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This paper describes the development of a thin film rheometer able to measure the viscosity of lubricant films of the order of 200 μm thickness on flat, solid surfaces. The rheometer consists of a small cylinder mounted on a piezo bimorph which is divided electrically into two halves. When an AC voltage is applied to the one half of the piezo it causes the flat surface of the cylinder to oscillate in its own plane with an amplitude of a few microns. This motion produces an AC output from the other half of the piezo. The flat face of the cylinder is held parallel to an oily test surface and the latter is supported on a micrometer stage so that the gap between the two surfaces can be adjusted. As the gap is narrowed the oil film dampens the sinusoidal motion of the cylinder and the extent of this damping can be used to determine the viscosity of the oil film between the surfaces.

A study has been made of the lubricant film-forming properties of viscosity index improver-containing oils in non-steady state, high-pressure contacts. Two types of non-steady speed condition have been investigated, sudden halting of motion and cyclically-varying entrainment speed. Film thickness has been measured in a ball on flat contact using ultra-thin film interferometry. It has been shown that viscosity index improver polymers in solution exhibit an enhanced squeeze behavior during halting and a viscoelastic response to acceleration/deceleration.

Lubricating films were deposited on friction test specimens from a homogeneous gas phase mixture of nitrogen and various lubricant vapors. The lubricants used were tributylphosphate ester (TBP), tricresylphosphate ester (TCP), trimethylolpropane-triheptanoate ester (TMPTH) and mix-bis-(m-phenoxyphenoxy)benzene (PPE). The volume percent of lubricant vapor in nitrogen ranged from 0.5 to 3.0 percent. The friction tests were performed over a temperature range of 245 to 586°C. The lubrication properties of vapor deposited films were found to be controlled by the specimen temperature, vapor exposure time, lubricant vapor concentration and lubricant chemistry. Lubrication of the tribocontact can be optimized by using the deposition parameters to give the optimum film thickness for a given lubricant.