bluuebunny/crossref_metadata_2025 huggingface dataset:
An Experimental Study of Thermally-Induced Flow Oscillations in Supercritical Helium
Authors: Daney D. E. , Ludtke P. R. , Jones M. C.
Published: November 2010

The density wave stability boundary has been experimentally determined for super critical helium flowing in a long (L = 185 m), heated channel of high aspect ratio (L/d = 46 (10)4). A pressure drop ratio and the fluid expansion ratio correlate the oscillation inception point data. The growth of enthalpy (temperature) perturbations in a heated channel has been experimentally verified. During the density wave oscillation, the channel exit temperature and inlet mass flow were observed to be in phase, and the oscillation period was close to twice the fluid transit time. All three observations agree with a simple incompressible flow model. Oscillation amplitudes as great as 11 K and 100 percent of inlet flow were observed.
Upper Limit of CHF in the Saturated Forced Convection Boiling on a Heated Disk with a Small Impinging Jet
Authors: Katto Y. , Shimizu M.
Published: November 2010

Critical heat flux (CHF) in the forced convection boiling on an open heated disk being supplied with saturated liquids through a small high-speed jet impinging at the center of disk is studied experimentally employing Refrigerant 12 at comparatively high pressures from 6.0 to 27.9 bars as well as water and Refrigerant 113 at atmospheric pressure. Generalized correlations of CHF are obtained for two characteristic regimes: V-regime where CHF is variable and I-regime where CHF is invariable for the change of jet velocity. Then, the boundaries of each regime are discussed clarifying the aspects for the lower limit of jet velocity capable of generating I-regime as well as the upper limit of CHF.
Evaporative Heat Transfer and Pressure Drop Performance of Internally-Finned Tubes with Refrigerant 22
Authors: Kubanek G. R. , Miletti D. L.
Published: November 2010

Heat transfer and pressure drop measurements were performed on three integral spiralled inner-fin tubes (12.7–15.9 mm OD, 30–32 fins, fin height 0.5–0.6 mm) with two-phase flow of refrigerant 22 under evaporating conditions. The data were compared with the performance of smooth tubes with and without a star-shaped insert. Based on the same length of heated test section (0.80 and 2.44 m), change in refrigerant quality (0.2 and 0.7) and mass velocity range (65,000 to 270,000 g/s · m2): (1) The enhancements in heat transfer coefficient for the internally-finned tubes over those for the smooth tubes ranged from 30 to 760 percent, and typically increased with mass velocity. Tighter fin spiralling significantly increased heat transfer. (2) The enhancements in heat transfer coefficient for the smooth tube with the star-shaped insert ranged from 40 to 370 percent, but decreased with mass velocity. (3) The increases in pressure drop for the internally-finned tubes over those for the smooth tubes ranged from 10 to 290 percent, while those for the smooth tube with the star-shaped insert were 300 to over 2000 percent. The factors enhancing the performance of the internally-finned tubes include the low fins which result in only a small reduction in cross-sectional flow area, and the tight spiral which increases the corner length per unit length of tube available for nucleation of vapor bubbles.
Convective Heat Transfer in Porous Media
Authors: Montakhab Ali
Published: November 2010

Convective heating or cooling of granular solids or porous media is of interest in the design of thermal energy storage systems. The solutions to the energy initial boundary value problems governing convective heat transfer between a fixed bed of granular solids and a steady flow of heating or cooling fluid are presented. The storage system is considered to be initially in thermal equilibrium at a uniform temperature, a step change in the inlet temperature of the working fluid is imposed, and the thermal response of the system predicted. The results are valid for gases and liquids when the temperature gradient in the solid material is small and axial conduction effect is negligible in comparison with the convective heat transfer. Unlike the previously available solutions to this problem, the results presented are in closed form. This greatly simplifies evaluation and design of thermal energy storage systems of this general type.
Thermal Behavior and Friction in Journal Bearings
Authors: Nica Al.
Published: November 2010

This paper deals with friction and the field of temperature in the lubricant film of journal bearings. Theoretical results regarding the thermal behavior are checked with experimental data and good agreement is found. Emphasis is put on the variation of temperature and lubricant flow with the operating characteristics of the bearing and it is seen that theoretical predictions for minima of friction torque are backed by temperature measurements. Further on, the friction torque and the mechanism of heat dissipation in bearings are dealt with, in order to verify the assumptions used in the calculation schemes. The means of efficiently cooling the bearing are also discussed, as well as the part played by the divergent zone in this process.
Rigid-Body Rotor Dynamics: Dynamic Unbalance and Lubricant Temperature Changes
Authors: Badgley R. H. , Booker J. F.
Published: November 2010

The case of a symmetric rotor supported on two identical, rigidly mounted, self-aligning, finite-length (L/D = 1) fluid-film journal bearings is considered. Rotor position is described by two translation coordinates in a plane perpendicular to the bearing line of centers, and by three Euler angles. Introduction of various amounts of dynamic unbalance via the inertia tensor off-diagonal terms (products of inertia) allows determination of angular velocity and static eccentricity ratio combinations leading to bearing “failure” defined for arbitrary maximum allowable eccentricity ratios. Instability hysteresis, defined here as the persistence, during rotor deceleration, of instability to speeds below which it first appeared, is considered by means of the above model. Equations and methods developed for the unbalance investigation are adapted to a variable-speed analysis. With both constant and variable mean bearing temperatures, variable-speed simulations terminating at constant speed are observed to be stable when the terminating point is below the instability threshold curve on the angular velocity-static eccentricity ratio parameter plane and unstable when above. The slope of the threshold curve and the shape of the equilibrium-condition path on the parameter plane (single-line path for constant temperature, closed curve for variable temperature) apparently combine to produce hysteresis in the variable temperature case and none at constant temperature.
Implementation of Time-Transient and Step-Jump Dynamic Analyses of Gas-Lubricated Bearings
Authors: Shapiro W. , Colsher R.
Published: November 2010

The dynamic analysis of gas-bearing systems are discussed from two points of view. The “Time-Transient” method which has been previously reported in a number of papers [1] [2] couples the lubrication and dynamic equations and integrates forward in time, to provide a time history of the motions of the system in its various degrees of freedom. The “Step-Jump” approach determines the system response due to a sudden impulse from an assumed stable operating position. The two theoretical approaches are discussed qualitatively. Implementation is presented by way of sample problems, including a fixed and resiliantly mounted hybrid journal bearing system and an elastic gimbal mounted Rayleigh-Step thrust bearing. The advantages, disadvantages and complementary characteristics of each method are presented. Details of the Step-Jump analysis for the hybrid bearing are included as an Appendix.
The Influence of Wall Conductance on Performance of the MHD Hydrostatic Thrust Bearing
Authors: Kamiyama S.
Published: November 2010

It is made clear that the influence of wall conductance on the pressure and load capacity of the magnetohydrodynamic thrust bearing must be considered when the inertia effect under the condition of high-speed rotation cannot be ignored. Further, by the numerical examples, the optimum bearing materials to improve the bearing performance under these conditions are determined.
Inertia Effects in Fully Developed Axisymmetric Laminar Flow
Authors: Makay E. , Trumpler P. R.
Published: November 2010

The three components of the Navier-Stokes equation are solved here simultaneously in their nonlinear form for axisymmetric radial inward and outward flow cases between two parallel rotating walls. Examples of application in rotating machinery are close clearance face seals, thrust bearings, high speed thrust device, rotating disk, narrow gap between centrifugal impeller and housing, etc. The differential equations of motion with the proper boundary conditions were converted into integral equations of the “Fredholm second kind” type and solutions have been obtained for the nonlinear cases. The use of integral equations greatly enhanced the advantage of the numerical solution developed here. The results are compared to simplified solutions and to solutions considering some of the nonlinear members. The effects of the inertia forces are especially emphasized and discussed in detail. The inclusion of these terms significantly affected the velocity field in the area discussed here. It is shown here that for low inward or outward flows the centrifugal force, and for high flows the convective acceleration terms have the main controlling influence on the radical velocity component.
Sliding Surface Interface Temperatures
Authors: Cook N. H. , Bhushan B.
Published: November 2010

An analysis is proposed for estimating the average interface temperature rise during sliding of two surfaces. The basic model includes surface topography statistics, frictional conditions, the effective surface hardness, and thermal parameters. In 75 percent of the material pairs studied, the analysis gives fairly good results. It appears applicable to either dry or lubricated surfaces.
A Fluidity-Temperature Relationship for Liquids
Authors: Ford T. F. , Singleterry C. R.
Published: November 2010

Many relationships between viscosity or its reciprocal, fluidity, and temperature have been proposed for liquids. None except the empirically modified ASTM chart have proven satisfactory over extended temperature ranges. We here note that by plotting the kinematic fluidity (φkin) against the square of the absolute temperature (deg K2) we obtain linear relationships for a wide variety of organic liquids at kinematic viscosities less than about 1.67 centistokes (or fluidities above about 0.60 reciprocal centistokes). The generality of the relationship appears to justify the use of the equation, φkin=a+bT2, as an interpolation formula for organic liquids in the low viscosity region.
On the Lubrication of Heavily Loaded Cylindrical Surfaces Considering Surface Deformations and Solidification of the Lubricant
Authors: Jacobson Bo
Published: November 2010

Lubrication of a line contact between two cylinders is studied. The viscosity of the oil is assumed to vary with pressure and temperature. The oil is assumed to solidify at a certain pressure, which is dependent on the temperature. The solidified oil is assumed to have a shear strength independent of pressure and temperature. Continuity conditions for the cavitation boundary, the boundary between liquid oil and solidified oil, and the boundary between sliding and nonsliding solidified oil are given. Numerical calculations of height functions, pressure distributions, and load capacities are made for the isothermal case. Theoretical and experimental pressure fields and height functions are compared.
A Systematic Study of Turbulent Film Flow
Authors: Hirs G. G.
Published: November 2010

Turbulent film flow theories can only be verified on the basis of a large number of experimental results. Since it will be useful to handle these experimental results more or less systematically and to get some idea of the amount of work yet to be done, the first objective of this paper is to set up a classification system for turbulent film flow experiments. The second objective is to verify the bulk flow theory on the basis of the limited number of experimental results available in the literature and to show this theory to be compatible with these results.
A Critical Examination of the Elastohydrodynamic Criterion for the Scoring of Gears
Authors: Finkin E. F. , Gu A. , Yung L.
Published: November 2010

A critical examination is made of the concept that gear scoring occurs when the EHD film thickness is less than several times the combined surface roughness. The well known experimental data of Borsoff, Borsoff and Godet, and Ku and Baber is analyzed using advanced EHD computational techniques. The study finds: (a) Gear scoring occurs under fully boundary-lubricated conditions and not even close to the breakdown of the EHD film. (b) Isothermal calculations of minimum EHD film thickness are in error both in magnitude and in trend with failure velocity. An analysis which takes thermal effects into account must be used. (c) Pitch point EHD film thickness does not reliably represent minimum EHD film thickness and therefore cannot be substituted for it. (d) The peak Hertz contact stress in a gear mesh may be significantly understated if calculated only at the pitch point.
Dynamic Characteristics of Air-Lubricated Slider Bearing for Noncontact Magnetic Recording
Authors: Ono K.
Published: November 2010

This paper analyzes stability and dynamic response of air-lubricated slider bearing in magnetic recording storage. Dynamic pressure distribution of air film is calculated in frequency domain by small perturbation method and finite difference method. Dynamic response of the slider spacing is obtained not only when the moving recording surface vibrates in the parallel mode but also when the recording surface has a small sinusoidal wave. Stability threshold and onset frequency are presented for three types of slider motion. Based on the analytical results design method for high performance slider and allowable level of the motion of the recording surface are discussed. Experimental agreement with analytical frequency response of slider spacing is obtained and the effect of suspension arm on slider dynamics is discussed.
Prediction of Rolling Contact Fatigue Life in Contaminated Lubricant: Part I—Mathematical Model
Authors: Tallian T. E.
Published: November 2010

In this first part of a two-part paper, a mathematical model is presented for the prediction of spalling fatigue life in rolling bearings, which operate in contaminated lubricant, resulting in denting damage of the rolling surfaces. Five damage accumulation cases are treated: (I) Early or pre-existing damage; (II) Linear damage accumulation from constant lubricant contamination; (III) Accelerating damage from progressive wear; (IV) A combination of the above; and (V) Damage leveling off during stress cycling. Cases (I)-(III) lead to Weibull distributions of fatigue life, the others to more complex distributions. Experimental corroboration and application examples of the model are presented in Part II [16] of this paper.
Journal Bearing Impedance Descriptions for Rotordynamic Applications
Authors: Childs D. , Moes H. , van Leeuwen H.
Published: November 2010

Bearing impedance vectors are introduced for plain journal bearings which define the bearing reaction force components as a function of the bearing motion. Impedance descriptions are developed directly for the approximate Ocvirk (short) and Sommerfeld (long) bearing solutions. The impedance vector magnitude and the mobility vector magnitude of Booker are shown to be reciprocals. The transformation relationships between mobilities and impedance are derived and used to define impedance vectors for a number of existing mobility vectors including the finite-length mobility vectors developed by Moes. The attractiveness and utility of the impedance-vector formulation for transient simulation work is demonstrated by numerical examples for the Ocvirk “π”, and “2π” bearing impedances and the cavitating finite-length-bearing impedance. The examples presented demonstrate both bearing and squeeze-film damper application. A direct analytic method for deriving a complete set of (analytic) stiffness and damping coefficients from impedance descriptions is developed and demonstrated for the cavitating finite-length-bearing impedances. Analytic expressions are provided for all direct and cross-coupled stiffness and damping coefficients, and compared to previously developed numerical results. These coefficients are used for stability analysis of a rotor, supported in finite-length cavitating bearings. Onset-speed-of-instability results are presented as a function of the L/D ratio for a range of bearing numbers. Damping coefficients are also presented for finite-length squeeze-film dampers.
Thermoelastic Effects in Frictionally Heated Line Contact of Slablike Bodies
Authors: Heckmann S. R. , Burton R. A.
Published: November 2010

Many sealing configurations incorporate the geometry of line contact on bluff, slablike bodies. When sliding speed is sufficiently high along or across the line of contact, instabilities may arise from interactions of thermal expansion, elastic deformation and frictional heating. These lead to concentrated contact with elevated temperatures and pressures. Previous studies have been largely restricted to two-dimensional models of such contact. The present study shows how those earlier results must be modified to apply to the more realistic geometry, and show also that the principal features of the interactions are the same in both geometries.
On the Roughness Effect in Hydrodynamic Lubrication
Authors: Chow P. L. , Saibel E. A.
Published: November 2010

Considerable work is being devoted to the influence of surface roughness on load carrying capacity of a bearing in hydrodynamic lubrication. These efforts are mainly concerned with the deviation of the mean pressure from that developed when the surfaces are smooth. These calculations are based on the Reynolds equation with assumptions which by various methods reduce the problem to one with one-dimensional randomness. In this paper it is shown that these current procedures are not valid unless certain stringent conditions are met. To estimate the magnitude of the roughness effect on the load carrying capacity, the upper bounds to the absolute mean deviation and the root mean square deviation of a normalized load carrying capacity from the smooth case is obtained for a general one-dimensional problem valid for an arbitrary distribution. It is found that the upper bound depends critically on the behavior of the autocorrelation of the roughness. The result for the mean deviation is illustrated by a slider bearing with plane mean surfaces.
The Effect of Viscous Shear Heating on Both Film Thickness and Rolling Traction in an EHL Line Contact—Part I: Fully Flooded Conditions
Authors: Goksem P. G. , Hargreaves R. A.
Published: November 2010

A theoretical analysis of both fully flooded rolling traction and film thickness in an EHL line contact is described and modified formulas for fully flooded isothermal conditions are presented. These are compared with the Grubin, Dowson, and Higginson film thickness formulas, and the rolling traction theory by Archard and Baglin (1975). The effect of viscous shear heating in the inlet region has been investigated and new equations for both fully flooded film thickness and rolling traction, including this thermal effect, are introduced. These equations predict significant reductions in both film thickness and rolling traction, relative to the isothermal case, as speed is increased. Viscous shear heating effect is found to be negligible only at very low rolling speeds. The results of the theoretical analysis compare well with experimental data presented by Dyson, Naylor, and Wilson (1966) and Adams and Hirst (1973).
Lubricant-Breakdown in Instrument Ball Bearings
Authors: Kingsbury E. P.
Published: November 2010

A testing scheme is described for short-term evaluation of lubricant-breakdown rate in starved elastrohydrodynamic (EHD) rolling contacts. It is shown that the rate is strongly influenced by the amount of lubricant available to the contacts, and by certain chemical treatments of the surfaces. Several surface conditions are evaluated for their effect on degradation rate.
An Experimental Investigation of the Effect of Misalignment and Directionality on the Performance of an Externally-Pressurized, Orifice-Compensated Air Journal Bearing
Authors: Markho P. H. , Grewal S. S. , Stowell T. B.
Published: November 2010

The study described in this paper aims to quantify the effects of misalignment and directionality on the important performance characteristics of a double-plane admission bearing having a length to diameter ratio of unity. The results clearly demonstrate that misalignment does not seriously impair the bearing performance, as long as due allowance is made for its effect on clearance at the bearing ends. In practice, this impairment would rarely exceed 10 percent. The effect of directionality is also found to be of the same order of magnitude.
Fluid-Film Flows of Differential Fluids of Complexity n Dimensional Approach—Applications to Lubrication Theory
Authors: Bourgin Patrick
Published: November 2010

An isothermal theory of fluid-film flows of differential fluids of complexity n is developed on the basis of a complete dimensional analysis. Within that particular geometrical configuration and provided that the Deborah number is small, such fluids cannot be distinguished from the far more special Rivlin-Ericksen material of complexity 3. It is shown afterwards that the use of a method of resolution similar to that of Reynolds requires to reduce the field of rheological models or the number of geometrical dimensions. The corresponding “generalized Reynolds’ equations” are then deduced: one in 3 dimensions, available for general viscous fluids; one in 2 dimensions, available for Stokesian fluids.
Exact Two-Dimensional Analysis of Circular Disk Spiral Groove Bearing (Part I)
Authors: Murata S. , Miyake Y. , Kawabata N.
Published: November 2010

Basic equations and idea of the method are described concerning the new two-dimensional theory of thin fluid film of spiral groove bearings. Two-dimensional inviscid flow theory of circular wing lattice is the basis of the proposed method. Detailed technique to perform numerical calculation has been established utilizing singularity method. Two-dimensional pressure formation of the fluid film is calculated together with load carrying capacity.
Dynamics of Neutrally Buoyant Inflated Viscoelastic Tapered Cantilevers Used in Underwater Applications
Authors: Modi V. J. , Poon D. T.
Published: November 2010

The paper investigates statics and dynamics of neutrally buoyant inflated viscoelastic tapered cantilevers used as structural members in underwater platforms. In the beginning, the static flexural behavior of the beam is studied using the three-parameter viscoelastic solid model which yields material properties for the mylar-polyethylene-mylar plastic film used. Results of a detailed experimental program are also presented to substantiate validity of the analytical model. This is followed by free vibration analyses of the inflated cantilevers in the ocean environment. The elementary beam theory is used to predict their natural frequencies. Finally, the dynamical response of the uniform and tapered cantilevers to root excitation, at the fundamental wave frequency and its second harmonic, is studied. The governing nonlinear equations are analyzed by taking two terms of the assumed Fourier series solution. Results suggest that for the case of the simple harmonic excitation, the nonlinear hydrodynamic drag introduces no superharmonic components into the response. For low forcing frequencies typical of the ocean environment, an increase in taper ratio tends to reduce the tip amplitudes. However, for frequencies above the fundamental, the response characteristics are completely reversed. The analysis provides valuable information concerning the system parameters leading to critical response and hence should prove useful in the design of such inflatable members.
A Research on High-Speed Hobbing With the Carbide Hob
Authors: Ainoura M. , Sakuragi I. , Yonekura M. , Nagano K.
Published: November 2010

If we could hob steel gears at high speed and full depth in a single pass (for the allowance of machining) using carbide hobs, “Gear Producing” capacity could be remarkably increased. However, the defects with carbide hobs are seen in frequent chipping and expensiveness. Using the comparatively less expensive carbide-tipped hobs, the authors have carried on a number of experiments in terms of the design, the special carbide quality for carbide-tipped hobs, and the improvement in manufacturing the hobs. And here at last we have the developed Carbide Tipped Hob without any chipping. Moreover, the authors have developed a new carbide hobbing machine equipped with a device which absorbs shock and vibration of the cutting blade during hobbing gears. The theme of this research is to introduce the points about the developed mechanical technique of hobbing.
Stability of a Simply-Supported Beam Subjected to Randomly Spaced Moving Loads
Authors: Kurihara M. , Shimogo T.
Published: November 2010

In this paper, vibration problems of a simply-supported elastic beam subjected to randomly spaced moving loads with a uniform speed are treated under the assumption that the input load sequence is a Poisson process. In the case in which the inertial effect of moving loads is taken into account, the stability problem relating to the speed and the mass of loads is dealt with, considering the inertia force, the centrifugal force, and the Coriolis force of the moving loads. As an analytical result a stability chart of the mean-squared deflection was obtained for the moving speed and the moving masses.
Dynamic Analysis of an Assembly of Shrouded Blades Using Component Modes
Authors: Srinivasan A. V. , Lionberger S. R. , Brown K. W.
Published: November 2010

The problem of vibratory behavior of an assembly of shrouded fan blades is examined. The point of view that forms the basis for the analysis is that the vibration characteristics of an assembly of blades can be predicted from a knowledge of vibration characteristics of its components. Clearly, linear behavior is assumed. A viscous type of damping mechanism is included to account for any energy dissipation due to vibratory rubbing action at shroud interfaces. As the component modes are computed with a single blade and shroud modelled with plate elements, the extent of chordwise motion in different modes is examined. Numerical results of an application of the analysis to a typical fan design are included.
The Design of Current Carrying Mechanisms Operating in a Magnetic Field
Authors: Reed W. S. , Smith W. D.
Published: November 2010

Extensions to earlier work presented on the electrodynamics of a planar mechanism moving in a magnetic field are considered in this paper. The effects of damping and self-fields are added to the equations of motion. These equations are then integrated numerically for an example design having a constant torque input, a constant angular velocity input, and a constant voltage input. The results of numerous parametric studies are then presented as a basis for design of these devices. Finally the results of experimental work are presented in order to verify the numerical model.
An Electrical Method for Failure Prediction in Ductile Machine Elements at Elevated Temperatures
Authors: Kurajian G. M. , Na T. Y.
Published: November 2010

This paper provides the designer with an electrical method for failure prediction in ductile machine elements operating at elevated temperatures from room through the creep range. The law of conservation of energy, electrical considerations, and electrical properties are employed to result in a formulation. The formulation enables the designer to obtain, or verify, and then employ the critical stress value he requires in the design of a particular machine element operating at a given elevated temperature. It is shown that this critical stress value may be calculated simply by knowing the electrical resistivity value at the operating temperature, and the critical stress and electrical resistivity values at a datum (room) temperature. Specific applications are taken for various categories of steels with very good agreement between the theory and experimental data. The formulation is deemed to be applicable to other ductile metals as well.
Multistage Geared Geneva Mechanism
Authors: Yang A. T. , Hsia L. M.
Published: November 2010

Design concepts for an n-stage geared Geneva mechanism, which is an assembly of n Geneva mechanisms connected by (n−1) gear trains, are proposed in this paper. The dwell time produced by the system is a function of (n−1) phase angles, the combined number of slots on all the wheels and the number of pins on all cranks in the system. The introduction of phase angles into the family of design parameters is highly significant: it gives the engineer an added dimension in the design of intermittent mechanisms and it gives him the flexibility to fine-tune their dwell time. For illustrative purposes, the derivation for the dwell time and the kinematic analysis of a two-stage geared Geneva mechanism are treated in detail. It is hoped that the results, which are presented in the form of charts and graphs, would be useful for the rational design of intermittent mechanisms.
Determination of the Critical Operating Speeds of Planar Mechanisms by the Finite Element Method Using Planar Actual Line Elements and Lumped Mass Systems
Authors: Kalaycioglu S. , Bagci C.
Published: November 2010

It has been a well-established fact that dynamic systems in motion experience critical speeds, such as rotating shafts and geared systems whose undeformed reference geometry remain the same at all times. Their critical speeds are determined by their natural frequencies of considered type of free vibrations. Linkage mechanisms as dynamic systems in motion change their undeformed geometries as function of time during the cycle of kinematic motion. They do also experience critical operating speeds as rotating shafts and geared systems do, and their critical speeds are determined by the minima of their natural frequencies during a cycle of kinematic motion. Such a minimum occurs at the critical geometry of a mechanism, which is the position at which the maximum of the input power is required to maintain the instantaneous dynamic equilibrium of the mechanism. Actual finite line elements are used to form the global generalized coordinate flexibility matrix. The natural frequencies of the mechanism and the corresponding mode vectors (mode deflections) are determined as the eigen values and eigen vectors of the equations of instantaneous-position-free-motion of the mechanism. Method is formulated to include or exclude the link axial deformations, and apply to any number of loops having any type of planar pair. Critical speeds of planar four-bar, slider-crank, and Stephenson’s six-bar mechanisms are determined. Experimental results for the four-bar mechanism are given. Effect of axial deformations and link rotary inertias are investigated. Inclusion of link axial deformations in mechanisms having pairs with sliding freedoms is seen to predict critical speeds with large error.
Partial Dynamic State Synthesis by Use of Mass Parameters in a System Coupler Link
Authors: Elliott J. L. , Tesar D. , Matthew G. K.
Published: November 2010

One of the primary objectives of synthesis is the reduction of the number of controlling parameters facing the designer in the optimization phase of the design process while at the same time forcing the remaining parameters to generate solutions which are acceptable in some prescribed sense. In this paper, the four mass parameters m, k, u, v of any link moving in coplanar motion are used to meet specified torque (or energy) levels or specified shaking moment values for up to four positions of the system. The origin of these specifications for the synthesis procedure may be due to inertia in the rest of the system or due to a work function such as those generated by springs. The dimensions of the mechanism are considered to pre-exist or are due to an earlier motion synthesis stage of the design [5]. Springs may have been obtained by a synthesis procedure outlined in reference [6]. Finally, once the values of m, k, u, v for one link are met by means of procedures introduced here, they may then be used directly in shaking force criteria of Berkof and Lowen [2] to further balance the system or those in reference [3] for additional refinement. The total objective of this serial use of synthesis procedures is to minimize the number of independent design parameters while still retaining a set of solutions containing the global optimum in terms of some prescribed qualitative requirements. Some of these qualitative criteria were outlined in the very interesting and complete work [4] on characterization of the dynamic state of real machines by Artobolevskii and Loschchinin. The synthesis procedure is validated by a design example of a throwing mechanism. The object being thrown is specified in four finitely separated velocity states of an existing mechanism. The resulting dynamic response of the system meets these arbitrary specifications within an error of 0.05 percent.
Constrained Balancing Techniques for Flexible Rotors
Authors: Pilkey W. D. , Bailey J. T.
Published: November 2010

Several methods for identifying the unbalance causing deflection of a flexible rotating shaft are developed. All methods presented permit the magnitude of the balance weights to be controlled. The formulations may be grouped into categories of either time independent schemes or time dependent schemes. The formulations are also characterized by the type of measure adopted for the identification, e.g., minmax or least squares fits. Numerical results are presented for some of the methods.
Low-Cycle Fatigue and Ultimate Strength Related to Gear Design
Authors: Moore W. L.
Published: November 2010

This paper describes the development of a method for assessing the ultimate tensile and limit load strength values required by MIL-A-8860 (ASG) [1] for aircraft actuator gear teeth, and the subsequent effect of a few very-high-load cycles with regard to bending and surface fatigue life. American Gear Manufacturers Association (AGMA) rating procedures are found to require modification for pitch point contact, modulus of rupture, higher contact ratios, and the extension of S-N curves to one load cycle. These modified rating procedures, combined with qualifying statements, provide for relatively simple calculation. Background and application data are provided for gear teeth under relatively common load conditions that are not included in AGMA standards.
Mechanism Optimization via Optimality Criterion Techniques
Authors: Thornton W. A. , Willmert K. D. , Khan M. R.
Published: November 2010

Presented in this paper are two new design techniques, based on optimality criteria, for selecting the cross-sectional sizes of the links within a mechanism. The objective is to minimize weight subject to stress and displacement (deformation) constraints. The mechanisms are assumed to be undergoing vibrational effects. These new optimality criterion methods are compared with a standard SUMT technique of nonlinear programming.
Limit Positions of Spatial Linkages via Connectivity Sum Reduction
Authors: Baker J. Eddie
Published: November 2010

Several methods are available for determining the configurations of spatial linkages at which joint freedoms take limiting values. These approaches emphasize various characteristics of joint limit positions, but none uses directly the fact that the remainder of the linkage has transient mobility at the instant when the joint being considered is locked. It is this feature which is utilized here to show, by means of a range of examples, how limiting configurations may be determined.
Contact Problems in Wire Ropes
Authors: Karamchetty S. D. S. R. , Yuen W. Y.
Published: November 2010

Forces are transmitted across the contact points in a wire rope. Wires tend to bend in between the contact points and they tend to nick and cut at the contact points. A computer method is discussed to determine the contact points in a wire rope. In a geometrically perfect wire rope with the wires laid as double-helices no contact point occurs. But in an actual rope, the geometry changes while laying and due to loading, thus permitting contacts at a number of points. The paper discusses such contact points. Some refinements of the basic model were considered and results presented.
Pressure-Vessel Steels: Promise and Problem
Authors: Gross J. H.
Published: November 2010

During the past 25 years, numerous pressure-vessel problems have been solved, but in many instances the solutions have led to other problems. Currently, promising developments in pressure-vessel steels are providing such solutions and such additional problems with respect to fabrication and various failure modes. With respect to fabrication, lamellar tearing is being minimized by special melting and solidification practices. However, continuous casting and electroslag-remelting of slabs are currently limited in plate size that can be produced. With respect to bursting, recent studies indicate that high-yield-strength steels have higher burst-strength indices than lower-strength steels even for vessels with nozzles and with notches up to 25 percent of the wall thickness. Strength and therefore resistance to bursting can be increased without loss in toughness through new control-rolling practices, except that these practices are limited to plates up to 3/4 in. thick. New high-toughness line-pipe steels are now available that should be very attractive for pressure vessels that require very high resistance to shear tearing. These low-sulfur steels may be somewhat impaired by sensitivity to splitting as a result of the control-rolling practice. To date, steels have not been developed with improved resistance to fatigue failure. Fortunately, pressure vessels have rarely failed by fatigue. Similarly, resistance to failure by environmental effects is not basically improved by steel composition. This is usually the result of difficulty in defining the effects of the numerous environments that may be involved. These steel developments promise continued improvement of pressure-vessel performance, but usually are accompanied by problems that present new technological challenges.
On the Determination of Effective Elastic-Plastic Properties for the Equivalent Solid Plate Analysis of Tube Sheets
Authors: Slot T. , Branca T. R.
Published: November 2010

Practical procedures are described for the evaluation of effective material properties for use in elastic-plastic analyses of perforated plates involving the equivalent solid plate approach. The finite-element method is used to generate numerical solutions that permit these properties to be determined for a given penetration pattern and given base metal properties. An example is treated for the triangular penetration pattern. The results are illustrative of the anisotropy of the equivalent solid material.
Effective Plastic Constants for Perforated Materials
Authors: Porowski J. , O’Donnell W. J.
Published: November 2010

New discontinuous fields of stress are derived for materials perforated in a triangular array of circular holes. These stress fields are applicable for loads of arbitrary bi-axiality and orientation with respect to penetration patterns having moderate to high ligament efficiencies. The corresponding effective plastic constants for the equivalent solid material are derived for use in the limit analyses of structures. The method of constructing these stress fields may also be used for irregular penetration patterns and to evaluate the effect of misplaced holes.
Dynamic Response of an Infinite Beam
Authors: Durlofsky H.
Published: November 2010

Both the exact and an approximate solution for the dynamic response of an infinite Bernoulli-Euler beam under an instantaneously applied, concentrated load are presented in this paper. The exact solution is obtained by means of complex Fourier transforms. The approximate solution is obtained by assuming the dynamic response has the form of a deflected infinite beam on an elastic foundation, with wavelength a function of time. This assumption is motivated by the similarity between the dynamic response problem and the problem of an infinite beam on an elastic foundation. A governing equation for the wavelength in the assumed response is derived by application of the principle of conservation of energy, and solved by straightforward methods. A comparison of the two solutions shows good agreement near the point of loading. Results applicable to pipe whip problems are presented.
Probabilistic Assessment of Low-Cycle Fatigue Behavior of Structural Welds
Authors: Ellingwood B. R.
Published: November 2010

Low-cycle fatigue behavior of structural welds is dependent on material characteristics, geometry at fatigue-critical locations, loading history including residual stresses, and environment. Since these factors may occur randomly and contribute significantly to the uncertainty in design, probabilistic methods are required for their analysis and for the development of appropriate fatigue design criteria. The analysis and prediction of low-cycle fatigue behavior of structural welds is discussed in terms of the foregoing factors. Consideration of statistical uncertainties in the various parameters enables prediction and interpretation of variability in fatigue response, and permits selection of design allowables which correspond to a small probability of unacceptable fatigue performance. These techniques are shown to provide a systematic basis for assessing fatigue reliability of structural welds.
An Examination of a Proposed Method for Evaluating Nonlinear Effects in Fracture Assessment
Authors: Adams N. J. I. , Munro H. G.
Published: November 2010

A proposal put forward by Liebowitz and Eftis suggests a method of accounting for nonlinear behavior observed in fracture. A simple model analysis of a center crack sheet and supporting experimental results, indicate that the corrected toughness based on load point displacement will not be single valued for a specific material. It is established that both the correction factor and deviation from linearity due to cracktip yielding vary with specimen length. Additionally, tests on compact tension specimens indicate that difficulties exist when trying to correlate corrected toughness values from one specimen configuration to another.
On the Gasdynamics of Running Ductile Fracture in a Pressurized Line Pipe
Authors: Parks D. M. , Freund L. B.
Published: November 2010

Developments in the modeling of the gasdynamics associated with running ductile fracture in pressurised line pipe are reviewed and critically examined. It is argued that existing models of gas escape through a flaring axial crack in a pipe may not be generally applicable. A new model of gas escape, based on two-dimensional flow and directed toward large crack opening situations, is presented, and results obtained with this model compare favorably with experiments. Implications of the present results concerning the driving force for crack propagation are discussed.
Embedded Elliptical Crack at a Corner
Authors: Kobayashi A. S. , Emery A. F. , Love W. J. , Antipas A.
Published: November 2010

A procedure for estimating the stress intensity factor of an embedded elliptical crack near the corner in a region of high stress concentration such as pressurized or thermally shocked nozzle-to-cylinder junction is discussed. The procedure is then used to analyze two hypothetical embedded circular cracks near the corner of a nozzle-to-cylinder junction where stress distributions in the uncracked junction are known. Also shown are two new stress intensity magnification factors for two embedded elliptical cracks, i.e., b/a = 0.2 and 0.982, close to a free corner, i.e., a/h = b/h = 0.9.
Design Curves for Stress Analysis of U-Tube Heat Exchanger Tubesheet With Integral Channel and Head
Authors: Soler A. I. , Soehrens J. E.
Published: November 2010

A U-tube heat exchanger with integral channel, head and unperforated rim is investigated to establish design rules based on application of elastic plate theory. The effect of tube bending resistance, unperforated rim, channel and head on the rigidity of the tubesheet are considered in the analysis. The solution of the equations for the configurations are presented in compact dimensionless form well suited for detailed parameter study. Numerical results are obtained for typical parameter ranges and some comparisons are made with the well-known TEMA formula. The final design curves and formulas are in a form suitable for consideration as a design code.
High Temperature Properties and Constitutive Equations for 1 Cr-1/2 Mo Steel
Authors: Long Saphura S.
Published: November 2010

This paper presents the tensile, creep, rupture, and fatigue properties of 1 Cr-1/2 Mo steel. Tensile tests were conducted over a temperature range of 70–1150 F (21 to 621 C). Creep-rupture tests were run for the stress range of 10–56 ksi (69 to 386 MPa) at temperatures of 850 to 1150 F (454 to 621 C) and the strain-controlled fatigue tests were run to 145,000 cycles at room temperature. Results of the tensile tests are presented as stress-strain curves and as constitutive equations. The parameters in the equations were obtained by a nonlinear least-squares technique assuming an origin offset power law formulation of true stress as a function of true strain. The creep analysis resulted in a creep constitutive equation, isochronous stress-strain curves, and correlations between rupture time, time to onset of tertiary creep, and minimum creep rate. The constitutive equation is a two-term rational polynomial with a steady-state term which describes primary plus secondary creep. Isochronous stress-strain curves were developed from the creep equation and extrapolated to 100,000 hr. Over the measured range, the isochronous curves showed excellent agreement with the actual data. In absolute strength level, both the rupture stress and minimum creep rate data show that this particular heat of material lies in the upper part of the scatter band for 1 Cr-1/2 Mo steel. The room temperature cyclic stress-strain curves show the alloy strain softens in the low strain region and strain hardens in the high-strain region. The fatigue behavior is typified by a linear relationship between both elastic and plastic strain range and cycles to failure on a log-log basis. The fatigue results conform reasonably well to predictions from Manson’s method of universal slopes.