bluuebunny/crossref_metadata_2025 huggingface dataset:
Microbuckling of Lamina-Reinforced Composites
Authors: Greszczuk LB
Published: March 2009

Compressive strength and failure modes of unidirectionally lamina-reinforced composites were studied both theoretically and experimentally. The failure modes investigated included microbuckling and compressive strength failure of the reinforcement. The influence of the following parameters on compressive strength was investigated experimentally: lamina volume fraction, lamina end fixity, lamina thickness, specimen geometry, and matrix properties. The two-dimensional microbuckling theory showed good correlation with test data from specimens designed to fail by microbuckling. As the Young's modulus of the matrix increased, the failure mode changed from microbuckling to compressive failure of the reinforcement.
Stress-Rupture Behavior of Strands of an Organic Fiber/Epoxy Matrix
Authors: Chiao TT , Wells JE , Moore RL , Hamstad MA
Published: March 2009

The stress-rupture behavior of strands of an organic fiber impregnated with an epoxy matrix has been studied to evaluate the long-term performance of this class of composites. An increase in the applied stress of approximately 138 MN/m2 (20 ksi) reduces the life of the organic fiber/epoxy strands by a factor of 10. This rate of degradation is about one half that of the S-glass/epoxy composite under identical nonhostile environmental conditions. A three-parameter Weibull function can describe the stress-rupture behavior. A Weibull extrapolation of data from more than 400 tests implies that this material has a survival probability of 0.9 for ten years while sustaining an equivalent fiber stress of 2200 MN/m2 (320 ksi).
Methods of Fiber and Void Measurement in Graphite/Epoxy Composites
Authors: Cilley E , Roylance D , Schneider N
Published: March 2009

A variety of experimental procedures for measuring composite fiber and void content has been evaluated, including resin removal by sulfuric acid digestion, water takeup, and quantitative microscopy. These techniques were applied to a series of graphite/epoxy laminates; a comparison of the results showed the more convenient resin-removal method to be sufficiently precise unless spatial distributions of the constituents are required, in which case microscopy is indicated.
Effect of Salt Water and High-Temperature Exposure on Boron-Aluminum Composites
Authors: Dardi LE , Kreider KG
Published: March 2009

Boron-aluminum composites are being considered for aerospace applications, including jet engine fan blades and structural airframe components. The high specific modulus and strength of this material make it attractive in the design of these components while incorporating weight savings and increased structural efficiency. But two significant hostile environments are present that can jeopardize its outstanding properties; namely, enhanced corrosion in saltwater environments and high-temperature (air) exposures that are present in supersonic aircraft applications. This work was planned to identify critical properties that relate these environments to possible aerospace applications. In particular, the application of boron aluminum in jet engine fan blades was instrumental in the choice of experiment methods and analysis. Some of the findings in this investigation are summarized in the following.

Exposure of 2024 and 6061 matrix BORSIC + aluminum composites to synthetic sea salt spray at 95°F and 100 ksi bending stress results in matrix corrosion that is most severe with 2024 matrix material in the as-fabricated condition. Both 6061-F and 6061-T6 matrix composites exhibit general corrosion without preference for regions of high stress, whereas 2024-F and 2024-T6 matrix composites display depths of attack that are approximately twice as great on the tensile surfaces as the compressive surfaces. The flexural strengths of 6061-F and 6061-T6 matrix composites are unaffected by exposure for periods up to one month. The strength of BORSIC + 2024-F and BORSIC + 2024-T6 matrix composites can be reduced by as much as 100 percent and 14 percent, respectively, after one month as a result of matrix attack. The longitudinal strength of BORSIC filament is not degraded as a result of exposure to the humid salt environment.

The longitudinal strength of 61 v/o 5.7-mil BORSIC + 6061-F was degraded approximately 10 percent after 1000 h at 700°F. Transverse properties were unaffected. Uncoated 4.0-mil boron + 6061-F material exhibited a 12 percent decrease in longitudinal strength (175 × 103 psi to 154 × 103 psi) with the same exposure conditions. The transverse strength of this material was unaffected.

Although degradation of mechanical properties was achieved under these severe conditions, it is apparent that only the 2024 matrix alloy in saltwater exposure was found to be unsuitable for turbine engine fan blades.
Materials Parameters that Govern the Erosion Behavior of Polymeric Composites in Subsonic Rain Environments
Authors: Schmitt GF
Published: March 2009

The influence of materials construction variables on the erosion behavior of fiber-reinforced polymeric composite materials in subsonic rain environments is described. The void content and type of reinforcement are shown to significantly influence the behavior of fiber-reinforced composite structures in a subsonic rain erosion environment whether uncoated or coated. The effects of various fiber layup schemes with a particular fiber reinforcement have been found to be minor compared to void content effects. The addition of reinforcement to thermoplastic resin matrices increases the erosion rates of these materials by breakage of fibers and resulting loss of material. In thermosetting resins, the addition of reinforcement reduces the erosion rate of a bulk material by limiting the chunking and breakout of large pieces. Polymeric coatings such as epoxies, polyesters, and armde-imides are brittle relative to the impringing water droplets with rupture of the film occurring very rapidly. The most resistant coatings; that is, elastomeric polyurethanes, typically show no surface erosion at all but fail at isolated points associated with a breakdown of the composite (that is, glass-epoxy) underneath the coating. Other elastomeric coatings such as neoprene or fluorocarbon will gradually erode on the surface by structural failure or tearing within the film; erosion of the composite then follows.
Lightning Protection for Composites
Authors: Clark HT
Published: March 2009

The increasing use of composites for primary structural applications in advanced aircraft has necessitated the development of environmental protective systems. Since lightning strikes to boron/epoxy structural systems can cause catastrophic damage, the Air Force Materials Laboratory initiated a program [1]2 to evaluate and optimize a low-weight lightning protection system to protect boron/epoxy composite, full-depth honeycomb structure for advanced fighter aircraft. This paper summarizes the studies and major achievements of this program and includes results of the weight optimization studies and demonstration tests on large subcomponent beams (simulating advanced fighter empennage structure) and a flight-worthy composite component.
Torsional Fatigue Behavior of Unidirectional Resin Matrix Composites
Authors: Novak RC
Published: March 2009

Torsional fatigue data are presented for boron/epoxy and graphite/epoxy composites. The failure criterion for the tests is shear modulus reduction. The modulus reduction is shown to be caused by cracks that occur in resin-rich portions of the composites. Resistance to torsional fatigue is found to increase as fiber distribution becomes more uniform and as interfiber distance is decreased.
Interlaminar Shear Fatigue Characteristics of Fiber-Reinforced Composite Materials
Authors: Pipes RB
Published: March 2009

In this investigation the interlaminar shear fatigue characteristics of three composite materials are examined: graphite-epoxy (HTS), boron-epoxy (AVCO 5505), and glass-epoxy (3M 1002 S/ply). Thick-laminate, short-beam shear specimens instrumented with electrical resistance strain rosettes were subjected to constant-amplitude sinusoidal loadings (positive/positive, R = 0.1). Both residual strength and stiffness data are presented and trends in the fatigue life of these materials are established. The results of this preliminary investigation indicate that the fatigue characteristics of composite materials in the interlaminar modes differ significantly from fatigue characteristics in the fiber mode. While the residual strength of composite materials in the fiber mode has been shown to be only slightly reduced from the static strength after 106 cycles, the interlaminar shear strength is found to be diminished to approximately 50 percent of the static shear strength after 106 cycles. The shear stiffness, unlike the strength, is shown to be only slightly diminished over a 106 cycle lifetime. Finally, residual strengths are evaluated at 106 cycles for each material.
Evaluation of Graphite Fiber Reinforced Plastic Composites for Use in Unlubricated Sliding Bearings
Authors: Brown RD , Blackstone WR
Published: March 2009

Conforming shoe-type specimens of radial fiber graphite/epoxy, tangential fiber graphite/epoxy, and radial fiber graphite/polyimide were fabricated and evaluated as bearing materials. Their performance was compared against that of specimens cut from commercially available Teflon-lined (TFE-lined) bearings of MS 21240 type. All the test specimens were run against hardened steel sleeves. Test conditions included bearing loads ranging from 9 to 30 ksi (6.2 × 107 to 20.7 × 107 N/m2); oscillatory motion of ±25 deg at 30 or 60 cpm (0.5 or 1.0 Hz); equilibrium sleeve temperatures at the start of test ranging from 80 to 400°F (300 to 477 K); and test durations of 2 h except where earlier specimen failure occurred. Compressive strength and thermal conductivity measurements were also made on the graphite/epoxy materials.

At temperatures of 350°F (450 K) and lower, the TFE material exhibited the best friction and wear characteristics of the four materials tested. The graphite/polyimide material exhibited friction and wear performance superior to that of either of the graphite/epoxy materials over the range of conditions used. At combinations of high load and temperatures in excess of 350°F (450 K), the wear rate of graphite/polyimide material was comparable to that of the TFE material, although friction was higher.
The Notched Tensile Behavior of Metal Matrix Composites
Authors: Prewo KM
Published: March 2009

The deformation and fracture of boron-reinforced 6061 aluminum and Ti-6A1-4V were examined using X-radiography. Both monofilament and multifilament containing specimens were tested to determine operative fracture mechanisms. It was shown that three distinctly different types of composite behavior could each provide substantial notch insensitivity.
Comparison of the Mechanical Behavior of Filamentary Reinforced Aluminum and Titanium Alloys
Authors: Toth IJ
Published: March 2009

The tensile behavior, erosion/impact resistance, mechanical fatigue strength, thermal fatigue behavior, and creep strength of filamentary reinforced aluminum and titanium alloy matrix composites were briefly compared. Parallel to the filament direction, aluminum matrix composites are slightly stronger than titanium matrix composites up to a temperature of about 600°F (314°C). Titanium matrix composites, however, have shown significant off-axis strength advantage even at room temperature. B/SiC-Ti has shown a five-fold advantage in transverse strength over B-A1 at a test temperature of 500°F (260°C). The erosion rate of fiber-reinforced composites was found to be controlled by the matrix until the filaments became exposed. The titanium matrix, having an order-of-magnitude stronger matrix yield strength, exhibited greatly improved ballistic impact resistance, when compared to the aluminum matrix system. The low-cycle fatigue strength of titanium composite was superior to that of comparable aluminum composite. On the other hand the high-cycle fatigue strength in the 0 deg orientation for the titanium composite was significantly lower than that of a comparable aluminum composite. The resistance to thermal fatigue damage, when measured by tensile strength degradation, delamination, and dimensional distortion, was in favor of titanium composites. The transverse creep strength of B/SiC at 800°F (427°C) was shown to be ten times better than that of B/SiC-A1 at 575°F (302°C).
Tolerance of Advanced Composites to Ballistic Damage
Authors: Olster EF , Roy PA
Published: March 2009

The tolerance to ballistic impact of graphite/epoxy and boron/epoxy composites has been investigated. The effects of preload, of ply layups, and of projectile velocity have been examined for 30 caliber armor-piercing projectiles striking the plate at a 0 deg obliquity. A limited number of tests were performed on glass/epoxy laminates and on type 6061-T6 aluminum panels. Several tests were conducted using 50 caliber armor-piercing projectiles. High-speed photography was used to determine the overall ballistic response, as an additional check on projectile velocity, and to determine when crack initiation occurred. The fracture toughness of each type of laminate was determined and both the residual strength (the nominal stress to which a panel which did not fail during performation can be loaded) and the threshold strength (the lowest pre-impact stress which results in failure upon impact) are shown to correlate directly with the toughness.
Evaluation of the Toughness of Thick Medium-Strength Steels by Using Linear-Elastic Fracture Mechanics and Correlations Between KIc and Charpy V-Notch
Authors: Marandet B , Sanz G
Published: March 2009

Fracture toughness of medium strength steels (A533B, 2.25Cr-1Mo, electroslag welds, cast steels …) with different heat treatments was investigated by using big compact specimens.

The comparison of Charpy V and KIc transition curves shows that a very good correlation exists between the transition temperatures defined by these two tests. By defining TKIc as the temperature at which KIc = 100 Mpa√m and TK 28 as the temperature at which Charpy V-notch (CVN) = 28 J, the relationship is

TKIc = 9 + 1.37 TK 28 (°C)

The fact that the slope of this straight line is not one makes the existence of a direct correlation between KIc and CVN impossible. Nevertheless, this relationship may be used to predict accurately KIc from CVN. If one shifts the KIc versus temperature curves in order for TKIc and TK 28 to coincide, KIc and CVN are related by

KIc = 19 (KV)½(MPa√m, J)

Predicting KIc versus temperature curve from the Charpy V transition curve can thus be achieved in several steps.
Stress Intensities for Cracks Emanating from Pin-Loaded Holes
Authors: Smith CW , Jolles M , Peters WH
Published: March 2009

A series of stress freezing photoelastic experiments were conducted on large plates containing central holes with cracks emanating from the edge formed by the intersection of the hole with the plate surface. Loads were applied through rigid pins with neat fits in the holes. Stress-intensity factors (SIF) were estimated by a computer assisted least squares analysis of the photoelastic data taken from slices near the points of intersection of the flaw border with the hole boundary and the plate surface. Results indicate that the local mode of loading changes from Mode I near the hole boundary to mixed mode near the plate surface. The analysis is extended to include mixed mode loading, and results are compared with an existing approximate theory.
Effect of Specimen Size on J-Integral and Stress-Intensity Factor at the Onset of Crack Extension
Authors: Keller HP , Munz D
Published: March 2009

For a nickel-chromium-molybdenum steel and the aluminum alloy 7475, linear-elastic fracture mechanics can be applied to determine the stress-intensity factor at the onset of crack extension KIo for specimens with (W − a)c>0.4 (KIo/σy)2. For smaller specimens, KIo can be calculated from the J-integral JIo at the onset of crack extension, whereas linear-elastic fracture mechanics yield values which are too low. Below a minimum thickness B ≤ 50 JIo/σy an increase of Jo was observed.
Determination of Stress Intensities of Through-Cracks in a Plate Structure Under Uncertain Boundary Conditions by Means of Strain Gages
Authors: Kitagawa H , Ishikawa H
Published: March 2009

It is often required to determine the values of the stress-intensity factors at a tip of a given two-dimensional through-crack even when some of the boundary conditions are not exactly given.

A new method is proposed for determination of this kind of stress-intensity factor by combining experimental stress-analysis techniques, fracture mechanics, and variational methods.

In this paper, the stresses on the boundary of a small domain surrounding a crack tip were measured by electric resistance strain gages, and the stress-intensity factors were calculated by variational method. Sufficient accuracy was obtained. For convenience of applications, a method by means of a calculating table was proposed.
Experimental Verification of the JIc and Equivalent Energy Methods for the Evaluation of the Fracture Toughness of Steels
Authors: Marandet B , Sanz G
Published: March 2009

The critical value JIc and the apparent fracture toughness KBd are measured with a single small specimen (compact tension or three-point-bend bar) loaded in the elastic-plastic range. Initiation is detected during loading by an electrical potential method.

For the steels studied here (2.25Cr-1Mo, electroslag weld, manganese cast steel), the KIc values deduced from JIc are in agreement with the KIc values directly measured with thick specimens in the transition-temperature range. Furthermore, the equivalent energy procedure gives the same results as those obtained by the J-integral method.
Diameter Increases in Steam Generating Heavy Water Reactor Zircaloy Cans under Loss-of-Coolant Accident Conditions
Authors: Rose KM , Hindle ED
Published: March 2009

In the steam generating heavy water reactor (SGHWR) the fuel rod temperature rise following a loss-of-coolant accident (LOCA) is controlled by a water spray from within the rod bundle. To allow this emergency water spray to operate as intended, the fuel rod cladding diameter increase during the LOCA is kept to less than 5 percent. This gives rise to the need for a means of estimating the diameter increase of cans during temperature excursions up to 1200°C under varying internal pressure. The Water Reactor Fuel Can Swelling (CANSWEL) code has been developed for this purpose, and there are well known codes available which deal with the CANadian Deuterium Uranium (CANDU) and light water (LW) reactors. The CANSWEL code satisfactorily predicts the can diameter increase in conditions where the absorption of oxygen by zirconium does not affect the result significantly but does not deal yet with exposure to high temperature in steam. This paper describes simple equations which represent the behavior of Zircaloy-2 cans below the transformation temperature and in the β-phase in the absence of oxygen. It goes on to consider some phenomena which cause the β-phase equation to be modified when the diameter increase occurs in steam.
Superplasticity of Zircaloy-4
Authors: Boček M , Hofmann P , Petersen C
Published: March 2009

The plastic behavior of Zircaloy-4 (Zry-4) sheet specimens is examined by tension testing in air atmosphere at temperatures between 750 and 1050°C at cross-head speeds ranging over three orders of magnitude. The basic dependencies of the strain rate sensitivity index, m, upon temperature, strain rate, strain, and anisotropy are reported. Information about the grain structure behavior during superplastic (SPL) flow was obtained from metallographic, electron microscopic, and texture examinations, respectively. Microstructural examinations have brought convincing evidence that in the (α + β)-phase region α-grain switching is the dominating deformation mode in SPL flow at lower strains.
Oxidation of Zirconium During a High-Temperature Transient
Authors: Sawatzky A , Ledoux GA , Jones S
Published: March 2009

A physical model describing oxidation and oxygen diffusion under non-isothermal conditions is presented. It assumes (a) equilibrium at phase interfaces, as is usual in the treatment of diffusion, and (b) oxygen supersaturation of the β-zirconium to precipitate α-zirconium on cooling. An important consideration, not required in isothermal diffusion, is that the equilibrium oxygen concentrations in the α- and β-phases decrease with temperature.

During isothermal oxidation at temperatures above 850°C, the phase distribution is zirconium dioxide (ZrO2/α/β. This model predicts that on slow cooling, oxygen in the β-region diffuses to the α/β interface leading to a depletion of oxygen in this region with a corresponding increase in the thickness of the α-layer. With more rapid cooling, α-zirconium is precipitated in the β-region near the α/β interface. The oxygen concentration of the β-region is determined not by the maximum temperature in the transient but by the lowest temperature at which appreciable diffusion is still possible.
Zircaloy Cladding Behavior During Irradiation Tests Under Power-Cooling-Mismatch Conditions
Authors: Hobbins RR , Smolik GR , Gibson GW
Published: March 2009

The behavior of Zircaloy-clad fuel rods for light water reactors under off-normal operating conditions is being studied in the Power Burst Facility. Fuel rods from three irradiation experiments conducted under power-cooling-mismatch conditions have been examined destructively in remote handling facilities. The postirradiation examinations of these pressurized water reactor-type rods have included visual and photographic examination, physical dimensioning, and metallography.

The examinations have revealed the collapse of the Zircaloy cladding onto the fuel pellets and into the gaps between pellets (waisting) of these fuel rods. In some cases, severe oxidation on the external surface of the cladding from Zircaloy-steam reaction and on the internal surface from Zircaloy-uranium dioxide (Zr-UO2) reaction caused embrittlement of the cladding which resulted in cladding cracking and fuel rod fracture.

Cladding temperatures were estimated from the microstructures using a correlation between temperature, time, and the combined thickness of the zirconium dioxide (ZrO2) and oxygen-stabilized alpha layers. Using this method, cladding temperatures up to 1640 K have been estimated on the fuel rods tested.

Cladding collapse occurred at temperatures estimated to be in the range of 1020 to 1170 K. The reactor coolant system pressure was 14.5 to 15.2 MPa and the rods were prepressurized to pressures within the range 2.6 to 3.8 MPa.
Corrosion Monitoring of Steam Generating Heavy Water Reactor Pressure Tubes
Authors: Sheppard MF , Tyzack C
Published: March 2009

The corrosion of zirconium alloys under boiling water reactor (BWR) conditions is enhanced by irradiation; therefore, it was necessary to verify the expected behavior in steam generating heavy water reactor (SGHWR) of pressure tabes manufactured by different routes. Specimens of each material and others of interest were exposed to the coolant inside perforated fuel cans replacing fuel pins in otherwise standard SGHWR fuel clusters. After irradiation, specimens were decrudded chemically and weight gains were measured. Hydrogen pick-up was found by hot vacuum degassing. Specimens were also examined metallographically.

Weight gains from irradiations up to 531 effective full-power days (EFPD) generally show a reasonably linear correlation with the fast fluence to which they have been exposed. There is a variation in corrosion rate between Zircaloy-2 materials of different histories; a quench treatment at the billet stage seems to be beneficial. Metallographic examination of specimens and fuel cladding showed the presence of nodular corrosion after exposure ia reactor in oxygenated water. The extent of nodular formation varied with material and generally followed the weight gain patterns. The paper includes a discussion on mechanistic aspects of nodular corrosion.

Hydrogen up-take by the specimens appears to be largely independent of corrosion weight gain making percentage pick-up figures of dubious value. The amounts of hydrogen taken-up, however, are small, representing less than 5 percent for many materials. Extrapolation of results to the expected full reactor life indicates that neither loss of section by corrosion nor hydrogen pick-up by the pressure tube should be life limiting.
Numerical Model for the Anisotropic Creep of Zircaloy
Authors: Franklin DG , Franz WA
Published: March 2009

A model that considers slip to occur on prism planes in hexagonal close packed (hcp) polycrystalline materials is used to determine anisotropic creep rates. The model uses basal pole figures to determine the orientation of individual grains and incorporates certain flow rules to predict creep rates in any direction for any applied stress state. Three combinations of two slip systems, one of which is taken as prism slip, are investigated. A computer code that performs the calculations is described and is used to, determine constants for a phenomenological creep description. The results of this model are compared to available experimental results on the creep of zirconium alloys and are used to study the ovalization of Zircaloy tubes during irradiation.
Susceptibility of Zirconium Alloys to Delayed Hydrogen Cracking
Authors: Coleman CE , Ambler JFR
Published: March 2009

Smooth and notched cantilever beams and round-notched bars were machined from pressure tubes of cold-worked Zr-2.5Nb and Zircaloy-2. They were loaded in the temperature range 290 to 520 K. After two thermal cycles and at high stress, cracks were initiated in smooth beams of cold-worked Zr-2.5Nb. Under the same test conditions, cold-worked Zircaloy-2 plastically deformed with no cracking. When notches were present, cracks propagated at the same rate in both materials by delayed hydrogen cracking. In cold-worked Zr-2.5Nb, the crack velocity followed an Arrhenius plot with an apparent activation energy of 42 kJ/mol. Below 420 K, the threshold stress intensity factor for delayed hydrogen cracking was about 5 MPa m. Therefore, cracking can be prevented by keeping tensile stresses very low.
A Comparison of Two Methods for Estimating the Parameters of a Truncated Normal Distribution
Authors: Hansen J , Zeger S
Published: March 2009

The lognormal distribution has been used as a model for species abundance. A historical review of the use of this model is given. The method of maximum likelihood described by Cohen (1959, 1961) and a nonlinear regression method developed by Gauch and Chase (1974) have been used to estimate the parameters of the model. These two methods are described and appropriate applications of each method are discussed. The maximum likelihood method, not the nonlinear regression, is appropriate for estimating the parameters of this species abundance model. Results of a Monte Carlo simulation which demonstrates the advantage of maximum likelihood are presented.
A Statistical Technique for Analyzing Time-Response Curves
Authors: Capizzi T , Burton DT
Published: March 2009

A statistical technique useful in the analysis of experiments involving time-response curves is presented. This procedure, known as growth curves analysis, uses the techniques of multivariate linear models to estimate parameters and test hypotheses. Examples of experimental designs to which this procedure can be applied and a worked out example are presented.
Use of Rarefaction and Related Methods in Ecology
Authors: Simberloff D
Published: March 2009

Rarefaction is a statistical technique useful in both pollution and evolutionary ecology. It can be used to infer whether samples are drawn from the same community and also to estimate minimum feasible sample size. In this setting it essentially tells the investigator what would have been found had sample size been smaller, but some surprising uses arise if questions are phrased properly. Rarefaction is most powerful in pollution ecology when entire curves, and not just single values, are calculated. In evolutionary ecology, species/genus and related ratios have been examined as an indicator of both competition and adaptive radiation, but rarefaction demonstrates that the former, at least, is rarely evidenced by such ratios. The ratios are largely determined by the number of species, and claimed relationships between the ratios and area are primarily artifacts of the high correlation between the ratios and species number. The analytic expressions for expectation and variance in rarefied samples and a FORTRAN IV program for their calculation are given.
Generation and Measurement of Shear Waves In Situ
Authors: Hoar RJ , Stokoe KH
Published: March 2009

Field procedures used to measure in situ shear wave velocity by cross-hole and downhole seismic methods are presented along with typical travel time records. Identification of the initial shear wave arrival is enhanced by use of a reversible torsional source in the crosshole method and a reversible embedded source in the downhole method. Correct triggering of recording equipment is critical in these measurements. Characteristics of three triggering systems—a velocity transducer, a resistance-capacitance (RC) circuit, and an electrical step trigger—are presented. Incorrect triggering can cause errors greater than 50 percent in field measurement of shear wave velocity. Other variables such as borehole casing, borehole disturbance, and source and sensor configuration also affect velocity measurement. The effects of many of the variables can be minimized by basing wave velocity computations on interval travel times of the initial arrival. It is recommended that any ASTM standards for crosshole and downhole seismic methods include field check procedures for correct timing and triggering of recording equipment and field measurement of borehole verticality.
Shear Modulus: A Time-Dependent Soil Property
Authors: Anderson DG , Stokoe KH
Published: March 2009

Dynamic shear moduli determined at low shearing strain amplitudes (<10-3 percent) during sustained-pressure, resonant-column tests are shown to increase with time of confinement. The time-dependent modulus increase is characterized by two phases: (1) an initial phase which results from primary consolidation, and (2) a second phase which occurs after completion of primary consolidation, called the “long-term time effect.” The duration of primary consolidation and the magnitude of the long-term time effect vary with factors such as soil type and stress conditions. Although shapes of the modulus-time relationships differ depending on whether the soil is primarily fine- or coarse-grained, all soils exhibit a long-term time effect. The long-term time effect is also shown to occur at higher shearing strains (0.001 to 0.1 percent) for moduli determined at the onset of cyclic loading. On the basis of these results, confinement time is shown to be an important parameter which must be properly accounted for in the laboratory measurement of shear moduli and which must be considered when interpreting laboratory moduli in terms of in situ response.
Modulus and Damping of Soils by the Resonant-Column Method
Authors: Drnevich VP , Hardin BO , Shippy DJ
Published: March 2009

The resonant-column method, a relatively nondestructive test employing wave propagation in cylindrical specimens, is used to obtain modulus and damping of soils as functions of vibratory strain amplitude and other factors such as ambient confining stress and void ratio. Descriptions of the apparatus, calibration procedures, testing procedures, and aids for data reduction are given for apparatus which propagate either rod compression waves or shear waves or both. Data reduction aids include graphs for a wide range of apparatus conditions and include a computer program that covers all admissable boundary conditions.
Effects of Time on Damping Ratio of Clays
Authors: Marcuson WF , Wahls HE
Published: March 2009

Laboratory tests with a Hardin oscillator were used to study the time-dependent characteristics of the damping ratio of isotropically consolidated specimens of kaolinite and calcium bentonite. Damping was determined using a steady-state method and from the decay of free vibrations. After completion of primary consolidation, the dynamic response was studied as a function of time for both drained and undrained conditions.

The damping ratio decreased approximately 12 percent for kaolinite and 25 percent for bentonite per logarithmic cycle of a dimensionless time ratio during secondary compression. To evaluate the effects of time in clay soils, at least one test should be continued to five to ten times the time at the end of primary consolidation.

Errors due to diffusion of air into the specimen were eliminated by using a mercury jacket around the specimen. The apparatus damping constant was found to vary significantly from test to test because of minor variations in the apparatus setup, and hence the apparatus must be recalibrated for each test.
Dynamic Properties of Mass Concrete
Authors: Saucier KL , Carpenter L
Published: March 2009

The objective of this study was to determine the tensile strength, cyclical behavior, and stress-strain relationships for concrete under loading conditions ( 1 to 10 Hz) such as could be produced by an earthquake.

Dynamic direct tension tests and stress-reversal tests were conducted on core specimens from two concrete mixtures representative of mass concrete. Test procedures were developed for cyclical loading and loading to failure in 0.25 to 0.025 s, which represent one fourth of a cycle having a frequency of 1 to 10 Hz. Stress-strain measurements were made on selected specimens. The procedures used could be modified to become ASTM test methods for direct-tension and stress-reversal tests of rock.

The tests indicated that there was no significant difference in tensile strength determined statically or dynamically on dry specimens. A 30 percent increase in strength was indicated for wet specimens tested dynamically. Very little hysteresis was evident in the tensile stress-strain curves. The results should be useful in studies conducted to determine the earthquake resistance of mass-concrete structures.
Resonant-Column Testing—Problems and Solutions
Authors: Drnevich VP
Published: March 2009

The resonant-column test is a relatively nondestructive test employing wave propagation in cylindrical specimens of soil and rock. Test results are usually quite accurate, but in some cases insufficient coupling exists between specimen and apparatus or specimens are too stiff for a given apparatus, or both. A criterion is given to evaluate whether a coupling problem exists and solutions are suggested. Procedures for evaluating limiting specimen stiffness and maximum strain amplitude capabilities are given. Solutions for reducing air migration problems during long-term tests are presented. Finally, a simple method for estimating strain amplitudes during a test is demonstrated for both shear and axial compression.
Toxicity Testing in the United Kingdom for the Evaluation of Oil Slick Dispersants
Authors: Norton MG , Franklin FL , Blackman RAA
Published: March 2009

Until recently, the toxicity of dispersants approved for use in U.K. waters was evaluated by a static bioassay on the dispersant alone.

Following the 1974 Dumping at Sea Act, dispersant evaluation methods were reviewed and dispersants are now licensed for sea (offshore) or for beach use, based on two tests to assess the environmental effect of the dispersant use.

The “sea” test assesses the toxicity to Crangon crangon of a chemically dispersed oil and compares it with the toxicity of the oil alone. Mortality is measured over a period of 100 min at an oil concentration of 1000 ppm.

The “beach” test assesses the toxicity of the dispersant alone to a typical intertidal organism, Patella vulgata, by spraying with dispersant and rinsing in a simulated tidal cycle. Mortalities are measured after 72 h and compared with those of an oil control.

The rationale behind the development of these tests is described, together with the experimental results. The U.K. criteria for licensing products on the basis of these test results are also discussed.
Some Guidelines for Oil-Spill Control in Coastal Environments, Based on Field Studies of Four Oil Spills
Authors: Gundlach ER , Hayes MO , Ruby CH , Ward LG , Blount AE , Fischer IA , Stein RJ
Published: March 2009

It is essential to understand the factors influencing the distribution, damage and long-term persistence of oil spills in order to adequately plan for, and apply appropriate cleanup techniques. Based on the study of two massive spills [Metula, 47 700 t (53 000 tons)]; [Urquiola, 22 500 to 27 000 t (25 000 to 30 000 tons)] and two smaller spills under ice conditions [Bouchard 65, 248 t (276 tons); Ethel H., 1350 t (1500 tons)], these factors are (1) wind stress and water currents, (2) beach activity and grain size, (3) tidal stage, (4) wave energy, (5) oil quantity and composition, and (6) ice effects, where applicable.

Coastal environments vary significantly in terms of resultant damage from spilled oil. Subsequent cleanup by dispersants or mechanical means should be planned accordingly. Considering the aforementioned factors, as well as initial biological effects, a classification of coastal environments in terms of potential oil spill damage has been developed. In order of increasing vulnerability, these environments are: (1) exposed, steeply dipping or cliffed rocky shores; (2) eroding wave-cut platforms; (3) fine-sand beaches; (4) coarse-sand beaches; (5) exposed, compacted tidal flats; (6) mixed sand and gravel beaches; (7) gravel beaches; (8) sheltered rocky coasts; (9) sheltered tidal flats; and (10) salt marshes and mangroves. This classification can be used to delineate oil-sensitive environments as part of an overall contingency plan to limit damage during an oil spill.
Dispersant Usage for Offshore Oil Spills
Authors: Coit RA
Published: March 2009

In some situations the use of dispersants to control marine oil spills is environmentally desirable and is an accepted practice in many areas of the world. In the United States the use of dispersants has historically (1967) been discouraged by Federal regulation, due primarily to the early concern over the use of some toxic dispersants. Since 1967 it has become very apparent that the use of low-toxicity dispersants to control oil spills may be the most environmentally sound control approach in offshore areas, particularly when an oil spill may approach a sensitive coastline. A task force was appointed over a year ago by the American Petroleum Institute to make recommendations on the utilization of dispersants based on studies of current information on dispersants and mechanical recovery equipment. The task force believes that the use of low-toxicity dispersants should be encouraged where it is justified, specifically when it would be the most effective and biologically sound method of controlling an offshore oil spill. For this reason the National Contingency Plan should be revised so that the responsible on-scene coordinator (OSC) has authority over the use of dispersants. The OSC should be able to decide to use dispersants, as part of preplanned contingency plan implementations, to control offshore oil spills that threaten to move into sensitive environmental areas.
Apparatus for Application of Chemical Dispersants on Open Sea
Authors: Allen TE
Published: March 2009

A chemical dispersant spraying system for use on seagoing workboats has been developed. Using two spray booms, the system can spray a path up to 18.3 m (60 ft) wide at a speed of 8 knots, thus covering approximately 0.27 km2/h (67 acres per hour). The design is based on the use of “self-mix surfactant,” which requires little mixing energy for effective dispersion of the oil slick. Three of these systems have been completed for Clean Atlantic Associates, an oil spill cleanup cooperative.

The system is made up of an apparatus for deploying and supporting two 9.1-m (30 ft) spray booms, a 33.6-kW (45 hp) pump skid for pumping a mixture of seawater and dispersant, and Marine Portable 1892.5 litre (500 gal) tankage for storing the dispersant.

The spray apparatus is designed to be attached to the bow of the boat. This allows the boom to spray the mixture of seawater and dispersant ahead of the bow wake. Subsequent mixing energy is provided by the bow wake. When not using a self-mix dispersant, additional mixing energy can be provided by breaker boards; however, these are not included in this system.

Seawater is drawn from an overboard suction line, proportioned with the chemical dispersant at a typical ratio of 33 to 1, and pumped at high pressure, 0.62 to 0.69 N/m2 (90 to 100 psi), through fan-type nozzles.

The entire system is readily adaptable to various sizes and shapes of vessels, and operates independently of the vessel to which it is mounted.
Thermal Conductivity Measurements on High-Temperature Fibrous Insulations by the Hot-Wire Method
Authors: Jackson AJ , Adams J , Millar RC
Published: March 2009

We have developed equipment to determine the “thermal conductivity” of insulating materials, in the temperature range 25° to 1600°C, by the hot-wire method. We have based our method on the German draft standard DIN 51046 and on the work of Padgett and Davis at the British Ceramic Research Association (BCRA). The method has been applied to measurements on polycrystalline alumina fibers, where the “thermal conductivities” range from 0.03 to 0.8 W/m-K. This paper gives details of our experiences with the hot-wire method and indicates some areas where we have found difficulties that are not completely covered in the specification.

In order to assess the value of “thermal conductivity” data obtained by the hot-wire method, we have, where possible, tried to compare our results with those obtained by parallel-plate methods. The dangers of making such a comparison are indicated, but the agreement between the results obtained by the two different methods gives us confidence in their reliability for insulation design.
Laboratory and Field Investigations of Moisture Absorption and Its Effect on Thermal Performance of Various Insulations
Authors: Dechow FJ , Epstein KA
Published: March 2009

Much work has been done in Europe, Canada, and the United States with respect to the effect of moisture on the thermal efficiency of various insulations. However, very little research has been done to orient the laboratory test methods to the actual field conditions in which the various insulations will be used.

This paper reports on the moisture performance characteristics of various thermal insulations under laboratory conditions and under actual field conditions. The various moisture effects, such as freeze-thaw cycling in the presence of water, water absorption, and water vapor transmission, which occur in insulations in upside-down roof systems and below-grade applications, reduced the thermal efficiency of all insulations tested. This loss of thermal resistance of the common insulating materials using both laboratory methods and field data is related to the volume of water present in the insulations. The minimum performance criteria for insulations exposed to the various laboratory test methods and to actual field conditions are also discussed. The insulations investigated include fiber glass, fiberboard, expanded (bead) polystyrene, extruded polystyrene, polyurethanes, and cellular glass. The effect of various top coverings for upside-down roof applications on the thermal resistance performance of insulations is also discussed.
A Calibrated/Guarded Hot-Box Test Facility
Authors: Miller RG , Perrine EL , Linehan PW
Published: March 2009

A hot-box test facility was fabricated by Wiss, Janney, Elstner and Associates for Jim Walter Research Corp. The equipment is capable of operating in either a calibrated or a guarded mode. When operating in the guarded hot-box mode, the equipment is in accordance with the ASTM Test for Thermal Conductance and Transmission of Built-Up Sections by Means of the Guarded Hot Box (C 236-66). When operating in the calibrated hot-box mode, the equipment is in accordance with the proposed ASTM Test for Thermal Performance of Building Assemblies by Means of a Calibrated Hot Box, which is presently being written by ASTM Subcommittee C16.30 and for which input has been provided from this facility. The basic design consists of a separate cold box, hot box, specimen frames, refrigeration unit, control and data-acquisition panel, and metered box. Both the hot and cold boxes are insulated with low-density polyurethane foam, with an overall minimum thickness of 30.5 cm (12 in.). The attitude of the test facility can be varied to provide upward, downward, or horizontal heat flow. Both the hot and cold boxes can provide variable air velocities parallel to the specimen face.

The following is a summary of the operating characteristics of the test facility:

Test specimen area dimensions: 2.4 by 2.4 m (8 by 8 ft)

Guarded mode metering area: 1.8 by 1.8 m (6 by 6 ft)

Cold side: normal temperature range: 27 to -23°C (80 to - 10°F) special temperature range: to -46°C (to -50°F) air velocity: 0.8 to 24 km/h (0.5 to 15 mph)

Hot side: temperature range: 2 to 71°C (35 to 160°F) air velocity: 0.8 to 24 km/h (0.5 to 15 mph)
A Calibrated Hot-Box Approach for Steady-State Heat-Transfer Measurements in Air Duct Systems
Authors: Lauvray TL
Published: March 2009

The paper describes a procedure for measurement of steady-state heat transfer through the walls of air duct systems under actual operating conditions and configuration. The procedure uses two independent measurement techniques. A calibrated hot box is the primary measurement technique and an airstream temperature-drop measurement provides a secondary technique.

The calibrated hot box is a heavily insulated box which is sealed around a duct conveying cold air. A temperature controller and electric resistance heaters maintain the box temperature as close as possible to ambient temperature. Thus, the laboratory space acts as a guard for the box. The energy input to the box is measured with a watt-hour meter. The total energy input, corrected for the heat transfer through the box wall, represents the heat transfer through the test system.

The temperature-drop technique uses thermocouples to measure the temperature difference betweeen two stations in the test duct and orifice plates to measure airflow. The heat transfer from this technique is compared with calibrated hot-box measurements.

An automatic data collection system is used so that tests can be conducted over a long period of time to assure steady-state conditions and to determine reproducibility.

Verification of the calibrated hot-box technique is achieved by testing a specially constructed section of duct whose heat transfer can be readily calculated. Experimental and calculated data are presented for this duct section.
Forced Convection: Practical Thermal Conductivity in an Insulated Structure Under the Influence of Workmanship and Wind
Authors: Bankvall CG
Published: March 2009

This paper describes the practical heat resistance in an insulated wall structure as influenced by workmanship and forced convection. Experimental investigations of crossbar walls are compared with calculations. Examples show the influence of heat resistance of insulation installation, airflow along the insulation, and airflow through the insulation. Full information on theoretical calculations and experimental investigations can be found in footnote 2.