The Influence of Sliding Speed and Lubricant Shear Stress on EHD Contact Temperatures

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Abstract
Infrared emission microscopy has been used to measure temperature profiles of the surface of a steel ball in sliding EHD contacts lubricated by a range of perfluoropolyethers of different viscosities and thence molecular weights. It has been found that, at high sliding speeds, the highest viscosity fluids give the lowest surface temperatures. Temperature profiles have been employed to determine the shear stresses of perfluoropolyethers in EHD and it has been shown that both the shear stress and variation of shear stress with temperature in EHD contacts are only marginally dependent upon molecular weight. A new model of the influence of speed on surface temperature in EHD contacts has then been developed which explains the influence of lubricant viscosity on surface contact temperature in terms of the thickness and the low thermal conductivity of the lubricant film.