A Method for Studying the Effect of Extreme Pressure Additives on Rubbing Metal Surfaces

When a film of lubricant separates two moving metal surfaces, it may be subjected to radical changes in temperature as the severity of the forces changes. This paper is concerned with a technique which measures the temperature of the lubricant after it leaves the area of rubbing metal surfaces. Special attention was given to: (A) the changing load conditions, (B) the changes in frictional force, (C) the effect of phosphate coating of the metal surface, and (D) the effect of different lubricant compositions. A modification of the Shell Four-ball EP Lubricant Tester has been made which permits automatic recording of a temperature-load curve which registers the temperature and frictional forces with either constant or changing load.

The work has shown that as the load increases at a uniform rate, there may be drastic and sudden changes in lubricant temperature which depend on lubricant composition as well as on metal surface composition.