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

Abstract

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.