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RESEARCH PAPERS

J. of Lubrication Tech. 1981;103(3):323-333. doi:10.1115/1.3251664.
Abstract
Topics: Tribology
Commentary by Dr. Valentin Fuster
J. of Lubrication Tech. 1981;103(3):334-336. doi:10.1115/1.3251665.
Abstract
Commentary by Dr. Valentin Fuster
J. of Lubrication Tech. 1981;103(3):337-346. doi:10.1115/1.3251666.

This work is a generalization of previous treatments of the cavitation problem for short journal bearings [1, 2]. Cavitation incipience and the cavitation pattern are dependent on both supply and cavitation pressure levels. The geometrical pattern of the cavity boundary is found to satisfy a universal solution which depends uniquely on the cavitation incipience eccentricity and the operating eccentricity. The same eccentricity parameters also uniquely determine the friction and through-flow characteristics. Radial and tangential force components are dependent on the supply/cavitation pressure ratio in addition to the eccentricity parameters. The results are applicable to journal bearings, shaft-seals, and squeeze-film dampers.

Commentary by Dr. Valentin Fuster
J. of Lubrication Tech. 1981;103(3):350-354. doi:10.1115/1.3251669.
Abstract
Commentary by Dr. Valentin Fuster
J. of Lubrication Tech. 1981;103(3):355-359. doi:10.1115/1.3251673.

The possibility of an incomplete lubricating film due to directed lubrication in hydrodynamic thrust bearings is considered. The free boundaries of the wetted area on a flat sector-shaped pad are determined by a simultaneous iterative solution of the Reynolds equation and a flow equation. Bearing load carrying capacity and power loss are calculated for a variety of inlet geometries, and a comparison is made with a complete fluid film bearing. It is found that bearing performance can be very much affected by the radial location of lubricant supply to the pads.

Commentary by Dr. Valentin Fuster
J. of Lubrication Tech. 1981;103(3):361-370. doi:10.1115/1.3251677.

An asymmetric rotor (19N; 4.3 lb), supported radially and axially by compliant bearings (foil bearings), is subjected to severe excitation by rotating unbalance (43 μm.N; 6100 μin.oz) in the “pitching” mode, at speeds to 50,000 rpm. The resilient, air-lubricated bearings provide very effective damping, so that regions of resonance and instability can be traversed with impunity, with amplitudes and limit-trajectories remaining within acceptable bounds. A novel journal bearing is introduced, in which a resilient support is furnished by the outer turn of the coiled foil-element, initially bent to form an open polygon. The experimental apparatus and procedure are described, and the response of the rotor and flexible support system are copiously documented by oscilloscope records of motion.

Commentary by Dr. Valentin Fuster
J. of Lubrication Tech. 1981;103(3):373-384. doi:10.1115/1.3251681.

Novel thrust bearings, with spiral-groove, flexible membranes mounted on resilient supports, were designed and their performance convincingly demonstrated. Advantages of surface compliance were thus combined with the superior load-capacity of the spiral-groove geometry. Loads of 127–150N (29–33 lb) were comfortably supported on an area 42 cm2 (6.5 in.2 ), at speeds 43,000–45,000 rpm and mean clearances 15–20 μm (600–800 μin.), by these self-acting and air-lubricated bearings. Support-worthiness was proved under exacting conditions, when tested in conjunction with foil journal-bearings and a 19N (4.3 lb)-rotor, excited in a pitching mode by a total unbalance of 43 μm.N (6100 μin.oz).

Commentary by Dr. Valentin Fuster
J. of Lubrication Tech. 1981;103(3):389-397. doi:10.1115/1.3251687.

An analysis of the steady state and dynamic characteristics of floating ring journal bearings has been performed. The stability characteristics of the bearing, based on linear theory, are given. The transient problem, in which the equations of motion for the bearing system are integrated in real time was studied. The effect of using finite bearing theory rather than the short bearing assumption was examined. Among the significant findings of this study is the existence of limit cycles in the regions of instability predicted by linear theory. Such results explain the superior stability characteristics of the floating ring bearing in high speed applications. An understanding of this nonlinear behavior, serves as the basis for new and rational criteria for the design of floating ring bearings.

Commentary by Dr. Valentin Fuster
J. of Lubrication Tech. 1981;103(3):398-403. doi:10.1115/1.3251690.

Numerical solutions for the squeeze film problem, in which one of the surfaces is made of rubber and moves sinusoidally, are presented. Viscoelasticity and in-compressibility of the rubber are taken into account in the numerical procedures. The solutions agree well with the experiments. Variation of the squeeze film shape with time is measured by the moiré topography. This will be one of the best methods for measuring the film thickness when the lubricating surface is made of soft materials like rubber.

Commentary by Dr. Valentin Fuster
J. of Lubrication Tech. 1981;103(3):406-412. doi:10.1115/1.3251695.

This paper presents results from an investigation concerned with vibrational characteristics of compliant-layer water-lubricated bearings. An experimental apparatus emulates the dynamic interactions between the propeller shaft and a water-lubricated elastomeric bearing stave. A computer model predicts the squeal tendency of the experimental apparatus. Correlations are obtained by using the apparatus to verify the predicted squeal tendency. Utilizing the computer model, the effects of varying system parameters on squeal/chatter are determined quantitatively. From the results obtained, it is found that the slope of the friction-speed curve and the effective structural damping are the most important parameters. It is concluded that the essential features of squeal/chatter have been identified and that the phenomenon can be modelled analytically.

Commentary by Dr. Valentin Fuster
J. of Lubrication Tech. 1981;103(3):414-424. doi:10.1115/1.3251698.

A fundamental research into the lubrication mechanism and operation of a new type of rotary shaft seal has been conducted. Optical interference technique was successfully used to study the film profiles with optically smooth elastomer seals. Elastohydrodynamic lubrication was found to exist over a wide range of operating conditions. A study of the other performance variables for the Offset-Seal define its useful application range to be between the Packing-Gland and Face-Seal.

Commentary by Dr. Valentin Fuster
J. of Lubrication Tech. 1981;103(3):428-433. doi:10.1115/1.3251702.

The motion of a flexibly mounted ring in a mechanical face seal is described in its major three degrees of freedom. The equations of motion include fluid film as well as flexible support forces and moments. These equations are linearized using small perturbation analysis. It is shown that for small perturbation the axial motion is uncoupled with the two angular ones and is always stable. A condition for angular stability is derived relating seal operation conditions to its geometry and other design parameters.

Commentary by Dr. Valentin Fuster
J. of Lubrication Tech. 1981;103(3):436-442. doi:10.1115/1.3251706.

A theoretical model is developed for a slider lubricated by its own surface melting. Heat for melting is assumed to be supplied both from viscous dissipation in the liquid film and by conduction from the track at a temperature higher than the melting temperature of the slider. The analysis allows prediction of film thickness and the friction coefficient. The overall behavior results to be clearly dependent on which of the two heat sources is prevailing. In particular, thermal conduction appears to be the cause for a generally much lower friction coefficient with respect to an isothermal case.

Commentary by Dr. Valentin Fuster
J. of Lubrication Tech. 1981;103(3):443-452. doi:10.1115/1.3251707.

An analytical solution for the full thermal field in a journal bearing under isoviscous conditions is presented. The results are for adiabatic bearing surfaces and for isothermal bearing surfaces, with isothermal shaft in all cases. The effects of convection and of dissipation in the film are governed by a single dimensionless parameter, Pe = ρcp ωc2 /k, under the assumption that pressure gradient effects do not influence the thermal field. Results for bulk temperature, heat transfer to bearing surfaces, and for temperature profiles across the film are presented. For small values of Pe, the thermal field is fully-developed, while for large values, dissipation dominates the temperature field and is the primary heat transfer source.

Commentary by Dr. Valentin Fuster
J. of Lubrication Tech. 1981;103(3):453-458. doi:10.1115/1.3251708.

A theoretical analysis was made of the effects of the inclusion of inertia, viscous, and turbulence terms in hydrodynamic lubrication theory is applied to a thrust bearing. The solution to the governing equations is obtained by an iterative numerical method. An improved eddy viscosity model is employed to evaluate the turbulence term. Results are compared with existing measurements made in bearing models and also with other theoretical solutions. The contribution of inertia and viscous terms is discussed in light of the obtained results.

Commentary by Dr. Valentin Fuster
J. of Lubrication Tech. 1981;103(3):459-466. doi:10.1115/1.3251709.

Turbulence makes high speed conventionally designed bearings operate with higher power loss, higher temperature rise, and lower oil flow than would be predicted from conventional laminar analysis. The objective of this paper is to present a new concept for increasing the load/power efficiency of large thrust bearings by a hybrid design employing hydrostatic load support combined with hydrodynamic pads. Self-pressurization using a shaft-center feed to radial ducts in the runner provides reliability fully equal to conventional bearing-fed designs.

Commentary by Dr. Valentin Fuster

DISCUSSIONS

J. of Lubrication Tech. 1981;103(3):354. doi:10.1115/1.3251670.
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Abstract
Commentary by Dr. Valentin Fuster
J. of Lubrication Tech. 1981;103(3):354. doi:10.1115/1.3251671.
FREE TO VIEW
Abstract
J. of Lubrication Tech. 1981;103(3):354. doi:10.1115/1.3251672.
FREE TO VIEW
Abstract
Topics: Cavitation
Commentary by Dr. Valentin Fuster
Commentary by Dr. Valentin Fuster
J. of Lubrication Tech. 1981;103(3):404-405. doi:10.1115/1.3251694.
FREE TO VIEW
Abstract
Topics: Rubber
Commentary by Dr. Valentin Fuster
Commentary by Dr. Valentin Fuster
Commentary by Dr. Valentin Fuster

TECHNICAL BRIEFS

J. of Lubrication Tech. 1981;103(3):467-468. doi:10.1115/1.3251710.

The analytical solution for the normal load carrying capacity of lightly loaded cylinders in combined rolling, sliding and normal motion is obtained. It is shown that the load capacity is inversely proportional to the dimensionless minimum film thickness. The results are presented graphically and approximated in the form of an exponential function.

Commentary by Dr. Valentin Fuster
J. of Lubrication Tech. 1981;103(3):468-470. doi:10.1115/1.3251711.

A list of mobility and impedance definitions is given for a set of full-journal-bearing solutions, including the finite-length-bearing solution.

Commentary by Dr. Valentin Fuster

BOOK REVIEWS

J. of Lubrication Tech. 1981;103(3):471. doi:10.1115/1.3251712.
FREE TO VIEW
Abstract
Commentary by Dr. Valentin Fuster

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