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Numerical characterization of surfaces with deep dimples, e.g. Laser Textured Surfaces, poses questions relative to the standard filtering techniques used to separate roughness, waviness and form effects. Usual roughness filters would produce a reference plane several micrometers “below” the surface. If this surface plane will be used as reference for mixed lubrication modeling, no hydro dynamic pressures and excessive high contact pressures may be calculated. The conventional roughness filters, Gaussian and Rk, and 4 other filters were applied in an artificially dimpled surface in order to demonstrate and especially to discuss how the Greenwood contact parameters were affected. Depending on the filter used, the estimation of the minimum surface separation for asperity contact varied two magnitude orders.

In lubricating and specialty oil industries, blending is routinely used to convert a finite number of distillation cuts produced by a refinery into a large number of final products matching given specifications regarding viscosity, flash point, pour point or other properties of interest. To find the right component ratio for a blend, empirical or semi-empirical equations linking blend characteristics to those of the individual components are used. Mathematically, the problem of finding the right blend composition boils down to solving a system of equations, often non-linear ones, linking the desired properties of the blend with the properties and percentage of the blend components. This approach can easily be extended to crankcase lubricants, in which case major blend constituents are base oils, additive packages, and viscosity index improvers. Artificial intelligence (AI) tools allow accurate predictions of the basic physicochemical properties of such blends.

Increased engine loads, coupled with low friction rings, renew the attention for predicting the maximum bore deformation which a given ring design can conform to before losing contact. The MIT developed “Software of Ring Design Tools” (RDT) code was used to verify the different published ring conformability criteria by progressively increasing the bore deformation until the model predicted lack of contact. For simple order deformations, the semi-empirical Tomanik criterion was found to correlate with the model predictions. However, as expected, more realistic deformations combining different harmonic orders were able to cause lack of conformability, even with the individual order amplitudes being lower than the criterion limit. In search of a more comprehensive criterion, an automated model ran hundreds of thousands of deformation cases in combination with relative ring angular positions looking at conformability.