A. Cameron

Optical analysis of ball bearing starvation

Optical measurement of oil film thickness in elastohydrodynamic rolling point contact of ball bearing

The Viscosity Wedge

In a previous paper (6) it was shown that a viscosity gradient across an oil film allowed a hydrodynamic load to be carried between contra rotating discs. If there is a temperature (and viscosity) gradient, not only through the oil film but also in the direction of motion, a considerable load can be borne. The equations are set up and solved numerically giving coefficient for oil film thickness and friction. The oil film thickness is comparable (three quarters) of that carried by Michell pads. The computed results are applied to the parallel surface thrust bearing described by Fogg (2) in 1946 and shown to give tolerable agreement with the experimental findings. Contributed to the American Society of Lubrication Engineers by the author.

Film Thickness of Grease in Rolling Contacts

Optical Interferometry is used to study the film thickness of greases, and of soap suspensions and of their base oils in point or line contact. In one case, samples were taken from a grease-lubricated plain-bearing test after 5 1/2- and 25-million revolutions. The effective viscosity of a grease under the very high shear rates of the order of 1/2 × 10-6 s-1 encountered in rolling contacts can be calculated. Presented as an American Society of Lubrication Engineers paper at the ASME/ASLE Lubrication Conference in San Francisco, California, August 18–21, 1980.

A Study of Friction Polymer Formation

Surfactant solutions in hexadecane have been studied to assess their capabilities in forming friction polymer. Only alcohols form adherent films, resistant to simple washing, on rubbing surfaces. There is no evidence of polymer formation on rubbed surfaces, even with mixtures of diacids and diols.

Basic Studies on Boundary, EP, and Piston-Ring Lubrication Using a Special Apparatus

A reciprocating short-stroke friction apparatus with several novel features is described. Friction can be measured reproducibly up to 350°C with easily obtainable test pieces. The change from boundary to hydrodynamic lubrication occurred at a constant value of the product (frequency×viscosity×stroke length), so high shear rate surface viscosities could be determined. When fatty acids in cetane lubricated steel, thick viscous films were formed whose viscosities were measured over a range of temperatures. Tests showed the action of EP-lubricants, typified by dibenzyl disulfide (dbds), could be explained by adsorption of polar materials on the dbds modified surface. A polar material was needed in the lubricant for the dbds to act. Finally, the action of zinc dialkyl dithiophosphate (ZnDTP) in mineral oil on honed cast-iron diesel liners up to 250°C was investigated. ZnDTP formed a thick viscous film which became solid between 90°and 200°C and caused cracking when run at 250°C for one hour. Presented at the 3...

Parallel Surface Thrust Bearing

The theory for the thermal wedge thrust pad is given assuming (a) all the heat is taken away by the oil and (b) the viscosity is constant across the thickness of the film. The viscosity is allowed to vary in the direction of motion. Solutions are obtained by both analytical and relaxation methods for infinite and finite pads. The viscosity is allowed to vary in the direction of motion and also a constant value is taken. The results are displayed non-dimensionally graphically. Contributed to the American Society of Lubrication Engineers by the Author. 1 This paper was read at the VIth International Congress of Applied Mechanics in Paris, in September, 1946, but due to post-war difficulties the Proceedings were not published. It is given here in its original form with later additions appended as Footnotes.

Fatigue Scoring A New Form of Lubricant Failure

Using the recently developed hydrostatic disc machine, a new form of gear lubricant failure has been investigated. This is called fatigue scoring and is caused by microcracks and micropits forming in the surface of heavily loaded surfaces, which drain away the oil in the contact. It is shown that failure is viscosity sensitive: the lower the viscosity, the lower the resistance to scoring. The correct choice of EP additive can raise the scoring load considerably, providing the additive is so chosen that it is active at the running temperature of the gear surface. Presented as an American Society of Lubrication Engineers paper at the ASME/ASLE International Lubrication Conference held in New York City, October 9–12, 1972

A Theory of Boundary Lubrication

The mechanism of boundary friction is assumed here to be due to the molecular forces between hydrocarbon molecules adsorbed on the surfaces rather than to welding and tearing of the opposing surface roughness. On this assumption the frictional force, which arises when two orientated layers are moved over each other, can be calculated. The formulae for the Van der Waals and the repulsion forces are those successfully used by Muller for paraffins. The different values of the kinetic and static frictions can be explained by the forces being due to the tails of the chains in kinetic and the sides of the chains in static lubrication. The value of the coefficient of friction, as calculated by this method, is of the correct order of magnitude. Contributed by the ASLE Technical Committee on Lubrication Fundamentals and presented at the Annual Meeting of the American Society of Lubrication Engineers held in Buffalo April, 1959.

Wear Properties of Salt-Bath Carbonitrided Steels

The paper describes tests to determine whether two methods of surface hardening, sulfinuz and tufftride, improved the lubricated wear properties of a crank-shaft steel. Very pure hexadecane was used as lubricant in a modified ball and triplane test machine. The surprising result was that wear rate increased logarithmically with actual contact temperature up to 160°C when it dropped two orders of magnitude. Below 160°C, the wear debris was red ferric oxide Fe203,· beyond 160°C it changed to the much softer magnetite Fe304. Approximate figures for the energy of the two (mild) wear processes were obtained, 12–15k cal/g mole for Fe203 and ˜25k cal/g mole for Fe304. No explanation for the 160°C transition, which was independent of speed and contact pressure, could be found. All the observed wear rates were explicable in terms of surface hardness. Presented as an American Society of Lubrication Engineers paper at the ASME/ASLE Lubrication Conference in San Francisco, California, August 18–21, 1980.