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No. 99MBB091A
14.6 Parameters Related With Motif
The motif method is a French standard for evaluating surface roughness.
Generally, when waviness components are removed from an assessed profile using filters, the
assessed profile is subjected to distortion. One method to remove waviness components from
an assessed profile without distorting it is by the motif method.
With this method, an assessed profile is divided into units called “motifs” which are based on
the wavelength of a component to be removed, and parameters to evaluate the profile are
calculated from each motif.
The following will briefly describe the methods of obtaining the motif parameters.
14.6.1 How to obtain roughness motifs
1)Determine the condition of the peak height
1
n
0.05 ×Hmin =
n
i=1
HRi
∑
LH LH
HRi
HRi
• Divide the assessed profile into sections with a set
length LH (=LR/2, LR: upper limit of roughness
motif length), then obtain the distance (HRi)
between the highest and lowest points.
• Obtain the condition (Hmin) of the peak height.
where n is the number of sections which can
secure the set length.
2)Obtain the highest point of peak and the lowest point of valley.
Peak
Peak
Valley
Valley
Motif
Hmin or greater
Peak and valley
• The peak and valley should have a height
difference of Hmin or greater.
The deepest point between two peaks is the
valley.
• A motif consists of the section between two
peaks.
3)Obtain the motif height.
Motif height
Peak
Peak
Valley
Motif
Motif height
• The motif height is defined as the difference
between the valley height and the lower peak
height.
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