ABSTRACT
This chapter discusses marginal lubrication, defined by the absence of thick fluid films. The industrial revolution, which by the way, could proceed no faster than developments in lubrication, began before polymers were invented and before temperatures and chemical environments were severe enough to require the high cost of high-quality ceramic materials. Adequacy of lubrication was measured in terms of friction, and tests were done "by sliding surfaces over one another at extremely low speeds and very high contact pressures so that the incidence of hydrodynamic or elastohydrodynamic lubrication is reduced to a minimum. Different modes of wear and surface damage occur during marginal lubrication. Boundary lubricants are usually thought to be applied to or inserted between sliding pairs, producing nonsolid boundary films. Further, the chemical composition of the films from these tests was determined, and the mechanical durability of the boundary films was measured.
