bluuebunny/crossref_metadata_2025 huggingface dataset:
Displacement Analysis of Spatial Seven-Link 5R-2P Mechanisms
Authors: Duffy J.
Published: November 2010

Input-output displacement equations of eighth degree are derived for general spatial seven-link (RPPRRRR, RRRPPRR), (RPRRRPR, RPRRPRR), and (RPRPRRR) mechanisms. The results are verified by numerical examples. The solutions of these mechanisms constitute a significant advance in the theory of analysis of spatial mechanisms. They contain as special cases the solutions for spatial seven-link 4R-3P slider-crank mechanisms, the solutions for all five-link 3R-2C and six-link 4R-P-C mechanisms that have appeared in the literature, together with the solutions for a multitude of solved and unsolved mechanisms containing spherical, torus, and plane kinematic pairs.
The Theory of Torque, Shaking Force, and Shaking Moment Balancing of Four Link Mechanisms
Authors: Elliott J. L. , Tesar D.
Published: November 2010

A method for the driving torque, shaking moment, and shaking force balancing is given as individual or combined problems for all of the four-link mechanisms: the four-bar, the slider-crank, the inverted slider-crank, and the oscillating block mechanism. The “method of linearly independent vectors” of Berkof and Lowen is extended to the shaking moment and driving torque functions. These tools are combined to completely eliminate shaking force and shaking moment with the addition of a physical negative mass. Specified values of driving torque can be met exactly in up to three positions or in the least-square sense for the full cycle while maintaining shaking force balance. For shaking moment, up to five specified moments or a cyclic moment in the least-square sense can also be obtained without, however, an accompanying shaking force balance.
Deformation Modes and Lip Fracture During Hole Flanging of Circular Plates of Anisotropic Materials
Authors: Johnson W. , Chitkara N. R. , Minh H. V.
Published: November 2010

An experimental investigation was carried out to determine the deformation leading to failure of the hole periphery in the hole flanging process using a conical punch. Circular plates of various hole sizes and of different materials were tested to different depths of punch penetration and the lip strain paths as well as the variation of thickness around the periphery of the lip were studied. In all cases, failure of the plate was due to lip fracture and the onset of lip instability was determined from the examination of the secondary surface texture of the lip of the plate during various stages of lip deformation. The instability strain in the hole flanging process was then calculated and it was found to be influenced by the process geometry and the plastic properties of the material. Hill’s model of plastic anisotropy for orthotropic materials was applied to a plane stress case to predict the variation of thickness around the periphery of the lip and the results were compared with experimental data. The influence of the anisotropic behavior of the material on the direction of lip fracture was also investigated.
Combing of Opening Room Blends of Cotton and Polyester
Authors: Graham C. O. , Rhodes P. L.
Published: November 2010

Opening room blends of 1.5 denier and 2.25 denier polyester/cotton were combed to improve blend homogeneity, and their processing and yarn properties were compared with those of conventional drawframe blends and combed cotton/polyester weigh-pan blends. Fewer processing steps were required to produce yarns of equal grade and tensile strength than by conventional blending methods. Combing of opening room blends of cotton/polyester can be a practical method of processing more homogeneous blends, even though some polyester was removed in the comber noils.
A Portable Personal Cooling System for Mine Rescue Operations
Authors: Webbon B. , Williams B. , Kirk P. , Elkins W. , Stein R.
Published: November 2010

The high temperatures, which are often encountered by mine rescue teams during emergency situations, may cause severe physiological strain. For example, at the Somerset coal mine, temperatures of 49°C (120°F) with 100 percent relative humidity caused the normal rescue team recovery mission to be shortened from 2 h to only 25 min. In order to increase the team’s effectiveness and comfort under such conditions, the U. S. Bureau of Mines (USBM) initiated a program with the National Aeronautics and Space Administration (NASA) to develop and test a personal cooling system based on technology developed for the thermal control of space-suited astronauts. The resulting system, which has 88 watt-h (300 Btu) heat absorption capacity, weighs approximately 5 kg (11 lb) and is compatible with existing rescue team breathing apparatus. Several different system configurations were tested under simulated mine rescue team operational conditions of 32.5°C (90°F) wet bulb globe temperature (WBGT) and 1.0 l O2/min (1200 Btu/h) metabolic rate. The system, which consists of a liquid circulation garment and belt-worn heat sink unit, was found to be capable of reducing the physiological strain by nearly 50 percent under these conditions. A simple analytical heat balance model was used to predict the effects of the thermal control system for other environments and metabolic rates. It was found that in the most severe environments, WBGT greater than about 35–37°C, that the maximum endurance time could be further increased by providing an insulating overgarment to reduce the heat gained from the hot environment.
Maximizing the Efficiency of Your Bucket Wheel Reclaimer
Authors: Hobson H. H. , Oyler J. F.
Published: November 2010

Proper application of a track-mounted reclaimer in a storage yard requires knowledge of the machine and the parameters which affect its efficiency. Several stockpile systems are discussed and the operation of a luffing, slewing travelling bucket wheel reclaimer is defined in detail. The effect of pile geometry, material characteristics, pile management and machine design on overall efficiency are evaluated with typical numerical results. Definitions for rating of reclaimers is given in terms of maximum and average performance.
Effects of Structural and Forming Parameters on the Efficiency of Energy Transfer in Impact Forming Machines
Authors: Vajpayee S. , Sadek M. M.
Published: November 2010

This work deals with the efficiency of energy transfer in impact forming machines due to the interaction of the process with machine structure as represented by a two degree-of-freedom (dof) system. The forming process is simulated by a rectangular force pulse as a function of time [1]. The effects of various parameters of the structure and also of the pulse on the energy transfer have been explored. It is found that the shock absorbers, commonly used for isolating the vibrations originating from such machines, restrict the attainment of 100 percent forming efficiency. Also, there exists a pulse-insensitive zone in the efficiency variation in which efficiency is independent of the forming operation and that the design of the machine should aim to achieve it.
Automated Optimum Design of Machine Tool Structures for Static Rigidity, Natural Frequencies and Regenerative Chatter Stability
Authors: Reddy C. P. , Rao S. S.
Published: November 2010

A computational capability for the automated optimum design of complex machine tool structures to satisfy static rigidity, natural frequency and regenerative chatter stability requirements is developed in the present work. More specifically, the mathematical programming techniques are applied to find the minimum-weight design of Warren-type lathe bed and horizontal knee-type milling machine structures using finite-element idealization. The Warren-type lathe bed is optimized to satisfy torsional rigidity and natural frequency requirements, whereas, the milling machine structure is optimized with constraints on static rigidity of the cutter centre, natural frequency and regenerative chatter stability.
Development of an Experimental Setup for the Investigation of Grinding of Wood and a Proposal for a Pulsed Loading Technique
Authors: Dornfeld D. , Wu S. M.
Published: November 2010

The study of the fiberizing mechanism in the grinding of wood requires specialized laboratory equipment to allow process alteration and data collection. The design and development of a unique grinding setup and the control device and instrumentation needed for wood grinding research are outlined. A pulsed loading technique for increasing the effectiveness of the fiberizing mechanism is proposed and this technique is tested in a series of experiments conducted with the grinding operations. Significant energy saving and pulp quality improvement for wood ground at 72 F (22.2 C) are achieved using a variable frequency and amplitude load pulsation superimposed over the constant grinding load. The pulsed loading technique can be used as a control device to minimize the effect of grinder input variation such as wood properties or stone surface conditions by altering the process during grinding to optimize the effect of the fiberizing mechanism.
Tool Life Distributions—Part 3: Mechanism of Single Injury Tool Failure and Tool Life Distribution in Interrupted Cutting
Authors: Ramalingam S. , Peng Y. I. , Watson J. D.
Published: November 2010

Tool life distribution under production machining conditions must be suitably accounted for in any rational design of large volume or automated machining lines. Reliable data on the type of distributions likely to be encountered are, however, unavailable. To remedy this, using relevent physical arguments, probabilistic models of tool failure which produce distribution functions germane to tool life scatter have been proposed and developed in earlier parts of this paper. An arbitrarily introduced hazard function was used to predict the life distributions likely to be obtained. The details of the mechanisms giving rise to tool failure were, however, not examined. Mechanistic questions connected with the single-injury tool failure (tool fracture) are examined in this part. The arbitrarily introduced hazard function is shown to have a physical basis. It is shown that the hazard function is determined by the interaction between the characteristics of the environment in which the tool operates and the mechanical properties of the tool material. The concepts outlined and the mechanistic model of tool failure proposed have been tested experimentally in interrupted cutting. It is shown that the predicted Weibull-distributed tool life is obtained when tool failure is due to a single injury and that the parameters of the Weibull distribution are governed by the properties of the tool material as well as those of the machining system.
Melt Spinning of Fibers: Effect of Air Drag
Authors: Kwon Y. D. , Prevorsek D. C.
Published: November 2010

Experimental measurements of the magnitude of air drag on the filament and the air velocity profile around the filament in the spinning and drawing down of a fiber filament in the surrounding of stagnant air are reported. The results are examined in comparison with the existing theoretical correlations which have been used in the studies of the spinning processes. The experimental values of the air drag are found to be larger than the values based on the existing correlations to such an extent that, in some cases of past studies, the air drag effect on the filament tension may have been underestimated.
Plug Flow of Bulk Solids Using Gas Pressure Control
Authors: Emery R. B.
Published: November 2010

This paper considers interstitial fluid pressure as an additional characteristic effecting bulk solids flowability. It describes a method for improving flow control of cement, powdered coal, sand, etc. through a converging hopper by applying particle stress-ratio control. In some applications, flowability of bulk solids can be modified rather than make costly modifications to the hopper. The patented method combines a baffle, a slot opening and gas pressure control modifying flowability in a converging channel. Plug-flow, a preferred type of mass flow, has been achieved flowing cement through hoppers open to the atmosphere as well as through enclosed, pressurized hoppers.
Stress Rupture Behavior of a Dispersion Strengthened Superalloy
Authors: Cairns R. L. , Benjamin J. S.
Published: November 2010

A dispersion strengthened nickel-base superalloy, designated IN-853, has been made by a new process called “Mechanical Alloying.” This provides a long sought combination of properties typical of dispersion strengthened and precipitation hardened materials. The alloy has flat rupture curves over a wide temperature range. Rupture stress/temperature curves for the alloy show a transition separating the low temperature regime where precipitation hardening controls the strength, and the high temperature range where dispersion strengthening predominates. The slope of a Larson-Miller plot of stress rupture test data also decreases at high values of that parameter. At high temperatures rupture stress is less sensitive to temperature changes than is the case with conventional nickel-base superalloys. At a fixed stress level the rupture life of the dispersion strengthened superalloy is more sensitive to temperature changes.
Elastic-Plastic Deformation in Edge-Notched Tension Specimens Under Plane Stress Conditions
Authors: Griffis C. A.
Published: November 2010

An elastic-plastic, plane stress, finite element analysis has been performed on edge-notched tension members having elastic stress concentration factors of 2.28 and 3.06. For net section stresses below general yield, experimentally measured notch root strains are within 12 percent of those computed by the finite element method. The current results indicate that finite element analysis generally provides a better estimate of notch strain than either the Neuber or Hardrath-Ohman formulations.
Fractographic Study of Fatigue Crack Propagation
Authors: Koterazawa R. , Mori M. , Matsui T. , Shimo D.
Published: November 2010

Fractographic studies were carried out on fatigue fracture of aluminum alloys and carbon steels. Special attention was given to the correlation between striation spacing and macroscopic crack growth rate and to the effect of stress change on the crack growth rate as determined by striation spacing measurements. Also the mechanism of formation of striations and tire tracks was examined by means of precisely matched electron fractographs of matching fracture surfaces. Some remarks are also made on the mechanisms of fatigue crack propagation.
The Optimal Column
Authors: Carter W. J. , Ragsdell K. M.
Published: November 2010

A new numerical search algorithm is presented which is employed to determine optimum shapes for pin-ended columns having elastic behavior. The search algorithm utilizes a gradient search scheme to seek out the optimum solutions. A Lagrange-like solution is given for the Strongest Column Problem of Lagrange.
Prediction of the Tensile Properties of Sheet Metal Composites
Authors: Beese J. G. , Bram G. M.
Published: November 2010

Sheet metal laminates are becoming more widely used because of advantageous combinations of the properties of their component parts. Theoretical equations have been developed to predict the tensile properties of laminates to aid selection from the list of many possible combinations of different materials. The equations have been used to predict the values of the tensile properties of copper/steel and aluminum/steel composites; these predictions have been checked against measured values. An empirical rule of mixtures is often used to predict the properties of laminates; the theoretical analysis has been used to justify, or otherwise, the use of this simple linear realtionship.
Plastic Energy Required for Fatigue Failure of Specimens Containing Cracks
Authors: Bui-Quoc Thang , Biron Andre
Published: November 2010

A study is conducted to determine the plastic energy absorbed by a material subjected to cyclic loading during the crack propagation stage. The analysis is based on Liu’s elastoplastic solution for calculating the plastic energy around the crack tip combined with a modified crack propagation law. The plastic energy per cycle Δw is found to be dependent upon the fatigue crack length and therefore varies with the number of applied cycles. The mean value of this energy corresponds to the plastic energy obtained by measuring the area within the stress-strain hysteresis loops of the material under repeated loading. If fatigue damage is based on plastic energy, the trend of variation of Δw with the applied cycles in the present analysis shows that the application of the linear damage rule (such as Miner’s law) should be more successful in the low-cycle region than in the high-cycle region. This is consistent with experimental data.
Deformation Characteristics and Time-Dependent Notch Sensitivity of
Udimet 700 at Intermediate Temperatures
Authors: Wilson D. J.
Published: November 2010

Time-dependent notch sensitivity of Udimet 700 sheet, bar, and investment castings was observed between 1000 deg and 1400 deg F (538–760 deg C) but not at 1600 deg F (871 deg C). As was the case for Modified Waspaloy, Waspaloy, Rene´ 41, INCONEL 718 and TD-NiCr, it occurred when notched specimens were loaded below the yield strength and when creep deformation was localized. For each γ′ strengthened alloy and notched specimen geometry, a stress-average particle size zone can be defined to characterize the notch sensitive behavior.
An Inelastic Constitutive Model for Monotonic, Cyclic, and Creep Deformation: Part II—Application to Type 304 Stainless Steel
Authors: Miller A.
Published: November 2010

For the deformation model developed in Part I, material constants are calculated from standard test data on type 304 stainless steel. With them, simulations are made of various types of tests, including tensile tests, strain-rate sensitivity, creep tests with stress drops, strain-controlled cycling, and creep-fatigue interaction. The simulations show general agreement with the corresponding experimental data for type 304, but in a few respects, quantitative improvements are required. Implications of the strengths and weaknesses of the new model are discussed.
An Incremental Criterion for Time-Dependent Failure of Materials
Authors: Bodner S. R. , Lindholm U. S.
Published: November 2010

A criterion for the time-dependent failure of materials is developed based upon the concept that failure results from an incremental accumulation of damage. The failure criterion is thereby explicitly tied to the incremental flow law describing the inelastic deformations. The damage increment is assumed as a product of functions of the stored strain energy due to inelastic deformations, the mean hydrostatic stress, and the damage itself. The consequences of the failure criterion for various types of loading are discussed.
An Improved Fracture Criterion for Three-Dimensional Stress States
Authors: Paul B. , Mirandy L.
Published: November 2010

A theory is developed to predict the onset of fracture in isotropic, brittle materials when subjected to three dimensional states of applied stress. It is assumed that fracture is precipitated by stress concentrations emanating from material flaws. The flaw model which has been adopted consists of randomly oriented, microscopic, flat triaxial ellipsoidal voids imbedded in an otherwise defect-free material. It is shown that the ensuing fracture criterion may be expressed as a parabolic Mohr’s envelope. These results are qualitatively similar to Paul’s earlier three-dimensional generalization of Griffith’s two-dimensional stress fracture criterion. To handle three-dimensional states of applied stress, Paul used an approximation based on two-dimensional elasticity to obtain the state of stress around a flat spheroid. Newly developed results for flat ellipsoidal cavaties are utilized herein to analyze the three-dimensional cavity. Pertinent effects due to Poisson’s ratio and ellipsoid geometry are reported.
The Relation Between Ultimate Tensile Strength and Carbide Size in Steel
Authors: Lui M.-W. , Le May I.
Published: November 2010

The paper demonstrates that a definite and simple relationship exists between ultimate tensile strength (or Brinell hardness) and the carbide size in steels, for a given carbide shape and volume fraction. This is explained on the basis that microvoid initiation, by decohesion at the carbide/matrix interface or by fracture of the carbide itself, is the critical event in the ductile fracture of these materials, and the stress required for microvoid formation may be related to the ultimate tensile strength.
Cumulative Fatigue Damage on Large Steel Specimens Under Axial Programmed Loading With Nonzero Mean Stress
Authors: Bui-Quoc T. , Choquet J. A. , Biron A.
Published: November 2010

Large specimens of an ASTM E-373-58T steel were subjected to zero-tension cyclic loading, hence with nonzero mean stress, under a repeated programmed pattern of nine stress levels. With the major stress twice the minor stress, the levels in the loading pattern were chosen in such a manner that they had approximately a sinusoidal wave as an envelope and the stress cycle at each step was repeated 500 times. The experimental results show a trend of variation of the cycle-ratio summation similar to that obtained on tests with zero mean stress; the higher the number of stress levels in the loading pattern below the original endurance limit, the larger the deviation from unity of this summation. A comparison is made between the predicted lives according to the linear cumulative damage rule and according to an alternative theory which takes into account the variation of the endurance limit (Unified Theory). It is found that the Unified Theory is more conservative and provides better estimates in the high-cycle range in particular for cases where there are, in the stress pattern, several levels lower than the endurance limit of the original material.
An Exponential Stress-Strain Law for Cyclic Plasticity
Authors: Liu M. C. M. , Krempl E. , Nairn D. C.
Published: November 2010

A previously proposed nonlinear differential constitutive equation for creep-plasticity interaction under a uniaxial state of stress is specialized for the time independent case. The characteristics of the second derivative of the stress-strain diagram are matched by an exponential function. The integration yields higher transcendental functions. For the matching of the stress-strain diagram, four easily obtainable constants are necessary at each cycle which are fed into a newly developed FORTRAN computer program. A plotting routine yields stress-strain diagrams and hysteresis loops. The procedure gives good matches for stress-strain diagrams of Type 304 stainless steel. Specifically, stress-strain diagrams for various product forms and the initial cyclic hardening of this material are reproduced quite accurately without the usual decomposition into elastic and plastic strains.
A Mechanical Equation of State for Inelastic Deformation of Iron: An Analytic Description
Authors: Rohde R. W. , Swearengen J. C.
Published: November 2010

The applicability of two familiar analytic descriptions of micromechanical deformation as equations of state for polycrystalline iron is discussed. These equations are the power law and the relationship based on reaction rate theory. It is shown that the reaction rate description fails to describe adequately individual stress relaxation events without invoking undue complexity from use of adjustable parameters. Moreover, even in that case, this formulation lacks the predictive capability required in an equation of state. Conversely, the power law is found not only to describe stress relaxation data properly but also to provide the capability of predicting stress relaxation following initial deformation by different loading paths. It thus appears to represent an equation of state for the material.
Fast Burst Reactor Burst Rod Adaptor Failure Analysis
Authors: Hull W. C. , De La Paz A. , Welch D. L.
Published: November 2010

Failure of a 440C stainless steel burst rod adaptor from the White Sands Missile Range Fast Burst Reactor is analyzed. The operational history of the adaptor, including nature of loading, radiation accumulation, and thermal environment, was examined. Problems associated with handling radioactive materials were overcome through careful monitoring and disposal. The chemical composition of the adaptor material was checked by x-ray and electron probe spectroscopy. The failure surface was examined and photographed at various magnifications, using optical and scanning electron microscopes. Areas of crack origin, rapid fracture, final breakoff, and abrasion from rebound are identified. Metallographic specimens were prepared, the grain structure examined, and hardness profiles obtained. The grain structure indicated the presence of microvoids and carbide segregation, and slight hardening was noted. Failure occurred at the base of a male thread in a region showing significant tool markings. Examination of the failure surface indicated crack initiation due to Stage I fatigue followed by rupture from shock overload. Recommendations to avoid similar occurrences are given.
J-Integral Approach to Fracture of Rotating Disk
Authors: Sakata M. , Aoki S. , Kanzawa M. , Ogure N. , Tateishi K.
Published: November 2010

The J-integral has been used as a fracture criterion for elastic-plastic behavior of metals. It may be pertinent to use the JIc concept for design or nondestructive inspection of rotating disks which have crack-like flaws and exhibit some amount of plastic behavior to fracture. JIc for cracked rotating disks of rotor forging steel is determined experimentally and is compared with that obtained using compact specimens. It is shown that prediction based on the compact tension tests agrees well with initiation of crack growth in rotating disks.
The Room Temperature and Elevated Temperature Fracture Toughness Response of Alloy A-286
Authors: Mills W. J.
Published: November 2010

The elastic-plastic fracture toughness (JIc) response of precipitation strengthened Alloy A-286 has been evaluated by the multi-specimen R-curve technique at room temperature, 700 K (800°F) and 811 K (1000°F). The fracture toughness of this iron-base superalloy was found to decrease with increasing temperature. This phenomenon was attributed to a reduction in the materials’s strength and ductility at elevated temperatures. Electron fractographic examination revealed that the overall fracture surface micromorphology, a duplex dimple structure coupled with stringer troughs, was independent of test temperature. In addition, the fracture resistance of Alloy A-286 was found to be weakened by the presence of a nonuniform distribution of second phase particles throughout the matrix.
On the Theories of Sheet Metal Necking and Forming Limits
Authors: Korhonen A. S.
Published: November 2010

The history and the present state of the theory of sheet metal forming limits are reviewed. The theory of necking and plastic instability (Swift-Hill and Marciniak-Kuczyn´ski models) is discussed and theoretical limit strains are calculated. The influence of the strain path on the theoretical limit strains is discussed with computational examples. At the present no theory can fully explain the localized necking in stretch forming.
Application of the R-Curve Concept to Fatigue Crack Growth
Authors: Wilhem D. P. , Ratwani M. M.
Published: November 2010

Crack growth resistance for both static (rising load) and for cyclic fatigue crack growth has been shown to be a continuous function over a range of 0.1 μm to 10 cm in crack extension for 2024-T3 aluminum. Crack growth resistance to each fatigue cycle of crack extension is shown to approach the materials ordinary undirectional static crack resistance value when the cyclic stress ratio is zero. The fatigue crack extension is averaged over many cycles and is correlated with the maximum value of the crack tip stress intensity, Kmax. A linear plot of crack growth resistance for fatigue and static loading data shows similar effects of thickness, stress ratio, and other parameters. The effect of cyclic stress ratio on crack growth resistance for 2219 aluminum indicates the magnitude of differences in resistance when plotted to a linear scale. Prediction of many of these trends is possible using one of several available crack growth data correlating techniques. It appears that a unique resistance curve, dependent on material, crack orientation, thickness, and stress/physical environment, can be developed for crack extensions as small as 0.076 μm (3 μ inches). This wide range, crack growth resistance curve is seen of immense potential for use in both fatigue and fracture studies.
Plastic Deformation of Anisotropic Tubes in Hydraulic Bulging
Authors: Woo D. M. , Lua A. C.
Published: November 2010

The anisotropy of tubular material is assessed from the values of the width/thickness strain ratio determined in the tension tests. Applying Hill’s theory of plastic anisotropy, these values are incorporated in the expressions for determining the stress/strain characteristics for anisotropic material in the tension and bulge tests, and also in the theoretical analysis of the hydraulic bulging of anisotropic tubes. Experiments have been carried out on copper tubes. Taking into account the anisotropy effect, the stress/strain curves determined in the tension and bulge tests agree closely except at the low strain region. In the analysis of the bulging process, comparison is made between the theoretical and the experimental circumferential strain distribution. The results appear satisfactory.
Low Level Charpy Impact Response of Graphite/Epoxy Hybrid Composites
Authors: Adams D. F. , Perry J. L.
Published: November 2010

Laminated graphite/epoxy composites, with and without the addition of plies of glass fabric/epoxy or unidirectional glass yarn/epoxy, were subjected to impact levels less than those necessary to cause total failure. These low level impact specimens, and undamaged control specimens as well, were then subjected to either static flexure or full impact loadings. Using an instrumented impact testing machine, the maximum impact forces and the impact moduli were determined, and compared to the corresponding values from the static tests. The maximum force was independent of loading rate, while the impact modulus was significantly less than the static flexural modulus. The various composites were found to be severely degraded by the low level impacts.
A Critique of MHD Power Generation
Authors: Jackson William D. , Petrick Michael , Klepeis James E.
Published: November 2010

Magnetohydrodynamic electrical power generation is a promising new technique for upgrading the efficiency of converting heat into electricity. The concept has been explored intensively but on a small scale during the past ten years, and the initial enthusiasm in it has been confirmed. Its utilization in base-load plants, in addition to increasing overall efficiency, can also lead to important reductions in the adverse environmental effects of thermal and air pollution. The projected efficiencies of large dual cycle systems are initially in the range of 47–50 percent, and improvements in technology could later increase this to 60 percent. In an MHD system, energy is extracted from a flowing electrically conducting fluid. The fluid may be either a seeded plasma or a liquid metal. Various MHD power cycles and systems are therefore under consideration. The status of these systems will be reviewed with emphasis on their application to large central-station commercial systems. The major technological problems and progress in the three major cycles (open cycle, closed-cycle plasma, and closed-cycle liquid metal) will be discussed in depth. In the open-cycle system, the engineering solutions that have been proposed for the major problems in the generator and auxiliary equipment will be detailed. In addition, the experience gained from the operation of a succession of generators will be summarized. In the case of the closed-cycle plasma system, the progress that has been made toward developing a generator with the requisite conversion efficiency will be cited. Recent cycle analyses that have established the conditions for matching these systems to current heat sources will also be reviewed and their implications noted. The potential of developing liquid-metal MHD systems for commercial application will be explored in the light of recently obtained experimental and analytical performance information. In particular, promising new techniques that can lead to improved efficiencies will be detailed.
Some Boundary Layer-Porous Wall Coupling Effects in Laminar Flows With Surface Injection
Authors: Nealy D. A. , McFadden P. W.
Published: November 2010

Using the integral form of the laminar boundary layer thermal energy equation, a method is developed which permits calculation of thermal boundary layer development under more general conditions than heretofore treated in the literature. The local Stanton number is expressed in terms of the thermal convection thickness which reflects the cumulative effects of variable free stream velocity, surface temperature, and injection rate on boundary layer development. The boundary layer calculation is combined with the wall heat transfer problem through a coolant heat balance which includes the effect of axial conduction in the wall. The highly coupled boundary layer and wall heat balance equations are solved simultaneously using relatively straightforward numerical integration techniques. Calculated results exhibit good agreement with existing analytical and experimental results. The present results indicate that nonisothermal wall and axial conduction effects significantly affect local heat transfer rates.
Vibration Characteristics of Low Aspect Ratio Compressor Blades
Authors: Petricone Ralph , Sisto Fernando
Published: November 2010

This paper presents the results of a study of the vibration characteristics of low aspect ratio compressor blades. The treatment is based on thin shell theory and the Rayleigh-Ritz method is used to obtain the eigenvectors and eigenvalues. The object is to elucidate those characteristics which are inaccessible using beam theory. Results are presented which show the variation of the natural frequencies and mode shapes with angle of twist, aspect ratio, and angle of inclination of the base of the blade. A three-dimensional plot of the bending mode frequencies versus aspect ratio and twist angle is presented. Although the surfaces describing the variation of frequencies for specific modes do not intersect, there is a point of contact. This contact point is significant in the transition of mode shapes along the frequency surfaces. It is demonstrated that the “stiff-direction” or “in-plane” vibration of the untwisted plate evolves into coupled bending modes as the twist angle increases from zero and that the character of these modes changes in the vicinity of the contact point.
Thermal Stress and Fatigue Analysis in Turbine Rotors
Authors: Chow C. L.
Published: November 2010

A method of thermal stress and fatigue analysis under triaxial stress conditions is presented. A rotor of a marine steam turbine is taken as a typical example to illustrate the detailed method of analysis in assessing the cycle damage life of the rotor. A computer technique of iterative block relaxation is devised for the thermal stress calculation as the physical geometry of the problem under consideration is fairly complex. This technique is particularly advantageous for such a system as (a) damping the magnitude of the oscillation in the solution of the ill-conditioned stress equations and (b) keeping the number of nodal points required in a converging solution to a minimum. Three different operating procedures of starting and loading the marine turbine have been studied with full three-dimensional stress and fatigue considerations. One of the three procedures which is found to be more desirable is recommended with the descriptions of detailed steam history and main features of the cold start throughout its whole operation.
The Use of Flow Modeling Techniques to Obtain a Minimum Loss Design for the Stack Entrance Section of a 700-ft Power Plant Chimney
Authors: Gilbert G. B.
Published: November 2010

Scale model testing and flow visualization techniques were used to achieve substantial reductions in stack entrance total pressure loss levels. This paper presents the loss coefficient results for three different model configurations for the stack entrance section at the bottom of a 700-ft power plant chimney. For the best configuration, an average stack entrance loss coefficient of 0.39 was achieved which represents a reduction of loss coefficient by a factor of 4.5 below the original unvaned design. For the lowest loss configuration, the entrance loss for one or several ducts can be substantially reduced below the other duct entrances by the correct specification of the velocity levels of the joining flow streams at the static pressure matching point.
Performance of Air-Cooled Radiatively Heated Screen Matrices
Authors: Hamid Y. H. , Beckman W. A.
Published: November 2010

The problem of combined radiation and convection in a porous bed, consisting of randomly stacked wire screens, was experimentally investigated. A collimated radiation source was used for bed heating, and air flowing normally through the bed was used for bed cooling. Both bed temperatures and air temperatures were measured at various locations. Comparisons are made with an analytical model which includes the effects of internal radiation exchange and convection between the bed and air.
2750 Deg F Engine Test of a Transpiration Air-Cooled Turbine
Authors: Moskowitz S. L. , Lombardo S.
Published: November 2010

The development of gas turbine engines for advanced subsonic and supersonic aircraft as well as for potential utilization of these high performance engines for stationary and marine applications requires, as a key element, the ability to operate at turbine inlet temperatures above the actual melting temperatures of the turbine materials. A limit on gas temperature levels is imposed by the fact that current alloys available for use in turbines, exhibit inadequate strength and oxidation characteristics above 1600–1800 deg F. However, the performance gains offered by operating engines at a high turbine inlet temperature may be realized through the application of an efficient method of cooling the highly stressed turbine components. As a step toward demonstrating that transpiration cooling of turbine blading is an effective means for achieving reliable and efficient gas turbine operation in a high gas temperature environment, a full-scale engine was tested at average gas temperatures of 2750–2800 deg F with a transpiration cooled turbine fabricated from normally used turbine alloys which are limited to metal temperatures of 1600–1800 deg F. The authors discuss the design of the transpiration air-cooled turbine, the technique used in fabricating the porous turbine blading, and the experimental test results obtained from operating the high-temperature engine. Furthermore, correlation of the test results on blade cooling with analytical predictions is presented.
The Effectiveness of Film Cooling With Three-Dimensional Slot Geometries
Authors: Nina M. N. R. , Whitelaw J. H.
Published: November 2010

The paper describes measurements of adiabatic wall temperature downstream of discrete hole injection slots for a range of parameters relevant to gas turbine practice. The influence of open-area-ratio, slot-lip-length and slot-lip-thickness is determined for tangential holes and a range of mass velocity ratios, 0.3 < m < 2.0, and downstream distances up to 40 equivalent slot heights; similar measurements are reported downstream of three-dimensional splash cooling geometries. In all, 13 different three-dimensional configurations are investigated and permit conclusions to be drawn as to the significance of the parameters investigated. The measurements clearly demonstrate the need for a thin and long slot lip and for a large value of open area ratio.
An Investigation of Nonequilibrium Effects in an Internal Combustion Engine
Authors: Spadaccini L. J. , Chinitz W.
Published: November 2010

A theoretical analysis of the basic chemical kinetic processes which lead to the formation and partial decomposition of nitric oxide and carbon monoxide has been undertaken. A mathematical model of an Otto cycle engine has been formulated, programmed for the CDC 6600 computer, and used to determine species concentrations and thermodynamic properties at any point in the engine cycle. The validity of this model has been confirmed by the results of an experimental program conducted on a typical multicylinder automotive engine, and data available for a single cylinder CFR engine. In addition, the computerized model was used to describe the chemical and physical processes upon which existing control techniques for nitric oxide are based, and to investigate the potential of a new concept, fuel-rich combustion and secondary air injection, for minimizing nitric oxide and carbon monoxide emissions. A unique concept in controlling undesirable engine emissions, i.e., rich combustion followed by secondary air injection during the engine expansion, was shown to result in significant reductions in nitric oxide and carbon monoxide emissions without incurring an appreciable loss in thermal efficiency as compared to stoichiometric operation.
Proposed Gas Turbine Procurement Standard, Rating and Performance
Authors: Fejer A. A. , Hendrickson R. L.
Published: November 2010

It has been difficult for users to compare gas turbines produced by different manufacturers due to different approaches used in specifying terms and operating modes. This paper describes standard ratings and commonly used performance indicators, the dependence of these data on ambient conditions at the site of the gas turbine, and on the manner in which the machine is operated. This paper is one of a series of ASME papers (see Appendix) which present a proposed Gas Turbine Procurement Standard. Comments and suggestions would be welcomed by the authors in order to improve this material and hence result in a more usable Gas Turbine Procurement Standard.
Modeling of Gas Turbine Combustors—A Convenient Reaction Rate Equation
Authors: Kretschmer D. , Odgers J.
Published: November 2010

In order to model a practical combustion system successfully, it is necessary to develop one or more reaction rate equations which will describe performance over a wide range of conditions. The equations should be kept as simple as possible and commensurate with the accuracy needed. In this paper a bimolecular reaction is assumed, based upon a simple mass balance. Temperatures derived from the latter are related to measured practical ones such that, if required, an evaluation of the partly burned product composition can be made. A convenient reaction rate equation is given which describes a wide range of blow-out data for spherical reactors at weak mixture conditions. NVP2φ={1.29×1010(m+1)[5(1−yε)]φ[φ−yε]φe−C/(Ti+εΔT)}/{0.082062φyε[5(m+1)+φ+yε]2φ[Ti+εΔT]2φ−0.5} Analysis of the components used in the above equation (especially the variation of activation energy) clearly shows its empirical nature but does not detract from its engineering value. Rich mixtures are considered also, but lack of data precludes a reliable analysis. One of the major results obtained is the variation of the reaction order (n) with equivalence ratio (φ): weak mixtures, n = 2φ; rich mixtures, n = 2/φ. Some support for this variation has been noticed in published literature of other workers.
Flow Fields in a Two-Dimensional Diffuser With Extraction of Fluid on the Diverging Walls
Authors: Rockwell D. O.
Published: November 2010

A theory is developed to describe the inviscid core in two-dimensional unstalled diffusers with suction (extraction) on the diverging walls. Experimental wall static pressure distributions and streamline patterns agree well with those predicted theoretically. Under appropriate extraction conditions, a stagnation region is located downstream of the diverging wall extraction station. Experimental verification of the streamline patterns and of the location of this stagnation region was achieved via hydrogen bubble visualization. In addition, the possible stall conditions, which result if improper extraction is employed, are described qualitatively.
Removal of Sulfur Dioxide From Stack Gases: Recent Developments in Lime-Limestone Wet Scrubbing Technology
Authors: Elder H. W. , Thompson W. H.
Published: November 2010

Processes utilizing lime-limestone wet scrubbing technology are generally considered by the utility industry to be the best candidates for control of sulfur dioxide emissions from existing plants. Operating reliability is of prime concern and development work by several organizations is being conducted in an effort to find solutions to several major problems which are a deterrent to application of the processes. The problems include chemical scaling, process control, waste disposal, mist elimination, solids deposition in the scrubber circuit, and operation at reduced capacity. Results of experimental work in pilot and full-scale studies that bear on these problem areas are reported. Also, the status of plans for commercial application of lime-limestone wet scrubbing processes is summarized.
Development of Jet Pumps for Boiling Water Reactor Recirculation Systems
Authors: Kudirka A. A. , Gluntz D. M.
Published: November 2010

The efficiency of jet pumps used in Boiling Water Reactors has been significantly improved through extensive development efforts. These jet pumps are used inside the reactor pressure vessel as part of the reactor recirculation system to circulate subcooled water at about 530 deg F. The development of the first-generation and improved, second-generation jet pumps is surveyed, and the economic advantages of using them in a reactor are discussed. The development, geometry, and performance of these two jet pumps are described, their performance is compared, and the significant increase in efficiency obtained, resulting in the highest value reported in literature, is illustrated.
Steam-Turbine-Driven Circulators for High-Temperature Gas-Cooled Reactors—Part II: Development
Authors: Barbat V. J. , Kapich D. , Dahms F. C. , Yampolsky J.
Published: November 2010

The High-Temperature Gas-Cooled reactor is characterized by integration of the primary coolant circuit and components within a Prestressed Concrete Pressure Vessel. This concept requires particular features and assurance in the circulators that are used to circulate the primary coolant fluid. Each circulator employs a single-stage axial compressor driven by a single-stage steam turbine which is in series with the main steam turbo-generator. The circulator is lubricated by water and is capable of variable speed operation. The conception and design of the circulator were discussed in the first part of this paper. The present part describes the experimental development program of the series steam-turbine-driven helium circulator, which verified and supported the design methods and demonstrated the operational capability of the circulator in all the possible modes that could occur in plant operation.
Premixed Combustion in a Baffle Combustor and the Effect of Steam Injection
Authors: Roy P. , Schlader A. F. , Odgers J.
Published: November 2010

Details are given of the operation of a 90 deg annular sector of a ceramic-lined baffle-type combustor utilising premixed propane/air or propane/air/steam composition at ambient inlet conditions. Gas analyses are used to determine the combustion efficiencies, temperatures and compositions at a plane 8.9 in. downstream of the primary baffle. The results indicate the potential of the system for a low pollution chamber. They also show that most of the additional loss in efficiency, when steam is injected into the system, is due to increased hydrocarbon content.