bluuebunny/crossref_metadata_2025 huggingface dataset:
Effects of Undercoats and Overcoats on Damage Thresholds of 248 nm Coatings
Authors: Tuttle Hart T , Lichtenstein TL , Carniglia CK , Rainer F
Published: March 2009

Previous experiments have demonstrated that 1064 nm high reflectors benefit from the addition of halfwave silica overcoats, and that 1064 nm antireflection coatings can be improved by adding halfwave silica undercoats or barrier layers. In each case, a statistical improvement of about 50% has been observed. This paper reports similar results for coatings designed for 248 nm. The high reflectors were scandia/magnesium fluoride quarterwave stacks. Three design variations were tested: with no overcoat, with a halfwave silica overcoat, and with a halfwave magnesium fluoride overcoat. The presence of the overcoat more than doubled the threshold of the reflectors. The highest threshold, 8.5 joules/sq.cm, was measured on a reflector with a magnesium fluoride overcoat. Two material combinations were used for the four-layer antireflection coatings: scandia/silica and scandia/magnesium fluoride. Each of these combinations was coated without a barrier layer, with a silica barrier layer, and with a magnesium fluoride barrier layer. The barrier layer was an undercoat with a halfwave optical thickness. Varying degrees of improvement in thresholds, ranging up to 50%, were found in all cases with barrier layers. The highest thresholds exceeded 6 joules/sq.cm for scandia/silica coatings with silica barrier layers.
Sensitive Technique for Measuring Apparent Optical Figure Error Caused by Coating Nonuniformity
Authors: Bennett HE , Burge DK
Published: March 2009

If a diffraction-limited wave front is to be produced by an optical train, the requirements on the optical figure of individual mirror components may be very stringent. Peak-to-valley values of λ/8 visible equivalent are found for some infrared systems, λ/20 for visible systems, and λ/100 visible equivalent has been suggested for some ultraviolet systems. These mirrors often have high reflectance multilayer coatings, in which case the optical figure is determined not only by the geometrical perfection of the optical surface but also by the uniformity of the multilayer coating. Although this uniformity can be determined interferometrically or by measuring the secondary structure surrounding the reflectance maxima, the most sensitive technique for determining film nonuniformities appears to be ellipsometry. It should be performed at the wavelength at which the mirror is to be used. Typically, the ellipsometric parameter Δ is found to be very sensitive to variations in film thickness but quite insensitive to absorption in the film; the converse holds for Ψ. For a representative infrared, high reflectance multilayer coating, a measurable change in Δ corresponds to film thickness nonuniformities of less than 0.01%, and a measurable change in Ψ corresponds to a change in peak reflectance of 0.001. An automated ellipsometer could be readily used to scan the surface of even a large mirror. Ellipsometry may thus provide the optimum technique for testing mirror optics for multilayer-film-induced changes in apparent optical figure. It also provides a sensitive technique for measuring the uniformity of reflectance of large, multilayer-coated mirrors.
Selective and Uniform Laser-Induced Failure of Antireflection-Coated LiNbO3 Surfaces
Authors: Seitel SC , Franck JB , Marrs CD , Dancy JH , Faith WN , Williams GD
Published: March 2009

LiNbO3 surfaces with different antireflection coatings and from different vendors were damaged with 1.06-μm, 9.5-ns full width at half maximum laser pulses. By probing with a laser spot smaller than the separation of isolated surface defects, it was possible to separate uniform damage, which was characteristic of the coating itself, from premature, defect-driven, localized failures. Uniform failure modes were identified and thresholds extracted for each by multithreshold analysis. Frequency of defect damage was determined at several fluences much lower than required for uniform failure. It is likely that defect-driven selective failures reduce the apparent damage threshold of flood-loaded samples. Tentative identification of a selective damage threshold was made and correlated with large-spot, multimode test results. Incorporation of these results into a product-improvement program has resulted in LiNbO3 Q-switches with increased resistance to selective damage.
Studies of Diamond-Like Carbon Coatings for Protection of Optical Components
Authors: Stein ML , Aisenberg S , Bendow B
Published: March 2009

Ion-deposited diamond-like carbon is a promising candidate for thin protective coatings for optical components. Our recent studies have been directed to ascertaining several key properties of the coating, and verifying its protective nature.

Tests performed on coated discs of CaF2 indicated improved resistance to environmental attack by acids, bases, and solvents. Hermeticity was corroberated by comparing the effects of HF-acid on coated and uncoated surfaces. The tenacity to substrates such as glass and CaF2 was demonstrated by the difficulty to remove the coating with standard techniques, such as exposure to HF and water. Also, a marked decrease in abrasion was found (by measuring forward optical scatter) for the coated portion of a disc.

Optical measurements performed on these coated discs indicated that the coating neither significantly decreased transmission as measured from 2 to 6 microns, nor induced visible scatter. High resolution scanning and transmission electron micrograph studies indicate that the films are partly amorphous with a partial ordering of carbon atoms; while Raman studies indicated both graphite as well as microcrystalline diamond-type behavior. ESCA studies indicated a C to CaF2 gradient throughout the coating indicative of ion implantation. Thickness determinations were made by substrate dissolution and surface profile measurements.
Preliminary Experimental Results of Spot Size Scaling in Laser Induced Damage to Optical Coatings
Authors: Stewart AF , Guenther AH
Published: March 2009

The laser damage threshold of various thin film coatings has been assessed using 1.06 μm radiation at a pulse length of 6ns FWHM. Samples of conventional coatings of several materials have been tested as a function of film thickness and spot size. Beam diameters employed range from approximately 9μm and larger.

From these preliminary data, previously observed scaling has been verified, i.e., thinner films are more damage resistant, while smaller spot sizes yield higher damage thresholds, as expected. The samples employed in these tests were conventional coatings of ThF4, ZrO2 and HfO2 as well as specially prepared “Low defect” coatings of Cerac and RAP grown ThF4. These “low defect” coatings are initial efforts and unfortunately showed no advantage over conventional coatings in terms of damage threshold.
Quantum Theory of Multiphoton Free Carrier Absorption At High Intensities in Compound Semiconductors
Authors: Jensen B
Published: March 2009

Multiphoton absorption and emission, accompanied by scattering of free carriers in an intense radiation field, is treated by an extension of the theory of one photon free carrier absorption in polar semiconductors. The rate equation for m photon absorption, where m is a positive integer, is obtained from the equation of motion of the quantum density matrix. It is shown to be proportional to the mth power of the radiation intensity. The effect of the field on the electron during scattering is taken into account by using the exact wavefunctions of an electron in an intense radiation field in the calculation of the transition matrix elements. An expression for the average Joule heating per electron is found. A comparison with earlier treatments is given.
Nonlinear Absorption and Self-Defocusing of Intense IR-Laser Radiation in Semiconductors Due to Generation of Free Carriers
Authors: Danileiko YK , Lebedeva TP , Manenkov AA , Sidorin AV
Published: March 2009

Results of experimental studies of the interaction of high power CO2 (λ = 10.6 μm), CaF Er3+ (λ = 2.76 μm) and YAG Er3+ (λ = 2.96 μm) lasers with undoped Ge and Si are presented. The experiments included photoconductivity, microwave absorption and laser beam transmission measurements at various intensities up to the level of laser damage. For both the Ge and Si samples, nonequilibrium carrier generation has been observed with both CO2 and Er-laser excitation.

It is shown that the carrier generation in Ge is due to two-photon ionization at the Er-laser wavelength, whereas none of the considered mechanisms (impact, multiphoton and thermal ionizations), explain the anomalous dependence of carrier density upon CO2-laser excitation intensity.

Nonequilibrium carrier generation results in nonlinear absorption and self-defocusing, which in turn lead to the intensity saturation of high power laser beams. Analysis of these effects for prefocused beams is presented. It is shown, in particular, that the absence of bulk damage in Ge under CO2 and Er-laser radiation is attributed to these effects even at very high incident intensities. It is pointed out that these effects play an important role in the application of Ge as a material for use in high power IR lasers.
Discontinuous Extension of Fracture in Elastic-Plastic Deformation Field
Authors: Wnuk MP
Published: March 2009

A procedure is developed whereby slow crack growth can be analyzed, and predictions are made regarding the transition from stable to spontaneous fracture in solids which are not susceptible to the linear elastic fracture mechanics formalism. Emphasis is placed on discerning the limit modes of fracture: cleavage versus tearing. These two extremes of material behavior, a very brittle one and a very ductile one, are described as certain limiting cases resulting from a single mathematical model. Certain numerical examples involving microstructural parameters are given to illustrate the use of the newly introduced quantities in analysis and in data reduction pertaining to the early stages of fracture.
Elastic-Plastic Steady Crack Growth in Plane Stress
Authors: Dean RH
Published: March 2009

Results are presented for a crack which is growing quasi-statically under plane-stress conditions. Crack-tip stress and strain fields have been computed by the finite-element method for a crack which is propagating steadily with symmetric small-scale yielding boundary loads (Mode I). The analysis assumes that the material is a standard J2-flow theory elastic-plastic solid exhibiting isotropic-hardening behavior. Results are discussed for various levels of material hardening.
Evaluation of Plate Specimens Containing Surface Flaws Using J-Integral Methods
Authors: Reuter WG , Chung DT , Eiholzer CR
Published: March 2009

Using annealed Type 304 stainless steel plate specimens containing ellipsoidal, rectangular, or triangular-shaped surface flaws, critical values of J are calculated for three separate situations: (1) the assumption that the specimen consists of a single-edge notch (SEN) and two unflawed specimens, (2) the prediction of an equivalent-length through-thickness defect for the surface flaw, and (3) the use of an equation developed by Paris. It was concluded that Jinit (Charpy specimen) and JIc cannot be used to successfully predict structural integrity using any of the three approaches for the 6.4-mm-thick (0.25-in.) annealed Type 304 stainless steel.

Since it was not possible to develop a comparison between the absolute values of Jinit (from the surface-flawed specimen) and JIc, an attempt was made to evaluate a possible relative agreement. Values of Jinit and Jpen from only those specimens containing rectangular-shaped defects were used to calculate ΔJ/Δα. The average values agree reasonably well with those obtained in the open literature.
Steady-State Crack Growth in Elastic Power-Law Creeping Materials
Authors: Hui CY
Published: March 2009

The problem of a quasi-statically growing crack in an elastic power-law creeping material is considered for the case of plane-strain Mode I under small-scale yielding conditions. A finite-element method is used to compute the complete stress and strain field. A crack growth criterion is used to derive a relation between the crack growth rate ˙a and the stress-intensity factor K.
Dynamic Growth of an Antiplane Shear Crack in a Rate-Sensitive Elastic-Plastic Material
Authors: Freund LB , Douglas AS
Published: March 2009

A numerical study of the dynamic steady-state antiplane shear (Mode III) crack growth process is described. The study is based on continuum mechanics, and the material is modeled as being elastic-viscoplastic. Using the small-scale yielding concept of fracture mechanics and allowing only for steady-state crack growth, but including the effects of material inertia explicitly, a full-field solution for the deformations is obtained by means of an iteration procedure involving the finite-element method. Numerical results for the strain distribution in the active plastic zone are presented. The fracture criterion for materials which fail in a locally ductile manner proposed by McClintock and Irwin [1],3 which stipulates that crack growth will proceed such that a critical strain level is maintained at a characteristic distance ahead of the crack tip, is adopted. This criterion is coupled with the results of numerical calculations to develop theoretical dynamic fracture toughness versus crack tip speed relationships for two levels of critical strain. For rate-dependent materials a range of toughness-versus-speed relations is manifested, ranging from that similar to rate-independent materials for low rate sensitivity to a relationship which rises dramatically for even a small increase in crack speed at low crack speeds, but which levels off for higher speeds for extremely rate-sensitive materials.
Parametric Analysis of Creep Crack Growth in Austenitic Stainless Steel
Authors: Sadananda K , Shahinian P
Published: March 2009

Creep crack growth behavior in Type 316 stainless steel at 593°C has been examined under displacement control and the results are compared with those under load control. The growth rates were analyzed in terms of linear elastic stress-intensity factor, K, reference stress, σr, and elastic-plastic energy rate parameters, J*, to determine which one of the three is best suited for correlating creep crack growth rates in the stainless steel. The results indicate that the correlations in terms of the three parameters do not depend on the method of testing, that is, displacement of load-controlled tests. Furthermore, the data correlate best with J*-integral, with a spread in the data by a factor of 10 in comparison with a factor of 1000 in terms of the other two parameters. Since the dimensions and the range of values for K and J* are significantly different, to facilitate a more meaningful comparison between elastic and elastic-plastic parameters, a linear elastic energy rate parameter K* is defined which is equivalent to J* in the linear elastic approximation. The analysis indicates that the crack growth data for the two types of tests correlate better in terms of K* than in terms of J* at low K*-values. At high values of K*, plasticity effects become pronounced, thus invalidating its applicability. Thus, in spite of the lack of correlation on a K basis, linear elastic fracture mechanics concepts may still be valid since the data can be correlated on a K* basis. But the present work clearly shows that the J*-integral is better than the stress-intensity factor K for creep crack growth in stainless steel.
Obtaining More Precise Descriptions of Peats by Use of Oriented Microtome Sections
Authors: Cohen AD
Published: March 2009

A procedure is described for making relatively undistorted, oriented microtome sections of peat for microscopic analysis. This simple procedure results in a permanent sample from which data can be produced that are precise, statistically reproducible, and easily transmitted and compared with data from other sources.

Highly accurate fiber-to-matrix ratios, porosities, and mineral contents can be quickly and easily determined from area point-counts of these peat sections. The terms fibric, hemic, and sapric, which have been widely used in the United States for describing peats, can be very precisely applied to peat samples in which fiber contents are determined in this way.

Color and translucency of peatified tissues can be measured from unstained microtome sections; or microtome sections may be differentially stained to bring out chemical or physical difference between tissues at different levels. Optical birefringence and fluorescence are two characteristics of peat tissues which can also be accurately measured. Both can be related to source substances and degree of decomposition.

This microtome sectioning technique has been used to describe and classify peats from the Everglades-Mangrove Region of Florida, the Okefenokee Swamp of Georgia, the Snuggedy Swamp of South Carolina, and the Albemarle-Pamlico Peninsular Swamps of North Carolina. The technique worked equally well on peats ranging in physical characteristics from coarsely-fibrous or woody (fibric) to finely-granular (sapric).
A Multistage Sampling Technique for Peat Deposits Utilizing Soil Survey Maps
Authors: Smith MR , LeMasters GS , Bartelli LJ
Published: March 2009

One purpose of this paper is to report on a multistage sampling scheme used in a Michigan peat resources study. A second purpose is to show how variations of this method can be applied in a sequential manner to adjust for incoming data or changing budgetary parameters.

The sampling plan for this study is a multistage sampling scheme utilizing clustering and multiple stratification. The State of Michigan has been stratified into soil-geomorphic provinces in order to group together organic soils formed on similar associated land surfaces. Within each province the unit of interest is the county or portion of the county. Each county or portion is then sampled. Each township within a county is stratified into four levels of organic soil deposit size, based on dot counts of soil survey maps. The townships form stratified clusters, and within each township a stratified sample of sections is chosen. Within each section systematic transect samples of the organic soils are obtained. The sampling plan should result in good point and interval estimates of organic soil characteristics by section, township, county, province, and total state evaluation.

The advantages and disadvantages of this sampling method are discussed in detail. Its advantages include: simplicity to implement in the field; ability to change with different geographic, personnel, or budgetary restrictions; and ability to be modified in a sequential manner as data are collected. The major disadvantage is the resulting relatively complex estimating equations. An attempt is made to simplify the explanation of these equations.

The utilization of this sampling scheme in conjunction with soil survey maps gives a very efficient method of estimating the total amount and characteristics of peat over a large geographic area.
Effect of Peat Type and Decomposition on the Calorific Value of Some New Brunswick Peats
Authors: D Keys
Published: March 2009

A detailed inventory of the peatlands in the Province of New Brunswick has been used to select representative sites on major peatlands for determination of several physical and chemical characteristics. At the selected sites a core was recovered for the entire thickness of the deposit using either a 4-cm piston sampler or a 10-cm Macaulay sampler. The core was subdivided into sample intervals on the basis of changes in peat type and humification (decomposition). The samples were oven-dried and calorific value was determined. Ash content was also determined to facilitate comparison of results on an ash-free basis.

The values obtained were grouped by degree of humification for comparison. The values were then subdivided into Sphagnum-dominated and Carex-dominated (sedge) peats for further comparison. Sedge peats were found to have higher calorific values than Sphagnum peats at all observed degrees of humification. For both peat-type groups the calorific value increased with increased decomposition, with the rate of increase being greater for Sphagnum peats.
Characterization of Organic Soils as Energy Sources
Authors: LeMasters GS , Bartelli LJ , Smith MR
Published: March 2009

Organic soil materials are characterized by the National Cooperative Soil Survey as fibric, hemic, or sapric, using the rubbed fiber volume and the sodium pyrophosphate extract color (SPEC) as differentiae. The U.S. Department of Energy (DOE) defines fuel-grade peat as having a minimum gross calorific value of 8000 Btu/oven-dry lb (18.6 J/kg), and a maximum ash content of 25% by weight. The object of this study was to determine the nature of the correlations between the unrubbed and rubbed fiber volume, SPEC, calorific value, and percent ash parameters for selected organic soil materials.

Thirty-four samples of the most common kinds of materials collected as part of the Peat Resource Estimation in Michigan research project were selected for characterization. Fiber volumes and pyrophosphate solubility were determined in duplicate after procedures of the National Soil Survey Laboratory of the Soil Conservation Service. Calorific value and ash content were determined in accordance with ASTM Test for Gross Calorific Value of Solid Fuel by the Isothermal-Jacket Bomb Calorimeter (D 3286-77) and ASTM Test for Ash in the Analysis Sample of Coal and Coke (D 3174-73). Correlation analyses were performed between these five data sets.

The correlation between rubbed fiber and calorific value was not significant (α = 0.05). Unrubbed fiber and SPEC were significantly correlated with calorific value (r = 0.363, r = 0.530), while a much stronger correlation existed between the ash content and calorific value (r = −0.869). The results suggest that the ash content of the materials is a very useful indicator of the calorific value, much more so than the other parameters studied.

Other systems of characterizing organic soil materials for fuel used by other peat resource estimation projects are compared with the system used in Michigan. Ash content and calorific value data reported by these projects are compared with the aforementioned findings.
Compressibility and Shear Characteristics of Radforth Peats
Authors: Landva AO , La Rochelle P
Published: March 2009

Radforth peat is a term introduced here to describe peats with a negligible content of mineral matter. The Sphagnum peat discussed in this paper consists mostly of fibrous particles such as stems, leaves, fiber hairs, etc.

Outstanding characteristics of Radforth peats are their extremely high compressibility and high rate of creep. The variability of peat is often almost unpredictable, even within an apparently uniform deposit. Predictions of magnitude and rate of settlement are therefore difficult. Frequent disturbed sampling and classification combined with empirical relationships may give better results than infrequent undisturbed sampling, consolidation testing, and theoretical relationships.

Peat fibers affect the geotechnical behavior of peat by providing an internal lateral resistance to shear deformations in the triaxial mode of shear. Since pore pressures reduce this resistance, loading under drained conditions will provide better stability through higher lateral resistance.

The shear strength of peat in ring shear would be virtually unaffected by fiber reinforcement. The behavior of the Escuminac peat in ring shear was surprisingly consistent and gave parameters of c = 2.4 kPa and φ = 27 to 32 deg within a load range of 3 to 50 kPa. These values would be directly applicable in the case of retaining structures on peat, for which triaxial φ-values of 40 to 50 deg, as consistently reported in the literature, could in fact be misleading.
Geotechnical Properties of Peat in San Joaquin Delta
Authors: Marachi ND , Dayton DJ , Dare CT
Published: March 2009

The San Joaquin Delta region in Central California covers about 780 square kilometres (300 square miles) of reclaimed islands and tracts and over 650 km (400 miles) of waterways and 1300 km (800 miles) of levees. Its peaty soils are some of the riches farm land in the world, but also have very undesirable geotechnical properties. The geotechnical problems facing the islands which are related to the peat are oxidation, seepage and erosion loss, low strength, light weight, and high compressibility. The oxidation, compressibility, and wind erosion of the peat and other soils cause subsidence at a rate of 6 to 8 cm (2.5 to 3 in.) per year, and as a result the islands presently are as much as 6.5 m (20 ft) below sea level. The investigations, which were performed to evaluate the hazards to the water aqueducts passing through this area, included over 50 borings and 100 cone penetration test (CPT) probes. Laboratory testing included classification, strength, and consolidation tests of peat. The geotechnical properties of the peat and their statistical variations are given, and the important parameters of the strength and deformation are analyzed in detail. The results indicate that peat in this area has a mean dry density of 0.32 ton/m3 (20 lb/ft3) and a water content of 320%. The effective angle of internal friction was 28 deg; however, the maximum strength was reached at strains well beyond 15 to 20%. In triaxial undrained tests the developed pore pressure often equalled the cell pressure for sample strains beyond 5 to 10%.
Characterization of Silicon Dioxide Surfaces by Successive Determinations of the Solution Rate
Authors: Baumann H
Published: March 2009

The successive determination of the solution rate in sodium hydroxide or in buffer solutions may serve to establish the extent of surface defects and the thickness of the more or less amorphous layer of silicon dioxide (SiO2) dusts. The solution rate is a sensitive measurement for the energetic and thus crystallographic surface structure. Quartz surface modification due to thermal treatment is shown by examples. Furthermore, it is possible to produce quartz with a “pure” surface. The results of cell and animal experiments performed with crystallographic pure quartz specimens and with the same specimens coated with thin layers of amorphous silica are discussed.
Characterization of the Inflammatory Response in Experimental Silicosis
Authors: Dauber JH , Rossman MD , Daniele RP
Published: March 2009

Six months after intratracheal instillation of silica, histologic, ultrastructural, and cytologic studies were performed to characterize the inflammatory response in the lungs of guinea pigs. Granulomatous and diffuse interstitial infiltration occurred predominantly in the peribronchial regions. Ultrastructural evaluation confirmed the presence of a mixed cellular infiltrate and fibrosis in the alveolar interstitium and Type II lining cell hyperplasia. Recovery of bronchoalveolar cells by whole lung lavage and the proportion of neutrophils and multinucleated giant cells in this population were significantly higher in experimental animals (p < 0.05) than in controls (intratracheal saline). Lung macrophages from experimental animals exhibited impaired adherence and motility in vitro. The mechanisms by which inflammatory cells might be recruited into the lungs of these animals and the importance of altered macrophage function are discussed.
Effects of Unmodified Natural and Coated Silicious Earth in a Long-Term Intraperitoneal Test in Rats
Authors: Weller W
Published: March 2009

In a long-term intraperitoneal test with rats the quantitative and qualitative effect of unmodified natural silicious earth with and without surface coating was studied. The following results were obtained: Natural silicious earth (NSE) causes distinct silicotic reactions. Surface-coating of this dust does not reduce its harmfulness, but only an initial inhibition of the silicotic reaction can be observed. The effects of natural products (silicious earth, diatomaceous earth, diatomite) as well as of amorphous synthetic silica are compared and contrasted.
Possible Health Hazards from Different Types of Amorphous Silicas
Authors: Jahr J
Published: March 2009

A review is given of some of the literature on the effect of different amorphous silicas on the lungs, with emphasis on the type collected in the ferrosilicon industry. Animal experiments indicate that amorphous silica gives a fairly strong initial lung reaction which, however, has little or no tendency to progress, and thus differs significantly from crystalline silica. Most of the reported cases of silicosis among workers exposed to amorphous silica in the ferrosilicon industry have either been transient lung changes or connected to exposure to crystalline silica. Workers exposed only to precipitated amorphous silica do not seem to be at any significant risk. Amorphous silica transforms easily to cristobalite at temperatures much lower than the reported stable temperature range (1470 to 1710°C). It then represents a silicosis hazard if inhaled. Provisional administrative norms (AN) [corresponding to threshold limit values (TLVs)] are suggested.
Summary
Authors: Gross P
Published: March 2009

The papers presented at the Symposium on Health Effects of Synthetic Silica Particulates covered a wide spectrum of subjects. They ranged from in vitro methods that may be useful for screening purposes to more lengthy in vivo experiments and clinical investigations, from the relationship between molecular configuration and biological sequella of some silicas to their effects on cellular organelles and the products of the latter, and from detailed pathological tissue changes to the resultant effects upon lung function.
Corrosion-Fatigue Crack Initiation Behavior of Four Structural Steels
Authors: Novak SR
Published: March 2009

This study was undertaken to investigate the corrosion-fatigue crack initiation (CFCI) behavior of steels with nominal yield strengths from 248 to 1034 MPa (36 to 150 ksi). Notched specimens were exposed to a 3.5% NaCl solution under constant-load-amplitude conditions at a stress ratio R of 0.10 and at a cyclic frequency of 12 cycles per minute (0.2 Hz). Results of crack-initiation life (NI) were characterized in terms of cyclic stress-intensity range normalized relative to notch-tip root radius [(ΔK/√ρ)] and in terms of cyclic-stress range at the notch tip (Δσmax).

Results showed that the CFCI behaviors for the A36, A588-A, A517-F, and V-150 steels investigated were virtually identical. Each steel exhibited a linear relationship of (ΔK/√ρ) versus log NI for cyclic lives from NI ≊ 104 to 3 × 106 cycles, where the latter value reflects a continuous testing period of about 180 days (6 months). All four steels exhibited about the same cyclic-stress range of (ΔK/√ρ) ≊ 207 ± 21 MPa (30 ± 3.0 ksi) at NI = 3 × 106 cycles. No evidence of a CFCI threshold behavior was determined or apparent up to 3 × 106 cycles. Compared with the respective estimated values of fatigue-crack-initiation (FCI) threshold in air [(ΔK/√ρ)th ≊ 448, 552, 758, and 1138 MPa (65, 80, 110, and 165 ksi)], such values of (ΔK/√ρ) for CFCI behavior correspond to degradations of about 54, 62, 72, and 82% for the A36, A588-A, A517-F, and V-150 steels, respectively. The cited values of (ΔK/√ρ) at 3 × 106 cycles were also equivalent to a cyclic-stress range at the notch tip of Δσmax ≊ 234 ± 24 MPa (34 ± 3.4 ksi).

The results show that the CFCI behavior of A36, A588-A, A517-F, and V-150 steels is finite for all current test conditions and is determined by the absolute level of the cyclic-stress range [(ΔK/√ρ) or Δσmax]. Such results are in direct contrast with well-established fatigue behaviors in air, where the FCI threshold level [(ΔK/√ρ)th or (Δσmax)th] varies directly with strength level (σys or σts). Thus, the present results show that, whereas FCI behavior varies directly with strength level, the CFCI behaviors for all four steels studied were virtually identical and occurred independently of strength level.
Anomalous Fatigue Crack Growth Retardation in Steels for Offshore Applications
Authors: Van Der Velden R , Ewalds HL , Schultze WA , Punter A
Published: March 2009

Cracks in structural steel were retarded or even stopped when fatigued in aerated seawater environments at 10 Hz. Backface strain measurements proved that the cause was corrosion product wedging, which enhances the effect of crack closure. The wedge thickness depended on the oxygen supply inside the crack. This is enhanced by acration and solution pumping, which was more effective at higher frequencies.
Crack Growth by Stress-Assisted Dissolution and Threshold Characteristics in Corrosion Fatigue of a Steel
Authors: Endo K , Komai K , Shikida T
Published: March 2009

Corrosion-fatigue crack growth and the threshold characteristics of a high-tension steel HT55 (σB = 580 MPa) have been investigated in 1% NaCl solution by using an automated microcomputer-controlled K-device.

Crack growth rates are significantly reduced in 1% NaCl solution at 5 Hz and R = 0.1, with a threshold value above the air values. The corrosion-products-induced wedge effect results in a reduced ΔK-value, thereby reducing growth rates. Therefore crack growth rates in 1% NaCl solution exceed those in air, with a lower threshold value than in air when considered in terms of ΔKeff.

Supposing a linear summation hypothesis in terms of ΔKeff given by (da/dN)CF = (da/dN)F + (da/dN)D, the crack growth that proceeds by stress-assisted dissolution (da/dN)D is derived. A proposal to estimate long-term corrosion-fatigue crack growth characteristics is presented, where ΔKeff is assumed to be identical to ΔK since the crack tip is blunted and the crack is much thickened in long-term corrosion fatigue. The long-term corrosion-fatigue crack growth curves are finally derived at various stress cycle frequencies.
Effects of Microstructure and Frequency on Corrosion-Fatigue Crack Growth in Ti-8Al-1Mo-1V and Ti-6Al-4V
Authors: Yoder GR , Cooley LA , Crooker TW
Published: March 2009

Fatigue crack growth studies were conducted on Ti-8Al-1Mo-1V and Ti-6Al-4V alloys in 3.5% NaCl aqueous solution. Each alloy was studied in two microstructural conditions and at two cyclic frequencies. Ti-8Al-1Mo-1V was heat-treated to produce a fine-grained duplex anneal microstructure and a coarse-grained Widmanstätten microstructure resulting from a beta anneal. The two microstructural conditions for the Ti-6Al-4V were an as-received mill anneal and a beta anneal. The two cyclic frequencies were 0.1 and 5.0 Hz. Each of the four alloy/microstructure combinations studied has been the subject of prior investigation regarding fatigue crack growth rate/microstructure interactions in ambient air environments. For both alloys, crack growth rates in air were found to be significantly reduced as a result of microstructural modifications associated with the beta anneal heat treatment. Although the salt water environment significantly accelerated crack growth rates for both alloys, this same ranking of fatigue crack growth resistance persisted in the present study. Both microstructures of the Ti-6Al-4V alloy exhibited a frequency crossover effect; in contrast, no significant frequency effects were observed in Ti-8Al-1Mo-1V in either microstructure. Similar frequency effects were seen in separate specimens cycled at a single constant frequency or in single specimens cycled at two alternating frequencies. Out-of-plane cracking was observed in both alloys in the beta-annealed condition. The effects of varying degrees of out-of-plane cracking on apparent crack growth rates are noted.
Corrosion-Fatigue Crack Initiation in an Iron-Caustic System
Authors: Leis BN , Rungta R , Mayfield ME , Beavers JA
Published: March 2009

Trends in stress corrosion and fatigue behavior are reviewed and a postulate for a general physical model of the corrosion fatigue process is advanced. Essential features of the postulate are surface reactions and degradation, pit formation, and stress corrosion cracking (SCC), with provision for an incubation period for pitting to become effective and for SCC to develop. Data related to surface degradation, fractography, and material fatigue resistance are presented for an iron-caustic system and discussed with respect to the postulate. The results suggest that surface degradation and SCC are the essential aspects of the corrosion-fatigue process for the iron-caustic system.
Electrochemical Corrosion Testing
Authors: Mansfeld F , Bertocci U
Published: March 2009

Description

Describes the most recent, useful procedures for determining the mechanisms of various corrosion phenomena, evaluating the corrosion susceptibility of various materials, and measuring rates of corrosion.
Building Security
Authors: Stroik J
Published: March 2009

Description

Experts delineate overall planning policies for our cities; methodologies for studying the effects of burglary and vandalism; the impacts of codes and standards; the needs of particular buildings; the needs for more basic research; state-of-the-art for particular security related building components.
Fractography and Materials Science
Authors: Gilbertson LN , Zipp RD
Published: March 2009

Description

This well-illustrated text demonstrates the importance of using the latest fractographic principles in material science. The principles are applied to a variety of metals including iron, aluminum, titanium, copper, nickel, tungsten base alloys; and various nonmetals including polymers, ceramics, and glass.
Water for Subsurface Injection
Authors: Johnson JL , Stanford JR , Wright CC , Ostroff AG
Published: March 2009

Description

Covers four areas that must be considered in order to develop and maintain a sound, trouble-free water injection system:

FiltrationCorrosion QualityReservoir ConsiderationsTreatment Methods
Fracture Mechanics for Ceramics, Rocks, and Concrete
Authors: Freiman SW , Fuller ER
Published: March 2009

Description

This volume emphasized the use of current fracture mechanics models to understand the failure of important engineering materials such as concrete, SiC, Si3N4 and Si-Al-O-N's.
Permeability and Groundwater Contaminant Transport
Authors: Zimmie TF , Riggs CO
Published: March 2009

Description

Problems faced by geotechnical engineers and geologists who are currently involved in ground water seepage analysis and evaluation of contaminant transport problems are covered in the publication. Permeability-hydraulic conductivity-is only one of the many parameters required to predict groundwater contaminant transport.
Acoustic Emissions in Geotechnical Engineering Practice
Authors: Drnevich VP , Gray RE
Published: March 2009

Description

The Symposium on Acoustic Emissions in Geotechnical Engineering Practice was held 24 June 1981, during the June Committee Week of the American Society for Testing and Materials in Detroit, Michigan. ASTM Committee D18 on Soil and Rock for Engineering Purposes sponsored the symposium. V. P. Drnevich, University of Kentucky, and R. E. Gray, GAI Consultants, Inc., organized the symposium and served as editors of this publication.
Through-Thickness Tension Testing of Steel
Authors: Glodowski RJ
Published: March 2009

Description

STP 794 endeavors to provide insights into through-thickness tension testing. The papers comprising this book's contents are divided into two sections, which are focused on the design and preparation of test specimens, and the relations between the through-thickness tension test results and metallurgical factors.
Titanium Alloys in Surgical Implants
Authors: Luckey HA , Kubli F
Published: March 2009

Description

The symposium on Titanium Alloys in Surgical Implants was held in Phoenix, Ariz., on 11-12 May 1981. Sponsoring the event were ASTM Committee F04 on Medical and Surgical Materials and Devices and ASTM Committee B10 on Reactive and Refractory Metals and Alloys. The symposium chairmen were Hugh A. Luckey, 3M Orthopedic Products, and Fred Kubli, Jr., RMI Company, both of whom also served as editors of this publication.
Composite Materials: Quality Assurance and Processing
Authors: Browning CE
Published: March 2009

Description

This volume provides the reader with an understanding of relevant methodologies, rationales, and experimental results, as well as a general understanding of current and future trends of research activities in this highly important area.
Aquatic Toxicology and Hazard Assessment: Sixth Symposium
Authors: Bishop WE , Cardwell RD , Heidolph BB
Published: March 2009

Description

The contents of STP 802 include papers on aquatic toxicology, environmental chemistry, environmental modeling, and aquatic hazard assessment. 35 papers serve in the attempt to bridge the gap between laboratory and field results and to model of study the behavior of chemicals of organisms in complex environments.
Elastic-Plastic Fracture: Second Symposium, Volume II Fracture Resistance Curves and Engineering Applications
Authors: Shih CF , Gudas JP
Published: March 2009

Description

Two separate volumes comprise STP803. The papers in these two volumes have been grouped into six topic areas including elastic-plastic crack analysis, fully plastic crack and surface flaw analysis and correlation, engineering applications, test methods and geometry effects, and cyclic plasticity effects and material characterization.
Hazardous and Industrial Solid Waste Testing: Second Symposium
Authors: Conway RA , Gulledge WP
Published: March 2009

Description

Second in a series, the purpose of this book is to describe new and improved means of evaluating hazardous and industrial solid wastes in terms of both hazard degree and disposal options.
Pesticide Formulations and Application Systems: Third Symposium
Authors: Kaneko TM , Akesson NB
Published: March 2009

Description

15 papers address: the use of entomopathogens to control insects; the effects of formulation and aerial application techniques on microbial insecticides; laboratory sprayers used to evaluate the compatibility of tank mixes; effective control of aquatic pests; and selection of appropriate carriers for water-dispersible granules.
Drop-Weight Test for Determination of Nil-Ductility Transition Temperature: User's Experience with ASTM Method E 208
Authors: Holt JM , Puzak PP
Published: March 2009

Description

STP 919 addresses the user’s experience with the drop weight test, ASTM standard E 208, which determines the nil ductility transition temperature of ferritic steels. The four broad topics of this book are: unusual material behavior; advantages of the test including correlations with service, other tests, or both; Shortcomings of the method; and unique testing equipment and experimental techniques.
The prevalence and characteristic features of cyclicity and variability in Cushing's disease
Authors: Alexandraki Krystallenia I , Kaltsas Gregory A , Isidori Andrea M , Akker Scott A , Drake William M , Chew Shern L , Monson John P , Besser G Michael , Grossman Ashley B
Published: March 2009

Objective

Cyclical Cushing's syndrome may render the diagnosis and management of Cushing's disease difficult. The aim of the present study was to investigate the prevalence of cyclicity and variability in patients with Cushing's disease, and to identify putative distinctive features.

Design

Retrospective case-note study.

Methods

We analysed the case records of 201 patients with Cushing's disease in a retrospective case-note study. Cyclicity was considered as the presence of at least one cycle, defined as a clinical and/or biochemical hypercortisolaemic peak followed by clinical and biochemical remission, followed by a new clinical and/or biochemical hypercortisolaemic peak. The fluctuations of mean serum cortisol levels, as assessed by a 5-point cortisol day curve, defined the variability.

Results

Thirty (14.9%; 26 females) patients had evidence of cyclicity/variability. ‘Cycling’ patients were older but no difference in sex or paediatric distribution was revealed between ‘cycling’ and ‘non-cycling’ patients. The median number of cycles was two for each patient, and 4 years was the median intercyclic period. A trend to lower cure rate post-neurosurgery and lower adenoma identification was observed in ‘cycling’ compared with ‘non-cycling’ patients. In multivariate analysis, older patients, longer follow-up, female sex and no histological identification of the adenoma were associated with an increased risk of cyclic disease.

Conclusions

This large population study reveals that cyclicity/variability is not an infrequent phenomenon in patients with Cushing's disease, with a minimum prevalence of 15%. Physicians should be alert since it can lead to frequent problems in diagnosis and management, and no specific features can be used as markers.
Merits and pitfalls of mifepristone in Cushing's syndrome
Authors: Castinetti F , Fassnacht M , Johanssen S , Terzolo M , Bouchard P , Chanson P , Do Cao C , Morange I , Picó A , Ouzounian S , Young J , Hahner S , Brue T , Allolio B , Conte-Devolx B
Published: March 2009

Objective

Mifepristone is the only available glucocorticoid receptor antagonist. Only few adult patients with hypercortisolism were treated to date by this drug. Our objective was to determine effectiveness and tolerability of mifepristone in Cushing's syndrome (CS).

Design

Retrospective study of patients treated in seven European centers.

Methods

Twenty patients with malignant (n=15, 12 with adrenocortical carcinoma, three with ectopic ACTH secretion) or benign (n=5, four with Cushing's disease, one with bilateral adrenal hyperplasia) CS were treated with mifepristone. Mifepristone was initiated with a median starting dose of 400 mg/day (200–1000). Median treatment duration was 2 months (0.25–21) for malignant CS, and 6 months (0.5–24) for benign CS. Clinical (signs of hypercortisolism, blood pressure, signs of adrenal insufficiency), and biochemical parameters (serum potassium and glucose) were evaluated.

Results

Treatment was stopped in one patient after 1 week due to severe uncontrolled hypokalemia. Improvement of clinical signs was observed in 11/15 patients with malignant CS (73%), and 4/5 patients with benign CS (80%). Psychiatric symptoms improved in 4/5 patients within the first week. Blood glucose levels improved in 4/7 patients. Signs of adrenal insufficiency were observed in 3/20 patients. Moderate to severe hypokalemia was observed in 11/20 patients and increased blood pressure levels in 3/20 patients.

Conclusion

Mifepristone is a rapidly effective treatment of hypercortisolism, but requires close monitoring of potentially severe hypokalemia, hypertension, and clinical signs of adrenal insufficiency. Mifepristone provides a valuable treatment option in patients with severe CS when surgery is unsuccessful or impossible.