bluuebunny/crossref_metadata_2025 huggingface dataset:
Characterization of Mode I and Mixed-Mode Delamination Growth in T300/5208 Graphite/Epoxy
Authors: Ramkumar RL , Whitcomb JD
Published: December 2008

This paper investigates the roles Mode I (opening mode) and Mode II (inplane shear) strain-energy release rates (GI and GII, respectively), play in inducing delamination growth under static and fatigue loading. Double cantilever beam (DCB) specimens were used for pure Mode I tests. Cracked lap shear (CLS) specimens were used for mixed-mode tests. All specimens were fabricated using T300/5208 graphite/epoxy. Delaminations were introduced during fabrication by inserting folded Kapton films between selected plies. Delaminations were located between two 0° plies in an attempt to inhibit delamination growth across plies into adjacent interfaces. The critical Mode I strain-energy release rate, GIc, was obtained from static DCB tests. Static tests on mixed-mode CLS specimens measured the total strain-energy release rate, which was broken into GI and GII components using a geometrically nonlinear finite-element analysis. By incorporating these values of GI and GII, and GIc from static DCB test results, into an assumed failure criterion, the critical Mode II strain energy release rate (GIIc) was computed.

Fatigue-induced delamination growth was characterized by conducting constant-amplitude fatigue tests at a minimum to maximum cyclic load ratio (R) of 0.05 and a frequency (ω) of 10 Hz. During the tests, the maximum and minimum strain-energy release rates (Gmax, Gmin) and the delamination growth rate (da/dN) were monitored. Fatigue test results on DCB specimens yielded a power-law relationship between da/dN and GImax. Similar results from CLS tests provided da/dN versus Gmax relationships. The contributions of GI and GII components to mixed-mode delamination growth were assumed to be additive. Hence, the power law for a pure Mode II delamination growth was derived from CLS test results by subtracting the contribution due to GI determined from DCB tests.
Effects of Strain Rate on Delamination Fracture Toughness of Graphite/Epoxy
Authors: Aliyu AA , Daniel IM
Published: December 2008

The objective of this paper is to evaluate various experimental techniques and analysis methods for the characterization of interlaminar fracture toughness, and to determine the effects of strain rate on that property for a graphite/epoxy composite. Mode I interlaminar fracture was investigated by means of a double-cantilever beam (DCB) specimen for AS-4/3501-6 graphite/epoxy. Hinged tabs were used to insure unrestrained rotation at the free ends. Specimens were loaded at quasi-static deflection rates of up to 8.5 mm/s (20 in./min) corresponding to crack extension rates of over 51 mm/s (2 in./s). Crack extension was monitored by means of strain gages mounted on the surface of the specimen, or a conductive-paint circuit attached to the edge of the DCB specimen. Continuous records were obtained of load, deflection, and crack extension for determination of the strain energy release rate. The latter was expressed as a power law of the crack extension velocity. Results indicate that the strain energy release rate increases with crack velocity by up to 28% for the range of rates considered here.
Matrix Deformation and Fracture in Graphite-Reinforced Epoxies
Authors: Bradley WL , Cohen RN
Published: December 2008

The resin-dominated fracture behavior of several graphite/epoxy composites has been studied using delamination of split laminates and transverse cracking of compact tension specimens. Pure Mode I and mixed Mode I/Mode II fracture behavior has been studied using specimens cut from unidirectional laminates with the critical energy release rates GIc or GI.IIc being measured. The effect on GIc of variations in resin ductility, thickness of resin-rich region through which cracking occurs, and fiber debonding has been investigated. In situ delamination fracture in a scanning electron microscope and postmortem fractography have been used to determine the micromechanisms of fracture which control GIc. A qualitative micromechanics model of delamination has been proposed and used to interpret the observed variations in GIc.
In-Situ Determination of the Strength of Marine Soils
Authors: Richards AF , Zuidberg HM
Published: December 2008

Minor emphasis is placed on three topics: (1) marine soil properties, distribution, and state of stress; (2) in-situ testing methods, in which it is noted that only the cone penetrometer, piezocone, and field vane are routinely used by the offshore geotechnical industry; and (3) the drilling-wireline and the seabed deployment systems and their principal subsystems. Major emphasis is placed on two topics: (1) quality assurance of in-situ testing and (2) a discussion of test descriptions and test standardizations, particularly with respect to the field vane and cone penetrometer. Some of the more important findings are that the in-situ strength distribution, particularly in the horizontal plane, is not well known; industrial offshore in-situ testing is a complex system involving ships, operational stability, deployment equipment, drilling or seabed subsystems, and probes and sensors; and how in-situ strength may be degraded by drilling and in-situ testing procedures. In addition, the offshore geotechnical industry recommends that full test descriptions be provided, unless supplemented or replaced by recognized standards. Only the field vane and cone penetrometer tests are reasonably standardized. The principal conclusion is that in-situ strength testing usually involves fewer significant problems than sample collection and laboratory testing.
A Lightweight 12-m Cone Penetrometer
Authors: Johnson BA , Beard RM
Published: December 2008

This paper describes a remotely operated, bottom resting cone penetrometer for testing to soil depths of 12 m (40 ft) in un-cemented sands, silts, and soft to medium stiff clays. It is lightweight (less than 4.5 kN [10 000 lb]) and can achieve 12-m penetration with a 4.5 kN (10 000 lb). The force necessary to push the cone rod into the seafloor was reduced by jetting.

The device is called the XSP for experimental static penetrometer. It is capable of performing electric friction-cone penetration tests to 12-m depths in soils at water depths of 60 m. The XSP is 15 m (50 ft) tall, weighs about 4.5 kN (10 000 lb), and uses an electric friction cone conforming to ASTM Method for Deep, Quasi-Static, Cone and Friction-Cone Penetration Tests of Soil (D 3441). Friction on the push rod has been sharply reduced by using a water-jet to flush sediment away from it.

Test results from four different soil types are presented. Comparison is made between side by side tests conducted with and without the water jet. Core data are also presented for comparison with the cone data.
Rod Shear Tests in Marine Clays
Authors: Amerasinghi SF , DeGroff WL
Published: December 2008

Laboratory rod shear tests were conducted on offshore clay samples with a test device adapted from a conventional triaxial cell. The load rod surface had an unpolished finish. Tests were of the fast type with controlled rate of displacement. The program included tests on normally consolidated specimens and measurement of response up to or approaching residual conditions. Failure conditions are assessed by comparing the test data with soil failure from an effective stress framework and rod-soil rupture. For these Gulf of Mexico clays, the experimental data compare well with a stress history dependent ratio of shear stress to consolidation stress. Rod shear results can be influenced by local drainage, leading to increases in strength of clays.
Three-Dimensional Stress Relaxation Behavior of Marine Sediments
Authors: Drumright EE , Nelson JD
Published: December 2008

An experimental program was conducted to investigate the creep-relaxation behavior of ocean bottom sediments under a three-dimensional state of stress. At the onset of stress relaxation, a linear relationship was found to exist between the octahedral shear stress and the logarithm of time, over some finite time span. The magnitude of stress decrease and the rate of relaxation was larger for a highly plastic marine clay than for a low plasticity silty clay. Both clays were able to sustain a constant, nonzero value of octahedral shear stress at the completion of the relaxation phase of each experiment. The minimum value of the octahedral shear stress was accurately computed using a hyperbolic fit of the observed data.
An Overview of Selected EPA RCRA Test Method Development and Evaluation Activities
Authors: Friedman D
Published: December 2008

This paper will present an overview of the U.S. Environmental Protection Agency's current and near-term future test method development and evaluation activities in light of the agency's regulatory activities under the Resource Conservation and Recovery Act. The paper will discuss the work in terms of the regulatory purpose to be served, the approach to be taken in conducting the studies, progress made to date, the responsible research organization, and the anticipated schedule.

Among the specific areas discussed are evaluation of current and proposed SW-846 (Test Methods for Evaluating Solid Waste) methods, development and evaluation of less costly methods for determining the presence and concentration of the Appendix VIII (40 CFR 261) hazardous constituents in groundwater, development and evaluation of sampling methods to determine the concentration of organic compounds in ambient air and stack emissions, and some aspects of the agency's activities in developing procedures to determine the leaching potential of waste materials placed in various environmental settings.
Multilaboratory Analysis of Soil for Leads
Authors: Perket CL , Barsotti LR
Published: December 2008

A multilaboratory test program to determine lead content in soils produced aberrant results from two laboratories and indicated apparent problems with sample preparation. The program demonstrates the importance of quality control in remedial site investigation to determine soil contamination.
Human Exposure Assessment: Basic Elements and Applications in Remedial Engineering Actions at Sites Containing Contaminated Soil and Groundwater
Authors: Dragun J , Erler TG
Published: December 2008

When a soil or groundwater contamination problem is discovered, the attention of the public and of regulatory agencies focuses on the potential effects on human health. However, human exposure to a chemical at some minimal concentration must occur before an adverse effect on human health is realized. The exposure assessment quantifies this exposure; an exposure assessment is the determination or estimation of the magnitude, frequency, duration, and routes of exposure.

This paper addresses the basic elements and applications of the exposure assessment. First, this paper will define and discuss the six basic elements of an exposure assessment. Second, this paper will discuss the usefulness of the exposure assessment in evaluating remedial actions to be implemented at hazardous waste sites. Third, this paper presents an actual case study, involving an existing Superfund site, in which an exposure assessment was performed to select a cost-effective remedial action plan that provided the greatest benefit at an acceptable risk.
A Proposed In-Vivo/In-Vitro Approach to the Toxicological Assessment of Hazardous Waste
Authors: Lewtas J , Andon B
Published: December 2008

An in-vivo/in-vitro toxicological screen has been developed to evaluate potentially hazardous waste samples and process stream residuals. The biological methods employed in the screen are designed to be rapid, cost-effective, and capable of screening large numbers of wastes. Emphasis is placed on identifying a wide range of potential toxic responses associated with each waste by employing diverse test methods. The toxic end points identified by the screen include mutagenesis/carcinogenesis, general toxicology, neurotoxicology, reproductive toxicology, teratology, and immunotoxicology.

The protocol, called the toxicological screen, involves the oral administration of waste material to male rodents for ten consecutive days. At the end of the ten-day period the whole animal, body tissues, and fluids are evaluated for toxicity. The toxicological screen also involves the oral treatment of pregnant rodents to wastes for ten consecutive days to assess transplacental effects and neonatal survival. A major goal of the toxicological screen is to maximize the amount and type of potential health effects information that can be obtained by exposing metabolically competent intact animals to complex waste mixtures.

The toxicological screen is being validated by using a series of positive (and negative) control compounds of known and defined toxicity. The validation study ensures that the protocol will be capable of detecting biologically active wastes and will allow assessment of the protocol's use as a predictive tool for known chronic effects. An additional goal of the validation study is to identify a subset of the assays from the toxicological screen that most readily detect the toxic potential of the positive control compounds. These selected assays will constitute a prescreen for the entire protocol. The prescreen can then be used as a rapid means of prioritizing waste samples to be evaluated in the full toxicological screen.

Initial trials of the validation study with four positive control compounds demonstrate the toxicological screen's ability to detect biologically active chemicals and to generate dose-response data.
Methods for Testing the Compatibility of Clay Liners with Landfill Leachate
Authors: Bowders JJ , Daniel DE , Broderick GP , Liljestrand HM
Published: December 2008

The compatibility of compacted clay liners with landfill leachate may be evaluated with laboratory permeability tests. Compaction mold permeameters are recommended for laboratory-compacted specimens of clay subjected to low overburden pressure. Flexible wall permeameters are recommended for laboratory-compacted specimens subjected to relatively high overburden pressure and for undisturbed specimens of clay obtained from the field. Before permeability tests are performed, the index properties of the soil should be determined by mixing the soil with water and by mixing the soil with the leachate. If the leachate does not affect the index properties of the soil, it is not likely to affect the permeability. The solubility of the soil in the leachate should be checked if the soil is acidic or basic. Also, for dilute leachates, batch equilibrium tests are recommended before a permeability test is initiated so that the tendency for the soil to adsorb materials in the leachate can be evaluated. The effluent liquid should be monitored to determine the degree of breakthrough of key constituents. It is best to continue the permeability test until full breakthrough is achieved.
A Simple Procedure for Acceptance Testing of Freshly Prepared Solidified Waste
Authors: Myers TE
Published: December 2008

The U.S. Department of the Army (DA) is considering treatment and disposal options for hazardous wastes generated at DA facilities that involve solidification processing and landfilling of waste. A rapid test procedure that correlates to critical processing parameters, specifically process additive dosages, is needed for monitoring solidification processing. Candidate testing procedures were evaluated in bench-scale studies for their ability to distinguish between low-, intermediate-, and high-strength formulations of a solidification process. A simple, rapid, and inexpensive test procedure is described that showed promise in bench-scale studies of being a reliable means of real-time monitoring of solidification processing. The procedure uses the cone index (CI) of freshly prepared samples as measured with a cone penetrometer to provide data for a determination of the acceptance or rejection of material before it is actually landfilled. The test procedure involves molding and testing specimens of solidified waste immediately after solidification processing and consists of the following steps: (1) compaction using a standard compaction procedure; (2) determination of CI using standard Department of the Army procedures; and (3) comparison of results with previously established acceptance/rejection criteria. Establishment of acceptance/rejection criteria is based on empirical correlation of CI to specific process/waste formulations that are known to set and cure properly and are, therefore, acceptable for landfilling. Application of the recommended testing procedure to field acceptance testing is discussed. Data from the bench scale evaluation of various testing systems are also presented.
Test Burns: A Critical Step in the Design of Hazardous Waste Incineration Systems
Authors: Santoleri JJ
Published: December 2008

With the final implementation of the Resource Conservation and Recovery Act covering the disposal of hazardous wastes by incineration, certain basic criteria have been established. Most critical is the ability to reach levels of 99.99% destruction and removal efficiencies (DRE) of the principal organic hazardous constituents (POHC). In order to be assured that this is possible, a pilot test burn is necessary. If these wastes are presently being burned in a similar incineration system, the data can be used in the permit application.

However, there are many wastes which have been disposed of by landfill, land treatment, and chemical treatment that still present a hazard to our environment, and high-temperature oxidation is the only sure method of reaching destruction to four nines.

Test burns provide information for the proper design of the oxidizer related to air flow, fuel flow, oxidation temperature, mixing technique to achieve turbulence, atomizer type, residence time, and resultant emissions. Other problems inherent in handling the waste—such as pumping, piping, valving and control, atomization fluid and pressure, and atomizer location—are also encountered in the test burn and provide insight in the design of the full-scale system.

Certain control techniques which may be necessary for handling a variety of wastes are encountered in the test burn and provide the opportunity to check the effects of the unit operation.

The need for proper design and operation of a test burn facility will be discussed. Problem test burns will be reviewed and related to the effect on scale-up of full scale operating units. When a process changes, resulting in a different waste product, the pilot unit will permit testing and optimization of design without interruption of the full-scale system.
Finite-Element Analysis of Drilled Piers Used for Slope Stabilization
Authors: Oakland MW , Chameau JA
Published: December 2008

During the past two decades, the use of bored piles, or drilled piers, has been shown on several occasions to be an effective deterrent to exessive slope movements. The technique is applicable when either the resisting forces of the slope are to be decreased or the driving forces to be increased. These situations arise when cutting a steeper slope or adding a surcharge above a slope, respectively. The movements of landslides can also be controlled by drilled-in piers or piles.

Several investigators have studied the problem of a single pier subject to lateral soil movement, given certain simplifying assumptions with regard to the soil model, soil-pile interface, and repartition of the lateral loads. It is commonly assumed that a plane strain condition prevails, and the piers are analyzed in two dimensions. This does not allow the effects of pier size and spacing to be represented, although finite-difference solutions have shown these to be very significant. Current design practice uses piers spaced closely together in a continuous barrier. Part of the face is usually exposed to form a retaining wall, and in some cases the piers are tied back at the top. The design methods are similar to those used for sheet-pile walls and usually valid for relatively shallow overburden depths. This methodology results in a conservative sizing and spacing of the piers.

In this paper a finite-element based methodology is proposed to model the three-dimensional effects involved in the stabilization of surcharged slopes with drilled piers. The soil is modeled with eight nodes, 24 degrees of freedom isoparametric elements. The piers are represented by three-dimensional spar elements. The program can be used to determine the effects of piers' position, size, spacing, and stiffness on slope movements. This program is the first step towards a more general methodology that will consider soil nonlinearity and creep, and make provisions for slippage around the pile.
Helical Anchor Piles Under Lateral Loading
Authors: Puri VK , Stephenson RW , Dziedzic E , Goen L
Published: December 2008

Anchors are used in civil engineering practice to provide resistance against uplift and overturning forces for structures such as transmission line towers, aircraft mooring, pipelines, offshore structures, mobile homes, and so forth. Although there are a wide variety of anchor types available, helical screw anchors, consisting of a steel shaft to which one or more helices are attached by welding, are finding wider usage particularly for the support of transmission line towers. Because these anchors are installed by truck mounted power augurs they can be used immediately after installation.

Although there exists in the geotechnical engineering literature a variety of techniques for evaluating lateral-load capacity of piles, there are no published methods for analyzing helical anchor lateral stability when used as piling. The present study was undertaken to develop suitable mathematical models based upon the current state of the art for determination of lateral-load capacity of helical-type anchor piles. The model selected was patterned after Matlock and Reese's elastic theory model. The model was modified to take into account the influence of the method of installation and other unique characteristics of this type of foundation. Based on the results of this study it was found that helical anchor piles can develop significant resistance to lateral loads, and this resistance is almost exclusively controlled by the extension shaft diameter.
Markings on Crack Surfaces of Brittle Materials: A Suggested Unified Nomenclature
Authors: Frechette VD
Published: December 2008

Terms to characterize the markings on crack-generated surfaces of brittle materials have come to be used in different ways as a result of the variety of interests and backgrounds of workers in this field and the scattered nature of the literature. A single system of nomenclature which is explicit, universally applicable, and self-consistent should be helpful in aiding communication among fractographers. This paper suggests a possible unified system for discussion and refinement.
Fracture Mist Region in a Soda-Lime-Silica Float Glass
Authors: Ball MJ , Landini DJ , Bradt RC
Published: December 2008

The mist region near the fracture origin was studied in a series of soda-limesilica float glass specimens ranging in strength from about 30 to 90 MPa. Both the mirror/mist and the mist/hackle radii were measured to ascertain the dependence of the width of the mist region on the strength level. The mirror/mist constant was found to be 1.80 ± 0.15 MN/m3/2 and the mist/hackle constant to be 2.42 ± 0.16 MN/m3/2. Both analytically and experimentally, the width of the mist region was found to be inversely related to the square of the fracture stress; that is, (Wmist) is proportional to (1/σf2). This suggests a dependence of the mist region width on the elastic strain energy at fracture initiation.

The surface topography of the mist region was analyzed by a scanning electron microscopy computerized contour mapping technique to determine the surface roughness within the mist region. It was observed that the average root-mean-square roughness in the mist region was proportional to the fracture stress squared. This suggests that the fracture surface roughness of the mist region, or alternatively the true surface area of the mist region, is also determined by the stored elastic strain energy in the specimen before fracture.

It is concluded that the mist region width and the mist region roughness are both determined by a strain energy criterion. It is suggested that they may be related through a generalized mist region parameter.
An Examination of Cleaning Techniques for Post-Failure Analysis
Authors: Vecchio RS , Hertzberg RW
Published: December 2008

A study has been made of the effectiveness of cleaning techniques for post-failure analysis. Air blast, organic solvents, and repeated stripping of cellulose acetate replicas (benign techniques) are useful in removing loosely adhering particles, grease, and oils. More aggressive removal techniques, however, are required for tightly bonded oxidation and corrosion products. A solution containing Alconox cleaning detergent was examined and found to remove most corrosion debris from fracture surface regions associated with cleavage and intergranular and microvoid coalescence fracture micromechanisms. In some instances, however, indications of surface degradation and etching were apparent which resulted from excessive exposure time in the cleaning solution. Degradation and etching led to complications in the interpretation of these fracture surface markings. Fatigue fracture surfaces exhibited the poorest response to the benign cleaning techniques of all fracture modes examined. Thus it was not possible to reveal typical fatigue markings (for example, striations) after specimen exposure to the Alconox solution.
Use of “Marker Blocks” As An Aid in Quantitative Fractography in Full-Scale Aircraft Fatigue Testing: A Case Study
Authors: Dainty RV
Published: December 2008

Damage tolerant design criteria and the current use of random or flight-by-flight loading methods in the full-scale testing of aircraft structures have necessitated the development of new techniques for acquiring accurate fatigue crack growth information from fracture surface analysis. This paper describes a technique that utilized a 64-cycle constant-amplitude “marker block”, in an otherwise random load spectrum of 4469 cycles, to derive fatigue crack growth data from an aluminum alloy spar cap and two wing skin rivets. The presence of an undetected incipient crack in the spar cap, from a previous full-scale test, provided an opportunity of accounting for the entire random loading crack growth history in terms of the “marker band” spacings. It was possible to identify the marker bands in the scanning electron microscope at relatively short crack lengths of 2.6 mm for the spar cap and 0.5 mm for the rivets. A total of 89 of the 90 marker blocks applied in the test were accounted for on the spar cap fracture surface. Examination of the rivet fracture surfaces revealed 12 and 8 marker bands, respectively, over crack lengths of some 3 mm.
Fractographic Analysis of the Primary Oil Pump Shaft Fracture from a Steam Turbine
Authors: Swaminathan VP
Published: December 2008

An extension shaft is connected to the governor end of a high-pressure steam turbine. This shaft, which drives the primary oil pump impeller in a tubine-generator unit, fractured while in service. Metallurgical analysis included extensive fractographic study using optical, scanning, and transmission electron microscopes. Fatigue striations and beach marks were observed on the fracture surface. Striation spacing measurements were made on carbon replicas taken at various crack depths. The approximate magnitude of the cyclic stresses causing these striations was calculated from data available from scale-model test specimens. Peeling-type cracks initiating from the bottom of the keyway indicative of torsional oscillations were also found. The fracture initiated at the keyway fillet and propagated in high-cycle fatigue mode under combined torsional and bending loads.
Non-Isothermal In-Reactor Creep of Nickel Alloys Inconel 706 and PE-16
Authors: Gilbert ER , Chin BA
Published: December 2008

The results of in-reactor step temperature change experiments conducted on two nickel alloys, PE-16 and Inconel 706, were evaluated to determine the creep behavior under non-isothermal conditions. The effect of the temperature changes was found to differ significantly between the two alloys. Following a step temperature change, the creep rate of PE-16 adjusted to the rate found in isothermal tests at the new temperature. In contrast, for Inconel 706, a reduction in irradiation temperature from 540 to 425°C produced a 300% increase in creep above that measured at 540°C in isothermal tests. The Inconel 706 in-reactor creep response to temperature changes was attributed to the dissolution of the γ″ phase and the subsequent loss of precipitation strengthening at temperatures below 500°C.
In-Pile Creep Strain and Failure of Cold-Worked Type 316 Titanium Pressurized Tubes
Authors: Boutard J-L , Maillard A , Carteret Y , Levy V , Boyer J-M
Published: December 2008

The in-pile creep and failure behavior of cold-worked Type 316 titanium pressurized tubes irradiated in the same rig at temperatures ranging from 430 to 480°C to 650 to 700°C up to 81.4 dpaF (French displacements per atom) maximum in PHENIX are presented and compared to monitors.

At temperatures below 600°C, the in-pile hoop strains are consistent with the expected amount of irradiation creep. In the range of 650 to 700°C, the measured plastic strains are dose rate independent. This supports the assumption that the thermally controlled mechanisms dominate.

Examinations by fractography and optical micrography show that the failures are intergranular either in-pile or out-of-pile. In both cases, the damage consists of intergranular wedge cracks, and no cavitation can be observed by transmission electron microscopy.

The in-pile embrittlement that gives lower failure strain is to be associated with a decrease of the surface energy of grain boundaries rather than growth and coalescence of cavities.
Critical Assessment of Low-Fluence Irradiation Creep Mechanisms
Authors: Henager CH , Simonen EP
Published: December 2008

A climb-controlled guide (CCG) creep model, which had been used to successfully rationalize low-fluence, light-ion irradiation creep data in pure nickel, accounted for low-fluence irradiation creep rates and loop growth rates in Type 316 stainless steel. The model also predicted a weak stress dependence and a weak temperature dependence in agreement with typical observations. Both light-ion and neutron irradiation creep measurements and microstructural observations at low fluences were examined and compared with predictions of the CCG model. Calculated creep rates compared to measured creep rates demonstrated that dislocation glide was the dominant mode of deformation during low-fluence creep when interstitial loops were small. When the interstitial loop radius approached one half the average dislocation glide distance, the dislocation glide contribution was small. The stress-induced preferred absorption (SIPA) creep mechanism contributed an increasing fraction of the total deformation as the loop radius increased and became dominant at fluences greater than 1 displacement per atom (dpa).

The CCG creep model assumes that glissile network dislocations intersect the small dislocation loop glide barriers, climb into a favorable orientation, and annihilate the loop through a Burgers vector reaction. Dislocation climb controls the rate of loop annihilation that allows dislocation glide between loop barriers. The creep rate is determined by a balance between irradiation-enhanced dislocation climb and interstitial loop growth.
Irradiation-Creep-Induced Anisotropy in a/2 <110> Dislocation Populations
Authors: Gelles DS
Published: December 2008

The contribution of anisotropy in Burgers vector distribution to irradiation creep behavior has been largely ignored in irradiation creep models. However, findings on Frank loops suggest that it may be very important. Procedures are defined to identify the orientations of a/2 <110> Burgers vectors for dislocations in face-centered-cubic crystals. By means of these procedures, the anisotropy in Burgers vector populations was determined for three Nimonic PE16 pressurized tube specimens irradiated under stress. Considerable anisotropy in Burgers vector population develops during irradiation creep. It is inferred that dislocation motion during irradiation creep is restricted primarily to a climb of a/2 <110> dislocations on 100 planes. The effect of these results on irradiation creep modeling and deformation-induced irradiation growth is considered.
Microstructure of Irradiated Inconel 706 Fuel Pin Cladding
Authors: Yang WJS , Makenas BJ
Published: December 2008

A fuel pin from the HEDL-P-60 experiment with a cladding of solution-annealed Inconel 706 breached in an apparently brittle manner at a position 12.7 cm above the bottom of the fuel column with a crack of 5.72 cm in length after 5.0 atomic percent burnup in Experimental Breeder Reactor (EBR-II). Temperatures (time-averaged midwall) and fast fluences for the fractured area range from 447°C and 5.5 × 1022 neutrons (n)/cm2 to 526°C and 6.1 × 1022 n/cm2 (E > 0.1 MeV). Specimens of the fractured fuel pin section were successfully prepared and examined in both a scanning electron microscope and a transmission electron microscope. The fracture surfaces of the breached section showed brittle intergranular fracture characteristics for both the axial and circumferential cracks. Formation of γ′ in the matrix near the breach confirmed that the irradiation temperature at the breached area was below 500°C, in agreement with other estimates of the temperature for the area, 447 to 526°C. A hexagonal η-phase, Ni3 (titanium, niobium), precipitated at boundaries near the breach. A more extensive η-phase coating at grain boundaries was found in a section irradiated at 650°C. The η-phase plates at grain boundaries are expected to have a detrimental effect on alloy ductility. A plane of weakness in this region along the {111} slip planes will develop in Inconel 706 because the η-plates have a {111} habit relationship with the matrix.
Microsegregation Observed in Fe-35.5Ni-7.5Cr Irradiated in EBR-II
Authors: Brager HR , Garner FA
Published: December 2008

In another recent study of the compositional dependence of swelling in annealed iron-nickel-chromium alloys, it was found that some annealed alloys densified during irradiation. No precipitate phases were observed to form, however. At 593°C, one alloy, Fe-35.5Ni-7.5Cr, which was particularly resistant to swelling, increased in density 0.9% at 7.6 × 1022 neutrons (n)/cm2 (E > 0.1 MeV).

Examination by energy dispersive X-ray analysis revealed that substantial oscillations occur in the nickel content of the alloy, varying from 25 to 53% about the nominal level of 35.5%. These oscillations exhibit a period of ∼200 nm. Regions enriched in nickel are depleted in chromium and iron, and the reverse is true in regions of low nickel content. This spinodal-like process produces a net densification and also appears to eventually destroy the swelling resistance of the alloy. Once voids form in the nickel-poor chromium-rich regions, further segregation of nickel to void surfaces is expected to accelerate the loss of swelling resistance.
Some Observations on the Effect of Stress on Irradiation-Induced Swelling in AISI Type 316 Stainless Steel
Authors: Lauritzen T , Bell WL , Rosa JM , Vaidyanathan S
Published: December 2008

An evaluation of the effect of stress on the swelling behavior of 20% cold-worked AISI Type 316 stainless steel was conducted. Beam specimens strained in a four-point bending mode during fast neutron irradiation in Experimental Breeder Reactor-II (EBR-II) were selected for this study. Peak elastic fiber stresses in the beams ranged from 140 to 320 MPa during irradiation to 8 × 1022 neutrons (n)/cm2 (E > 0.1 MeV) at temperatures of 685 and 697 K. Regions of the beams corresponding to tensile, compressive, and neutral loading were examined by transmission electron microscopy (TEM) to evaluate the type, morphology, and distribution of irradiation-induced voids.

TEM revealed a fairly uniform distribution of voids throughout the lower temperature beam with little difference noted in void size, void density, or swelling. In the higher temperature beam, void densities increased by as much as a factor of two from the plane of zero stress—the central portion of the beam—to the tension and compression surfaces. This produced an increase in swelling relative to the neutral axis in both tension and compression regions, the latter showing a slightly lower swelling as the result of a somewhat smaller average void size. The general microstructure was that of a cold-worked material, with similar dislocation arrays in the three regions of the beams. Widely scattered faulted loops were detected but, because of their small size and density, no assessment regarding the influence of stress on such distributions was possible. However, there appeared to be no interaction between voids and dislocations and no encircling of voids with dislocation loops was noted.

Although the irradiation conditions in the present work produced extremely low levels of swelling with associated large uncertainties, the results suggest that swelling is enhanced by a tensile stress such as is produced in bending. Moreover, the results also indicate that a compressive stress similarly produced may also contribute to an increase in swelling.
Influence of Helium on Swelling of Steels
Authors: Levy V , Gilbon D , Rivera C
Published: December 2008

In this work, we have studied the effect of helium and its injection mode on the microstructure of Type 316 and titanium-modified Type 316 stainless steels, both in their solution-annealed and cold-worked states. Irradiations have been conducted in a dual-beam accelerator to doses up to 150 dpa in a wide range of temperatures, from 550 to 750°C. Different injection modes have been investigated: cold preinjection, hot preinjection, and dual beam.

The results show that the effect of helium on swelling is largely dependent on the injection mode and also on the chemical composition of the alloy considered. In Type 316 steel, the presence of helium decreases swelling, the major effect being observed when helium is preinjected at room temperature. In titanium-modified steels, if a high density of tiny helium bubbles are present in all the specimens containing helium, void swelling only occurs for dual-beam irradiations.

In conclusions, this work shows that the effect of helium on void swelling depends on its injection mode, but also that the sense of this effect is clearly different when comparing the behavior of a low and a high swelling alloy.
Comparison of Depth-Dependent Microstructures of Ion-Irradiated Type 316 Stainless Steels
Authors: Sindelar RL , Dodd RA , Kulcinski GL
Published: December 2008

The microstructural response of P7, a high-swelling, “pure” Type 316 stainless steel and the Magnetic Fusion Engineering (MFE) heat of Type 316 stainless steel were investigated after 14-Me V nickel-ion irradiation. Specimens of the P7 alloy were irradiated to fluences of 3.3 × 1016 14-Me V nickel ions/cm2. Irradiation temperatures ranged from 500°C to 650°C (0.45 to 0.6 Tm). In addition, a sample of Type 316 stainless steel was irradiated at 650°C (0.6 Tm) to a fluence of 3.3 × 1016 14-Me V nickel ions/cm2. The irradiated specimens were examined in cross section by electron microscopy. the 500°C irradiation of the P7 alloy produced a depth-dependent void distribution influenced by the excess interstitial effect of the bombarding ions. The 650°C irradiations of the P7 alloy produced a bimodal void distribution at the damage peak. The 650°C irradiation of Type 316 stainless steel produced needle-like precipitation in the entire damage region.
Direct Observation of Cascade Defect Formation at Low Temperatures in Ion-Irradiated Metals
Authors: Muroga T , Hirooka K , Ishino S
Published: December 2008

Direct transmission electron microscopy observations of cascade defect formation have been carried out in gold, Type 316 stainless steel, and aluminum irradiated by Al+, Ar+, and Xe+ ions with energies between 80 and 400 ke V. By utilizing a link of an ion accelerator to an electron microscope, in situ observations at low temperature (-150°C) have become possible. In gold, subcascade structures are clearly observed in all cases. Obvious dependence on projectile mass and energy is observed for cascade structure and vacancy clustering efficiency in gold and for defect visibility in aluminum and Type 316 stainless steel. A computer simulation calculation using MARLOWE shows subcascade distributions a little smaller in size and larger in number than the present observation.
Nonequilibrium Segregation and Phase Instability in Alloy Films During Elevated-Temperature Irradiation in a High-Voltage Electron Microscope
Authors: Lam NQ , Okamoto PR
Published: December 2008

The effects of defect-production rate gradients, caused by the radial nonuniformity in the electron flux distribution, on solute segregation and phase stability in alloy films undergoing high-voltage electron-microscope (HVEM) irradiation at high temperatures are assessed in this paper. Two-dimensional (axially symmetric) compositional redistributions were calculated, taking into account both axial and transverse radial defect fluxes. It was found that when highly focused beams were employed, radiation-induced segregation consisted of two stages: dominant axial segregation to the film surfaces at short irradiation times and competitive radial segregation at longer times. The average alloy composition within the irradiated region could differ greatly from that irradiated with a uniform beam, because of the additional atom transport from or to the region surrounding the irradiated zone under the influence of radial fluxes. As a result, damage-rate gradient effects must be taken into account when interpreting in situ HVEM observations of segregation-induced phase instabilities. The theoretical predictions are compared with experimental observations of the temporal and spatial dependence of segregation-induced precipitation in thin films of nickel-aluminum, nickel-germanium, and nickel-silicon solid solutions.
Establishing a Calibration Laboratory for Industrial Radiation Thermometry
Authors: Barber R , Brown ME
Published: December 2008

Establishing an industrial laboratory involves many variables because of the wide variety of needs. First, the basic principles involved are discussed along with key definitions. The importance of traceability is stressed along with methods of achieving it. Some representative calibration equipment and important calibration parameters are described.
Radiation Thermometry—Status and Trends
Authors: Barron WR , Goldberg AE
Published: December 2008

The use of radiation thermometry has expanded over the past five years and applications will increase to meet new industrial demands and the addition of new technologies. There is the full product spectrum from portables to transmitters to closed loop control systems. Tailored designs also are being developed involving dual wavelength sensors, multihead systems, fiber-optic sensors, and hybrid designs to measure aluminum.

This paper summarizes the present and future trends in radiation thermometry. Instrument development will continue as user demands for accurate product temperature measurements are uncovered.
A Review of Temperature Measurement in the Steel Reheat Furnace
Authors: Martocci AP , Mihalow FA
Published: December 2008

The incentive for conducting research and development on reheat furnaces is substantial; the domestic steel industry spent approximately one billion dollars on fuel in reheat furnaces in 1981. Bethlehem Steel Corp. spent $145 million of that total, and neither figure includes fuel consumed in soaking pits or annealing furnaces. If we set a goal to save 10% of these annual fuel costs, that translates into $100 million for the domestic steel industry and $14.5 million for Bethlehem Steel. These large sums of money are significant incentives.

The purpose of this paper is to review the historical heating practices and equipment at steel reheat furnaces along with current practices and instrumentation.
Defining Silicon Dioxide
Authors: Hemenway DR
Published: December 2008

Crystalline silicon dioxide has been associated with pulmonary lung disease. A number of descriptive terms such as “amorphous silica,” “free silica,” “silica flour,” and “fumed silica” have arisen in the literature as a result of studies related to health and the silicon dioxide forms. The definition of these terms has been the result of limitations (both analytical and physical) in qualitative and quantitative analytical methods, as well as definitions associated with the type of manufacturer or process producing the silicon dioxide. X-ray diffraction and typical mineralogical nomenclature are relevant for the definition of crystalline silicon dioxide polymorphs, but other silicon dioxide materials require alternative techniques for analytical definition of those properties which may be health related.
Definitions for Silica Minerals
Authors: Dunnom DD
Published: December 2008

The author presents some definitions for silica minerals, based on discussions held during a workshop on this subject.
The Function of Thermal Insulation
Authors: Barnhart JM
Published: December 2008

Thermal insulations or thermal insulation systems are usually defined as materials or combinations of materials that retard the flow of heat energy by conductive, convective, or radiative modes of transfer or a combination of these. In order to be effective, they must be properly applied.
Factors Affecting Corrosion of Carbon Steel Under Thermal Insulation
Authors: Lazar P
Published: December 2008

The problem of corrosion under insulation is studied by analysis of seven contributing factors: (1) equipment design; (2) service temperatures; (3) insulation selection; (4) paints and coatings; (5) weather barriers; (6) climate; and (7) maintenance practices. The purposes of our study are to identify optimum locations for inspection of insulated equipment and to identify improvements in new equipment design and insulation, as well as maintenance of existing systems. Emphasis is placed on equipment design features, operating temperature, and weather barrier deficiencies to guide inspection. Weather barrier maintenance is critical for prevention of corrosion on existing equipment. New insulated equipment designs should provide special details so that the system can be better sealed against water entry and allow clearance for the specified insulation thickness. On new equipment or when reinsulating existing equipment, a high quality coating system is recommended, since touch up opportunity does not exist.
Thermal Insulation Materials: Generic Types and Their Properties
Authors: Lang GE
Published: December 2008

Thermal insulation plays a very important function in all of our lives. Without it the cost of energy used in our homes would skyrocket, perishable foods would be available only within a short distance of the source, plastic items and many petroleum products would not exist, and we would have to get used to warm beer and soupy ice cream.

Now to the generic and functional differences of the various types of thermal insulation. One of the most defining properties of a thermal insulation is its service temperature range. Since we are discussing generic types of insulation, and some manufacturers' recommended service temperatures vary slightly, the du Pont Company's established recommended service temperatures are listed in the paper. The properties, good and bad, of generic thermal insulation materials that have a bearing on their individual influence on corrosion of the metals they cover will be discussed.