Lubrication at Extreme Pressures with Mineral Oil Films

Abstract

Intact mineral oil films at average pressures ranging from 86,000 to 215,000 psi and at high rates of shear have been obtained using a bearing consisting of the contact area between crossed axis steel cylinders. Intact films have also been maintained at low rates of shear and lower pressures using a bearing consisting of a sphere in a spherical shell. The lubricating films possess the shearing properties of plastic solids, a fact which is consistent with solidification observations reported in the literature of high pressure viscometry. In the crossed cylinder bearing the high film pressures required for lubrication are induced by hydrodynamic forces. Such forces can be very large as a result of the rapid increase in viscosity incurred by mineral oils under increasing pressure. The observation of complete mineral oil lubrication at such extreme pressures resulting from known bulk properties, namely, viscosity increase and solidification under pressure, suggests that these properties are sufficient to account for practical mineral oil lubrication.