bluuebunny/crossref_metadata_2025 huggingface dataset:
A Simple Model to Simulate the Interlaminar Stresses Generated Near the Free Edge of a Composite Laminate
Authors: Conti P , De Paulis A
Published: December 2008

This paper relates an attempt to evaluate the interlaminar stresses that are generated within the interface between two layers near the free edge of angle-ply and cross-ply laminates. An approximate model based on simple polynomial formulations is proposed. The results obtained with this model are compared with numerical results available in the literature and with values obtained by an experimental program conducted on angle-ply glass/epoxy laminates.
A New Ply Model for Interlaminar Stress Analysis
Authors: Valisetty RR , Rehfield LW
Published: December 2008

An accurate estimate of interlaminar stresses is crucial to understanding as well as predicting many delamination-related failures in composite materials. A new model for ply-level sublaminate analysis is presented and applied. The homogeneous plate theory developed earlier by the authors is further refined, and the equations are reduced appropriately for the classical finite-width free-edge laminate elasticity problem and a related delamination crack growth problem. It is applied to the laminate on a ply-by-ply basis. This theory incorporates all the essential physical effects and appears to be an adequate model for predicting the behavior of individual layers in equilibrium. On the basis of the number of equations and boundary conditions required for the implementation of layer equilibrium, this theory also appears to be the simplest of its kind presented so far. The stress induced in the free-edge region of a (0,90,90,0) laminate in uniform extension and the energy release rates for the delamination between the −30° and 90° plies of a (±30,±30,90,90)s laminate are computed using the new analysis. The results are in excellent agreement with the existing numerical solutions. The new ply behavioral model appears to be very promising; it yields stresses and displacements that are statically and kinematically compatible at interlaminar surfaces.
Analysis of Interlaminar Stresses in Thick Composite Laminates With and Without Edge Delamination
Authors: Whitcomb JD , Raju IS
Published: December 2008

The effect of laminate thickness on the interlaminar stresses in rectangular quasi-isotropic laminates under uniform axial strain was studied. Laminates from 8-ply to infinitely thick were analyzed. Thick laminates were synthesized by stacking (45/0/−45/90) ply groups, rather than grouping like plies. Laminates with and without delaminations were studied.

In laminates without delaminations, the free-edge interlaminar normal stress distribution in the outer ply groups was insensitive to total laminate thickness. The interlaminar normal stress distribution for the interior ply groups was nearly the same as for an infinitely thick laminate. In contrast, the free-edge interlaminar shear stress distribution was nearly the same for inner and outer ply groups and was insensitive to laminate thickness. In laminates with delaminations, those delaminations near the top and bottom surfaces of a thick laminate have much larger total strain-energy-release rates (GT) and Mode I-to-total (GI/GT) ratios than delaminations deep in the interior. Therefore delaminations can be expected to grow more easily near the surfaces of a laminate than in the interior. This is consistent with experimental results reported in the literature. Also, near surface delaminations in thin laminates tend to have larger strain-energy release rates than corresponding near surface delaminations in thick laminates.
Delamination Growth in a Notched Graphite/Epoxy Laminate Under Compression Fatigue Loading
Authors: Mohlin T , Blom AF , Carlsson LA , Gustavsson AI
Published: December 2008

This paper is concerned with the propagation of delamination in a graphite/epoxy composite laminate with an unloaded circular hole subjected to compression fatigue loading. Experimental and theoretical aspects of the problem are investigated.

In the experimental phase, coupon specimens were fatigue loaded in pure compression. The tests were performed at different constant-load amplitudes in ambient and humid environments at room temperature.

To monitor delamination growth, the specimens were removed from the testing machine after certain numbers of load cycles and were nondestructively inspected using a tetrabromoethane (TBE)-enhanced X-ray technique. In this way a measure of the delamination shape and area as a function of applied load level and number of cycles was obtained. Fatigue damage in terms of modulus degradation was also monitored. In the case of specimens which suffered severe damage, the residual compression strength was measured.

A three-dimensional finite-element analysis was used in conjunction with the experimental results to characterize the delamination crack growth in dry specimens. Results of this analysis enabled a power-law relationship between the strain energy release rate and the crack growth rate to be established.
Fatigue Thresholds of Delamination Crack Growth in Orthotropic Graphite/Epoxy Laminates
Authors: Gustafson C-G , Jilkèn L , Gradin PA
Published: December 2008

During manufacturing of fiber composite structures, cracks of small sizes are introduced during layup and drilling, and in the making of cutouts. The component itself sometimes has sites that are prone to delaminations, such as the junction of the web and the flange of a beam. Under cyclic loading these interlaminar defects can grow.

One key for designing fiber composite structures that will not exhibit delamination crack growth is to make sure that the actual or anticipated interlaminar flaws produce strain-energy release rates below the fatigue threshold value Gth for the actual laminate and actual combination of opening mode and shearing mode energy release rates, GI and GII, respectively.

Four types of delamination crack growth experiments were carried out to experimentally determine the critical curve inside which no cyclic crack growth will take place in the GI and GII planes. Pure Mode I crack growth and near pure forward shearing mode crack growth experiments were performed, as were experiments that possess a combination of the first two modes of crack growth. The laminates used in this investigation were (0/90), T300/914C layups. In the experimental work a unique automatic load reduction system was used, allowing for the determination of the threshold state with a constant stress ratio maintained during the load reduction.

For all but one case, GIth and GIIth were determined numerically, using a two-dimensional finite-element method program, by employing a relaxation procedure. Finally, the results from the experiments are presented in the GIth and GIIth planes.
Analysis of Local Delaminations and Their Influence on Composite Laminate Behavior
Authors: O'Brien TK
Published: December 2008

An equation was derived for the strain-energy release rate, G, associated with local delamination growth from a matrix ply crack. The critical Gc for edge delamination onset in [±25/902]s graphite/epoxy laminates was measured and used in this equation to predict local delamination onset strains in [±25/90n]s, where n = 4, 6, 8 laminates. A simple technique for predicting strain concentrations in the primary load bearing plies near local delaminations was developed. These strain concentrations were responsible for reduced laminate nominal failure strains in laminates containing local delaminations. The influences of edge delamination and matrix crack tip delamination on laminate stiffness and strength were compared.
Role of Delamination and Damage Development on the Strength of Thick Notched Laminates
Authors: Harris CE , Morris DH
Published: December 2008

A large, comprehensive program is being conducted at Virginia Tech to study the effect of laminate thickness on the fracture strength of notched laminated composites. Part of this program has been the study of the characteristics and development of subcritical crack-tip damage prior to failure. The study has concentrated on the centercracked tension specimen geometry. Subcritical crack-tip damage has been studied using enhanced X-ray radiography and the laminate deply technique.

This paper examines the role that delamination plays in affecting the fracture of [0/±45/90]ns and [0/±45]ns laminates at various values of n. The study has found that delaminations do occur in thin laminates (n = 1) and affect the strength of the laminate. However, in thick laminates such as [0/±45/90]15s and [0/±45]20s, there is sufficient constraint to prevent delaminations from occurring in the interior region of the specimen. The final fracture surface is uniform in the interior and self-similar (collinear with the original starter notch), with “shear-lip” type damage in the form of delaminations and matrix cracking in the first several plies at the surface. These differences in the type of fracture of the thin and thick laminates greatly affect the fracture strength.
Quantification of the “Tapping” Technique for the Detection of Edge Defects in Laminated Plates
Authors: Kenner VH , Staab GH , Jing H-S
Published: December 2008

A miniature piezoelectric transducer has been used to sense both details of the loading history and features of the ringing response in tapping tests conducted on bonded aluminum and graphite/epoxy plates containing artificial flaws. Either the loading or the ringing phase of the resulting output records exhibits significant differences for loading occurring over, as opposed to off, the flaw. When the data are examined in the frequency domain, it is found that major details are beyond the audible range of frequencies.
Borehole Shear Tests in a Shallow Marine Environment
Authors: Handy RL , Schmertmann JH , Lutenegger AJ
Published: December 2008

A wireline adaptation of the borehole shear test (BST) with high-pressure shear plates was one of several in-situ test methods selected to measure strength of over-consolidated phosphatic clays and lime rock at proposed pier locations for the replacement Sunshine Skyway Bridge, Tampa Bay, FL. Although the site's soils ordinarily would be judged too hard for stage BSTs, an on-site decision was made to try it in lieu of single-point testing to save time. Of 18 stage tests attempted in very hard clay, 10 gave satisfactory failure envelopes, 5 gave envelopes indicative of residual shear strength, and 3 gave invalid envelopes attributed to progressive seating of the shear plates. Stage tests in the harder rocks and shell were less successful. The average cohesion from the 10 satisfactory stage tests in the overconsolidated clays was 91 kPa (1900 psf) and the average friction angle φ = 25.7°. The BST data proved useful for converting a large number of undrained penetration tests into the effective stress strength parameters needed for design. The additional use of special BSTs using smooth plates also permitted site-specific shear strength corrections for soil against steel piles and casings.
Determination of Effective Stress-Based Shear Strength Parameters from Static and Cyclic Triaxial Tests
Authors: Skotheim A , Janbu N , Senneset K
Published: December 2008

This paper describes triaxial testing procedures and corresponding methods of interpretation to find relevant effective stress-based soil parameters as input to stability analyses of marine structures. The main emphasis is laid on interpretation of static and cyclic triaxial test results with respect to shear strength parameters and pore-pressure characteristics. Examples of tests on marine soils are presented, and resulting design profiles are applied to investigate the foundation stability of a gravity platform during a 100-year design storm.
Effects of Sustained Shear Stresses on the Cyclic Degradation of Clay
Authors: Goulois AM , Whitman RV , Hoeg K
Published: December 2008

The soils surrounding any of the anchorage piles of a tension leg platform (TLP) will be subjected to average (sustained) shear stresses τave of significant magnitude, in addition to the cyclic shear stresses τc associated with fluctuations of environmental loading. In order to investigate their combined effect on the displacement behavior of such a foundation, ten cyclic direct simple shear (DSS) tests were run with constant values of both τave and τc, as were two tests with variable τc. All the conditions of the 1975 Norwegian Geotechnical Institute (NGI) program (Andersen 1976 and Andersen et al, 1980) were followed (Plastic Drammen Clay, Geonor DSS device, and so forth) in order to capitalize upon, and increase, that data base.

The results of the investigation are presented in the form of “three-dimensional strain contour diagrams,” which improve our ability to interpolate, and even extrapolate, the data over a wide range of stress conditions. Furthermore, a procedure is proposed that permits a satisfactory estimation of the clay behavior under the variable cyclic loading imposed.
Integrated Testing and Properties of a Gulf of Mexico Clay
Authors: Saada AS , Macky TA
Published: December 2008

In testing undisturbed soil samples taken in a hostile environment one is often faced with the problem of having to obtain many properties from a limited number of specimens. This difficulty can be partly overcome by designing compatible equipment, so that a sample can be tested in a nondestructive way at very small strains in one type of machine, then transferred to another one and subjected to larger static and dynamic stresses and strains. In this investigation, the specimens were first placed under fast cyclic loading axially and torsionally in the resonant column cell. Then they were transferred with their caps in place to another cell where they were subjected to slower cyclic loading under increasingly larger stress amplitudes. The results of the tests that were conducted on a Gulf of Mexico clay are given and analyzed. Shear moduli, damping ratios, and frequency responses obtained in a resonant column at very small strains are examined together with ratios obtained at large strains to give a complete picture of the dynamic behavior of this clay.

Data discussed in the light of the Ramberg-Osgood-Masing criterion show that such a criterion overestimates the damping and that it is impossible to describe the behavior of this clay over the whole spectrum of strain with just one set of parameters. It is recommended that parameters in the zone of interest always be obtained.
Response of Silts to Wave Loads: Experimental Study
Authors: Clukey EC , Kulhawy FH , Liu PL-F
Published: December 2008

The response of a nonplastic silt subjected to water waves was investigated in a laboratory wave tank facility. The deposit was created by slurrying the silt into a sediment bay, and pore-water pressure transducers were placed at various depths within the deposit to measure the dynamic response under wave loading.

Tests were run under varying hydrodynamic conditions. At higher wave heights, the pore-water pressures rose continuously and resulted in liquefaction of the silt. Intermediate wave heights caused observable deformations, while low wave heights generated positive pore-water pressures that appeared to reach steady state nonfailure conditions in a few minutes.

The results from the testing suggest that normally consolidated silty marine sediments at low overburden stresses can liquefy at substantially lower cyclic stress ratios than currently available data for sands would indicate. This observation suggests further that utilization of data for sands could lead to unrealistic design practices in offshore regions of silty material.
Measurement of Poro-Elastic Properties of Marine Soils
Authors: Edil TB , Toha FX
Published: December 2008

The objective of this paper is to describe a new technique for measurement of the poro-elasticity of marine sediments in the laboratory. This technique enables one to determine the composite poro-elasticity factor α′ in one test setup as a function of controlling environmental factors such as stress state and load frequency. α′ includes shear modulus, Poisson's ratio, and hydraulic conductivity of the soil and compressibility and unit weight of the fluid along with frequency of wave loading and a characteristic dimension. The determination of α′ is based on the measurement of pore pressure at different depths in a confined cylindrical specimen. The theoretical basis of the test procedure, the method of analysis of the test results, and the appropriate test boundary conditions for different soils are presented. The results of tests performed on a nonplastic silt soil indicate that the proposed technique provides an efficient means of determining poro-elasticity of marine soils.
The Use of the Point Load Index in Weak Carbonate Rocks
Authors: Abbs AF
Published: December 2008

There has been increasing use of the point load index as a measure of rock strength since its introduction in 1972. The test results have been correlated to in the uniaxial compressive strength σf of the rock. The correlations between the rates of point load index Is and the uniaxial strength σf for conventional strong rocks are σf/Is = 16 to 24. The small size of the equipment and the simplicity of the test have led to its use on site on many offshore projects.

Recent experience with weak porous carbonate rocks from offshore areas of the Middle East have proven that the relationship for these materials is much closer to σf/Is = 3.7 with actual field correlations varying from 2.7 to 8.8. Moreover, statistical studies of a large number of point load test data show that this test is poorly suited to weak carbonate rocks.
Laboratory and In-Situ Strength Testing of Marine Soils in Iran and Indonesia
Authors: Attwooll WJ , Fujioka MR , Kittridge JC
Published: December 2008

Major geotechnical investigations were conducted for a proposed shipyard at Bandar Abbas, Iran, and a silo complex and dock at Tanjong Priok, Jakarta, Indonesia. In Iran, drilling and sampling were conducted from a drill ship and a jackup platform. The drilling in Indonesia was from an existing jetty and on onshore reclaimed marine areas. The value of both in-situ and laboratory strength testing was demonstrated at these geologically diverse sites. The soils at the Iranian site were generally overconsolidated, whereas at the Indonesian site the geologic history indicated the soils to be normally consolidated near the surface and becoming progressively underconsolidated with depth. At both sites, in-situ tests indicated higher shear strength then did laboratory tests on relatively undisturbed soil samples. The shear strength values used in design were based on the laboratory strength data, with the in-situ data allowing an evaluation of the relative conservatism of the selected relationships.
The Deformation Properties of Warm Permafrost
Authors: Shields DH , Domaschuk L , Man C-S , Kenyon RM
Published: December 2008

Six pressuremeter tests and one multistage triaxial creep test were conducted on a prepared frozen sand at −2.5 and −3°C, respectively. The pressuremeter study suggested that the model of incompressible power-law fluid, which is sometimes used in the numerical modelling of frozen-ground geotechnical problems, would not provide a suitable “simplified constitutive relation” on which we could base the design of a new standard pressurementer test for discerning long-term creep properties of warm permafrost. The multistage triaxial creep test showed a correlation between the decreasing or increasing in volume of the specimen and the attenuating or nonattenuating character of its axial creep behavior.
Comparison of Analytical Methods for the Determination of Total and Free Cyanide in Solid Waste
Authors: Barsotti LR , Palmer TA
Published: December 2008

Historically, standard reflux distillation methods have been used to determine the total cyanide in aqueous systems. This paper compares such a method with an automated total cyanide method and demonstrates good recovery and precision by both methods. The automated method has the advantages of speed and convenience, as well as being less labor-intensive.

Free cyanide, identified as the sum of hydrocyanic acid and cyanide ion in aqueous solution, is determined by a microdiffusion and a modified Roberts-Jackson method. A comparison of results obtained by both methods showed free cyanide was only about 2% of the total cyanide in an aqueous sample. Total cyanide methods are useful for screening the cyanide content of samples, but free cyanide methods increase the information available and improve the understanding about the kinds of cyanide compounds in a sample. Even greater selectivity of analytical methods for cyanide compounds in waste is desirable and a challenge to analytical chemists.
A Rapid Method for Determination of Total Organic Halogens in Industrial Waste Samples
Authors: Ziegler WJ , Schlauch R
Published: December 2008

A rapid method for determining total organic halogens (TOX) in industrial waste samples has been developed and validated. Total organic halogens is an indicator parameter specified by the U.S. Environmental Protection Agency (EPA) to be of environmental significance as representative of toxic organic halogenated compounds. The validation study included 36 compounds representing all halogenated organic classes on the EPA priority pollutant list. The recovery data indicate that the method is quantitative for all halogenated organic classes with a detection limit of 3.5 ppm (micrograms per gram) as inorganic chloride [approximately 6.5 ppm polychlorinated biphenyls (PCBs)]. The analysis can be performed within 20 min and can be used to screen hazardous waste samples for PCBs at the 50-ppm enforcement limit of the Toxic Substances Control Act.
Laboratory Evaluation of Test Procedures for Use in the RCRA Hazardous Waste Ignitability Characteristic
Authors: Michael LC , Perritt RL , Pellizzari ED , Richardson F
Published: December 2008

The purpose of this research project was to conduct a single-laboratory evaluation of three methods to determine and characterize the potential hazard posed by flammable materials disposed in landfills. The test procedures—(1) radiant heat ignition, (2) linear flame propagation and (3) extinguishability with water tests—were conducted in six replicates on 26 actual and simulated wastes, including three reference standards. Precision of the replicate analyses was approximately 30% and was consistent between actual samples and reference standards. Evaluation of the data from the three tests revealed a significant correlation between the radiant heat and flame propagation tests and hence a possible redundancy based on the samples analyzed. The data show that the ignitability of a waste is directly related to the rate of flame propagation and the volume of water necessary to extinguish the flame, and is inversely related to the time to ignition under a radiant heat source. These relationships were combined into an “ignitability factor” for assessing the overall ignition tendency for the samples tested.
Nontarget Compound Analysis of Hazardous Waste and Environmental Extracts by Combined FSCC/GC/FT-IR and FSCC/GC/MS
Authors: Gurka DF , Hiatt MH , Titus RL
Published: December 2008

Complex environmental wastes have been analyzed by fused silica capillary column gas chromatography/mass spectrometry (FSCC/GC/MS) and fused silica capillary column gas chromatography/Fourier transform infrared spectrometry (FSCC/GC/FT-IR). The two techniques used in conjunction are capable of determining or confirming the compound class of at least two thirds of all extract analytes. Detailed analytical results are presented that demonstrate that the relative strengths and shortcomings of each method are different and thus using both in conjunction leads to the identification of a far greater number of analytes than the use of either one alone. It is postulated that the present cost of using both techniques in conjunction can be substantially lowered by the direct interfacing of both spectrometers and the development of suitable computer software.
A Toxicity Reduction Test System to Assist in Predicting Land Treatability of Hazardous Organic Wastes
Authors: Matthews JE , Bulich AA
Published: December 2008

Migration of toxic organics contained in the water-soluble fraction (WSF) of land-applied hazardous wastes poses the most serious threat to groundwater resources. Wastes containing toxic organics that are potentially leachable must be applied to the land at a rate that will allow attenuation of such constituents before their migration from the treatment zone can occur.

A toxicity reduction (TR) test system is being proposed that will serve to determine whether and to what extent attenuation of WSF organic constituents, including both parent compounds and intermediate transformation products, will occur in a well-managed land treatment system.

The test system employs reduction of acute toxicity exerted by WSF organics over time as the measurement criteria. Four sample sets of selected waste-soil combinations are prepared in duplicate for extraction with deionized water (DW) at 14-day intervals during a 42-day experimental period. Acute toxicity of each DW extract is determined by using a bacterial bioluminescence assay. Dose-response curves for each loading rate and subsequent time interval are compared with those of previous sample sets. The waste is predicted to be a candidate for land treatment if a significant reduction of acute toxicity exists during the experiment period at any of the loading rates tested. The maximum acceptable initial loading rate (MAIL) for waste application is predicted from these data. The predicted MAIL rate is the highest rate tested in which toxicity reduction for the waste-soil DW extract progresses steadily during the experimental period with the Day-42 EC50 approaching or exceeding 100 percent. (The EC50 is defined as the effective concentration of the DW extract that causes a 50% decrease in bacterial light output.) The higher the EC50 the lower the toxic effect; therefore, a 42-day EC50 approaching 100% signifies toxicity reduction in a waste-soil DW extract.

The TR procedure currently is being used by the EPA's Hazardous Waste Land Treatment Research Program to assist in evaluating land treatability potential for a variety of organic hazardous wastes. The most extensive use of the procedure to date has involved evaluation of land treatability for oily wastes from different sources within a refinery: i.e., lagoon bottom sludge, API separator sludge, slop oil emulsion solids, and dissolved air flotation unit skimmings. Additional evaluation tests have been conducted by using wastes from the wood preserving and paint industries. Results from these evaluation tests indicate the potential usefulness of the TR procedure as one of the initial tests conducted in a laboratory screening test sequence for predicting the land treatability potential of organic hazardous wastes.
U.S. EPA Program in Hazardous Waste Landfill Research
Authors: Schomaker NB
Published: December 2008

The U.S. Environmental Protection Agency's hazardous waste land disposal research program is collecting data necessary to support implementation of disposal guidelines mandated by the Resource Conservation and Recovery Act of 1976 (RCRA—PL 94-580). This program relating to the categorical areas of landfills, surface impoundments, and underground mines encompasses state-of-the-art documents, laboratory analysis, economic assessment, bench and pilot studies, and full-scale field verification studies. Over the next five years the research will be reported as Technical Resource Documents in support of the RCRA Guidance Documents. These documents will be used to provide guidance for conducting the review and evaluation of land disposal permit applications. This paper will present an overview of this program and will report the current status of work in the areas of landfills, surface impoundments, underground mines, and dioxin engineering.
Spatial Variation of Characteristics in the Zone of Incorporation at an Industrial Waste Land Treatment Site
Authors: Loehr RC , Martin JH , Neuhauser EF
Published: December 2008

The spatial variation in the characteristics of the zone of incorporation (ZOI) at an industrial waste land treatment site can be significant even when efforts are taken to achieve uniform distribution and incorporation. A single grab sample can be inappropriate for determining average ZOI characteristics.

The results of this study provide guidance in determining the number of samples necessary to provide reliable estimates of ZOI characteristics. The spatial variation at land treatment sites is a function of site-specific factors such as soil characteristics and methods of waste application and incorporation. A determination of specific site spatial variation is recommended as a prerequisite for developing an appropriate sampling program at land treatment sites.
Diagnostic Test Burns and Considerations for Selecting Hazardous Waste Incineration Systems
Authors: Doucet LG
Published: December 2008

It is difficult to procure hazardous waste incineration systems that will meet demanding performance and regulatory requirements and still be cost-effective. Test burns have proven to be of great value in this regard. These consist of burning representative waste samples under controlled conditions to observe and measure reactions. Test burn data are useful for evaluating technologies and designing systems and equipment. Despite the many benefits, test burns are not frequently used. There are difficulties associated with conducting test burns, and very little has been publicized concerning test burn procedures, performance, and applications. Standards and guidelines are needed for test burns, possibly through a technical organization such as ASTM.
Development of the Volatile Organic Sampling Train for Use in Determining Incinerator Efficiency
Authors: Johnson LD
Published: December 2008

Development and field application are described for the volatile organic sampling train (VOST) for testing incinerator efficiency. The concepts behind the VOST, several stages in its development, and the current status of this technology are discussed. Early experience indicates that the VOST works well in the field and yields good results when used with adequate care and precautions.
A New Solution for the Resistance of Single Piles to Lateral Loading
Authors: Pyke R , Beikae M
Published: December 2008

A new analytical solution for the resistance of a horizontal slice through a pile to lateral loading is presented. The solution assumes that a pile is surrounded by an infinite elastic medium, but it allows for the tendency of this medium to separate from the back of the pile. Procedures for determining Young's modulus for various soils are given and comparisons of the overall results are made with previously published results.
Lateral-Load Tests on 25.4-mm (1-in.) Diameter Piles in Very Soft Clay in Side-by-Side and In-Line Groups
Authors: Cox WR , Dixon DA , Murphy BS
Published: December 2008

Studies were made to investigate efficiencies of pile groups under lateral loading. The loading was in one direction at slow displacement rates approaching static conditions. The test piles were 25.4-mm (1-in.) diameter tubes open-ended, with penetrations of two, four, six, or eight diameters. Tests were made on single piles and on three- and five-pile groups with clear spacings of 0.5, 1, 2, 3, and 5 diameters in side-by-side or in-line arrangements. The tests were run in a very soft clay with a moisture content of 59% and a shear strength of 2 kPa (42 psf).

Summaries are given of efficiencies of 20 combinations of pile numbers, penetrations, arrangements, and clear spacings. Efficiencies are given for individual piles in a pile group as well as for the entire group. Distances from the soil surface to the load resultant on individual piles and to the load resultant on the total group are also given.
Lateral-Load Tests on Drilled Pier Foundations for Solar Plant Heliostats
Authors: Bhushan K , Askari S
Published: December 2008

The first commercial-sized solar generating station in the United States, the 10-MW Solar Pilot Plant near Daggett, Calif., required 1818 sun-tracking mirrors (heliostats). To ensure accurate focusing of the mirrors on the central receiving tower, stringent wind load rotation criteria were specified for the top of the heliostat foundation. Soils at the site are medium dense to very dense sands and gravelly sands. Because little data were available to predict lateral deflections of drilled piers under low-level cyclic loads, a full-scale load test program was undertaken to obtain the necessary soil-resistance pier-deflection parameters. Piers with a diameter of 0.91 m (3 ft) and length of 5.5 m (18 ft) were tested under cyclic loads of up to 23.0 kN (5.16 kips) applied at a height of 5.43 m (17.8 ft). Test results indicated lateral movements of less than 0.61 mm (0.024 in.) under maximum loading. A design based on site-specific soil-pier parameters resulted in about a 40% reduction in pier length and significant cost savings when compared to the original design based on existing methods.
Suggested Procedure for Conducting Dynamic Lateral-Load Tests on Piles
Authors: Gle DR , Woods RD
Published: December 2008

There are several analytical procedures available to predict the soil-pile interaction parameters required for the analysis of a pile-supported foundation subjected to vibratory forces. A procedure for performing a dynamic lateral field test on a single pile is presented. Results of this test are used to verify the adequacy of the assumptions made for the analytic solution and to judge the appropriateness of the soil-pile interaction parameters.

Dynamic lateral-load tests were conducted on eleven steel-pipe piles at three sites in southeastern Michigan. The piles were 324 and 356 mm (12.75 and 14 in.) in diameter, had lengths from 15 to 49 m (50 to 160 ft) long, and were embedded in both cohesive and cohesionless soils. The procedure consisted of attaching a steel-plate mass, vibratory oscillator, and vibration monitoring instrumentation to the head of each pile. The oscillator was then used to drive the soil-pile-mass system at selected force levels through frequencies from 5 to 55 Hz. The dynamic response was recorded on a strip-chart recorder for later evaluation. The data are presented in figures showing frequency versus response amplitude for each oscillator force level.

The soil-pile-mass system was also set into free vibration using the plucking technique. Results of the steady-state vibration testing are compared with the plucking test results on the same pile.

Conventional soil boring and testing methods were used to determine the subsurface soil profile and static soil properties. Dynamic soil properties adjacent to the tested piles were determined using the seismic cross hole and SH refraction (horizontal polarization of the shear wave) techniques.

Because of the way piles are inserted into the soil, the assumed boundary conditions between the soil and pile used in the analytical solutions seldom match the field conditions. This dynamic testing procedure enables the geotechnical engineer to make a judgment as to the adequacy of the assumptions in the analytical model and to make suitable corrections to match the field-observed results.
Fractography of Slow Fracture in Glass
Authors: Michalske TA
Published: December 2008

Slow fracture in soda-lime silica glass produces fracture surface markings associated with (1) a limit for stress corrosion crack growth, (2) plateau crack growth in humid environments, and (3) dynamic effects of liquids. For each case, the associated fracture surface marking is described and its interpretation reviewed. Discussion of each marking demonstrates the usefulness of fractography in solving problems of failure analysis as well as understanding slow fracture in glass.
Chemical Analysis of Fracture Surfaces
Authors: Pantano CG , Kelso JF
Published: December 2008

The applicability of various instrumental techniques for chemical analysis of fracture surfaces is reviewed. It is shown that methods which possess both a high spatial and a high in-depth resolution are usually required for analyzing structural heterogeneities on the fracture surface. When the features of interest have submicron dimensions, scanning Auger microanalysis (SAM) is most applicable, whereas features whose dimensions exceed 1 to 2 µm may be more easily characterized with scanning electron microscopy and energy dispersive X-ray analysis (SEM-EDXA). Chemical analysis of fracture surfaces can also be used to investigate the atomistic mechanisms of crack propagation; this is of particular benefit when chemically-assisted crack growth is involved. In this case, a method with exceptional in-depth resolution is required to measure the composition of reaction products and modified surface layers in the fracture plane. In this regard, the unique capabilities of ion-scattering spectroscopy (ISS) and ion microscopy are also discussed.
Some New Fractographic Features in the Fatigue of High-Strength Aerospace Alloys
Authors: Cina B , Eldror I , Kaatz T
Published: December 2008

The object of this research was to further a systematic fractographic study of fatigue in aerospace materials to facilitate failure investigations of actual components. Smooth and notched laboratory specimens were fatigue tested in pulsating tension and in alternating stress at a frequency of 1 to 2 Hz and at stresses that gave failure in 103 to 105 cycles. Fractures were examined by stereoscopic and scanning electron microscopes.

A ridge structure that had been previously observed in aluminum alloys that emanates from fatigue origins but precedes the formation of striations was observed in ultra-high-strength steels. The implications of such ridges in the mechanism of fatigue cracking are discussed. Not all the steels studied showed fatigue striations, and failure mechanisms not specific to fatigue were frequently observed.

Such nonconformity of fractographic features increased with the tensile strength of the steels. Secondary cracking was sometimes found to be a more reliable method of identifying fatigue failure in some of these steels. Intergranular cracking at prior austenite grain boundaries was also frequently observed, although its formation appeared, on occasion, to be related to the attainment of a minimum level of stress intensity. Hydrogen from the environment also probably played a role in such intergranular cracking, as indicated by distinct hairlines on the fracture surface. Intergranular crack surfaces also sometimes showed unexpected crystallographic features.

For the aluminum alloys, further quantitative relationships have been established between the total number of striations in the development of the crack and the number of fatigue cycles in the entire fatigue test. This enables the fatigue stress to be estimated where unknown.

Counting striations in the steels was found to be very difficult and unreliable. However, trends in 4340 steel were found to be akin to those in aluminum alloys. Ridge formation in the aluminum alloys did not appear to be related to specimen geometry.
Evaluation of Ferritic Alloy Fe-2¼Cr-1Mo After Neutron Irradiation: Irradiation Creep and Swelling
Authors: Gelles DS , Puigh RJ
Published: December 2008

Irradiation creep and swelling measurements are reported for Fe-2¼Cr-1Mo after irradiation by fast neutrons over the temperature range 390 to 560°C. Diameter change measurements on thin-walled pressurized tubes in a bainitic condition and density change measurements on rods in a nonstandard condition were made following irradiation in the Experimental Breeder Reactor II. The irradiation creep specimens were irradiated to a fluence of 5.7 × 1022 neutrons (n)/cm2 (E > 0.1 MeV) or 30 displacements per atom (dpa) and the swelling specimens were irradiated to a peak fluence of 2.4 × 1023 n/cm2 or 115 dpa. These results have been used as a basis to establish in-reactor creep and swelling correlations for 2¼Cr-1Mo in a bainitic condition. The correlations predict moderate swelling and moderate irradiation enhanced creep at 390°C. The in-reactor creep at 570°C indicates that thermal creep mechanisms become important at this irradiation temperature.
Transmission Electron Microscope Studies and Microhardness Testing of Irradiated Ferritic Steels
Authors: Hulett DK , Jesser WA
Published: December 2008

Model alloys of ferritic steels were irradiated to a low fluence of 1 × 1023 neutrons (n)/m2 at temperatures 544, 580, and 599 K. These alloys were pure iron, Fe-0.1C, Fe-0.1C-0.15Cu, and Fe-0.1C-0.28Cu. Specific attention was given to the copper-containing alloys in correlating microstructural changes as observed in the transmission electron microscope (TEM) with hardness changes measured using Vickers microhardness tests. The post-irradiation microstructure did not exhibit characteristic radiation damage; no voids, bubbles, or dislocation loops were observed. The hardness changes were related to the semi-quantitatively obtained amount of copper not bound in TEM-observable copper-containing precipitates. The copper unaccounted for in observed precipitates was shown to be the primary influence on hardness changes.
Swelling of 20% Cold-Worked Type 316 Stainless Steel Fuel Pin Cladding and Ducts
Authors: Makenas BJ
Published: December 2008

The data base of Type 316 stainless steel 20% cold-worked cladding swelling measurements from mixed-oxide fuel pins irradiated in Experimental Breeder Reactor-II (EBR-II) has been extended to a fast (E > 0.1 MeV) fluence of 17 × 1022 neutrons (n)/cm2. Previously, the data base from actual fuel pins included only developmental and Fast Flux Test Facility (FFTF) first core cladding of 5.84 mm (0.230 in.) diameter irradiated to a maximum fast fluence of 13 × 1022 n/cm2. Recent data includes FFTF fourth core material and cladding samples 7.37 mm (0.290 in.) in diameter that were taken from various advanced oxide experiments. Differences in incubation parameter between the swelling of first and fourth core material were at first attributed to heat-to-heat differences, but later were shown to be more properly attributed to different experimental and cladding fabrication parameters. Peak swelling values have now reached 40% volume change.

Swelling in cold-worked Type 316 stainless steel ducts used in EBR-II has also been evaluated using coupons cut or punched from irradiated duct faces. Substantial differences in swelling between faces, which reflect the local reactor environment, have been observed. More recently, duct material at the same maximum fluence as that of the fuel pin cladding has been added to the data base and compared to the swelling of EBR-II cladding.
Swelling of AISI Type 304L Stainless Steel in Response to Simultaneous Variations in Stress and Displacement Rate
Authors: Porter DL , Garner FA
Published: December 2008

The void swelling of annealed AISI Type 304L stainless steel was studied to determine the effects of simultaneous variations in several environmental variables, namely, applied stress and displacement rate. It was found that the transient regime of swelling was modified by both variables in much the same way as previously observed in single-variable experiments. Lower displacement rates and applied tensile stresses shortened the transient regime of swelling. In addition, it was discovered that the simultaneous application of lower dose rates and applied stresses shortened the transient regime to no lower than that observed in the unstressed pure iron-nickel-chromium ternary system, or ∼10 displacements per atom (dpa). This implies that the 10 dpa transient may be a generic minimum for iron-based austenitic alloys. Stress and displacement rate appear to act on a common swelling control mechanism, most likely the effectiveness of swelling-inhibitive solutes on void nucleation.
Evolution of Cavity Microstructure in Ion-Irradiated Type 316 Stainless Steel and Fe-20Ni-15Cr Alloy
Authors: Kohyama A , Loomis BA , Ayrault G , Igata N
Published: December 2008

The effect of a helium implantation schedule on the evolution of the cavity microstructure in Type 316 stainless steel and Fe-20Ni-15Cr alloy during heavy-ion irradiation was investigated for damage levels up to 100 displacements per atom (dpa) with three helium injection schedules, that is, 15 atomic parts per million (appm) He/dpa, 50 appm He/dpa, and 15 appm He pre-injected prior to Ni+ ion irradiation. In the case of the dual-ion irradiated specimens, there was a trend towards a saturation of the swelling with increasing damage level that was coincident with the saturation and a subsequent decrease of the number density of the small cavities (<8 nm diameter for Type 316 stainless steel and <4 nm for Fe-20Ni-15Cr) and the dislocation density. The bi-modal cavity size distribution that was determined for the Fe-20Ni-15Cr alloy at 40 dpa changed to uni-modal distribution at 65 and 100 dpa.
Experimental Investigation of the Effect of Injected Interstitials on Void Formation
Authors: Badger B , Plumton DL , Zinkle SJ , Sindelar RL , Kulcinski GL , Dodd RA , Wolfer WG
Published: December 2008

Pure nickel, a “pure” Type 316 stainless steel (P7), and two high-strength copper alloys have been irradiated with either 14-Me V nickel or copper ions to a peak damage level of 50 displacements per atom (dpa) (K = 0.8) at homologous temperatures ranging from 0.4 to 0.6 Tm. The irradiated foils have been examined in cross section in an electron microscope. The injected interstitial effect on the suppression of the measured void densities in nickel and P7 was found to increase with decreasing temperature. The comparison of these results with nucleation theory shows good qualitative agreement. Quantitative discrepancies are attributed to diffusional spreading of point defects and to the presence of impurity atoms in the matrix. A copper alloy irradiated at 300°C showed a small heterogeneous void density characteristic of the high temperature end of the void swelling regime, while no voids formed in the alloys irradiated ≧400°C. This result is in excellent agreement with nucleation theory that indicates the void swelling regime in ion-irradiated, low impurity copper should be less than 300°C (0.42 Tm.
Ion Bombardment Damage in a Modified Fe-9Cr-1Mo Steel
Authors: Farrell K , Lee EH
Published: December 2008

A normalized-and-tempered Fe-9Cr-1Mo steel, modified with small quantities of niobium and vanadium, was bombarded with 4 MeV iron ions to a nominal displacement level of 100 displacements per atom (dpa) at temperatures of 400, 450, 500, 550, and 600°C. The major microstructural damage feature created in the lathlike α-ferrite grains was dislocation tangles that coarsened with increasing bombardment temperature. Sparse cavities were heterogeneously distributed at 500 and 550°C. Incorporation of helium and deuterium simultaneously in the bombardments at rates of 10 and 45 atomic parts per million (appm)/dpa, respectively, introduced very high concentrations of small cavities at all temperatures, many of them on grain boundaries. These cavities were shown to be promoted by helium. A small fraction of the matrix cavities exhibited bias-driven growth at 500 and 550°C, with swelling <0.4%. This is a very narrow temperature range for bias-driven swelling. It is about 125°C higher than the peak swelling temperature found in neutron irradiations, which is compatible with the higher damage rate used in the ion bombardments. High concentrations of subgrain boundaries and dislocations resulting from the heat treatment, and unbalanced cavity and dislocation sink strengths in the damage structures contribute to the swelling resistance. Such resistance may not be permanent. High densities of bubbles on grain boundaries indicate a need for helium embrittlement tests.