A thermal analysis of traction in elastohydrodynamic rolling/sliding line contacts

Abstract

An accurate thermal analysis of traction in elastohydrodynamically lubricated (EHL) line contacts has been done using an efficient numerical method based on Lobatto quadrature developed by Elrod and Brewe [H.G. Elrod, D.E. Brewe, Thermohydrodynamic analysis for laminar lubricating films, NASA Tech. Memorandum No. 88845, 1986.]. Roelands' viscosity model for P-150 and Santotrac-50 oils has been used in the present analysis. The variation of traction coefficient with slip for maximum contact pressures and rolling speeds varying between 0.4 to 1.52 GPa and 5 to 35 m s-1, respectively, are presented. Significant reduction in traction coefficient at high rolling speeds due to thermal effects have been found. Large increments in traction coefficient have been determined at high contact pressures, e.g., at 1.52 GPa as compared to 0.4 GPa at a particular rolling speed. The results of the present work have been compared with the results of Crook [A. W. Crook, The lubrication of rollers: IV. Measurements of friction and effective viscosity, Philos. Trans. R. Soc. London, Ser. A, 255 (Jan. 1963) 281-312.], Cheng [H.S. Cheng, A refined solution to the thermal elastohydrodynamic lubrication of rolling and sliding cylinders, Trans. ASLE, 8 (4) (1965) 397-411.] and Walowit and Smith [J.A. Walowit, R.L. Smith, Traction characteristics of a MIL-L-7808 oil, Trans. ASME, J. Lubric. Technol., Oct. 1976, pp. 607-612.]. It was found that the results obtained by the present method are consistent with more elaborate theories and with the available traction data. Significant reduction in traction coefficient has been noticed at high rolling speeds (above 15 m s-1) and high slips (above 10%). The thermal effect on the sliding traction coefficient, μs, is expressed in terms of the dimensionless thermal loading parameter, Q, dimensionless load W and slip 5 as: μ = 2.31 W0.80Q-0.66S-0.72. © 1998 Elsevier Science S.A. All rights reserved.