Maximum height (Rz)

Represents the sum of the maximum peak height Zp and the maximum valley depth Zv of a profile within the reference length.

• Indicated as Ry within JIS’94
• Profile peak: Portion above (from the object) the mean profile line (X-axis)
• Profile valley: Portion below (from the surrounding space) the mean profile line (X-axis)

Pz  Maximum height of the primary profile
Wz  Maximum height of the waviness

Note
Although frequently used, max height is significantly influenced by scratches, contamination, and measurement noise due to its reliance on peak values.

_{(In the case of a roughness profile)}

Maximum profile peak height (Rp)

Represents the maximum peak height Zp of a profile within the sampling length.

Pp  The maximum peak height of the primary profile
Wp  The maximum peak height of the waviness profile

_{(In the case of a roughness profile)}

Maximum profile valley depth (Rv)

Represents the maximum peak height Zp of a profile within the sampling length.

Pv　The maximum peak height of the primary profile
Wv　The maximum peak height of the waviness profile

_{(In the case of a roughness profile)}

Mean height (Rc)

Represents the mean for the height Zt of profile elements within the sampling length.

• Profile element: A set of adjacent peaks and valleys
• Minimum height and minimum length to be discriminated from the peaks (valleys)

Minimum height discrimination: 10% of the Rz value
Minimum length discrimination: 1% of the reference length

Pc  The mean height of the primary profile element
Wc  The mean height of the waviness element

_{(In the case of a roughness profile)}

Total height (Rt)

Represents the sum of the maximum peak height Zp and the maximum valley depth Zv of a profile within the evaluation length, not sampling length.

• Relationship Rt≧Rz applies for all profiles

Pt  The maximum total height of the profile (Rmax in the case of JIS’82)
Wt  The maximum total height of the waviness

Note
Rt is a stricter standard than Rz in that the measurement is conducted against the evaluation length. It should be noted that the parameter is significantly influenced by scratches, contamination, and measurement noise due to its utilization of peak values.

_{(In the case of a roughness profile)}

Ten-point mean roughness (Rzjis)

Represents the sum of the mean value for the height of the five tallest peaks and the mean of the depth of the five deepest valleys of a profile within the sampling length.

• Indicated as Rz within JIS’94

Note
Rzjis is equivalent to the parameter Rz of the obsolete JIS standard B0601:1994. Although ten-point mean roughness was deleted from current ISO standards, it was popularly used in Japan and was retained within the JIS standard as the parameter Rzjis.

_{(In the case of a roughness profile)}

Arithmetic mean deviation (Ra)

Represents the arithmetric mean of the absolute ordinate Z(x) within the sampling length.

Pa  The arithmetic mean height of the primary profile
Wa  The arithmetic mean waviness

Note
One of the most widely used parameters is the mean of the average height difference for the average surface. It provides for stable results as the parameter is not significantly influenced by scratches, contamination, and measurement noise.

_{(In the case of a roughness profile)}

Root mean square deviation (Rq)

Represents the root mean square for Z(x) within the sampling length.

Pq  The root mean square height for the primary profile
Wq  Root mean square waviness

Note
This is one of the most widely used parameters and is also referred to as the RMS value. The parameter Rq ７corresponds to the standard deviation of the height distribution. The parameter provides for easy statistical handling and enables stable results as the parameter is not significantly influenced by scratches, contamination, and measurement noise.

_{(In the case of a roughness profile)}

Skewness (Rsk)

The quotient of the mean cube value of Z (x) and the cube of R8 within a sampling length.

Rsk=0: Symmetric against the mean line (normal distribution)
Rsk>0: Deviation beneath the mean line
Rsk<0: Deviation above the mean line

Psk  The skewness of the primary profile
Wsk  The skewness of the waviness profile

Note
This parameter concerns height distribution. It is suitable for evaluating the abrasion and oil sump of lubricants for slide planes.

_{(In the case of a roughness profile)}

Kurtosis (Rku)

The quotient of the mean quadratic value of Z (x) and the fourth power of Rq within a sampling length.

Rku=3: Normal distribution
Rku>3: The height distribution is sharp
Rku<3: The height distribution is even

Pku  The Kurtosis of the primary profile
Wku  The Kurtosis of the waviness profile

Note
This parameter relates to the tip geometry of peaks and valleys and is suitable for analyzing the degree of contact between two objects.

_{(In the case of a roughness profile)}

Mean width (RSm)

Represents the mean for the length Xs of profile elements within the sampling length.

• Indicated as Sm within JIS’94
• Minimum height and minimum length to be discriminated from peaks (valleys)

Minimum height discrimination: 10% of the Rz value
Minimum length discrimination: 1% of the reference length

Psm  Mean width of the primary profile element
Wc  Mean width of the waviness element

Note
This parameter is used to evaluate the horizontal size of parallel grooves and grains instead of the height parameters.

_{(In the case of a roughness profile)}

Root mean square slope (Rdq)

Represents the root mean square for the local slope dz/dx within the sampling length.

Pdq  The root mean square slope for the primary profile
Wdq  The root mean square slope for the waviness

Note
The steepness of the surface can be numerically represented with this parameter.

_{(In the case of a roughness profile)}

Material ratio curve and probability density curves

Material ratio curves signify the ratio of materiality derived as a mathematical function of parameter c, where c represents the height of severance for a specific sample. This is also referred to as the bearing curve (BAC) or Abbott curve. Probability density curves signify the probability of occurrence for height Zx. The parameter is equivalent to the height distribution histogram.

_{(In the case of a roughness profile)}

Material ratio (Rmr(c))

Indicates the ratio of the material length Ml(c) of the profile element to the evaluation length for the section height level c (% or μm).

Pmr (c)  The material length rate of the primary profile (formerly tp)
Wmr (c)  The material length rate of the waviness

_{(In the case of a roughness profile)}

Profile section height difference (Rdc)

Rdc signifies the height difference in section height level c, matching the two material ratios.

Pdc  The section height level difference for the primary profile
Wdc   The section height level difference for the waviness profile

_{(In the case of a roughness profile)}

Relative material ratio (Rmr)

Rmr indicates the material ratio determined by the difference Rδc between the referential section height level C₀ and the profile section height level.

Pmr  The relative material length rate of the primary profile
Wmr  The relative material length rate of the waviness profile

_{(In the case of a roughness profile)}

Parameters of a surface with stratified functional properties

Rk, Mr1, and Mr2 values are calculated from the linear curve (equivalent linear curve) minimizing the sectional inclination corresponding to 40% of the material ratio curve. Draw a triangle with the area equivalent to the protrusion of the material ratio curve segmented by the breadth of the parameter Rk and calculate parameters Rpk and Rvk.

Rk  Core roughness depth
Rpk  Reduced peak height
Rvk  Reduced valley depth
Mr1, Mr2  Material portion

Note
This function is used to evaluate friction and abrasion. It is also used to evaluate the lubricity of engine cylinder surfaces.

Motif parameters

Motif parameters are used for the evaluation of surface contact status based on the enveloped features of the sample surface.

AR  Mean spacing of roughness motifs: the arithmetic mean of roughness motifs ARi calculated from the evaluation length
R  Mean depth of roughness motifs: the arithmetic mean of the roughness motif depth Hj calculated from the evaluation length
Rx  Maximum depth of roughness motifs: the maximum value of the Hj calculated from the evaluation length
AW  Mean spacing of waviness motifs: the arithmetic mean of the waviness motif AWi calculated from the evaluation length
W  Mean depth of waviness motifs: the arithmetic mean of the waviness motif depth HWj calculated from the evaluation length
Wx  Maximum depth of waviness motifs: the maximum value of the HWj calculated from the evaluation length

Note
These parameters are suited to evaluating the slippage of lubrication mechanisms and contact surfaces, such as gaskets.