An analysis of track replenishment mechanisms in the starved regime

In earlier work [4-6] the film thickness reduction due to lubricant starvation was analysed for a circular EHL contact. One conclusion from this work is that without a mechanism to replenish the track with lubricant the process of film thickness reduction would inevitably lead to component failure. Thus in order to explain long term operation, it is essential to include a replenishment mechanism. This paper analyses the replenishment under severely starved conditions. Replenishment is divided into 'out-of-contact' and 'in-contact' reflow. The 'out-of-contact' reflow occurs in the lubricant track in the time between overrollings. Under severely starved conditions it was found that this mechanism produced negligible reflow into the track. The second reflow mechanism considers flow in the vicinity of the contact due to local capillary forces. In a first approximation the flow around a stationary contact was analysed, and a comparison with experimental observations shows similar flow patterns and similar time scales; An extension of this model to a moving contact was made resulting in a theoretical film thickness versus speed curve.