This study proposes a model to predict the effect of lubricant starvation on EHL behavior of line contact, including the boundaries among the starved, fully flooded, and over-flooded lubrications. A pre-inlet region is analyzed to overcome the discontinuous phenomenon of film thickness at the position of the meniscus presented in the previous model under the starvation.
The relationship between the film thickness of the supply region and the position of the meniscus is established. The prediction formulas for the minimum film thickness required to achieve the fully flooded condition is expressed in terms of the load and the speed. This formula can be used to predict the fully flooded/starved boundary under certain of flow rate in the supply end.
In the analysis of the pre-inlet region, the surface speed, the pressure and the mass flow rate are assumed to be continuous with the supply region and the pressure region, so that its film thickness can be calculated by the mass flow rate equation. However, when the backflow occurs in the boundary between the pre-inlet and pressure region, only part of the film thickness flows into the pressure region, and the rest film only performs recirculation. When no backflow is observed at this boundary, the film thickness in the pre-inlet region easily rises and continuously connects to the pressure region.
If the film thickness in the supply end is increased, the surface speed gradually decreases at the inlet end of the pre-inlet region. When the film thickness in the supply end increases to twice as high as the minimum film thickness that required to achieve the fully flooded condition, the surface speed at the inlet end of the pre-inlet region becomes stationary. Hence, when the film thickness in the supply end continues to increase to more than twice, the backflow occurs at the supply region, and this behavior is called the over-flooded lubrication.