bluuebunny/crossref_metadata_2025 huggingface dataset:
Rolling Element Fatigue and Macroresidual Stress
Authors: Kepple R. K. , Mattson R. L.
Published: November 2010

An experimental investigation was made to determine the effect of the initial or residual stress state on rolling element fatigue life. This was done by simulating a residual stress by a mechanically applied static stress. Hoop-shaped specimens were statically stressed in both a tangential direction and a transverse direction to simulate either a biaxial tension or biaxial compression stress state and then subjected to repeated rolling contact until failure occurred. The results showed the rolling element fatigue properties for the compression state is not significantly better than the “zero” stress state, contrary to widely held opinion, and that the tensile state is detrimental to fatigue properties as expected.
Response of a Viscoelastic Annulus to a Step Transverse Load
Authors: Robertson S. R.
Published: November 2010

The problem of finding the response of a viscoelastic annulus in plane strain to step, transverse loads is solved. It is solved by employing Valanis’ method which assumes constant Poisson’s ratio. The resulting displacements are used to calculate the work done by the applied transverse load for various thicknesses of the annuli. A simple spring-dashpot model is then fitted to the work versus time curves so as to provide the logarithmic decrement for design.
Pivoted Plane Pad Bearings: A Variational Solution
Authors: Szeri A. , Powers D.
Published: November 2010

It is known that the solution of Reynolds’ equation for the plane pad bearing presents no theoretical, but much computational, difficulty. In this paper, after a classical separation of variables is effected, the eigenvalue problem that arises is replaced by a Rayleigh-Ritz matrix. Then it is shown that the design variables of the bearing—all of which depend on integrals of the pressure—can be calculated quite accurately from inner products involving two vectors and a function of the Rayleigh-Ritz matrix, without solving any eigenvalue problem.
The Optimum One-Dimensional Magnetohydrodynamic Slider Bearing
Authors: Shukla J. B.
Published: November 2010

In this paper, the techniques of the calculus of variations are used to study the general problems in magnetohydrodynamic lubrication when two or more control variables are bounded. The load integral, in the case of a magnetohydrodynamic slider bearing, is maximized with film thickness and conductivity functions as bounded control variables. It is shown that if the conductivity of a bearing surface is of step-type function then uniformly applied magnetic fields are more advantageous.
Frictional Behavior in Metalworking Processes
Authors: Peterson M. B. , Ling F. F.
Published: November 2010

Frictional behavior in metalworking processes between the tool and the workpiece for unlubricated condition is discussed. The primary aim of the work was to develop means to predict frictional behavior in terms of which metal flow can be better understood. Experimental and theoretical work has been carried out to determine the important variables of metal working friction. It was found that friction is dependent upon the strength of the workpiece, the pressure, the surface adhesion, and the surface roughness. The pressure-dependence of shear strength based on experimental data is also discussed. Finally, although techniques are available to predict friction, they are dependent upon the ability to predict interface surface temperature.
A Comparison of the Frictional Losses in Hydrostatic and Conventional Extrusion Processes With Hydrodynamic Lubrication
Authors: Wilson W. R. D.
Published: November 2010

Experimental evidence indicates that billet die friction is higher in conventional extrusion than in hydrostatic extrusion. Simple hydrodynamic lubrication theory is used to show that this may be accounted for by the less favorable conditions for hydrodynamic lubrication in the conventional process.
An Analysis of the Flow of Oil Through a Tapered Roller Bearing
Authors: Leibensperger R. L.
Published: November 2010

A theoretical analysis, based on boundary layer theory, is presented to predict the oil pumping ability of a tapered roller bearing. The momentum integrals for an assumed laminar boundary layer about the I.D. circumference of the outer race (cup) are derived and solved numerically. The resulting equations predict that the head, flow and viscous torque generated are dependent upon the bearing’s speed and geometry, as well as the viscosity and density of the oil in the bearing.
Asymptotic Methods for an Infinitely Long Step Slider Squeeze Bearing
Authors: DiPrima R. C.
Published: November 2010

The step slider squeeze bearing is analyzed by a combination of singular perturbation techniques and numerical procedures. It is assumed that the bearing number associated with the trailing section is large and that the amplitude of the squeezing motion is small. There is no restriction on the film clearance or the jump in the film thickness at the step, so the bearing number associated with the leading section of the bearing need not be large. Results for the steady-state load are given for several geometries. Stability characteristics of different geometries are discussed.
Lubrication of Narrow Porous Bearings With Arbitrary Wall Thickness
Authors: Murti P. R. K.
Published: November 2010

An analysis is given for the hydrodynamic lubrication of short porous metal bearings that are press-fitted into a solid housing. An exact solution is given for the pressure of the lubricant in the bearing material using modified Bessel functions and the modified Reynolds equation for the problem is solved by the Galerkin method. Numerical results obtained on a digital computer indicate a progressive reduction in the load capacity and increment in the friction parameter and attitude angle as the permeability parameter is increased. These results are presented in graphical and tabular forms. A side result of this analysis is the emergence of a new permeability parameter and its convenience in bearing selection is discussed.
Gas Bearing Failure as a Result of Surface Erosion
Authors: Heyerman J. L.
Published: November 2010

Material erosion from the working surfaces of gas bearings can cause failure. A gas bearing gyroscope wheel, used in guidance instruments for space vehicles, experienced this type of failure. The problem was revealed by the use of optical and scanning electron microscopes. Elimination of the problem was completed via better preparation of the surfaces in contact with the gas film.
Pressure Viscosity Characteristics of a Series of Siloxane Fluids
Authors: Jakobsen J. , Sanborn D. M. , Winer W. O.
Published: November 2010

The viscosity-pressure-temperature behavior of a series of 14 siloxane polymers is reported. The series of fluids includes a range of degree of polymerization and of size and nature of side radicals. The variations span the range of siloxane fluids currently available and considered as possible lubricants. The major conclusion is that the pressure viscosity coefficient considered important to elastohydrodynamic lubrication is only influenced by changing the nature of the side radical and not by the degree of polymerization or the size of alkyl side groups on the siloxane chain.
The Evolution of Surface Pressure and Temperature Measurement Techniques for Use in the Study of Lubrication in Metal Rolling
Authors: Kannel J. W. , Dow T. A.
Published: November 2010

The paper describes the evolution of surface pressure and temperature transducers to a level of sophistication and reliability such that they can be used in the investigation of lubrication in sheet-rolling processes. The paper cites the development of these techniques from their inception (where they were used solely in the elastohydrodynamic regime) to their current application in the plastohydrodynamic and boundary lubrication regimes characteristic of sheet-rolling operations. The pressure and temperature data determined, using the transducers in experiments involving the rolling of steel sheet, show significant variation throughout the contact zone and these data are particularly influenced by changes in the lubricant and the deformation-process conditions.
Axial Current Induced Pinch Effect on the Squeeze-Film Behavior for Porous Annular Disks
Authors: Gupta J. L. , Sinha P. C.
Published: November 2010

An analysis of the effect of axial current induced pinch on the squeeze-film behavior between two annular disks, when the upper disk which has a porous facing and is parallel to the stationary nonporous disk moves normal to itself approaching the lower disk, is presented. The analytical results for the pressure distribution, load-carrying capacity, and the film thickness as a function of time are obtained and the effect of pinch on these quantities is studied. It is found that a load proportional to the square of the axial current can be sustained even when there is no flow.
Hydrostatic Extrusion With Controlled Follower Block Clearance
Authors: Kulkarni K. M. , Schey J. A.
Published: November 2010

Hydrostatic extrusion of annealed 1100 aluminum was investigated experimentally at ambient temperature. The principal variables studied were lubricant viscosity which was varied from less than 100 to over 76,000 SUS at 100 deg F and the diametral clearance between the follower block and the extrusion cylinder which ranged from 0.0005 to 0.0030 in. for the 1.026 in. dia. cylinder. The specimen diameter was 0.97 or 1.00 in. corresponding to an extrusion ratio of 4.75 or 5.00, respectively. The included die angle was either 60 deg or 90 deg. The results show that with a proper combination of the lubricant viscosity and the follower block clearance, hydrostatic extrusion can be accomplished without the necessity of any sealing of the container on the follower block side. The optimum clearance for minimum breakthrough pressure increases as the lubricant viscosity increases. The extrusion force increases with die angle. The paper discusses the various factors that affect the magnitude of the breakthrough pressure and the occasional uneven bamboo-type appearance of the surface. Processing conditions must be selected carefully since the lowest extrusion force does not necessarily lead to a product with the best surface finish.
On the Performance of Journal Bearings Under Conditions of Film Rupture, Part I
Authors: Crosby W. A. , Badawy E. M.
Published: November 2010

A model of film rupture taking into account both the finger-pattern and the flow carried away over and/or under the cavity is considered. A tractable boundary condition is derived by assuming that the Reynolds flow is retained in the vicinity of the cavity. The pressure isobars and cavity profile are shown at different depths of the clearance space. Thus, the shape of the separation line is obtained. A modification is suggested so that the boundary condition may accommodate the occurrence of cavitation at higher loads.
On the Calculation of Seizure Considering the Plastic Flow of the Surficial Layers
Authors: Kragelsky I. V. , Alekseev N. M.
Published: November 2010

A scheme for estimating, in two stages, the seizure of friction pairs has been proposed. The first stage is the assessment of the extent of destruction of lubricant or other protective films. The second stage deals with plastic flow which occurs in surficial layers of the solid. For the second stage, the solid is assumed to be perfectly plastic with deformation hardening. This material model allows the definition of conditions at which plastic flow develops and damage of the surfaces occurs in the form of torn out wedges. Examples of such an estimate for seizure which considers both the properties of lubricant and protective surface films and mechanical properties of the surficial layer of material have been given. Comparison is made of the estimate and experimental data.
Infrared Emission Spectra of Elastohydrodynamic Contacts
Authors: Lauer J. L. , Peterkin M. E.
Published: November 2010

A small diamond disk mounted as a window in a steel plate was covered with test fluid, and a weighted steel ball was rotated over the window so as to form a sliding elastohydrodynamic (EHD) contact region. Some of the radiant energy generated in this region, both in the fluid and at the boundaries, passed through the window into an infrared interferometer, giving rise to an emission spectrum. This spectrum could be separated into contributions from the fluid and from the ball surface, making it possible, by appropriate calibrations, to estimate their temperatures separately under operating conditions. Moreover, the shape of the discrete spectral bands of the fluid permitted some inferences on its state. Two fluids were studied under identical mechanical conditions, a polyester and a naphthenic oil, each containing an equal amount of polymethylstyrene as a spectral indicator. Differences of band intensity, band width, and frequency could, therefore, be attributed to differences in the behavior of the base fluid. The principal results were much lower fluid temperatures and lower metal surface temperatures when the polyester was used than when the naphthenic oil was similarly used. Polyester films were also thicker and of higher density than naphthenic oil films under the same conditions. This work is only the beginning of a comprehensive study of EHD contacts by infrared spectroscopy, but the results already achieved lead to interesting speculations on the mechanisms of EHD processes, which further study is expected to elucidate.
A Thermal Hydrodynamic Lubrication Theory for Hydrostatic Extrusion of Low Strength Materials
Authors: Snidle R. W. , Parsons B. , Dowson D.
Published: November 2010

The paper presents a theoretical analysis of hydrodynamic lubrication in the hydrostatic extrusion process which includes a consideration of thermal effects in the lubricant film arising from the work of plastic deformation. A Newtonian lubricant with an exponential pressure-temperature-viscosity relationship has been assumed and allowance has been made for the effects of redundant deformation of the worked material. The results of the theory are compared with those from previous isothermal and solid friction theories.
Leakage-Free Journal Bearings
Authors: Pinkus O. , Etsion I.
Published: November 2010

A new concept of a journal bearing is developed which prevents side leakage of the lubricant, thus eliminating the need for sealing and collecting this leakage. The cooling of the bearing is accomplished by the prevailing circumferential flow. An analysis is performed and solutions are given for the bearing geometries and inlet pressures required to achieve the above purpose.
The Optimal Wearpath Principle
Authors: Engel P. A.
Published: November 2010

The concept of the optimal wearpath is helpful in determining the geometrical formation of the wear scar due to repeated contact loading. By definition it is that shape which alleviates the critical contact failure parameter(s) the fastest way. In the present paper the mathematical formalism is set forth for the ensuing optimization problem. The general prescription for formulating a wear law for a specific application (sliding, rolling, impact, and hybrids) is to combine the wear mechanism with the optimal wearpath. Examples for impact wear are presented, using both macroscopic and microscopic wear models.
A Theoretical Study of the Effects of Cooling on Thermoelastic Contact Instabilities
Authors: Heckmann S. R. , Burton R. A.
Published: November 2010

The effects of cooling on thermoelastic instability are delineated for a two dimensional flat plate geometry. The analysis includes conductive heat transfer from the edge of the flat plate as well as convective heat transfer from its sides. Cooling is found to be characterized by two dimensionless parameters allowing a direct comparison between these results and previous results where cooling was ignored. An immediate assessment can be made concerning the significance of cooling, and if cooling effects need be included in the design analysis.
Effects of Load, Speed, and Surface Roughness on Sliding EHD Contact Temperatures
Authors: Nagaraj H. S. , Sanborn D. M. , Winer W. O.
Published: November 2010

An infrared technique has been used to determine the effects of load, speed and surface roughness on temperature in a sliding EHD point contact. Ball surface temperatures are reported for sliding speeds of 0.35 to 5.08 m/s at 0.52 to 2.03 GN/m2 maximum pressure with surface roughness in the range 0.01 to 0.38 μm c.1.a. The relationship between asperity interaction, as measured by relocation surface profilimetry and high frequency temperature measurements, and the ratio of film thickness to surface roughness has also been studied.
Vibrational Characteristics of Ball Bearings
Authors: Gupta P. K. , Winn L. W. , Wilcock D. F.
Published: November 2010

The classical differential equations of motion of the ball mass center in an angular contact thrust loaded ball bearing are integrated with prescribed initial conditions in order to simulate the natural high frequency vibrational characteristics of the general motion. Two distinct frequencies are identified in the analytical simulation and their existence is also confirmed experimentally. One of the frequencies is found to be associated with the Hertzian contact spring at the ball race contact and it is therefore defined as the “elastic contact frequency”, Ωe. The other dominant frequency corresponding to oscillatory motion of the ball in the raceway groove appears to be kinematic in nature and it is, therefore, termed as the “bearing kinematic frequency”, Ωk. It is shown that for a given bearing Ωe and Ωk, vary as, respectively, 1/6 and 1/2 powers of the ball contact load and, therefore, for a given load these frequencies correspond to the natural frequencies of the bearing as applied in any vibrational analysis or simulation.
The Thermoelastic Patch Contact Problem for Large Peclet Number
Authors: Kilaparti S. R. , Burton R. A.
Published: November 2010

An equation in the form of a Fourier series was derived in an earlier study to give displacements of the originally straight edge of a plate as the result of a small heat input patch moving at speed c along that edge. That unwieldly formulation is reduced to a simple integral equation, which is shown to be manageable in an example calculation. The integral equation is shown to be closely related to that of Ling and Mow, although it is much simpler to use. Comparison of the results of the simplification to results of the original series formulation suggest that the equation proposed for “high Peclet number” may be a valid approximation for Peclet number as low as 2.5 = Pel = cl/πk, and l is the width of the patch of heat input, k is the thermal diffusivity of the material.
Strain Rate Effects in Low Speed Two-Body Abrasion
Authors: Larsen-Basse J. , Tanouye P. A.
Published: November 2010

Specimens of pure aluminum, copper, and iron were abraded on silicon carbide abrasive papers. The sliding velocity was varied between 0.5 and 82 mm/s and a range of abrasive grit sizes was used. The cutting force is composed of a friction contribution, which accounts for 70–90 percent of the total, and a plastic work contribution. The plastic work contains a velocity-independent and a velocity-dependent contribution. The velocity-independent part is the work to deform the metal plastically to a true strain of approximately 5. The velocity-dependent part is relatively small and is proportional to the logarithm of the velocity. It is caused by the effect of strain rate on the flow stress. No effects of grit size alone on strain rate were found.
On the Influence of Finite Wall Conductance and Inertia Effects of Hydrostatic Thrust Bearing
Authors: Kapur V. K. , Verma Kamlesh
Published: November 2010

An analytical study is presented on the influence of finite wall conductance and inertia effects in magnetohydrodynamic lubrication flow between two parallel disks, one of which is rotating with constant angular velocity, in the presence of the axial magnetic field. Numerical results showing the behavior of wall conductance and inertia effects on pressure distribution, load carrying capacity, critical speed, and frictional torque of the bearing are obtained. Results obtained will provide necessary conditions for wall materials to improve the bearing performance.
A Variable Wave Speed Technique for the Steady-State Analysis of Low-Clearance Gas Bearings
Authors: White J. W.
Published: November 2010

A method is described which utilizes an artificial fluid viscosity as a means of adjusting the pressure wave speed in asymptotic steady-state analysis of gas bearings. The approach is shown to be useful for producing steady numerical solutions of low-clearance bearings with minimum computation. The technique is first developed for a rigid boundary step bearing of infinite width and then extended to the finite width case by a semi-implicit solution procedure. Last, the method is shown to be useful for the analysis of foil bearings in which case the pressure wave speed is “tuned” to that of the foil wave so as to produce an optimum computational approach to steady state.
The Lubrication of a Long, Porous, Flexible Journal Bearing
Authors: Mak W. C. , Conway H. D.
Published: November 2010

Solutions are obtained for the pressure distributions in porous, flexible long bearings. The oil is assumed to have a viscosity which is either (a) constant or (b) varying with pressure according to the law η = η0eαp. Finally, a method is given whereby the pressure distributions in porous, flexible bearings can be found approximately from the corresponding values for non-porous bearings. The limits of validity of the approximation are investigated.
The Stability of a Flexible Rotor Supported by Circumferentially Fed Journal Bearings
Authors: Bar-Yoseph P. , Blech J. J.
Published: November 2010

The stability of a flexible rotor, perfectly balanced, was investigated theoretically. The rotor is symmetrically supported by circumferentially fed journal bearings. Short and finite bearings were treated. Stability was checked for small and large disturbances. Two methods were employed to treat large disturbances: Direct integration and the slowly varying technique. The nonlinear prediction was tested concurrently with the prediction of the stability charts. It was observed that in certain cases stability can be obtained in the asymptotic and in the unstable regions. Instability was obtained for regions which presumably are asymptotically stable in the entire speed range.
Transient Response of a Rotor in Damped Bearings
Authors: Pilkey W. D. , Strenkowski J. S. , Chang P. Y.
Published: November 2010

In this paper, the transient response of a rotor subjected to a general forcing function is presented. The rotor model permits any number of in-span bearings, which include stiffness, damping, and mass properties. The excitation forces may include distributed loadings along the rotor as well as transient bearing base motion. The response is found by use of a modal analysis that incorporates the damped mode shapes. An illustrative example is presented of a rotor subjected to an initial displacement and a saw-tooth bearing base displacement.
Optimality Criterion Techniques Applied to Mechanical Design
Authors: Khan M. R. , Thornton W. A. , Willmert K. D.
Published: November 2010

Presented are two optimality criterion techniques for the minimum weight design of mechanical and structural systems subject to limitations on stresses and natural frequencies. The results, based on their application to several examples, are compared with those obtained by other researchers and with standard nonlinear mathematical programming techniques, as well as with a special linear approach. It is shown in all cases that the optimality criterion methods are capable of locating the optimal design and are far superior to other methods in terms of computational time.
Torsional Vibrations of Pretwisted Cantilever Plates
Authors: Gupta K. , Rao J. S.
Published: November 2010

A pretwisted cantilever plate is treated as a thin shallow shell. Its potential and kinetic energies in torsional vibration are determined by assuming an appropriate displacement field. Applying Hamilton’s principle, the problem is reduced to a fourth-order ordinary differential equation with constant coefficients, which is solved to obtain the first four torsional frequencies of vibration. Plates of aspect ratios varying from 1.0 to 8.0 are analyzed with pretwist angles varying from 0 to 90 deg. Results of the present analysis are compared with existing theoretical and experimental results.
Dynamic Response of Packets of Blades by The Finite Element Method
Authors: Salama A. L. , Petyt M.
Published: November 2010

The finite element method is used to study the free vibration of packets of blades. A packet of six shrouded blades is analyzed, only the tangential vibrations being considered. Results are obtained to establish the effect of certain parameters such as stiffness ratio, mass ratio, the number of blades in the packet, the effect of rotation and the position of the lacing wires. The dynamic response of a packet to periodic loading is also studied. The cases of engine order harmonic excitation and partial admission of gas are considered with reference to a packet of six shrouded blades.
Wide-Band Random Vibration of Circular Plates
Authors: Itao K. , Crandall S. H.
Published: November 2010

When a uniform circular thin plate is excited at a point by a stationary wide-band random force process the transverse motion response at any point is also a wide-band random process. If enough modes are excited, however, there is an unexpectedly simple pattern in the spatial distribution of mean-square response. The main features of the pattern are narrow lanes of intensified response along the diameter through the driving point and along the circle, concentric with the plate boundary, which passes through the driving point. This phenomenon is investigated analytically and experimentally for a free-edged aluminum plate, 0.16 cm (1/16 in.) thick and 0.91 m (3 ft) in diameter. Qualitative agreement is obtained between measured response distributions and the predictions of an idealized analytical model for excitation bandwidths within the range from 500 to 5000 Hz.
Control of Clearance Effects in Mechanisms
Authors: Grant S. J. , Fawcett J. N.
Published: November 2010

The dynamic effects of bearing clearances in mechanisms can cause increased bearing loadings and noise. These undesirable effects occur when contact is remade in a bearing after relative motion of the two parts of the bearing within the clearance space. Thus if loss of contact could be prevented, the impulsive loadings which would normally occur would be eliminated. A method for preventing contact loss in a bearing by the use of constant magnitude spring forces, arranged so that the maximum bearing load is not increased, is described. Experimental results from a four bar linkage are presented. A method for calculating the magnitude of the required spring force using a standard no-clearance analysis is described.
Mechanical Error Analysis of Spatial Linkages
Authors: Dhande S. G. , Chakraborty J.
Published: November 2010

In this paper the effect on the output error of function-generating spatial linkages due to tolerances on the links and clearances at the hinges is analyzed. Tolerances on link lengths are assumed to be normally distributed. For the clearance error in spherical, prismatic, and revolute joints, uniform probability density function is assumed. However, the models developed and the analysis procedure proposed can be used for any other probability density function including the mean and variance values derived from experimental information. A synthesis procedure to allocate tolerances and clearances on different members of linkages to restrict the output error within specified units is developed. Results of analysis and synthesis are given for two example problems involving RRSS and RSSR mechanisms.
A Study on Hourglass Worm Gearing with Constant Slide-Roll Ratio
Authors: Sakai T. , Maki M. , Tamura H.
Published: November 2010

A new type of hourglass worm gearing is developed by the authors’ own theories [1], [2]. This hourlgass worm gearing has the good points of Hindley’s one and also covers the weak points of it. The worm is cut by a tool with straight-lined cutting edge which is fixed to the basic member [1]. The tooth of the worm has the secondary action, and the wheel tooth consists of two kinds of surfaces. The wheel tooth surface which is concerned to the secondary action of the worm has the same character with the enveloped surface of the Hindley’s wheel [2]. Thus this worm gearing has two characteristics of contact. One is recognized as the contact lines lying perpendicularly to the relative sliding velocity. The other is recognized as the contact lines of constant slide-roll ratio. That is, the worm tooth surface and a part of the wheel tooth surface contact with each other with constant slide-roll ratio. The gears manufactured by the authors showed an efficiency of over 80 percent and the wear of the wheel tooth surface was less than that of Hindley’s one.
Kinematics of an Epicyclic Gear Pump
Authors: Wojcik C. K.
Published: November 2010

A novel gear pump employing epicyclic gears is introduced. The geometric constraints of the system are stated, the kinematic requirements for its successful operation are discussed and determined by means of the method of the instantaneous centers. In terms of performance, the pump is characterized by a high displacement rate, similar to that of a piston pump. However, the geometry and the kinematics of the two systems are different. White in the case of a piston pump the pumping action is due to the reciprocal linear motion of the piston, in the case of an epicyclic gear pump it is due to the relative motion of the planet gears. Further, during the operation of the epicyclic gear pump none of its elements changes the direction of its motion.
Design Charts for Disk Cams with Reciprocating Radial Roller Followers
Authors: Ganter M. A. , Uicker J. J.
Published: November 2010

Design charts are presented for evaluating the minimum radius of curvature of a disk cam with a radial roller follower. These computer generated charts follow well known theory but show surprising discrepancies from long accepted results of other authors.
Higher Order, Planar Tangent-Line Envelope Curvature Theory
Authors: Soni A. H. , Siddhanty M. N. , Ting K. L.
Published: November 2010

Following the analogy of higher order point-path generation, new concepts for tangent-line higher order envelope curvature theory are introduced. Mathematical relationships are derived to define, using the instantaneous invariants and the stretch rotation concepts, the characteristic numbers λ1 and λ2 for third and fourth-order contacts at the tangency point of a tangent-line generating an envelope. The newly developed tangent-line higher order envelope curvature theory is applied to demonstrate its application in synthesis of mechanisms. Examples involving circular, elliptic and involute are generation using a mechanism are presented.
Frontiers of Optimal Design
Authors: Siddall J. N.
Published: November 2010

A discussion of the current state and future prospects of optimization in design. Although the emphasis is on the use of computerized algorithms, attention is also given to the evolutionary and intuitive processes in optimal design. The importance of the process of imbedding optimization algorithms in the whole design process is emphasized. It is argued that no single nonlinear programming technique can be expected to dominate the field, and that we cannot anticipate any major breakthrough in the achievement of a rapid global optimum.
Thermal Stress Analysis of Multiholed Composite Plates and Cylinders by the Boundary-Point-Least-Squares Method
Authors: Hulbert L. E. , Sampath S. G.
Published: November 2010

The paper describes the application of the boundary-point-least-squares method (BPLS) to the determination of the two-dimensional temperatures and thermal stresses in composite multiply connected domains. Series solutions are first determined for the steady-state temperatures. Using these temperature solutions, the solution to the thermally-induced stresses is automatically found in terms of Airy stress function series. Applications are described which illustrate use of the method in specific problems.
Finite Element Study of Pressure Wave Attenuation by Reactor Fuel Subassemblies
Authors: Belytschko T. , Kennedy J. M.
Published: November 2010

The attenuation of pressure waves by the subassembly walls in a reactor core was studied by a two dimensional, finite element program. For these purposes, a hydro-dynamic finite element was incorporated in an existing dynamic structural program. The resulting program has the advantage that complex boundary conditions and the interaction of structural and fluid elements are handled in a straightforward manner. The program was used to model a section of the hexcan and the surrounding fluid; the hexcan was modelled by beam elements. It is shown that the hexcan walls attenuate pressure peaks by about 33 percent in the adjacent subassembly. Thus the subassembly walls may play an important role in confining the effects of local accidents.
Elevated Temperature Fatigue Behavior of 2 1/4 Cr-1 Mo Steel
Authors: Brinkman C. R. , Booker M. K. , Strizak J. P. , Corwin W. R.
Published: November 2010

Results are reported for a number of load and strain controlled fatigue tests conducted over the temperature range of room temperature to 1000°F (538°C). Cyclic hardening and softening characteristics for a single heat of 2 1/4 Cr-1 Mo steel in the isothermally annealed condition are discussed. Comparisons of the data generated in this effort are made with data available from the literature and from these compilations possible ASME design fatigue curves were prepared covering continuous high and low cycle behavior over the temperature range of room temperature to 1100°F (593°C). Equations for these design curves are also given.
Thrust Balancing Exhaust Fitting for Safety and Relief Valves
Authors: Phillips D. W.
Published: November 2010

A description is given of the stress distribution in an elastically strained standard safety valve installation, followed by a discussion of the problem introduced by settlement and vertical expansion in finding a means of support for rapid and extensive changes of load. Given is a method for absorbing today’s greater design thrusts safely and economically, while meeting the need to accommodate varying positions in space. Basically, a greater thrust has meant reinforcement of the valve, piping and supports. However, the use of readily available standard valve, flange and other high pressure components to the fullest extent possible consistent with safety is much preferred. After considerable experience with the application of these principles, they are now presented for general consideration along with illustrations of practical designs that have evolved in their use.
Stresses in Ruptured Floating Roofs
Authors: Epstein H. I. , Buzek J. R.
Published: November 2010

Procedures are developed for determining the stresses and displacements for pontoon-type floating roof structures subjected to the loading caused by the product leaking through punctures onto the deck. The effects of various parameters such as tank diameter, product density and pontoon geometry are examined. Numerical examples are presented which compare the stresses and deflections for the ruptured case to those caused by accumulated rainwater. Large axial compressive stresses together with their associated buckling problems are found in the pontoon for the examples presented. Possible corrective measures for these problems are considered.
Field Application of Externally Stress-Relieved Drill Collars
Authors: Primm L. A.
Published: November 2010

This paper discusses the 1975 field results of the application of external stress relief grooves on drill collars. It contains a formula for the calculation of the groove diameter and makes recommendations for how and where to cut these features. Increased connector fatigue life was gained.
The Inelastic Deformation of Pressurized Stainless Steel Tubes Under Dynamic Bending and Torsional Loading
Authors: Larson L. D. , Stokey W. F.
Published: November 2010

A test program was conducted to investigate the inelastic response behavior of internally pressurized tubes subjected to dynamic bending and torsion loads. The basic experiment was a drop test in which the cantilever tube was dynamically loaded by a torque arm with a concentrated weight at the end. The experimental data consist of strain versus time records and peak and permanent deflections. Analytical predictions of the response were made using a lumped parameter beam model of the structure. This simple representation of the pressurized tube is made possible by use of an approximate analytical model for the inelastic deformation of a pipe element subjected to pressure, bending and torsion. The predicted responses are compared with measured responses to assess the accuracy of the models.
Fracture Toughness Properties of SA540 Steels for Nuclear Bolting Applications
Authors: Seeley R. R. , Van Der Sluys W. A. , Lowe A. L.
Published: November 2010

Large bolts manufactured from SA540 Grades B23 and B24 are used on nuclear reactor vessels and require certain minimum mechanical properties. A minimum fracture toughness of 125 ksi in. (137 MPa m) at maximum operating stresses is required by the Nuclear Regulatory Commission for these bolts. This minimum toughness property was determined by a stress analysis of a bolt. Minimum required Charpy impact properties were calculated by a fracture toughness-Charpy impact energy correlation and the minimum calculated fracture toughness. The fracture toughness, yield strength and Charpy V notch impact properties were determined for five commercial heats of SA540 steels. Correlations between the fracture toughness and Charpy impact properties of these materials were evaluated. The toughness-impact energy correlation used to set the minimum required Charpy impact properties was found to be unduly conservative, and a different correlation of these properties is suggested. The SA540 steels investigated exhibited fracture toughness properties in excess of the NRC minimum requirements.
Analytical and Experimental Stress Analysis of a Cylinder-to-Cylinder Structure
Authors: Brown S. J. , Haizlip L. D. , Nielsen J. M. , Reed S. E.
Published: November 2010

This paper presents a comparison of stress results obtained using the FESAP three-dimensional finite element computer program with results obtained from experimental testing. The comparison was obtained for the case of internal pressure applied to a cylinder-to-cylinder structure with a variable shell thickness at the juncture and a D/d of 1.6. The experimental testing conducted at the Babcock & Wilcox Research Center, Alliance, Ohio, consisted of strain gage testing followed by a “stress freezing” photoelastic analysis. The numerical analysis was performed at the Babcock & Wilcox Nuclear Equipment Division using the FESAP three-dimensional isoparametric element with incompatible modes. The model mesh was generated with the program FEMEG which is briefly discussed. The paper includes a detailed description of both the experimental and analytical studies. It is concluded that FESAP, with the eight-node incompatible mode element can accurately and economically predict the structural response of complex components.
Approximate Prediction of Hoop Stresses at Major Sections of Tee Intersections of Cylindrical Shells Subjected to Internal Pressure
Authors: Redekop D. , Schroeder J.
Published: November 2010

An approximate method is formulated to predict elastic hoop stresses in the longitudinal plane of unreinforced pressurized tees using axisymmetric solutions from plate-cylindrical shell intersections. These stresses are compared with experimental data and finite element results. Correspondence of values is such that the present method may be preferred to a full-scale finite element analysis for some cases. A comparison is also made between the hoop stresses in the transverse plane of tees and those in sphere-cylinder intersections. Hoop stresses from these two solutions do not compare.
ANALYTIC FIRST-ORDER EIKONAL MODEL FOR HEAVY-ION ELASTIC SCATTERINGS
Authors: KIM YONG JOO , WOO JONG-KWAN , CHA MOON HOE
Published: November 2010

We present analytic expressions for the zero-order eikonal phase shift and its first-order correction by approximating a distance between two colliding nuclei. This formalism has been applied to elastic scatterings of the 12 C + 40 Ca and the 12 C + 90 Zr systems at E lab = 420 MeV , and the 16 O + 40 Ca and the 16 O + 90 Zr ones at E lab = 1503 MeV . The calculated angular distributions, taking into account up to the analytic first-order eikonal phase shift, are found to be in fairly good agreement with the observed data. The reaction cross-sections obtained from the present model produce very excellent agreements with ones of exact first-order eikonal model calculations. We have found that analytic eikonal phase shift including the first-order correction is one theoretical method to the analysis of heavy-ion elastic scattering.
Voluntary running, skeletal muscle gene expression, and signaling inversely regulated by orchidectomy and testosterone replacement
Authors: Ibebunjo Chikwendu , Eash John K. , Li Christine , Ma QiCheng , Glass David J.
Published: November 2010

Declines in skeletal muscle size and strength, often seen with chronic wasting diseases, prolonged or high-dose glucocorticoid therapy, and the natural aging process in mammals, are usually associated with reduced physical activity and testosterone levels. However, it is not clear whether the decline in testosterone and activity are causally related. Using a mouse model, we found that removal of endogenous testosterone by orchidectomy results in an almost complete cessation in voluntary wheel running but only a small decline in muscle mass. Testosterone replacement restored running behavior and muscle mass to normal levels. Orchidectomy also suppressed the IGF-I/Akt pathway, activated the atrophy-inducing E3 ligases MuRF1 and MAFBx, and suppressed several energy metabolism pathways, and all of these effects were reversed by testosterone replacement. The study also delineated a distinct, previously unidentified set of genes that is inversely regulated by orchidectomy and testosterone treatment. These data demonstrate the necessity of testosterone for both speed and endurance of voluntary wheel running in mice and suggest a potential mechanism for declined activity in humans where androgens are deficient.
Deploying Mouse Models of Pancreatic Cancer for Chemoprevention Studies
Authors: Grippo Paul J. , Tuveson David A.
Published: November 2010

With the advent of mouse models that recapitulate the cellular and molecular pathology of pancreatic neoplasia and cancer, it is now feasible to recruit and deploy these models for the evaluation of various chemopreventive and/or anticancer regimens. The highly lethal nature of pancreatic ductal adenocarcinoma (PDAC) makes multiple areas of research a priority, including assessment of compounds that prevent or suppress the development of early lesions that can transform into PDAC. Currently, there are over a dozen models available, which range from homogeneous preneoplastic lesions with remarkable similarity to human pancreatic intraepithelial neoplasms to models with a more heterogeneous population of lesions including cystic papillary and mucinous lesions. The molecular features of these models may also vary in a manner comparable with the differences observed in lesion morphology, and so, navigating the route of model selection is not trivial. Yet, arming the community of cancer investigators with a repertoire of models and the guidance to select relevant models that fit their research themes promises to produce findings that will have clinical relevance. Cancer Prev Res; 3(11); 1382–7. ©2010 AACR.
Pseudaphelenchus vindai n. sp. (Tylenchomorpha: Aphelenchoididae) associated with termites (Termitidae) in Barro Colorado Island, Panama
Authors: Kanzaki Natsumi , Giblin-Davis Robin M. , Herre E. Allen , Scheffrahn Rudolf H. , Center Barbara J.
Published: November 2010

In 2008, a field survey of termite-associated nematodes was conducted on
Barro Colorado Island, Smithsonian Tropical Research Institute (BCI, STRI),
Panama. During that survey, an undescribed Pseudaphelenchus species was
isolated from three species of subterranean termites, Amitermes beaumonti,
Microcerotermes exiguous and Obtusitermes panamae. The nematode is described
and figured herein as P. vindai n. sp. The new species is morphologically
similar to its only congener, P. yukiae, i. e., these two species share a
thin stylet with small and clear basal knobs, a true bursa supported by
three bursal limb-like genital papillae and a nerve ring surrounding the
anterior clear region of the pharyngeal gland lobe and intestine. The
molecular phylogenetic analysis based upon near full length (ca 1.7 kb) SSU
ribosomal DNA sequence suggested that the new species forms a well supported
clade with P. yukiae, at the basal position of the family Aphelenchoididae.
The new species is distinguished from P. yukiae by possessing a clear
condylus and rostrum of the capitulum and arcuate calomus/lamina complex of
the spicules vs no condylus and rostrum and a relatively straight
calomus/lamina complex, long and tapering female tail without small mucro vs
blunt with small mucro present and possession of lateral field with three
incisures vs four incisures.
BDNF Overexpression in the Forebrain Rescues Huntington's Disease Phenotypes in YAC128 Mice
Authors: Xie Yuxiang , Hayden Michael R. , Xu Baoji
Published: November 2010

Huntington's disease (HD) is caused by an expansion of the polyglutamine tract at the N terminus of huntingtin. This mutation reduces levels of BDNF in the striatum, likely by inhibiting corticalBdnfgene expression and anterograde transport of BDNF from the cerebral cortex to the striatum. Substantial evidence suggests that this reduction of striatal BDNF plays a crucial role in HD pathogenesis. Here we report that overexpression of BDNF in the forebrain rescues many disease phenotypes in YAC128 mice that express a full-length human huntingtin mutant with a 128-glutamine tract. TheBdnftransgene, under the control of the promoter for α subunit of Ca2+/calmodulin-dependent protein kinase II, greatly increased BDNF levels in the cerebral cortex and striatum. BDNF overexpression in YAC128 mice prevented loss and atrophy of striatal neurons and motor dysfunction, normalized expression of the striatal dopamine receptor D2 and enkephalin, and improved procedural learning. Furthermore, quantitative analyses of Golgi-impregnated neurons revealed a decreased spine density and abnormal spine morphology in striatal neurons of YAC128 mice, which was also reversed by increasing BDNF levels in the striatum. These results demonstrate that reduced striatal BDNF plays a crucial role in the HD pathogenesis and suggest that attempts to restore striatal BDNF level may have therapeutic effects to the disease.