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Arithmetical Mean Height (Ra, Pa, Wa) | Surface Roughness Parameters

Arithmetical Mean Height (Ra, Pa, Wa)

Arithmetical mean height indicates the average of the absolute value along the sampling length.

When dealing with the roughness profile, Ra is referred to as the arithmetic mean roughness, while Wa is referred to as the arithmetic mean waviness for the waviness profile.

Surface Roughness Parameters

This section explains the main parameters of ISO 4287:1997. Each parameter is classified according to primary profile (P), roughness profile (R), and waviness profile (W) in order to evaluate different aspects of the profile. (When the wavelengths of the waviness and primary profile components are compared, the surface roughness component is the asperity component of that which has the comparatively shorter wavelength.)

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Peaks and valleys in the height direction Arithmetical mean height (Ra, Pa, Wa)
Maximum height of profile (Rz, Pz, Wz)
Maximum profile peak height (Rp, Pp, Wp)
Maximum profile valley depth (Rv, Pv, Wv)
Mean height of profile elements (Rc, Pc, Wc)
Total height of profile (Rt, Pt, Wt)
Average amplitude in the height direction Root mean square deviation (Rq, Pq, Wq)
Average characteristics in the height direction Skewness (Rsk, Psk, Wsk)
Kurtosis (Rku, Pku, Wku)
Horizontal direction Mean width of the profile elements (RSm, PSm, WSm)
Hybrid Root mean square slope (RΔq, PΔq, WΔq)
Areal material ratio curve and probability density function Load length ratio (Rmr (c), Pmr (c), Wmr (c))
Profile cut level difference (Rδc, Pδc, Wδc)
Relative load length ratio (Rmr, Pmr, Wmr)
Material ratio curve (BAC)
Probability density function (ADF)

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