J. of Lubrication Tech. 1975;97(1):1. doi:10.1115/1.3452526.
Commentary by Dr. Valentin Fuster


J. of Lubrication Tech. 1975;97(1):4-12. doi:10.1115/1.3452534.

A model of hydrodynamically lubricated cold rolling including thermal and pressure effects on the lubricant is developed in this paper. The hydrodynamic film thickness is calculated as well as the work zone pressure and shear stress distribution for several conditions assuming that the lubricant behaves as a Newtonian fluid. Pressure measurements made with vapor-deposited thin-film transducers on the roll surface are used for experimental comparison.

Commentary by Dr. Valentin Fuster
J. of Lubrication Tech. 1975;97(1):14-17. doi:10.1115/1.3452524.

A horizontal forging machine, Impacter, was used to determine coefficients of friction under different conditions of forging 1020 steel and 2014 T-4 aluminum. Short cylinders were open die forged with repeated blows and the reduction of height determined for one to eight blows. The area under a calculated forging force versus reduction curve was related to available energy in the impellers so that a theoretical reduction for each blow could be determined for different coefficients of friction.

Commentary by Dr. Valentin Fuster
J. of Lubrication Tech. 1975;97(1):18-23. doi:10.1115/1.3452525.

The Ugine-Séjournet patent for glass lubrication of metals extrusion made it possible to extrude steel in large quantities. A cold pad of glass powder inserted between the die and the billet head melts progressively, providing a high viscosity glass film between the die and the metal. The authors propose a theoretical model of the lubrication mechanism: progressive melting, hydrodynamic flow, and stability of the film. The influence of process parameters is discussed and results are compared with experimental measurements.

Commentary by Dr. Valentin Fuster
J. of Lubrication Tech. 1975;97(1):25-31. doi:10.1115/1.3452528.

Hydrostatic extrusion of annealed 1100 aluminum was investigated experimentally at ambient temperature. The principal variables studied were lubricant viscosity which was varied from less than 100 to over 76,000 SUS at 100 deg F and the diametral clearance between the follower block and the extrusion cylinder which ranged from 0.0005 to 0.0030 in. for the 1.026 in. dia. cylinder. The specimen diameter was 0.97 or 1.00 in. corresponding to an extrusion ratio of 4.75 or 5.00, respectively. The included die angle was either 60 deg or 90 deg. The results show that with a proper combination of the lubricant viscosity and the follower block clearance, hydrostatic extrusion can be accomplished without the necessity of any sealing of the container on the follower block side. The optimum clearance for minimum breakthrough pressure increases as the lubricant viscosity increases. The extrusion force increases with die angle. The paper discusses the various factors that affect the magnitude of the breakthrough pressure and the occasional uneven bamboo-type appearance of the surface. Processing conditions must be selected carefully since the lowest extrusion force does not necessarily lead to a product with the best surface finish.

Commentary by Dr. Valentin Fuster
J. of Lubrication Tech. 1975;97(1):33-36. doi:10.1115/1.3452531.

The present paper discusses some of the friction related problems associated with the upsetting and sheet forming of nickel chromium base superalloys at temperatures between ambient and 1200 F. It continues by reviewing some of the works of the author and his colleagues in examining the effects of certain of the components of potential industrial metalworking lubricants. In the course of the research an interesting synergistic effect pertaining to lubricant components has been uncovered, a difficulty concerning the brinelling of die materials evidenced and an attempt made to utilize some of the interesting potential tool materials, for example carbides and nitrides, that have recently become available. In connection with the latter, preliminary results indicate some promising values of the friction coefficient in 1200 F tests at a 20 percent average deformation upon Inconel 625 and 718 workpieces. However, it is pointed out that in using these tooling materials special precautions must be taken regarding the provision of adequate support by sub-tooling.

Commentary by Dr. Valentin Fuster
J. of Lubrication Tech. 1975;97(1):37-43. doi:10.1115/1.3452532.

Forward slip during the rolling process is adopted as a measure in evaluating rolling stability. Forward slip during cold rolling of aluminum has a serious effect on the productivity as well as the quality of rolled sheets. The forward slip must remain within a specified range depending on the thickness of sheet if the rolling is to stay stable. Rolling speed, rolling tension, rolling oil viscosity, additives, rolling surface roughness, and roll diameter constitute an important factor for controlling forward slip during rolling. The present paper examines the effects of these factors on forward slip using both production-type and experimental rolling mills.

Commentary by Dr. Valentin Fuster
J. of Lubrication Tech. 1975;97(1):44-51. doi:10.1115/1.3452533.

The steady state operational performance of gas-lubricated porous journal bearings is analyzed by using a numerical iterative method. Results are obtained, and presented in charts and tables, for the length-to-diameter ratio values of 1, 2, and 3; the eccentricity ratio values of 0.2, 0.4, 0.6, and 0.8; the compressibility number from 0 to 10; and several values of the feeding parameter and the supply-to-ambient pressure ratio commonly found in applications.

Commentary by Dr. Valentin Fuster
J. of Lubrication Tech. 1975;97(1):52-62. doi:10.1115/1.3452535.

A rectangular gas film bearing with inherently compensated feedholes evenly distributed around the interior is analyzed. The feedhole boundary between the enclosed central region and the exterior perimeter region is modeled as a line source. A periodic load disturbance is imposed on the externally pressurized bearing, and the dynamic pressure distribution is determined by small perturbations of the Reynolds’ equation. The solution for the square bearing is obtained by numerical methods. Design curves are presented for the load capacity, mass flow, stiffness, and damping as a function of squeeze number, external pressure, restrictor coefficient, and source location. A design methodology is presented.

Commentary by Dr. Valentin Fuster
J. of Lubrication Tech. 1975;97(1):63-68. doi:10.1115/1.3452536.

An externally pressurized compliant air bearing with potential for operation on surfaces of moderate unevenness or roughness such as might be encountered in vehicle guideways is considered. Analytical results are presented which show the effect on load carrying capacity, flow requirement, and center of pressure location of variation of bearing compliance, surface roughness, bearing speed, and bearing slope.

Commentary by Dr. Valentin Fuster
J. of Lubrication Tech. 1975;97(1):69-72. doi:10.1115/1.3452537.

Theoretical investigation on the performance characteristics of externally pressurized gas bearings with several supply holes is made. The solution is obtained for finite bearings using pressure perturbation method. The results are compared with an approximate solution assuming quasi-steady film. It has been shown that quasi-steady solution overestimates the squeeze film force.

Commentary by Dr. Valentin Fuster
J. of Lubrication Tech. 1975;97(1):73-80. doi:10.1115/1.3452538.

This paper summarizes a theoretical study of a method of controlling the clearances of hydrodynamic foil bearings. The air-bearing clearance for certain large-wrap cylindrical foil bearings (that is, for perfectly flexible webs) is determined exclusively by the tension, the viscosity of air, the velocity of the web, and the radius of the cylinder. This clearance cannot usually be modified without changing one of the above parameters. However, a pressure pad placed above the web where the web enters the air bearing enables this uniform clearance to be reduced considerably. The pressure pad can thus be used to control the position of the web relative to the cylinder. This paper presents the relationships of the pressures and size of the pad to the reduction in uniform clearance. Clearance profiles for many different pads are also presented, and the practical limitations on reductions in clearance are discussed.

Commentary by Dr. Valentin Fuster
J. of Lubrication Tech. 1975;97(1):81-88. doi:10.1115/1.3452539.

The drift torque produced in a spherical ball bearing supporting a directional gyro is obtained. The analysis is based on static load balance and Coulomb friction. The effects of preload and wear track on drift torque are also studied. It is found that the drift rate of the gyro due to this drift torque is significant.

Commentary by Dr. Valentin Fuster
J. of Lubrication Tech. 1975;97(1):89-93. doi:10.1115/1.3452540.

The Reynolds equation is here solved for journal bearings using new upstream boundary conditions which reflect the fact that starting films in these bearings are often incomplete. The work is an extension of previously published results for short bearings to the case of finite bearings of arbitrary width and arbitrary extent of inlet film. An expression is also derived relating the width of the inlet film with the lubricant feed pressure and the bearing operating parameters, when the lubricant is fed through a hole. The results provide an explanation for the profound lack of agreement between previous theory and experiment with regard to side leakage in journal bearings.

Commentary by Dr. Valentin Fuster
J. of Lubrication Tech. 1975;97(1):94-100. doi:10.1115/1.3452541.

In this approximate analysis of laminar journal bearing operations both the momentum and the energy equations are two dimensional, the shaft operates at a constant temperature and the bearing conducts heat in the radial direction only. Via the last of these assumptions, the equation of heat conduction is eliminated from consideration. The remaining equations are solved by a numerical iteration method. A parametric study of therohydrodynamic journal bearing operations is performed and design charts are given for a 100 deg arc bearing.

Commentary by Dr. Valentin Fuster
J. of Lubrication Tech. 1975;97(1):101-104. doi:10.1115/1.3452513.

The problem is the motion of a film of liquid squeezed between a fixed and a uniformly moving plane. The case when the squeeze Reynolds number R is small is reconsidered in order to point out defects in the conventional lubrication theory which may have practical importance. The effects of initial conditions and large R are then examined.

Commentary by Dr. Valentin Fuster
J. of Lubrication Tech. 1975;97(1):105-115. doi:10.1115/1.3452514.

Assuming the short bearing approximation and constant lubricant properties, the root loci of the pertinent characteristic function were obtained for the linearized model of a simple symmetric flexible rotor bearing system. Using these loci, design maps consisting of lines of constant damping and vibration frequency pertaining to the dominant roots are presented as a function of the equilibrium eccentricity ratio and a frequency parameter for relevant degrees of flexibility. These maps display undesirable operating regions where external disturbances such as shock or unbalance loading are likely to excite undesirable vibrations, as well as regions of instability. The maps may conveniently be used to determine the effect of changing journal speed, lubricant viscosity and/or bearing clearance. Increased flexibility is seen to reduce the stability threshold in a predictable manner and to reduce damping at the pin-pin critical speed. The approach is applicable to more complex rotor bearing systems. It is felt that the use of such maps will enhance the understanding of rotor bearing system behavior, particularly at operating regions close to the stability threshold.

Commentary by Dr. Valentin Fuster
J. of Lubrication Tech. 1975;97(1):116-120. doi:10.1115/1.3452515.

This paper describes two new applications for the hydrostatic thrust bearing. The first application is the use of the bearing, when the gap is fixed, as a linear constant resistance. Several bearings have been connected together in parallel to obtain large flow rates at small pressure drops for use as a flowmeter. The second application is the use of a bearing, when modified, as a temperature sensor. Description and performance of this modified design when used as a temperature sensor are given.

Commentary by Dr. Valentin Fuster
J. of Lubrication Tech. 1975;97(1):121-129. doi:10.1115/1.3452516.

The influence of inertia terms and the effects of convection and dissipation on the characteristics of an infinitely wide cooled slider bearing are examined. The lubricant is assumed to be incompressible and the variation of viscosity with temperature is taken into account. The nondimensionalized governing equations, transformed in terms of the stream function, are solved numerically. The results verify that inclusion of the inertia terms causes an increase in the dimensionless load capacity of the bearing. Retention of the convective terms in the energy equation results in a larger dimensionless load capacity. The dissipation terms when included yield a smaller dimensionless capacity.

Commentary by Dr. Valentin Fuster
J. of Lubrication Tech. 1975;97(1):130-133. doi:10.1115/1.3452518.

An analysis of the effect of axial current induced pinch on the squeeze-film behavior between two annular disks, when the upper disk which has a porous facing and is parallel to the stationary nonporous disk moves normal to itself approaching the lower disk, is presented. The analytical results for the pressure distribution, load-carrying capacity, and the film thickness as a function of time are obtained and the effect of pinch on these quantities is studied. It is found that a load proportional to the square of the axial current can be sustained even when there is no flow.

Commentary by Dr. Valentin Fuster
J. of Lubrication Tech. 1975;97(1):134-141. doi:10.1115/1.3452519.

The fine surface defect structure of commercial EC grade aluminum magnet wire has been characterized and four basic component types have been identified. A grading system has been established for each of the component defects. Intermediate process surface characterization studies and laboratory drawing experiments have been performed to clarify the origin of the defects. The potential role of drawing lubrication in repairing or compounding the defect structure has been demonstrated and the mechanics of a drawing related repair process have been clarified through study of the effects of rod drawing on hardness indentations.

Commentary by Dr. Valentin Fuster



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