bluuebunny/crossref_metadata_2025_split huggingface dataset:
Prediction of Structural Crack Growth Behavior under Fatigue Loading
Authors: Hopkins SW , Rau CA 
Published: March 2009

Structural components which undergo operational fatigue cycles have historically been designed for fatigue resistance based upon crack initiation data generated on smooth and notched laboratory speimens. More recently, reliability has been improved by using linear elastic fracture mechanics (LEFM) to assure that flaws, even if present, cannot grow to a dangerous size during service. The methodology and input data utilized for LEFM evaluation are described, and the impact of variations in key input parameters are discussed in detail. Specifically, the paper describes the sensitivity to (1) loading parameters: applied cyclic stresses, mean stresses, residual stresses, load spectrum, and stress distributions, (2) local crack driving force: crack size, shape, orientation, growth, and growth mode, (3) materials properties: crack growth rate constants, crack growth threshold, and response to spectrum overloads, and (4) initial flaw size, with and without nondestructive inspection.Presently, LEFM analyses are often deterministic and utilize conservative (worst-case) assumptions for all input parameters which are not known. The assumptions that all worst-case conditions occur simultaneously lead to extremely conservative designs which may be economically unacceptable. Probabilistic fracture mechanics methods have been developed which incorporate the statistical variations or uncertainties that actually exist and establish a more realistic quantitative basis for design allowables and accept/reject criteria, which optimize the cost/risk trade-offs that must be made.
Translation of Laboratory Results to Field Conditions: The Role of Aquatic Chemistry in Assessing Toxicity
Authors: Lee GF , Jones RA 
Published: March 2009

One of the most significant problems facing the water quality management field today is the translation of laboratory-derived aquatic toxicology criteria and standards to natural water field conditions. This problem is caused, in part, by the markedly different chemical environments that frequently exist in laboratory toxicity tests and the field. Normally, laboratory-developed water quality criteria are derived from bioassays in which the contaminant is presented to the organism in a completely or nearly completely available form or forms; however, under field conditions, many contaminants exist in a variety of forms only some of which are available to aquatic organisms.
Guidance is provided on how to use knowledge of the aqueous environmental chemistry of the contaminant or contaminants of concern to detect situations in which there may be markedly different toxicity levels under field and laboratory conditions. A hazard-assessment approach is outlined by which maximum use can be made of existing laboratory bioassay data and environmental chemistry in site-specific water quality evaluation.
Evaluation of Technical Limitations to Determining Organic Contamination in Subsurface Soils
Authors: Baty CJ , Perket CL 
Published: March 2009

The major technical impediments to quantitative determination of organic contamination in subsurface soils are the following: lack of an established procedure, heterogeneous specimens with unconfirmed representativeness, and difficulty in assessing method accuracy. These technical limitations have been discussed with respect to a specific case study at the site of a former wood-preserving plant.
Subsurface soil specimens were obtained from the former wastewater drainage trench and lagoons, Soxhlet extracted with methylene chloride, and analyzed by gas chromatography (GC) and high-pressure liquid chromatography (HPLC) for phenolic compounds and polynuclear aromatic hydrocarbons (PNAs), respectively. Interlaboratory and intralaboratory precision was evaluated and was shown to be poor. Accuracy was not determined.
Excavation and soil test borings were compared for utility and sensitivity in subsurface sampling. Data obtained from soil test borings alone did not adequately depict the subsurface patterns of contamination evidenced by the excavation.
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.
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.
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.
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.
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.
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.
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.
A Criterion Based on Crack-Tip Energy Dissipation in Plane-Strain Crack Growth Under Large-Scale Yielding
Authors: Saka M , Shoji T , Takahashi H , Abé H 
Published: March 2009

In order to assess the proper resistance of elastic-plastic materials for stable crack growth in Mode I under plane-strain conditions with large-scale yielding, a fracture criterion based on a rate of the crack-tip energy dissipation with crack extension was proposed. The criterion can be expressed as TW = (TW)c, where TW is a newly developed tearing parameter defined as TW = (1/R)(E/σ02)(dp/da). The parameter TW is a dimensionless representation of the increment of plastic work done, dp/da, in a circular region of characteristic radius R at the growing crack tip, and TW is related directly as the amplitude to the singularity field at a growing crack tip.
A procedure of experimental determination of (TW)c was described, where the crack-tip energy dissipation, Wp, was evaluated by means of the recrystallization-etch technique, and the width of recrystallized region observed parallel to the growing crack surface was used as the characteristic radius R. With special reference to a nonlinearity of the J-resistance curve for a wide range of crack extension, a conventional estimation procedure of the rate of crack-tip energy dissipation in terms of γ[=(½)β2σ02R(TW)c] was also described.
Furthermore, the TW criterion was verified experimentally and numerically in comparison with other candidate tearing parameters TJ[=(E/σ02)(dJ/da)] and Tδ[=(E/σ0) (dδ/da)]. A significant superiority of TW over TJ and Tδ [crack-opening angle (COA)] was emphasized as a characterizing parameter for crack growth. It was shown that the critical value of TW during crack growth was not affected by specimen size, side groove depth, and an amount of crack extension.
Evaluation of J-Integral for Surface Cracks
Authors: Shiratori M , Miyoshi T 
Published: March 2009

A new finite-element program has been developed in order to analyze the stress-intensity factor K and J-integral for surface cracked plates and shells. The program is composed of the flat shell elements and the line spring elements which are based upon the line spring model proposed by Rice. Summary of results analyzed by this program is as follows:
1. In the analysis of K for surface-cracked rectangular plates, the results have been in good agreement with the three-dimensional finite-element results obtained by Raju and Newman. The computing time is one order less than the three-dimensional finite-element analysis. 2. Nearly the same results as those by Parks have been obtained in the analysis of the J-integral for surface-cracked rectangular plates. 3. As a practical application of this program, K and J have been analyzed for surface-cracked part-circular cylindrical shells. The effect of curvature has been found to lower the values of K and J slightly. Therefore, estimates of K and J by those of flat plates for the equivalent crack configuration give conservative results.
Effects of Thickness on J-Integral in Structures
Authors: Sakata M , Aoki S , Kishimoto K , Kanzawa M , Ogure N 
Published: March 2009

The distribution of the Ĵ-integral, an extension of the J-integral, is calculated along the crack front of compact specimens of varying thicknesses by a three-dimensional elastic-plastic finite-element method. The Ĵ-integral takes the maximum value at the midthickness and smaller values near the plate surfaces, and the Ĵ-value at the midthickness coincides with the J-value determined from the computed load versus load-line displacement curve by using the Merkle-Corten formula. These results explain why the plane-strain fracture toughness value JIc can be experimentally determined by using specimens of moderate thickness.
To avoid the expense of three-dimensional computations, an empirical formula based on a two-dimensional finite-element method is proposed to determine the J-value which coincides with the Ĵ-value at midthickness in a cracked structure. Experimental results on compact specimens of 304 and 4340 steels and also on rotating disks of 4340 steel indicate that the onset of crack growth in a structure with finite thickness can be estimated by using the empirical formula and the JIc-value of the compact specimen.