 to 1991, a number of laboratory and field tests have been performed in order to correlate field and laboratory data. This paper discusses the effects of moisture accumulation within the wall system on the finish coat properties and the effect on the bond between various sealants and the finish coat when the properties of the finish coat are altered by elevated moisture levels.
Building Seals and Sealants for Parking Garage Decks in Hawaii
Authors: Yanoviak AC
Published: March 2009

Seven case studies of problems and solutions using building seals and sealants in parking garages and parking decks in Honolulu, Hawaii are described including: the Royal Iolani Condominium, the Parkside Towers, the Kapiolani Commercial Center, the Heritage House Condominium, the Discovery Bay Condominium, the Canterbury Place, and the Imperial Hawaii Resort Hotel.

An illustrated slide lecture was presented that exemplified serious water infiltration problems involving property damage and manufactured product application failures, architectural and structural design detailing problems, and defective specifications for combinations of various building materials. Examples of unsuccessful attempts at remedial repair solutions, and concern for maintenance and replacement factors are given. Various materials and design standards being used for building seals and sealants on waterproofed decks and walls, with considerations for concrete chemistry, reinforcement steel placement, construction and expansion joints, etc., are discussed.

Design challenges by architects, developers, and building owners for contractors and manufacturers of building seals and sealants on ten or twelve other projects in Honolulu, including the Hawaii State Capitol, Kukui Plaza, Queen Emma Apartments, Tamarind Park, Ilikai Hotel, Admiral Thomas Condominium, Hyatt Regency at Hemmeter Center in Waikiki, Century Square Plaza, and the Ala Moana Shopping Center are described with due consideration for standards development.
Modeling of the Thermomechanical Fatigue of 63Sn-37Pb Alloy
Authors: Hacke PL , Sprecher AF , Conrad H
Published: March 2009

The stress-strain hysteresis behavior of 63Sn-37Pb solder joints in thermomechanical cycling was determined experimentally with a bimetallic loading frame for temperature excursions between — 30 and 130°C applied in triangular waveform for periods of 12, 24, 48, and 300 min. A computer simulation based on a constitutive equation previously formulated for steady-state creep conditions yielded reasonable agreement between the predicted and measured hysteresis behavior. An approximately linear relationship was found between the drop in maximum load in a hysteresis cycle and the measured fatigue cracked area.
Growth of Surface Cracks During Large Elastic-Plastic Loading Cycles
Authors: McClung RC , Hudak SJ , Bartlett ML , FitzGerald JH
Published: March 2009

Thin Inconel 718 plates with deep elliptical surface flaws are subjected to large loading cycles under both load and displacement control. Closed-form estimates of the J-integral for surface flaws in finite thickness plates are derived with a modified reference stress method and compared with recent elastic-plastic finite element results. A J-resistance curve for the surface-cracked configuration is developed and compared with data from thick compact tension specimens. Special attention is given to the apparent relationship between ductile tearing and low-cycle fatigue crack growth mechanisms and rates.
Fracture Properties of Specially Heat-Treated ASTM A508 Class 2 Pressure Vessel Steel
Authors: Alexander DJ , Cheverton RD
Published: March 2009

The mechanical properties of ASTM A508 Class 2 pressure vessel steel quenched and tempered to simulate the effects of irradiation have been measured. The tensile, Charpy impact, fracture toughness, and crack arrest properties were measured as a function of temperature. The fracture toughness was measured using 1T, 2T, and 4T compact specimens. The maximum dimensions of the 4T specimens exceeded the test cylinder thickness, so compound specimens were successfully fabricated by electron-beam welding arms to the material. Compact crack arrest specimens were used to determine the arrest toughness. Two sizes of specimens were tested: 150 by 150 by 32 mm and 75 by 75 by 25 mm. The larger specimens used a brittle weld bead and notch as the crack starter. Two different notches (blunt and fatigue precracked) were used with the smaller specimens. The blunt notch was not successful, but the fatigue-precracked specimens provided valid data without the need for warm prestressing. The results from the small fatigue-precracked specimens were consistent with the data from the larger weld-embrittled specimens.
Cracked Strip Problem Subjected to a Nonsymmetric Transverse Loading by a Stamp
Authors: Yahşi OS , Demir Y
Published: March 2009

In this study, the problem of an infinite elastic strip that contains a crack perpendicular to its boundaries and subjected to a nonsymmetric transverse loading is considered. The problem is a coupled crack-contact problem in which the distribution of the transverse loads is not known and is dependent on the geometry of the crack as well as the stamp. The effect of friction that may exist at the punches is taken into consideration in formulating the problem by prescribing the tangential as well as the normal tractions on the boundaries.

The solution of the problem is given for two stamp geometries, namely, a rigid flat-ended stamp with sharp corners and a curved elastic stamp.

To solve the problem, the stress and displacement fields of the strip were obtained by using Fourier transforms and then crack solution was added. As a result, three singular integral equations were obtained.

These singular integral equations are solved for the discrete values of contact stresses at certain collocation points, and stress intensity factors are obtained and tabulated for various geometries and material combinations.
Environmentally Controlled Fracture of an Overstrained A723 Steel Thick-Wall Cylinder
Authors: Underwood JH , Olmstead VJ , Askew JC , Kapusta AA , Young GA
Published: March 2009

A through-wall, 1.7-m-long crack grew suddenly from an outer diameter (OD) notch in a 285-mm-OD A723 steel overstrained tube that was undergoing plating operations with no externally applied loads. A description is given of the fracture mechanics tests and analyses and the fractography that were performed to characterize the cracking. Key material, residual stress, and environment information are: 1200 MPa yield strength; 150 MPa √m fracture toughness; composition typical of air-melt A723 steel; tensile residual stress at the OD of about 600 MPa; and electro-polishing bath of sulfuric and phosphoric acids at 54°C.

The bolt-loaded test for threshold stress intensity factor for environmentally controlled cracking described by Wei and Novak was used here with two significant modifications. Some tests included only a notch with radius matching that of the tube, and a new expression for K in terms of crack-mouth displacement was developed and used. Scanning electron microscopy (SEM) fractography and energy dispersive X-ray spectra were used to identify cracking mechanisms.

Results of the investigation include: (a) a measured threshold of hydrogen stress cracking for the material/environment below 20 MPa √m, (b) da/dt versus K behavior typical of classic environmental control, (c) an improved K/v expression for the bolt-loaded specimen and associated criteria for determining plane strain test conditions in relation to the Irwin plastic zone.
Fatigue Lifetimes for Pressurized, Eroded, Cracked, Autofrettaged Thick Cylinders
Authors: Parker AP , Plant RCA , Becker AA
Published: March 2009

This paper summarizes Boundary Element Method Stress Intensity Factor solutions, obtained by the authors and presented elsewhere, for internally pressurized thick cylinders having a single longitudinal, semicircular erosion on the internal bore with radial straight-fronted and elliptical cracks emanating from the deepest point of the bore erosion.

A ratio of external to internal cylinder radii (R0/R1) of 2.0 is employed and a range of semicircular erosion depths varying from 0 to 40% of the wall thickness. Care is taken to determine accurate stress concentration factors for the various erosion depths in order to accurately quantify limiting values of stress intensity factor at very short crack lengths.

Employing a standard fatigue crack growth law, lifetime calculations are presented for cyclic pressurization of the bore. The results indicate that the presence of a modest semicircular erosion at the bore serves to reduce the fatigue lifetime by an order of magnitude. A similar reduction in lifetime results from the elimination of the autofrettage residual stress field.
Fatigue Crack Growth Analysis of Structures Exposed to Fluids with Oscillating Temperature Distributions
Authors: Chattopadhyay S
Published: March 2009

This investigation considers amplitudes and frequencies of the oscillating temperature distribution as parameters for crack propagation studies. The alternating stresses produced by the temperature distribution are used to determine the ranges of stress intensity factors for a particular crack geometry using the principles of linear elastic fracture mechanics. The crack growth is then studied using a crack growth law for the material relating the crack growth per cycle to the number of cycles.

The analysis predicts that the number of cycles required to drive a crack of a specified initial size is dependent on the frequency of temperature cycling. The model also predicts that as the frequency increases, larger amplitudes of temperature variation can be permitted for the same number of cycles to failure. A design curve relating the temperature amplitude with the number of cycles to failure (a specified crack length) is obtained for various frequencies of temperature oscillations.
Debonding Force of a Single Fiber from a Composite Body
Authors: Leu S-S , Hill JL
Published: March 2009

The force necessary to break the adhesive bond of a single fiber from a multilayer composite is investigated. An important application of this analysis is the determination of the force required to pull the wire-guided fiber from the wound spool of a missile as it deploys the control fiber in flight. Deformations of the pulled fiber include bending, stretching, and torsion. The equilibrium equations are similar to the equation that governs a beam on an elastic foundation except that the three equations are coupled. A closed-form solution to the equilibrium equations is obtained with the constants of integration evaluated by carefully applying the appropriate boundary conditions. Results obtained include the variation of debonding force with the pulling angle, the transition of the governing failure mode of the adhesive layers, and the stress distributions in the adhesive layers. Results obtained for a special case of the double-cantilever beam are in excellent agreement with results in the literature.
A Finite-Element Analysis of Nonlinear Behavior of the End-Loaded Split Laminate Specimen
Authors: Corleto CR , Hogan HA
Published: March 2009

A finite-element analysis has been developed to evaluate the J-integral for the end-loaded split laminate specimen (ELS) used to characterize Mode II delamination fracture toughness of composites. The analysis includes the use of nonlinear beam theory to evaluate the J-integral from typical output data obtained using nonlinear beam elements. The beam elements include large deflections and rotations, midplane straining, and the effect of shear deformations. Several composite laminates going from unidirectional to multidirectional layups have been studied. The path independence of the J-integral using this analysis has been verified except for paths very close to the crack tip where the complex state of stress that develops at the crack tip invalidates beam theory approximations. For all the layups studied, midplane straining from the development of large rotations shows no significant effect on J. Furthermore, J has been found to be independent of shear deformations even when shear deformations are no longer negligible in the load-deflection response of the ELS. The effect of limited inelasticity on J, as is typical of multidirectional layups, has also been studied. This analysis illustrates the feasibility of evaluating the J-integral from simplified finite-element analyses, where global quantities away from the complex state of stress at the crack tip are used instead of local stresses and strains near the crack tip.
Effects of Sample Size and Loading Rate on the Transition Behavior of a Ductile Iron (DI) Alloy
Authors: Salzbrenner R , Crenshaw TB
Published: March 2009

The measurement and understanding of the fracture toughness of ductile irons (DI) are critical to the analysis of nuclear transportation casks made from these alloys. Cask containment must be assured for all loading events from normal handling to accidents during which high loads can be delivered at elevated rates. Cask walls are commonly in the range of 20 to 50 cm thick (or greater) in order to provide requisite nuclear shielding, and this requires that associated mechanical constraint effects must be considered. At elevated temperatures (that is, in the vicinity of ambient), DI behaves in an elastic-plastic manner, even for large section sizes (thickness > 20 cm) and moderately high loading rates. However, as the temperature is lowered or the loading rate is increased, ferritic DI alloys exhibit a relatively sharp transition to linear elastic behavior, with a significant decrease in the fracture toughness.

The fracture toughness of a DI alloy has been measured using linear elastic and elastic-plastic experimental techniques. Measurements have been made as a function of temperature, loading rate, and section size. The loading rates span the range that a cask could experience during normal transport and handling, as well as accident events. Specifically, the stress intensity rate, K, was varied between 10-3 to > 10+5 MPa m1/2/s. The range in section size that was examined was restricted to moderate thicknesses (̃1 to ̃4 cm) because of the limitations of available hydraulic test frames. For static testing rates, it was found that increasing specimen thickness appears to shift the transition behavior to slightly higher temperatures. The effect of increased specimen thickness during elevated rate testing was more pronounced. As the thickness was increased from ̃1 to ̃2 cm, the fracture toughness was decreased by roughly 25% at 25°C, and 40% at -29°C (the fracture toughnesses of both thicknesses were the same at -50°C where fracture was essentially all cleavage). Initial fractographic results show that the amount of brittle cleavage (at initiation) was larger for the thicker specimens in the ductile-brittle transition region. The decrease in fracture toughness with increasing section size (in the transition region) occurred even though all specimens met the size criteria of the ASTM Test Method for JIc, A Measure of Fracture Toughness (E 813-87). Measurements also showed that the temperature range of the transition region for this DI alloy increased with increasing loading rate and extended up to room temperature. A consistent explanation for the measured behavior seems to be that increased constraint (from increased specimen thickness) can cause an increase in cleavage if the test temperature (for a specific loading rate) is close to the transition region. The extent of this effect has an obvious impact on the analysis of the fracture resistance of transportation containers.
Comparison of Short-Term and Long-Term Pullout Testing of Geogrid Reinforcements
Authors: Collin JG , Berg RR
Published: March 2009

Long-term, 1000 hour sustained loading, and quick, strain rate of 1 mm per minute, soil-geogrid pullout was investigated with a laboratory test program. Results of the long-term and quick tests are compared and variations discussed. Geogrids of singular and of composite material manufacture were investigated. The test program was too limited in scope to extract any specific conclusions regarding the geogrids tested. However, differential between quick and sustained test results were significant enough to conclude that additional testing and investigation is warranted.
Chemical Stability of Polyester Fibers and Geotextiles Without and Under Stress
Authors: Netravali AN , Krstic R , Crouse JL , Richmond LE
Published: March 2009

High tenacity industrial grade polyester fibers were aged up to three months, in various chemicals at different stress levels. The accelerated aging was done at temperatures up to 70°C, which is thought to be the maximum underground temperature for applications such as surface veneers for waste landfills. The chemicals used in the study include trichloroethylene, deionized water, sea water, and 2% solutions of sulfuric acid and sodium hydroxide. The stress values used were 0 MPa, 100 MPa, and 260 MPa. The fibers were tested for their mechanical and thermal properties as a function of aging.

The results suggest that there are no changes in the fiber strength and glass transition temperature (Tg) after aging in trichloroethylene, sea water, and deionized water under any stress level and test temperatures. However, there is a small increase in the melting temperature indicating the possibility of crystal growth, especially at 70°C, due to the annealing effect.

Significant degradation in fiber strength is seen after a week of aging in sulfuric acid solution (-1.1 pH) at room temperature and 40°C. Under the severe acidic conditions, at 70°C and higher stress levels, the fibers completely disintegrated after one week.

In the strong alkaline condition (-13.7 pH), strength decreases of 33% and more than 50% are seen under 0 and 100 MPa stress levels within the first week of aging in NaOH, at RT. All fibers, regardless of stress, did not survive one month in the highly alkaline environment.

These results suggest that 1) severe hydrolysis occurs in strong alkaline and acidic media 2) no hydrolysis occurs under more normal soil conditions (∼pH 7-8) at temperatures up to 70%C and 3) higher stress levels do not significantly affect the degradation process.
Effects of Layer Waviness on the Stresses and Failure in Hydrostatically Loaded Cylinders
Authors: Brown TL , Hyer MW
Published: March 2009

The influence of layer waviness on the stress state and failure pressure of thick cross-ply composite cylinders loaded by external hydrostatic pressure is studied. Layer waviness is idealized as a single isolated region of waviness in an otherwise perfect cylinder. The waviness occurs in only the circumferential direction and is assumed to extend indefinitely in the axial direction. Waviness is assumed to occur because particular circumferential layers experience local radial displacement during consolidation, resin richness and resin depletion occurring on either side of the locally displaced layers. Stresses are computed by using a finite element analysis which models the isolated region of waviness in the cylinder on a layer-by-layer basis. Some details of the model are discussed; the model accounting for a range of amplitudes of waviness, a range of cylinder radius-to-wall thickness ratios, and whether the isolated waviness is located near the inner radius or near the outer radius of the cylinder wall. The paper illustrates the behavior of the three primary stresses, namely interlaminar shear, interlaminar tension, and fiber-direction compression, all of which are important to failure. Pressure capacity is determined by applying the maximum stress failure criterion. It is shown that interlaminar shear, while absent in the perfect cylinder, can be responsible for a 50% reduction in pressure capacity relative to the wave-free perfect cylinder. Also it is shown that fiber-direction compressive stresses are increased by the presence of waviness, and that interlaminar normal tensile stresses caused by the waviness are potentially responsible for failure.
Resonating-Orthotropic-Cube Method for Elastic Constants
Authors: Heyliger P , Ledbetter H , Austin M
Published: March 2009

Following studies by Demarest (1969) and by Ohno (1976), we describe measurements and analysis that yield, from a single cube-shape specimen, in a single measurement, the complete set of anisotropic elastic-stiffness constants, the Cij. Experimentally, we place a cubic specimen between two piezoelectric transducers, which excite and detect the cube's macroscopic free-vibration (fundamental-mode) frequencies, up to 10 MHz. From the specimen's shape, size, and mass, and from the measured resonance-frequency spectrum, we analyze for the Cij within a given tolerance ϵi: λi(Cij)-λi¯=ϵi. (No sum on i.) Here ƛi relates to the measured resonance frequencies, and λi represents eigenvalues calculated by a Rayleigh-Ritz method using Legendre-polynomial approximating functions. Legendre-polynomial orthogonality ensures a diagonal mass matrix [m], which simplifies the resulting eigenvalue problem: ([k]-λ[m]){x}={0}. For materials with certain symmetries, the coefficient matrix [k] reduces to a block-diagonal matrix, which reduces computational effort and simplifies vibration-mode identification.
Fiber-Reinforced Composites: Models for Macroscopic Elastic Constants
Authors: Datta SK , Ledbetter HM
Published: March 2009

Considering uniaxial-fiber-reinforced composites, we review selected models for calculating macroscopic elastic constants from the constituent elastic constants (fiber and matrix) and the phase geometry. Especially, we focus on the transverse-isotropic case with five independent elastic-stiffness constants, Cij. Also, we focus on wave-scattering ensemble-average methods developed by Bose and Mal (1974) and by Datta and Ledbetter (1983, 1984). We compare the model results with measurements made by pulse-echo dynamic (MHz) methods. As examples, we consider B/Al and Gr/Mg; the latter fibers possess high elastic anisotropy.
Sample Coupling in Resonant Column Testing of Cemented Soils
Authors: Lovelady PL , Picornell M
Published: March 2009

Low-strain shear moduli of lightly cemented sand can be obtained by testing specimens in a resonant column. In the literature a variety of techniques have been suggested for coupling the sample to the base and cap of the device. These studies' results suggest that the shear modulus of cemented sand changes with confining pressure. In this study, the specimens were coupled to the end platens with epoxy which was allowed to harden before testing. The results indicate that the low strain shear modulus of lightly cemented sand is nearly independent of confining pressure for pressures up to 500 kPa. The difference in the effect of confining pressure on the shear modulus, in this and other studies, is attributed to the different coupling techniques used. The results illustrate the need for a rigid connection between the specimen and the end platens.
Interactive Processing of Complex Modulus Data
Authors: Fowler BL
Published: March 2009

A methodology for processing damping material complex modulus data and presenting it in a manner that is meaningful to the damping designer is discussed. Initial parameter values for characterization equations are derived. The use of a computer program for characterization of complex modulus data is described.
Void Formation and Helium Effects in 9Cr-1MoVNb and 12Cr-1MoVW Steels Irradiated in HFIR and FFTF at 400°C
Authors: Maziasz PJ , Klueh RL
Published: March 2009

Martensitic/ferritic 9Cr-1MoVNb and 12Cr-1MoVW steels doped with up to 2 wt% nickel have up to 450 appm helium after High Flux Isotope Reactor (HFIR) irradiation to ̃38 dpa, but only 5 appm helium after 47 dpa in Fast Flux Test Facility (FFTF). No fine helium bubbles and few or no larger voids were observable in any of these steels after FFTF irradiation at 407°C. By contrast, many voids were found in the undoped steels (30 to 90 appm helium) irradiated in HFIR at 400°C, while voids plus many more fine helium bubbles were found in the nickel doped steels (400 to 450 appm helium). Irradiation in both reactors at ̃400°C produced significant changes in the as-tempered lath/subgrain boundary, dislocation, and precipitation structures that were sensitive to alloy composition, including doping with nickel. However, for each specific alloy the irradiation-produced changes were exactly the same comparing samples irradiated in FFTF and HFIR. particularly the nickel-doped steels. Therefore, the increased void formation appears solely due to the increased helium generation found in HFIR. While the levels of void swelling are relatively low after 37 to 39 dpa in HFIR (0.1 to 0.4%), details of the microstructural evolution suggest that void nucleation is still progressing, and swelling could increase with dose. The effect of helium on void swelling remains a valid concern for fusion application that requires higher dose experiments.
Swelling Suppression in Phosphorus-Modified Fe-Cr-Ni Alloys During Neutron Irradiation
Authors: Lee EH , Packan NH
Published: March 2009

Phosphorus-containing austenitic alloys in the solution annealed condition were irradiated at 745 to 760 K (470 to 485°C) in the Fast Flux Test Facility (FFTF) reactor to doses ranging from 0.1 to 10 dpa. The alloys were variations on Fe-13Cr-15Ni-0.05P with respective additions of 0.8 silicon, 0.2 titanium, or 0.8 silicon plus 0.2 titanium; also included were low (0.01) and zero phosphorus compositions (all values in wt %). This alloy set was studied previously using heavy ion irradiations.

The reference ternary and the two phosphorus-only variations contained little precipitation and numerous voids and swelled rapidly, while the three variants containing phosphorus with silicon or titanium or both showed little or no void formation and profuse phosphide precipitation. These results indicate that phosphorus in solution alone does not have a major influence on void swelling, whereas fine-scale phosphide precipitation is quite effective at suppressing void formation. The possible contributing role of impurity oxygen to void formation is considered, but this role is found to be secondary to the principal mechanism restricting swelling, which is the effect of the dense precipitate microstructure. These precipitates foster profuse cavity nucleation that in turn dilutes the helium accumulation per site. The cavities together thereby require more total helium atoms (and more time) in order for individual cavities to surpass their critical size and number of gas atoms necessary for subsequent growth as voids.
Ion Bombardment Radiation Damage Studies of Fusion-Relevant Austenitic and Ferritic Alloys
Authors: Mazey DJ , Murphy SM , Walters GP , Hanks W , Bolster DEJ
Published: March 2009

Results are given of a transmission electron microscope (TEM) study of the damage structure of selected alloys following ion bombardment with 46 MeV nickel ions in the Harwell variable energy cyclotron (VEC) to simulate fusion reactor exposures up to 40 dpa (̃3 MW-year m-2) at temperatures from 475 to 650°C. The alloys were 316 L (UNS 31603), modified 316-Ti, 316-Nb, a ferritic alloy 1.4914, and the commercial alloy TENELON. The 316 L alloy is being considered for the Next European Torus (NET). At temperatures between 475 and 575°C swelling in the matrix and weld of 316 L was similar but at 625°C swelling in welds was ̃60% greater than in the 316 L matrix. The 316-Ti alloy showed only 2.5% swelling after 40 dpa at 625°C, but a maximum swelling of 10 to 14% was observed in the 316-Nb alloys. Swelling in TENELON was moderate up to 575°C but rose to 5% after 40 dpa at 625°C. Low swelling of 0.2% after 40 dpa was observed in the 1.4914 alloy. The results confirmed the superiority of the ferritic steel over the austenitic steels in respect of void-induced swelling.
Electron Irradiation-Induced Amorphization of Precipitates in Zircaloy-2
Authors: Motta AT , Olander DR , Machiels AJ
Published: March 2009

The crystalline-amorphous transformation of Zr2(Ni,Fe) precipitates in Zircaloy by electron irradiation has been studied in the high voltage electron microscope at temperatures ranging from 92 to 283 K and dose rates between 10-3 and 4 × 10-2 dpa/s. The dose-to-amorphization was found to increase exponentially with temperature and to decrease with increasing dose rate. The occurrence of the transformation was modeled by calculating the increase in free energy because of irradiation effects: accumulation of point defects and lattice disordering. The time-dependent diffusion equation with recombination was solved to find the interstitial and vacancy concentrations as functions of dose, dose rate, and temperature. Random recombination was the assumed disordering mechanism. The transformation was assumed to occur when the free energy increase of the crystalline phase became equal to the difference in free energy between the amorphous state and the unirradiated crystal. The dose-to-amor phization predicted by the model agreed well with experimental results for reasonable values of the fitting parameters.
Equivalent Electronic Circuits Computer Generated from Alternating-Current Impedance Data
Authors: Pye EL , Golestaneh K
Published: March 2009

A simple but powerful method is presented for the computer generation of equivalent circuits using CAE/CAD software. The effect is shown of various component values, of the relative separation of component values, and of the frequency range. A comparison is made of Nyquist plots for Voigt, Maxwell, and Ladder equivalent circuits.
Computer Simulation of Stress Corrosion Cracking Behavior of Reactor Pressure Vessel (RPV) Steels in Light Water Reactor (LWR) Environments in Slow Strain Rate Tests (SSRT)
Authors: Shoji T , Moriya S , Yoshida K
Published: March 2009

Based upon a slip dissolution model, crack initiation and growth behavior of stress corrosion cracking of reactor pressure vessel steels, in pressurized high temperature water, was simulated by FEM (finite element method), with a combination of nodal force release techniques, simulating the crack growth by dissolution.

Results obtained from the computer simulation for this materials/environment combination agree well with experiments in overall load/displacement curves of the tests and also can simulate crack initiation and propagation behavior. This computer simulation of slow strain rate ( SSR ) tests also focused on the significance of the multiple crack problems in SSR tests, particularly for smooth specimens, in relation to an evaluation of an actual crack tip strain rate. It was also found that crack growth rates, under such a multiple crack situation, can be uniquely plotted as a function of crack tip strain rates when evaluated correctly.
The Use of Computer Modeling in the Interpretation of Filming Inhibitor Mechanisms
Authors: Palus AF , Nienart CA
Published: March 2009

The computer has made the collection and interpretation of data easier. The advent of computer controlled instrumentation made it possible to easily acquire electrochemical impedance data; unfortunately the complex nature of the data made it difficult to interpret. One classical approach to interpretation is to hypothesize an equivalent circuit to model the electrochemical system. Since the equations and algorithms of electrical circuits are well defined, a computer program can do an excellent job of modeling these equivalent circuits. We will discuss how the use of a commercially available impedance modeling program can be used in the interpretation of real impedance data.

Cinnamaldehyde is known to act as an inhibitor to steel corrosion in hydrochloric acid. The mechanism for protection is assumed to be twofold. The chemisorption of trans-cinnamaldehyde (TCA) is usually proposed as the major contributor to inhibition. A secondary, but significant, contribution is caused by the polymerization of the TCA to form a film. Growcock and Lopp [ 1 ] have studied the nature of these two mechanisms. They showed through corrosion rate studies, organic analysis, NMR, FT-IR and GC/MS the nature and function of the organic film formed by TCA.

We have studied the film formation of TCA on 1018 steel in HCL solutions using electrochemical impedance spectroscopy. Experiments were run to try to distinguish the difference between the two major inhibition mechanisms. The impedance spectrum of an adsorbed TCA diffusion barrier should differ from the spectrum of either a polymer film or a combination polymer film and diffusion barrier. The Equivalent Circuit modeling program of Boukamp [15] was used to assist in interpretation.
Modeling Electron Transfer, Diffusional Effects, Passivation, and Ohmic Loss in Multi-Reaction Polarization Curves
Authors: Devereux OF , Yeum KS
Published: March 2009

A freely corroding metal may be represented as an electrode under the simultaneous influence of at least two electrochemical reactions, one anodic and one cathodic. If the corroding medium is mildly acidic, aerated water there are two cathodic reactions of significance, reduction of water and reduction of oxygen, while additional anodic reactions must be considered if the metal has multiple oxidation states or contains alloying ingredients or if its potential is sufficiently positive to oxidize water. The separate behavior of these reactions may be delineated by polarizing the electrode and measuring the current that passes as a function of the potential. To a good approximation these reactions may be regarded as independent. In this paper the current carried by a single electrode reaction at a given potential is expressed by a system of equations that incorporate rate control by electron transfer, diffusion, and passivation, and correct for ohmic loss in the electrolyte; the total current passed by the electrode and measurable in the external circuit is expressed as a simple algebraic sum of these values. Features of illustrative polarization curves (potential versus log current) are explained in the context of this model, and the technique is applied to two experimental systems, one entailing seven reactions with twenty-four parameters which were fit to the model via a regressive procedure.
Numerical Simulation of Impressed Current Cathodic Protection (ICPP) Systems Using Boundary Element Methods
Authors: De Giorgi VG , Thomas ED , Kaznoff AI
Published: March 2009

The numerical simulation of a prototypic ship and impressed current cathodic protection (ICCP) system to determine the required current for adequate cathodic protection is documented in this paper. The prototypic ship is modeled using a commercial boundary element code. The propellor assembly and rudder are included in the boundary element model as separate detached geometric features. Nonlinear polarization data are used to define the material response. Electrolyte static ( low flow ) conditions are examined. The current required for cathodic protection for a bare steel hull is compared with an estimated value based on material polarization data.
Some Observations in Fracture Toughness and Fatigue Testing with Chevron-Notched Specimens
Authors: Salem JA , Shannon JL , Jenkins MG
Published: March 2009

Chevron-notched specimens were used to test metallic and ceramic materials over a range of temperatures and testing conditions. The materials tested were M-50 bearing steel, alumina, silicon carbide, monolithic silicon nitride, and in situ toughened silicon nitride. Results were compared to measurements performed with compact-tension specimens, singleedge notched beam specimens, or single-edge precracked beam specimens.

Measured properties included fracture toughness, crack growth resistance, and fatigue crack growth rate. For materials with rising R-curves, the fracture toughness measured with chevron-notched specimens was dependent on specimen proportions and notch geometry, as related to the amount of crack extension to the measurement point. For materials with flat R-curves, the chevron-notch test is independent of notch geometry and specimen proportions.
Short Bar Chevron-Notch Fracture Toughness of Bone Cement
Authors: Bhambri SK , Gilbertson LN
Published: March 2009

Poly(methylmethacrylate) is used as a grouting agent in total joint arthroplasty. Fracture toughness of the relatively brittle bone cement is an important property determining the reliability and defect tolerance capability of the material. In the present study, fracture toughness of bone cement and commercial PMMA has been determined using a short bar chevron-notch test method. Chevron-notched short bar specimens were prepared with a notch molded-in during the polymerization process or by machining techniques. Specimen size and other test parameters were varied to determine variability of the results. In addition, parameters were also varied to simulate clinical practices.

A peak load test method following ASTM E 1304-89 was used to estimate fracture toughness. The load-displacement curves obtained were independent of the displacement rates within the recommended peak load time range. Wide variation of displacement rates had no effect on the fracture toughness values. No plasticity-induced effects on fracture toughness were evident in the slow rate regime up to a peak load time of 300 s for 12.7-mm-thick short bar specimens. The results of this study indicate that the ASTM Test Method E 1304-89 can be successfully used in determining fracture toughness of bone cements.
Material Modeling for Unidirectional Glass and Glass-Ceramic Matrix Composites with Progressive Matrix Damage
Authors: Yen C-F , Buesking KW
Published: March 2009

Material models have been developed for characterizing the nonlinear stress-strain response of unidirectional glass and glass-ceramic matrix composites associated with progressive transverse matrix cracks perpendicular to fibers and ultimate composite failure. The models utilize a combined micromechanical and statistical approach. A simple micromechanical model has been used to evaluate the fiber and matrix stresses in the presence of transverse matrix cracks, fiber-matrix debonding, and residual stresses. Utilizing the chain-of-bundles approach, statistical models for matrix failure and fiber failure have been introduced to relate the density of transverse matrix cracks to the applied composite stress and to compute the final composite strength, respectively. Procedures to determine the required statistical and mechanical material parameters from experimental data have been established. The material models that are developed are applied to a glass matrix composite (C/borosilicate) and a glass-ceramic matrix composite (SiC/LAS).
Evaluating Surface Treatment Effects on Interfacial Bond Strength Using Dynamic Mechanical Analysis
Authors: Edie DD , Kennedy JM , Cano RJ , Ross RA
Published: March 2009

Three series of torsional dynamic mechanical analysis (DMA) tests were conducted on unidirectional carbon/epoxy composites to determine differences in interfacial bond strength. For the first series, composites were manufactured with PAN-based and pitch-based carbon fibers. The fibers had a proprietary surface treatment. For the second series of tests, the composites were made with four grades of pitch-based carbon fibers. Two different methods of surface treatment were used on the fibers. As a comparison, short beam shear tests were conducted on the composites made with fibers which had different surface treatments. The final series of tests were conducted on composite samples made from one grade of pitch-based fibers with four different fiber volume fractions. All samples were made using the same matrix material. Dynamic mechanical analysis was able to clearly differentiate between the fiber/matrix bond strength of pitch-based and PAN-based fibers. The interlaminar shear strength correlated well with the DMA results, indicating that DMA can measure the effectiveness of various surface treatments. The dynamic mechanical loss modulus increased with increasing fiber volume fraction or total surface area.
Micromechanical Analysis of Fiber Fracture
Authors: Carman GP , Lesko JJ , Reifsnider KL
Published: March 2009

A closed-form analytical model is developed in this paper to study the perturbed stress field in a general unidirectional composite system containing fiber fractures. The model includes analysis of eccentrically oriented fibers and multiple fiber fractures with the use of an approximating geometry. The theory developed incorporates a functional dependence of stress/strain concentration on constituent material properties, fiber volume fraction, crack size, multiple fiber fracture, and fiber eccentricity. Utilizing a mechanics of materials approach with classic elasticity concepts, the approximate stress field is generated for each constituent region (e.g. fiber, matrix, and interphase). The analysis employs an annular ring of fibers to model the adjacent unbroken fibers and a novel fiber discount methodology to examine multiple fiber fractures. Analytical results of strain concentration are compared with direct experimental measurements to corroborate the model's depiction of the effect specific physical parameters (crack size and axial position) have on this quantity. Parametric studies are performed with variables such as fiber volume fraction, constituent stiffness properties, crack size, and eccentrically located fibers to investigate their significance on general trends.
Characterization of Composite Material's Dynamic Response Using Load/Stroke Frequency Response Measurement
Authors: Elahi M , Razvan A , Reifsnider KL
Published: March 2009

A new experimental technique was developed to characterize damage development in composite materials. The technique does not require interruption of the test. It utilizes the frequency response measurement of load/stroke signals to characterize fatigue damage in terms of parameters such as phase and gain. Test frame and frequency dependency of the method was investigated. Center-notch quasi-isotropic unidirectional specimens were fatigue cycled at various load levels. From the fatigue test results, it was found that gain is related to the total damage and that phase may be related to the rate of damage in the specimen. Results also indicated that the method was sensitive to the applied load level and the material systems. This technique might be able to overcome problems involved in fatigue damage characterization of unidirectional laminates during high-temperature testing of composites where extensive splitting and elevated temperatures limit the use of extensometers.