A Volumetric Fractional Coverage Model to the Predict Frictional Behavior for In Situ Solid Transfer Film Lubrication

Pellets were formed by compacting MoS₂ powder. In the setup, the pellet is sheared against a disk surface while the slider pad rides on the MoS₂ partially-covered asperities, while depleting the lubricant. A volumetric fractional coverage (VFC) modeling approach was developed to predict the friction coefficients for the lubricated pellet/disk sliding contact by assuming that the friction coefficients at pellet/disk and slider/disk interfaces are functions of the fraction of lubricant occupying the control volume. This fractional coverage is a theoretical parameter for quantifying the amount of third body film covering the disk asperities as a function of time. The model can be applied to a deterministic surface, thus, the proposed theory can predict the behavior of friction coefficients between the pellet/disk and slider/disk interfaces for most topographies, whether they are deterministic (i.e., textured) or real (i.e., random).