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SPIP Classic Roughness Parameters for Profiles

 

The SPIP Classic Roughness Parameters for Profiles contains the profile roughness parameters implemented before SPIP version 6.1 where SPIP was extended with various standards for profile roughness. Thus these parameters are maintained for backward compatibility. The profile roughness are using the R prefix and have equivalent Image Roughness parameters using the S prefix and often calculated in the same way. For example is the Arithmetic mean deviation of a profile Ra similar to the Sa parameter of an image and you will find a more thorough description of the parameters in the section SPIP Classic Roughness Parameters for Images

Rp: Maximum profile peak height
The maximum height value Rp = Zmax

Rv: Maximum profile valley depth
The minimum height value Rv = Zmin
Rt: Total height of the profile
The difference between the maximum height value and the minimum height value of the profile

Ry: Peak-Peak

Rt,: Peak-Peak, ASME Definition

Rz,: Peak-Peak, ISO Definition

This is the difference between the maximum height and the minimum height of the profile

Peak-Peak Height Roughness Parameter, Sz, St, Sy, Rz, Rt, Ry

R10z:Ten Point Height

Rz_tph:Ten Point Height old legacy term

Ten Point Height is defined as the average height of the five highest local maximums plus the average height of the five lowest local minimums:

Ten Point Height Roughness Parameter, S10z, R10z

Ra: Arithmetic mean deviation of the profile

 

Where n is the number of points in the profile, and Ziis the height value at point i.
Rq: Root mean square deviation of the profile

 

Where n is the number of points in the profile, and Ziis the height value at point i.
Rsk Skewness of the profile height distribution

Where n is the number of points in the profile, and Zi is the height value at point i. If this parameter is zero it means that the height distribution is symmetric, for example Gaussian distributed. Peaks will cause Rsk to become positive and valleys will cause Rsk to become negative.
Rku: Kurtosis of the profile height distribution

Where n is the number of points in the profile, and Zi is the height value at point i. The Kurtosis describes the sharpness of the height distribution, A Gaussian distribution has a Kurtosis close to 3. Wider distributions have a kurtosis less than 3 and narrower distributions a kurtosis greater than 3. High peaks or deep valleys will influence the kurtosis strongly.
Rds: Density of Summits

This is the number of local maximums per length unit

Density of Summits, Sds

where n is the number of profile points and δx the sampling distance
Rsc: Mean Summit Curvature

Rsc, is the average of the principal curvature of the local maximums on the profile, and is defined as:

Root Mean Square Gradient Roughness Parameter, Sdq for all local mmaximums
Rmean: Mean Height

Bearing Curve Based Parameters

Rbi: Surface Bearing Index

Rci: Core Fluid Retention Index

Rvi: Valley Fluid Retention Index

Rpk: Reduced Summit Height

Rk: Core Roughness Depth

Rvk: Reduced Valley Depth

Rdc-h: Height Intervals of Bearing Curve

RMR1: Upper Material Portion

RMR2:Lower Material Portion
These parameters are calculated from the Material Ratio curve ( also called Abbott or Bearing Curve) in the same way as their equivalent Image roughness parameters see for example Sbi

 

 

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