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RESEARCH PAPERS

J. of Lubrication Tech. 1973;95(2):113-122. doi:10.1115/1.3451743.

The authors describe a numerical procedure for the solution of the problem of hydro-dynamic lubrication in the hydrostatic extrusion process. The lubricant is assumed to be a Newtonian fluid and in this preliminary analysis it is assumed that the yield strength of the worked material remains constant. Elastic deformation of the billet as it enters and leaves the die is considered but this effect is found to have only a small influence upon the thickness of the lubricant film which is generated. Thermal effects arising from plastic deformation of the billet and viscous dissipation in the lubricant film are also considered. Theoretical results are presented showing the influence of die angle and reduction ratio upon values of film thickness and extrusion pressure for two materials.

Commentary by Dr. Valentin Fuster
J. of Lubrication Tech. 1973;95(2):123-130. doi:10.1115/1.3451744.

High reliability requirements of aircraft gas turbine mainshaft ball bearings necessitate reliable methods for estimating fatigue lives in the early failure region of the life dispersion. Economical and rapid comparisons of surface fatigue lives of modern track materials demand extrapolation from limited numbers of rig results, using a statistical distribution which gives reasonable rectification of early failures. The investigation indicates that lognormal distributions are more satisfactory than Weibull distributions for low failure probabilities.

Commentary by Dr. Valentin Fuster
J. of Lubrication Tech. 1973;95(2):132-134. doi:10.1115/1.3451747.

Experiments on the sliding of boron carbide on boron carbide in atmospheres of dry air and water vapor at room temperature have shown the frictional behavior of boron carbide to be similar to that of graphite. As boron carbide has not a lamellar structure this is surprising. Electron diffraction studies have shown that the surface of the boron carbide probably contained graphite, thus explaining the frictional behavior.

Commentary by Dr. Valentin Fuster
J. of Lubrication Tech. 1973;95(2):137-145. doi:10.1115/1.3451752.

The purpose of this study on the turbulent lubricant film is: 1 To give a brief outline of a new theory called bulk-flow theory; 2 To investigate to what extent results of theories based on law of wall and mixing length concept agree with the newly developed theory; 3 To provide a theoretical basis for the design of bearings lubricated by fluids of low kinematic viscosity.

Commentary by Dr. Valentin Fuster
Commentary by Dr. Valentin Fuster
Commentary by Dr. Valentin Fuster
J. of Lubrication Tech. 1973;95(2):166-172. doi:10.1115/1.3451759.

In a number of previous papers a hydrodynamic theory of lubrication of rough bearing surfaces has been developed. The present paper describes the application of this theory to the analysis of the full journal bearing of finite width. The analysis demonstrates how the roughness influences the characteristics of the bearing and also shows how roughness interacts with features of nominal geometry and operating factors to determine the bearing response.

Commentary by Dr. Valentin Fuster
J. of Lubrication Tech. 1973;95(2):173-179. doi:10.1115/1.3451760.

An experimental study was made of the performance of porous bronze bearings under different operating conditions. A PV value of 50,000 psi ft/min was found to be too high for the assembly used when the bearings were lubricated only by the oil initially provided within their structure. Tests at a PV value of 33,000 psi ft/min gave satisfactory results. The coefficient of friction was found to vary with load and to be almost independent of speed for the bearings tested under boundary lubrication conditions. Except for relatively light loads and moderate and higher speeds, the bearings operate under boundary lubrication conditions. When pressurized oil was supplied to the bearings, it was found that, for the same operating conditions, porous bearings run at higher eccentricity ratios than solid bearings, as predicted by theoretical analyses.

Commentary by Dr. Valentin Fuster
J. of Lubrication Tech. 1973;95(2):181-186. doi:10.1115/1.3451764.

An approximate analysis of the magnetohydrodynamic flow between rotating disks shows that the torque of rotating disks is strongly affected by the wall conductance. Also, considering the application to a viscous coupler or a hydrostatic thrust bearing operating under the extreme temperature, the operating characteristics of such MHD devices are analyzed.

Commentary by Dr. Valentin Fuster
J. of Lubrication Tech. 1973;95(2):187-194. doi:10.1115/1.3451767.

The classical hydrodynamic theory of fluid film lubrication as described by Reynolds’ equation assumes isothermal conditions in the film. Such conditions may never exist in many engineering applications. A common practice is to calculate bearing performance with isothermal conditions at an average film temperature. This paper presents results on the load-carrying capacity of the film when thermal homogeneity does not exist. An empirical procedure is proposed for the prediction of the thermohydrodynamic behavior of the film. A hysteresis-type phenomenon in the pressure-temperature relationship is also observed.

Commentary by Dr. Valentin Fuster
J. of Lubrication Tech. 1973;95(2):195-202. doi:10.1115/1.3451768.

Externally pressurized porous journal gas bearing is analyzed theoretically in this paper by introducing a flow model, in which the flow in the porous bushing is substituted by a flow in an assumed thin layer. The surface loading effect due to machining is taken into account as the increase of resistance to the gas flow from porous media to bearing clearance. The theoretical results are investigated experimentally, yielding a comparatively good conformity between them enough to certify the analysis. Then, the optimum design conditions of the externally pressurized porous journal gas bearing are obtained by theoretical calculations with considering the surface-loading effect.

Commentary by Dr. Valentin Fuster
J. of Lubrication Tech. 1973;95(2):204-207. doi:10.1115/1.3451771.

Criteria of stability of externally pressurized gas bearings fed through a porous wall are derived from a quadratic Liapunov functional, taking into account the transverse motion of the bearing and the pressure distributions inside the bearing clearance and the porous wall. The stability condition found from this Liapunov functional reduces to the condition previously given by some authors, when the pressure distribution is assumed to be the same as in steady state. Finally, it is shown that the stability domain is increased by diminishing the effective porosity and the thickness of the porous wall.

Commentary by Dr. Valentin Fuster
J. of Lubrication Tech. 1973;95(2):208-215. doi:10.1115/1.3451772.

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.

Commentary by Dr. Valentin Fuster
J. of Lubrication Tech. 1973;95(2):217-220. doi:10.1115/1.3451775.

The authors present an equation describing the pressure distribution in the supersonic domain, for a lightly loaded bearing, including a friction factor as an explicit term. This paper contains also a few experimental curves showing the effect of rounding the edge of an inherently compensated orifice.

Commentary by Dr. Valentin Fuster
J. of Lubrication Tech. 1973;95(2):222-235. doi:10.1115/1.3451779.

A general, easily implemented technique is developed by which stability maps may be determined for gimbaled, gas-lubricated, spiral-grooved thrust bearings. This technique is based upon the spectral analysis (frequency domain) method in which the neutrally stable states of the stator-gimbal system are determined through solution of the system’s characteristic equations. The method has proven effective for conducting low-cost investigations of the sensitivity of system instability thresholds to changes in various system design parameters. Containing data valid for a wide range of gimbal inertias, stability maps are presented for a range of bearing compressibility numbers, for several bearing geometries, and for several values of mechanical damping in order to illustrate both the power of the technique and also its effectiveness. Limited experimental information which is presently available verified the essential features of the corresponding stability maps. The technique has been reduced to a form usable in the design of gas bearings for use in gas turbine engines.

Commentary by Dr. Valentin Fuster
J. of Lubrication Tech. 1973;95(2):236-241. doi:10.1115/1.3451780.

Many relationships between viscosity or its reciprocal, fluidity, and temperature have been proposed for liquids. None except the empirically modified ASTM chart have proven satisfactory over extended temperature ranges. We here note that by plotting the kinematic fluidity (φkin ) against the square of the absolute temperature (deg K 2 ) we obtain linear relationships for a wide variety of organic liquids at kinematic viscosities less than about 1.67 centistokes (or fluidities above about 0.60 reciprocal centistokes). The generality of the relationship appears to justify the use of the equation,

φkin = a + bT2,
as an interpolation formula for organic liquids in the low viscosity region.

Commentary by Dr. Valentin Fuster
J. of Lubrication Tech. 1973;95(2):242-246. doi:10.1115/1.3451783.

A mineral oil and a lithium-based mineral oil grease containing molybdenum disulfide are tested under boundary conditions on the Shell Four Ball Testing Machine and on a modified Reichert Wear Balance. The investigation of the wear tracks by scanning electron microscopy and microprobe analysis shows that a continuous MoS1 film is formed on the metal surface under mild friction conditions. Under extremely severe conditions, however, the MoS2 reacts chemically. It is found that molybdenum diffuses into the steel surface forming intermetallic compounds and carbides which improve the quality of the steel surface. The effect of time and pressure on the thickness of the molybdenum disulfide is determined and the amount of wear reduction by chemical reaction of molybdenum disulfide with the steel surface is compared to that of a traditional EP-additive.

Commentary by Dr. Valentin Fuster
J. of Lubrication Tech. 1973;95(2):249-254. doi:10.1115/1.3451787.

To measure the absolute oil film thickness or the journal center locus in con-rod big-end bearings of a practical automobile engine, a special new device and procedure have been developed. By means of this method, the measurement could be carried out stably up to full load at 5000 rpm. These measurements revealed that the journal travels along the vicinity of bearing surface by the inertia force. In the combustion period, however, the journal center passes near the center point of the bearing. On the other hand, under a misalignment condition, the minimum oil film thickness depends on the combustion pressure. Therefore in the future many of the problems related to con-rod big-end bearings will be resolved by this method.

Commentary by Dr. Valentin Fuster

DISCUSSIONS

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
Commentary by Dr. Valentin Fuster
J. of Lubrication Tech. 1973;95(2):260. doi:10.1115/1.3451795.
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Abstract
Topics: Lubrication

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