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AWARDS

J. of Lubrication Tech. 1979;101(2):113-114. doi:10.1115/1.3453286.
FREE TO VIEW
Abstract
Commentary by Dr. Valentin Fuster
J. of Lubrication Tech. 1979;101(2):163. doi:10.1115/1.3453303.
FREE TO VIEW
Abstract
Commentary by Dr. Valentin Fuster

PROFILES

J. of Lubrication Tech. 1979;101(2):115-119. doi:10.1115/1.3453287.
FREE TO VIEW
Abstract
Topics: Tribology
Commentary by Dr. Valentin Fuster

RESEARCH PAPERS

J. of Lubrication Tech. 1979;101(2):120-128. doi:10.1115/1.3453288.

The unbalance response and stability of centrally preloaded symmetric rigid rotors are investigated. Steady state solutions for unbalance transmissibilities, orbit eccentricity radii, and stability are presented for rotors running in hydrodynamic journal bearings and in rolling element bearings which are supported in squeeze film bearings. The Ocvirk and Warner approximations are used to evaluate the fluid film forces, rendering the data applicable to any length/diameter ratio. Both pressurized (2π film) and unpressurized (π film) oil supply are considered. Pressurization has a far reaching influence on the steady state behavior of both journal and squeeze film bearings. For unpressurized bearings, conditions of multistable operation and for stability are depicted, with journal bearings exhibiting ‘half frequency whirl’ possibilities as well. The error involved in predicting vertical bearing behavior by assuming an equivalent unidirectional load equal to the unbalance load is demonstrated. For pressurized bearings multistable operation is eliminated but both squeeze film and journal bearings are unstable for most length/diameter ratios in the absence of external radial stiffness. The stabilizing effect of superimposed external radial stiffness on pressurized bearings is clearly demonstrated. While pressurized journal bearings can run stably, they are less suited than pressurized squeeze film bearings for vibration isolation.

Commentary by Dr. Valentin Fuster
J. of Lubrication Tech. 1979;101(2):129-137. doi:10.1115/1.3453289.

This paper describes a theoretical and experimental investigation into the nonlinear characteristics of the eight coefficients which specify the lateral flexibility of a hydrodynamic journal bearing. Coefficient calculations allowed viscosity to vary with temperature, and pressure, and examined a range of positive and negative displacements and velocities. Experimental techniques have been developed in which coefficients were deduced from specially chosen, imposed vibration orbits arising from two mutually perpendicular external oscillating forces of variable relative magnitude and phase. Journal centre displacement and velocity were measured using high speed data logging equipment. Coefficients are defined in terms of a “zero” value and linear gradient. Using realistic criteria, measured coefficient non-linearity was found to be significant at eccentricity ratios greater than 0.78. Theory adequately predicted some “zero” values but not gradients. An improvement in the coefficient prediction may depend on the inclusion of some previous history dependent factors.

Commentary by Dr. Valentin Fuster
J. of Lubrication Tech. 1979;101(2):140-144. doi:10.1115/1.3453294.

An isothermal theory of fluid-film flows of differential fluids of complexity n is developed on the basis of a complete dimensional analysis. Within that particular geometrical configuration and provided that the Deborah number is small, such fluids cannot be distinguished from the far more special Rivlin-Ericksen material of complexity 3. It is shown afterwards that the use of a method of resolution similar to that of Reynolds requires to reduce the field of rheological models or the number of geometrical dimensions. The corresponding “generalized Reynolds’ equations” are then deduced: one in 3 dimensions, available for general viscous fluids; one in 2 dimensions, available for Stokesian fluids.

Commentary by Dr. Valentin Fuster
J. of Lubrication Tech. 1979;101(2):145-152. doi:10.1115/1.3453295.

An analytic solution is presented for the flow of a viscoelastic fluid between arbitrary but sufficiently smooth two-dimensional surfaces, one of which is subjected to small high frequency oscillations normal to the other. The results are presented in terms of the complex viscosity parameters of linear viscoelasticity, and are valid for any simple viscoelastic fluid, provided the oscillation amplitude is sufficiently small. Fluid inertia effects are included although convective inertia terms are shown to be negligible through order-of-magnitude considerations. The resulting linearized equations of motion can be solved through conventional means by techniques established in earlier works. Solutions for the velocity field, pressure distribution, and load are presented in terms of the Reynolds and Deborah numbers. Two illustrative cases are demonstrated—the tapered thrust bearing and the partial journal bearing. Unusual resonance effects in pressure and load are exhibited as the oscillation frequency (or Reynolds number) is increased for a particular fluid.

Commentary by Dr. Valentin Fuster
J. of Lubrication Tech. 1979;101(2):154-160. doi:10.1115/1.3453299.

Several recent technical papers have discussed the advantages of various designs of thrust bearings by comparing the power losses of the different type bearings. However, great care must be exercised to ensure that the comparisons are fair. There are many external factors that influence loss, such as oil flowrate, clearance, supply temperature and so on. Unless compensation for these external factors is included in the analysis, the power loss comparisons may be misleading. This paper attempts to show both qualitatively and quantitatively the influence that various external factors have on bearing power loss. It has been determined experimentally that oil flowrate adjustment can vary power loss by as much as 150 percent. The choice of radial or tangential discharge can reduce power loss by 60 percent, while the actual size of the discharge can influence power loss by 50 percent. Varying the bearing end play has little effect on measured power loss.

Commentary by Dr. Valentin Fuster
J. of Lubrication Tech. 1979;101(2):164-169. doi:10.1115/1.3453304.

A special 60 mm bore cylindrical roller bearing was designed to support the radial and thrust loads developed by a spiral bevel input in a Blackhawk size helicopter transmission. Two prototype bearings were fabricated and tested in a laboratory environment at various loads and speeds simulating that of the application, culminating in a combined load of 7.12 kN radially and 6.79 kN axially at 21,500 rpm. Lubrication was provided by circulating Mil-L-23699 synthetic lubricant into the bearing from jets located on each side and through inner ring supply holes directing the flow to the flange surfaces. Thirty-two hours of operation were accumulated. Detailed examination of the bearing surfaces conducted visually and using the scanning electron microscope established that no abnormal deterioration of the load-supporting contact surfaces had been experienced. It was concluded that the bearing performed satisfactorily and warrants further consideration for application in helicopter transmissions. In addition, an experimental test series was conducted to evaluate bearing performance under predominant thrust loading. This was completed at 1.3 × 106 Dn maintaining the applied axial load at 6.79 kN while reducing the radial load until a thrust to radial load ratio of 9.5 was achieved without difficulty. The condition of the load-supporting contact surfaces after this test was again quite good although the contact patterns were altered. It was concluded that the bearing design also has the potential to operate in this more severe loading environment.

Commentary by Dr. Valentin Fuster
J. of Lubrication Tech. 1979;101(2):171-176. doi:10.1115/1.3453307.

Ball bearings were fatigue tested with a noncontaminated MIL-L-23699 lubricant and with a contaminated MIL-L-23699 lubricant under four levels of filtration. The test filters had absolute particle removal ratings of 3, 30, 49, and 105 microns. Aircraft turbine engine contaminants were injected into the filter’s supply line at a constant rate of 125 milligrams per bearing hour. Bearing life and running track condition generally improved with finer filtration. The experimental lives of 3- and 30-micron filter bearings were statistically equivalent, approaching those obtained with the noncontaminated lubricant bearings. Compared to these bearings, the lives of the 49-micron bearings were statistically lower. The 105-micron bearings experienced gross wear. The degree of surface distress, weight loss, and probable failure mode were dependent on filtration level, with finer filtration being clearly beneficial.

Commentary by Dr. Valentin Fuster
J. of Lubrication Tech. 1979;101(2):180-187. doi:10.1115/1.3453312.

A derotation prism was used to produce a stationary image of balls deflecting a portion of the separator. Ball to cage contact forces in a 110 mm bearing at speeds to 12,000 rpm were found to be 25 N (five lb) maximum. Inner race land contact force was found to vary up to 20 N (four lb).

Commentary by Dr. Valentin Fuster
J. of Lubrication Tech. 1979;101(2):190-197. doi:10.1115/1.3453316.

The effect of the deformation of an automotive connecting-rod on the oil film characteristics are studied. The simultaneous elastic deformation and pressure distribution are obtained by iterative methods in steady-state conditions under realistic speeds and loads (5500 rpm, 25,000 N). Plane elasticity relations are used in this study. The following parameters are investigated: —bearing characteristics: bearing thickness B and bearing clearance C, —operating conditions: journal speed N and applied load W, —lubricant: viscosity μ0 and piezoviscous coefficient α. As a result of the deformation, the maximum pressure and the attitude angle are decreased and the relative eccentricity is greatly increased. The minimum oil film thickness is slightly but systematically decreased. The piezoviscosity effect is noticeable only at high loads: it increases slightly the oil film thickness and the maximum pressure. An empirical dimensional equation for the minimum oil film thickness hm is derived numerically for the bearing considered. Thus:

hm∼μ0NW0.5(1+0.06 108α)B0.12C0.09

Commentary by Dr. Valentin Fuster
J. of Lubrication Tech. 1979;101(2):201-206. doi:10.1115/1.3453321.

The effects of phosphorus on the friction and wear characteristics of Cu-5 at. percent Sn-P alloys containing 1–5 at. percent P were studied using a pin on disc apparatus. The results showed that the decrease in both the coefficient of friction and the rate of wear became conspicuous with the increase in quantity of Cu3 P coexisting in the matrix; its amount increases with the content of phosphorus. The structural changes in the surface of the specimen due to heating in a vacuum were observed by using Auger electron spectroscopy and X-ray photoelectron spectroscopy. It was seen that the surface concentration of phosphorus strongly increased after heating at 573K, whereas the diffusion of tin atoms was markedly retarded. It was concluded from these results that the behavior of phosphorus atoms in the surface during sliding played an important role in the friction and wear characteristics of Cu-Sn-P alloys.

Commentary by Dr. Valentin Fuster
J. of Lubrication Tech. 1979;101(2):208-211. doi:10.1115/1.3453325.

Cemented WC-Co composites were abraded by quartz abrasives in a three-body test. It was found that the quartz has an effective hardness as an abrasive of 1260–1320 kg/mm2 (12.36–12.94 GPa), which makes it a soft abrasive relative to most cemented carbides. Material is removed in abrasive wear by two mechanisms—cobalt extrusion and carbide fragmentation. The binder extrusion is rate-controlling and occurs due to repeated loading of the surface material in friction-generated shear. The cracking and fragmentation of the carbide grains is a secondary removal mechanism which depends upon the relaxation of compressive stresses in the carbide grains as the cobalt binder is extruded. The wear rate is directly related only to binder mean free path and it increases linearly with this parameter.

Commentary by Dr. Valentin Fuster
J. of Lubrication Tech. 1979;101(2):212-218. doi:10.1115/1.3453326.

A process is described for the preparation of low density polyethylene (LDPE) doped with two percent dysprosium oxide for use in transfer experiments. The doping agent made it possible to use neutron activation analysis to measure transfer of LDPE to steel disks at levels of less than one microgram. A model is described which predicts the transfer of LDPE, PVC and PCTFE to within a factor of five or less to measured values of transfer. The model also predicts the penetration depth of the highest asperity into the polymer at which the material transferred fills up the valleys on the surface. The major significance of the model is that it does not require an experimentally determined wear coefficient to make the prediction of transfer. The model uses the normal load, yield strength of the polymer, the apparent area of contact, the bearing area curve for the surface, the polymer density, and the shear angle of the polymer to make the transfer prediction.

Commentary by Dr. Valentin Fuster
J. of Lubrication Tech. 1979;101(2):220-229. doi:10.1115/1.3453329.

The Average Flow Model introduced in an earlier paper is extended to include sliding contacts by deriving the shear flow factor for various roughness configurations. Similar to the pressure flow factors, the shear flow factor is obtained through numerical flow simulation on a model bearing having numerically generated roughness. The flow factors for isotropic and directional surfaces are expressed as empirical relationships in terms of h/σ, a surface pattern parameter γ defined as the ratio of x and y correlation lengths, and the variance ratio Vr1 which is the ratio of variance of surface 1 to that of the composite roughness. Expressions for the mean shear stress and horizontal force components due to local pressure in rough bearings are derived through the definition of shear stress factors, also obtained through simulation. The application of the average Reynolds equation to analyze roughness effects in bearings is demonstrated on a finite slider. The effects of the operating parameters as well as the roughness parameters on mean hydrodynamic load, mean viscous friction and mean bearing inflow are illustrated.

Commentary by Dr. Valentin Fuster
J. of Lubrication Tech. 1979;101(2):231-237. doi:10.1115/1.3453332.

The influence of geometry on the isothermal hydrodynamic film separating two rigid solids was investigated. Pressure-viscosity effects were not considered. The minimum film thickness is derived for fully flooded conjunctions by using the Reynolds boundary conditions. It was found that the minimum film thickness had the same speed, viscosity, and load dependence as Kapitza’s classical solution. However, the incorporation of Reynolds boundary conditions resulted in an additional geometry effect. Solutions using the parabolic film approximation are compared with those using the exact expression for the film in the analysis. Contour plots are shown that indicate in detail the pressure developed between the solids.

Commentary by Dr. Valentin Fuster

DISCUSSIONS

Commentary by Dr. Valentin Fuster
Commentary by Dr. Valentin Fuster
Commentary by Dr. Valentin Fuster

TECHNICAL BRIEFS

J. of Lubrication Tech. 1979;101(2):240-241. doi:10.1115/1.3453335.
Abstract
Topics: Gas bearings
Commentary by Dr. Valentin Fuster

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