Proposals of methods of oil capacity calculation

The aim of this work is to compare various methods of oil capacity calculation for surfaces containing cavities. In reference method, oil capacity was computed by summation of volumes contained in all the holes of measured surface using TalyMap software. Oil retention volume was calculated also on the basis of material ratio curve using the Svk and Sr2 parameters from Sk parameters group (areal extension of ISO 13565-2 standard). The second and third procedures were developed on the basis of rotation of material ratio curve axes. The fourth method is based on determination of point of maximum curvature of the normalized material ratio curve. It was found that in the most cases it was possible to obtain correct values of oil capacity using the Sk parameter family. However when the slope of material ratio curve in its middle part (core roughness) is small or high, the errors of oil capacity estimation may be large; up to 80%. In those cases the other methods gave better results–usually errors of oil capacity estimation were not higher than 10%; average deviations were about 5%. Determination of transition point between valleys and plateau regions as the point of maximum curvature of the normalized material ratio is recommended. The new proposals of oil capacity calculation can be used also for surfaces with cross-hatched pattern.