bluuebunny/crossref_metadata_2025 huggingface dataset:
Oily Bilge Water Treatment With a Tubular Ultrafiltration System
Authors: Harris L. R. , Jackson D. F. , Schatzberg P.
Published: November 2010

In its concern for maintaining and enhancing the environmental quality of water bodies, the Navy has been developing various oil pollution abatement systems. One potential process for the separation of oil in bilge water is ultrafiltration, a pressure-driven membrane process which can separate, concentrate, and fractionate macromolecular solutes and suspended species from water. A tubular ultrafiltration system using cellulosic and noncellulosic membranes was tested with bilge oil obtained from a patrol craft. Tests were also conducted with tap water, river water, a turbine lubricating oil, and a fuel oil, alone and in combination with a nonionic detergent. The addition of the detergent was observed to result in a steeper flux decline than when any of the fluids were evaluated alone. Both membrane types produced a permeate with an oil content generally less than 15 mg/l. Although the noncellulosic membranes exhibited higher flux rates than the cellulosic membranes, only the former could be restored by a cleaning operation to its initial water flux after experiencing a decline in flux. A cumulative irreversible flux decline was exhibited by the cellulosic membrane. Cleaning operations, some of which were time-consuming, consisted of flushing the membrane with ultrafiltrate, distilled water, tap water, or the manufacturer’s enzyme-detergent formulation. Only the last of these, when employed at elevated temperature (125°F), restored the initial water flux of the noncellulosic membrane.
On the Criteria for the Rotatability of the Cranks of a Skew Four-Bar Linkage
Authors: Freudenstein F. , Primrose E. J. F.
Published: November 2010

Based on an extension of an earlier investigation [1], an algebraic treatment is given of the conditions governing the existence of crank-and-rocker type skew four-bar linkages.
Synthesis of Function Generating Spatial Mechanisms With Optimum Structural Error
Authors: Osman M. O. M. , Dukkipati R. V.
Published: November 2010

The design of a spatial four-link RSSR mechanism for function generation with optimal structural error is examined. Analytical equations relating the design parameters are obtained by forcing the extreme errors in between accuracy points to be equal in magnitude by imposing the necessary constraints. The procedure for computing the linkage parameters in a function generation synthesis of an RSSR mechanism with optimal structural error is illustrated with a numerical example. This method provides an effective approach to the synthesis of spatial mechanisms for function generation with optimal structural error and represents a useful addition to the methods at the discretion of engineers in the design of spatial mechanisms.
Numerical Solution of a Deep-Drawing Problem
Authors: Odell E. I. , Clausen W. E.
Published: November 2010

A rigid-plastic analysis of the axisymmetric deep-drawing problem is made using a special numerical technique. The effects of work-hardening, friction, and normal anisotropy have been included. Incremental strain theory is used to obtain results for both bending and membrane shell theories. These results are then compared. The authors feel that membrane theory gives very good results and should be used in the future to analyze any relatively thin cups.
Design of a Fiber Optic Pressure Transducer
Authors: Pahler R. H. , Roberts A. S.
Published: November 2010

Performance characteristics of a fiber optic pressure transducer are presented and discussed. The transducer consists of a cylindrical metal housing with a specular reflecting aluminum diaphragm at the distal end and a circular array of fiber optic light guide bundles at the proximal end. The center bundle is connected to a light source with the surrounding bundles carrying reflected light to a photodetector. A change in pressure on the diaphragm produces a differential change in light intensity. An analytic procedure guides the selection of an optimal configuration in order to obtain maximum transducer response.
Fracture and Wear as Factors Affecting Stochastic Tool-Life Models and Machining Economics
Authors: Rossetto S. , Levi R.
Published: November 2010

Under production conditions cutting tools often fail under several failure modes, the occurrence of a single one only for a given operation being rather exceptional. In light of this observation a stochastic model is developed, considering as causes of tool failure both wear and fracture processes. Machining economics are then analyzed with a probabilistic approach, deriving distribution functions of profit rate.
Design of Four-Bar Function Generators With Mini-Max Transmission Angle
Authors: Gupta K. C.
Published: November 2010

A new method of designing four-bar function generators with optimum transmission angle is presented. Transmission angles are considered optimum, in a mini-max sense, when their extreme values deviate equally from 90 deg. Numerical examples are given to illustrate the synthesis procedure.
On One Analysis of Axisymmetric Extrusion by the Use of Flow Lines
Authors: Ishikawa Hiromasa , Hata Kin-Ichi , Goto Masayoshi
Published: November 2010

On the assumption that the flow lines of material might be approximated by the function of hyperbolic tangent an analytical method to examine the mechanics of material during forward extrusion is presented in this paper. For the application of this method to actual extrusion, the unknown quantity is readily determined with the use of material constant obtained through the compression test. Therefore, the mechanics of material during forward extrusion can be obtained approximately without a preliminary extrusion test.
Synthesis of a Six-Link Spatial Mechanism via Screw Triangle Geometry, Successive Screw Displacements, and Pair Geometry Constraints
Authors: Kohli D. , Soni A. H.
Published: November 2010

Using the theory of screw triangle geometry, successive screw displacement, and pair geometry constraints, a generalized synthesis procedure is proposed and demonstrated to synthesize for a variety of motion programs all possible six-link, two-loop spatial mechanisms with lower kinematic pairs. The mathematical procedure developed in this paper is illustrated by presenting two numerical examples. It is shown that the screw triangle circuit is the most fundamental element that permits us to derive synthesis equations for any type of synthesis problem.
Fluid Delivery and Metering for Reaction-Injection Molding
Authors: Tucker C. L. , Suh N. P.
Published: November 2010

Power consumption and metering accuracy of reaction-injection-molding (RIM) fluid-delivery systems are examined. Emphasis is on the use of simple models to understand the source of metering errors and to estimate the magnitudes of these errors. Typical examples are given. The basic understanding provided by these models is used to explain the advantages of a new type of RIM fluid-delivery system developed at M.I.T. The new system offers reduced machine size and cost by minimizing instantaneous power requirements, and the metering system can achieve higher accuracy than conventional equipment while using less-accurate components.
The Thermodynamic Performance of Oil-Flooded Helium Screw Compressors
Authors: Toscano W. M. , Hoagland L. C.
Published: November 2010

In recent years the cryogenic community has become interested in the application of hermetic screw compressors for helium refrigeration/liquefaction systems. In the past the screw compressor had not been an attractive compressor for cryogenic systems because of the problems associated with both dry and oil-flooded screw compressors. However, oil separation technology has evolved to a point where oil can successfully be separated from helium gas. The screw compressor has exhibited excellent reliability and performance characteristics for various refrigeration gases, and preliminary test results reveal that the same is true for helium gas. The present paper presents the thermodynamic performace characteristics of 30-kW (40-HP) and 113-kW (150-HP) oil-flooded hermetic screw compressors with various built-in volume ratios operating with helium gas at pressure ratios between 2.0 and 18.0, and for suction pressures of 0.5 atm, 1.0 atm, and 2.0 atm. The thermodynamic parameters of interest are the volumetric efficiency and the isentropic efficiency. It is found that the volumetric efficiency decreases with pressure ratio; however, depending on the built-in volume ratio of the compressor, the maximum value of the isentropic efficiency occurs in a narrow range of values for the pressure ratio at which the optimum isentropic efficiency occurs. The results of the tests indicate that oil-flooded screw compressors may successfully be used for helium service.
Hysteresis Test on Bolts
Authors: Fazekas G. A. , Griffin J. P.
Published: November 2010

Using only a torque wrench to measure tightening and break-away release torque, bolt pull and friction can be determined in situ. This allows both a check on and a setting of the required bolt preload.
Measurements of Mean and Fluctuating Temperature in a Turbulent Spray Flame
Authors: Khalil E. E.
Published: November 2010

Measured values of gas temperature and its fluctuations are reported for six different flow conditions of kerosene spray flames issuing into free surroundings. Beside assessing the feasability of measuring mean and fluctuating temperature in turbulent flames, the paper is concerned with investigating effects of the fuel injection pressure and secondary atomization on the structure of the flame. The measurements were obtained using thin thermocouple wires, and corrections for conduction, radiation and time-lag effects were included.
Chipping and Breakage of Carbide Tools
Authors: Tlusty J. , Masood Z.
Published: November 2010

The paper deals with chipping and breakage of carbide tools and it is based on a combination of turning tests, examination of fracture surfaces, and analysis of stresses in the tool as produced by the cutting force. Thermal stresses are so far not considered. It is concluded that chipping is a ductile failure due to high shear stresses at the cutting edge and breakage is brittle fracture originating at the rake face at a local maximum of tensile stress. For the finite element stress analysis, a new method of successively refining mesh while diminishing the analyzed area is introduced which is rather effective and economical in that all computation except for the final field is done once only for various loading cases.
Rotary Car Dumper Systems
Authors: Sabina W. E.
Published: November 2010

This paper, in general, discusses the technically important points in total planning of rotary car dumper systems. Total systems installations include, aside from terrain and trackage, such items as car retarders, electronic weigh scale platens, the many combinations of dumpers, car ejectors, train positioners and hammermills. Pollution control and OSHA safety provisions are also discussed. The paper will also explain technological details of design which promotes smoothly operating systems.
Multi-Tool Machining Analysis—Part 1: Tool Failure Patterns and Implications
Authors: Zompi A. , Levi R. , Ravignani G. L.
Published: November 2010

In some machining operations tools may fail suddenly in a catastrophic way. Multi-tool setups, where several tools are engaged simultaneously and a single tool failure may impair the whole operation, are particularly sensitive to such a failure mode. Selection of tool replacement strategy may then become a major problem, whose solution is often hampered by scarcity of data. Sometimes no optimal strategy may exist, and little can be done acting on tool replacement only to improve the situation. However, given a minimum amount of information, simple simulation methods help to assess effectively alternative policies.
Die Temperatures During Production Drop Forging
Authors: Dean T. A. , Silva T. M.
Published: November 2010

This paper describes a cavity forging die set fitted with thermocouples for measuring both surface and sub-surface temperatures. Measurements at the surfaces show how the temperature transients are influenced basically by flow of forging stock. Maximum values of surface temperatures are shown to vary over the surface of the cavity and are affected by the type of machine used. Sub-surface temperatures are found to be primarily dependent on the length of time the forging stock is in intimate contact with the die and relatively insensitive to the type of forging machine used.
Plastic Instability of Thin Shells Deformed by Rigid Punches and by Hydraulic Pressure
Authors: Kaftanog˘lu Bilgin
Published: November 2010

A theory has been developed to provide a solution for axisymmetrical shells in the plastic range for large deformations up to fracture. It includes the effects of strain history, nonlinear strain-hardening characteristics of materials, plastic anisotropy in the thickness direction, prestrain, through-thickness stress, and boundary tractions. It is also possible to use nonuniform initial conditions such as varying thickness and varying prestrain. A numerical solution has been developed especially suitable for stretch forming by a rigid punch and for hydraulic bulging of shells or diaphragms. It can easily be modified for the deep-drawing problem. Different instability criteria have been studied. It was found that the conventional criteria would not yield satisfactory results. A new criterion called the “strain propagation” criterion gave satisfactory results in the prediction of the onset of fracture. It could expalin the fracture taking place at increasing or decreasing pressures in the hydraulic bulging problem.
A Phenomenological Theory of Aging Effects of Metals
Authors: Stouffer D. C. , Strauss A. M.
Published: November 2010

A constitutive law is developed for metals which have aging properties. The development of this law is based on the assumption that the mechanical properties of simple aging materials can be mathematically represented by a functional of the strain history, and that this functional depends upon the age of the material. A perturbation technique allows the separation of the nonaging response from the aging effects, and leads to convenient representations for viscoelasticity and plasticity. The mechanical behavior of aging metals is studied by applying the arc length parameterization of the strain history. The final rate independent results are transformed to the time domain for efficient use in engineering applications and in solving boundary value problems.
A Study of the Effects of Prestrain on the Tensile Properties of Filamentary Composites
Authors: Fedor R. J. , Ebert L. J.
Published: November 2010

A study of the effect of mechanical prestraining on the tensile behavior of metal matrix composites was conducted. Using both a two-member cylindrical composite simulation model and actual filamentary composites, the stress and strain distribution was followed during cool-down from the compositing temperature, through the prestrain cycle, and during subsequent reloading. The prediction of the behavior of the model composites during unloading from the prestrained state was found to be complicated by compressive plastic flow of the matrix during the unloading. By using experimentally measured effective stress-effective strain curves, the Bauschinger effect exhibited by model composites was well described. The model composites used to validate the analysis consisted of maraging steel—OFHC copper concentric cylinders. Prestraining of copper-tungsten filamentary composites was investigated both experimentally and analytically to verify the applicability of the model to real fiber composites. It was established that prestrain into the elastic-plastic behavioral region was successful in increasing the load-carrying capacity of composites with a 20 percent volume fraction of tungsten. The analytical technique used to describe the behavior of the cylindrical composites was used to rationalize the behavior of the filamentary composites. It was shown that the ameliorating effect of prestraining was due to the alteration of the net residual stress state of the matrix from an “as fabricated” tensile state to one of compression after prestraining.
The Plastic Bending of Beams and Their Failure by Low Cycle Fatigue
Authors: Das P. K. , Chandler D. C. , Foster B. K.
Published: November 2010

The major difficulty in applying high strain fatigue data to technological problems lies not in the fatigue aspect per se but in the prediction of the cyclic strain amplitudes. In this paper they are postulated for the cyclic bending of beams using large deflection theory and taking into account the changing stress-strain relationships which occur as cycling progresses. These theories have been tested using beams of rectangular cross section made of three different materials: mild steel, stainless steel, and an aluminum alloy. Good correlation has verified their applicability.
Finite Element Analysis of the Diametral Test of Polymer Moldings
Authors: Price H. L. , Murray K. H.
Published: November 2010

A finite element analysis of the diametral test is presented and the results are compared with an elastic analysis and with diametral tests of molded pyrrone disks. Both the elastic and the finite element analysis gave similar stresses for points near the center of the disk. Near the points of loading, however, the elastic analysis gave infinitely high stresses whereas the finite element analysis gave high but finite stresses. A simulated fracture was made using the finite element analysis. The fracture began at the center of the disk and propagated toward the loading points. As the fracture approached the loading points, the finite element analysis indicated the formation of four secondary fracture sites in the disk. These sites were a normal development for a soft loading system. The existence and location of the secondary fracture sites was confirmed by diametral tests of molded pyrrone disks.
The Effect of Slow-Constant Strain Rates on the Tensile Properties of Selected Alloys at Room and Elevated Temperatures
Authors: Dotson C. L.
Published: November 2010

Tensile tests were performed at constant strain rates from 10−2 to 10−5 min−1 on 5454-O and 1100-O aluminum alloys, A515 Grade 70 steel and B166 nickel alloy at room temperature and at elevated-temperature ranges where the design stress basis normally changes from tensile to creep-rupture controlled. The results in general showed that the strength of the alloys decreased at lower strain rates, and the sensitivity to strain rate was greater at elevated temperatures except where metallurgical phenomena such as dynamic strain aging negate the effects of strain rate. At the highest temperature the decrease in strength properties ranged from 11 to 50 percent over the strain rate range for different alloys.
Effect of Strain-Hardening Exponent and Strain Concentrations on the Bursting Behavior of Pressure Vessels
Authors: Royer C. P. , Rolfe S. T.
Published: November 2010

Studies by the Subcommittee for Effective Utilization of Yield Strength of the Pressure Vessel Research Committee of the Welding Research Council have provided a better understanding of the behavior of pressure vessels in the bursting mode of failure. Specifically, these studies have shown that high-strength steels can be more effectively utilized in pressure vessel applications, and with appropriate safety. However, before specific Code changes are recommended, the possible influence of undetected sharp flaws on the burst pressure, as predicted by the modified Svensson equation, should be established. Accordingly, a study of six notched pressure vessels was conducted to establish the limitations of the Svensson equation with respect to severe strain concentrations, namely, sharp longitudinal notches. Three steels (A517, A516, and 304SS) having a wide range of strain-hardening exponents (0.09, 0.19, and 0.59) were used to fabricate thin-walled pressure vessels (16-in. (406 mm) O.D., 1/2 in. (13 mm) wall thickness, 48-in. (1.22 m) length). Each vessel had a 15-in. (381 mm) long sharp machined notch with flaw depths ranging from 15 to 35 percent of the wall thickness. These vessels were tested hydrostatically to burst at room temperature. All failures were ductile. The results indicate that for pressure vessel steels having nominal yield strength up to 115 ksi (793 MN/m2) and normal ductility and toughness, the modified Svensson equation can be used to predict burst pressure very reliably as long as the flaw depths are less than 25 percent of the wall thickness. On the basis of these test results, as well as burst tests of vessels with moderate strain concentrations such as nozzles and flat end closures, it is recommended that the terms Fcyl and Fsph (factors that describe the effect of strain-hardening exponent on the bursting behavior of cylinders and spheres) be incorporated into the appropriate Code provisions. It is further recommended that the appropriate Code committee consider a possible reduction in the factor of safety against bursting on the basis of the results of this investigation.
Model Experiments for Thermal Shock Fracture Behavior
Authors: Blauel J. G. , Kalthoff J. F. , Stahn D.
Published: November 2010

Thermal shock fracture tests with specimens of simple geometry (plate and hollow cylinder) made from an appropriate model material, glass, were performed to investigate the behavior of cracks under transient thermal loads. The experimental results are compared to theoretical/numerical calculations based on a linear elastic analysis. The fracture mechanics approach used for safety evaluations, for instance in case of emergency core cooling in a reactor plant, is further substantiated.
Formation of Cavities From Nondeformable Second-Phase Particles in Low Temperature Ductile Fracture
Authors: Argon A. S.
Published: November 2010

Limiting solutions are discussed for elastic-plastic deformation around rigid particles of both equiaxed and greatly elongated shapes. It is shown that if the matrix can be characterized as a rigid nonhardening continuum the stress concentration at the particle interface and interior is less than two for either equiaxed or elongated particles. In a rapidly strain hardening matrix, however, while the interfacial stress concentration relative to the distant boundary traction remains at a factor of two for the equiaxed particles, it rises nearly linearly with aspect ratio for slender platelets and rods. Interaction between particles can occur when the local volume fraction of particles is high. Such interactions raise the interface tractions for a given state of shear of the matrix and hasten void formation, and are often discerned as a particle size effect. Another particle size effect based on flawed particles is also discussed.
Computer Simulation of Plastic Deformation Through Planar Glide in an Idealized Crystal
Authors: Altintas S. , Hanson K. , Morris J. W.
Published: November 2010

In this paper we report the behavior of the plastic deformation of an idealized crystal made by stacking parallel slip planes. Each slip plane is assumed to contain active sources of dislocations leading to a constant density of non-interacting dislocations in the plane which glide through randomly distributed localized point obstacles, representing small precipitates. The dislocation is assumed to have a constant line tension and the dislocation-obstacle interaction is taken to have a simple step form. Using results of computer simulation of thermally activated glide through random arrays of point obstacles we modeled deformation as a function of temperature and applied stress, determining the strain rate and the morphological characteristics of slip.
Stresses at the Surface of a Flat Three-Dimensional Ellipsoidal Cavity
Authors: Mirandy L. , Paul B.
Published: November 2010

The stress field associated with a thin ellipsoidal cavity in an isotropic elastic medium with arbitrary tractions at distant boundaries is needed to generalize Griffith’s two-dimensional fracture criterion. Such a solution is given here. It is first formulated for a general ellipsoidal cavity having principal semiaxes a, b, and c, and then it is reduced to the specific case of a “flat” ellipsoid for which a and b are very much greater than c. An explicit solution of the general problem is possible but the results are somewhat unwieldy. The dominant terms of an asymptotic solution for small c/b, however, are shown to provide remarkably simple expressions for the stresses everywhere on the surface of the cavity. The applied normal stress parallel to the c axis and the shears lying in a plane perpendicular to it were found to produce surface stresses proportional to (b/c) × applied stress, with the amplification of other components of applied stress being negligible in comparison. Analytical expressions for the location and magnitude of the maximum surface stress are developed along with stress intensity factors for the elliptical crack (c = 0). Three dimensional effects due to ellipsoidal planform aspect ratio (b/a) and Poisson’s ratio are reported.
Creep Testing at Variable Temperature and Load, Experimental and Computational Methods
Authors: Smith E. M.
Published: November 2010

Design of engineering components for reliable service in conditions where severe load and thermal transients are encountered requires special care. The individual nature of each such application can easily place it out with existing codes of practice. For safe life design in such cases, general analytical techniques involving numerical computation may have to be applied. This paper describes opening stages in one approach to determination of constitutive equations essential to such computations.
Thermal Ratcheting of a Beam Element Having an Idealized Bauschinger Effect
Authors: Mulcahy T. M.
Published: November 2010

Thermal ratcheting has been analytically investigated for a beam element subjected to a linear temperature variation across its solid rectangular cross section. A linear strain-hardening material response exhibiting an idealized Bauschinger effect was assumed. Formulas are given for the associated strain accumulation which are valid over a large range of strain hardening, temperature variation, temperature cycles, and axial load. Specific results are tabulated for the materials and operating conditions typically associated with liquid metal breeder reactors.
Fully Plastic Solutions and Large Scale Yielding Estimates for Plane Stress Crack Problems
Authors: Shih C. F. , Hutchinson J. W.
Published: November 2010

Fully plastic plane stress solutions are given for a center-cracked strip in tension and an edge-cracked strip in pure bending. In the fully plastic formulation the material is characterized by a pure power hardening stress-strain relation which reduces at one limit to linear elasticity and at the other to rigid/perfect plasticity. Simple formulas are given for estimating the J-integral, the load-point displacement and the crack opening displacement in terms of the applied load for strain hardening materials characterized by the Ramberg-Osgood stress-strain relation in tension. The formulas make use of the linear elastic solution and the fully plastic solution to interpolate over the entire range of small and large scale yielding. The accuracy of the formulas is assessed using finite element calculations for some specific configurations.
Mechanism of Underclad Cracking—Combined Effects of Residual Strain and Heat-Affected Zone Ductility
Authors: Kume R. , Okabayashi H. , Amano M.
Published: November 2010

The mechanism of heat-affected zone cracking under weld overlay cladding has been investigated for four kinds of ferritic steel overlay-welded with austenitic stainless steel. Cracking occurs during postweld heat treatment because the ductility of the heat affected zone is insufficient to relieve internal stress. This low ductility is caused by the combined effects of fine carbide precipitate and coarse-grained structure. High internal stresses at postweld heat treating are due to the combined effects of residual stress as well as thermal stress resulting from the difference in thermal expansion coefficients of base metal and cladding material. Means for preventing cracking during fabrication are described, based on this cracking mechanism.
Failure Analysis of an Adhesively Bonded Graphite Composite/Steel Scarf Joint
Authors: Macander A. B. , Mulville D. R.
Published: November 2010

Recent studies on the use of graphite fiber-organic matrix composites in Naval and commercial high performance ships have demonstrated the potential for significant weight savings and corresponding improvements in ship performance. Unlike conventional materials, structural elements fabricated with advanced composite materials require specialized attention. One area that is critical to the successful development of reliable composite structural elements is joining. This paper describes a method for determining the structural integrity of an adhesively bonded composite/steel scarf joint. An experimentally established failure criterion is presented based on a strain energy release rate formulation, which may be used to predict performance of the scarf joint under tensile loading.
Elastic-Plastic R-Curves
Authors: McCabe D. E. , Landes J. D.
Published: November 2010

The principal purpose of this investigation was to study specimen size effects on elastic-plastic type R-curve using HY130 steel plate. Compact specimens ranging in size from 12T to 1T in planar dimensions and standardized on 1-inch thickness were used. Using an elastic-plastic concept developed in a companion program, it was shown that the R-curve is specimen size independent, even when nominal stress was well beyond general yield and the crack was propagating beyond maximum load. Using this observation, it is shown how instability can ge predicted under conditions ranging from elastic-plastic to fully plastic. This establishes the ground work for future studies on how R-curve is affected by specimen type or by stress triaxiality conditions.
A Dynamic Optical Correlation Technique For Fatigue Failure Prediction
Authors: Haworth W. L. , Cheng T. , Hieber A. F. , Yu F. T. S. , Mueller R. K.
Published: November 2010

A continuous optical correlation technique for fatigue damage detection and fatigue failure prediction in metals is described. Information about the metal surface is recorded on a thermoplastic-photoconductor device and compared with the actual surface as the fatigue test proceeds. Results are presented as plots of optical correlation intensity (CI) versus number of fatigue cycles (N) for aluminum 2024-T3 sheet. A decelerating loss of log CI versus N is observed over about the first 30 percent of fatigue life, a linear loss from 30 to 80 percent approximately, and an accelerating loss over the final 20 percent of life. The correlation intensity curve provides a sensitive indication of fatigue damage occurring in the specimen, and can be used to monitor crack formation and to predict impending failure.
Fatigue Damage Detection in 2024-T3 Aluminum, Titanium, and Low Carbon Steel by Optical Correlation
Authors: Haworth W. L. , Singh V. K. , Mueller R. K.
Published: November 2010

Optical correlation techniques were used to monitor fatigue damage in three metals of different strength and ductility, namely 2024-T3 aluminum alloy, commercial purity titanium, and low carbon steel. Topographical information from the specimen surface is stored holographically and compared with the actual surface as the fatigue test proceeds. Results are presented as curves of correlation intensity (CI) versus number of fatigue cycles, and data are compared for unnotched aluminum sheet specimens and notched specimens of all three materials. CI curves from both notched and unnotched 2024-T3 specimens show the same general three-stage form, and the onset of the third stage corresponds to the presence of a growing fatigue crack. The overall loss of CI over the effective life of the specimen, however, is lower for notched specimens, where fatigue damage is limited to a relatively small area of the illuminated surface. CI curves from titanium and steel specimens also develop in three stages, but for steel the initial region of the curve is protracted and the overall loss in CI is relatively large. This behavior occurs because the steel is relatively ductile and consequently the fatigue damage develops over a large fraction of the illuminated surface. Finally, the effect of the initial surface finish on the CI curve is discussed for all three materials.
Review of the Mechanical Properties of Cast Steels With Emphasis on Fatigue Behavior and the Influence of Microdiscontinuities
Authors: Mitchell M. R.
Published: November 2010

Mechanical properties of cast steels are pronouncedly affected by the microdiscontinuities which they inherently contain. In particular, fatigue behavior of cast steels is altered by (1) the size, (2) the shape, and (3) the distribution of microdiscontinuities as well as (4) the strength and ductility of the matrix metal. A review is made of the literature in order to demonstrate the necessity of accounting for all of these variables and a technique for predicting the fatigue behavior of cast steels is presented.
Representation of Elevated-Temperature Tensile Behavior of Type 304 Stainless Steel in a Sodium Environment
Authors: Chopra O. K. , Natesan K.
Published: November 2010

An analysis of tensile behavior of Type 304 stainless steel was conducted for specimens in the solution-annealed condition and after exposure to a sodium environment. The Voce equation was used to describe tensile flow curves for plastic strains above 0.005 at temperatures between 550 and 700°C and strain rates of 3.81 × 10−6 to 1.90 × 10−3 s−1. The results show that, when compared with solution-annealed specimens, the tensile flow behavior of the sodium-exposed specimens is characterized by a higher strain-hardening rate, which decreases rapidly with an increase in flow stress. The values of the saturation stress for uniform elongation predicted from the Voce model are higher for the sodium-exposed specimens than for those in the solution-annealed condition at strain rates ≲5 × 10−5 s−1 and lower for strain rates ≳5 × 10−5 s−1. Metallographic examination of the fracture surfaces shows a transition from a complete ductile fracture to a partial intergranular failure as the strain rate decreases. Carburization of the specimens appears to inhibit the intergranular failure.
Design of Condenser Cooling Water System for a Nuclear Power Plant Located on a Large Estuary
Authors: Jeffers F. J. , Geyer J. C. , Neale L. C.
Published: November 2010

A coordinated program is described for developing information needed for designing a condenser cooling water system for a nuclear power plant located on a large estuary to meet State water quality standards and minimize any adverse effects on aquatic life. The paper discusses estuarine conditions pertinent to the design of the intake and discharge structures, the heat assimilative capacity of the estuary, application of the momentum jet theory to the condenser cooling water discharges, and hydraulic model investigations to determine mixing and dispersion patterns.
Optimization of Solar Terrestrial Power Production Using Heat Engines
Authors: Selc¸uk M. K. , Ward G. T.
Published: November 2010

Mathematical model and computer programs have been developed for the analysis of the economic performance of a terrestrial solar power system using heat engines. Various combinations of cycle, collector, engine, storage system, and sink have been studied and the influence of design parameters on power costs examined for both the steady and unsteady state cases. Typical minimum power costs under central Australian conditions for units of 12 kw capacity at current levels of materials and labor costs range from 7 to 47 U. S. cents per kwh, according to the specific design of installation.
Boundary Layer Optimization for the Design of High Turning Axial Flow Compressor Blades
Authors: Papailiou K. D.
Published: November 2010

An optimization method, based on Le Foll’s boundary layer theory and on Goldstein’s conformal mapping method is described. The parameters of optimization are circulation per blade and absolute losses. The problem is treated as an inverse problem (i.e., the best blading is found starting from the flow conditions imposed). The performance of a highly loaded compressor cascade, designed according to the method presented and tested in a low speed wind tunnel, is compared with the theoretical predictions. Some discrepancies exist which are due to the influence of flow convergence and blade curvature. A modification of the method to take into account these effects is discussed.
Design and Performance Evaluation of Four Transonic Compressor Rotors
Authors: Gostelow J. P.
Published: November 2010

A set of four compressor rotors was designed as a means of optimizing blade camberline shape in the high-transonic Mach number region. One blade row was designed for a tip diffusion factor of 0.35 with the supersonic camber minimized. The other three blade rows were designed for a tip diffusion factor of 0.45 with tip ratios of supersonic to total camber varying from zero to the value corresponding to a double-circular-arc blade section. Performance maps and blade element data were generated as a result of testing on the four rotors. All rotors exceeded design efficiency and flow at conditions corresponding to design point operation. Operating range, from peak efficiency to stall, is highest in rotors designed for a low tip diffusion factor and which have the minimum amount of supersonic camber.
Tailpipe Effects on Gas Turbine Diffuser Performance With Fully Developed Inlet Conditions
Authors: Kelnhofer William J. , Derick Charles T.
Published: November 2010

Straight-walled diffuser-tailpipe systems with fully developed inlet conditions as encountered with gas turbine exhaust ducting systems have been tested. For constant length diffusers with varying tailpipe lengths, an increase in recovery and a slight increase in area ratio occurs at maximum performance condition. Test conditions included ratios of diffuser wall length to diffuser inlet width from 5.33 to 15.33. Maximum ratio of tailpipe length to diffuser inlet width was 10.47.
Thermal Cycle Arrangements for Power Plants Employing Dry Cooling Towers
Authors: Leung Paul , Moore R. E.
Published: November 2010

The use of dry cooling towers with air as the cooling medium will become more prevalent in the not-too-distant future as water quantities available for consumption in evaporative cooling processes for steam-electric generating plants become limited. Special considerations for designing either fossil-fueled or nuclear-fueled plants are required due to significant differences in turbine exhaust pressures which result in sizable capability losses. Those design considerations affecting turbine thermal cycles for steam-electric generating plants employing dry cooling towers are discussed in this paper. Effects on major plant components, such as turbine exhaust end sizes, cycle parameters and steam conditions, and the extent of feedwater heating within the regenerative cycle are discussed. Plant siting constraint considerations and general economic appraisals of fossil-fueled and nuclear-fueled cycles are summarized.
Shock Wave Behavior in Transonic Compressor Noise Generation
Authors: Fink M. R.
Published: November 2010

Compressor noise at transonic tip speeds contains strong tones at multiples of shaft rotation frequency as well as harmonics of blade passage frequency. These multiple pure tones or combination tones are caused by rotor blade nonuniformities which result in pronounced irregularities in the shock pattern attached to the rotor. Nonlinear first-order theory, similar to that used in analysis of sonic boom strength, is utilized to determine shock wave decay with upstream distance. In the extreme near field of the rotor, shock strength varies inversely as the square root of upstream distance from the blade leading edge, as with an isolated airfoil. Somewhat further upstream, the expansion region from the neighboring blade in the cascade interacts with the shock so that shock strength varies as the inverse first power of distance. These aerodynamic results are used to infer some characteristics of transonic compressor noise which in turn are compared with experimental results.
Fireside Corrosion and Pollutant Emission from Crude Oil Combustion
Authors: Lee G. K. , Mitchell E. R. , Friedrich F. D. , Draper R. G.
Published: November 2010

A pilot-scale research boiler was used to evaluate the corrosion and pollution potential of a western Canadian mixed-blend crude oil from the Interprovincial Pipeline. It was demonstrated that this crude oil, even when deliberately contaminated with high levels of salt, can be burned successfully with moderately low excess air. In addition, problems associated with low-temperature deposits, low-temperature corrosion, and pollutant emissions were minimal. High-temperature corrosion, due to either oil ash or gas-phase oxidation, can be controlled by proper selection of boiler tube material. Low-temperature pump and screen tests on the as-received crude oil indicated that no pumping or screen-plugging problems should occur at temperatures above the maximum pour point.
The Use of Cascade Technology in Centrifugal Compressor Vaned Diffuser Design
Authors: Pampreen R. C.
Published: November 2010

This paper highlights some results from experience with use of cascade technology in the design of diffusers for centrifugal compressors. The designs consisted of conformally transformed tandem blade-rows using 65-Series and double-circular-arc vane sections. Performance results are presented and comparisons to conventional diffuser data are made.
The Effect of Interaction Between Wakes From Blade Rows in an Axial Flow Compressor on the Noise Generated by Blade Interaction
Authors: Walker G. J. , Oliver A. R.
Published: November 2010

The effect of interaction between the wakes from one row of blades and the boundary layers and wakes of the next row of blades downstream has been measured in an axial flow compressor by hot wire signals displayed on a CRO screen synchronized with the rotor. It is shown that the two sets of wakes can be made to mutually cancel the greater part of the velocity defect in each at certain points. Proper choice of axial and circumferential position of alternate rows of stationary blades so that the downstream row is in the middle of the wake street from the upstream row allows the velocity defect normally in the rotor wakes to be thus cancelled at the position of the stator and considerably reduces the noise produced at the rotor blade passing frequency by the rotor wakes on the stator. The effect of stator wakes on rotor blades downstream of the first can be similarly reduced by lining up blades in successive rotor rows. The deductions are confirmed by measurements of sound pressure level.
Calculation of Temperature Distribution in Multistage Axial Gas Turbine Rotor Assemblies When Blades Are Uncooled
Authors: Evans D. M.
Published: November 2010

Calculation of the temperature distribution in the turbine rotor of the axial gas turbine engine is an essential preliminary to a meaningful calculation of the stress distribution and the prediction of related life of the various rotor elements. Where the turbine blades are uncooled, the element of chief concern is the turbine disk, with respect to achieving acceptable life. The art of performing a multistage axial gas turbine rotor assembly temperature distribution analysis is reviewed in detail with particular emphasis on choice of heat transfer correlations and boundary conditions in the steady state. Modification of the thermal model to yield transient temperature results is discussed briefly. Comparison of analytical results with some recent engine disk temperature measurements is presented.
NOx Emissions From Industrial Boilers: Potential Control Methods
Authors: Siegmund C. W. , Turner D. W.
Published: November 2010

Future regulations may limit emissions of NOx from industrial/commercial boilers as well as utility boilers. The potential methods of control for these boilers are the same as those for utility boilers—low excess air, flue gas recycle, and two stage combustion. Low excess air and flue gas recycle can control NOx from thermal fixation. Two stage combustion controls both thermal and fuel NOx. Further development work is needed to apply these combustion modification procedures to industrial/commercial boilers in which volumetric heat release rate is normally quite high.
On the Unsteady Supersonic Cascade With a Subsonic Leading Edge—An Exact First Order Theory—Part 2
Authors: Kurosaka M.
Published: November 2010

Pursuant to Part 1, the analysis of the aerodynamic forces acting on slowly oscillating airfoils in a supersonic cascade with a subsonic leading edge is presented. First the flow field between adjacent airfoils is determined. In the limit of sonic leading edge, the present results for the velocity potential agree with the sonic limit of Lane’s supersonic leading edge analysis. The requirement of the continuity of pressure in the “train” leads to functional equations for the train velocity; their solutions, obtained in closed form, are found to involve arbitrary constants which are related to the back pressure. The effect of the back pressure on the “train” is discussed in detail. For a cascade with zero pressure rise across it, the train velocity is determined completely and the formulas for lift and moment, accurate to the first order of a frequency parameter, are obtained in closed form. Stability criteria for a single-degree-of-freedom motion are examined. A pure bending motion is found to be stable, but a pure torsional motion becomes unstable under certain circumstances. These results are consistent with analogous oscillations of an isolated airfoil. However, the stability boundary for a typical cascade differs significantly from the case of the isolated airfoil, being strongly influenced by such cascade parameters as solidity, blade-to-blade phase difference, and stagger angle.
Reduction of NOx by EGR in a Compact Combuster
Authors: Hazard H. R.
Published: November 2010

The effect of EGR (Exhaust Gas Recirculation) on the emission of NOx, CO, and HC from two compact, low-emission burners sized for use in automotive Rankine-cycle engines was studied experimentally. One burner was a lean-primary design, and the other was a rich-primary design. Both had been developed to meet 1976 Federal Emission Standards for automobiles. It was shown that EGR resulted in significant reduction of NOx emission from both burners, with negligible effect upon emission of HC and CO. The effect of EGR was additive to the effect of excess air, staged air admission, and wall cooling.
Residual Stresses in Gas Turbine Engine Components From Barkhausen
Noise Analysis
Authors: Barton J. R. , Kusenberger F. N.
Published: November 2010

The Barkhausen noise analysis method for nondestructive residual stress measurement in ferromagnetic steels is described. Photographs showing the influence of stress on magnetic domain walls are presented; qualitative and quantitative calibration results are summarized. Results of exploratory measurements on a variety of jet engine components: compressor blades, compressor disks, diffuser cases and ball bearings, are presented and discussed.