SAE ARP6243

The lubricant performance capability for aero-propulsion drive systems is derived from the physical properties, chemical properties, and the transport phenomena of the oil. Viscosity, pressure-viscosity coefficient, and elastohydrodynamic (EHD) full-film traction coefficient are inherent properties of the lubricating fluid. Full-film traction coefficient is a required input for thermal performance prediction and engineering design. Traction coefficient data can be modeled and used as an input into bearing and gear analysis codes. This document describes a test method for traction coefficient measurement of 5 cSt oils under service-like conditions for high-stress Hertzian elastic contacting bodies operating under temperatures and sliding (slip) velocities found in high-speed rolling element bearings and gears. Bearings and gears in high-speed aero-propulsion turbine engines and transmissions generate an enormous amount of heat between rolling/sliding contacts. A good portion of the heat is associated with the shear of highly stressed thin films between surfaces. The bulk film shear stress or traction is critically needed to predict heat generation and to conduct thermal management analysis. Traction coefficient measurements are required over engine relevant speeds, stresses, and temperatures.