EHL Contact Temperature - Comparison of Theoretical and Experimental Determination

Highly loaded rolling and sliding elastohydrodynamically lubricated (EHL) contacts e.g. at gears are subject to shear and compressive heating of the lubricant film in the contact. Mainly by conduction and convection, the heat is distributed in the lubricant film and solid bodies resulting in an EHL contact temperature distribution. As viscosity, density, Theological behavior and oxidation stability of lubricants as well as tribofilm formation depend significantly on EHL contact temperature, its accurate prediction is crucial for the design of machine elements. However, theoretically calculated and measured EHL contact temperatures often show considerable discrepancies. Hence, this paper discusses the influence of different thin film sensor designs as well as the impact of different coatings for electrical insulation on the measured EHL contact temperature. Simulated results are obtained from a thermal EHL contact model considering non-Newtonian fluid behavior. Measured results are from the FZG twin disc test rig using thin film sensors.