bluuebunny/crossref_metadata_2025 huggingface dataset:
Clearance, Leakage, and Contact Temperature in a Thermoelastically Deformed Seal-Like Configuration
Authors: Burton R. A. , Nerlikar V.
Published: November 2010

Equations are derived for clearance, leakage, and contact temperatures for conditions where initially flat rubbing surfaces are deformed thermally to produce a sequence of equally spaced contact patches, separated by regions where the surfaces withdraw from one another. One paradoxical result is that increased contact pressure or preload on the seal increases leakage when sliding takes place above a critical speed.
On the Performance of Journal Bearings Under Conditions of Film Rupture, Part II
Authors: Crosby W. A. , Badawy E. M.
Published: November 2010

An analytical analysis of journal bearing performance under conditions of film rupture by separation and by cavitation is performed. The ruptured region is considered to have an infinite number of cavities. The boundary condition of Reynolds’ equation at the trailing edge is influenced by the bearing’s operating characteristics and the method of oil admission. A variational solution is given in order to extend the applicability of the boundary conditions to bearings of finite length.
The Analysis of the Lubrication of a Flexible Journal Bearing
Authors: Conway H. D. , Lee H. C.
Published: November 2010

An analysis is made of the effects of flexibility on the lubrication of a loaded journal bearing. Numerical and graphical results are presented for (a) the pressure distributions in the oil film, (b) the thickness variation of the film, (c) the magnitude and direction of the load applied to the bearing, and (d) the frictional forces in the bearing. The oil is first assumed to be isoviscous and the above data are found to depend on the values of the two independent parameters C0=6Uη0R2t(1−ν02)/Ec3 and ε = e/c (see Nomenclature). The analysis is then extended to the case of a pressure-dependent viscosity η = η0eαp oil, and the data found to depend on the values of the three independent parameters C0, ε, and β=Eeα/t(1−ν02).
Two Anomalies of the Short Bearing Theory
Authors: Fazekas G. A.
Published: November 2010

The reciprocal of eccentricity gives a near linear plot against the reciprocal of the Load Number. It holds over most of the important region. It brought to light two anomalies inherent in Ocvirk-DuBois theory, and the way to remove at least one.
Pressure Drop Due to Inertia Forces in Step Bearings
Authors: Constantinescu V. N. , Galetuse S.
Published: November 2010

A study of the pressure distribution in a step bearing is presented, including inertia effects, by assuming that (1) a simplified pressure differential equation, (2) a global momentum balance or (3) an energy equation can be written in the vicinity of the step. All three methods give comparable results for small and moderate film thickness ratios, while satisfactory agreement with existing numerical data and some experimental data may be emphasized. It is pointed out that under certain circumstances, such as strong reverse flow occurring for larger film thickness ratios, the flow is decelerated instead of being accelerated across the step. As a consequence a pressure rise instead of a pressure drop may occur due to inertia, reaching a limiting value equal to half of the dynamic head corresponding to the sliding velocity (when the minimum film thickness in the land area becomes very small).
Application of Finite Element Methods to Lubrication: Squeeze Films Between Porous Surfaces
Authors: Eidelberg B. E. , Booker J. F.
Published: November 2010

Finite element methods are applied to the analysis of squeeze films between porous surfaces. Planar elements in the fluid film region are joined with solid elements in the porous region to ensure continuity of pressures and flows. The formulation is valid for problems with irregular geometry and nonhomogeneous anisotropic permeability. A simple example with uniform properties demonstrates convergence to a previous analytical solution. More complex examples illustrate the power and versatility of the method.
Fluid Inertia Effects in Non-Newtonian Squeeze Films
Authors: Elkouh A. F.
Published: November 2010

The momentum and energy integral methods are used to study the effect of inertia on the behavior of a non-Newtonian (Power Law) squeeze film. It is shown that the inertia correction in the load capacity is more significant for pseudoplastic fluids, n < 1. For a Newtonian fluid, n = 1, the expressions obtained by using the energy integral method yield results identical to those obtained from a first-order iteration, and which are in good agreement with available experiments.
The Hydrodynamics of a Plug Bearing
Authors: Etsion I. , Pinkus O.
Published: November 2010

The notion of a “plug” bearing taken up in this work refers to bodies moving within tight circular conduits. Our interest lies in the hydrodynamic film generated in the narrow interspace between body and wall under conditions of an incompressible fluid and unequal boundary pressures. For generality rotation as well as translation is considered. Performance characteristics are given for nontilting frustums, both diverging and converging in the direction of motion. It is shown that for a given body shape the amount of leakage past the plug is the same regardless of its orientation. However, with geometries whose film increases in the direction of plug velocity there is a wide range of operating conditions when the resultant force is such as to drive the body against the wall of the conduit; over the same range, shapes which produce films decreasing in the direction of motion yield a floating force.
Elastohydrodynamic Lubrication of Spherical Surfaces of Low Elastic Modulus
Authors: Biswas S. , Snidle R. W.
Published: November 2010

The paper presents a numerical solution for the elastohydrodynamic lubrication of low modulus point contacts which is broadly equivalent to the theory of Grubin for materials of high elastic modulus. The theoretical results obtained for the variation of minimum film thickness using this approach are therefore expected to apply to conditions of high load and low speed. For less severe conditions in which elastic deformation is less significant an alternative approach has been developed. Results of this analysis show the transition from undeformed to heavily loaded conditions. The effect of lubricant starvation has been examined for heavily loaded conditions and the theoretical results are compared with those obtained previously for high elastic modulus point contact.
A Numerical Procedure for Designing Profiled Rolling Elements
Authors: Oh K. P. , Trachman E. G.
Published: November 2010

A numerical procedure is developed for studying the pressure and stress distributions resulting from the contact of two elastic bodies. The pressure distribution is obtained by a quadratic programming method such that the resulting displacements satisfy the geometric constraints of the contact problem, and the bodies are in a state of minimum potential energy. The potential method is used to calculate the subsurface stresses due to a constant pressure over a rectangular element. The stresses due to the contact pressure are then obtained by superposition of the contributions of all the elements in the contact area. A small number of elements (5 × 5) provides pressure and stress solutions within two percent of the closed-form solution for quadratic surfaces. For surfaces with abrupt changes in geometry, more elements are required. This procedure can be used to locate an optimum profile for rolling element bearings.
Reliability of Railroad Roller Bearings
Authors: McGrew J. M. , Krauter A. I. , Moyar G. J.
Published: November 2010

Bearing defect data from 8,000 railroad roller bearings are analyzed to determine their defect modes and defect rate distributions. Cone bore growth, brinelling, and fatigue are identified as the predominant defect modes as bearings age at least through age 12 years. The results of the study show that, after only two years of service, ten percent of all railroad roller bearings exhibit a defect of one type or another for which at least one component would be condemned if it were in a rework shop. The present AFBMA method of calculating fatigue spalling, modified to account for lubricant film thickness effects, correlates reasonably well with the observed incidence of spalling (10 percent fatigue life of about 11 years). The problem lies in the fact that the AFBMA calculation procedure ignores the other competing defect modes which contribute far more to the overall defect rate than does spalling. The relationship between “defect rate” and “failure rate” is not direct, of course, and an examination of “condemning limit” definitions relative to the progression of bearing failure in service is needed.
On the Natural Lubrication of Synovial Joints: Normal and Degenerate
Authors: Mansour Joseph M. , Mow Van C.
Published: November 2010

Fluid flow and mass transport mechanisms associated with articular cartilage function are important biomechanical processes of normal and pathological synovial joints. A three-layer permeable, two-phase medium of an incompressible fluid and a linear elastic solid are used to model the flow and deformational behavior of articular cartilage. The frictional resistance of the relative motion of the fluid phase with respect to the solid phase is given by a linear diffusive dissipation term. The subchondral bony substrate is represented by an elastic solid. The three-layer model of articular cartilage is chosen because of the known histological, ultrastructural, and biomechanical variations of the tissue properties. The calculated flow field shows that for material properties of normal healthy articular cartilage the tissue creates a naturally lubricated surface. The movement of the interstitial fluid at the surface is circulatory in manner, being exuded in front and near the leading half of the moving surface load and imbibed behind and near the trailing half of the moving load. The flow fields of healthy tissues are capable of sustaining a film of fluid at the articular surface whereas pathological tissues cannot.
Optical Measurement of Oil Film Thickness Between Rollers
Authors: Willis T. , Seth B.
Published: November 2010

Previous research has established that the laser beam diffraction method can be used for measurement of film thicknesses between two adjacent flat surfaces. This paper describes further experimentation on this method, where oil film thicknesses between rollers is measured. Calibration curves are obtained between the experimental (set) gap and the gap dimensions which are deduced from the diffraction patterns when the laser beam is passed through the film. These set versus calculated film thickness curves are extremely linear for films which are less than 1 mm depth, the coefficients of correlation with straight lines being close to unity. Data based upon several oils used with 76.2 mm dia rollers are presented and empirical equations established. These equations allow the researcher to obtain the film thickness between the rollers in terms of oil properties (density, viscosity and refractive index) and the geometry of the light beam (wavelength, distance from oil film to diffraction screen, and diffraction pattern bandwidth). The empirical constants in the equations for film thickness appear to apply to specific oil types, and remain the same for each family or group of oil used. The groups used here were SAE 10 through 40, low viscosity index and high viscosity index groups. Oil films from 7.62 × 10−3 mm up to 76.2 × 10−3 mm thickness were measured using this method.
An Average Flow Model for Determining Effects of Three-Dimensional Roughness on Partial Hydrodynamic Lubrication
Authors: Patir Nadir , Cheng H. S.
Published: November 2010

A new approach is utilized to determine the effects of surface roughness on partially lubricated contacts. An average Reynolds equation for rough surfaces is defined in terms of pressure and shear flow factors, which are obtained by numerical flow simulation. Through the use of measured or numerically generated rough surfaces, any three dimensional roughness structure can be analyzed with this method. The average Reynolds equation is obtained for isotropic surfaces, and for surfaces with directional patterns. The flow factors for these surfaces are expressed as empirical relations in terms of h/σ and a surface characteristic γ defined as the ratio of x and y correlation lengths.
Flow Characteristics and Pressure Head Build-Up at the Inlet of Narrow Passages
Authors: Tipei Nicolae
Published: November 2010

Geometric discontinuities of the solid boundaries at the inlet of narrow passages, as for slider bearings, piston rings etc. generate local phenomena where inertia plays an important role. Assuming the lubricant is carried by a moving surface towards the contact zone, the flow characteristics at a short distance ahead of the inlet are investigated. The velocity distribution across the lubricant layer and the shape of the free surface are analyzed, when the surface tension is taken into account. The differential equation of the free surface shows that the thickness of the liquid layer has a special value (He = 3) at the point where the incoming flow is reversed. The pressure at the inlet of the film is then calculated, in terms of the dynamic pressure of the unperturbed flow. It is shown that the inlet pressure head depends on the shape of the free surface (through He), on the pressure gradient and on Reynolds number. Subsequently, the drag generated by the pressure head is determined. After the flow entering the gap and the expelled flow were obtained, the problem of bearing starvation or flooding was examined, thus leading to a new criterion for lubricant supply conditions.
Hydrodynamic Lubrication and Wear in Wavy Contacting Face Seals
Authors: Lebeck A. O. , Teale J. L. , Pierce R. E.
Published: November 2010

A model of face seal lubrication is proposed and developed. Hydrodynamic lubrication for rough surfaces, surface waviness, asperity load support, elastic deflection, and wear are considered in the model. Predictions of the ratio of hydrodynamic load support to asperity load support are made for a face seal sealing a low viscosity liquid where some contact does occur and surface roughness is important. The hydrodynamic lubrication is caused by circumferential surface waviness on the seal faces. Waviness is caused by initial out of flatness or any of the various distortions that occur on seal ring faces in operation. The equilibrium solution to the problem yields one dimensional hydrodynamic and asperity pressure distributions, mean film thickness, elastic deflection, and friction for a given load on the seal faces. The solution is found numerically. It is shown that the fraction of hydrodynamic load support depends on many parameters including the waviness amplitude, number of waves around the seal, face width, ring stiffness, and most importantly, surface roughness. For the particular seal examined the fraction of load support would be small for the amount of waviness expected in this seal. However, if the surface roughness were lower, almost complete lift-off is possible. The results of the analysis show why the initial friction and wear rates in mechanical face seals may vary widely; the fraction of hydrodynamic load support depends on the roughness and waviness which are not necessarily controlled. Finally, it is shown how such initial waviness effects disappear as the surface profile is altered by wear. This may take a long or short time, depending on the initial amount of hydrodynamic load support, but unless complete liftoff is achieved under all operating conditions, the effects of initial waviness will vanish in time for steady state conditions. Practical implications are drawn for selecting some seal parameters to enhance initial hydrodynamic load support without causing significant leakage.
Methods of Decreasing Wear in Metal-Polymer Contacts
Authors: Belyi V. A. , Kragelskii I. V. , Savkin V. G. , Sviridyonok A. I.
Published: November 2010

In metal-polymer contacts, wear can be decreased either by developing materials which have the required frictional properties before rubbing, or by additives which revise the material surface properties during sliding. Two methods of each type are described. Several polymers were prepared by solidification against other solids which produced special surface structures. Other specimens were prepared by irradiation to change the structure of the polymer. In other experiments, two kinds of additives were incorporated into the surface layers of the polymer. The one is a complex compound which decomposes during sliding and alters the frictional properties. The other is an additive which influenced the transfer by a ‘selective’ mechanism. All of these methods widen the safe range of load and speed for the polymers. In the development of polymeric materials for improving friction and wear behavior, a polymer may be specially prepared before use, or may incorporate additives which alter the surfaces during sliding. Two modifications of polymers of each type are described below and follow upon preliminary work on these products [1–5].
Asperity Interactions In EHD Contacts
Authors: Nagaraj H. S. , Sanborn D. M. , Winer W. O.
Published: November 2010

Infrared temperature measurements, ferrographic analysis, and surface profilimetry were used to monitor asperity interactions in a sliding EHD point contact. The contact temperature and surface profile signals obtained both before and after a run-in period are compared in the frequency domain by means of a Fourier analyzer. The interaction of surface asperities is accompanied by the presence of a high frequency component in the infrared signal. It is also shown that only a relatively narrow band of wavelengths of the surface profile spectrum are relevant in the interaction process.
The Influence of Variable Density and Viscosity on Flow Transition Between Two Concentric Rotating Cylinders
Authors: Li Chin-Hsiu
Published: November 2010

In a journal bearing, the lubrication film can be analyzed by the laminar flow theory if the modified Reynolds number, R*, is small or by turbulent flow theories if R* is very high. R* of 41.17 has generally been quoted as the criterion below which simple laminar film is to be expected. This is a classical value obtained by assuming that the film is isothermal and that the journal and bearing are concentric. In high speed bearings, nonuniform oil film temperatures are generated due to viscous dissipation. This paper studies the influence of the temperature profiles on the onset of instability of the film between two concentric cylinders with small diametrical clearance. Linear and exponential temperature variations of density and viscosity, respectively, are considered. Direct integration coupled with Newton’s iteration is used to solve the eigenvalue problem. Results indicate that the critical modified Reynolds number for an oil film can be lowered significantly from its classical value of 41.17. For a lubricant with a Prandtl number of 200, a modified Reynolds number of about 21 is found to be the critical value for the onset of instability. Therefore, for this type of bearing, the nature of the flow deserves careful examination before laminar flow theory can be applied to the analysis of bearing performance.
An Analysis of Stress Relaxation in Elastico-Viscous Fluid Lubrication of Journal Bearings
Authors: Harnoy A.
Published: November 2010

The hydrodynamic theory of lubrication in journal bearings is extended to elastico-viscous lubricants. The stress relaxation effect upon flow, pressure distribution, friction, and bearing load capacity is considered. This analysis deals with the case of a small relaxation time compared with the transit time required for the lubricant to pass through the bearing. A lubricant model is assumed with a constant relaxation time and without any cross stresses. It is found that the bearing load capacity of an elastic liquid lubrication film is higher than that of a Newtonian one, while the friction torque remains unchanged. Existing experimental studies have shown considerable improvement in journal bearing performance with elastico-viscous lubricants. This analysis suggests stress relaxation to be one of the factors giving rise to this improvement.
Glass Transitions in Lubricants: Its Relation to Elastohydrodynamic Lubrication (EHD)
Authors: Alsaad M. , Bair S. , Sanborn D. M. , Winer W. O.
Published: November 2010

A preliminary investigation into the possible role of glass transition and glassy state behavior of lubricants in EHD contacts is reported. Measurements of the glass transition of lubricants as a function of pressure by two methods are presented along with a discussion indicating possible implications of the results to EHD lubrication.
Wear Mechanism of Unidirectionally Oriented Fiber-Reinforced Plastics
Authors: Tsukizoe T. , Ohmae N.
Published: November 2010

Wear between unidirectionally oriented fiber-reinforced-plastics and mild steel has been investigated. The wear behavior was found to be greatly influenced by the sliding direction, the mechanical properties of fiber-reinforced-plastics and by the tribological properties of fiber-reinforcements or matrices. A summarization of wear-resistance of seven different kinds of fiber-reinforced-plastics signified that the epoxy resin reinforced with high-modulus carbon fibers was the best wear-resistant fiber-reinforced-plastics.
Two Temperature Gradients Model for Friction Failure
Authors: Rozeanu L. , Pnueli D.
Published: November 2010

A model of friction interaction between two surfaces is based on considerations of discrete microscopic asperities at the surface. This model establishes the existence of two temperature gradients in the material: a weak one (10 °K/cm) in the bulk, and a very strong one (106 °K/cm) at the surface. A large number of cases of friction failures, which could not be explained by the classical continuum model; are easily interpreted by the two gradient model. It also becomes clear that the continuum model and the two gradient model are opposite extreme cases, with a whole spectrum of intermediate cases between them.
Strongly Anisotropic Rough Surfaces
Authors: Bush A. W. , Gibson R. D. , Keogh G. P.
Published: November 2010

The statistics of a strongly anisotropic rough surface are briefly described. The elastic contact of rough surfaces is treated by approximating the summits of a random process model by parabolic ellipsoids and applying the Hertzian solution for their deformation. Load and real contact area are derived as functions of the separation and for all separations the load is found to be approximately proportional to the contact area. The limits of elastic/plastic contact are discussed in terms of the plasticity index.
The Influence of Fluid Rheology on the Performance of Traction Drives
Authors: Tevaarwerk J. L. , Johnson K. L.
Published: November 2010

The performance of traction drives depends to a large extent on the rheological properties of the fluid in the EHL contact. Through the use of the recently proposed J + T constitutive equation, the influence of elastic effects in the fluids is examined. The results were compared with those obtained from conventional analysis. It is shown that essentially three regions of influence exist. For small values of spin and side slip the elastic effects in the fluid dominate and no consideration of the spin and side slip is required. At higher values of spin and side slip the elastic effect still exists but slip is influenced by the spin and slide slip. At still higher values of side slip and spin, the elastic effects in the fluid may be neglected. The various boundaries of the regions of influence depend on the aspect ratio of the contact.
Dynamics of Rolling-Element Bearings—Part IV: Ball Bearing Results
Authors: Gupta P. K.
Published: November 2010

Dynamic simulations of the performance of a ball bearing are presented in terms of the general motion as obtained by integrating the differential equations of motion of the various bearing elements. It is shown that bearing misalignment significantly influences the ball/cage and race/cage interaction and, hence, the stability of cage motion. The increased radial to axial load ratios promote skidding which couples with the lubricant behavior to impose accelerations on the ball which ultimately influence the ball/cage interactions. Hence, the lubricant behavior and the large load variation on the balls play dominant roles not only in determining the extent of skidding but also in establishing the overall stability of the cage motion.
The Hybrid Isothermal Air Lubricated Journal Bearing
Authors: Kamala V.
Published: November 2010

This paper analyzes the load-carrying capacity of the hybrid air lubricated journal bearing. Assuming a small eccentricity ratio, a first order perturbation solution is obtained. The air is fed to the bearing through inherent restrictor with feeding holes distributed around the circumference in one, two, and three feeding planes (Fig. 1). The number of feeding holes in each plane is sufficiently large to permit the feeding planes being treated as the line sources. The results are given for the load-carrying capacity and the attitude angle. A comparative study is made of the three types of gas feeding arrangements.
Stability Threshold of Flexibly Supported Hybrid Gas Journal Bearings
Authors: Kazimierski Zbyszko , Jarzecki Krzysztof
Published: November 2010

Results of experimental investigations of the dynamic properties of elastic supports for gas bearings having the form of rubber O-rings are presented. Theoretical calculations of the stability threshold of an externally pressurized gas bearing system elastically supported by means of O-rings were performed. An experimental investigation of the stability threshold of this gas bearing system was made. Comparisons between theoretical and experimental results verify the theoretical model and illustrate the possibility of its application to design purposes.
Response of Collecting Plates in Electrostatic Precipitators Due to Shear Rapping
Authors: Juricic D. , Herrmann G.
Published: November 2010

One of the factors influencing the efficiency of modern electrostatic precipitators is the proper cleaning of dust-collecting plates, which is usually done by a periodic rapping. The paper analyzes the response of a precipitator plate to an in-plane hammer blow. A simplified one-dimensional model is considered here and the response spectra to a square pulse load of different intensity and duration are found. The results indicate that different design parameters, depending on the rap impulse level, will control the frequency spectrum of the response. The frequency spectrum is considered to play an important role in dust dislodgment mechanism.
The Steady State Response of Systems With Hardening Hysteresis
Authors: Miller R. K.
Published: November 2010

A physical model for hardening hysteresis is presented. An approximate analytical technique is used to determine the steady-state response of a single-degree-of-freedom system and a multi-degree-of-freedom system incorporating this model. Certain critical model parameters which determine the general nature of the responses are identified.
Study of Lubricant Jet Flow Phenomena in Spur Gears—Out of Mesh Condition
Authors: Townsend D. P. , Akin L. S.
Published: November 2010

An analysis was conducted for oil jet lubrication on the disengaging side of a gear mesh. Results of the analysis were computerized and used to determine the oil jet impingement depth for several gear ratios and oil jet to pitch line velocity ratios. An experimental program was conducted on the NASA gear test rig using high-speed photography to experimentally determine the oil jet impingement depth on the disengaging side of mesh. Impingement depth reaches a maximum at gear ratio near 1.5 where chopping by the leading gear tooth limits the impingement depth. The pinion impingement depth is zero above a gear ratio of 1.172 for a jet velocity to pitch time velocity ratio of 1.0 and is similar for other velocity ratios. The impingement depth for gear and pinion are equal and approximately one-half the maximum at a gear ratio of 1.0. Impingement depth on either the gear or pinion may be improved by relocation of the jet from the pitch line or by changing the jet angle. Results of the analysis were verified by experimental results using a high-speed camera and a well lighted oil jet.
Experimental and Analytical Investigation of Self-Excited Chatter Vibrations in Metal Cutting
Authors: Saravanja-Fabris N. , D’Souza A. F.
Published: November 2010

Chatter in metal cutting is a nonlinear self-excited vibration of the limit cycle type. This investigation is concerned with the analysis of chatter from the viewpoint of the describing function. Vibrations with different frequencies and amplitudes were superimposed on the steady feed motion of the tool in orthogonal cutting in order to simulate chatter. The relationships between the oscillating cutting and thrust forces and tool vibrations are discussed from the point of view of energy transfer and describing functions. Experimentally obtained describing functions of the dynamically varying cutting process are given. The stability of a typical machine tool structure under primary chatter conditions with dynamical cutting process represented by its describing function is discussed.
Application of Goal Programming to Machinability Data Optimization
Authors: Philipson R. H. , Ravindran A.
Published: November 2010

Goal programming is emerging as a practical tool to solve optimization problems where a number of conflicting goals or objectives are involved. In this paper, goal programming is explained and is applied to the multiple criteria optimization of the single-pass, single-point turning operation. It is pointed out that goal programming may be the most appropriate technique for those manufacturing situations where a single objective is either not practical or not desirable. With this technique the optimal machining conditions can be selected under such conflicting objectives as minimization of cost, achievement of a given metal removal rate and maximization of tool life.
Fluidelastic Vibration of Heat Exchanger Tube Arrays
Authors: Connors H. J.
Published: November 2010

A basic fluidelastic excitation mechanism, of a type reported in an earlier paper, causes large whirling vibrations of tubes in model arrays when the flow velocity exceeds a critical value. The critical velocity is U = βfnDmoδn/ρoD2 where β, the threshold instability constant is a function of the tube pattern and spacing. Threshold instability constants are given that were obtained from wind tunnel and water tunnel tests on multirow tube arrays in uniform cross flow. Test results are discussed that demonstrate the effects of spanwise variations in flow velocity on fluidelastic whirling for both straight tubes and U-tubes. Design methods are provided for predicting the onset of fluidelastic whirling of heat exchanger tubes on multiple supports when spanwise variations in the cross flow exist.
A Strategy for the Optimum Design of Acoustic Space
Authors: Baxa D. E. , Seireg A.
Published: November 2010

This study deals with the development of an automated computer optimization procedure for the design of acoustical space. An analysis scheme utilizing a ray tracing approach is used to calculate the acoustical response at different locations in the space. The response characteristics are utilized to quantify the acoustical merit at any location based on a developed set of criteria. An efficient search technique is employed to seek, for any given floor and stage areas, the geometric and acoustical design parameters which maximize the considered merit function, subject to any constraints imposed on the design. A simplified example of a concert hall design is considered for illustration. Considerable improvement in the acoustical merit (as defined in the paper) of such halls can be achieved by the use of the optimization scheme. The developed procedure shows excellent potential for the application of optimization techniques to the design of enclosed spaces.
Stress Distribution and Displacements on the Electromechanical Shield of a Superconducting Generator After a Three-Phase Fault
Authors: Dagalakis N. G. , Kirtley J. L.
Published: November 2010

We assume that there is a cylindrical electromechanical shield between the armature and the field windings of a superconducting generator. The maximum shield load after an open circuit three-phase fault is derived. The resultant stress distribution and displacements are calculated for two cases: for the case of a thick wall long shield, where two dimensional plane strain conditions are assumed away from the two end supports, and for the case of the moderately thick to thin shield wall, where an approximate solution is derived which approximately satisfies the three dimensional elasticity equations and the end boundary conditions. The solution was applied to 2-pole and 4-pole machine designs.
A Closed-Form Numerical Algorithm for the Periodic Response of High-Speed Elastic Linkages
Authors: Midha A. , Erdman A. G. , Frohrib D. A.
Published: November 2010

A numerical closed-form algorithm, easily adaptable for computer simulation, is developed to solve for the periodic solutions of vibrating systems, and in particular, the high-speed elastic linkage. The algorithm is first introduced to solve the single degree-of-freedom mass-dashpot-spring system, the governing differential equation of which is a linear, second-order equation with constant coefficients. This algorithm is utilized as a basic tool and extended to solve a single degree-of-freedom mass-dashpot-spring system whose governing differential equation of motion is a linear, second-order equation with time-dependent and periodic coefficients. The system is excited by a periodic forcing function and solution is made possible by discretizing the forcing time period into a number of time intervals, the system parameters remaining constant over the duration of each interval. During each interval, the solution form is assumed to be that of the differential equation with “constant” coefficients. Constraint equations result from imposing the conditions of “compatibility” of response at the discrete time nodes and the conditions of “periodicity” of response at the end nodes of the time period. Also, the sum of the integration required is over one forcing time period only. This closed-form nature of the computational procedure results in large savings in computer time to acquire the periodic solution. The suggested numerical algorithm is then employed to solve an elastic linkage problem.
Chebychev Approximations of Finite Point Sets with Application to Planar Kinematic Synthesis
Authors: Sarkisyan Y. L. , Gupta K. C. , Roth B.
Published: November 2010

In the first part of this paper we consider the problem of determining circles which best approximate a given set of points. The approximation is one which minimizes the maximum radial deviation of the points from the approximating circle. Then a similar procedure is developed for determining straight lines which best approximate a given point set. The final parts of the paper illustrate the application of these results to synthesizing planar linkages.
Optimum Synthesis of Mechanisms Using Heuristics for Decomposition and Search
Authors: Datseris P. , Freudenstein F.
Published: November 2010

The heuristic techniques developed by Lin and Kernighan [1, 2, 3] and subsequently adapted by Lee [4, 5] for the optimum synthesis of mechanisms have been extended to medium- and large-scale mechanical systems. Heuristic decomposition methods were developed by combining principles from the Design of Experiments with Heuristics. For certain classes of mechanisms other decomposition techniques were devised based on the kinematic structure of the mechanism. These techniques were then integrated with a heuristic search to yield a combinatorial optimization technique for large-scale mechanical systems. The results have been applied to the optimization of a twelve-degree-of-freedom mechanical manipulator. Based on the experience gained with the method we believe that the techniques, which have been developed, can be effective in yielding an optimum design.
An Alternative to Euclid’s Algorithm
Authors: Matthew G. K.
Published: November 2010

A general method for finding factors common to two polynomials is developed. The process is shown to have immediate application to the removal of multiplicities when attempting to root polynomials. Computational procedures and likely difficulties are discussed.
Analysis of Multiholed Orthotropic Laminated Plates by the Boundary-Point-Least-Squares Method
Authors: Sampath S. G. , Hulbert L. E.
Published: November 2010

The paper describes the application of boundary-point-least-squares method (BPLS) for the determination of stresses in multiply connected finite orthotropic plates under plane stress. Series solutions composed of mapping functions are employed. Numerical solutions presented include the case of an orthotropic plate with an elliptical hole with orientation noncoincident with the material axes.
Plastic Strength of Perforated Plates With Square Penetration Patterns
Authors: Porowski J. , O’Donnell W. J.
Published: November 2010

The sheet perforated with circular holes arranged in a square penetration pattern anp subjected to in-plane biaxial stress is investigated. Discontinuous fields of stress are used to obtain the lower-bound limit loads for the perforated material. The yield surfaces for the equivalent solid material are then derived and the effective plastic constants are given for the entire range of ligament efficiencies used in design.
Analysis of Strength and Residual Stresses in Filament Reinforced Aluminum Cylinders
Authors: Simonen F. A. , Henderson N. C. , Winegardner R. D. , Specht K.
Published: November 2010

This paper describes a study of aluminum gas cylinders used in underwater manned vehicles. A determination was made of the relative increase in one cycle burst pressure and fatigue life of an existing aluminum gas cylinder when the sidewall was reinforced with fiberglass overwrap and prestressed by over pressurization. Detailed finite-element stress analyses were conducted to determine the operating stresses and also the residual stresses at the end cap-to-cylinder transition section which were a result of plastic deformation during proof testing. Calculated residual stresses were found to be consistent with experimental measurements. It was determined that the filament reinforcement both increased the vessel burst pressure and increased the vessel fatigue life through favorable prestress effects. Results of vessel fatigue and burst tests are presented and are compared with the predicted performance characteristics.
Thermomechanical Analysis of the Welding Process Using the Finite Element Method
Authors: Friedman E.
Published: November 2010

Analytical models are developed for calculating temperatures, stresses and distortions resulting from the welding process. The models are implemented in finite element formulations and applied to a longitudinal butt weld. Nonuniform temperature transients are shown to result in the characteristic transverse bending distortions. Residual stresses are greatest in the weld metal and heat-affected zones, while the accumulated plastic strain is maximum at the interface of these two zones on the underside of the weldment.
Elevated Temperature Fatigue Tests and Inelastic Stress Analysis of Bellows
Authors: Kobatake K. , Tsukada T. , Takahashi S. , Akatsu M. , Ikemoto Y. , Baba O.
Published: November 2010

For a multiwalled piping of the elevated temperature helium gas loop or HTR, some kinds of joints are required to absorb the thermal expansion difference between the inner and outer pipes. Bellows joints are planned to use for them and developed bellows. From the 900 deg C fatigue tests of the bellows, a design curve was obtained for the estimation of the allowable cycle versus the bellows deflection. Further, an inelastic analysis was carried out on the same figures by using a FEM code and tried to study the integrity of the bellows in accordance with the creep and fatigue interaction equations.
Influence of Sulfur Content on the Fracture Toughness Properties of 2 1/4 Percent Cr-1 Percent Mo Steel
Authors: Copeland J. F.
Published: November 2010

The effects of sulfur content on the fracture toughness properties of 2 1/4Cr-1 Mo steel were evaluated at test temperatures above, at, and below the nil ductility transition temperature (NDTT) of −23°C (−10°F). Small, 12.7-mm (0.5-in.) thick compact tension specimen results were combined with J-integral, Equivalent Energy, and Crack Opening Displacement analytical techniques to provide KIc results up to 22°C (72°F). It was found that the sulfur content of this steel has a large detrimental effect on KIc at the NDTT and above, where microvoid coalescence is the fracture mode. Sulfur has no significant effect at −73°C (−100°F) where cleavage occurs. These results also indicate that the higher Charpy V-notch energy at NDTT, shown by lower sulfur steels, is translatable into increased fracture resistance.
Application of Normal Mode Theory and Pseudoforce Methods to Solve Problems With Nonlinearities
Authors: Molnar A. J. , Vashi K. M. , Gay C. W.
Published: November 2010

In the design of structural systems such as nuclear reactor coolant loops consisting of piping, supports, bumpers, and tie rods, the basic structure is linear. For transient analysis of piping loops under conditions of earthquake and hypothetical accident of pipe rupture, the linear system becomes nonlinear because of forces due to bottoming in gaps, plastic action in the bumper stops or tie rods, etc. The dynamic analysis of such a structure normally employs the direct integration of the governing nonlinear equations of motion. A technique is presented in this paper where conventional normal mode theory is used even though there are nonlinearities. Nonlinearities such as bumper-gap elements, plasticity, etc., are defined as functions of motion and incorporated as generalized pseudoforces. This approach can, to a considerable degree, preserve the benefits of modal type analysis such as physical understanding in terms of frequencies and modes, and adequate and economical solutions using a reduced number of modes.
Buckling Rules for Nuclear Components—Code Case 1592
Authors: Berman I. , Gupta G. D.
Published: November 2010

The buckling rules for nuclear components in elevated temperature service have been recently modified by the ASME Boiler and Pressure Vessel Code Committee. The specific modifications and some reasons and justifications for these modifications are described in this write-up. This write-up should be read as a supplement to Section 8.0 of the criteria document [1] for Code Case 1592 [2] of the ASME Boiler and Pressure Vessel Code.
Experimental Stress Analysis of Cylinder-to-Cylinder Shell Models and Comparisons With Theoretical Predictions
Authors: Gwaltney R. C. , Corum J. M. , Bolt S. E. , Bryson J. W.
Published: November 2010

Four carefully machined cylinder-to-cylinder shell models were tested, and the experimentally determined stresses were compared with theoretical predictions obtained from a thin-shell finite-element analysis. The models were idealized structures consisting of two circular cylindrical shells intersecting at right angles. The first model tested had a nozzle-to-cylinder diameter ratio of 0.5 and a diameter-to-thickness of 100 for both nozzle and cylinder. The second model had a nozzle-to-cylinder diameter ratio of 1.0 with a diameter-to-thickness ratio of 100. The third and fourth models had a nozzle-to-cylinder ratio of 0.129. For these models the diameter-to-thickness ratio was 50 for the cylinders and 7.68 for the nozzle of model 3, while it was 20.2 for the nozzle of model 4. All models were strain gaged and subjected to 13 separate loading cases. Comparisons of measured and predicted stress distributions are presented for three of these loadings—internal pressure and in-plane and out-of-plane moments applied to the nozzle. The analytical predictions were obtained using a finite-element program that used flat-plate elements and which considered five degrees of freedom per node in the final assembled equations. The agreement between these particular finite-element predictions and the experimental results is shown to be reasonably good for the four models.
Stress Analysis of Pipe Bends by Ring Elements
Authors: Ohtsubo H. , Watanabe O.
Published: November 2010

This paper proposes a new finite element method for treating the stress analysis of a piping system under general loading conditions. This finite element method will be referred as the finite ring method, since its elements are ring-shaped. This finite ring treatment is based on the general thin shell theory incorporating shear and distributed deformations along the pipe length. In this paper, emphasis is given to the theoretical aspects of the method. A comparison with other experimental and theoretical results is presented to substantiate the validity of the present method.
Shallow Formation Hydrofracture Mapping Experiment
Authors: Keck L. J. , Schuster C. L.
Published: November 2010

Geophysical diagnostic techniques are being developed to characterize the massive hydraulic fractures that are being utilized for the enhanced gas recovery from the Western tight gas reservoirs. Sandia Laboratories is developing a system based on the measurement of surface electrical potentials. Model calculations indicate that the electrical potentials produced by direct electrical excitation of the fracture well and the fracture fluid can be used to determine the direction and asymmetry of a massive fracture. A small scale, shallow formation hydrofracture experiment was conducted by the AMOCO Production Company in an attempt to better correlate theoretical and experimental data.
CAVIJET™ Augmented Deep-Hole Drilling Bits
Authors: Conn A. F. , Radtke R. P.
Published: November 2010

Drilling bits which exploit the destructive energy of cavitation are being developed. A systematic series of tests is now under way, first to establish feasibility, and then to define the effective adaptation of the CAVIJET™ cavitating water jet method for augmenting the cutting action of mechanical deep-hole drilling bits. Successful drilling tests, using a 1/4-in. (6.4-mm) CAVIJET nozzle, were performed at atmospheric pressure and in a test chamber which provided simulated wellbore pressures up to 3000 psi(21 MPa). The effect of back pressure on standoff distance, and a comparison of steady jet versus CAVIJET cutting efficiencies are discussed.
A Means of Assessing the Effects of Periodic Proof Testing and NDE on the Reliability of Cyclically Loaded Structures
Authors: Harris D. O.
Published: November 2010

A technique is presented that allows the effect of periodic proof testing and nondestructive evaluation (NDE) on the reliability of cyclically loaded structures to be calculated. This technique combines the initial defect size and nondestructuve inspection detection probability with fracture mechanics calculations of fatigue crack growth and final fracture to predict the failure probability of a cyclically loaded structure as a function of the number of cycles of load application. The influence of part geometry, stress levels, material properties, inspection procedures and inspection interval enter into the analysis. The results of an example problem are presented which indicates that the benefits of proof testing are restricted to a fairly short period immediately following the proof test. The length of this period can be extended significantly by acoustic emission monitoring of the proof test. The benefits of an in-service inspection can be large or small, depending on the inspection interval, detection probabilities, and stress level. The capability of the techniques presented to quantitatively assess the influence of the many parameters involved should make these procedures useful in a wide variety of applications.