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RESEARCH PAPERS

J. of Lubrication Tech. 1967;89(4):409-415. doi:10.1115/1.3617009.

This paper presents a solution to the problem of hydrodynamic lubrication of journal bearings taking into account the elastic distortions of the shaft and the bearing. The exact solution for determining the elastic deformation for a given pressure distribution around a bearing is given, together with the reiterative procedure adopted to find the pressure distribution which satisfies both the hydrodynamic and elastic requirements of the system. Results are given which have been derived for a material with a Poisson’s ratio of 0.28, but other values such as 0.33 do not incur substantial errors. The results can be applied to a wide range of operating conditions using the nondimensional group of terms suggested in the paper. The bearing is assumed to be infinite in length, and infinite in thickness. The latter assumption is shown to be valid for a particular case where the outside diameter of the bearing shell is 3.5 times the shaft diameter. A further assumption in the calculation is a condition of constant viscosity of the lubricant existing around the bearing.

Commentary by Dr. Valentin Fuster
J. of Lubrication Tech. 1967;89(4):418-424. doi:10.1115/1.3617015.

The externally pressurized bearing may be considered and analyzed as an hydraulic closed-loop servomechanism. The use of restrictor feed devices introduces an inner loop that reduces the gain. The time-dependent flow due to the change in volume with film thickness creates a “lead” break frequency favorable to stability. Fluid compressibility, on the other hand, leads to a “lag” break frequency which, if it approaches or becomes less than the “lead” frequency, results in bearing instability. Analysis by transfer function furnishes fresh insight into EP bearing behavior.

Commentary by Dr. Valentin Fuster
J. of Lubrication Tech. 1967;89(4):425-431. doi:10.1115/1.3617017.

Friction and adhesion coefficients of copper on copper were measured in vacuum (5 × 10−10 to 4 × 10−7 torr) at temperatures ranging from −270 to 1000 F, and in controlled pressures of dry air ranging from 10−9 to 760 torr at 75 F. The effects of duration of exposure of surfaces to vacuum, and the effects of contact duration on adhesion were studied. Friction coefficients were very high (2.2 to over 16) and increased greatly with temperature; adhesion coefficients also increased with temperature, but at given temperatures, were about one-tenth the magnitudes of the friction coefficient.

Commentary by Dr. Valentin Fuster
J. of Lubrication Tech. 1967;89(4):433-438. doi:10.1115/1.3617021.

Shallow grooving in a herringbone pattern has been proposed to enhance the stability of both gas and liquid-lubricated journal bearings. It has been shown theoretically that this possibility is particularly advantageous for unloaded journal bearings. This paper describes corroborating experiments. The experiments included the running of an unloaded bearing up to speeds of 60,000 rpm and the collection of steady-state load-displacement, attitude angle data at intermediate speeds up to and including 60,000 rpm. No sign of bearing whirl instability was detected. There was good correlation between theoretical and experimental data. Design data for the partially grooved journal bearing is included for future designs.

Commentary by Dr. Valentin Fuster
J. of Lubrication Tech. 1967;89(4):439-443. doi:10.1115/1.3617023.

The isothermal Reynolds differential equation of gas film lubrication is written in finite-difference form for numerical analysis of the pressure distribution within spiral-groove thrust bearings and compressors. Appropriate jump equations are presented which provide flow continuity at the land-to-groove interfaces. Gas flow, load support, static stiffness, power consumption, and compressor efficiency are computed and theoretical performance curves are presented for this device. Agreement between computed data and experiment is discussed and presented in graphical form.

Commentary by Dr. Valentin Fuster
J. of Lubrication Tech. 1967;89(4):445-452. doi:10.1115/1.3617026.

An iterative method of calculating the steady-state pressure and temperature distributions in the fluid film for infinitely wide slider bearings is presented. The bearing profile is assumed to be quite general, rendering the method particularly applicable to problems involving thermal or elastic distortion. The viscosity of the lubricant is regarded as a function of temperature and pressure; the density as a function of temperature only. The inertia terms are retained in the simplified Navier-Stokes equation and the energy equation includes the compression work term. Heat transfer between the bearing surfaces and the fluid film are accounted for. Several numerical examples are evaluated and compared with existing solutions. The solution presented is believed to be the most complete to date. A subsequent paper will deal with the effect of thermal distortions of similar geometrical arrangements described herein.

Commentary by Dr. Valentin Fuster
J. of Lubrication Tech. 1967;89(4):453-463. doi:10.1115/1.3617027.

Stress patterns in lubricated rolling-contact elements have been computed from surface pressures and temperatures between pairs of rolling disks, both cylindrical or both crowned, measured by means of evaporated surface transducers. The maximum mechanical shearing stresses computed for both cylindrical and crowned disks proved to be nearly equal to those that would have occurred under static contact, but the calculated depth of those stresses was reduced for cylindrical rollers in dynamic contact. The maximum shear reversals computed for rolling cylindrical disks were noticeably below the corresponding shear differences for the static cases. Local pressure anomalies, such as the pressure spike in the one particular case chosen for investigation, did not seem to alter significantly the shear-stress patterns. Thermal shearing stresses do not appear to be a significant portion of the maximum stress but do dominate over mechanical shearing stresses near the surface of the elements.

Commentary by Dr. Valentin Fuster
J. of Lubrication Tech. 1967;89(4):466-472. doi:10.1115/1.3617031.

The wear and compatibility characteristics of selected bearing materials, including surface coatings and cemented refractory carbides were investigated in support of a pump development program for advanced Rankine cycle space power plants employing high temperature lithium and NaK. Compatibility of candidate materials with 1100-deg lithium in Cb-1 Zr alloy was studied in tilting capsule tests for durations to 7000 hr. The wear behavior of material combinations was evaluated with a rotating disk-static shoe assembly in lithium and NaK to 1000 deg. The best compatibility and wear characteristics were exhibited by high density molybdenum cemented carbides. Carburized Cb-1 Zr alloy wear resistance was inconsistent but, under the best conditions, was nearly equivalent to that of the cemented carbides. Plasma sprayed coatings of tungsten carbide and WC-Co gave encouraging results in NaK, but additional development of the coating process appeared necessary to assure reliable control of adhesion and performance.

Commentary by Dr. Valentin Fuster
J. of Lubrication Tech. 1967;89(4):473-481. doi:10.1115/1.3617035.

This paper discusses the characteristics of the 120 deg bearing as the compressibility parameter Λ is increased from 0 to ∞. At low values of Λ and light loads, the gas bearing behaves as an incompressible lubricated bearing. Curves are developed to show under what conditions of bearing loading, film thickness, and speed the partial gas bearing may be treated by the incompressible theory. The compressibility parameter Λ has a considerable effect on the proper selection of the shoe pivot position and bearing clearance ratio for both maximum load capacity and minimum coefficient of friction. It is shown that the bearing clearance ratio and pivot location can vary considerably and still maintain close to optimum conditions at low compressibility numbers. At higher compressibility numbers, the choice of pivot location has a substantial effect on the bearing load capacity and coefficient of friction. Also discussed are the optimum design ranges of the compressibility number Λ.

Commentary by Dr. Valentin Fuster
J. of Lubrication Tech. 1967;89(4):483-491. doi:10.1115/1.3617038.

The temperature distribution in the lubricating film of journal bearings for the three-dimensional case is obtained by using the results already known regarding the pressure distribution in the film and by integrating the energy equation. Relations for the divergent and convergent zones of the bearing are established by taking into account the viscosity and the side leakage; the distribution of the temperature along the bearing width is also considered. Comparisons between the theoretical values and experimental measurements are also performed, resulting in good agreement.

Commentary by Dr. Valentin Fuster
J. of Lubrication Tech. 1967;89(4):493-498. doi:10.1115/1.3617042.

The stability of a gas bearing is treated by a new procedure in which the bearing film is characterised by its responses to step-jump displacements. Duhamel’s theorem is invoked to generalize these step responses in a system of dynamical equations. Stability is determined by calculation of a “growth factor” for each degree of freedom. Results are presented for the infinitely long self-acting sleeve bearing and for a finite length two-bearing system.

Commentary by Dr. Valentin Fuster
J. of Lubrication Tech. 1967;89(4):499-507. doi:10.1115/1.3617043.

A method for obtaining the performance characteristics of a rotor-tilting pad gas lubricated journal bearing system by solving the appropriate dynamics equations together with the time-transient Reynolds’ equation is outlined. Results for a 4 degree of freedom and an 18 degree of freedom system are given. Comparison with steady-state and experimental results are also discussed.

Commentary by Dr. Valentin Fuster
J. of Lubrication Tech. 1967;89(4):510-519. doi:10.1115/1.3617045.

The paper presents experimental and theoretical data on the axisymmetric hydrostatic thrust bearing with one bonded compliant surface. The theoretical results are exact and are based on linear elasticity theory. The effects of compliance on the behavior of the thrust bearing are discussed and illustrated.

Commentary by Dr. Valentin Fuster

DISCUSSIONS

Commentary by Dr. Valentin Fuster
J. of Lubrication Tech. 1967;89(4):431-432. doi:10.1115/1.3617020.
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Abstract
Commentary by Dr. Valentin Fuster
Commentary by Dr. Valentin Fuster
Commentary by Dr. Valentin Fuster

BOOK REVIEWS

J. of Lubrication Tech. 1967;89(4):521. doi:10.1115/1.3617048.
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Abstract
Commentary by Dr. Valentin Fuster
J. of Lubrication Tech. 1967;89(4):521-522. doi:10.1115/1.3617050.
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Abstract
Commentary by Dr. Valentin Fuster

COMMENTARY

J. of Lubrication Tech. 1967;89(4):523. doi:10.1115/1.3617051.
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Abstract
Commentary by Dr. Valentin Fuster

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