bluuebunny/crossref_metadata_2025 huggingface dataset:
Effect of Variation in Poisson’s Ratio on Plastic Tensile Instability
Authors: Bert C. W. , Mills E. J. , Hyler W. S.
Published: November 2011

Using the concept of the tensile-instability mechanism which determines the ultimate strength of most of the ductile materials under uniaxial or biaxial tension conditions, two new analyses are carried out. In these are considered an effect previously neglected: Variation of Poisson’s ratio (based on total strain) with strain in the plastic range. One analysis treats a uniaxial tensile specimen, and the predicted results are generally in better agreement with experimental values for seven alloys of aerospace structural importance than the results of classical theory, in which Poisson’s ratio is assumed to remain constant at a value of 1/2 in the plastic range. The other considers a thin-walled spherical shell subject to internal pressure, and the predicted result is again closer to the experimental value than that predicted by classical theory.
Rotating Principal Stress Axes in High-Cycle Fatigue
Authors: Miller W. R. , Ohji K. , Marin J.
Published: November 2011

A new modified octahedral shear stress failure theory for high-cycle fatigue has been developed. This theory considers rotating principal stress axes and nonsynchronous stresses. This theory was then compared to the commonly used octahedral shear stress theory using data from the literature. The new theory was found to be significantly better in predicting failures.
Elastic Constants of Magnesium Thorium Alloy
Authors: Asay J. R.
Published: November 2011

The longitudinal and shear wave velocities in a polycrystalline sample of magnesium thorium alloy were measured by a pulse transmission technique as a function of temperature. Temperatures ranged from 25 C to about 350 deg C for longitudinal wave measurements and to about 220 deg C for shear measurements. The resulting velocity data were used to calculate various elastic properties of the material, including Young’s modulus, shear modulus, bulk modulus, and Poisson’s ratio. The resulting least squares fits for these data are: Longitudinal velocity, cl = 5.749 − 3.987 × 10−4T − 1.139 × 10−6T2mm/μsec; shear velocity, ct = 3.108 − 1.421 × 10−4T − 2.588 × 10−6T2mm/μsec; bulk modulus, B = 3.576 × 10″ − 2.744 × 107T + 1.187 × 105T2 dynes/cm2; Young’s modulus, E = 4.435 × 10″ − 1.415 × 107T = 6.037 × 105T2 dynes/cm2; shear modulus, G = 1.716 × 10″ − 7.994 × 106T − 2.619 × 105T2 dynes/cm2; Poisson’s ratio, σ = 0.293 − 6.459 × 10−6T + 3.392 × 10−7T2.
Short-Time Tensile and Long-Time Creep-Rupture Properties of the HK-40 Alloy and Type 310 Stainless Steel at Temperatures to 2000 F
Authors: VanEcho J. A. , Roach D. B. , Hall A. M.
Published: November 2011

The short-time tensile properties of the A CI Type HK-40 cast heat-resistant alloy and AISI Type 310 wrought stainless steel were investigated from room temperature to 2000 F. The creep-rupture properties of the HK-40 alloy were studied in the range of 1400 to 2000 F for times long enough to permit extrapolation to 100,000 hr. In addition, the creep-rupture properties of Type 310 were investigated at 1800 to 2000 F, and observations were made of the microstructural changes that occurred in the two materials during creep exposure. The Type 310 material tended to have a higher yield strength and ultimate tensile strength at moderate temperatures than the HK-40; however, from 1200 to 2000 F, the HK-40 was the stronger. The Type 310 was more ductile at all temperatures. The HK-40 displayed about twice the rupture strength of the Type 310 at each test temperature. On the basis of comparable minimum creep rates, the HK-40 showed five to six times the strength of the Type 310 at the same temperature. During exposure at the lower temperatures, chromium carbides precipitated in finely dispersed form in the matrix of the HK-40; isolated islands of sigma phase also tended to form. At high temperatures, the primary eutectic carbides in the HK-40 alloy tended to spheroidize; and both materials absorbed nitrogen from the atmosphere, needles of chromium nitride forming in the matrix.
A Study of the Law of Crack Propagation
Authors: Yang C. T.
Published: November 2011

A general form of the mathematical function in the crack-propagation law for specimens of both infinite and finite widths was determined by means of dimensional analysis. The exact function of the latter type was then determined by experiments. It was found that the general equation of the power law holds for specimens of finite width for three metals: Cold-rolled types 301 and 310 stainless-steel sheet and 2014-T6 aluminum-alloy sheet tested at 78° F and low cyclic load rates. The indices n of the power-law equation for the two stainless steels were found to be different from that of the aluminum alloy. The valuable application of the power-law equation to design work is mentioned.
Analytical Interpretation of Brinell Hardness
Authors: Ku T. C. , So S. S.
Published: November 2011

Hardness, an experimentally determined quantity, cannot be related conveniently to other mechanical properties of a material. This note is aimed at deriving a better interpretation of the Brinell hardness in terms of some common mechanical properties such as Young’s modulus, Poisson’s ratio, and the yield point in shear. The Brinell hardness test can be idealized to that of a rigid frictionless sphere indenting a semi-infinite solid under a given load. Under the condition of Brinell hardness test, the maximum shear stress at any point in the elastic region along the axis of symmetry can be obtained from Terazawa’s solution. The Brinell hardness can then be interpreted as a measurement of the depth along the axis of symmetry where the maximum shear stress is equal to a given fraction of the yield point in shear, or the maximum shear stress expressed as a fraction of the yield point in shear at a given depth.
The Metallurgy of Alloy 718
Authors: Hall R. C.
Published: November 2011

The nickel-base wrought Alloy 718 was designed for high strength at elevated temperatures, that is, near 1200 deg F; the alloy also has exceptional mechanical properties at cryogenic temperatures. This paper reviews the metallurgy of Alloy 718. The effect of variations in composition, microstructure, and heat-treatment are correlated to mechanical properties; the relationships among these factors are complex and are described where possible.
A Study of Diffusion in Turbulent Pipe Flow
Authors: Evans G. V.
Published: November 2011

The paper describes a numerical solution to the problem of diffusion of a dye injected into turbulent pipe flow. Theoretical concentration distributions obtained assuming a uniform distribution of radial diffusivity coefficient and those obtained assuming a parabolic radial distribution of diffusivity are compared with measured concentration profiles at various distances downstream of injection. The effect of flow and injection conditions on the length of straight pipe required for complete mixing of the dye has been found from the theoretical results.
Mechanical Potential Drops at a Fluid Branch
Authors: Katz S.
Published: November 2011

Separating and mixing steady flows are analyzed at a 90 deg equal area branch (TEE junction). An arbitrary assumption is made linking secondary flow forces to the turning momentum through an experimental constant. This constant is evaluated from the data of Vogel on TEE junctions and the data of Barton on pipe laterals. Expressions are derived for the mechanical potential drops at the branch. These expressions are then used to solve a simple branch flow problem.
Reducing Water Tunnel Turbulence by Means of a Honeycomb
Authors: Lumley J. L. , McMahon J. F.
Published: November 2011

The effect of a honeycomb on a turbulent stream and the turbluence produced by the honeycomb itself are analyzed. The first analysis is similar to the classical one for screens except that: (a) It is assumed that the cell flow is fully developed so that transverse fluctuations are completely annihilated; and (b) both the inertial effect of the mass of fluid in the cell and the effect of frictional resistance are included. The second analysis includes: (a) The turbulence created in the cell flow if the cell flow is turbulent; and (b) the turbulence resulting from the breakup of the wake behind each cell.
A Numerical Study of the Flow Due to a Rotating Disk With a Center Sink
Authors: Richards C. G. , Graebel W. P.
Published: November 2011

The flow due to a rotating disk in an infinite fluid with a sink located at the center of the disk is studied numerically. The problem is solved as an unsteady flow problem by an implicit alternating-direction technique and the method of successive over-relaxation. Solutions are computed for various values of a single parameter, β=Q02πων3, which contains the sink strength (Q0) and the disk speed (ω). The solutions converge to steady state values, and the values obtained for large radii are compared with an earlier solution for the case of the disk without the sink, with good agreement. It is found that a dividing stream surface is present which separates the sink flow from the centrifugal flow. The numerical results were limited to values of β below 12 in order to keep the computation time within reasonable limits.
Turbulent Flow of Dilute Aqueous Polymer Solutions
Authors: Goren Y. , Norbury J. F.
Published: November 2011

This paper summarizes some of the research into the effect of polymer additives on turbulent shear flow, which was conducted at the University of Liverpool between October, 1964, and October, 1966. The paper contains a brief description of the research together with a summary of the principal results and conclusions. The present work was devoted to a detailed examination of the mechanism of a particular flow by gathering information on friction drag, velocity distribution, concentration distribution, and correlation with Reynolds number and polymer concentration level. The particular flow chosen was the fully developed turbulent flow in a 2-in-dia pipe of Polyox WSR-301 solutions. A maximum drag reduction of 71 percent was obtained at a Reynolds number of 1.5 × 105 for solutions having polymer concentration of 10 weight parts per million. The drag reduction effect occurred only above some “critical” Reynolds number which was independent of concentration. The polymer additives were found to influence the flow in the neighborhood of a solid boundary. In this zone of the flow, the eddy viscosity was found to be much lower than that of water. In the absence of a boundary, as in free jet flow, the polymer additives had no effect on the flow characteristics. The experiments showed for the first time that the polymer molecules were uniformly distributed across the pipe diameter under all turbulent flow conditions investigated. A method of determining polymer concentration was devised for this purpose.
Prediction of the Low Cycle Fatigue Life of Pressure Vessels
Authors: Pickett A. G. , Grigory S. C.
Published: November 2011

The bases for ASME Boiler and Pressure Vessel Code, Section III, fatigue evaluation procedures, the fracture mechanics approach to fatigue life analysis, and the notch stress analysis method are reviewed. Fatigue life predictions are compared with the results of materials, model, and full size pressure vessel tests performed for PVRC and AEC. These tests were made in response to the research objectives established by ASME Special Committee to Review Code Stress Basis in 1958. A proposed design procedure based on the notch stress analysis method and experimental results is presented.
The Effect of Mean Stress on Fatigue Crack Propagation in Plates Under Extension and Bending
Authors: Roberts R. , Erdogan F.
Published: November 2011

An earlier study of fatigue crack propagation in thin plates under fluctuating plane extension and cylindrical bending is extended to include the effect of nonzero mean stress. The theoretical considerations are applied to existing data and to new data obtained from 2024-T3 bare and clad aluminum specimens subjected to fully reversed and nonsymmetric bending loads. For the ranges studied, the agreement between the data and the model developed seems to be very good.
Yankee Reactor Pressure Vessel Surveillance: Notch Ductility Performance of Vessel Steel and Maximum Service Fluence Determined From Exposure During Cores II, III, and IV
Authors: Serpan C. Z. , Hawthorne J. R.
Published: November 2011

Charpy V-notch specimens representative of one of the several heats of A302-B steel forming the Yankee reactor pressure vessel, and irradiated as part of the Yankee surveillance program, have been tested by the Naval Research Laboratory. Specimens of this particular heat, irradiated in near-core (accelerated) as well as in vessel wall locations, showed more embrittlement than did specimens of a reference steel heat of the same nominal A 302-B composition irradiated simultaneously in the same surveillance capsules. Those specimens from both the Yankee vessel heat and the reference heat irradiated at the vessel wall location depicted a higher damage rate than that for the accelerated location. The cause of this difference in embrittlement response could not be attributed to an effect of cyclic, service irradiation temperatures, but could be traced to a qualitative relationship of thermal to fast (>1 Mev) neutron fluxes. This ratio was in excess of about 9:1 at the vessel wall location versus a ratio less than about 9:1 for the accelerated location. The computation of a maximum service fluence of 1.46 × 1019 n/cm2 >0.5 Mev was made possible by establishment of the neutron spectrum at the reactor vessel wall using computer calculations. The maximum fluence derived by this technique compared favorably with another value given by an independently-developed calculated neutron spectrum. The NRL computed service fluence in concert with the embrittlement data projects a maximum transition temperature increase of 265 deg F, a level of embrittlement considered acceptable for the Yankee reactor vessel after thirty fuel cycles of operation at 600 MW(t).
An Electron Fractographic Study of Spalls Formed in Rolling Contact
Authors: Borgese S.
Published: November 2011

A technique is described for making fractographs of spalls formed in bearings during rolling contact. Results are given which illustrate the usefulness of the method in identifying the fracture modes encountered in spalls. Regions of fatigue striations, cleavage, dimpled rupture, and quasi-cleavage were identified in each spall examined. All of the fractures observed were transgranular with no evidence of any intergranular fractures. In a spall which initiated at an identifiable defect (grinding furrow), the region at the initiation point failed by a fatigue mechanism. The final stages of fracture were by cleavage and quasi-cleavage.
Transmission of Fluid Power by Pulsating-Flow (P-F) Concept in Hydraulic Systems
Authors: Weng Cheng-Kuo
Published: November 2011

Theoretical and experimental investigations have been made on fluid-power transmission in hydraulic systems by pulsating flow. In particular, the system efficiency and the viscosity effect on the dynamic response of pulsating flow in the fluid line have been studied. Test results on the fluid-line dynamic response and on the system efficiency that obtained from the line-loss test setup and the miniaturized P-F hydraulic system setup, respectively, are presented.
Sequential Estimation of States and Parameters in Noisy Nonlinear Dynamical Systems
Authors: Detchmendy D. M. , Sridhar R.
Published: November 2011

The problem considered is the sequential estimation of states and parameters in noisy nonlinear systems. The class of systems considered is those in which the dynamical behavior is described by an ordinary differential equation. No statistical assumptions are required concerning the nature of the unknown inputs to the system or the measurement errors on the output. For estimation purposes, a least-squares criterion is used. The new feature of the approach presented is that a sequential least-squares estimator is obtained for the class of problems considered. This estimator could be implemented in real time. Experimental results from several examples indicate that the proposed estimation scheme is feasible.
A Study of Fluid Squeeze-Film Damping
Authors: Griffin W. S. , Richardson H. H. , Yamanami S.
Published: November 2011

The fluid squeeze-film produced by relative axial or tilting motion of two closely spaced plates provides viscous damping action over certain ranges of operation. When gas is the working fluid, a damper can be realized which is operable over a wide frequency range in the presence of extreme temperatures and intense radiation. A linearized analysis and approximate design equations, verified by a limited experimental program, are presented for several useful damper configurations.
A Nonlinear Filter for Independent Gain and Phase (With Applications)
Authors: Foster W. C. , Gieseking D. L. , Waymeyer W. K.
Published: November 2011

Compensation of control systems by means of linear filters is a basic and well-known art. However, the limitations of linear compensation are also well known. In particular, the interdependence of the phase and gain characteristics of linear filters is always in conflict with the desires of the control-system designer. For example, it is impossible to introduce attenuation into a system without introducing undesirable phase lag as well. The development of a split-path nonlinear filter (SPAN filter) concept promises to yield a practical device which has independent phase and gain characteristics. These characteristics are independent of input signal amplitude. This filter can, therefore, have desirable characteristics which are unattainable with conventional linear filters. The design of the nonlinear filter to meet a desired gain-phase, describing-function specification is simplified by results given in the paper. Analysis and simulation of three sample problems has shown that a great deal of flexibility is available with this nonlinear filter. It is possible to obtain phase lead and amplitude attenuation by a proper choice of linear filtering in the two channels. Analog-computer simulation has verified the analytical work with respect to stability margins, and provided transient-response data, in the absence of analytical methods.
An Extension of the Describing-Function Method
Authors: Sarti Eugenio , Takahashi Yasundo
Published: November 2011

The use of the describing-function method has been generally limited to systems with nonlinearities which can be combined in a block diagram of a feedback control system which is represented by a scalar variable. This paper deals with an extension of the method to some autonomous systems with more than one nonlinearity. The paper also shows that nonlinear systems can have hypersurfaces or manifolds in state space which divide regions of different stability characteristics. Each of these manifolds can be regarded as a boundary element of a family of surfaces related to a Lyapunov function. The describing-function method is applied in such a way that the hypersurfaces are approximated by a quadratic form. Two cases in an example, for which data obtained by analog computer and describing function approximations are compared, show that the amount of error caused by the approximation can be acceptably small, particularly in the subspace of the state space in which a system exhibits nonlinearities.
Electron Microscopy of Stress-Induced Structural Alterations Near Inclusions in Bearing Steels
Authors: O’Brien John L. , King Alwyn H.
Published: November 2011

The white-etching structural alteration occurring around nonmetallic inclusions in cyclically stressed bearing steels has been studied by transmission-electron microscopy. In order to use this method, thin foils have been prepared with an edge running through the alteration. It has been found that the alteration is due to the formation of 0.05 to 0.1-micron cells in ferrite. The cell formation is similar to that seen in fatigued iron except for the small cell size of the deformed steel. Evidence is also given that deformation causes breakup of the carbides produced on the tempering of steel prior to deformation.
Lubricant Effects on Fatigue in a Stationary Concentrated Contact Under Vibratory Loading
Authors: Burton R. A. , Russell J. A.
Published: November 2011

Contact fatigue, brinnelling, and erosion are reported, for a stationary ball-on-flat contact, subjected to oscillatory normal load. Damage was least in the absence of lubricant, and greatest with a diester lubricant. Low-viscosity mineral oil was less severe in its effects than was a high-viscosity mineral oil. In those cases where damage was least, it could be attributed to a process of fatigue spalling. In those cases where it was severe, other processes such as fretting could be postulated, but fatigue still appeared to be the favored cause.
Creep-Rupture Properties of Centrifugally Cast 1 1/4 Cr-1/2 Mo Alloy Steel Pipe
Authors: Dotson C. L. , Donoho C. K.
Published: November 2011

The creep-rupture properties of tensile specimens made from 1 1/4 Cr-1/2 Mo centrifugally cast alloy steel pipe, conforming to ASTM A426-CP11, were evaluated at 1000, 1100, and 1200 F. At 1000 F, the pipe was evaluated in two normalized-and-tempered conditions, and at 1100 and 1200 F, in one normalized-and-tempered condition. Specimens were loaded to produce rupture in time ranging from less than 100 to about 2000 hr for determination of the minimum creep rate and the creep-rupture strength, and at lower loads to obtain additional minimum creep rate data. The rupture strength and minimum creep rate of the centrifugally cast pipe were compared to similar properties for the alloy in statically cast and wrought forms. Stresses required to produce a minimum creep rate of 10−5 percent/hr and rupture in 100,000 hr were compared to allowable design stresses specified by the ASME Boiler and Pressure Vessel Code and American Standards Association Specifications B31.1, Pressure Piping, and B31.3, Petroleum Refinery Piping. In both heat-treated conditions evaluated, the minimum creep rate of the pipe compared favorably with published data for the alloy in noncentrifugally cast forms and with the allowable stresses set by the ASME and ASA codes.
Long-Term Rupture Strength of Alloys and Plastics From Tensile Strength at Elevated Temperatures
Authors: Goldfein Solomon
Published: November 2011

This paper covers an investigation to determine if the long-term, tensile stress-rupture strength of alloys could be calculated from the results of static tensile-strength tests at elevated temperatures. Twenty-one alloys were investigated. A second-order form of a mechanical-chemical equation of state was used to draw master rupture curves from both long-term rupture and tensile-strength data. It is concluded that the long-term strength of an alloy can be computed from a knowledge of its tensile strength at elevated temperatures, prior history, chemical composition, and mode of failure.
Fracture Toughness Determinations of A-302B and Ni-Mo-V Steels With Various Size Specimens
Authors: Mowbray D. F. , Brothers A. J. , Yukawa S.
Published: November 2011

Fracture tests were conducted on three steels obtained from heavy-section pieces over a range of test temperatures using single-edge notched (SEN) specimens under tensile loading and notched-bar (NB) specimens in bending. The SEN tests were performed on specimens 0.125 and 0.4 in. thick plus a few specimens 0.020 in. thick. In the NB series Charpy-sized specimens (0.4 in. square) were tested at various temperatures with additional tests on smaller and larger specimens up to 6 in. square at selected temperatures. All specimens were provided with a fatigue precrack at the tip of the notch. The tests were conducted to determine the capability of various size specimens for providing valid plane-strain fracture toughness (GIc or KIc) values at various temperatures for these steels. At very low temperatures all specimens gave similar KIc values. With increasing temperature, KIc values obtained from the larger specimens remained relatively constant and then increased rapidly. At higher temperatures within this range, valid KIc values could not be measured with small specimens. Two possible methods of estimating KIc at these temperatures from small specimen data are discussed. One of these involves a correlation between fracture toughness and shear-lip thickness. The second makes use of a relation between bend angle, crack-opening-displacement, and fracture toughness. The test results are analyzed to show that both methods can be very useful.
Successive Generation of Chebychev Approximation Solution
Authors: Aoki Masanao
Published: November 2011

Problems of filtering and prediction, which are significant parts of many control problems, can be treated as those of data-fitting, usually by the method of least squares. Then, the least-square data-fitting is essentially the process by which a best approximate solution is obtained, in the sense of least squares of deviation, of a system of overdetermined linear equations. The same problem is known as the Chebychev approximation problem when the absolute deviation is used as the measure of goodness of approximation. The paper gives a recursive algorithm for the Chebychev approximation problem by modifying a nonrecursive algorithm of Zuhovickii and Stiefel. An example of estimation processes is given in which the Chebychev approximation method gives an estimate whose variance is smaller than that of the least square estimate.
Energy Storage in Metals at High Pressures
Authors: Bailey N. P.
Published: November 2011

An equation of state of the form u/pv = muk is developed where u is internal energy, p is pressure, v is specific volume, and m and k are constants over wide ranges of the variables. It is shown to be valid for both impact and static pressures and also to describe other solids, liquids, and gases.
Driving Torques in a Theoretical Model of a Turbine Meter
Authors: Rubin M. , Miller R. W. , Fox W. G.
Published: November 2011

A theoretical model of a turbine meter, incorporating fewer restrictions than previously available models, is analyzed from both the momentum and airfoil viewpoints. The two resulting equations for driving torque are explored in a series of graphs and discussed. Emphasis is on design implications. Of particular interest are the criteria, resulting from this analysis, for determining the conditions necessary for full fluid guidance.
Use of Hydrogen Bubbles for Quantitative Determination of Time-Dependent Velocity Fields in Low-Speed Water Flows
Authors: Schraub F. A. , Kline S. J. , Henry J. , Runstadler P. W. , Littell A.
Published: November 2011

Improved flow-visualization methods based on the hydrogen-bubble technique are described. Use of “combined-time-streak markers” allows quantitative measurement of the instantaneous velocity field in a plane as a function of time in low-speed water flows. Adaptation to a great variety of situations using different probe techniques is possible. Disturbance to the flow is very small. Adequate accuracy is obtainable. The method offers the advantage of simultaneous visual observation of the flow structure and quantitative measurement of velocity over a finite region. It also allows some types of measurement not previously possible. Limitations of the method include its restriction to low-speed water flows and the observation of fluctuations only at low frequencies. Practical difficulties occur due to probe frangibility and problems of obtaining uniform bubble production. Part 1 describes the underlying concepts, summarizes the history of the method and describes operating experience to date at Educational Services, Incorporated, and Stanford University. Part 2 is a detailed analysis of the uncertainties in velocity measurements using combined-time-streak markers formed by hydrogen bubbles.
The Reflection of Waterhammer Pressure Waves From Minor Losses
Authors: Contractor D. N.
Published: November 2011

This paper deals with the reflection produced when a waterhammer pressure wave encounters any device that produces a sudden energy loss such as an orifice, a valve, or an elbow. The classical wave theory is used to determine the magnitudes of the reflected and the transmitted waves. The waterhammer equations, with the friction term included, are solved by the method of characteristics. The conditions at a minor loss are studied as a boundary condition to these equations. Agreement between theoretical and experimental pressure-time diagrams is sufficient to validate the theory.
Dynamically Loaded Journal Bearings: Mobility Method of Solution
Authors: Booker J. F.
Published: November 2011

An approach is presented for simplified analytical, graphical, and numerical solutions to extremely general problems of dynamically loaded bearings. A series of examples illustrates the application of the method to problems of varying complexity.
On Hydrodynamic Instability of Gas-Lubricated Journal Bearings
Authors: Constantinescu V. N.
Published: November 2011

Paper starts with a study of static stability response of gas-lubricated bearing, followed by a general small perturbations theory of the dynamic stability of journal bearings. Then the pressure equation for bearings subjected to variable forces and velocities is analyzed, by pointing out the existence of a limiting solution which can occur both for high speeds or for high frequency of the bearing eccentricity. At the same time the squeeze effect can be strongly altered by the lubricant compressibility so that, for motions with high tangential speeds or with high frequencies, the pressures depend only on the thickness h and not on the derivative with respect to time h˙ as is the case of incompressible films. Finally, the analysis of the stability conditions reveals that bearings operating at low numbers H are unstable according to the small perturbations theory. The same situation occurs to the bearings operating with small eccentricity ratios, for any number H. The frequency of undamped oscillations is proportional to the shaft angular speed ω for low numbers H but tends to a bounded value ω0* for high number H. Quasi-resonant conditions may also occur when the number H is increasing, a fact which allows the deduction of a simple half-empirical stability condition.
The Measurement of Surface Temperatures on Gear Teeth
Authors: Niemann G. , Lechner G.
Published: November 2011

The flash-temperature theory plays an important part in the attempt to explain the scoring phenomenon of gears. Purpose of the investigations was to measure the surface temperatures of meshing gears. Results are presented as to the following influences on the surface temperatures: Tooth profile, loading, pitch-line velocity, surface roughness, synthetic lubricant and face width. The results are compared with the flash-temperature equation according to Blok.
On the Mechanism of Contact Between Metal Surfaces—The Penetrating Depth and the Average Clearance
Authors: Tsukizoe Tadasu , Hisakado Terumasa
Published: November 2011

The analysis of the mechanism of air leakage through the interstices between metal surfaces in contact or of the mechanism of thermal resistance between them is dependent on the average clearance between opposite surfaces or on the distribution of the real contact area; i.e., the mechanism of contact. Assuming that the distribution curve obtained from the profile curve of the surface has a normal distribution, the relation between the applied load and the average clearance or the penetrating depth, i.e., the distance through which the one surface moves into the other surface, is obtained theoretically. A comparison of calculated values based on this theory with experimental data shows good agreement.
A Linearized Turbulent Lubrication Theory
Authors: Ng Chung-Wah , Pan C. H. T.
Published: November 2011

The “law of wall” for turbulent shear flows has been adapted to analyze turbulent lubrication. This new approach takes into account many well-established facts concerning turbulent shear flows. Isotropy of turbulent momentum transport (eddy viscosity) is assumed in treating nonplanar mean flows. A linearized version of the governing differential equation is established. Sample results agree well with available experimental data.
Surface Displacement of a Convective Elastic Half-Space Under an Arbitrarily Distributed Fast-Moving Heat Source
Authors: Ling F. F. , Mow V. C.
Published: November 2011

A solution of the normal displacement of the elastic half-space under an arbitrarily distributed fast-moving heat source of constant velocity within the two-dimensional quasi-static, uncoupled thermoelasticity theory is presented. The surface of the half-space is allowed to dissipate heat by convection. Moreover, an example associated with the problem of elastohydrodynamics is given.
Magnetohydrodynamic Squeeze Film Bearings
Authors: Dodge F. T. , Osterle J. F. , Rouleau W. T.
Published: November 2011

A theoretical analysis is given for squeeze film bearings which use an electrically conducting fluid, such as a liquid metal, as the lubricant and which are in the presence of a magnetic field. Electrical energy is added to the film by an exterior source. By considering infinitely long rectangular plates, the fluid film thickness is determined as a function of time, with the applied magnetic and electric fields as parameters. It is shown that the squeeze action is altered significantly when the electric field is symmetrical about the center of the bearing, and results are presented for various values of the Hartmann number.
General Formulation of a Perturbation Theory for Unsteady Cavity Flows
Authors: Wang D. P. , Wu T. Yao-Tsu
Published: November 2011

The problem of a two-dimensional cavity flow of an ideal fluid with small unsteady disturbances in a gravity free field is considered. By regarding the unsteady motion as a small-perturbation of an established steady cavity flow, a fundamental formulation of the problem is presented. It is shown that the unsteady disturbance generates a surface wave propagating downstream along the free cavity boundary, much in the same way as the classical gravity waves in water, only with the centrifugal acceleration owing to the curvature of the streamlines in the basic flow playing the role of an equivalent gravity effect. As a particularly simple example, the surface waves in a hollow potential vortex flow is calculated using the present theory.
Slip Flow in Rectangular and Annular Ducts
Authors: Ebert W. A. , Sparrow E. M.
Published: November 2011

An analysis has been performed to determine the velocity and pressure-drop characteristics of moderately rarefied gas flows in rectangular and annular ducts. The density level is such that a velocity slip may occur at the duct walls. In general, it is found that the effect of slip is to flatten the velocity distribution relative to that for a continuum flow; furthermore, the axial pressure gradient is diminished under slip-flow conditions. The conditions characterizing the onset of the slip regime have been determined on the basis of a 2 percent reduction in friction factor relative to the continuum value. For all the geometries studied here, the onset of slip occurred at a Knudsen number of 0.003. The effect of compressibility on the axial pressure drop was also investigated. It was found that compressibility increases the pressure drop primarily through an increase in viscous shear rather than through an increase in momentum flux.
The Theory of the Infinitely Wide, Perfectly Flexible, Self-Acting Foil Bearing
Authors: Eshel A. , Elrod H. G.
Published: November 2011

The differential equations applicable to the film thickness beneath an infinitely wide, perfectly flexible self-acting tape are derived in this paper. Accurate numerical solutions are obtained for the film thickness in both the entrance and exit regions. These solutions have general applicability to situations where the entrance and exit regions are separated by a third region of uniform thickness.
Stress-Rupture of Metals Under Increasing Stress
Authors: Rowe G. H. , Meck H. R.
Published: November 2011

The prediction of rupture life of several high temperature alloys (Hastelloy X, Type 316 stainless steel, Cb-1 Zr) was investigated analytically and experimentally for the case of linearly increasing stress.
Plane-Strain Fracture Toughness of High-Strength Aluminum Alloys
Authors: Carman C. M. , Armiento D. F. , Markus H.
Published: November 2011

The plane-strain fracture toughness of precipitation-hardening aluminum alloys of 7000 and 2000 series and a strain-hardening alloy 5456 have been determined at both room temperature and −320 F using circumferentially notched rounds. These results show that the plane-strain fracture toughness is an inverse function of the yield strength and that at equivalent yield-strength levels the 7000 series of alloys is tougher than the 2000 series of alloys. Plane strain-fracture toughness values were determined using “pop-in” technique employing both the center crack and single-edge-notch specimens. Comparable values were obtained in all examples tested. The effects of impurity elements, iron and silicon, on the fracture toughness of 7075-T6 aluminum alloy were investigated using a special low iron-and-silicon melt of 7075-T6 material. Reduction of these impurity elements resulted in a 30 to 45 percent upgrading of the plane-strain fracture toughness of this alloy. These data have been interpreted in terms of the process zone size, dT, using electron microfractography as an indication of this parameter. The plane strain-fracture toughness values have been used to calculate the breaking stress of part-through-cracked panel. These calculations have been confirmed experimentally for two alloys. Such data have direct applicability in the design of structures.
Resonance in Bersimis No. 2 Piping System
Authors: Wylie E. B. , Streeter V. L.
Published: November 2011

A condition of resonance in a large hydroelectric development is analyzed and the reasons the plant vibrated at selected frequencies and with definite pressure and discharge amplitudes are explained. The impedance theory is used in the analysis. The complete system is programmed for solution on the digital computer using the method of characteristics and the resonating conditions are reproduced as they actually occurred.
Pressure Peaks in the Hydraulic Actuator
Authors: McCloy D.
Published: November 2011

Results are presented of theoretical and experimental studies of the pressure peaks occurring in valve-controlled hydraulic actuators operated under severe loading conditions. Oil compressibility is shown to reduce the magnitude of these peaks. Valve overlap has the opposite effect. The possibilities of fatigue failure and cavitation damage in the actuator are discussed. The two different modes of cavity formation which occur when the valve is oscillated sinusoidally are discussed in detail.
Resonance in Pressurized Piping Systems
Authors: Wylie E. B.
Published: November 2011

The primary objective of this paper is to present a method of determining the resonant characteristics of a number of practical hydraulic systems. Distributed parameters are used to describe the system with the concept of hydraulic impedance being used to determine the frequency response. The investigation shows that the impedance approach is a valid, practical method of evaluating the resonant characteristics of complex systems without the introduction of many simplifying assumptions in the system geometry.
An Experimental Study of Accelerated Cavitation Induced by Ultrasonics
Authors: Numachi F.
Published: November 2011

With a view to clarifying cavitation phenomena induced by ultrasonic waves, utilized recently in erosion tests, the frequency spectrum of the waves caused by cavitation was obtained, and the pattern of air bubbles produced were observed by high-speed photography. Some considerations also are given in the present report on the amount and form of erosion caused by cavitation.
On the Separation, Reattachment, and Redevelopment of Incompressible Turbulent Shear Flow
Authors: Mueller T. J. , Korst H. H. , Chow W. L.
Published: November 2011

An experimental and theoretical investigation is presented which describes the character of the mean motion and the structure of turbulence for the separation, reattachment, and redevelopment of the incompressible turbulent shear flow downstream of a single step-type roughness element. For the redeveloping turbulent boundary layer downstream of reattachment, it is shown that the mean velocity profiles constitute a one-parameter family and that as far as the shape parameters are concerned, this one-parameter family is essentially the same as for a boundary layer developing toward separation. This similarity between developing (toward separation) and redeveloping (after reattachment) turbulent shear layers is utilized to establish an integral method for calculating the redeveloping turbulent boundary layer at essentially zero pressure gradient.
A Visual and Photographic Study of the Inception of Vaporization in Adiabatic Flow
Authors: Mikol E. P. , Dudley J. C.
Published: November 2011

Data and observations obtained during the study of two-phase flow phenomena for refrigerants flowing in small bore copper and glass tubes have been examined for their significance to the cavitation. Visual and photographic observations have been made of the inception of vaporization and of the movement of the point of inception as operating conditions are varied. Liquid tension has been deduced as occurring in these tests. Liquid tension and cavitation index data are presented. The experimental method is recommended as a means for studying many aspects of the phenomenon of cavitation.
The Hydrostatic Gas Journal Bearing With Journal Rotation and Vibration
Authors: Lund J. W.
Published: November 2011

This paper analyzes the load-carrying capacity of the externally pressurized gas journal bearing, including the effect of journal rotation and vibration. The analysis assumes small eccentricity ratio and small vibration amplitude such that a first-order perturbation solution is obtained. The gas is fed to the bearing through orifice-restricted feeding holes around the circumference in one or two feeding planes. The number of feeding holes is sufficiently large to permit treating the feeding planes as line sources. Results are given for the load-carrying capacity and the attitude angle.
Precise Power Control Utilizing a New Actuator Concept Embodying All-Mechanical Power Flow
Authors: Harned J. L. , Miller K. M. , Szlaga E. V. , Sudhindranath P.
Published: November 2011

Performance of a servomechanism that provides accurate, continuous control of mechanical power is fundamentally governed by the actuator used to meter power to the load. These actuators, when used in exacting control applications, tend to be complex, expensive, and critical. This paper describes a mechanical servoactuator concept based on the toric-transmission principle that has the potential of providing precise power control in a relatively simple and rugged package. Actuator kinematic principles are explained and equations that describe these relationships are presented to illustrate both steady-state and dynamic performance characteristics. Closed-loop control techniques are discussed with specific emphasis on the load-acceleration control feature inherent with this actuator concept. Experimental performance data obtained from testing a 1-hp prototype model operated as a velocity servo are presented. Static velocity control accuracy of ±0.1 percent is readily obtained; transient-response times vary from 20 to 40 milliseconds depending on signal amplitude and load conditions.
The Response of Nonlinear Closed-Loop Systems to Random Inputs
Authors: Gibson J. E. , Sridhar R.
Published: November 2011

A dual-input describing function (DIDF) is derived for sine waves and Guassian noise. The derivation follows the correlation method used in [1]. In this paper only single-valued nonlinearities are discussed but extension to multivalued nonlinear elements appears possible. The DIDF is used to investigate the stability and closed-loop response of nonlinear systems excited by random noise. Previous investigations have provided only for the random component at the input to the nonlinear element. It is shown that previous work is invalid insofar as it neglects the possibility of oscillations in the nonautonomous system if the autonomous system is stable and vice versa. Two examples are presented which show (i) the necessity of the DIDF approach for systems which are stable without input, and (ii) the possibility of successfully obtaining stable response to certain classes of inputs with systems which appear unstable without inputs. The present investigation is an extension of the authors’ previous work on the stability and closed-loop response of nonlinear systems excited by sinusoidal inputs [2].
A New Method of Locating the Maximum Point of an Arbitrary Multipeak Curve in the Presence of Noise
Authors: Kushner H. J.
Published: November 2011

A versatile and practical method of searching a parameter space is presented. Theoretical and experimental results illustrate the usefulness of the method for such problems as the experimental optimization of the performance of a system with a very general multipeak performance function when the only available information is noise-distributed samples of the function. At present, its usefulness is restricted to optimization with respect to one system parameter. The observations are taken sequentially; but, as opposed to the gradient method, the observation may be located anywhere on the parameter interval. A sequence of estimates of the location of the curve maximum is generated. The location of the next observation may be interpreted as the location of the most likely competitor (with the current best estimate) for the location of the curve maximum. A Brownian motion stochastic process is selected as a model for the unknown function, and the observations are interpreted with respect to the model. The model gives the results a simple intuitive interpretation and allows the use of simple but efficient sampling procedures. The resulting process possesses some powerful convergence properties in the presence of noise; it is nonparametric and, despite its generality, is efficient in the use of observations. The approach seems quite promising as a solution to many of the problems of experimental system optimization.
Two-Phase Viscous Axial Flow in a Pipe
Authors: Bentwich Michael
Published: November 2011

The author develops the general solution for the axial two-phase viscous flow in a long circular pipe. The interface between the two phases is taken to be either circular-cylindrical or an arc-segment of a cylindrical surface; possibly of zero curvature. The expressions for the velocity distributions obtained may be of use in calculating the amount of water that should be added to oil pipelines, in order to reduce pumping costs. The mathematical problem is that of potential and, hence, this work is also the solution of various analogous problems in the fields of elasticity, heat transfer, mechanics, or electricity.