bluuebunny/crossref_metadata_2025 huggingface dataset:
On Elastic Oscillations of a Thick-Walled Cylindrical Shell Subjected to Initial Finite Twist
Authors: Ertepinar A. , Wang A. S. D.
Published: November 2010

This paper is concerned with the natural vibrations of a rubber-like, thick-walled tube which is prestressed by an initial finite twist about the axis of the tube. The analysis is based on a rigorous theory of finite elasticity and the extended theory of small displacements superposed on large elastic deformations. Numerical results are obtained for tubes made of a neo-Hookean material. The fundamental frequency of the vibrations is found to depend on the prestressed state of the tube. In particular, when the tube becomes unstable under the initial twist, then the corresponding fundamental frequency ceases to be real-valued. When this happens, the problem becomes identical with that of torsional instability of similar tubes which was investigated earlier both analytically and experimentally.
A Study of Coupled Mathieu Equations by Use of Infinite Determinants
Authors: Lee Ti-Chiang
Published: November 2010

Hill’s method of infinite determinant is applied to solving a system of Mathieu-type equations. Expansion of the converging infinite determinant then leads to the criterion for stability of the solution. Numerical results are then presented in graphs for two examples. Good agreements between the present results and the existing solutions are observed. The criterion therefore is useful to predict the stability properties of a finite number of coupled Mathieu equations.
Finite Rotations and Associated Displacement Vectors
Authors: Kozik T. J.
Published: November 2010

The paper presents a definition of a finite rotation and a concise vector expression for the displacement vector associated with the rotation.
Stability of Liquid-Filled Spinning Spheroids Via Liapunov’s Second Method
Authors: Parks P. C.
Published: November 2010

In this paper the stability theory of Poincare´ and others, expounded in the last few pages of Sir Horace Lamb’s textbook Hydrodynamics, is extended by a stability analysis using Liapunov functions to cover the full nonlinear equations of motion of spinning liquid-filled spheroids. The linearized criterion is confirmed, that is for stability c/a < 1 or c/a > 3 where the semiaxes of the spheroid are a, a, c, the c-axis being also the spin axis. The unstable motion for 1 < c/a < 3 is examined, and a conjecture that viscosity will destabilize spinning spheroids with c/a > 3 is proposed.
On a Class of Modes Defined by Rosenberg
Authors: Pecelli G. , Thomas E. S.
Published: November 2010

We show that a certain class of Hamiltonian systems with positive-definite potential admits, at each energy level, a continuum of solutions which satisfy the four Rosenberg conditions for normal modes.
Frequency Domain Stability Criteria for Distributed Parameter Systems
Authors: Khatri H. C.
Published: November 2010

For distributed parameter systems, open-loop stability in the sense of bounded outputs for bounded inputs, and closed-loop asymptotic stability are considered. Frequency domain stability criteria for open and closed-loop distributed parameter systems are given. The closed-loop stability criterion is similar to V. M. Popov’s stability criterion for lumped systems. The criteria are limited to those linear, time-invariant systems whose dynamics can be described by a transfer function which is the ratio of the multiple transform of the output to the multiple transform of the input. The input may or may not be distributed. An example is given to illustrate the applications of the stability criteria.
In-Vivo Mechanical Properties of Soft Tissue Covering Bony Prominences
Authors: Ziegert J. C. , Lewis J. L.
Published: November 2010

In order to measure in-vivo bone accelerations, it is necessary to know the mechanical response of the soft tissue covering areas of bony prominence when a load is applied through a rigid contactor. Two methods are presented for determining this response in vivo. The first method is for quasi-static loading and the second method is for dynamic loading at approximately 2000 Hz. Results are presented for various subjects and contactor geometries.
Compensation of the Speed Governor of a Water Turbine by the Method of Inequalities
Authors: Coelho C. A. D.
Published: November 2010

The method of inequalities is used to design a compensator for the speed regulation of a Francis water turbine. Apart from the improvement in regulation achieved, this paper provides a partial evaluation of the potentialities of this method of design.
An Adaptive Control Policy of Discrete-Time Linear Systems With Random Parameters
Authors: Yoshimura Toshio , Kiyota Masanori , Soeda Takashi
Published: November 2010

An adaptive control policy of discrete-time linear systems with random parameters under a quadratic control cost function is treated. The policy is mainly based on the concept of one-measurement optimal feedback control. Simulation results indicate that the proposed method is superior to the certainty equivalence control.
A Flueric Gas-To-Liquid Interface Amplifier
Authors: Woods Robert L.
Published: November 2010

In certain applications it is necessary to control the flow of liquid by means of pneumatic signal. This paper discusses the design and operation of a flueric amplifier that accomplishes this control without moving parts or diaphragms and with no intermixing of fluids. The amplifier operates with pneumatic pressure-field deflection of a slightly turbulent liquid power jet. The amplifier has “infinite” input impedance since there is no measurable steady-state control flow over a large range of input pressures. Single-stage pressure gains of 25 and extremely high power gains have been achieved. The amplifier has a minimum dynamic range of 25 and a bandwidth suitable for many applications.
Analysis of Energy Demand Distribution Within Anthropomorphic Systems
Authors: Vukobratovic´ M. , Hristic D. , Ciric V. , Zecevic M.
Published: November 2010

The paper presents the fundamentals of a synthesis approach to the gait of an anthropomorphic robot. The mathematical algorithms necessary to obtain the driving torques in the powered joints of the exoskeleton anthropomorphic robot are also presented. Driving torques are calculated for some presented gait types. From known gait characteristics the dynamics imposed on one part of the system (prescribed synergy) are determined and the corresponding synergies of the complete anthropomorphic exoskeleton-patient system are calculated. A brief summary of experimentally obtained energy data gathered by previous investigators is presented and the results of energy analysis for two adopted gait types are discussed.
A Path Identification Procedure for Networks
Authors: Garg D. P.
Published: November 2010

A generalized procedure has been advanced for path identification in complex multiloop interconnected directed networks. Reference to transportation networks has been made for the sake of specificity in this paper although the proposed method is equally applicable to all types of directed networks. Typically, one may utilize such procedures for developing information aimed at an efficient traffic rerouting between a given origin-destination pair. The rerouting may be necessitated by situations such as vehicular congestion or adverse weather conditions along a previously assigned nodal segment. A network example illustrates the application of proposed algorithm.
Planar Thermic Elements for Thermal Control Systems
Authors: Buckley S. , McCarthy R. L.
Published: November 2010

Thermics is a newly emerging control discipline where heat flows are modulated by temperatures. Heat is the only energy medium necessary for control, analogous to other single-medium control disciplines such as electronics, hydraulies, pneumatics or fluidics. Although initially dominated by elements based on vaporization heat tranfser of the heat pipe, a new class of planar thermic logic and control elements has been invented that relies on conduction and convection heat transfer. Three different temperature modulated thermal resistors are presented to explore the various types of modulation possible. The convection type is shown in several variations (amplifier, NOR gate, and diode) to illustrate analog, digital, and nonlinear control elements. Bond Graph models and experimental data are presented on characteristics of these prototype devices.
Development and Testing of a 56-In-Dia Jointed Glass Pressure Hull
Authors: Murphy D. W.
Published: November 2010

During development of a spherical glass pressure hull made up of two hemispheres joined with a metallic joint ring, a problem of bearing edge cracking was encountered. A joint was developed through a series of model tests which placed the bearing edge in radial compression, thus eliminating the cracking. This joint was used to assemble a 56-in. spherical glass pressure hull which was proof-tested to 1610 psi (3650 ft) and cycled 100 times at 1000 psi (2250 ft). Three minor spalls occurred on the proof cycle. This spalling is attributed to either adhesion of the epoxy support material to the glass or support of surface irregularities by the epoxy. Testing was stopped at 100 cycles due to a failure in the epoxy seat-containing material. The joint concept appears workable to 4000 psi if the proper materials are used for the seat-containing material.
Strength of a Pipe Mitred Bend
Authors: Sobieszczanski Jaroslaw
Published: November 2010

Single and multiple mitred bends are analyzed for stress and deformation due to inplane bending and internal pressure. Theory of cylindrical shells is used as a tool of analysis. Results show maximum stress at the elbow increased up to more than 400 percent of the stress predicted by elementary beam theory. Influence of the elbow on the self-compensation of the heated pipeline is discussed and the local reinforcements proposed. Solutions are presented as graphs which may be directly applied in design work.
Synthesis of Four-Link Space Mechanisms Via Extension of Point-Position-Reduction Technique
Authors: Soni A. H. , Huang Matthew
Published: November 2010

The principle of point-position-reduction technique, which is used for position-synthesis of planar mechanisms, is extended to synthesize spherical four-link and spatial four-link RCCC mechanisms for four precision positions.
Fatigue of Cylinders Subjected to Pulsating Internal Pressure
Authors: Haslam G. H.
Published: November 2010

A method of estimating the fatigue strength and finite fatigue lives of components subjected to pulsating internal pressure is presented. An empirical expression describing the effect of the pressurization medium in contact with the bore surface is used, to correlate the fatigue strength of thick-walled cylinders subjected to pulsating internal pressure with the uniaxial fatigue strength of the cylinder material. This work is extended to examine the influence of high mean pressures. A fracture mechanics crack propagation law is used to estimate the finite fatigue lives of the cylinders. Estimated fatigue curves show good agreement with experimental results. Finally, design curves are presented from which fatigue limit and finite fatigue lives may be readily estimated.
Plastic Indentation of Steel Cylinders With Circular Punches
Authors: Sehgal M. M. , Kobayashi Shiro
Published: November 2010

The detailed deformation characteristics involved in axisymmetric plastic indentation was examined. Circular punches with flat and hemispherical ends were indented into specimens prepared from SAE 1215 steels under as-received and annealed conditions. The load-displacement curves were recorded, and measurements were made of the geometrical changes of the workpieces and of the strain distributions for various punch-workpiece dimensions. Furthermore, the mode of deformation was examined by revealing the flow lines, and fracturing of the workpiece was also observed.
Process Application and Design of Large Power Output Turboexpanders
Authors: Linhardt H. D.
Published: November 2010

The design parameters of turboexpanders and their influence on process optimization are reviewed with particular emphasis on hydrocarbon recovery processes requiring large power output turboexpanders. Plants with 100,000 horsepower expanders have not yet been built. However, the technology is available and novel test procedures are discussed in detail. This provides the necessary confidence for custom engineering of large turboexpander plants.
An Automatic V-Belt Transmission With an Asymmetrical Belt
Authors: Oliver L. R. , Hornung K. G. , Shapiro H. N.
Published: November 2010

A variable speed, V-belt transmission in which the belt has an asymmetrical cross-section was studied. The sliding sheaves adjust automatically to varying torque and speed requirements. A complete theoretical and experimental analysis was carried out and design equations derived were found to accurately predict performance in these drives.
Design of Energy Absorbing Upper Torso Restraint Systems
Authors: Ofodile E. I. E. , Hannell J. W.
Published: November 2010

Based on current DOT requirements for a car occupant restraint in car crashes, the load-extension characteristics for an upper torso belt system capable of safety restraining an average motorist in crashes up to 50 mph when worn snugly are analytically determined. The belt characteristics are shown to depend, among other factors, on the total inherent slack in and the permissible displacement of the belt system. Energy absorption is incorporated into the system by means of a mechanical device activated at a specific magnitude of bell load defined by the initial elastic belt elongation.
Automated Control for Ship Unloaders
Authors: Oyler J. F. , Withrow M. F.
Published: November 2010

User demands for higher performance from today’s clamshell unloaders have led to a critical examination of the operator himself. In order to reduce dependency on this unpredictable individual, it becomes desirable to automate the unloading cycle as much as possible to achieve maximum efficiency. This paper discusses some of the computer simulation which has been done to determine an automated cycle, and the electrical controls involved in implementing the automation.
On Optimum Design of Disk Brakes
Authors: Dike G.
Published: November 2010

This work describes the conduction of heat in a braking disk. It also gives a base for an optimum design of braking disks. The optimum theory is based on temperature as the limiting factor.
A Study of the Strain Distributions and Strain Histories in Axisymmetrical Stretch-Forming
Authors: Hsu T. C. , Lee P. K.
Published: November 2010

The strain distributions and strain histories in the axisymmetrical sheet metal forming process have hitherto been difficult to study owing to the lack of a succinct system of representation. The use of a triangular coordinate system to represent the strains in axisymmetrical sheet metal products is explained. Strain distributions and strain paths in sheet steel products are presented for processes involving variations in blank diameter, load on the pressure plate and punch profile radius. It is shown, by studying the growth of draw-in, that the effect of an increase in blank diameter is the same as that of increasing the load on the pressure plate. The various effects of a change in the punch profile radius are also discussed through the diagrams showing the strain distributions and strain paths.
Three-Dimensional Analysis of Form-Relieved Surface of Milling Cutter With Applications
Authors: Friedman M. Y.
Published: November 2010

The flank in multi-edge profiled cutters must be designed so that the profile geometry and the correct relief angle at every point of the cutting edge are preserved on repeated radial regrinding. The three-dimensional theory proposed for the problem was used in evaluating technological solutions for the design and production of the surface in question.
Transient Analysis of Offshore Loading Systems
Authors: Streeter V. L. , Wylie E. B.
Published: November 2010

Transient fluid flow caused by power failure to pumps or by accidental flow stoppage in offshore piping systems may be significant. This paper discusses analysis procedures with particular emphasis on an efficient and convenient means of handling the transient behavior of the turbopump. The interaction of the turbomachine with the piping and other appurtenances in the system is also discussed.
Monotonicity and Dominance in Optimal Hydraulic Cylinder Design
Authors: Wilde D.
Published: November 2010

Rigorous principles are derived for designing hydraulic cylinders optimizing a wide range of objective functions and stress constraints. Monotonicity and dominance are illustrated as general principles useful for identifying constraints critical at an optimum and simplifying design procedures. Optimal cylinder designs are shown to be of two types easy to compute. Constraint indicators are introduced to handle combinatorial aspects.
Inception of Cavitation From a Solid Surface
Authors: Miller G. E. , Rylander H. G.
Published: November 2010

This study of cavitation inception from a solid surface includes the presentation of an empirical model for the nuclei, a completely new design for experimental test equipment, a rigorous analysis of liquid conditions within the test section, and quantitative test data. The results prove that it is possible to reduce the effective size of cavitation nuclei, thereby making the interface more resistant to cavitation. The empirical model for cavitation nuclei provides the mechanism for bubble formation from gas-filled, submicroscopic crevices in a solid surface. The size of these nuclei may be reduced by forcing the liquid into these crevices. If the liquid-solid interface is hydrophilic, the pressure treatment is permanent, but the liquid will pull out of a hydrophobic interface thus providing only a temporary reduction of nuclei dimensions. The newly designed experimental equipment for cavitation inception studies has been demonstrated to produce cavitation under controlled conditions. The test section resembles a 180-deg journal bearing constructed in three slices. The middle slice is slid away from the journal to produce a diverging wedge which induces a tensile stress in the liquid. The inception stage of cavitation is detected by an acoustical probe. The temperature and pressure distributions in the thin film are calculated numerically by successively solving the energy and generalized Reynolds equations. A strongly implicit iteration algorithm is employed to solve the large set of simultaneous algebraic equations resulting from placing the nonlinear elliptic partial differential equations in finite difference form. Experimental data from test runs with petroleum oil, glycerin, and a glycerin-soap mixture showed that stress required for inception of cavitation could be determined with a repeatability of ±1.4 × 104 Pa (±2 psi). A linear relationship was experimentally determined to exist between the magnitude of pressure forcing oil into the crevices of a steel surface and a capacity of the oil-steel interface to withstand a tensile stress.
The Use of a Random Algorithm for Dynamic Optimization of Mechanisms
Authors: Sandler B. Z.
Published: November 2010

This paper describes the following two kinds of dynamic optimization problems applied to mechanisms and their solution by using the spectral theory of random processes: (1) One has to choose such parameters of three-mass vibrating system which will insure the minimum vibration of the most important element. (2) The possibility is envisioned of achieving output motion with minimal errors in a gearing mechanism, without increasing the accuracy of the wheels. It is suggested to achieve this effect by the choice of optimal teeth number combination. A randomized optimization algorithm is considered for these aims.
Rigidity Analysis and Optimization of Warren Beams in Torsion
Authors: Bahi R. C. , Chandra S. , Pandey P. C.
Published: November 2010

This paper reports analytical and experimental investigations on the static performance of warren beams in torsion. The theoretical results have been found to be in good agreement with the experimental values. The proposed theoretical model has further been used to obtain optimized proportions for the warren beams in terms of stiffness/weight criterion.
Optimum Design of a Complex Planar Mechanism
Authors: Mariante W. , Willmert K. D.
Published: November 2010

Presented is the optimal design of a planar mechanism whose configuration is generally more complex than those investigated in previous research. Specifically the paper deals with the synthesis of a linkage consisting of three connected four-bar chains used to open and close a convertible top of an automobile. The design objective and several of the constraints are of a type not previously considered in mechanism optimization problems. The formulation of the design problem is accomplished in such a way that an equality constraint, which would normally exist, is eliminated, resulting in a problem that is much easier to solve. The SUMT-Version 4 program is applied to the optimization, with a graphic computer terminal used to obtain an initial trial design. The optimal design is compared with a mechanism actually used in an automobile convertible top.
Influence of Flank Wear on the Stresses in a Cutting Tool
Authors: Chandrasekaran H. , Nagarajan R.
Published: November 2010

The present paper is devoted to the study of the influence of flank wear upon the contact and internal stresses in a single-point tool. A comprehensive model for the distribution of contact stresses along the wear land is proposed and compared with experimental results obtained from photoelastic investigations. For this purpose orthogonal machining of lead was carried out at low speed and constant depth of cut, making use of a transparent epoxy tool provided with a pre-honed wear flat along the flank surface. Wear level and rake angle seem to have influence on both the tool-chip and tool-work contact stresses in differing degrees. The elastic stress field in the tool wedge is evaluated analytically for given mixed boundary loading conditions. These results, on comparison with the experimental data obtained from photoelastic investigation and actual cutting test, indicate noticeable influence of wear level upon contact stress redistribution and stress field reorientation. Based on this, the role of flank wear upon the brittle strength of the tool is clarified.
Existence Criteria of Two-Loop Six-Link R-R-C-C-R-C-C Spatial Mechanism
Authors: Dukkipati R. V. , Soni A. H. , Pamidi P. R.
Published: November 2010

The necessary conditions for the existence of two-loop six-link R-R-C-C-R-C-C overconstrained mechanism are developed by extending Dimentberg’s approach of passive coupling. The developed conditions are examined to describe the geometry of the R-R-C-C-R-C-C mechanism for the existence of one general constraint.
Gross Motion Analysis of Planar Linkages With Application to a Geared Five-Bar
Authors: Vadasz A. F. , Soni A. H.
Published: November 2010

A generalized mathematical approach is developed to find the limit positions, hesitations, and dead-center positions of any given linkage. The approach is applied to study the motion of a geared five-link mechanism. It is shown that the limit positions of a geared five-link mechanism can be expressed in terms of a polynomial and that the degree of polynomial is a function of the gear ratio.
Spherical Acrylic Pressure Hulls With Multiple Penetrations
Authors: Stachiw J. D. , Dolan R. B.
Published: November 2010

An experimental program has been conducted to determine the effect of multiple penetrations on the performance of spherical acrylic plastic hulls under external hydrostatic pressure. As test specimens served 15-in. OD × 14-in. ID model scale NEMO spheres. The distribution of strains and the magnitudes of short term critical pressures indicate that the structural response of acrylic spheres with multiple penetrations to external hydrostatic pressure is identical to spheres with only one penetration equipped with a metallic closure providing that the included angles of the penetrations are ≤46 deg and the edges of the penetrations are at least one penetration radius apart. Based on these findings it is feasible to incorporate three or more large penetrations into the spherical hulls of acrylic submersibles without decreasing their operational depth rating that has been based on the experimentally proven structural performance of spheres with only one penetration, or two penetrations 180 deg center to center apart.
Failure of Cemented Carbide Tools When Executing Intermittent Cuts
Authors: Bhatia S. M. , Pandey P. C. , Shan H. S.
Published: November 2010

Premature failure of the cutting edge is a major problem associated with the application of cemented carbide tools in intermittent cutting operations. In such cases, unlike in continuous cutting, the tool edge fails due to fracture, well before the permissible limit of wear is approached. This paper reports some of the findings pertaining to the behavior of cemented carbide tools when used in interrupted cuts on a lathe. Based on the type of tool failure observed, the operating speed and feed range has been divided into four regions and the mode of tool failure in each region has been discussed. From the experimental results obtained, it is possible to specify a safe operating range for cemented carbide tools when executing intermittent cuts.
The Investigation of Locomotive Dynamics via A Large Degree of Freedom Modeling
Authors: Patadia S. , Craft W. J.
Published: November 2010

An analytical model of a locomotive due to S. Levy is modified to accept random track input and used as the basis of a locomotive study with 63 degrees of freedom. This model differs from precursors in that it is faster, it accepts nonlinear suspension components and wheel/rail interactions, it includes routines so that track irregulatiries may be incorporated by means of vertical and lateral PSD curves, it accounts for adhesion limits, checks derailment conditions, and provides time histories of generalized variables. With this code, a specific locomotive model, similar to the General Electric Company’s U33-C locomotive, is evaluated to ascertain what changes in either the model or the track parameters will permit higher safe speeds. This parametric study addresses speeds in the range of 70 to 280 ft/sec. (21.34 to 85.34 m/sec), three classes of track, 4, 5, and 6, primary suspension stiffnesses from 18 to 300 klbs/ft. (.263 to 4.38 MN/m), wheel flange clearances from .05 to .75 inches (1.27 to 19.1 mm) and the effect of vertical and lateral rail stiffnesses in the ranges of .5 to 8 and .25 to 4 Mlbs/ft. (7.3 to 117 and 3.65 to 58.4 MN/m), respectively. The results generally agree well with current standards governing safe running speeds on various class tracks. They indicate that at speeds equal to accepted safe operating speeds on class 4, 5, and 6 tracks, the rms values of the vertical forces at the contact of the first wheel and rail do not increase beyond 25% of the nominal vertical load at this point. Under these same conditions, maximum wheel-rail separations, if they occur, are for each case less than the wheel flange height assumed one inch (25.4 mm); for class 6 track, no separations larger than the flange height occur even at 280 ft/sec. (85.34 m/sec.).
A Momentum-Integral Analysis of the Three-Dimensional Turbine End-Wall Boundary Layer
Authors: Dring R. P.
Published: November 2010

An analysis is presented which is a combination of existing momentum-integral equations and existing studies of profile shapes for incompressible three-dimensional turbulent boundary layers. These, along with a number of suitable refinements and assumptions, result in a solution technique which is particularly well suited for turbine end-wall boundary layer calculations. The solution gives the distribution of the boundary layer thickness and skewing over the end-wall as well as the amount and flux of total pressure deficit of the flow leaving the end-wall at the suction surface corner. The analysis also disclosed that a shear term which is normally neglected in the boundary layer approximations must in fact be retained, at least in approximate form, in order to insure the stability of the integral equations.
Elasto-Plastic Cyclic Analysis of Structural Members
Authors: Koenig H. A. , Vogel W. , Cernoch L.
Published: November 2010

A two-dimensional elasto-plastic finite element analysis is developed herein which has the capability of analyzing structural members which are subjected to cyclic thermal-mechanical loadings. This analysis, therefore, is of great value in gas turbine applications. The analysis, which is based on an effective stress-strain formulation, employs a tangent modulus approach in its execution. Both principal and conventional stresses are computed in the body. Unloading procedures are established and subsequently employed in cyclic loading problems. Several examples are presented. A turbine blade shroud, which has been mechanically loaded due to interference with its adjacent member, is analyzed. Cyclic behavior is shown for a uniaxial tension specimen and then generalized to a multiaxial stress state. A “predictor-corrector” procedure, which calculates the most efficient loading increment, is developed. Analyses of stress concentration factors and thermal stress applications are also presented.
The Use of a Finite Difference Technique to Predict Cascade, Stator, and Rotor Deviation Angles and Optimum Angles of Attack
Authors: Dodge P. R.
Published: November 2010

This paper develops a method of using a quasi-three-dimensional finite difference (blade to blade) flow program to predict deviation angle. The work discussed herein was accomplished in support of Contract NAS3-15324 with Lewis Research Center of NASA, Cleveland, Ohio. An appropriate approximation to the Kutta Condition is developed. Results are compared with experimental data from cascades including the effects of meridional velocity ratio and compressibility. Predictions are extended to cases with radius changes. In addition, the same program is used to predict optimum angle of attack for a compressor blade row.
Similarity Parameters for Comparing Erosive Particle Trajectories in Hot Air and Cold Air Radial Inflow Turbines
Authors: Clevenger W. B. , Tabakoff W.
Published: November 2010

The similarity parameters that can be used to relate erosive particle trajectories in hot gas and equivalent cold gas flows are derived from the equations of motion. The flow in a radial turbine is used as the basis for studying the range of applicability of these similarity parameters. The study includes the vortex and rotor regions of the radial turbine and indicates the ranges of Reynolds number within which these parameters can be used. In addition, the study shows that when general trends of particle trajectories are to be considered, and precise trajectories are not necessary, one of the similarity parameters can be used for Reynolds numbers that are not within the limits indicated for precisely similar trajectories.
Elementary Three-Dimensional Interactive Rotor Blade Impact Analysis
Authors: Cornell R. W.
Published: November 2010

A theoretical analysis is presented which defines the loading and response of a rotor fan blade due to soft or frangible impacts in terms of the three fundamental modes of vibration by representing the blade as a lumped, spring-mass system. The analysis includes the effects of centrifugal stiffening, blade twist, retention stiffness and orientation, damping, and blade motion and deflection on the impact force. The features, solution, program, and applications of this analysis are reviewed, and the results are compared with those from a number of blade and specimen tests and found to be in good agreement.
Industrial Power Rates in the Mid-Eighties
Authors: Keith R. M. , Morris G. R. , Mangione B.
Published: November 2010

The full impact of higher cost fuel and plant construction costs have not been factored into today’s industrial electrical power rates. New power plant units committed in the late sixties and early seventies at sharply higher costs, higher financing charges and the phasing in of higher fossil fuel costs will create the need for sizeable rate increases over the next eight to ten years. This paper presents one technique for forecasting future industrial rates which takes into account the impact of the major parameters of fuel, cost of capital (financing) and the utility’s rate base on the development of customer class revenue. A sensitivity analysis is included which examines the effect of changes in fuel costs, new rate design proposals and financing costs. It is shown that these variations will add from 0.72 to 1.85 cents/kWh to the projected base rate of 2.85 cents/kWh in 1985. This is a total increase of over 94–154 percent compared to the actual rate of 1.85 cents/kWh in 1974.
Hot Corrosion of Gas Turbine Components
Authors: Patarini V. , Bornstein N. S. , DeCrescente M. A.
Published: November 2010

Hot corrosion is the accelerated rate of oxidation of coatings and substrates, which occurs when a condensed phase is present on the surface. The major constituent of the corrosive deposit is sodium sulfate, although when fuels other than light distillates are employed, the deposit can contain various amounts of vanadium pentaoxide, an impurity present in many heavy distillates and most residual oils. Other corrodents that can be present in varying concentrations are lead, carbon and alkali halides. The coatings employed to extend the life of gas turbine alloys, and the alloys themselves exhibit varying degrees of resistance to hot corrosion. In our study of the “Parameter Monitoring for Corrosion Control of Utility Gas Turbines” we are determining the relative effect of each of the aforementioned corrodents with respect to simple aluminides, overlay coatings and precious metal coatings on three nickel base superalloys and one cobalt base superalloy. Although these studies are being conducted over the temperature range from 1500 to 1800°F, this presentation primarily emphasizes the completed high temperature results with some examples of the ongoing lower temperature studies.
Theoretical Investigations and Numerical Evaluations of Wall Effects in Cavity Flows
Authors: Popp S.
Published: November 2010

The wall effects for fully and partially cavitating flows are investigated for both compressible and incompressible two-dimensional jets. The exact solution for Roshko’s model in a channel with a wedge shaped body is obtained and some particular models are studied. The hodograph method as developed by S. V. Falkovitch [19] is used and the solutions are given as infinite series of Chaplygin’s functions. The exact expressions of the drag coefficients for the aforementioned configurations are also given. Numerical computations are carried out for wedges of all angles. Tables and diagrams are included.
Theoretical and Experimental Study of Wall Region Periodicity for Turbulent Pulsatile Flow
Authors: Thomas L. C. , Shukla R. K.
Published: November 2010

Attention is focused in this study upon the development of a surface renewal-based analysis of transitional turbulent pulsatile flow and upon the experimental measurement of the instantaneous wall region turbulent periodicity. The resulting theoretical predictions and experimental measurements for periodicity provide a direct test of the validity of the model. The theory and experiment taken together provide further physical insight into the mechanism associated with this complex problem.
Laminar Film Condensation From a Steam-Air Mixture Undergoing Forced Flow Down a Vertical Surface
Authors: Denny V. E. , Mills A. F. , Jusionis V. J.
Published: November 2010

An analytical study of the effects of noncondensable gas on laminar film condensation of vapor under going forced flow along a vertical surface is presented. Due to the markedly nonsimilar character of the coupled two-phase-flow problem, the set of parabolic equations governing conservation of momentum, species, and energy in the vapor phase was solved by means of finite-difference methods using a forward marching technique. Interfacial boundary conditions for the numerical solution were extracted from a locally valid Nusselt-type analysis of the liquid-film behavior. Locally variable properties in the liquid were treated by means of the reference-temperature concept, while those in the vapor were treated exactly. Closure of the numerical solution at each step was effected by satisfying overall mass and energy balances on the liquid film. A general computer program for solving the problem has been developed and is applied here to condensation from water-vapor–air mixtures. Heat-transfer results, in the form q/qNu versus x, are reported for vapor velocities in the range 0.1 to 10.0 fps with the mass fraction of air ranging from 0.001 to 0.1. The temperature in the free stream is in the range 100–212 deg F, with overall temperature differences ranging from 5 to 40 deg F. The influence of noncondensable gas is most marked for low vapor velocities and large gas concentrations. The nonsimilar character of the problem is especially evident near x = 0, where the connective behavior of the vapor boundary layer is highly position-dependent.
Local Film Thickness During Transient Voiding of a Liquid-Filled Channel
Authors: O¨zgu¨ M. R. , Chen J. C.
Published: November 2010

Using a recently developed method, measurements were obtained of local film thicknesses during transient voiding of a liquid-filled channel. The liquid film remaining on the channel walls was found to vary in thickness over a range of 0.015–0.15 times channel diameter. In a Lagrangian coordinate system, the film thickness at a fixed distance from the head of the void was found to increase with increasing void acceleration. In an Eulerian system, the film thickness at a fixed location on the channel wall was found to decrease with increasing acceleration, when measured at the same time after passage of the head of the void. In all cases, film thickness monotonically decreased with increasing distance from the head of the void. Complete film breakage (dryout) was not observed in these experiments. These experimental measurements of local film thicknesses during transient voiding conditions are pertinent to thermal analyses for reactor safety studies.
Radiation Heat Transfer Through Multiband Molecular Gases
Authors: Nelson D. A.
Published: November 2010

Exact characterization of radiation heat transfer through multiband molecular gases is obtained in some limits of considerable importance. An approximate procedure based upon these results is also suggested.
Conservative Anisotropic Scattering in a Planar Medium with Collimated Radiation
Authors: Buckius R. O. , Hwang D. C.
Published: November 2010

The directional hemispherical and bidirectional reflectance and transmittance are presented for a conservative anisotropic scattering medium. Collimated incident radiation and linear anisotropic scattering are considered so that the azimuthal dependence must be retained. The effects of optical thickness, anisotropic scattering, incident angle, polar angle, and azimuthal angle are presented in a closed-form approximate solution. Comparisons with exact solutions are also presented.
Predicted Effects of Tangential Slot Injection on Turbulent Boundary Layer Flow over a Wide Speed Range
Authors: Cary A. M. , Bushnell D. M. , Hefner J. N.
Published: November 2010

Paper describes a numerical calculation method using eddy viscosity/mixing length concepts for tangential slot injection (wall-wake) flows; application of the method over a wide range of flow conditions indicates increased accuracy compared to previous work. Predictions from the numerical code were in good agreement with experiment (velocity profile, skin friction, and effectiveness data) for low and high speed flows. To achieve improved accuracy, improvements in the turbulence modeling, compared to previous research, were necessary for the imbedded shear layer region in the near field and for the wall region near shear layer impingement. Anomalous behavior was noted for far field experimental velocity profiles in low speed flow when the slot-to-free stream velocity ratio was near one.
Friction and Lubrication Effects in Open Die Impact Forging
Authors: Cruff C. E. , Reynolds C. C.
Published: November 2010

A horizontal forging machine, Impacter, was used to determine coefficients of friction under different conditions of forging 1020 steel and 2014 T-4 aluminum. Short cylinders were open die forged with repeated blows and the reduction of height determined for one to eight blows. The area under a calculated forging force versus reduction curve was related to available energy in the impellers so that a theoretical reduction for each blow could be determined for different coefficients of friction.
An Investigation of “Diaphragm” Type Thrust Bearings—Part I: Experiment
Authors: Tieu A. K.
Published: November 2010

The performance of two types of hydrodynamic thrust bearings, namely the diaphragm tilting thrust pad and the diaphragm stepped thrust pad, is investigated experimentally under low- and high-speed conditions. The outlet film thickness and coefficient of friction of these diaphragm thrust pads are then correlated with computed results.
Design of Efficient Turbulent Thrust Bearings
Authors: Wilcock D. F.
Published: November 2010

Turbulence makes high speed conventionally designed bearings operate with higher power loss, high temperature rise, and lower oil flow than predicted. The objective of this paper is to show that the phenomenon of turbulence can be turned to the designer’s and operator’s advantage; and that turbulent thrust bearings can be designed to operate with lower power loss than conventional design would predict, while maintaining the same minimum film thickness and safe temperature rise.
Perturbation Solution of the 1-D Reynolds Equation With Slip Boundary Conditions
Authors: Sereny Aron , Castelli Vittorio
Published: November 2010

The method of matched asymptotic expansion is applied to obtain the pressure distribution and the load carrying capacity for an infinitely long slider bearing, operating under high-speed, low-height, with slip boundary conditions. The pressure distribution is easily applicable as the starting solution for the iterative numerical solution of Reynolds equation. Two examples given show extremely good correlation between this expansion and the numerical solution. It is shown that, for a tapered slider bearing with a bearing number above 100, the reduction in load because of slip is minimal and that, for a parabolic slider, there exists a certain unique bearing number for which the load carrying capacity is independent of the parabolic crown of the slider. It is shown that for a wide slider bearing with large bearing number, the effect of slip is on the order of 1/A.
Analysis of Dynamic Tilt Stiffness and Damping Coefficients of Externally Pressurized Porous Gas Journal Bearings
Authors: Rao N. S.
Published: November 2010

A theoretical estimate of dynamic characteristics in terms of stiffness and damping of an externally pressurized gas-lubricated porous journal under tilting mode of vibration is made. The governing nonlinear partial differential equations in the porous medium and in the bearing clearance are linearized using a first-order perturbation analysis. The tilt stiffness and damping are then determined from the solution of the resulting linear partial differential equations numerically. The effect of feeding parameter, supply pressure, porosity parameter, L/D ratio and eccentricity ratio on these two above characteristics is shown.
On the Dynamic Stability of Self-Aligning Journal Gas Bearings
Authors: Cohen M. J.
Published: November 2010

The report presents an investigation of the dynamic stability behaviour of self-aligning journal gas bearings when subjected to arbitrary small disturbances from an initial condition of operational equilibrium. The method is based on an approach similar to the nonlinear-ph solution of the author for the quasi-static loading case but the equations of motion of the journal are the linearized forms for small motion in the two degrees (translational) of freedom of the journal center. The stability domains for the infinite journal bearing are presented for the whole of the eccentricity (ε) and rotational speed (Λ) ranges for any given bearing geometry, in the shape of stability boundaries in that domain. It is shown that a given bearing will be stable within a corridor in the (ε, Λ) parametral domain having as its lower bound the so called “half-speed” whirl stability boundary and as its upper bound another whirling instability at a higher characteristic (relative) frequency, the instability occurs generally at the higher eccentricities and lower rotational speeds.
Surface Ribbing of a Thin Viscous Fluid Film Emerging From a Spreader or Roller
Authors: Fall C.
Published: November 2010

The thin film produced by the flow of a viscous fluid through a narrow gap between a spreader (or roller) and a flat plate is often subject to surface ribbing. A linear perturbation analysis, based upon lubrication theory, is used to examine the nature of this ribbed film and, specifically, to explain the large distances over which ribbing is observed to prevail. Taking into account the effects of both surface tension and gravity in smoothing out the film, the analysis predicts a characteristic distance from striated film-rupture to where a uniform film is formed.
International Trends in Engineering Design Education—A Partial View
Authors: Bar-Cohen A.
Published: November 2010

Approaches to engineering design education in several developing and developed nations are reviewed and found to suggest widespread recognition of the need for early and frequent student exposure to the pragmatic and often controlling aspects of mechanical system design. In this context, it appears that the undergraduate engineering program at most U.S. Universities may not contribute to the ability of engineering students to pursue successful careers in engineering innovation and design.
Mechanical Properties of Cast Carbon Steel in Heavy Sections
Authors: Banks W. C. , Skidmore K. F. , Schwartzbart H.
Published: November 2010

An extensive investigation of the mechanical properties of cast ASTM A216 steel WCB and WCC grades, as functions of composition, heat treatment and casting thickness is reported. Castings in section thicknesses ranging from 2 1/2 in. to 10 in. were produced from twenty-two commercial size heats by five different foundries. Tensile, Charpy-V-notch and metallographic results are discussed. The overall conclusion is that by exercising control over composition and heat treatment, cast carbon steel conforming to the requirements of ASTM A216 Grades WCB and WCC when tested at the quarter thickness point in well-fed sections up to 10 in. thick can be expected to meet the requirements of these specifications and those of Section III of the ASME Boiler and Pressure Vessel Code.
Finite Element Analysis of Perforated Plates Containing Triangular Penetration Patterns of 5 and 10 Percent Ligament Efficiency
Authors: Jones D. P.
Published: November 2010

Two- and three-dimensional finite element models were used to determine elastic stress distributions in plate ligaments for various in-plane, bending, and thermal loadings. Plates containing triangular penetration patterns of 5 and 10 percent ligament efficiency were analyzed as well as the example of a circular plate containing a single centrally placed hole subjected to step change in temperature on one surface. Detailed descriptions of boundary conditions are given with the results presented in terms of stresses important in tubesheet and vessel closure design considerations. Results show that the minimum ligament section of the perforated region need not be the critically stressed cross section as is currently assumed in the ASME Boiler and Pressure Vessel Code. Further, a thermal shock ΔT applied to the surface of a perforated region will result in a maximum peak stress of EαΔT/(1−ν) and may be significantly lower than the thermal skin stress calculated by the ASME Code procedures.