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Area Roughness Parameters

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.

Smr(c) Areal material (bearing area) ratio

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.

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Height Sa (arithmetical mean height)
Sz (Maximum height)
Sq (Root mean square height)
Ssk (Skewness)
Sku (Kurtosis)
Sp (Maximum peak height)
Sv (Maximum pit height)
Spatial Sal (Auto-correlation length) / Str (Texture aspect ratio)
Std* (Texture direction)
Hybrid Sdq (Root mean square gradient)
Sdr (Developed interfacial area ratio)
Functional Smr(c) Areal material (bearing area) ratio
Smc(mr) Inverse areal material ratio
Sk (Core roughness depth)
Spk (Reduced peak height)
Svk (reduced dale height (reduced valley depth))
Smr (Peak material portion)
Smr2 (Valley material portion)
Sxp (Peak extreme height)
Functional volume Vvv (Dale void volume)
Vvc (Core void volume)
Vmp (Peak material volume)
Vmc (Core material volume)
Feature Spd (Density of peaks)
Spc (Arithmetic mean peak curvature)
S10z / S5p / S5v / Sda(c) / Sha(c) / Sdv(c) / Shv(c)

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