Statistical analysis of wear of biplanar deterministically-arrayed surfaces for load bearing applications

The use of microscale deterministic surface features has been investigated in many bearing and seal applications in recent research. This paper considers a class of surface textures that are comprised of periodic arrays of deterministic geometric shapes created using photolithography-based manufacturing processes. These features are unique in that they can be modeled as biplanar: the topography of the entire surface ideally lies on one of two parallel horizontal planes. A total of eight such surface textures are analyzed: three comprised of electroplated nickel cavities and five comprised of metal-impregnated polymer asperities. It is shown that for this class of surface textures, closed form solutions for perfectly-manufactured surfaces exist for eleven areal surface parameters-including amplitude (Sa, Sq, St and Sz), spatial (Ssk, Sku and Std) and functional (Sbi, Sci and Svi)-and these are derived and presented for each case. These surface parameters are then used to evaluate manufacturing process errors for the surface textures and to quantify and evaluate the impact of wear on the performance of such surface textures when placed in a tribological application, in this case a radial lip seal. In particular it was found that useful correlations exist between the surface parameters of Sq and Svi and the operating torque in the lip seal application.