bluuebunny/crossref_metadata_2025 huggingface dataset:
Fatigue Crack Propagation and Applied Stress Range—An Energy Approach
Authors: Liu H. W.
Published: November 2011

Using the saturation of hysteresis energy absorption as a criterion for fatigue crack propagation, the rate of crack propagation in a thin and wide metal sheet under repeated axial loading is found to be proportional to the square of the applied stress range. The local stress and strain fields adjacent to the crack tip are employed to compute the energy density. The analytical results correlate very well with the experimental results on 2024-T3 aluminum alloy.
The Magnetohydrodynamic Finite Step Slider Bearing
Authors: Hughes W. F.
Published: November 2011

A theoretical analysis is made of the finite step slider bearing using an electrically conducting liquid metal lubricant in the presence of a magnetic field applied both tangentially and transversely to the fluid film. The electrical terminal characteristics are discussed. For the transverse field it is found that only a slight increase in pressurization can be effected on open circuit conditions and that the short circuit condition is adverse. For the tangential field the effect is adverse for both open and short circuit. By supplying electrical power from an external source, however, significant increases in load carrying capacity can be achieved for both field geometries. Various curves of normalized load versus Hartmann number and pressure contour plots are presented.
Observation of Cavitation Scale and Thermodynamic Effects in Stationary and Rotating Components
Authors: Hammitt Frederick G.
Published: November 2011

This paper presents experimental measurements on cavitation performance effects for a venturi test section and a centrifugal pump. Theoretical expectations and comparisons with previous investigators’ data are discussed. The following general conclusions are drawn. (1) Significant scale effects were found for all degrees of cavitation, and for both venturi and pump. The direction of the effects is consistent with present literature. (2) Certain of these effects can be correlated in terms of Reynolds’ number; however, Reynolds’ number alone is not a sufficient correlating parameter.
The Effect of Warm Prestressing on Notch Fracture Strength
Authors: Brothers A. J. , Yukawa S.
Published: November 2011

The effect of warm prestressing at various stress levels on the notch bend fracture properties of a Ni-Mo-V steel at two levels of strength and Charpy FATT is determined. Warm prestressing of a notch sensitive steel effected increases in notch fracture strengths up to 150 percent of the unprestressed value. The fracture strength after prestressing increases proportionately with prestress level. The results indicate that the efficacy of warm prestressing is dependent on the temperature at which the notch strength is determined and its relation to the notch strength versus temperature behavior for a material.
On the Equivalence of Discrete Systems in Time-Optimal Control
Authors: Polak E.
Published: November 2011

It is shown in this paper that under a transformation which maps the state space of a system onto a sequence space in a one-to-one manner, time-optimal discrete regulator systems with different dynamics and modulators can be brought to equivalence and that this fact may be used to construct an optimal control strategy for one system from the known optimal control strategy of another one. In particular, the optimal control strategy for a pulse-width-modulated discrete system with a plant described by an nth order linear differential equation is derived in this manner.
The Frequency Responses and Jump-Resonance Phenomena of Nonlinear Feedback Control Systems
Authors: Hatanaka H.
Published: November 2011

A method is presented for analyzing the frequency responses and jump-resonance phenomena of nonlinear feedback control systems of any order. The nonlinearities treated in this paper are those whose outputs are single-valued odd functins of the inputs and are independent of frequencies of the inputs. The general conditions under which jump-resonance occurs are given and the system with saturation nonlinearity is analyzed fully as an example. The essential objective is to express the contours on the complex plane for the constant values of system variables, e.g., input amplitude, amplitude ratio, and phase shift.
A Statistical Analysis in Solid Film Lubrication
Authors: Adams Martin R. , Lum Mary D.
Published: November 2011

A factorial experiment was designed for evaluating the performance of a ceramic bonded solid film lubricant consisting of PbS/B2O3 in a 6:1 weight ratio. The effects of three factors, each at two levels were studied. These were bearing load, sliding speed, and rub block temperature. An analysis of variance of the test results was made. At 200 rpm, wear life increased with an increase in temperature between 700 and 1000 F for both load levels of 100 and 200 lb. At 600 rpm, however, wear life decreased with increasing temperature between 700 and 1000 F for both load levels. All results were obtained from runs made in air.
A Theory of an Externally Pressurized Circular Thrust Gas Bearing With Consideration of the Effects of Lubricant Inertia
Authors: Mori Haruo
Published: November 2011

A hydrodynamic theory, with consideration of the effects of compressibility and inertia of the lubricant, is applied to externally pressurized gas bearings which consist of circular and parallel surfaces. The ordinary velocity distribution in a bearing clearance with a parabolic shape is changed to a velocity distribution with a shape of elliptic function due to the effect of lubricant inertia. The pressure distribution in this case differs from the ordinary pressure curve calculated without consideration of inertia, but the load capacity seems to be almost the same in both cases. The theoretical results agree in general with the experimental results reported in a previous publication [3].
Measurement of the Effects of Viscosity on Aerofoil Lift Using the Electrolytic Tank
Authors: Platt A. , Norbury J. F.
Published: November 2011

A description is given of an electrolytic tank which was constructed for measuring the lift of aerofoils when boundary layer effects are considered. The associated electrical circuits for measurement of potential and potential gradient are given. Experiments were carried out on a single Piercy 12/40 aerofoil, and the measured lift agreed with wind tunnel observations within 1 percent. It is concluded that the electrolytic tank may be a useful tool in application to such problems.
Sweep and Dihedral Effects in Axial-Flow Turbomachinery
Authors: Smith Leroy H. , Yeh Hsuan
Published: November 2011

An approximate method for including the effects of sweep and dihedral when designing axial-flow turbomachinery blading is presented. Blades are said to have sweep when the flow direction is not perpendicular to the spanwise direction, and dihedral when the blade surface is not normal to the surface of an end wall. It is shown that blade cross sections should be cut by sectioning surfaces that are tangent to the axisymmetric stream surfaces of the meridional flow, but that these cross sections should be viewed by looking parallel to the axis (stacking line) of the blade. When this is done the observed blade shapes and flow angle distributions are most nearly comparable to those obtained from two-dimensional cascade experiments and analyses. This approach is found to be inadequate at the blade ends, however, and an analytical method is presented which yields a wall correction for blade rows of semi-infinite span. For all practical variations of the parameters involved in the design of axial-flow compressors and turbines, the wall correction can be conveniently calculated from a set of approximate formulas presented in this paper. The importance of an adequate axisymmetric solution (method not presented herein) as the first step in the analysis is pointed out; many of the effects of sweep and dihedral are traceable to the skewness of the force and thickness-blockage fields of the axisymmetric model. Finally, the paper summarizes the blading design procedure and applies the present work within the framework of the overall design. As an example, the method is used to design a swept cascade; previously reported test results for a similar cascade tend to substantiate the validity of the design procedure, but experimental results for a direct comparison with the theory are not available.
The Magnetohydrodynamic Journal Bearing
Authors: Kuzma Dennis C.
Published: November 2011

An analysis of an infinite journal bearing is presented for the case of an electrically conducting fluid in the presence of a magnetic field. The magnetohydrodynamic form of Reynolds’ bearing equation is derived and solved for the pressure distribution. The load carrying capacity is determined from the pressure distribution. Numerical data are presented for nonconducting bearing surfaces. These data are compared with the data from the ordinary journal bearing. It is shown that the load carrying capacity is increased by the application of a magnetic field.
Measurement of Pointwise Juncture Condition of Temperature at the Interface of Two Bodies in Sliding Contact
Authors: Ling F. F. , Simkins T. E.
Published: November 2011

An apparatus is described for bringing a rider specimen and a slider specimen into continuous sliding contact so that significant temperatures at the interface are achievable. The design is such that the flow fields of heat in the specimens would be at most two-dimensional, i.e., within engineering approximations; this fact makes possible the measurement of temperatures of the specimens without disrupting the flow fields of heat. Typical data are presented of speed, normal load, frictional resistance, and temperatures at strategic locations on the specimens. Using the heat-equation solutions obtained previously for the configurations concerned, contact-surface temperature distributions of both specimens are calculated from experimental data. Results give the pointwise, temperature juncture condition at the interface.
Application of Flow and Stability Theory to the Design of Externally Pressurized Spherical Gas Bearings
Authors: Grossman Robert L.
Published: November 2011

Application of the flow theory of Laub and Norton [1] and the stability theory of Licht, Fuller, and Sternlicht [2] is made to the design of externally pressurized spherical gas bearings. Analytical results are presented in the form of “stability maps” (stability limits) and were confirmed by experimental data. The double-valuedness of stable loading for a constant supply pressure is predicted. The design procedure presented appears to be a dependable method for assuring stable operation of spherical gas bearings.
Low Cycle Fatigue Damage in Pressure-Vessel Materials
Authors: Sessler J. G. , Weiss Volker
Published: November 2011

Strain-controlled tension-compression fatigue tests were performed on the ASTM pressure vessel steels, A302 and A225, to study the damage processes that lead to failure in low cycle fatigue. The measurements of static property changes in partially cycled specimens, and hysteresis loop effects obtained during cycling, were utilized to reflect the pattern of damage accumulation. In addition, strain cycling tests were conducted on these materials to assess the applicability of the relationship Nf=εF−ε0εTR2 as proposed by Manson [4] and Coffin [5] and modified by Sachs, et al. [6]. The experimental data obtained were in good agreement with the failure life and the effect of mean strain as predicted by the foregoing equation. Accordingly, a positive mean strain (prestrain in tension) reduces fatigue life, since the fracture strain available for cycling is reduced by the amount of the prestrain. The damage studies indicated, however, that this equation cannot be used to describe the progress of damage during strain cycling. Rather, it appears that damage is governed by at least two, possibly interdependent, processes; namely, the loss of available ductility due to strain hardening and the formation and growth of cracks which finally determine failure. Both processes are reflected in the remaining ductility after partial cycling. At present, it is not clear how the two processes combine to yield the experimentally confirmed relationship, Nf=εF−ε0εTR2.
Photothermoelastic Investigation of Thermal Stress in Flat Plates
Authors: Becker Herbert , Colao Angelo
Published: November 2011

Predictions of thermal stresses in various shape flat plates with a parabolic temperature field applied in one direction were found to yield good agreement with photothermoelastic analysis. A theory based upon an analog was found to agree with experiments on rectangular plates better than two other methods of analysis. The analog procedure was utilized for analysis of a circular plate, to the results of which an engineering modification was applied to obtain theoretical data for comparison with experiments on a hexagonal plate with and without a central circular hole.
On the Optimization of the Stiffness of Externally Pressurized Bearings
Authors: Ling Marvin T. S.
Published: November 2011

This paper presents theoretical studies of the method of optimization of the stiffness of externally pressurized bearings. When an externally pressurized bearing is designed to operate at any given film thickness, it is found that the maximum bearing stiffness can be obtained by proper selection of the value of the ratio of recess to supply pressure, Pr/Ps. While various values of Pr/Ps can be attained by either varying the restrictor constant for a given film thickness or varying the film thickness for a given restrictor constant, the important quantity to vary in determining the optimum condition is the restrictor constant rather than the film thickness. For an incompressible fluid, the Pr/Ps value for which the bearing stiffness is optimized depends only on the type of compensation used, while for a compressible fluid it is slightly affected by exhaust pressure.
Analysis of Bearings Operating in Turbulent Regime
Authors: Constantinescu V. N.
Published: November 2011

Proceeding from the results obtained previously [5] this paper analyzes theoretically the three-dimensional motion in the lubricant layer by using Prandtl’s mixing length theory. Formulas and diagram are presented for calculating journal and thrust bearings subjected to turbulent lubrication.
On the Existence of Optimal Controls
Authors: Markus L. , Lee E. B.
Published: November 2011

The problem of existence of various types of optimum controls for controlling processes which are described by ordinary differential equation models is considered. The results presented enable one to test if there does exist an optimum control in the class of controls under consideration before proceeding to the construction of an optimal control.
Analytical and Experimental Study of Externally Pressurized Air Lubricated Journal Bearings
Authors: Lemon Jason R.
Published: November 2011

A simplified analysis for calculating the characteristics, such as stiffness, flow, and load of an externally pressurized gas journal bearing, is obtained through a standard one-dimensional flow approach altered to take into account the effect of circumferential pressure variations. From this analysis, it is revealed that bearing stiffness has an optimum which, it is further shown, can be chosen through a proper selection of bearing design parameters, such as radial clearance, upstream resistor, and supply pressure. As the analysis is developed each assumption is experimentally verified. The final predictions of the analysis are also verified. It is felt that the analysis is sufficiently simple to allow comparison of many different bearing configurations, while sufficiently complete to compare very well against experimental measurements in all respects. A comparison is made between the recessed and nonrecessed bearing.
The Magnetohydrodynamic Slider Bearing
Authors: Snyder William T.
Published: November 2011

An analysis is presented of the slider bearing using an electrically conducting lubricant, such as a liquid metal, in the presence of a magnetic field. The solution permits the calculation of the load-carrying capacity of the bearing. A comparison is made with the classical slider bearing solution. It is shown that the load capacity of the bearing depends on the electromagnetic boundary conditions entering through the conductivity of the bearing surfaces. Numerical data are presented for nonconducting surfaces with the emphasis on a comparison between the classical bearing and the magnetohydrodynamic bearing characteristics. It is shown that a significant increase in load capacity is possible with liquid metal lubricants in the presence of a magnetic field.
On the Periodic Modes of Oscillation in Pulse-Width-Modulated Feedback Systems
Authors: Jury E. I. , Nishimura T.
Published: November 2011

A general procedure for obtaining information on the periodic modes of oscillation in PWM and nonlinear sampled-data feedback systems is considered in this paper. Based on the equivalence of PWM in the state of limit cycles to the finite pulsed systems with the periodically varying sampling pattern, the methods of analysis applied to the latter are extended to obtain these limit cycles. In particular, the final value theorem is applied to obtain the fundamental response equation which gives rise to the limit cycles for the various specified modes. The theory is applied to systems with and without integrator and the results are checked by the phase-plane approach. Two kinds of nonlinearities, namely, pulse-width modulation and saturating gain, are discussed among the various nonlinearities, and examples are presented for each of these cases. Furthermore, both self-excited and forced oscillations are examined as well as the possible existence of limit cycles for certain specified modes. This approach to examining the periodic modes is not restricted to the type of non-linearity or the order of the system and thus can be applied to various forms of nonlinear discrete systems. However, it is based on the assumption that the mode of the limit cycle is specified, as can be done in certain cases, and thus the method of this paper permits the study of the conditions that sustain those oscillations.
Cumulative Damage in Creep-Rupture Tests of a Carbon Steel
Authors: Randall P. N.
Published: November 2011

A life-fraction rule is often used to predict the rupture life of a piece of elevated-temperature equipment exposed to several temperature and stress conditions. It is based on the assumption that the fraction of rupture life used up in a specific time at one stress and temperature is independent of previous conditions and therefore can be estimated from tests in which exposure conditions were held constant. Test data are needed to substantiate the validity of this rule. The results of 23 constant-stress creep-rupture tests on an ASTM A201A carbon steel have shown this rule to be valid when all of the test conditions caused appreciable creep strain. Even so, it may not be valid for prolonged service above 1100 F followed by service at lower temperatures. Creep rates are reasonably predictable for constant-stress conditions when only temperature is changed. The transient creep rate accompanying a change in stress continues long enough to make creep-rate predictions unreliable. Periodic shutdowns during tests at constant stress and constant temperature have little effect on either rupture life or creep rate.
Dynamics of Human Operator Control Systems Using Tactile Feedback
Authors: Weissenberger S. , Sheridan T. B.
Published: November 2011

Much has been learned in the past ten years about the dynamic performance of the human operator in control tasks primarily involving visual stimuli. In many human activities, however, sight is complemented or superseded by other senses. One important sense modality whose dynamic use is as yet poorly understood is touch. This paper describes an experimental technique for investigating human operator dynamics in tasks where tactile stimulus information is of primary importance; some exemplary results are presented.
Effect of Cavitation on the Accuracy of Herschel-Type Venturi Tubes
Authors: Numachi F. , Kobayashi R. , Kamiyama S.
Published: November 2011

Experiments were undertaken to determine the effect of cavitation on the discharge coefficient of venturi tubes of Herschel type, and on additional limitations that must be applied to existing standards governing dimensional proportions of these venturi tubes in order to hold deviations in reading down to within limits allowed by standards.
Cumulative Fatigue Damage With Random Loading
Authors: Gatts R. R.
Published: November 2011

A general concept of the accumulation of fatigue damage is applied where stress amplitude is a random time function with a specified amplitude distribution. A differential equation relating damage accumulation to the amplitude distribution of stress is derived. This equation is applicable to both continuous and discrete distributions. Solutions of the equation are used to predict life under random loading on the basis of constant amplitude S-N data. Such predictions are compared for both continuous and discrete stress amplitude distributions and found in better over-all agreement with the data than comparable predictions by the linear rule.
On the Stability of Rotors in Cylindrical Journal Bearings
Authors: Rentzepis G. M. , Sternlicht B.
Published: November 2011

The regions of stability for plain cylindrical journal bearings have been determined analytically here. The linear “variational” equation of motion has been employed to obtain the stability regions bounded by families of load-carrying capacity and operating eccentricity curves. The results were applied to the “quasi-static” equilibrium case for gas lubricated cylindrical journal bearings of L/D = 2. They show that there exists a “minimum” in the stability curves, a prediction supported by experimental evidence. The results of this work seem to bridge together observation on stability at very small clearances and large ones.
Effects of Extra Sinusoidal Inputs to Nonlinear Systems
Authors: Oldenburger R. , Boyer R. C.
Published: November 2011

This paper presents a technique for predicting the effect of an extra high frequency sinusoidal input on systems with various commonly occurring types of nonlinearities. This input may be thought of as an extra input introduced into a system to improve the performance of nonlinear components. The mathematical analysis is greatly simplified by the introduction of a certain approximation to the input-output relationship of a nonlinear element when the input to the nonlinear element is the sum of the regular sinusoidal input signal and an extra sinusoidal signal of higher frequency. For the approximation to be valid experience and theory indicate that the ratio between the frequencies of the sinusoidal inputs should be on the order of ten or more. The extra sinusoidal input may reduce or remove the hunt (self-oscillation) of some systems, but it may create a hunt in others. In computations, a nonlinear element with an extra sinusoidal input may often be replaced by an equivalent nonlinear element without the extra input. By introducing the extra input a designer may be saved the expense of physically replacing one nonlinear component by another, the input-output characteristics of the first being transformed by the extra input into the characteristics of the second. The introduction of an extra signal may yield much better transient response than is possible by changing open loop gain. Examples are given with analog computer verification.
Fracture of Flat and Curved Aluminum Sheets With Stiffeners Parallel to the Crack
Authors: Frisch J.
Published: November 2011

The mode of crack propagation and failure in relatively large 2024-T3 aluminum sheets reinforced with stiffeners parallel to the crack direction has been investigated. Curved specimens with a 69-in. radius of curvature as well as flat panels were subjected to uniaxial tension perpendicular to a simulated crack to study the effects of curvature, crack location, and stiffener spacing. Increase in strength due to stiffening particularly in the curved panels was observed although these specimens exhibited considerable lower crack strength than flat ones. For the specimens tested, crack location as well as variations of stiffener spacing from 3 to 12 in. had no appreciable effect on either critical crack length or failure stress.
Reduction of Dimensionality, Dynamic Programming, and Control Processes
Authors: Bellman Richard , Kalaba Robert
Published: November 2011

A major difficulty in the way of a successful systematic approach to the study of control processes by way of the theory of dynamic programming is the occurrence of processes having state vectors of high dimension. However difficult the problem is for systems ruled by a finite set of differential equations, it is several orders of magnitude more complex for systems of infinite dimensionality and for systems with time lags. By combining a technique presented earlier for dealing with finite dimensional systems and various methods of successive approximations and quasi-linearization, certain classes of control processes associated with infinite dimensional systems can be treated. The ideas are illustrated by discussing control of a system involving a time lag and control of a thermal system.
The Effect of the Method of Compensation on Hydrostatic Bearing Stiffness
Authors: Malanoski Stanley B. , Loeb Alfred M.
Published: November 2011

Capillary, orifice, and flow control valve compensation of hydrostatic thrust bearings is investigated theoretically with regard to the effect of these three methods of compensation on the stiffness of the lubricant film. Equations are derived which permit rapid determination of bearing stiffness at any given load and film thickness. When a hydrostatic bearing is made to operate at any given film thickness and load, it is found that at this load and film thickness no adjustment of the compensating element or supply pressure will alter the fact that ψvalve > ψorifice > ψcapillary where ψ equals the absolute value of stiffness. Furthermore, with fixed supply pressure and compensation, this stiffness relationship will remain the same for all practical values of load above and below the initial film thickness-load point.
Theory of Lubrication and Failure of Rolling Contacts
Authors: Sternlicht B. , Lewis P. , Flynn P.
Published: November 2011

The fatigue life of rolling-element bearings has been the subject of numerous investigations. Most recently the influence of the lubricant on fatigue failure has been given added emphasis. This paper presents the results of an investigation which was undertaken in order to gain a better understanding of fluid behavior in the contact zone and to determine the influence of the lubricant on rolling contact fatigue life. The investigation had three distinct facets: (a) An analysis was performed on pressure and temperature distribution within the contact zone of rolling disks. In the analysis Reynolds, energy, and elasticity equations were solved simultaneously and fluid properties, such as viscosity dependence on temperature and pressure were included. (b) Dynamic stresses in two contacting cylindrical bodies were measured by means of photoelastic techniques. These measurements were used to test the validity of the analytically predicted stress distribution. (c) High-speed ball-bearing fatigue tests were conducted with two specially blended oils which had the same viscosity at the bearing inlet temperature, but widely different pressure viscosity characteristics. The physical characteristics of the oils were the same as those considered in the analysis. The paper summarizes the work and presents a hypothesis for the failure mechanism.
On the Dynamics of Steam Liquid Heat Exchangers
Authors: Hempel Arvid
Published: November 2011

The aim of the present work has been to present relatively simple transfer functions for steam/liquid heat exchangers, relating outlet liquid temperature to variations in, respectively, the steam temperature, the liquid velocity, and the inlet liquid temperature. The transfer functions are first obtained from the partial differential equations of the system and then simplified. From the simplified expressions the transient response can readily be obtained and, in addition, they are of a form easily simulated on an analog computer. Experimental frequency response data are provided. An analog computer proved useful in analyzing phase lag and amplitude ratio in the frequency response measurement.
Experimental Investigation of Corners in the Yield Surface
Authors: Phillips Aris , Gray G. A.
Published: November 2011

The results of fourteen combined stress tests with variable stress ratios on annealed commercially pure aluminum are reported. These tests were made on a combined tension-torsion testing machine of a dead-load type. It is shown that the loading path carries a pointed vertex with it. However, the direction of the plastic-strain increment vector differs only slightly from the direction predicted by the Mises theory. Finally, the experiments indicate that the form of the yield surface at a considerable distance from the stress increment vector agrees much better with the prediction of the slip theory than it does with the prediction of the Mises theory.
Generalization of a Class of Solutions of the Laminar, Incompressible Boundary-Layer Equations
Authors: Winer Ward O. , Hansen Arthur G.
Published: November 2011

The momentum, continuity, and energy equations of the laminar incompressible boundary layer in a skew-linear co-ordinate system are similar in form to those in a rectangular co-ordinate system. This fact is used to generalize the requirements for similarity solutions in rectangular co-ordinates. The requirements for all possible similarity solutions of the boundary-layer and energy equations in skew-linear co-ordinates are presented. The usual Cartesian co-ordinate system is a special case of co-ordinate systems considered.
Scale Effects on Cavitation
Authors: Holl J. William , Wislicenus George F.
Published: November 2011

Scale effects on cavitation are defined here as departures from the classical similarity relations when changing size, velocity, and/or properties of the fluid. The various phenomena governing such scale effects are examined and the resulting similarity laws, together with some expected scale effects, are tabulated. The theoretical expectations are then compared with extensive test data on desinent cavitation in cold water. This comparison leads to two different sets of plausible relationships for cavitation attached to a streamlined body, and cavitation not attached to a solid wall. However, the conclusions drawn are only tentative and qualitative, clearly indicating the need of further careful experimentation and analysis.
Tensile Properties of AISI Types 304 and 347 Stainless Steels at Moderate Temperatures for Section Sizes Ranging From Bars to Extremely Large Forgings
Authors: Pryle W. H. , Wessel E. T.
Published: November 2011

The tensile properties of AISI types 304 and 347 annealed stainless steels were investigated for the temperature range from 75 to 800 F. Several lots of materials were studied in each of several section sizes ranging from bar stock to extremely large forgings. A considerable variation in properties, particularly yield strength and elongation, were observed between different lots of a given type of steel of a given size category. These variations correlated with variations in the annealed hardness and are attributed to the use of different annealing treatments by the suppliers. At equivalent hardness levels the properties obtained from the various section sizes were comparable. Within any given lot or forging the properties were quite uniform for equivalent specimen orientations. The transverse ductility of the large forgings was considerably less than the longitudinal ductility. However, this relatively poor ductility did not lead to notch sensitivity or embrittlement problems.
Effect of Combined Stress on Yield and Fracture Behavior of Zircaloy-2
Authors: Mehan R. L.
Published: November 2011

The yielding and fracture characteristics of Zircaloy-2 as a function of stress state were investigated at room temperature through the medium of thin-walled cylindrical specimens under internal pressure and axial tension. Stress states from uniaxial longitudinal tension to uniaxial tangential tension were examined. Two tests at elevated temperature were performed at a single stress ratio. It was found that the fracture ductility lessened with increasing biaxiality. A minimum in ductility was found at balanced biaxial tension where the fracture ductility, as expressed by the effective strain, was 29 per cent. The yielding and plastic flow properties were found to be highly anisotropic. Two methods were used to express the plastic flow data: a graphical approach and a theoretical analysis based on a theory proposed by R. Hill, either one of which is suitable to express the flow properties of Zircaloy-2 under various states of combined stress.
Effect of Cell Geometry on the Shear Modulus and on Density of Sandwich Panel Cores
Authors: Chang Chieh C. , Ebcioglu Ibrahim K.
Published: November 2011

A simple analytic theory for the effect of cell geometry on both the shear modulus and the density of sandwich panel core is presented. The core shear modulus in different directions is analyzed to include the effects of the angle α and the aspect ratio b/a of the cell. It is also found that the minimum cell weight of the sandwich core depends both on the cell angle α and the cell aspect ratio b/a. The theory compares fairly well with some available experiments. The cell geometry chosen is so general that the regular hexagonal and square cells of commercial sandwich cores are special cases.
Bursting of Tubular Specimens by Gaseous Detonation
Authors: Randall P. N. , Ginsburgh I.
Published: November 2011

The paper describes some experimental work designed to investigate the bursting of pipe and pressure vessels by gaseous detonation. The test specimens were 3.25-in-OD tubes, 12 in. long, and of 0.040 to 0.070-in. wall thickness. The specimens, cut from hot-rolled carbon-steel pipe, and also from drawn carbon-steel tubing, were tested at several temperatures, which were chosen to produce failures both above and below the brittle transition temperatures for the two materials. In addition, an austenitic stainless-steel specimen was tested under very severe conditions in several unsuccessful attempts to fragment it.
Rolling-Contact Fatigue Studies With Four Tool Steels and a Crystallized Glass Ceramic
Authors: Zaretsky Erwin V. , Anderson William J.
Published: November 2011

The rolling-contact fatigue properties of crystallized glass ceramic balls together with AISI M-1, AISI M-50, Halmo, and WB-49 alloy steel balls tempered to various hardness levels were determined in the NASA spin rig and in the five-ball fatigue tester. A continuous increase in fatigue life and load capacity for each steel was observed with increased ball hardness. These results correlate with resistance to plastic deformation as measured with spherical specimens in rolling contact but do not correlate with elastic limit and yield strength measured for bar specimens. These bar specimens showed optimum values at intermediate hardness levels. Extremely low scatter in fatigue life for the ceramic balls indicate that the degree of structural homogeneity may be an important factor in life scatter of bearing materials.
Complete Pump Characteristics and the Effects of Specific Speeds on Hydraulic Transients
Authors: Donsky Benjamin
Published: November 2011

This paper presents complete pump characteristics of specific speeds 1800, 7600, and 13,500 (gpm units) in the ν – hP (flow ratio-head ratio) co-ordinate system. The method of developing these complete pump characteristics from test data is described. The three complete pump characteristics are compared, and the effects of specific speed on hydraulic transients caused by power failure or pump shutoff is presented.
The Phase-Plane Topology of the Simple Surge-Tank Equation
Authors: Marris A. W.
Published: November 2011

An investigation of the phase-plane solution curves of the nonlinear differential equation describing the motion of the water level in a simple surge tank operating in conjunction with a turbine governed for constant hydraulic power acceptance. The phase-plane solution picture is developed by determining the form of the solution of the equation near each of its singularities. The picture enables prediction and interpretation of instability and drainage phenomena.
Human Body as an Inconstant Heat Source and Its Relation to Clothes Insulation: Part 2—Experimental Investigation Into Dynamics of the Source
Authors: Iberall A. S.
Published: November 2011

Quantitative measurement on the human in the so-called evaporative, vasomotor, and metabolic control regimes has revealed frequency spectrum of sustained thermal power oscillations with approximate periods of 2, 7, 35 min, and 3 1/2 hr independent of the regime. Step function adjustments take place with a time constant of about 7 min. It is believed that the 3 1/2 hr cycle represents the shortest equilibrium cycle. The hypothesis that it might be possible to measure the resistance of clothing as an ohmic relation among time-averaged equilibrium values, and for a specific mode of operation of the system has now been put in rational context in the time domain. Two equilibrium modes of the human system were explored. The active mode of operation of the system, to which the resistance concept of clothes is most applicable, is as a feedback system in which the extremities are used as error indicators of deviations from a comfort level set point. In response to deviations, the human feeds back a signal to generate an activity level in which only internal work—immediately degraded into heat—is done to maintain the comfort level. This is referred to as the comfort mode of operation of the system. Another “survival” mode of operation of the system is also described.
Discharge Coefficients and Steady-State Flow Forces for Hydraulic Poppet Valves
Authors: Stone J. A.
Published: November 2011

Experiments were run on a poppet valve operating in hydraulic oil. The experimental values of the flow forces and discharge coefficients were about 25 per cent below the predicted theoretical values. Although there was some scatter in the values of discharge coefficients, there was good correlation for the flow forces. Flow forces are strongly influenced by the downstream configuration. The smaller the diameter of the downstream chamber, the higher the forces. A poppet configuration was designed and tested which virtually eliminated the flow forces.
Indentation of Metals by Cavitation
Authors: Wheeler W. H.
Published: November 2011

The first stage in cavitation damage—indentation where cavitation bubbles collapse near the metal surface—was observed and measured by Knapp [1]. The author suggested that the high temperature of indentation points, caused by the absorption of work in their formation, should create conditions favorable to energetic local chemical action between water and metal. The brittle oxide films thus produced would be ruptured by later blows, resulting in erosion. Photomicrographs taken in monochrome and color show the form and texture of indentations with associated corrosive oxidation. Parallel experiments were made with toluene whose inertness permitted the elimination of chemical factors. The special features of the microscope technique employed to get the photographs are explained.
The Fluids Engineering Laboratory at the University of Michigan
Authors: Edmonson G. V.
Published: November 2011

Although the purpose of this paper is specifically that of describing the Fluids Engineering Laboratory at the University of Michigan, it is clear that an understanding of the faculty philosophy underlying the planning of this unit is a necessary part of the document. This is an age of technological expansion, the rate-of-change of which exceeds any progress the world has hitherto known. The seeking of new knowledge and the application of that knowledge is the work of an ever-increasing number of competent scientists and engineers not only skilled in a technology but equally successful in the art of human understanding and relationships. Institutions of higher education are an integral part of this technological age and, because of this fact, find themselves confronted with the task of foreseeing the educational and research needs of the future. This is an immense task, one which is occupying many of the best minds of this generation. The technological and social progress of the coming generation depends upon the continuing flow of students emanating from our institutions of learning. They must be adequately prepared for the responsibilities which they alone can assume.
The Importance of Spinning Friction in Thrust-Carrying Ball Bearings
Authors: Reichenbach G. S.
Published: November 2011

Experimental work was done rolling balls on flat plates and in V-grooves at loads and contact angles corresponding to usual thrust-bearing practice. It is shown that the spinning action of the ball with respect to the race should account for the major part of the over-all friction of a thrust-carrying ball bearing. Variables studied included contact angle, conformity, load, lubricant, and temperature. The results have been correlated and shown to follow theoretical predictions.
Bearing Oil-Ring Performance
Authors: Lemmon D. C. , Booser E. R.
Published: November 2011

A series of tests was made with rings ranging from 2 3/4 to 16 1/2 in. ID and at journal speeds up to 4000 fpm. Correlation of the results provides means for calculating ring speed for any journal speed. Oil viscosity, ring weight and diameter, ring immersion, and journal diameter are taken into account. From this calculated ring speed, oil delivery can then be estimated from equations incorporating the effect of oil viscosity and related operating factors.
Creep Rupture Tests for Design of High-Pressure Steam Equipment
Authors: Davis E. A.
Published: November 2011

Creep rupture tests on tubular specimens of type 316 stainless steel were run at 1200 F and at pressures up to 24,000 psi. The specimens were tested under pure internal pressure and equal biaxial tensions. The results of these tests correlate favorably with those of uniaxial tension tests if a comparison is made on the basis of effective stress and effective strain rate.
Design of Pressurized Cylinders for High-Temperature Applications
Authors: Traexler J. F.
Published: November 2011

General equations for the stresses in a thick-walled cylinder in a state of plane strain are derived considering “steady-state” creep. A specific form of the creep-rate function is assumed and numerical examples are included to show the effect of geometry and material properties.
Rotating Wakes in Vaneless Diffusers
Authors: Dean Robert C. , Senoo Yasutoshi
Published: November 2011

Experimental investigations have shown that the flow discharged from a centrifugal compressor or pump impeller into a diffuser is often unsteady and axially asymmetric. A theory based upon a simplified model is developed for this type of flow. The theory predicts a significant reversible work transfer between parts of the flow with different velocities. This effect only occurs in cases of rotating distortion patterns; stationary distortion patterns, therefore, behave differently. Theoretical results are compared to measurements and good agreement is found. The implications of the theory have been investigated by means of machine computations and are discussed herein.
Laminar Boundary Layers in Oscillatory Flow
Authors: Hill P. G. , Stenning A. H.
Published: November 2011

A study has been made of the effects of free stream oscillations on laminar boundary layers of the Howarth type. Detailed measurements of oscillations have been made for the two conditions of Blasius flow and a Howarth flow fairly near separation. It has been found that there are three types of behavior, corresponding to low, intermediate, and high frequencies. Low and very high frequency oscillations are shown to be well described by existing approximate solutions. However, an intermediate frequency region required a new analytic treatment, the results of which do in fact account for the measured flow behavior in that region.
Experimental Determination of Statistical Properties of Two-Phase Turbulent Motion
Authors: Soo S. L. , Ihrig H. K. , El Kouh A. F.
Published: November 2011

Experimental methods for the determination of certain statistical properties of turbulent conveyance and diffusion of solid particles in a gaseous state are presented. Methods include a tracer-diffusion technique for the determination of gas-phase turbulent motion and a photo-optical technique for the determination of motion of solid particles. Results are discussed and compared with previous analytical results.
The Stability of Metals Under Cyclic Plastic Strain
Authors: Coffin L. F.
Published: November 2011

During the course of an experimental investigation on the effect of cyclic plastic strain on metals [1], it was observed that under certain conditions materials subjected to cyclic plastic strain showed little stability to simultaneously imposed steady stresses. The present paper describes and interprets some experiments undertaken to learn more about this behavior of real materials.
Steady-State Creep of a Thick-Walled Cylinder Under Combined Axial Load and Internal Pressure
Authors: Finnie Iain
Published: November 2011

Equations are developed for prediction of steady-state creep stresses and strain rates in a thick-walled tube under combined internal pressure and axial load. An analytical solution of the equations, in closed form, is not possible but numerical solutions to the equations are tabulated for various values of the variables. For values of the variables, other than those tabulated, interpolation is usually adequate. If this is not the case, a trial method of calculation is presented which uses the tabulated solutions as a starting point. Simple approximate solutions, which apply for the cases in which the additional axial load is small or large relative to the axial load due to internal pressure, are also given.
A Study of Viscosity Effect and Its Compensation on Turbine-Type Flowmeters
Authors: Lee W. F. Z. , Karlby Henning
Published: November 2011

An analysis of the viscosity effect on meter accuracy of an axial-flow turbine-type flowmeter is formulated by the use of physical reasoning and experimental evidence. This analysis indicates methods of compensating for the effect of viscosity on meter accuracy. One method of compensating for viscosity is analyzed and design criteria are developed for constructing a viscosity compensator. Test results of a turbine meter, before and after installation of a viscosity compensator, are presented for comparison with the results determined from analysis.
Viscous Dispersion in Water Hammer
Authors: Walker M. L. , Kirkpatrick E. T. , Rouleau W. T.
Published: November 2011

When a column of fluid moving with uniform velocity is instantaneously stopped at the downstream end a pressure wave is propagated upstream. In an inviscid fluid the wave is a step discontinuity, and the pressure so calculated serves as an easily obtained upper bound for all practical “water-hammer” problems, the exact solution of which may be either difficult or impossible to obtain. This paper describes an analysis of viscous dispersion in relation to the upper bound. The conclusion is reached that in problems of practical interest the bound is not significantly changed by the dispersive effects of viscosity.