3D Functional Parameters
Spk/Sk (Reduced Peak Height to Core Ratio), Svk/Sk (Reduced Valley Depth to Core Ratio), Spk/Svk (Reduced Peak Height to Reduced Valley Depth Ratio)
The ratios of the various areal material ratio parameters Spk/Sk , the Reduced Peak Height to Core Ratio, Svk/Sk, the Reduced Valley Depth to Core Ratio, and Spk/Svk, the Reduced Peak Height to Reduced Valley Depth Ratio may be helpful in further understanding the nature of a particular surface texture. In some instances, two surfaces with indistinguishable roughness average (Sa) may be easily distinguished by a ratio such as Spk/Sk. For example a surface with high peaks as opposed to a surface with deep valleys may have the same Sa but with vastly different Spk/Sk values.
By considering the ratios such as Spk/Sk, Svk/Sk and Spk/Svk one may determine quantitatively the dominance of peak structures relative to valley structures. In typical tribological applications such as seals and bearings these ratios may be useful in differentiating surfaces that have similar surface roughness as measured by Sa. The ratios may be further thought of as a measure of the texture amplitude distribution normalized by the overall roughness magnitude and thus may be used to characterize the texture amplitude symmetry.