Smr(c) (Areal material ratio)
The areal material ratio curve of an area is a curve representing heights at which the areal material ratio changes from 0% to 100%.
An areal material ratio represents the area with a specific height c or higher. The areal material ratio at height c corresponds to Smr(c) in the figure below.
When a secant line of an areal material ratio curve, which covers 40% of the difference in the areal material ratio, is shifted from the areal material ratio of 0% the position at which the secant line has the smallest gradient is called the center portion of the areal material ratio curve.
The equivalent line is the line where the sum of the squared deviation in the vertical-axis direct is the smallest in the center portion.
The section of the equivalent line between the two height positions where the areal material ratio is 0% and 100% is called the core surface. The peaks with a height above the core surface are called reduces peaks, while the valleys below the core surface are called reduced vallesy.
The core surface represents the height of the area that makes contact with other objects after initial abrasion.