This paper presents experimental results of measuring the friction coefficient of smooth non-conformal surfaces (ball-on-disk test) in the range of elastohydrodynamic lubrication. The coefficient of friction under starved lubrication was observed under relative sliding motion by using a Tribometer and torque sensor. On the other hand, interferometric images were captured by a digital camera simultaneously with measuring the friction between the ball and disk to illustrate the influence of the air-oil meniscus position on the behavior of friction under the starved lubrication. The results show that the friction of starved contacts depends strongly on the distance of the air-oil meniscus from the Hertzian contact. However, the position of air-oil meniscus is basically related to the entraining velocity, the value of slide-to-roll ratio and the oil amount on the track.
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