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RESEARCH PAPERS

J. of Lubrication Tech. 1980;102(2):125-129. doi:10.1115/1.3251448.
Abstract
Topics: Tribology
Commentary by Dr. Valentin Fuster
J. of Lubrication Tech. 1980;102(2):133-138. doi:10.1115/1.3251450.

A mixed friction hydrostatic mechanical face seal model is presented. Load support and friction due to mechanical contact and the effect of a phase change are considered. The results show that a phase change within the seal interface leads to a greater fraction of the load being supported by fluid film pressure than for an all liquid or all gas phase seal. As seal operating temperature approaches the boiling point of the sealed fluid, very high leakage is predicted. An explanation for puffing is offered. The effect of various design parameters on two phase seal operation is examined. On a theoretical basis, operation at a higher temperature reduces seal wear rate and friction. The model can be used by seal designers to predict instability and performance for a two phase seal.

Commentary by Dr. Valentin Fuster
J. of Lubrication Tech. 1980;102(2):139-144. doi:10.1115/1.3251451.

The effect of coning on radial forces in face seals having angular misalignment is analyzed. Both the hydrostatic and hydrodynamic components of the resultant radial force are presented. It is shown that the displacement of the primary seal ring due to the action of radial forces is always in a direction which may cause inward pumping. However, in most cases the radial force is very small.

Commentary by Dr. Valentin Fuster
J. of Lubrication Tech. 1980;102(2):145-151. doi:10.1115/1.3251452.

Squeeze effects in a liquid lubricated radial face seal are analyzed. The analysis considers face misalignment with both axial and angular vibrations of the primary seal ring. Translational, rotational, and cross-coupled damping coefficients of the fluid film are derived analytically from a solution of the Reynolds equation utilizing the narrow seal approximation. Results are given for a wide range of practical radius ratios. At each radius ratio, the complete range of angular misalignment—from parallel faces to touch down—is covered. It is shown that squeeze effects in face seals are usually larger than the more familiar hydrodynamic effects. These effects play an important role in the seal’s mechanism of operation and therefore have to be considered in any realistic seal model.

Commentary by Dr. Valentin Fuster
J. of Lubrication Tech. 1980;102(2):153-164. doi:10.1115/1.3251457.

This paper attempts to give a unified treatment of experiments obtained with solid, liquid and boundary lubricants, different plastics, high temperature steels and elastomers. The argument is centered around third body role, load-carrying capacity, transport and continuum mechanics. This study suggests that an extension to general tribology of the continuum approach used in full film lubrication could be profitable.

Commentary by Dr. Valentin Fuster
J. of Lubrication Tech. 1980;102(2):165-170. doi:10.1115/1.3251458.

A single cylinder engine equipped with a transparent cylinder sleeve has been used to develop a technique to make visual investigations of piston ring lubrication behavior and engine oil loss mechanism. This paper describes this apparatus and the development of a laser excited oil fluorescence technique for measuring the oil film thickness change between the piston rings and the transparent cylinder sleeve wall. The amount of oil accumulated in the piston-cylinder clearance spaces above and below the ring pack, and those in the inter-ring spaces, can also be observed. Preliminary results showing oil fluorescence light intensity traces indicate that this technique works very well. Quantitative oil film thickness data should be readily obtainable from these traces once the fluorescent light intensity is calibrated.

Commentary by Dr. Valentin Fuster
J. of Lubrication Tech. 1980;102(2):172-179. doi:10.1115/1.3251462.

The experiments of Mr. Beauchamp Tower and their subsequent interpretation by Professor Osborne Reynolds form the basis of all hydrodynamic lubrication theory. In the experiments described in his second report, Tower made nine pressure tappings in a 157 deg partial arc bearing. Reynolds assumed that the film shape corresponded to a circular bearing and analyzed the results on this assumption. Inverse hydrodynamic theory allows the calculation of the actual film shape from this measured pressure distribution. It is found that the film was a slightly convergent wedge which does not correspond to a fitted bearing as assumed by Tower and certainly not to the clearance bearing assumed by Reynolds. Existing methods of inverse hydrodynamic analysis require the second differential of the pressure profile (or its equivalent in the two-dimensional case) to become zero at some point in the film. The film thickness can be found directly at this point and then elsewhere by the solution of a cubic equation. Two separate and more general methods are developed in this paper in which this requirement for the second differential is unnecessary.

Commentary by Dr. Valentin Fuster
J. of Lubrication Tech. 1980;102(2):182-191. doi:10.1115/1.3251465.

A large number of variables are associated with the design of pivoted pad bearings that makes a generalised approach using charts most difficult. All design offices now have readily available on-line computer terminals that have access to library programs. The development of a library program for this type of bearing is described and discussed. The analysis considers the entire bearing as opposed to the superposition of results of individual pads. This simplifies the solution of the temperature field for each pad and allows the inclusion of turbulence, hot oil carry over and thermal and elastic distortion of each pad. The analysis is verified against three sets of independent experimental results. It is shown that the effect of pad bending is to lower the bearing damping so that the unbalance response is increased.

Commentary by Dr. Valentin Fuster
J. of Lubrication Tech. 1980;102(2):193-200. doi:10.1115/1.3251469.

The paper offers an analysis of finite journal bearings having an axially variable clearance. Such bearings are encountered either as a consequence of manufacturing errors and wear, or as configurations specifically designed to accommodate journal misalignment. The Reynolds equation is solved for the appropriate boundary conditions and film geometry by finite difference methods. Tables of computer solutions and a number of graphs provide the performance characteristics of misaligned bearings for a wide range of parameters. The results show that striking advantages can be achieved by the use of flared bearings for cases of moderate and severe journal misalignment.

Commentary by Dr. Valentin Fuster
J. of Lubrication Tech. 1980;102(2):201-210. doi:10.1115/1.3251470.

The basic tenet of the research reported here has been to develop a fundamental understanding of the mechanism of noise generation in water-lubricated compliant rubber bearings. An experimental model study employed a transparent glass slider rubber against a Buna-N rubber section in order to permit direct measurement of the different aspects of the vibration phenomena, and to be able to observe the type of rubber motion that occurs at the sliding interface. This study has clearly demonstrated that the basic phenomenon is a stick-slip motion of the rubber surface, at times coupled with mechanical resonances of the bearing parts. Shaft torsional resonance does not appear to be involved. The design, geometrical and material conditions that encourage the phenomenon have been established. The direction for improvement is clear, and the paper contains both conclusions and recommendations for corrective means which would lead toward silent operation.

Commentary by Dr. Valentin Fuster
J. of Lubrication Tech. 1980;102(2):213-220. doi:10.1115/1.3251474.

A Grubin-like EHD inlet analysis utilizing a non-linear viscous fluid model with a limiting shear stress is reported. The shear rheological equation requires only a low shear stress viscosity and the limiting shear stress both functions of pressure. Values employed for these properties are taken from measurements on typical lubricants. Reductions of EHD film thickness are found to be up to 40 percent compared with the standard Grubin prediction for typical operating conditions. Slide-roll ratio, limiting shear stress dependence on pressure, and atmospheric pressure value of limiting shear stress are new variables required to determine film thickness with the first two being more important than the last. The EHD film thickness is reduced by increasing slide-roll ratio and/or decreasing the pressure dependence of the limiting shear stress.

Commentary by Dr. Valentin Fuster
J. of Lubrication Tech. 1980;102(2):222-227. doi:10.1115/1.3251478.

The paper deals with the unique functional characteristics that the use of hollow rolling elements induce in a radial type cylindrical roller bearing. The ability to consistently and successfully preload these hollow rollers between the inner and the outer races together with, of course, the necessary but usual degree of precision of the bearing components, provides an effective control of the shaft run-out. This makes the bearing especially suitable for high precision applications. The roller preloading also eliminates the need for a roller guidance from a retainer which, combined with the lighter rollers, generally means higher speed capabilities. In addition to the inherent superior rotational accuracy of the hollow roller bearing, it is also demonstrated as to why, contrary to the common belief, the preloading ability of the hollow rollers results in significant stiffness improvements over, say, a corresponding solid roller bearing. The significance of the roller hollowness is discussed with regard to the stiffness, load capacity and life characteristics of this bearing. Finally, the suitability of the various lubrication systems for this bearing are discussed.

Commentary by Dr. Valentin Fuster
J. of Lubrication Tech. 1980;102(2):229-234. doi:10.1115/1.3251481.

Viscoelastic transition measurements of several lubricants by volume dilatometry to pressures of 1.75 GPa, dielectric transitions at atmospheric pressure on five fluids in a frequency range of 0.2 to 500 kHz and on two fluids in the same frequency range to pressures of 0.55 GPa are reported. Lines of constant rate dilatometry transition, constant rate dielectric transition and constant viscosity are shown to be essentially parallel on a temperature-pressure diagram.

Commentary by Dr. Valentin Fuster
J. of Lubrication Tech. 1980;102(2):236-245. doi:10.1115/1.3251485.

Dry bearing tests have been made with a PTFE fibre/glass fibre/phenolic resin composite against stainless steel to examine the influence of time of sliding, counterface roughness and load. The worn surfaces were examined by optical and scanning electron microscopy, energy dispersive analysis of X-rays (EDAX) and X-ray photoelectron spectroscopy (ESCA). It is shown that the coefficient of friction and the rate of wear are strongly influenced by the formation of third bodies on both sliding surfaces. The structure and composition of these third bodies depend on the time of sliding and the load, but are independent of counterface roughness. Wear of the PTFE composite appears to occur on several scales, and considerable degradation of PTFE is evident within the third body (transfer film) on the counterface. The significance of these observations to the measured friction and wear rates is discussed.

Commentary by Dr. Valentin Fuster
J. of Lubrication Tech. 1980;102(2):247-251. doi:10.1115/1.3251488.

Visualization of the friction process of a Cr.Ni Steel pin running on a disk of similar material under nitrogen has shown that a built-up edge (b.u.e.) is gradually formed and eliminated at contact. The construction of the b.u.e. is described. Metallurgical sections of b.u.e. formed under different conditions are analysed and confirm mechanisms suggested by visualization. Both visualization and b.u.e. examinaton point to the importance of flow transport in friction processes.

Commentary by Dr. Valentin Fuster
J. of Lubrication Tech. 1980;102(2):253-255. doi:10.1115/1.3251491.

Two advanced carburizing grade gear steels were evaluated and compared against an AMS 6260 baseline material. Each material was evaluated on three lubricants (an unformulated ester basestock, a qualified MIL-L-23699B lubricant, and an advanced MIL-L-23699 type lubricant) to determine their gear scuffing/scoring capacities. The results show that (a) a 3Ni-4.5Mo alloy is superior to a 3Ni-2Cu alloy and to the AMS 6260 alloy with the lubricants evaluated, (b) the 3Ni-2Cu alloy is superior to the AMS 6260 with the fully formulated lubricants, and (c) the advanced MIL-L-23699 type lubricant showed significant load carrying capacity improvements for all three gear steels.

Commentary by Dr. Valentin Fuster

REPORTS

J. of Lubrication Tech. 1980;102(2):130-132. doi:10.1115/1.3251449.
FREE TO VIEW
Abstract
Commentary by Dr. Valentin Fuster

DISCUSSIONS

J. of Lubrication Tech. 1980;102(2):151. doi:10.1115/1.3251453.
FREE TO VIEW
Abstract
Commentary by Dr. Valentin Fuster
J. of Lubrication Tech. 1980;102(2):151. doi:10.1115/1.3251454.
FREE TO VIEW
Abstract
J. of Lubrication Tech. 1980;102(2):151. doi:10.1115/1.3251455.
FREE TO VIEW
Abstract
J. of Lubrication Tech. 1980;102(2):152. doi:10.1115/1.3251456.
FREE TO VIEW
Abstract
Commentary by Dr. Valentin Fuster
J. of Lubrication Tech. 1980;102(2):228. doi:10.1115/1.3251480.
FREE TO VIEW
Abstract
Topics: Rollers
Commentary by Dr. Valentin Fuster

ERRATA

Commentary by Dr. Valentin Fuster

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