bluuebunny/crossref_metadata_2025 huggingface dataset:
Elastic Field Surrounding a Rapidly Tearing Crack
Authors: Kobayashi AS , Lee OS
Published: March 2009

The transient elastic stress field surrounding a rapidly tearing crack in a single-edged notch (SEN) specimen is analyzed by dynamic photoelasticity using a 16-spark gap Cranz-Schardin camera system. The 1.6-mm-thick annealed polycarbonate SEN specimens produced rapidly tearing cracks with approximately 11-mm-long necked regions which were modeled as Dugdale strip yield zones. In addition, the wake of the residual compressive stress along the rapidly tearing crack was modeled statically by a single force parallel to the crack and acting close to the physical crack tip. Theoretical isochromatics generated by this residual-stress-corrected, propagating Dugdale model of a rapidly tearing crack agreed reasonably well with those obtained experimentally by dynamic photoelasticity.

The experimental analysis showed that the length of Dugdale strip yield zone remained essentially constant through much of the rapid tearing. The crakc-tip opening angle also remained constant, while the crack-mouth opening displacement increased during the terminal stage of crack propagation.
Elastic-Plastic Analysis of a Nozzle Corner Crack by the Finite-Element Method
Authors: Brocks W , Erbe H-H , Noack H-D , Veith H
Published: March 2009

The paper presents the results of an elastic-plastic three-dimensional finite-element analysis for a nozzle corner crack in a pressurized reactor test vessel. The calculations were performed by the finite-element program ADINA using the von Mises yield condition and isotropic hardening. The crack plane was taken parallel to the axis of the vessel and the crack front straight and perpendicular to the symmetry line of the nozzle corner in order to obtain the worst position for a nozzle corner crack. The calculations were performed up to that pressure level where general yield of the ligament in the nozzle corner section takes place.

For the chosen crack length, which is relatively small in comparison with the ligament, the stress normal to the ligament plane and the crack-opening displacement have a maximum in the center of the crack. The differences between the maximum and minimum values along the crack front increase rapidly in the plastic range when the pressure load is raised above half of the general yield pressure. The results of the finite-element analysis are compared with figures obtained from analytical procedures of elastic-plastic fracture mechanics.
Elastic-Plastic Finite-Element Analysis for Two-Dimensional Crack Problems
Authors: Hilton PD , Gifford LN
Published: March 2009

The specialized finite-element program, PAPST (plastic axisymmetric and planar structures), has been developed by the Navy for analysis of elastic-plastic crack problems. After a number of years of PAPST development, internal usage [1,2]3 and refinement, preliminary documentation [3] has now been issued for public release. PAPST includes a finite strain treatment [4] (with a small strain option) for incremental (J2) plasticity. Both power-hardening and multilinear models for uniaxial response are available. The singular core element [5] can be employed to enforce the Hutchinson-Rice-Rosengren crack-tip singularity for power-hardening materials [6, 7] while the enriched element [8] may be used to model crack-tip response for the multilinear material model. For crack problems, both path values for the J-integral and values based on the amplitude of the singular solution can be automatically computed.

PAPST has been used within the Navy research and development community to evaluate response of specimens of varying size, geometries, and material properties. Results for planar and axisymmetric configurations are presented to demonstrate the applications of PAPST to elastic-plastic crack problems.
Elastic-Plastic and Fully Plastic Analysis of Crack Initiation, Stable Growth, and Instability in Flawed Cylinders
Authors: Kumar V , German MD , Shih CF
Published: March 2009

In this paper a procedure has been developed for examining crack initiation, stable growth, and instability in flawed cylinders. Elastic and fully plastic solutions are presented for cylinders containing axial and circumferential cracks located at the inner surface. In the case of an axial crack the loading is due to internal pressure and a plane-strain analysis is carried out. The circumferentially cracked cylinder is loaded by remote uniform tension and is treated as an axisymmetric problem. The solutions are based on the deformation theory of plasticity and employ a special incompressible finite-element method. Solutions cover a broad range of values for the wall thickness to radius ratio, crack length to wall thickness ratio a/b, and strain-hardening exponent n. The relevant crack parameters such as the J-integral, crack mouth opening displacement, and load-point displacement are suitably normalized and tabulated. Accuracy of the elastic solutions is assessed by a comparison with available literature solutions and some other consistency checks.

By appropriately combining the elastic and fully plastic solutions developed, simple estimation formulas are derived through which the relevant crack parameters can be readily computed in the entire range of elastic-plastic deformation. Corresponding results for some illustrative problems are compared with detailed finite-element calculations based on both flow and deformation theories of plasticity. Example J-integral crack driving force diagrams are presented for materials like A533B and 304 stainless steel. Since equilibrium of crack growth requires that applied J equal the material resistance, a superposition of the material JR-curve on such diagrams yields complete information regarding crack initiation, amount of stable growth, instability, and the overall deformation behavior.

Finally, the instability of crack growth under J-controlled growth conditions is examined along the lines of the tearing modulus, TJ, approach. J versus TJ stability diagrams are presented for both axial and circumferential cracks covering a broad range of practical problems of interest. Instability develops when the applied tearing modulus exceeds the material resistance to crack growth. Effects of material properties, flaw size, and cylinder dimensions, including system compliance, on the crack growth and instability phenomenon are investigated in some detail.
Consistency Checks for Power-Law Calibration Functions
Authors: Parks DM , Kumar V , Shih CF
Published: March 2009

Recently, considerable numerical effort has been devoted to obtaining solutions to crack problems in incompressible J2 deformation theory materials of pure power-law type (ε ∞ σn). Following Il'yushin's observation of the scalability of such solutions, many investigators have conducted broad parametric studies on crack length and material exponent, and have tabulated normalized J and deformation magnitudes. Due to numerical difficulties such as slow convergence, incompressibility, or inadequate finite-element mesh refinement, the solutions do not always agree.

We outline the basis for a very stringent general test of the “quality” of proposed solutions by applying the well-known equivalence of J and energy difference rate with respect to crack length.

The test is applied to data available in the literature, and conclusions are drawn as to their accuracy.
Ductile Growth of Part-Through Surface Cracks: Experiment and Analysis
Authors: White CS , Ritchie RO , Parks DM
Published: March 2009

It is an essentially open question as to how well characterizations of through-thickness crack growth based on parameters such as J, crack-tip opening displacement, and tearing modulus describe ductile cracking in important structural configurations such as the part-through surface-cracked plate.

In this work we compare experimental observations and predictions of ductile crack extension in surface-cracked plates subject to bending. Predictions are made by performing finite-element analysis of this three-dimensional geometry using the line-spring model, in conjunction with experimental plane-strain crack growth data from R-curves obtained from through-thickness-cracked compact-tension specimens.

Analysis of the surface flaw is based upon the incremental plasticity theory line-spring element, which has been incorporated into the ABAQUS© general-purpose finite-element program.

The material under study is a low-alloy bainitic pressure vessel steel; namely, fossil energy ASTM A542, Class 3.

Results show that for the crack configuration considered here the amount of stable tearing is quite uniform along the crack front as is the local value of the J-integral. Crack growth initiation occurs at similar J's for both through-crack and surface-crack specimens, but the surface-crack specimens tested exhibit a higher apparent tearing modulus.
J-Integral Analysis of Surface Cracks in Pipeline Steel Plates
Authors: King RB , Cheng Y-w , Read DT , McHenry HI
Published: March 2009

A capability for direct experimental evaluation of the J-integral in surface-cracked members under elastic-plastic deformation is useful for providing understanding of the driving force for fracture. In addition, such a capability makes it possible to evaluate analytical and numerical predictions of J. Experimental procedures have been developed for direct evaluation of J at the root of surface cracks from quantities measured at the specimen surfaces. These procedures rely on the assumption that the line J-integral around the root of a surface flaw is sufficiently path-independent for practical purposes. Arguments in favor of this assumption are made.

Experimentally measured J-integral results are presented for specimens containing surface cracks. Several specimens of pipeline steel 16 mm thick and 75 to 100 mm wide, containing surface cracks varying in length from 31 to 48 mm and in depth from 5.6 to 10.5 mm, were loaded in tension, and the J-integral was evaluated. Plots of measured J as a function of applied stress show a parabolic dependence followed by a nonlinear region and a vertical asymptote at the stress corresponding to net section yield. The experimental results are used to evaluate a simplified line-spring model for predicting J, and the model results compare favorably with the experimental data.
Use of J-Integral Estimation Techniques to Determine Critical Fracture Toughness in Ductile Steels
Authors: Green G , Miles L
Published: March 2009

The use of J-integral estimation techniques is discussed with reference to the evaluation of fracture toughness values for ductile materials. Two applications are considered, tensile plates containing elliptical surface cracks and two specimens designed to produce Mode II sliding shear.

In all cases good agreement was obtained between critical fracture toughness values obtained using J-integral estimation techniques and those obtained in established specimen geometries or by using fractographic techniques. Caution is advised in ensuring that the specimen geometry utilized for J-integral analysis is sufficiently constrained to produce a crack-tip stress-strain field uniquely characterized by the J-integral.
Stress Concentrations Due to Sliding Grain Boundaries in Creeping Alloys
Authors: Lau CW , Argon AS , McClintock FA
Published: March 2009

The most dominant singular stress distributions caused by grain-boundary sliding accommodated by power-law creep have been determined at hard grain-boundary particles and at triple grain junctions, where cavitation and eventual creep cracking are frequently observed. Finite element computations have been used to connect these local stresses to the far-field stresses. These finite element analyses incorporate a specially formulated power-type singularity element, a new method of simulating periodicity and symmetry boundary conditions, a scheme for automatic variable step selection for stable time integration, and a method to bypass the influence of incompressibility. The deviatoric stresses obtained from the finite element results show very good agreement with the dominant singularity solutions, and provide accurate estimates of the generalized stress intensity factors.
Effects of Creep Recovery and Hardening on the Stress and Strain-Rate Fields Near a Crack Tip in Creeping Materials
Authors: Kubo S
Published: March 2009

It is thought that creep recovery may be one of the main causes of acceleration of crack growth rates under variable loads. To explore this possibility, the effects of creep recovery and hardening on the near-tip fields are examined in this paper. Robinson's constitutive relation, which is based on the Bailey-Orowan model, is used to take these effects into account. In this model, the strain rate is proportional to the nth power of an effective stress, which is the difference between applied stress and internal stress. The rate of the internal stress is given by the difference between a hardening term and a recovery term, which are proportional to the strain rate divided by the βth power of the internal stress and the (n − β)th power of the internal stress, respectively.

It is found that the Hutchinson-Rice-Rosengren-type singular fields prevail near a creep crack tip irrespective of the combination of the material parameters n and β. When β < n − 1, the “steady-state creep conditions” prevail near the crack tip; when β > n − 1, the “initial-state creep conditions” prevail, under which the internal stress is small compared with the applied stress.

The intensities of the singular stress and strain-rate fields are obtained rigorously for the case of β = n − 1. For the case of β < n − 1 and β > n − 1, the intensities are estimated by using a hypothesized path independence of the J-integral or the C*-integral. For any combination of n and β, the intensity of strain rate is very high immediately after load increase. Then the strain rate decreases and approaches its steady-state value. On the other hand, for load decrease the strain rate is low immediately after load decrease, and increases until it attains the steady-state value.

From a survey of the values of n and β, the case of β < n − 1 seems to be prevailing for metallic creep. In this case C* can be a characterizing parameter of the near-tip fields. The observed acceleration and deceleration of crack growth rates under variable loads are found to be explained by the present analysis.
On the Time and Loading Rate Dependence of Crack-Tip Fields at Room Temperature—A Viscoplastic Analysis of Tensile Small-Scale Yielding
Authors: Little MM , Krempl E , Shih CF
Published: March 2009

A finite-element analysis of stationary cracks in Mode I small-scale yielding is presented. It is asserted that the deformation of structural metals at room temperature and quasi-static loading rates can be significantly time dependent and so the theory of viscoplasticity based on total strain and over-stress is employed. Loading levels are controlled by the elastic stress-intensity factor K while loading rates are governed by the time rate of change of K. For loading rates varying over six orders of magnitude in the quasi-static range followed by subsequent periods of sustained loading, significant time dependence of the crack-tip fields is predicted. Interpreting the results using two different fracture criteria, it is predicted that the value of K at which crack growth is initiated is loading-rate dependent. Moreover, it also follows that strain-induced crack growth could be initiated during periods of sustained load. The results are strongly suggestive that time-dependent deformation should be considered in design against fracture even at room temperature. Appropriate design approaches, based on the special features of the viscoplasticity model employed, are proposed.
Boundary-Element Analysis of Stresses in a Creeping Plate with a Crack
Authors: Banthia V , Mukherjee S
Published: March 2009

The boundary-element method is used to determine the solution of the problem of a creeping plate with a crack. Particular attention is focussed on the numerical evaluation of a certain line integral—called the C-integral—over various paths around a crack tip, as functions of time for short times. The growth of the creep zone around a crack tip is also studied numerically.
Estimates of the C* Parameter for Crack Growth in Creeping Materials
Authors: Smith DJ , Webster GA
Published: March 2009

This paper discusses methods of determining the creep equivalent of the J-contour integral termed C* for a cracked body subjected to creep deformation. It is shown that C* can be expressed in terms of a creep displacement rate, which can be measured either at the loading points, or locally across the crack plane and an appropriate nondimensional factor. It is found that this factor can be estimated from numerical calculations for a material undergoing power-law hardening plastic deformation or from approximate limit analysis techniques. With either approach the nondimensional factor is found to be dependent on specimen geometry and crack length but to be relatively insensitive to the creep stress index n.

The form of expression developed for C* is particularly suitable when experimental measurements of displacement rate can be made since it enables C* to be determined with little knowledge of the creep properties of the material. Comparisons with experimental creep crack growth data have indicated that the approximate limit analysis estimates of C* are satisfactory for the most part.
Crack Growth in Creeping Solids
Authors: Radhakrishnan VM , McEvily AJ
Published: March 2009

The creep crack growth behavior in a creep-ductile material, 6061 aluminum, and a creep brittle material, Ti-6242, has been investigated. In the creep ductile material an observed load dependency in the relation between the load-point displacement rate, ˙Δ, and the crack growth rate, ˙a, precluded the straightforward application of the C* approach. An alternative approach has been developed in which ˙Δ, ˙a, and P are interrelated through an equation of form ˙Δ∝Pα˙aθ The exponent α determines the contribution of creep deformation to ˙Δ and therefore relates to the creep ductility or creep brittleness of the material. For both materials tested the foregoing relationship was able to describe the experimental results without any systematic scatter.
Influence of Time-Dependent Plasticity on Elastic-Plastic Fracture Toughness
Authors: Ingham T , Morland E
Published: March 2009

The paper describes the results of preliminary experiments to examine the effect of time-dependent plasticity on ductile crack growth, resistance to ductile tearing, and instability in laboratory fracture toughness tests. Experiments on a carbon-manganese (C-Mn) steel and two specimens of A533B-1 steel have shown that unstable ductile fractures can be induced at ambient temperature when 20- and 40-mm-thick compact specimens are held at constant loads between the load approximating that for crack initiation and the maximum load attained in a conventional displacement-controlled fracture toughness test; the time to failure after holding at constant load decreases with increasing constant load level and increasing strain rate prior to load-holding. The data suggest that final failure occurs under conditions paralleling “tertiary creep” behavior. Specimens were loaded at typical rates used in “static” fracture toughness testing and at a slower rate where the maximum load condition was reached in approximately 24 h. Crack extension under constant load has been related to J-resistance curves derived from multispecimen displacement-controlled tests.

The J-resistance curve for C-Mn steel specimens is dependent upon strain rate at rates of loading which are conventionally taken to be representative of “static” conditions. This effect was not observed in tests on A533B-1 steel.
Comparison of Ashing Techniques for Determination of the Inorganic Content of Peats
Authors: Andrejko MJ , Fiene F , Cohen AD
Published: March 2009

In recent years there has been an increased interest in peat both as a precursor of coal and as an alternative fossil fuel. One of the most important tests used to evaluate or describe peat is measurement of its inorganic (or ash) content. Numerous methods for determining ash content have been proposed by various researchers. The purpose of this research, therefore, was to compare ash yields produced from the same samples of peat by several of these methods. These include the present ASTM standards for peat (D 2974) and coal (D 3174), along with more recent developments such as electronic Low Temperature Ashing (LTA).

For this study a series of large bulk samples were utilized from several presently or potentially exploitable peat deposits. These samples represented a wide range of depositional environments, botanical compositions, and inorganic and mineral suites. In some samples the mean difference in ash weight between methods was as high as 26% on a dry weight basis, while in other samples there was little if any significant distinction. The overall results indicate that there is a direct relation between the mineral composition of the inorganic fraction and the tendency for distinct statistical differences in the ash results from the different methods utilized.

The conclusions from this study indicate that a revised standard for the determination of ash content in peat should be considered that would incorporate parts of ASTM D 2974 (peat) and D 3174 (coal) with new procedures utilizing LTA technology.
Geotechnical Classification of Peats and Organic Soils
Authors: Landva AO , Korpijaakko EO , Pheeney PE
Published: March 2009

On reviewing the literature on peat classification, it becomes evident that most of the existing classification systems are based on the use of peats and organic soils as a growing medium in horticulture, agriculture, and forestry, or as a horticultural additive (peat moss), or as a fuel. One exception is the Radforth classification system for peat, which does pertain to engineering applications. Since this system is not based on geotechnical properties, however, it is not in itself sufficient for geotechnical classification.

The term peat as used today also includes a vast range of organic soils: from jelly-like, almost liquid muds whose organic content may not even originate from peat, to extremely coarse-fibrous meshes of woody remnants and fibers. The mud is often referred to as an amorphous-granular peat and the woody mesh as a fibrous peat. These are the only two terms that have been generally adopted by geotechnical engineers, with the inevitable results that each term covers a large range of materials and that considerable overlapping occurs.

An attempt is made in this paper to distinguish between various peats and organic soils on the basis of geotechnical engineering considerations. The existing von Post and Radforth systems are examined with respect to geotechnical applications. These systems are supplemented with routine geotechnical tests yielding numerical values for classification purposes.
A Comparative Study of Preparation and Analytical Methods for Peat
Authors: Schelkoph GM , Hassett DJ , Weber BJ
Published: March 2009

The United States has large deposits of peat, with recoverable fuel value roughly estimated at 538 quads (1015 Btu), which is equivalent to 90 billion barrels of oil. The potential importance of peat as a feedstock for gasification and as a fuel source is currently being evaluated by the U.S. Department of Energy.

Owing to the high moisture content, high volatiles, and fibrous nature of most peats, standard techniques for the preparation and analysis of coal may not always apply to peat. The purpose of this study was to determine whether current preparation and analytical methods used for coal were adequate for characterizing peat and to determine the accuracy of these methods for peat. Peat samples were obtained from four different locations in the United States and were packed under an inert atmosphere. These samples were sent to six laboratories, where ultimate, proximate, heating value, and elemental ash analyses were performed. The results were then statistically correlated, and the various analytical methods were evaluated by the Grand Forks Energy Technology Center as to their validity for peat. These results will be extremely useful in developing ASTM standards and selecting the best techniques for testing and analysis of peat samples.
Undisturbed Sampling of Peat
Authors: Landva AO , Pheeney PE , Mersereau DE
Published: March 2009

Two samples developed at the University of New Brunswick for sampling of peat are described. One is a 100-mm-diameter piston sampler with a Plexiglas insert sample holder and the other is a 250-mm-square block sampler. The samplers have been extensively tested and used in Sphagnum and sedge peat and have also been used successfully in soft-to-almost-fluid organic diatomaceous soils.
Repeated Short-Term Consolidation of Peats
Authors: Ng SY , Eischens GR
Published: March 2009

The behavior of peats under varying loading processes was noted by the authors while working on various geotechnical engineering projects. This paper gives the comparative results of repeated short-term loading tests and continuous one-load consolidation tests on peats. Peat samples were obtained from three separate sites. The test results show that peats undergo significant consolidation when subjected to repeated loadings, comparable to continuous loading. Loading times and frequencies do not significantly affect the rate and amount of compression.

The test results offer a possible explanation for uneven settlements of parking lots and storage areas of lumber yards, coal yards, canneries, etc.
Test Method for Determining the Potential for Decomposition in Organic Soils
Authors: Wardwell RE , Charlie WA , Doxtader KA
Published: March 2009

Engineering properties of organic soils are influenced to a large degree by their organic content. As such, engineering designs for the development of any site underlain by organic materials should consider the potential for decomposition of the organic materials. Most of the highly compressible organic soils are in areas of high water table. Because of this, anaerobic processes will be the primary decomposition mechanisms associated with these deposits. This paper discusses a method of laboratory testing that was established to determine the environmental factors which influence the anaerobic microbial breakdown of organic matter in soils. Soil samples are monitored for anaerobic microbial activity by collecting and analyzing the gas production during the decomposition process. The type of biological activity taking place is indicated by the time rates of gas production, the total amounts of gas produced, and the components in the gas. This paper details the necessary equipment and the procedures needed to conduct these tests without interrupting the biological process. The effects of elevated temperatures on accelerating decomposition are presented.
The Surface Chemistry of Amorphous Synthetic Silica—Interaction with Organic Molecules in an Aqueous Medium
Authors: Iler RK
Published: March 2009

The chemical structure of the silica surface plays a key role in the adsorption and bonding of organic molecules from aqueous solution. This paper summarizes the known variables in surface structure, such as the state of hydration and dehydration, ionic charge, and the presence of aluminum as anionic aluminosilicate sites. These variables affect the degree to which organic molecules are bound to the surface through the three known forces, namely, ionic attraction, hydrogen bonding, and hydrophobic bonding. The latter probably has not been sufficiently widely appreciated in the case of pyrogenic silicas which have surfaces that are partly hydrophobic.
Evaluation of Potential Inhalation Hazard of Particulate Silicious Compounds by In Vitro Rabbit Alveolar Macrophage Tests—Application to Industrial Particulates Containing Hazardous Impurities
Authors: Aranyi C , Gardner DE , Huisingh JL
Published: March 2009

The Rabbit Alveolar Macrophage test was used to evaluate the toxic ranking of a series of particulate samples collected from in-plant control devices from various industrial processes. Generally, low-to-intermediate cytotoxicity was found for samples collected from a steel foundry and from different coal-fired power plants, whereas particulates originating from an aluminum and a copper smelter were highly toxic to alveolar macrophages (AM), as monitored by viability, total cellular protein, and adenosine triphosphate (ATP) levels. In contrast to all others, these two samples also contained soluble components that contributed to their overall in vitro cytotoxicity. The copper-smelter dust and two coal fly ash samples chosen on the basis of their respective high, intermediate, and low in vitro cytotoxicity were used in aerosol exposures to examine their in vivo effects in mice. Observations from our laboratory reported elsewhere demonstrated parallel effects in in vivo assessments of the inhalation toxicity of these samples in the intact animal and thereby substantiated the in vitro data.
Immunological Aspects of Silica
Authors: Burrell R
Published: March 2009

This paper reviews the immunological aspects of silica and silicosis. Since crystalline silica by itself is nonantigenic, emphasis is placed on how silica can effect immunological consequences, on what immunological abnormalities are observed in both spontaneous and experimental forms of silicosis, and on how these immunological activities may influence silicosis.

The effect of silica on immunoglobulin levels, interferon induction, lymphocyte function, and macrophages in the afferent limb of the immune response is critically examined. The toxic and adjuvant effects of silica are discussed in relation to how these effects influence humoral and cellular immune responses to extrinsic and intrinsic antigens.

Finally, the relationship between the immunological effects of silica and immune reactions involving connective tissue antigens is explored in relation to its possible role in the pathogenesis of disease.
An Analysis of Random Pits in Corrosion Fatigue: A Statistical Three-Dimensional Evaluation of an Irregularly Corroded Surface
Authors: Kitagawa H , Tsuji K , Hisada T , Hashimoto Y
Published: March 2009

A method of statistical evaluation based on two-dimensional spectral analysis is proposed for quantitative determination of irregular configurations of an unnotched surface subjected to corrosion fatigue. For the practical use of the spectral analysis new parameters √A, √B, and α2 are used. These parameters, which characterize the autocorrelation function, correspond to the standard deviation of the surface irregularity, mean depth of the corroded surface, and pit size respectively. The method was applied to unnotched smooth specimens made of structural steel and subjected to fatigue in hydrochloric acid. The specimen surface was covered with many randomly distributed pits. From the results of the analysis, it has been made quantitatively clear that increases in the cyclic stress level or the number of load cycles bring about corrosion pits on the surface.
Corrosion-Fatigue Crack Propagation Rates in Commercial 7075 and P/M X7091 Aluminum Alloys
Authors: Santner JS , Kumar M
Published: March 2009

The recently developed powder metallurgy (P/M) alloy X7091 (formerly CT91) has strength characteristics similar to ingot metallurgy (I/M) 7000 series alloys. However, its stress corrosion cracking resistance has been reported to be far superior to the conventional ingot-processed alloys. This suggests that P/M alloy X7091 may have far better corrosion fatigue behavior than I/M 7075-T651. Fatigue crack growth rates between 2.5 × 10−8 and 2.5 × 10−6 m/cycle (10−6 and 10−4 in./cycle) were measured for specimens in both the S-T and T-L orientations. In order to determine the effect of environment on the fatigue crack growth rates, tests were conducted in both an innocuous and an aggressive environment (R = 0.5; f = 0.2 Hz). Since it is known that the fatigue crack growth rates of aluminum alloys are sensitive to small amounts of water vapor, gaseous nitrogen with a dew point of −60°C (−75°F) was chosen as the innocuous environment. An aerated 3½% NaCl solution was used as the corrosive environment.

The corrosion fatigue crack growth rates were, on the average, ten times slower for the P/M X7091 alloy than the I/M 7075 alloy tested in both the T-L and S-T orientation. The crack propagation rates for each alloy are similar for both the S-T and T-L orientations when tested in a given environment. While the I/M 7075 specimens had a ten times slower growth rate in the gaseous nitrogen environment than those measured in the salt water, there was no such dramatic change between the crack growth rates measured in the two environments for the P/M X7091 alloy.

The crack closure stress was measured for specimens tested in the corrosion environment to determine if it was greater than the applied minimum stress. It was found that while the I/M 7075 alloy had no measurable closure stress, the P/M X7091 alloy had sufficient closure to reduce the effective cyclic loads by up to 40% of the applied load amplitude. The presence of a measurable closure stress in the 3½% salt water environment is correlated with the P/M X7091 alloy, which has a lower corrosion-fatigue crack growth rate than the I/M 7075 alloy.

Fractographic examination of the corrosion-fatigue fracture surfaces suggests that copious amounts of corrosion debris correspond to where the crack closure was greatest. This debris is absent when the crack closure stress was less than or equal to the applied minimum stress. This observation suggests that in addition to the plastic deformation zone in the wake of the fatigue crack, the presence of corrosion products between the fracture surfaces can increase the closure stress if the general corrosion rate of the fatigue fracture surface is small.
Fractography and Mechanisms of Environmentally Enhanced Fatigue Crack Propagation of a Reactor Pressure Vessel Steel
Authors: Törrönen K , Kemppainen M
Published: March 2009

This paper describes the findings and interpretations of the fractographic survey conducted for the International Cyclic Crack Growth Rate (ICCGR) cooperative group round-robin specimens. Specimens of A533B pressure vessel steel were tested at several laboratories in the United States and elsewhere with the same nominal test parameters. A rather wide scatter of the results was found. A fractographic and metallographic survey was carried out in order to clarify the scatter and to evaluate the micromechanism of the crack growth. The fractographic findings are reported in detail and correlated to the crack growth behavior. A hydrogen-assisted crack propagation mechanism based on the fractography is proposed and applied to the observed crack growth behavior.
Chemistry Effects in Corrosion Fatigue
Authors: Scott PM
Published: March 2009

In principle, there could be as many different types of corrosion-fatigue behavior as there are metal/environment combinations, since each will interact chemically and electrochemically in different ways. Pessimism in the face of such potential complexity would be justified if we could not, from our knowledge of the corrosion properties of the material in its environment, make worthwhile generalizations. The object of this paper is to identify those common threads running through the experimental observations that enable us to deduce which are the important chemical and electrochemical interactions with the environment influencing the fatigue strength, cyclic endurance, or fatigue crack propagation kinetics of a given material or class of materials. Interpretation of the effects of chemical and electrochemical variables is seen to be dependent on both our basic knowledge of surface corrosion and crevice corrosion phenomena and our perception of the relative importance of the crack initiation and propagation phases of corrosion-fatigue failure in particular materials and test specimen geometries.
A Theoretical Evaluation of the Oxygen Concentration in a Corrosion-Fatigue Crack
Authors: Turnbull A
Published: March 2009

The oxygen concentration in a corrosion-fatigue crack has been evaluated theoretically by assuming that oxygen was consumed by cathodic reduction on the walls of the crack and mass transport occurred by diffusion and advection (forced convection), with the latter resulting from the sinusoidal variation of the displacement of the crack walls. By using parameters relevant to a compact tension specimen, the time-dependent distribution of the oxygen concentration in the crack was calculated as a function of ΔK (the range of the stress intensity factor), R-value (minimum load/maximum load), frequency, crack length, and electrode potential. The influence of advection was to significantly enhance the mass transport of oxygen in the crack compared with “diffusion-only” even at low frequencies and low ΔK. Regions in the crack were identified in which advection dominance or diffusion dominance of the mass transport of oxygen occurred.
Environmental Influences on the Aqueous Fatigue Crack Growth Rates of HY-130 Steel
Authors: Fujii CT , Smith JA
Published: March 2009

The influence of chloride ions, pH, potential, and chromate ions on fatigue crack growth rates of HY-130 steel in aqueous solutions were examined. Crack growth rates (da/dN) were determined as functions of stress intensity factor range (ΔK) over the ΔK-interval of approximately 20 to 90 MPA√m, and environmental effects were evaluated by comparison with similar data for HY-130 obtained in air. All fatigue experiments were conducted at a maximum stress intensity factor (Kmax) < (KIscc), a stress ratio (R) = 0.1, a cyclic frequency (f) = 0.1 Hz, and a temperature (T) = 24 ± 2°C.

In the absence of inhibitors, crack growth rates are enhanced approximately threefold by an aqueous environment relative to air. A comparison of results from distilled water, 0.6M NaCl solution, and 0.1N HCl solution suggests that the crack growth rates are not influenced significantly by chloride ions or acid conditions (pH ≃ 1.0). Under alkaline conditions (pH ≃ 12), the crack growth rates are between those observed in air and in distilled water, acid or saline solution. The chromate ion is an effective corrosion fatigue inhibitor for HY-130, as indicated by the coincidence of its da/dN-versus-ΔK curve with that of air. All of these crack growth rates converged at higher ΔK values. Applied cathodic potentials increased crack growth rates beyond those observed under freely corroding conditions in 0.6M NaCl solution. This enhancement in crack growth rates is only observed at ΔK-values above 30 to 40 MPa√m. The results suggest that hydrogen is involved in the crack growth mechanism.
The Use of Notched Compact-Type Specimens for Crack Initiation Design Rules in High-Temperature Water Environments
Authors: Prater TA , Coffin LF
Published: March 2009

This report describes the techniques used and results obtained for fatigue crack initiation of notched compact-type (CT) tests of SA333 Gr.6 carbon steel in air or in autoclaves mostly at 288°C (550°F), 1.05 kg/mm2 (1500 psi) oxygenated water conditions. The fatigue crack initiation life Ni was quantitatively determined from a cycle-by-cycle crack length measurement as the number of cycles of produce 7.6 × 10−2 mm (0.003 in.) of growth from the notch root. Results for several parameters of the experimental program (including temperature, environment, oxygen content, frequency of cycling, notch radius, R-value, and ΔK) are reported. A majority of the tests were run in 288°C (550°F) water at 8 ppm O2 with 5.1 × 10−2 mm (0.002 in.) notch radii, and showed a severe degradation in initiation life, especially at a frequency of 0.00021 Hz (0.0125 cpm), compared with 288°C (550°F) air tests. On the other hand, at 0.021 Hz (1.25 cpm) and 8 ppm O2, decreasing the temperature to 232°C (450°F) restored the life to that of air. Reducing the oxygen level to 0.2 ppm in 288°C (550°F) water was also beneficial. These latter two findings are preliminary because of limited testing.

The test results were interpreted in terms of conventional procedures in which a notch root pseudostress amplitude Sa was calculated for each test and compared with the ASME fatigue data curve for carbon steel. The quantity Sa was obtained from the applied stress intensity range (ΔK) and Neuber notch analysis procedures to account for elasticplastic notch root conditions. The worst-case notch concept was introduced to account for the observed maximum in the fatigue notch factor kf with decreasing notch radii and for the environmental notch sensitivity. For the present study, the worst-case notch radius ρ was 0.165 mm (0.0065 in.).

A procedure is described for calculating Sa and Ni from crack growth data. This procedure assumed a crack to be equivalent to the worst-case notch and provided a good prediction of the ASME fatigue data curve from the ASME crack growth curves in air, both for carbon steel. By using this approach and a conservative threshold stress intensity value for fatigue crack growth in 288°C (550°F), 8 ppm O2 water, a value of Sa was determined below which crack initiation will not occur in this environment, regardless of defect sharpness or frequency of loading. This value of Sa was consistent with the notched CT crack initiation results obtained.
Effects of Cathodic Protection on Corrosion Fatigue
Authors: Floyd Brown B
Published: March 2009

The effects of cathodic protection on corrosion fatigue of alloys can vary widely, ranging from strongly beneficial to strongly detrimental. This paper provides a concise synopsis of the subject, based upon a review of selected literature. Attempts are made to discern important generalizations concerning the effects of various cathodic protection levels on crack initiation and crack propagation in ferrous and nonferrous alloy systems.
The Role of Microplastic Deformation in Fatigue Crack Initiation
Authors: James MR , Morris WL
Published: March 2009

A reference gage technique is used to measure the localized plastic strains which develop within individual surface grains during cyclic loading of A1 2219-T851. These are found to increase more rapidly in grains having large distances of slip between grain boundaries in the plane of the surface. Further fatigue causes cyclic hardening of the surface in the large grains as manifest by a reduction in the microplastic deformation. Maximum values of the local plastic strain and the cycles needed to achieve them are observed to be a function of environmental humidity and of internal hydrogen content.

Humid air is found to decrease the development of microplasticity when compared with fatigue in dry air. Increased quantities of internal hydrogen (although in contents less than 1 ppm) substantially increase the rate of development of microplasticity early during fatigue and later accelerates cyclic hardening of the surface. A model based on a critical fracture strain criterion is formulated and used to calculate the numbers of constituent particles in the alloy fractured during fatigue. The model satisfactorily predicts the enhancement of particle fracture in alloys that contain hydrogen or that are fatigued in dry air. We conclude that the principal effect of these environmental factors on particle fracture arises because they alter the propensity of the surface to undergo microplastic deformation.
Industrial Applications of Titanium and Zirconium
Authors: Kleefisch EW
Published: March 2009

Description

Covers the practical application of titanium and zirconium-materials highly resistant to corrosion and with few design limitations.
Laboratory Shear Strength of Soil
Authors: Yong RN , Townsend FC
Published: March 2009

Description

Describes the development of new test techniques and methods for the evaluation of the laboratory shear strength of soil.
Underground Corrosion
Authors: Escalante E
Published: March 2009

Description

The main purpose of this book is to provide the most recent information on underground corrosion of metals, its evaluation and the factors that affect it.
Power Plant Instrumentation for Measurement of High-Purity Water Quality
Authors: Lane RW , Otten G
Published: March 2009

Description

The publication presents techniques employing various methods of measurement, such as ion chromatography, atomic absorption, specific ion electrode, ion exchange columns, electrical conductivity, a gravimetric method, differential pulse polarography and others. Discussions on methods of sampling, desired point of sampling, and other details are included.
Hazardous Solid Waste Testing: First Conference
Authors: Conway RA , Malloy BC
Published: March 2009

Description

The first in a series of publications provides a basis for new methodology in the testing of industrial solid wastes. This publication is one of the first technical testing manuals for identifying and characterizing hazardous solid wastes in terms of disposal options. The book is divided into five areas:

• Laboratory Extractions and Leaching Procedures

• Large-Scale Leaching Tests Versus Laboratory Tests

• Analysis of Residues, Extracts, soils, and Ground Waters

• Evaluation of Land Disposal Sites and Materials

• Risk Assessment Approaches.
Pesticide Formulations and Application Systems: Second Conference
Authors: Seymour KG
Published: March 2009

Description

STP 795 is the result of a symposium intended to provide an interdisciplinary forum for discussion of the many facets of pesticide formulation and application. This book addresses packaging, granular formulations, and spray-related subjects. STP 795 represents a variety of subjects all contributing to a theme of knowledge about effective, efficient, and safe use of pesticides.
Vertebrate Pest Control and Management Materials: Fourth Symposium
Authors: Kaukeinen DE
Published: March 2009

Description

Succeeds STP 752. 24 papers cover
Sampling and Analysis of Rain
Authors: Campbell SA
Published: March 2009

Description

9 papers describe processes leading to acidic precipitation; techniques used to collect and analyze rain; and quality assurance programs currently used by major acid precipitation measurement networks.
Engineering Dielectrics Volume IIB Electrical Properties of Solid Insulating Materials: Measurement Techniques
Authors: Bartnikas R
Published: March 2009

Description

Fight chapters describe testing procedures suitable for the measurement of dielectric properties of solid insulating materials. They explain why dielectric measurements are made, their specialized uses, and their limitations.
Intravenous Ceftriaxone and Calcium in the Neonate: Assessing the Risk for Cardiopulmonary Adverse Events
Authors: Bradley John S. , Wassel Ronald T. , Lee Lucia , Nambiar Sumathi
Published: March 2009

OBJECTIVES. Unsolicited reports regarding potentially serious adverse drug reactions in neonates and young infants were reported to the Food and Drug Administration, leading to changes in the package label for ceftriaxone. This report describes and summarizes the reported cases that led to safety concerns regarding the concurrent administration of intravenous ceftriaxone and calcium in this age group.

METHODS. Nine reported cases were assessed. The Food and Drug Administration Adverse Event Reporting System database was searched for potential drug interactions in patients who were receiving concomitant ceftriaxone and calcium therapy.

RESULTS. Eight of the reported 9 cases (7 were ≤2 months of age) represented possible or probable adverse drug events. There were 7 deaths. None of the cases were reported from the United States. The dosage of ceftriaxone that was administered to 4 of 6 infants for whom this information was available was between 150 and 200 mg/kg per day. The rate of occurrence of these serious adverse drug reactions cannot be accurately determined from available data.

CONCLUSIONS. The concurrent use of intravenous ceftriaxone and calcium-containing solutions in the newborn and young infant may result in a life-threatening adverse drug reaction. Contributing factors for infants in this report may include the use of ceftriaxone at dosages higher than those approved by the Food and Drug Administration, intravenous “push” administration, and administration of the total daily dosage as a single infusion.