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RESEARCH PAPERS: Lubrication Symposium Papers

J. of Lubrication Tech. 1970;92(1):1-12. doi:10.1115/1.3451325.

The validity of experimental simulation of ball-bearing lubrication by a rolling-disk apparatus has been scrutinized mathematically, with specific attention to films generated for thickness measurements by X-rays. Emphasis was given to distinctive ball-bearing features, such as surface slip and related thermal effects alterable by geometric expansion. For a representative ball bearing, rigorous simulation demanded unattainble disk speeds and hampered X-ray measurements of film thickness, but experiments were made feasible through acceptable relaxation of carefully chosen details. Several experiments were performed under fairly severe combinations of load, speed, and temperature. Specific results with a synthetic paraffinic oil under maximum pressure of 200,000 psi at high speeds showed films about 20 microin. thick at 200 F but indicated only about one microin. at 600 F. Even the thin films allowed little surface contact, though they may have increased susceptibility to damage from sliding.

Commentary by Dr. Valentin Fuster
J. of Lubrication Tech. 1970;92(1):16-20. doi:10.1115/1.3451314.

A review of current rolling bearing load rating and life prediction practices is given, based on the ASA standard method. Experimental results show the existence of life-factors in addition to those encompassed in the ASA standard. A more general rolling contact fatigue theory is sketched but is not yet at a stage where it can be applied to practical life calculations. Therefore a simple generalization of ASA life formulas is proposed for practical use, which accounts for material and environmental variables by multiplicative factors and permits life prediction for any desired reliability using another, tabulated factor.

Commentary by Dr. Valentin Fuster
J. of Lubrication Tech. 1970;92(1):23-31. doi:10.1115/1.3451330.

Rolling-element fatigue tests were conducted with 120-mm bore angular-contact ball bearings made of AISI M-50 steel with a synthetic paraffinic oil, a fluorocarbon, and a 5P4E polyphenyl, ether. At 600 deg F under a low-oxygen environment, the synthetic paraffinic oil and the fluorocarbon gave bearing lives approximately 14 and 3 times AFBMA-predicted (catalog) life, respectively. With the polyphenyl ether, bearing life was less than AFBMA-predicted (catalog) life in an air environment at 600 deg F. At temperatures of 400 and 500 deg F with the synthetic paraffinic oil there was no statistical difference in life from those bearings tested with the same fluid at 600 deg F. For the synthetic paraffinic oil and the fluorocarbon, bearing fatigue was subsurface initiated. For the polyphenyl ether, bearing failure was mainly from surface distress, wear, and superficial pitting.

Commentary by Dr. Valentin Fuster
J. of Lubrication Tech. 1970;92(1):34-38. doi:10.1115/1.3451333.

The linear motion assembly is a type of rolling bearing used to support and guide a translating member along a round shaftway. The load-carrying adequacy of this bearing for a given application is evaluated in the same way as for conventional rolling bearings by determining a statistical fatigue life. This paper presents an analytical development of the equations for dynamic capacity from which fatigue life can be calculated. Contact deflection and the effects of preload are also examined.

Commentary by Dr. Valentin Fuster
J. of Lubrication Tech. 1970;92(1):39-51. doi:10.1115/1.3451336.

Experimental results indicate that oil supply can have a significant effect on cage and roller motion in a lubricated roller bearing. A theoretical analysis is presented which enables cage and roller motion, for various operating conditions, to be predicted. The theoretical results imply that reducing the oil supply to a minimum value required to maintain full hydrodynamic conditions, reduces cage slip by up to 75 percent of its fully flooded value. This conclusion is consistent with existing experimental evidence.

Commentary by Dr. Valentin Fuster
J. of Lubrication Tech. 1970;92(1):54-58. doi:10.1115/1.3451340.

The deformation bands which form in cyclically stressed AISI 52100 steel inner rings (during rolling contact) are studied by transmission electron microscopy. These deformation bands are regions where the temper carbides have dissolved and a well-developed cell structure has formed. Many of the deformation bands are bordered by lenticular-shaped carbides which form after prolonged cyclic stressing. The deformation bands were tempered in the electron microscope and most were found to be free of excess carbon since no precipitation of carbides occurred at normal tempering temperatures. In one specimen there was profuse precipitation of carbides at the cell walls indicating that an excess of free carbon had segregated around dislocations. It is concluded the regions free of excess carbon are due to the nucleation and growth of a lenticular carbide while no lenticular carbide formed at the deformation band which was supersaturated with carbon.

Commentary by Dr. Valentin Fuster
J. of Lubrication Tech. 1970;92(1):59-69. doi:10.1115/1.3451343.

The paper evaluates the influence of damped, linear flexibly mounted rolling-element bearings on dynamic rotor unbalance response. The system analyzed is treated as a general four degree of freedom unbalanced rotor mounted on damped flexible supports and includes rotor gyroscopic effects. The rotor equations of motion are solved for synchronous precession over a wide range of speeds for various support conditions. Rotor performance curves on bearing amplitude, forces transmitted, phase angles as a function of speed for various values of support damping are computer plotted to illustrate rotor and bearing performance over a wide range of speed and operating parameters. Results indicate that forces transmitted to the bearings by the rotor synchronous unbalance response can be dramatically reduced by proper design of the bearing support characteristics.

Commentary by Dr. Valentin Fuster
J. of Lubrication Tech. 1970;92(1):76-81. doi:10.1115/1.3451347.

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.

Commentary by Dr. Valentin Fuster
J. of Lubrication Tech. 1970;92(1):83-86. doi:10.1115/1.3451352.

Rolling friction was increased by flange contact and by sand or leather on surfaces. It was but slightly decreased by water. It could be increased by a thick oil film and decreased by a thinner one. Increasing the wheel hardness diminished rolling friction. Roughness raised static resistance with little effect on kinetic.

Commentary by Dr. Valentin Fuster
J. of Lubrication Tech. 1970;92(1):89-94. doi:10.1115/1.3451358.

An elastohydrodynamic solution for the spinning torque of a ball spinning without rolling in a non-conforming groove is presented. The solution is compared with experimental results using a synthetic paraffinic oil as the lubricant. A modified pressure-viscosity relation is proposed. The theory predicts increase in torque with stress and spinning speed and decreasing conformity. Good agreement was obtained between theoretical predictions and experimental results.

Commentary by Dr. Valentin Fuster
J. of Lubrication Tech. 1970;92(1):97-101. doi:10.1115/1.3451362.

Using high oil-flow rates, 6-in-bore tapered roller thrust bearings were operated in a speed range of 3600 fpm to 10800 fpm with loads up to 70,000 lb. Bearing operating temperature is considered to be the principal criterion of operation. The effect of lubricating systems, speed, load, oil-flow rates, lubricant viscosity, and oil-inlet temperature on the operating temperature is demonstrated. The test-rig results are generalized by means of dimensional analysis enabling the designer to predict operating temperature for various operating conditions of speed, load, oil-flow rates, and oil-inlet viscosity.

Commentary by Dr. Valentin Fuster
J. of Lubrication Tech. 1970;92(1):105-111. doi:10.1115/1.3451280.

This paper compares theoretical and experimental results on the friction-induced heating in thrust-loaded ball bearings at constant speed. Heat transfer and friction heat-generation models are developed for the bearings using computer techniques. The comparisons indicate that the models are reasonable since the predictions are within ±10 percent of the measured values. More work is needed, however, before a more accurate prediction technique will be available.

Commentary by Dr. Valentin Fuster
J. of Lubrication Tech. 1970;92(1):113-117. doi:10.1115/1.3451285.

The Basic Oxygen Furnace comprises a tiltable vessel supported by two trunnions in large roller bearings. To accommodate thermal expansion, the floating bearing is mounted on a deep curved beam which moves axially on two linear bearings. Under loads of 1 to 2 million pounds, the elastic deflection of this beam alters the static load capacity of the roller bearing. This paper describes a computer assisted analysis based on Castigliano’s First Theorem for determining the effective bearing capacity, and secondly for optimizing the beam design.

Commentary by Dr. Valentin Fuster
J. of Lubrication Tech. 1970;92(1):121-127. doi:10.1115/1.3451289.

A general analytical technique is presented for the evaluation of rolling element bearings when their structural support significantly influences the equilibrium solution. A cylindrical roller bearing supported by an elastic outer housing with two stiff leg supports is analyzed to illustrate the application of this computer oriented method. Experimental determination of the roller load distribution by “footprint” measurement techniques shows excellent agreement with the analytical predictions. The method of solution is outlined with sufficient detail to enable the cooperation of structural and bearing analysis in the solution of a class of problems requiring both disciplines.

Commentary by Dr. Valentin Fuster
J. of Lubrication Tech. 1970;92(1):129-134. doi:10.1115/1.3451292.

Thrust load transmission at the contact areas of roller ends and flanges occurs under conditions of pure sliding. Recent theoretical and experimental investigations showed that with adequately designed roller ends and flanges and with a satisfactory lubricant high thrust loads can be accommodated over a wide speed range with fully hydrodynamic lubrication. The conventional methods used for the determination of the safe thrust load should be revised and supplemented. Oil viscosity should be introduced as an important parameter. Contrary to present opinion the hydrodynamic load-carrying capacity at the flange increases with increasing speed. This new knowledge broadens the application range of radial cylindrical roller bearings.

Commentary by Dr. Valentin Fuster
J. of Lubrication Tech. 1970;92(1):138-142. doi:10.1115/1.3451298.

This paper presents the analysis of the stress field in a hollow sphere in the vicinity of the contact area. The sphere is subjected to a normal load applied through a flat plate. The elastic contact shape and extent are developed for a load of 1000 lb applied to a 1-in-dia hollow ball with a 0.08-in-thick wall. Hollow ball shell bending stresses have a significant effect upon the subsurface stress field. Fatigue life estimates for the hollow ball vary significantly depending upon the selection of decisive stress amplitude. Comparison of the maximum value and location of the reversing orthogonal subsurface shear stress with solid ball data according to the Lundberg-Palmgren dynamic life theory predicts a 91.6 percent life reduction for the hollow ball contact. The use of the unidirectional subsurface shear stress results in a prediction of hollow ball contact life over 30 times the solid ball contact life.

Commentary by Dr. Valentin Fuster
J. of Lubrication Tech. 1970;92(1):145-153. doi:10.1115/1.3451305.

The elastohydrodynamic problem of normal approach of two spherical bodies is studied and the lubrication and elasticity equations governing this type of motion are established. Numerical solutions to the general case accounting for elastic deformation of the bodies and pressure dependent viscosity are presented. It is found that for values of central film thickness that are not too small, the load and relative approach velocity is much more influenced by the increase of viscosity with pressure than by the effects of elastic distortion. Once the separation of the two surfaces becomes small enough, however, the effects of elastic deformation will profoundly influence all aspects of the motion. The transition film thickness HT at which this change takes place is sharply defined and for metallic contacts lubricated with mineral oils quite small, even compared to the surface roughness. Very high pressure—considerably in excess of the Hertzian maximum pressure corresponding to the load—can be generated by the normal approach motion. The maximum value of pressure is generated when film thickness reaches its transition value HT for the load in question. For loads sufficiently large to generate a high enough pressure in the oil film a small increase in load will cause a large increase in maximum pressure. Once the pressure has reached a high enough value it becomes extremely sensitive to a further increase in load.

Commentary by Dr. Valentin Fuster
J. of Lubrication Tech. 1970;92(1):155-161. doi:10.1115/1.3451310.

A numerical solution of the elastohydrodynamic film thickness in an elliptical contact is developed. The two-dimensional Reynolds’ equation in the inlet region is solved by a finite-difference method. The deformation contour in the inlet region is calculated according to the classical Hertz theory for elliptical contacts. Results are presented as side leakage film reduction factors, which are defined as the ratios of the film thickness of the finite contact to that calculated by a line contact theory based on the same maximum Hertz stress. The results obtained for a b/a → ∞, which corresponds to a line contact, and for b/a = 1, which corresponds to a circular contact, agree with those obtained in [2]. Comparison with experimental data [1] indicates that this theory predicts a film thickness slightly higher than those measured by the experiment.

Commentary by Dr. Valentin Fuster
J. of Lubrication Tech. 1970;92(1):163-174. doi:10.1115/1.3451313.

This paper reports the measurement of 296 combinations of load, roller diameter, and plate hardness. The diameters of the steel rollers ranged from 1/16 to 4 in. inclusive. The hardness of the steel plates ranged from 42 Rc to 61 Rc. Two series of tests are also included for titanium plates having a hardness of 40 Rc and 43 Rc, respectively. Equations are derived from this experimental data which can be used to estimate the depths of permanent indentation for a large range of roller diameters, plate hardness, and loads.

Commentary by Dr. Valentin Fuster

DISCUSSIONS

Commentary by Dr. Valentin Fuster
Commentary by Dr. Valentin Fuster
J. of Lubrication Tech. 1970;92(1):38. doi:10.1115/1.3451335.
FREE TO VIEW
Abstract
Topics: Motion
Commentary by Dr. Valentin Fuster
Commentary by Dr. Valentin Fuster
Commentary by Dr. Valentin Fuster
Commentary by Dr. Valentin Fuster
Commentary by Dr. Valentin Fuster
Commentary by Dr. Valentin Fuster

TECHNICAL BRIEFS

J. of Lubrication Tech. 1970;92(1):178-179. doi:10.1115/1.3451320.
Abstract
Commentary by Dr. Valentin Fuster
J. of Lubrication Tech. 1970;92(1):179-180. doi:10.1115/1.3451321.

The complete film solution for the squeeze film in an infinitely long journal bearing contains an arbitrary constant. When only positive pressure regions are retained, this constant influences the load capacity. Several different values have been used for this constant. Its value is determined here so that the infinitely long journal bearing is the limiting case of the finite journal bearing.

Commentary by Dr. Valentin Fuster
J. of Lubrication Tech. 1970;92(1):181-182. doi:10.1115/1.3451322.
Abstract
Topics: Rotors , Whirls
Commentary by Dr. Valentin Fuster

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