Surface finish characterization
Once a satisfactory profile is obtained, it can be analysed and represented by a variety of means. This raises the question of what particular number, parameter or descriptor should be used. Unfortunately, there is no such thing as a universal parameter or descriptor and one must select from the ones published in the ISO standards.
With reference to Figure 6.5, the ADF (Amplitude Distribution Function or height distribution function) is a histogram where the value of p(y) represents the fraction of heights lying in the stratum between y and (y + dy). If the ADF is integrated, the BAC or Abbott-Firestone Curve or Material Ratio Curve is obtained. The BAC can also
- Figure 6.5 A profile and the corresponding height distribution function and bearing area curve
be generated by slicing the profile in a straight line parallel to the mean from the highest peak down, plotting the total length revealed as a fraction of the profile length under consideration. This is the equivalent of a perfect abrasion or wear process. Examples of the graphical outputs as well as parameters are shown in Figure 6.6. This is a trace from a fine-turned surface, showing the conventional turning unit event 'cusp' surface form. The peak spacing is approximately 115um and the peak to valley height is 45um.
- Profile Trace of a Fine-Turned Surface
XPI IX)
/FILTER
XPI IX)
/FILTER
Amplitude Distribution Function
8.78 18.12 37.67 31.84 31 .<2 44.64 8.51 2.28 38.22 41.99 33.64 39.49 35.83 26.52 18.12 22.44
HE1SHT
/FILTER
18.8
Freq X
Bearing Area Curve ss-
BEflRIHS
|
Ra |
8.78 |
|
Rt |
44.64 |
|
HSC |
35 |
|
TP1B |
33.13 |
|
TP28 |
28.12 |
|
TP38 |
24.17 |
|
1P48 |
28.21 |
|
TPS6 |
15.83 |
|
TP68 |
12.92 |
|
TP78 |
18.62 |
|
TP80 |
8.54 |
|
TP98 |
Figure 6.6 A profile of a fine-turned, surface and the corresponding ADF and BA C curves |
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