bluuebunny/crossref_metadata_2025 huggingface dataset:
Safety Margins: Classical Mammalian Approaches and Practical Aspects of Their Present Use in Aquatic Toxicology
Authors: Gibson JR
Published: March 2009

The approach of mammalian toxicologists to determining margins of safety has been to define situational margins of safety for each definable situation; however, aquatic toxicologists have taken a global approach to estimating safety margins, attempting to establish a single margin of safety to encompass all conceivable situations. Though either approach can determine safety margins that will protect organisms or systems of concern, the global approach is likely to be more conservative, and thus much more difficult to achieve. In the future, aquatic toxicologists should try to move toward situationally dependent assessments.
Modeling the Fate and Transport of Chemicals in Estuaries: Current Approaches and Future Needs
Authors: Bostater CR , Ambrose RB , Bell B
Published: March 2009

A discussion of chemical modeling approaches is presented with emphasis on modeling chemicals in estuaries. An application of modeling di-n-octyl phthalate in a subestuary of Chesapeake Bay indicates that the most sensitive processes for an analyst to consider in estuary chemical modeling are dispersive transport, biological partitioning, boundary exchange, and sediment partitioning. Additional research is needed to evaluate the role of coagulation and sedimentation in such efforts. A framework for consideration of effects modeling is presented briefly.
Phosphate Ester Hydraulic Fluids: An Aquatic Environmental Assessment of Pydrauls 50E and 115E
Authors: Mayer FL , Adams WJ , Finley MT , Michael PR , Mehrle PM , Saeger VW
Published: March 2009

Two phosphate ester hydraulic fluids, Pydrauls 50E and 115E, are used principally in industrial systems. A study by the U.S. Environmental Protection Agency indicated that a significant portion of the annual production of all hydraulic fluid was discharged into the environment as a result of leakage. We studied the mobility, persistence, bioconcentration potential, acute and chronic toxicity, and environmental concentrations of Pydrauls 50E and 115E and their three main components: triphenyl phosphate, nonylphenyl diphenyl phosphate, and cumylphenyl diphenyl phosphate. Physicochemical properties and use-disposal patterns were also considered.

Pydrauls 50E and 115E presently do not appear to constitute an unreasonable risk to the environment; however, inadvertent leakage of these materials to the aquatic environment should be avoided. Toxicity tests indicated that the margin of safety between environmental concentrations in water and the expected biological effect concentration is at least 1 order of magnitude for coldwater fish, and about 3 orders of magnitude for warm-water species. Better control of hydraulic fluid leakage would reduce environmental contamination and increase the margin of safety.
Principles of Aquatic Hazard Evaluation as Applied to Ocean-Disposed Wastes
Authors: Rose CD , Ward TJ
Published: March 2009

The effects-based criteria identified in the 1977 ocean dumping regulations and associated guidelines for evaluating potential hazard of ocean-disposed wastes to aquatic organisms are reviewed. The use of these criteria, which provide for bioassay-based limiting permissible concentrations for physical phases of wastes to be compared with estimated environmental concentrations of the phases, is demonstrated in case studies of two wastes (acid-iron wastewater and dredged material) that are dumped in the ocean and one waste (formation water) that is discharged from an ocean outfall. The case studies present Lagrangian (exposure-time-dependent) assessments of the potential hazard of ocean-disposed wastes to plankton, as well as Eulerian (exposure-time-independent) evaluations of the potential hazard to nonplanktonic organisms. A plume study and models of different levels of sophistication are employed to estimate environmental concentrations of ocean-disposed materials.
Applications and Results of Analytical Methods Used in Monitoring Environmental Contaminants
Authors: Ribick MA , Smith LM , Dubay GR , Stalling DL
Published: March 2009

Techniques being developed to purify, fractionate, and classify complex organic chemical residues will simplify the detection of these residues and provide more comprehensive data about them. These techniques include an integrated series of chromatographic processes, new technology in mass spectrometry, advances in glass capillarygas chromatography, and chemical derivatization.

Gel permeation chromatography increases the efficiency of sample cleanup. Additional cleanup and selective separation of residues are achieved by adsorption chromatography (Florisil, silica gel, and carbon foam). An important finding which results from the use of this methodology is the identification of potentially toxic chlorinated dibenzofurans in fish tissue. An analytical scheme for isolating and detecting acidic pollutants was developed: derivatization of phenols and other acidics to pentafluoro benzyl ethers enhances their chromatography and detection. Partial automation of the sample cleanup and enrichment of residues reduces the time required for analyses, and the new separation techniques increase the number of components that are identifiable from a tissue matrix.
Reliability of the Bacterial Luminescence Assay for Determination of the Toxicity of Pure Compounds and Complex Effluents
Authors: Bulich AA , Greene MW , Isenberg DL
Published: March 2009

The bacterial luminescence toxicity assay has been under development for 2 years. The assay procedure has been significantly improved in that five dilutions of a toxicant or effluent can be assayed simultaneously along with a control. A median effective concentration (EC50) can be generated 30 min after sample collection. The reproducibility of the assay using sodium lauryl sulfate as a standard displayed a coefficient of variation of 15 to 20 percent. The data presented compare Microtox EC50 data for pure compounds and literature data on median lethal concentrations (LC50) for fish. In addition, over 50 complex effluent samples were assayed with Microtox. These same samples were assayed simultaneously using standard fish testing procedures. The data show that a good correlation exists between the bacterial luminescence assay and conventional testing procedures.
Statistical Inconsistencies in the Use of No-Observed-Effect Levels in Toxicity Testing
Authors: Skalski JR
Published: March 2009

Use of the no-observed-effect level (NOEL) as an experimental end point violates the principle of negative inference, the logical basis of statistical hypothesis testing. The NOEL is based on the nonrejection of the hypothesis of no toxic effect, whereas scientific methods stress conclusions based on the rejection of a hypothesis. Failure to reject this hypothesis may result either because the concentration is “safe” or because the experimental protocol to detect a toxic response is insensitive, but the cause is indeterminant and the error rate unknown. The lowest rejected concentration tested (LRCT) is recommended as an experimental end point. By the use of LRCT the rate of misclassification is known and is equal to α. Experimental designs that emphasize both the biological and the statistical significance of LRCT end points are recommended.
Test Method for Evaluating the Effects of Chemicals on Starling Reproduction
Authors: Schafer EW , Brunton RB , Schafer EC
Published: March 2009

A test method is proposed whereby effects of chemicals on reproduction of starlings (Sturnus vulgaris) are monitored in outdoor pen facilities throughout a breeding season. The method involves the use of replications of ten pairs of breeding starlings held in 3 by 3 by 7-m enclosures constructed of plywood and 1.27-cm (0.5-in.) mesh chicken wire. Each enclosure is equipped with ten modified nest box traps that allow observations of nest building, egg laying, incubation, and nestling production. Although initial studies were limited to determining egg fertility after 5 to 7 days of natural incubation, production of starling nestlings or fledglings also should be easy to monitor with only minor modifications in the test method.
Methods for Assessing the Efficiency of Aerial Spraying Control Operations on Quelea Colonies and Roosts
Authors: Elliott CCH
Published: March 2009

The standard methods presently used by the Food and Agriculture Organization of the United Nations (FAO) Quelea Project for estimating mortality in quelea breeding colonies and roosts after spraying are described. Factors are discussed which influence the accuracy of the estimates, such as the period in the breeding cycle, the tendency for the birds to die quicker with one avicide than another, the type of vegetation used for roosting and nesting, and the difficulty of making accurate assessments of the roost numbers. Whatever the estimate produced, it is postulated that the number or percentage of birds killed has only limited significance. What really matters is whether quelea damage to nearby cereal crops has been curtailed effectively. Ultimate success, therefore, can be evaluated only by crop damage assessments both before aerial spraying and again at the time of harvesting. Methods used in crop damage assessment are considered and examples provided of their use in evaluation of quelea control.
Recommended Practice for Determining the Effectiveness and Safety of Aquatic Animal Control Agents in Static Water Studies
Authors: McCann J , Walker CR
Published: March 2009

This recommended practice describes procedures for testing the effectiveness of aquatic animal control agents and for determining the effect of these agents on nontarget organisms under actual-use conditions. The field tests are recommended after basic relative toxicity data have been established by laboratory tests. Federal and state regulations pertaining to field testing of pesticides must be followed. Data obtained using this practice should generally be applicable to some requirements for registration of an aquatic control agent.
Reducing Potential Hazards of Pesticides to Fish, Wildlife, and Habitat
Authors: Walker CR
Published: March 2009

Environmental safety data must be applied in the registration of pesticides, including labels and labeling. Knowledge of physiology, ecology, and behavior of organisms should be combined with the physical and chemical properties, formulation, and use patterns of pesticides to reduce hazard to fish, wildlife, and habitat. The hazards of pesticides can be separated into (1) the pesticide concentrations, (2) the time and nature of exposure, and (3) exposure to nontarget organisms. Hazard varies with the habitat and the sensitivity of organisms, including the most vulnerable life stage, links of food chains, habitat requirement, and other limiting factors. The bioaccumulation of residues may also compromise the wholesomeness and value of fish and wildlife for both recreational and nutritional uses. Mitigation of the hazard can be accomplished by adequate training of pest control operators, better formulations, application methods, timing of the application, and utilization of the safest pesticides or alternative pest control methods and cultural practices (integrated pest management). However, such precautions must be more universally accepted and applied over broad geographic areas to be effective in minimizing losses.
Chapter 4—Metabolic Function Data: Clinical Chemistry Standards
Authors: Bowers GN
Published: March 2009

The use of objective scientific measurements in medicine has grown rapidly over the last few decades. All present information suggests that quantitative measurements, particularly clinical chemistry testing on blood, urine, and tissues by any number of instrumented electrochemical, enzymatic, and immunochemical techniques, will continue to rise in total volume and in the variety of discrete analytes determined.
Chapter 6—Testing Tools: Development of Measurement Standards for Edge Characterization of Intraocular Lenses
Authors: Teague EC , Scire FE , Vahey DW , Mueller EP
Published: March 2009

Intraocular lenses are small, plastic replacement lenses implanted in the eyes of human patients who have had their natural lenses removed, usually as a result of cataract surgery. About 400 000 people undergo cataract surgery each year, and of that number, 100 000 have intraocular lens implants. Although the operation is generally successful, the edges of some lens' designs, if not properly finished, irritate or damage the eye badly enough to require additional treatment.
Chapter 9—Computerized Medical Technology: Meeting the Challenge and Issue of Standards
Authors: Eden H , Macks GC
Published: March 2009

No computer can deterministically produce valid results from invalid data. Any attempt to use computers to enhance decisions in medicine is thus limited by “problems of consensus and authority of the underlying information”. The problems of uncertainty and error exist in the data bases of all medical specialties.
Chapter 14—Development of Compatibility for Clinical Effectiveness: Monitoring Devices
Authors: Kirchhoff WH , Doyle FJ
Published: March 2009

Standards for monitoring devices and telemetry in the health care field have traditionally focused primarily on performance effectiveness of a device or on safety considerations for the patient and attendant medical person. As a result, adequate performance and safety standards for commonly used devices exist and are usually developed initially vt^hen a new product or technology is introduced to the marketplace. That is not to say that all the necessary standards have been written or are under development. In particular, standards associated with maintenance, durability, and long-term reliability are needed. Nevertheless, the area that requires the greatest attention is systems compatibility.
Chapter 18—Evaluating Medical Devices for the Clinical Environment
Authors: Jones RJ
Published: March 2009

Physicians are constantly encountering problems in their practice that appear to defy solution. Like everyone in our society, they have come to expect better solutions through science or through technological advance. All too often, however, the gains obtained are less than promised, and sometimes horrendous new problems are created-expectations must be modified and dreamers brought back to earth.
Chapter 19—Disposable Devices in Clinical Therapy: Foley Catheters—A Model for the Development of a Standard
Authors: Boyarsky S
Published: March 2009

Performance standards are the fine adjustment to commercial and professional life in a highly industrialized society. The lack of organizations like ASTM would greatly complicate the tasks of consumers in specifying needs and producers in meeting them. Their absence would also complicate the life of professionals in many ways.
Dependence of Silicon Float-Zone Refining Parameters on Frequency
Authors: Gupta KP , Gregory RO
Published: March 2009

Float-zone refined silicon is produced by establishing a molten zone in a silicon rod, vertically situated and passing the zone through the rod. Induction heating is the typical conventional means for producing the molten zone. Since power levels are very high with large-diameter rods, the efficiency of the heating process is a concern. One of the key parameters is the frequency of the radio frequency current in the induction coil. Silicon rods of 65-mm diameter were zone-refined, at a series of frequencies in the 200 kHz to 3.5 MHz range. It was found that frequencies lower than 500 kHz are not suitable because they produce undesirable surface melting characteristics. On the other hand, higher frequencies tend to increase the susceptibility for arcing. Indeed, the suitable range appears to be between 2 and 3 MHz. The presentation also highlights the major differences between the float-zone and Czochralski processes, and explains the reasons why large-diameter float-zone technology has lagged behind Czochralski technology.
A Review of Optical Lithographic Techniques for VLSI
Authors: Doane DA
Published: March 2009

Optical lithography using UV radiation (200 to 450 nm) has long been the workhorse in pattern generation for fabricating integrated circuit devices on silicon. Various techniques employing projection and proximity printing using electron-beam-generated photomasks have been developed to reduce feature sizes, to improve device yields, and to lower device fabrication costs. In this review, some optical lithographic techniques available for fabricating semiconductor devices are described. The advantages and limitations of the various methods are discussed with an emphasis on their suitability for the geometries required for VLSI.
Resist Profile Quality and Linewidth Control
Authors: Neureuther AR
Published: March 2009

Key parameters and process tradeoffs in improving resist profile quality and linewidth control are explored for optical projection printing. Simulation with program SAMPLE is used to study the impact of image quality, wafer topography, and resist characteristics in the context of the complete lithographic process. The advantages of the use of a bias and of a “surface induction” resist are illustrated. The tradeoff between quality and throughput is explored as a function of the partial coherence factor. Practical rules of thumb are given for performance with single-layer thick resists. The potential improvements with multilayer and inorganic resists are also discussed.
Silicon Crystals for VLSI Technologies
Authors: Jastrzebski L
Published: March 2009

The need for a new generation of electronic circuits with a high degree of integration and a large area of silicon imposes a new demand on the quality of silicon used for their fabrication. This paper reviews the generation process of crystallographic defects (in the context of material characteristics), their effect on device/circuit performance, and their relationship to crystal growth conditions.

The defect formation during processing, effectiveness of internal gettering, and mechanical strength of silicon (resistance to warpage) are mainly controlled by characteristics of oxygen in silicon. For a given process, oxygen precipitation kinetics depends on the crystal growth conditions, which control oxygen incorporation into silicon, formation of active sides for oxygen nucleation, and initial stage of oxygen precipitation. It is believed that proper understanding of required silicon characteristics and proper control of the crystal growth process will lead to higher yield of integrated circuits.
Verification of Tearing Modulus Methodology for Application to Reactor Pressure Vessels with Low Upper-Shelf Fracture Toughness
Authors: Tang SS , Riccardella PC , Huet R
Published: March 2009

A significant number of operating reactor pressure vessels in the United States are anticipated to undergo, during their design lifetime, reductions in upper-shelf fracture toughness below the minimum values currently prescribed in the Code of Federal Regulations. This reduction occurs in the beltline region of the vessels adjacent to the reactor core due to neutron irradiation effects. A methodology has been developed by Paris to apply tearing modulus methodology to quantitatively establish the minimum upper-shelf toughness levels required to maintain an acceptable margin of safety in such vessels.

The proposed analytical techniques and data base are compared with test data and alternative analytical results in order to verify the validity of the methodology. The method is used to predict failure conditions in a series of large pressure vessels and tension bar experiments containing large crack-like defects. The analytical method is also compared with a three-dimensional nonlinear finite-element analysis of a typical pressurized water reactor vessel containing a beltline defect. The method is shown to accurately predict the test failure conditions and to agree well with the finite-element analysis results.
Ductile Tearing Instability Analysis: A Comparison of Available Techniques
Authors: Chell GG , Milne I
Published: March 2009

A comparison is made between the major proposals recently developed for assessing the stability of a structure which is cracking by ductile mechanisms. These proposals all have in common the concept that stability is ensured if the crack driving force is less than the material's resistance to cracking. They differ, however, in how they define and evaluate the necessary parameters.

The four basic procedures discussed are: 1. Direct graphical comparisons, using the J-integral as a fracture parameter. Different methods of estimating the applied J are discussed, together with techniques for comparing the slopes of the applied J and the material's resistance curve. 2. An energy-based method which compares the elastic energy release rate and the plastic work dissipation rate during crack extension. 3. Assessment diagram approaches. These include the Central Electricity Generating Board procedure and methods that incorporate strain-hardening effects. 4. Maximum load crack-opening displacement.

The information needed to perform each analysis and its relevance to the practical problem when viewed against the uncertainties inherent in any structural analysis are discussed. Emphasis is given to the treatment of thermal and residual stresses. It is concluded that the confidence obtained in the results varies from procedure to procedure, but this can be greatly enhanced if certain safeguards are applied during the analysis. The safeguards necessary depend upon which approach is adopted.
Fracture of Circumferentially Cracked Type 304 Stainless Steel Pipes Under Dynamic Loading
Authors: Wilkowski GM , Ahmad J , Zahoor A , Marschall CW , Broek D , Abou-Sayed IS , Kanninen MF
Published: March 2009

A program of experimentation and analysis aimed at determining fracture instability in circumferentially cracked Type 304 stainless steel pipes in seismic or water-hammer loadings is described. Experimental work on center-cracked tension panels revealed that dynamic loading does not affect the net-section stress criterion evolved previously for Type 304 stainless steel. Full-scale tests on 100-mm-diameter (4 in.) pipes subjected to a dynamic load nevertheless indicate that a margin of safety exists beyond that predicted by the application of the net-section stress criterion. It is concluded that the finite duration of a dynamic loading together with the system compliance which allows stable crack growth beyond maximum load is primarily responsible. A J-based plastic fracture mechanics assessment based upon rate-dependent mechanical and fracture properties of the material was made and found to be consistent with this hypothesis.
Quantitative Fractographic Definition and Detection of Fracture Initiation in COD/KIc Test Specimens
Authors: El-Soudani SM , Knott JF
Published: March 2009

One important requirement of any fracture toughness test is the ability to detect the initiation of fracture, and it is here that detailed observations of void growth ahead of the crack tip should provide background calibration for macroscopic measurements such as compliance changes, electrical resistance changes across the notch faces, or acoustic emission output. The nature of incipient crack growth process, however, is such that the use of the term “fracture initiation” requires careful definition. The problem arises in view of the complexity of a set of microscopic-scale events occurring at a crack tip upon extension. In this paper the development of a reliable single-test method for the detection of fracture initiation is described. This method is based on the use of a double-clip-gage system attached to either a fracture toughness (KIc) or a crack opening displacement (COD) test specimen. It locates the initiation point from compliance-related changes in the double-clip-gage output signals and is successful in detecting fracture initiation, independent of specimen size, under conditions of quasi-linear elastic fracture mechanics (QLEFM), elastoplastic fractures (limbo region), and fully yielded specimens (YFM). The double-clip-gage method was calibrated by quantitative scanning electron microscopy of void growth and coalescence during a series of experiments in which ductile low-alloy steel precracked specimens were unloaded from different points on the load-displacement diagram. A three-parameter microfractographic definition of fracture initiation was established at the detectable point based on: (1) maximum lineal extent of advancing microthumbnail cracks; (2) normalized areal growth increment; and (3) the percentage of advanced crack-tip length. Following its rigorous fractographic calibration, the double-clip-gage system was used as a means of checking out other methods of fracture initiation prediction. Four methods were applied simultaneously to the same specimen: the double- (or triple) clip-gage system; an acoustic emission analyzer; a potential drop system; and the Standard Offset Procedure. There was excellent agreement between the double-clip-gage system and both acoustic emission ringdown and event count indications under valid and nonvalid fracture toughness (KIc) test conditions. By comparison, the potential-drop system exhibited appreciable and, in some materials, considerable lagging, the extent of which increased with increasing plasticity. The Standard Offset Procedure agreed well with the calibrated method only in valid KIc tests, but tended to underestimate the initiation point in substandard specimens. When used as a monitoring technique for determining various measures of fracture initiation toughness in situations involving either limited or excess plasticity, the fractographically calibrated double-clip-gage method can serve as a means of developing a unified and consistent ranking of the toughness behavior of materials under widely different conditions.
Elastic-Plastic Fracture Mechanics Analysis of Fatigue Crack Growth
Authors: El Haddad MH , Mukherjee B
Published: March 2009

Fatigue crack growth rate data are obtained for ASTM A516 Grade 70 steel subjected to elastic and elastic-plastic cyclic loading for both load-controlled and displacement-controlled test conditions. Cyclic J-integral values estimated from load versus deflection hysteresis loops and crack closure estimates are correlated with growth rate data. The cyclic J-crack growth rate data agree well with that from the linear elastic tests. The J-integral parameter is shown to be better than the linear elastic parameter K in correlating fatigue crack growth, particularly so in ductile materials such as A516 steel and at high load levels.
Initiation of Fatigue Cracks Around Inclusions in Rolling Fatigue
Authors: Freitas M , Francois D
Published: March 2009

The cyclic behavior of E52 100 quenched and tempered rolling bearing steel displayed strain-hardening according to the law Δσ/2 = 5790 (Δϵp/2)0.137. The fatigue life was found to be given by the formula Δϵ/2 = 0.0073 (2Nf)-0.36 + 0.0145 (2Nf)-0.062.

The cyclic strain-hardening law was used in a finite-element bidimensional incremental elastoplastic analysis to compute the plastic deformation around inclusions in the Herzian stress field produced by a rolling ball. Three types of inclusions were studied: alumina, titanium nitride, and spinel. The maximum plastic strain region was found to be inclined with respect to the rolling direction as observed in rolling bearings. This strain distribution provided an explanation for the relative harmfulness of the various inclusions. The strain amplitude found could be used to predict the number of cycles for fatigue crack initiation at inclusions using the experimental fatigue life law.
Further Developments of a J-Based Design Curve and Its Relationship to Other Procedures
Authors: Turner CE
Published: March 2009

The existing so-called J-design curve is based on shallow-notch data (a/W ⩽ 0.1) and in many other ways is in a less-developed form than the corresponding crackopening displacement and R-6 procedures. A specific though simplified relationship between the three methods of assessment is pointed out and a modified J-estimation method is then proposed. The features of load or displacement control, shallow or deep notches, stress concentrations, and residual stresses are discussed and proposals made to encompass them within the revised procedure. The normalized J, JE/Y2σY2a is expressed as a function of an effective structural strain that depends upon notch depth. One equation is used to describe the load-controlled region of linear elastic fracture mechanics and contained yield, and another, the strain-controlled regime at or above ligament limit load.
Stress-Intensity Factors of Stiffened Panels with Partially Cracked Stiffeners
Authors: Shah RC , Lin FT
Published: March 2009

Theory and numerical procedure are presented to determine the stress-intensity factors for a partially cracked typical stiffener and a partially cracked splice stiffener in a stiffened panel subjected to a uniaxial uniform remote stress normal to the crack. The translational spring element and the beam element with special boundary conditions are investigated for the simulation of flexible fasteners. The finite-element procedure was applied to the problem. From the finite-element solution, the stress-intensity factors were determined by using the displacement method and the strain energy release rate method. Results are presented as stress-intensity configuration factors, Y, for various values of crack lengths, stiffening ratios, stiffener spacings, and fastener flexibilities. The crack growth lives computed from finite-element solutions are compared with test data of panels containing a partially cracked typical stiffener subjected to constant amplitude cyclic loading and spectrum loading. The correlation between the test data and the analyses is very good.
Analysis of Cracks at an Attachment Lug Having an Interference-Fit Bushing
Authors: Hsu TM , Kathiresan K
Published: March 2009

An analytical procedure was presented for computing the stress-intensity factors for a crack emanating from an attachment lug having an interference-fit bushing. The procedure consists of two major steps. First, the effective unflawed stress distribution on the prospective crack surface was obtained by superimposing the residual hoop stresses due to the installation of an interference-fit bushing on the tangential stresses obtained due to the application of pin loading. Next, a crack was introduced in this stress field by removing the tractions on the crack faces and computing the corresponding effective stress-intensity factor using the developed Green's function. It was found that the installation of an interference-fit bushing caused an increase in the effective stress-intensity factor ratio (Reff = Kmin/Kmax), and a significant decrease in the effective stress intensity factor range (ΔKeff = Kmax − Kmin). This would result in reduction of the fatigue crack growth rate. The effects of the rigidity and the thickness of the bushing on the stresses and the effective stress-intensity factors also were presented.
Approximate Influence Functions for Part-Circumferential Interior Surface Cracks in Pipes
Authors: Lim EY , Dedhia DD , Harris DO
Published: March 2009

Approximate influence functions are presented for a part-circumferential semielliptical interior surface crack in a circular pipe. The influence functions are derived from the crack surface opening displacements obtained by the use of boundary integral equation techniques. Such functions are useful in evaluating stress-intensity factors for cracks in bodies subjected to complex stress conditions, and convenient curve fits suitable for numerical calculations are provided. The stress intensities are obtainable for arbitrary stresses by numerical integration techniques. Comparisons with existing solutions indicate that the influence functions provide results of suitable accuracy for engineering purposes. The results indicate that the stress-intensity factor is not strongly dependent on the parameter Ri/h or on whether the crack is longitudinal or circumferential. Details of the variation of K along the crack front are not obtainable from the influence functions, only “root-mean-square (RMS)-averaged” values are generated. However, such values are useful in the analysis of the growth of semielliptical cracks, and the results presented should be of wide use in the analysis of such cracks under complex stress conditions.
Plastic Flow Normalizing the Fatigue Crack Propagation Data of Several Steels
Authors: Krafft JM
Published: March 2009

Taken from a recent Naval Research Laboratory (NRL) report, this paper advances author's earlier efforts to associate plastic flow with fatigue crack growth characteristics. Success with this could lessen the data required for estimates of fatigue crack propagation life of structural elements. The model sees crack growth as a means of strain hardening material elements adjacent to the crack tip to counteract strength losses due to transient stress relaxation/creep and environmental surface attack. It defines limiting growth rates in terms of fixed as well as of strain-limited environmental action. Data on some 16 steels are compared to measured stress-strain data using the same model equations. Data fits are rather close, and values of the three kinds of data fitting parameters show consistent trends with respect to the yield strength of the steels.
Unified Solution for J Ranging Continuously from Pure Bending to Pure Tension
Authors: Ernst HA
Published: March 2009

This paper addresses the problem of determining J for a ligament subjected to arbitrary tension-bending loading, presenting a solution for J in terms of the load displacement characteristics. Several aspects of the problem are considered. First the Merkle-Corten analysis (MCA) for the compact specimen (CT) is reviewed, emphasizing its basic assumptions. Then the problem is stated in a general way and solved for J by assuming suitable relations between load and displacement. This results in a unified solution ranging continuously from pure bending to pure tension. The result agrees with previous investigators in the limits of pure bending and pure tension and closely approximates the MCA result for small tensile component (0.6 < a/W) in the CT. The two analyses are extensively discussed in the light of the constitutive equation used. The present work is also compared with finite-element results obtained by other investigators for the CT and the single-edge-notch specimen.
A Perspective on R-Curves and Instability Theory
Authors: McCabe DE , Ernst HA
Published: March 2009

Several aspects of elastic-plastic R-curve theory and instability analysis are discussed. It is shown how material flow property effects can be incorporated into the R-curve in place of the more common practice of incorporation into J crack drive. Formulas for deformation theory J that adjust for slow-stable crack growth in compact (CT) and center cracked tension (CCT) specimens are presented. For cases of extremely large crack extension where conditions of deformation theory J are violated, an expression for modified J also is presented. JR-curve data obtained from a 4T size compact specimen were used to predict instability in a displacement controlled CCT test for 2024-T351 aluminum.
Extension of a Stable Crack at a Variable Growth Step
Authors: Wnuk MP , Mura T
Published: March 2009

This study has been inspired by two proposed models for stable crack growth described by Sih and Kiefer (1979) and Wnuk and Sedmak (1980). Basic assumptions of the second model are reexamined and refined. Although the mathematical analyses involved in both approaches are widely different, it is shown that the physical assumptions underlying these two models are analogous. Both treatments assume a “quantum” nature of crack growth by representing extension of a stable crack as a sequence of steps each of which is executed as a finite jump in the current crack length. While Sih and Kiefer employed the numerical approach to treat the three-dimensional (3D) elastic-plastic fracture problem, here a highly idealized line-plasticity model, modified by an addition of the final stretch growth law, is used.

In earlier final stretch model the quantities essential in the formulation of the growth law, such as the growth step Δ and the opening constants δ or J, were assumed to be material constants. Now it is demonstrated that the first of these assumptions may be relaxed and replaced by a more general requirement of the constancy of the ratios COD/Δ or J/Δ. Indeed, a self-consistent theory may be constructed if only the ratio of a certain measure of the apparent material fracture toughness to the size of the growth step is maintained constant throughout the slow growth phase.

It is shown that variations in the growth step result in reduction of the true and apparent fracture toughnesses associated with the quasi-static crack, which are represented respectively by the tearing modulus δ̂/Δ and any suitable resistance parameter such as J-integral, COD, or extent of the plastic zone generated at the crack front. It is concluded that the models that are based on ideal plasticity and that ignore variations in the growth step tend to overestimate material ability to sustain a stable crack, and thus lead to non-conservative predictions regarding occurrence of terminal instability.
Progress in The Development of Multispectral Glasses Based on The Fluorides of Heavy Metals
Authors: Drexhage MG , Bendow B , El-Bayoumi O , Brown RN , Banerjee PK , Loretz T , Moynihan CT , Shaffer JJ , Temple PA , Bennett HE
Published: March 2009

Considerable progress has been made recently both in the characterization of existing heavy metal fluoride glasses and in the development of new compositions with extended IR transmission. We here report results of continuing investigations of optical and physical characteristics of fluorozirconate type glasses, including absorption, scattering, and mechanical properties. We also report IR edge measurements of new fluoride glasses based on ThF4 and BaF2, which display extended IR transparency and potentially lower minimum absorption compared to fluorozirconates. These developments indicate that heavy metal fluoride glasses are highly promising for a variety of multispectral applications.
Intensity Dependent Absorption and Laser Induced Catastrophic Damage in Diamond Turned and Mechanically Polished Cu Mirrors at 1.06 μm
Authors: Koumvakalis N , Lee C-S , Bass M
Published: March 2009

Intensity dependent absorption and multiple pulse induced failure of mechanically polished and diamond turned Cu mirrors were investigated at 1.06 μm. A Q-switched single longitudinal and single transverse mode Nd:YAG laser operating at 10 Hz was the irradiation source in the experiments. Repetitively pulsed calorimetry was used to measure the absorption and to record the onset of the multiple pulse-induced failure at high intensities. The absorptance was found to increase with increasing intensity. The change was compared to that predicted by the Drude model where the increase in absorptance is related to temperature. A spot size dependence of the laser damage intensities was observed which is suggestive of the role of laser induced stresses in the failure process.
Polarization Sensitive Laser Calorimetry
Authors: Miles P
Published: March 2009

Techniques used currently to determine bulk and surface laser aborption coefficients of highly transparent materials have drawbacks both inherent and practical that limit their accuracy. Conventional bar calorimetry attempts a two-coefficient characterization of nine separate physical absorption sites. Photo-acoustic techniques require in situ calibration sensitive to sample geometry and material.

This paper proposes a new technique in which a set of conventional ballistic laser calorimetry measurements are made on a single prismatic sample. Systematic changes in the polarization and direction of propagation of the laser beam can lead to an explicit determination of individual surface and bulk absorption coefficients. An equilateral prism sample provides a set of independent measurements sufficient to establish the bulk absorption in each of three internal paths and two absorption components on each of the three surfaces. This geometry can be used, in principle, for materials with refractive indices less than 2; more practically, for indices less than 1.7. For higher indices, a truncated prism is proposed which allows seven independent measures to deduce eight absorption components. An assumption of constant surface anisotropy is proposed to complete the analysis. Design criteria for the prism shape are presented, along with analytical expressions for all relevant absorption experiments, and for the simplest cases of uniform, isotropic high and low index materials.
Laser Damage to Metal Mirrors at Nonormal Incidence
Authors: Decker DL , Porteus JO
Published: March 2009

Virtually all laser damage experiments have been performed at normal incidence. However, many applications are for nonnormal incidence, and, obviously, it would be appropriate to characterize the surfaces with the intended geometry and polarization.

This paper presents damage threshold data on bare diamond-machined copper at 45-degree angle of incidence at 3.8 μm wavelength. Within experimental uncertainty, the melt threshold for p-polarization is identical to that obtained at normal incidence on the same surface. The threshold for s-polarization is a factor of two larger. The experimental values are compared with theoretical melt threshold calculations and are found to be in reasonable agreement. The polarization dependence is seen to arise from the fundamental infrared optical properties of metals. The relationship between normal incidence and 45-degree incidence thresholds provides a valuable cross-check on the systematic errors in laser damage measurements.
Effects of Deuterium Treatments on the Optical Properties of Fused Silica
Authors: Kumar B , Fernelius NC , Detrio JA
Published: March 2009

Flame produced fused silica, the process used by all American manufacturers, contains a large amount of OH−. The fundamental OH− vibration in SiO2 is at 2.75 μm and its first overtone is at 1.38 μm. Much of the optical absorption at 1.3 μm is due to the wing of the 1.38 μm absorption band. Stone and Burrus[1] described a deuterium treatment given optical fibers to transform the OH− absorption to OD− whose fundamental is at 3.72 μm and first overtone at 1.85 μm. Here we describe some related treatments given to Suprasil II window samples. Spectral traces show that the 1.38 μm absorption peak is diminished while a new absorption peak appears at 1.85 μm. Similar changes appear in the spectrum between 2 and 4 μm. 1.3 μm laser rate calorimetry performed before and after treatment on the sample showing the most complete H↔D exchange exhibited a drop in absorption value to about 1/5. Thus we conclude that over 80% of the optical absorption in Suprasil II at 1.3 μm is due to the OH− molecule. The method offers a way of improving the performance of flame produced fused silica windows used at 1.3 μm.
Laser Damage Results and Analyses for Ultraviolet Reflectors Under Multiple-Shot Irradiation
Authors: Foltyn SR , Newnam BE , Jolin LJ
Published: March 2009

In a continuing program intended to evaluate and optimize multi-layer dielectric reflectors for the ultraviolet, additional results are reported.

Standard test conditions at the 248 nm KrF* wavelength are a nominal pulsewidth of 10 ns at a 35 Hz pulse repetition frequency. The 0.6 mm mean spot diam (Io/e2) is effectively increased by testing ten sites at each fluence, with each surviving site irradiated for 1000 shots. In this manner, 50 to 100 sites are tested on each reflector. By plotting the fraction of sites which damaged (%) vs laser test fluence (J/cm2) and employing a linear regression fit to the data, a threshold (0% intercept) and an upper limit (100% intercept) are obtained. Emerging correlations between the slope of the data and physical properties of the coatings are discussed.

We have previously reported damage thresholds averaging 1.5 J/cm2 with a high of 3.0 J/cm2 for a ThF4/Cryolite reflector. Presently, we routinely observe thresholds of 3.0 J/cm2 up to a high of 5.5 J/cm2 for oxide films, particularly those employing Al2O3 or Sc2O3 as the high-index component.

As an initial attempt to ascertain the possible effect of pulse repetition rate, some samples were tested at both 35 pps and 2 pps. Within our experimental uncertainty, no difference in threshold was observed.
Graded-index Antireflective Coatings for High Power Lasers Deposited by the Sol-Gel Process
Authors: Lowdermilk WH , Mukherjee SP
Published: March 2009

Gradient-index alkali borosilicate antireflection films for use in lase systems were deposited by the sol-gel process. Laser damage thresholds of these films, measured with 1.07μm, 1-ns pulses, were four times greater than thresholds of widely-used, multilayer, antireflection coatings.
Preparation of Thin Amorphous Films by E-Beam Evaporation from Multiple Sources
Authors: Farabaugh EN , Sanders DM , Wilke ME , Hurwitz SA , Haller WK
Published: March 2009

E-beam codeposition was used to produce thin films in the system ZrO2-SiO2. Bk-7 glass, heated to 325 °C was used as substrate material for these depositions. The films, thus produced were studied by X-ray Diffraction and Scanning Electron Microscopy Techniques. These studies yielded information on the dependence of film crystallinity on composition and substrate temperature. Particular attention was paid to the compositional range in which the structure of the film changes from polycrystalline to amorphous. The change in film structure is easily determined from the change in the XRD patterns. Different film structures were observed using SEM methods.
Improved Si-Based Coating Materials for High Power Infrared Lasers
Authors: Pawlewicz WT , Martin PM
Published: March 2009

Data are presented to demonstrate that alloying of Si with H during thin film coating deposition reduces coating absorption at important infrared laser wavelengths such as 1.06, 1.315 and 2.7 μm by more than an order of magnitude compared to pure Si coatings. These results contradict earlier beliefs that the presence of H in Si was undesirable because of its association with H2O. It appears that absorption values approaching state-of-the-art for near-infrared coatings can now be obtained for a material with many attractive physical properties such as very high refractive index, outstanding hardness and scratch-resistance, glassy structure, non-hygroscopicity and general environmental stability and durability. In particular, an absorption coefficient of 3 cm−1 has been obtained at a wavelength of 2.7 μm for a Si1−xHx alloy with x = 0.12. The Si1−xHx coatings are made by reactive sputtering, and cannot be made by conventional evaporative techniques. Controlled deposition of coatings with specific compositions and optical properties is briefly described, and optical property-composition relationships are presented for the alloy mixing interval 0 < x < 0.4. The same sputtering system is used to deposit the low index material SiO2 by simple exchange of H2 for O2 in the sputtering gas, making possible straightforward multilayer coating fabrication. Reflectance spectra for Si1−xHx/SiO2 all-dielectric mirrors and dielectric-enhanced Au and Al mirrors are presented.