bluuebunny/crossref_metadata_2025_split huggingface dataset:
Effect of Temperature, Microstructure, and Stress State on the Low Cycle Fatigue Behavior of Waspaloy
Authors: Stahl DR , Mirdamadi M , Zamrik SY , Antolovich SD 
Published: February 2009

The low-cycle fatigue (LCF) behavior of Waspaloy was studied in uniaxial and torsional loading for two heat treatments at 24 and 649°C. It was shown that for both heat treatments deformation and failure mechanisms were independent of stress state at 24°C. Deformation occurred by precipitate shearing and the formation of intense shear bands for the coarse-grain/small-precipitate (CG-SP) condition and by precipitate looping and loosely defined shear bands for the fine-grain/large-precipitate (FG-LP) condition. Failure in both microstructures was associated with the formation of shear cracks.
At 649°C deformation and failure mechanisms for the FG-LP condition were independent of stress state, and the mechanisms were similar to those observed at 24°C. For the CG-SP condition, the situation was different. Failure occurred on principal planes when tested in torsion and on shear planes when tested in uniaxial tension. The mechanism transition is interpreted in terms of deformation mode and microstructural instability.
In general, there was a more pronounced decrease in life with increasing temperature for uniaxial specimens than for torsional specimens. This result is interpreted in terms of an environmental interaction that is accelerated by a comparatively significant dilatational strain component.
Effect of HIP on Elevated-Temperature Low Cycle Fatigue Properties of an Equiaxed Cast Superalloy
Authors: DL Anton , LH Favrow 
Published: February 2009

A typical high strength equiaxed cast superalloy, B-1900, was tested in the fully heat-treated condition, preceded by an optional hot isostatic pressing (HIP) cycle. Fully reversed constant total strain amplitude testing was carried out at temperatures ranging from 760 to 982°C in air. The HIP cycle successfully eliminated all non-surface connected porosity, and specimens, machined from the center of test bars, were totally pore free. Changes in grain boundary carbide morphology and γ′ size also ensued from the HIP treatment. Fatigue crack initiation sites were identified in scanning electron microscopy (SEM) fractographic analysis along with modes of crack propagation.
An enhancement of fatigue life by a factor of 6 to 8 was realized in the HIP alloy at temperatures of 871°C and below. Above this temperature no effect of HIP was observed. Cracks of HIP specimens initiated at grain boundary-surface intersections. Fatigue crack initiation was enhanced by local oxidation of surface-connected carbides, with fatigue crack propagation being predominantly intergranular. The non-HIP specimens typically contained surface cracks which propagated through near surface clusters of microporosity which in turn were formed adjacent to the interdendritic carbide networks. The HIP treating of equiaxed cast superalloys for turbine blade applications completely closed interdendritic and intergranular microporosity and caused grain growth to occur. This led to enhanced fatigue life at low temperatures where oxidation of grain boundary carbides was minimized. Fatigue life enhancement due to HIP was separated into microstructural modifications effecting yield stress and grain boundary structure.
Effect of Superimposed Stresses at High Frequency on Low Cycle Fatigue
Authors: J-Y Guedou , J-M Rongvaux 
Published: February 2009

The effects of superimposed stresses at high frequency on low cycle fatigue behavior were studied on two aeronautical alloys (Ti 6-4 and Inconel 718) in terms of crack initiation, crack propagation, and failure. It is shown that, if the minor cycles have limited amplitudes, not more than 10 to 15% of low cycle fatigue stresses, the life is monitored by the maximum stress of the cycles. This is correlated with the fact that, in this case, the endurance limit of the material is not exceeded. The same criterion is suitable for crack initiation of Inconel 718, but not for Ti 6-4 which is, in all cases, much more sensitive to mixed fatigue than Inconel 718.
The crack propagation regime is ruled by minor cycles only beyond an observed transition ΔK value. For both materials, linear cumulation rules are inadequate for predicting the number of cycles to failure and for calculating the crack growth rates in mixed fatigue.
Low Cycle Fatigue Characterization of a HP-IP Steam Turbine Rotor
Authors: V Bicego , C Fossati , S Ragazzoni 
Published: February 2009

Results of an extensive low cycle fatigue characterization of HP and IP stages of a 1Cr-Mo-V steam turbine rotor are presented. Uniaxial strain controlled fatigue tests were carried out at 480 and 540°C, with hold times up to 24 h and strain rates down to 3 × 10−6 s−1. Moderate life reductions due to long hold periods were found only in tests with strain ranges less than 0.8%, though microstructural observations revealed evidence of creep damage morphologies in a few tests with 24 h hold times carried out at high strain ranges. Life reductions caused by the lowest strain rate were more significant. Generally, inferior fatigue resistance was provided by the rotor bore material, particularly in the more heavily segregated zones of the intermediate pressure stage.
Application of the linear damage summation (LDS) rule to hold time data was not satisfactory. Better results were generally obtained by the strainrange partitioning (SRP) method, with a few unconservative life predictions mainly due to inclusions that dominated early failures. A life correlation was attempted by an energy-based criterion suitable to provide rationalization of creep and fatigue damage in terms of thermodynamic concepts.
Fracture Toughness of Thin-Walled Cylinders Fabricated from Discontinuous Silicon Carbide Whiskers/Aluminum Metal Matrix Composites
Authors: Raymond L , Jennings JA 
Published: February 2009

Six cylinders (16 cm diameter with 6 mm wall thickness) were manufactured from two unreinforced aluminum alloy and four silicon carbide (SiC) whisker reinforced aluminum composites. Curved, subthickness, Charpy sized specimens were used to measure the fracture toughness, KIc in accordance with ASTM E 399. For the more ductile, unreinforced alloys, the British crack opening displacement (COD) method was used as an elastic-plastic approximation of the fracture toughness. The results rank the relative toughness of the aluminum alloy metal matrix composite (MMC) materials.
The test program was successful in demonstrating the changes in fracture toughness due to the addition of SiC whiskers, notch acuity, and prior hydrostatic straining. A new procedure was developed by which materials can be successfully fatigue precracked (FPC) by utilizing the notched strength ratio in bending. This procedure eliminates the cost of the excessive waste commonly generated in attempting to fatigue precrack fracture toughness specimens by conventional techniques.
Influence of Heat Treatments and Working on Mechanical Properties of Silicon Carbide Reinforced Aluminum Alloys
Authors: Heritier J , Balladon P , Rambaud J , Chevet F , De Coquereaumont M 
Published: February 2009

Three grades of silicon carbide (SiC) reinforced aluminium alloys are studied: one grade fabricated by powder metallurgy and reinforced by ≈25% volume fraction (vf) SiC particulates; two grades produced by casting and reinforced by ≈15% vf SiC whiskers.
Their behavior during hot working is simulated using unloading and holding times during high temperature tension testing. The three grades are also worked by extrusion and forging and the defects appearing on the wrought pieces are observed.
Mechanical properties of the three grades are represented versus temperature in the as received state, in the annealed state and in some cases after forging and annealing.
Microstructure is observed and its influence on mechanical properties is discussed.
Lineaments: Significance, Criteria for Determination, and Varied Effects on Ground-Water Systems—A Case History in the Use of Remote Sensing
Authors: Peter KD , Kolm KE , Downey JS , Nichols TC 
Published: February 2009

Lineaments are present in western South Dakota as linear segments of trunk streams and tributaries, soil and vegetation tonal anomalies, and topographic or drainage offsets. Because there is evidence for paleotectonic activity associated with certain lineaments, they appear to represent surface expressions of major basement discontinuities. Crustal movements along these discontinuities affected depositional patterns intermittently throughout the past 600 million years. Accordingly, the permeability and thickness of aquifers and confining beds have been affected.
Potentiometric, hydrochemical, geothermal, and seismic anomalies found in at least two aquifers correlate with surface lineaments mapped by remote sensing techniques. The authors hypothesize that (1) the Madison aquifer of Mississippian age is more transmissive along the Cheyenne River lineament and (2) there is upward leakage through the confining layers from the Paleozoicage aquifers to the Lower-Cretaceous-age aquifers along parts of the Kimball Creek, Bad River, White River lineament, and Cheyenne River lineament.
Criteria for the Selection of Remote Data Telemetry Methods for Geotechnical Applications
Authors: Chedsey GL 
Published: February 2009

The field of geotechnical monitoring has just within the last decade entered the age of automatic and remote data telemetry. Civil engineers, especially geotechnical engineers, have just recently opened the door to allow communication lines, telephone modems, radio links, and satellites to convey monitoring data automatically from the field to the office. The initial projects involving instrumentation automation and data telemetry were used for either very remote areas or very large projects. However, monitoring data can now be automatically gathered at the site and transmitted to a central location easily, efficiently, and economically, for projects of any size.
This paper details the types of automation and data acquisition used by Geotechnical Engineering and Mining Services (GEMS) to monitor conventional geotechnical instruments; for example, pneumatic and vibrating wire piezometers, thermistors, stream and reservoir level sensors, and others. Instrument data acquisition systems are of paramount importance to monitoring systems because they must accurately monitor the instrument and store the data. Equipment details, including electronics, are addressed.
The paper compares the four types of data transmission: telephone, radio [both ultrahigh-frequency (UHF) and very-high-frequency (VHF)], communication line, and satellite. Guidelines for the use of each type of data telemetry are given, and the relative advantages and disadvantages of each method are explained. The focal point of the paper is a table that summarizes the following items for each of the four telemetry methods: (a) best application, for example, the optimum number and types of sensors; (b) transmission range/rate and times per day; (c) accessibility; (d) reliability; and (e) relative cost.
In addition, applications are shown in which multiple types of data transmission methods are applicable. Case histories of recent projects involving geotechnical instrument automation and data acquisition with data telemetry also are given.
The Use of Synthetic or Natural Seawater in Studies of the Corrosion of Copper Alloys
Authors: Castle JE , Chamberlain AHL , Garner B , Parvizi MS , Aladjem A 
Published: February 2009

The inorganic components of seawater are well known and easily simulated by mixtures of the appropriate salts. The adoption of such mixes has the advantage that the buffering ability of seawater is simulated to some extent but leaves open the question of the role of the organic component of seawater, which is not simulated in any of the normal recipes available. It is always open to the experimenter to avoid the problem of simulating seawater by carrying out the test exposures in the sea itself. However seawater has such a variability that any exposure site or time of year will be inadequate in some unknown regard.
This paper describes our experience in holding water in the laboratory and of work relating to the influence of organic natural products on the corrosion of Kunife 10 (alloy CA706, 10Ni1.5FeCu alloy). To attempt to create a “modus operandi” for waters containing organic species, it is essential to first envisage their possible actions, for example, chelating action, inhibition, stimulation of transport, a reduction in ionic activity in solution leading to a change in the Pourbaix diagram, modification of crystal habits, or the formation of weak boundary layers. These aspects will be discussed in the paper.
A detailed study of the micro-organisms, which develop in tanks containing seawater over the period of their use as a stock of test medium and of the concomitent changes in water chemistry, has been made and will be reported. A more direct method of examining the effect of the organic component is to remove it from the water in order that it may be added back to synthetic mixes or used to augment the seawater itself. A system, which permits the removal and retention of high molecular weight compounds, will be described.
It is concluded that the organic material may have less influence on the corrosion of the Kunife alloy than on some other systems but that the techniques established to deal with organic components of seawater have been successful. In particular an influence of organic molecules on the cathodic process at low oxygen levels has been demonstrated.
The Electrochemistry of Steel Corrosion in Concrete Compared to Its Response in Pore Solution
Authors: Dawson JL , Langford PE 
Published: February 2009

Corrosion control of steel reinforcement relies on the maintenance of the high alkalinity of the hydrated cement especially in the presence of chloride ions. The present paper also indicates the adverse effect that chloride contamination of the initial mix can have on the permeability of the matrix to oxygen diffusion.
Data obtained on steel specimens embedded in ordinary portland cement paste prepared with varying additions of sodium chloride are presented. Potentiodynamic polarization curves obtained after 400-days exposure in a controlled humidity environment are compared to curves from steel immersed in extracted pore solutions. Pore solution measurements are shown to provide analogous information to embedded steel samples on the anodic and passivation processes. However, pore solution experiments do not simulate the influence of the matrix in controlling diffusion and resistivity, which influence the long-term durability and macro-cell development.
Interlaminar Fracture Analysis of Composite Laminates Under Bending and Combined Bending and Extension
Authors: Armanios EA , Rehfield LW 
Published: February 2009

Interlaminar fracture or delamination is a primary damage mode in laminated composites. It is caused by high interlaminar stresses which are produced by local stress raisers such as holes, free edges, ply drops, and other defects and discontinuities which may be manufacturing related or service induced. Delaminations alter internal load paths and usually contribute to the ultimate failure of the structure.
The present work is concerned with the development of a simple analytical model which permits the rapidly varying interlaminar stresses and energy release rate to be estimated by elementary means. Extensive numerical computations are avoided, and the results are obtained in closed form. The model is applied to the edge delamination specimen subjected to uniform bending and combined bending and extension loadings. Interlaminar stresses, total energy release rate, and energy release rate components are estimated.
Residual Stress and Strength Loss in Filament-Wound Composites
Authors: Knight CE 
Published: February 2009

Filament-wound composites are fabricated using an initial stress in the filament strand called the “winding tension.” This initial stress will interact structurally with the winding form and each of the wound layers incrementally as the fabrication process proceeds. The interactions will result in a variable residual stress distribution or possibly in total tension loss in some of the wound layers. Total tension loss before cure of the resin matrix produces strength loss in the affected layers and the whole structure.
An incremental construction procedure has been implemented into a finite element computer program for analysis of the winding process. The method involves switching “on” element stiffnesses in the finite element model as construction proceeds. The initial stress in the element being switched on due to winding tension is converted to nodal loads and applied to the currently existing structure. If any layer loses all its initial stress, then its material stiffness is reduced (assuming the uncured composite cannot carry fiber direction compressive loads). The incremental addition of element stiffnesses and modification of material properties make the analysis incrementally nonlinear.
An analytical and experimental study was conducted on a series of cylinders. The parameters investigated include winding mandrels of aluminum or plastic, two uniform winding tension levels, and two final composite thicknesses all using a Kevlar/epoxy composite. Two aluminum mandrel thicknesses were used to vary the mandrel stiffness, with the plastic mandrel serving as a very low stiffness mandrel. Residual stress distributions were predicted for all the wound parts, and these were used to calculate the mandrel strain during construction which was compared with measured response of strain gages on the mandrel. Correlations were very good. Tension loss in the inner layers was seen in two cases; these were for the highest winding tension and largest final composite thickness wound on the thin aluminum mandrel and wound on the plastic mandrel.
The study shows results of modeling the fabrication process and the consequence of fabrication parameter choices. Situations were produced which show strength loss in Kevlar/epoxy composites. It is therefore necessary to include fabrication engineering as part of the design of filament-wound structures.
Local Area Networking in the Analytical Laboratory
Authors: Kunz FW , Cole GS 
Published: February 2009

The use of dedicated or shared computers or both for analytical instrument control, data accumulation, data reduction, and data reporting is now commonplace in most well-equipped laboratories. This paper details a local area network (LAN) concept for an analytical laboratory which improves the use of computers as well as reduces computing costs. Various instruments, including X-ray diffraction, X-ray fluorescence, electron microprobe, and surface spectroscopy equipment are connected to our LAN for file transfer and remote terminal logins.
There is also an increasing demand for filing data, monitoring quality assurance, and generating composite management reports accumulated from these various analytical instruments; this can be accomplished by accessing an electronic laboratory notebook system.
Efficacy Determinations of Rodenticide Use and Trapping for Reduction of Coconut Loss in the Philippines
Authors: Milan PP , Jackson WB 
Published: February 2009

Trapping and anticoagulant baiting to reduce rodent populations in coconut plantations—and consequently to reduce crop losses—were evaluated in Leyte (Central Philippines). Activity indices (trap success and tracking board utilization) were used to reference rodent populations (largely Rattus rattus mindanensis). Relative numbers of rodent-damaged, fallen coconuts were used to assess control efficacy.
Both anticoagulant baiting (ground, trunk, crown) and snap trapping (ground and crown) reduced numbers of rodents and fallen and damaged coconuts. Crown baiting was the most effective in reducing rat numbers and thus damage, and it also provided the most favorable cost/benefit ratio. Marking of rodents with metallic flakes contained in bait showed vertical movements in coconut trees as well as movements from croplands into coconut plantations at times of harvest and field preparation.
Prediction of Tube-Tubesheet Galvanic Corrosion Using Finite Element and Wagner Number Analyses
Authors: Scully JR , Hack HP 
Published: February 2009

Galvanic corrosion predictions for heat exchanger tube/tubesheet galvanic couples are presented and discussed. The predictions were performed using finite element analysis using two programs, WECAN and MARC, and by Wagner number analysis under conditions of secondary and tertiary current distribution. Long-term electrochemical potentiostatic polarization data generated over 120 days in natural seawater were used to account for time effects. Results of the predictions are presented in the form of potential and galvanic current density as a function of distance from the tubesheet along the tube axis.
Seawater exposures of some tube/tubesheet material combinations were performed to compare with the predictions. These exposures used segmented tubes connected in series through the use of zero resistance ammeters. Material combinations exposed included a Monel Alloy 400 tubesheet coupled to a 90-10 copper-nickel tube, a 90-10 copper-nickel tube coupled to a zinc anode at the position of the tubesheet, and a nickel-aluminum-bronze tubesheet coupled to an Alloy 625 tube. Tube/tubesheet data obtained from the literature were also compared to predictions.
This study is directed towards determining not only the degree of accuracy of the predictions from the finite element and Wagner number analysis techniques, but also the sensitivity of the analyses to small changes in the electrochemical data used to obtain the predictions. The feasibility of these two analysis techniques for accurate qualitative as well as quantitative galvanic corrosion prediction for the tube/tubesheet configuration is discussed.
Integration of Galvanic Corrosion Control Technology into Design
Authors: Jenkins JF 
Published: February 2009

Corrosion and design are synergistic. Design affects the type and amount of corrosion that is likely to occur, and corrosion affects the functionality of a given design. As galvanic corrosion can result in rapid localized attack, its effects are often severe.
The general relationship between open circuit potential, polarization, electrolyte resistivity, area ratio, and galvanic corrosion is well understood by corrosion engineers but is often not considered during design. Control of galvanic corrosion is most often accomplished by identifying probable sites for galvanic attack and either eliminating the possibility of galvanic corrosion through elimination of the dissimilar metals or by other means.
Where atmospheric exposure is encountered, mitigation of galvanic effects can be accomplished by eliminating design features that trap and hold moisture, the use of sealants, or the use of welded versus bolted joints. The selection of fastener materials must also consider galvanic compatibility.
In applications where the surfaces subject to galvanic attack are submerged, electrical isolation of dissimilar metals, control of the relative anodic and cathodic areas, the use of protective coatings, and the application of cathodic protection should be considered.
The technology to control galvanic corrosion is well known to corrosion engineers but is often not considered during the design process. It is the responsibility of corrosion engineers to insure that corrosion control technology is incorporated into the design process. This may be achieved either by education of design engineers regarding galvanic corrosion or by the inclusion of a corrosion engineer in the design team.