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AWARDS

J. of Lubrication Tech. 1978;100(3):309-310. doi:10.1115/1.3453177.
FREE TO VIEW
Abstract
Commentary by Dr. Valentin Fuster

PROFILES

J. of Lubrication Tech. 1978;100(3):311-315. doi:10.1115/1.3453178.
FREE TO VIEW
Abstract
Topics: Tribology
Commentary by Dr. Valentin Fuster

RESEARCH PAPERS

J. of Lubrication Tech. 1978;100(3):316-322. doi:10.1115/1.3453179.

An analytic solution is presented for squeeze film flow with smooth, arbitrary, two-dimensional surface geometry. One surface undergoes sinusoidal oscillation toward the other. The oscillation amplitude is much smaller than the film thickness, which is in turn much smaller than the bearing length. The solution improves on the lubrication theory due to the inclusion of inertia effects. The solution to an illustrative problem is presented—the thrust bearing. The velocity field, pressure distribution and load differ significantly from those predicted by lubrication theory. The results show the lubrication solution for load and pressure to be in error by over 100 percent for Reynolds numbers as low as 5.

Commentary by Dr. Valentin Fuster
J. of Lubrication Tech. 1978;100(3):323-329. doi:10.1115/1.3453180.

Squeeze film flow in smooth but arbitrarily shaped infinite journal bearings is considered. The nonrotating shaft is subject to small sinusoidal oscillations. An analytic solution is presented which improves on the lubrication theory by including inertia terms in the equations of motion. The solution technique is to introduce a stream function by which the problem can be reduced to a linear partial differential equation, with time varying boundary conditions, which can be solved by conventional means. The solution to an illustrative problem is presented—the circular journal and bearing. The velocity field and pressure distribution differ qualitatively from those predicted by lubrication theory due to the existence of out-of-phase components. The results show that the lubrication solution for the amplitude of load and pressure can be significantly in error for high Reynolds number operation of a bearing at low eccentricity ratio. At high eccentricity ratios, however, the lubrication theory can be used with confidence, even at very extreme (high Reynolds number) conditions. Simple approximate closed form expressions for pressure and load are presented which are sufficiently accurate for engineering use (error <3 percent) in the range of practical applications.

Commentary by Dr. Valentin Fuster
J. of Lubrication Tech. 1978;100(3):330-338. doi:10.1115/1.3453181.

Presented is a new numerical procedure for the calculation of flow in finite-width bearing films. The method, based on the integro-differential approach, is a development of schemes devised by Patankar and Spalding [8] and Gosman and Pun [9] for general flows occurring in fields other than tribology. Principal features of the method are: the full inclusion of inertial effects; the retention of “primitive” variables; the use of a marching solution procedure using line-by-line solution of the discretized conservation equations. Applications to several aspects of laminar inertial flow problems are discussed.

Commentary by Dr. Valentin Fuster
J. of Lubrication Tech. 1978;100(3):339-345. doi:10.1115/1.3453182.

A new set of turbulent resistance laws for hydrodynamic lubricant films has been derived with the aid of a turbulence model which includes transport effects on two turbulence parameters. The model consists of two differential equations for the turbulence energy and its rate of dissipation and a constitutive equation for the turbulent viscosity. The model places no restrictions on the Reynolds number. An efficient finite-difference scheme, based on the integro-differential approach and incorporating the resistance laws and a set of accurate inertial coefficients, is applied to the solution of the turbulent inertial flow in finite-width slider bearings. A selection of predictions is presented for non-inertial and inertial flows. The former are compared with solutions obtained with alternative turbulent lubrication theories. The importance of including fluid inertia effects is demonstrated.

Commentary by Dr. Valentin Fuster
J. of Lubrication Tech. 1978;100(3):346-352. doi:10.1115/1.3453183.

A theoretical analysis of both fully flooded rolling traction and film thickness in an EHL line contact is described and modified formulas for fully flooded isothermal conditions are presented. These are compared with the Grubin, Dowson, and Higginson film thickness formulas, and the rolling traction theory by Archard and Baglin (1975). The effect of viscous shear heating in the inlet region has been investigated and new equations for both fully flooded film thickness and rolling traction, including this thermal effect, are introduced. These equations predict significant reductions in both film thickness and rolling traction, relative to the isothermal case, as speed is increased. Viscous shear heating effect is found to be negligible only at very low rolling speeds. The results of the theoretical analysis compare well with experimental data presented by Dyson, Naylor, and Wilson (1966) and Adams and Hirst (1973).

Commentary by Dr. Valentin Fuster
J. of Lubrication Tech. 1978;100(3):353-358. doi:10.1115/1.3453184.

A theoretical analysis of both fully flooded rolling traction and film thickness in an EHL line contact has been presented in Part I of this paper. The effect of viscous shear heating was investigated and the results predict a significant reduction in both fully flooded film thickness and rolling traction, relative to the isothermal case, as speed is increased. In this part of the Series, the analysis is extended to consider the calculation of starved rolling traction and film thickness, including viscous shear heating of the lubricant in the inlet region. An approximate equation has been developed, which predicts both the isothermal and non isothermal starved film thickness for all conditions of inlet boundary distance, rolling speed, load, geometry, material constants and lubricant properties. The results show that both rolling traction and film thickness are significantly reduced from the starved isothermal case. For the starved isothermal case, the theoretical analysis for the film thickness agrees closely with experimental data and published empirical formula by Wymer and Cameron, (1974) and the theoretical work of Wolveridge, et al. (1971).

Commentary by Dr. Valentin Fuster
J. of Lubrication Tech. 1978;100(3):359-363. doi:10.1115/1.3453185.

A theoretical estimate of dynamic characteristics in terms of stiffness and damping of an externally pressurized gas-lubricated porous journal under tilting mode of vibration is made. The governing nonlinear partial differential equations in the porous medium and in the bearing clearance are linearized using a first-order perturbation analysis. The tilt stiffness and damping are then determined from the solution of the resulting linear partial differential equations numerically. The effect of feeding parameter, supply pressure, porosity parameter, L/D ratio and eccentricity ratio on these two above characteristics is shown.

Commentary by Dr. Valentin Fuster
J. of Lubrication Tech. 1978;100(3):364-368. doi:10.1115/1.3453186.

Externally-pressurized gas bearings are prone to a dynamic instability known as pneumatic hammer. This paper examines the possibility of using a flexible damped bearing support to suppress the instability. A circular thrust bearing having a central feed hole and pocket is employed in the feasibility study. The linearized gas film dynamic coefficients are derived using an adaptation of an existing solution to Reynolds equation for a long rectangular bearing. Only stability of the equilibrium position is considered. Results obtained for a support having a stiffness comparable to the stiffness of the gas film show that damping in the support can substantially improve stability.

Commentary by Dr. Valentin Fuster
J. of Lubrication Tech. 1978;100(3):369-377. doi:10.1115/1.3453187.

The squeeze-film damper, undergoing a whirl orbit as may be caused by rotor unbalance, resists eccentricity of the whirl orbit with a static stiffness which is proportional to the dynamic force carried by the squeeze-film. In addition, the fluid film force would develop nonsynchronous components. The short bearing analysis is applied to treat this problem. Implications regarding the unbalance dynamics of a rigid rotor in the presence of a static load are examined.

Commentary by Dr. Valentin Fuster
J. of Lubrication Tech. 1978;100(3):379-383. doi:10.1115/1.3453190.

A flat seal having an angular misalignment is analyzed, taking into account the radial variations in seal clearance. An analytical solution for axial force, tilting moment, and leakage is presented that covers the whole range from zero to full angular misalignment (surfaces in contact). It is shown that nonaxisymmetric hydrostatic pressures due to the radial variations in the film thickness have a considerable effect on seal stability. When the high pressure is on the outer periphery of the seal, both the axial force and the tilting moment are nonrestoring. This causes the seal surfaces to wear at the outer diameter. Instability and wear at the inner diameter can occur when angular misalignment is combined with radial distortions and the high pressure is on the inner periphery. The case of high-pressure seals, where cavitation is eliminated, is discussed, and the possibility of dynamic instability is pointed out.

Commentary by Dr. Valentin Fuster
J. of Lubrication Tech. 1978;100(3):386-393. doi:10.1115/1.3453193.

A testing scheme is described for short-term evaluation of lubricant-breakdown rate in starved elastrohydrodynamic (EHD) rolling contacts. It is shown that the rate is strongly influenced by the amount of lubricant available to the contacts, and by certain chemical treatments of the surfaces. Several surface conditions are evaluated for their effect on degradation rate.

Commentary by Dr. Valentin Fuster
J. of Lubrication Tech. 1978;100(3):395-403. doi:10.1115/1.3453196.

An analytical model describing the in-plane motions of a bearing cage is developed for angular contact bearings operating in the EHD lubrication regime. The ball-cage impacts are treated as impulse forces imparted to the cage. The model is developed on the basis that during ball-cage impact, energy is transmitted to the cage at the ball-cage interface by friction, whereas, cage energy is dissipated at the ball-race interfaces as a result of the ball being caused to translate along its EHD film by the cage. Numerical computations using the model indicate that the level of ball-cage friction, lubricant viscosity, and extent of ball-race lubrication are significant factors in determining the conditions for which the cage motions may be stable or unstable. The predicted trends concerning the stability of the cage motions conform qualitatively to observed experimental results.

Commentary by Dr. Valentin Fuster
J. of Lubrication Tech. 1978;100(3):404-416. doi:10.1115/1.3453197.

A preliminary investigation into the possible role of glass transition and glassy state behavior of lubricants in EHD contacts is reported. Measurements of the glass transition of lubricants as a function of pressure by two methods are presented along with a discussion indicating possible implications of the results to EHD lubrication.

Commentary by Dr. Valentin Fuster
J. of Lubrication Tech. 1978;100(3):418-422. doi:10.1115/1.3453201.

The sound velocity of four lubricants has been measured as a function of temperature and pressure using Brillouin scattering. A change in slope of the velocity as a function of temperature or pressure allowed the determination of the glass transition temperature and pressure. The glass transition data were used to construct a phase diagram for each lubricant. The data indicate that Tg increased with pressure at a rate which ranged from 120 to 200 C/GPa. The maximum pressure attained was 0.69 GPa and the temperature range was from 25 to 100 C.

Commentary by Dr. Valentin Fuster
J. of Lubrication Tech. 1978;100(3):423-427. doi:10.1115/1.3453202.

In extrusion and injection molding, centrifugally cast metallurgical coatings are often utilized to provide wear resistance in the barrel of the molding machine. The need for wear resistance is a result of two potential sources of wear, a screw or plunger that operates within the barrel, and the plastic being processed. Adhesive wear occurs under abnormal operating conditions when the screw bears against the barrel bore. Abrasive wear may result from certain additives used to modify the properties of the plastics. An in situ centrifugal casting process used for production of wear resistant coatings metallurgically bonded to the bores of heavy wall metal tubes is described. Characteristics of industry standard metallurgical coating alloys, a martensitic white iron, a Co-Ni-Cr-B alloy and a composite with tungsten carbide dispersed in a Ni-base alloy matrix are given. Metal-to-metal wear-compatibility tests are discussed.

Commentary by Dr. Valentin Fuster
J. of Lubrication Tech. 1978;100(3):428-435. doi:10.1115/1.3453203.

Alloy characteristics that relate directly to wear resistance are much sought after, but elusive. Attempts have been made to correlate wear resistance with mechanical and physical properties, including hardness, but only with limited success. During the course of this investigation, cast, wrought, and hard facing wear alloys were processed using various casting, consolidation and deposition techniques and evaluated using laboratory sand abrasion wear tests, and metal-to-metal (adhesive) wear tests. In general, superior abrasive wear resistance was obtained with those processing conditions that produced microstructures which contained coarse carbide morphologies. No general relationship between hardness and abrasive or adhesive wear was found in this processing study. Little effect of processing, structure or hardness was observed on metal-to-metal wear. Where chemical similarity and common structural condition between the commercial alloys tested allows comment on chemical effects, carbon appeared to be the most effective variable; particularly with abrasive wear where resistance increased with increasing carbon level and volume percent of carbide phases present.

Commentary by Dr. Valentin Fuster
J. of Lubrication Tech. 1978;100(3):436-441. doi:10.1115/1.3453204.

The observation of a white diffusion layer at the HSS tool-BUE (mild steel) interface and in the crater, its composition and its identity are discussed here. Diffusion wear by itself is not a dominant mode of wear but depletion of elements from the tool surface makes it more prone to wear by plastic deformation to a larger extent and by abrasion to a lesser extent. Plastic deformation in coated carbide tools and Loladze’s diffusion wear model for carbide tools are used to project a diffusion wear model for HSS tools at low to medium and at high speeds.

Commentary by Dr. Valentin Fuster

DISCUSSIONS

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

TECHNICAL BRIEFS

J. of Lubrication Tech. 1978;100(3):442-444. doi:10.1115/1.3453205.

A closed form solution of pressure distribution which leads to the determination of bearing performance characteristics of an externally pressurized porous gas bearing without journal rotation is obtained. A good agreement with a similar available solution confirms the validity of the method.

Commentary by Dr. Valentin Fuster
J. of Lubrication Tech. 1978;100(3):444-446. doi:10.1115/1.3453206.
Abstract
Topics: Reynolds number
Commentary by Dr. Valentin Fuster

BOOK REVIEWS

Commentary by Dr. Valentin Fuster

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