
231From Frictional Instabilities to Friction-Induced Self-Organization
–0.5
–1
–1.5
–2
–2.5
–1 49 14 19
Number of Scans
24 29
8
7
6
5
4
3
2
1
0
–1
4
9
14
19
Number of Scans
Kurtosis (K)
24
29 34
(e)
FIGURE 8.13 (Continued )
Variations of different roughness parameters during running-in period: (a) Root mean square,
(b) roughness average, (c) extreme-value height, (d) skewness, and (e) kurtosis.