Friction and Wear Homework
Homework #1
1. There are several different layers that make up the surface and near surface
regions of a solid material prior to reaching the bulk material. The following
is a discussion of each of these layers and why they differ from the bulk
material. The first layer above the bulk material is referred to as the
“worked” layer. This layer is caused by the forming or shaping of the piece of
bulk material and, because of these processes, contains a lot of stress. The
layer above the “worked” layer is referred to as the “Beilby” layer that is
caused by fine finishing machining processes (e.g. polishing). During
polishing the crystalline structure of the bulk material is broken up into a
large number of much smaller crystals. The “oxide” layer resides above the
“Beilby” layer and is caused by the bulk material reacting with the oxygen
within the environment surrounding the bulk material. The final layer on top
of the bulk material is the “absorbed gasses and water vapor” layer which, as
the name suggests, contains water vapor and various gasses that are either
trapped to the surface of have chemically bonded with the surface of the bulk
material.
2. Profilometers are used to characterize the roughness of characteristics of
solid surfaces. There are two types of profilometers used today: contact and
optical (non-contact). The contact profilometers utilizes a stylus, like a
phonograph, that is moved laterally across a service of a component and as it
moves vertically due to imperfections in the services it registers the distance
the stylus moves, mapping the surface of the part. Optical, or non-contact,
profilometers use many different techniques to scan and measure the
surfaces of parts with light or optics.
3. The work for this problem is provided in Hw1-3.xls and HW1_3.MPJ:
a. Colum C in Hw1-3.xls
b. From the notes Ra= mean value/length however length was not given
and assumed to be 100mm. Therefore Ra=0.4 micrometers
Rq= square root of the mean^2/length Rq=0
c. The histogram was approximately Weibull distributed (see below)
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Friction and Wear Homework
Homework #1
Histogram of C1
Weibull
Shape 53.17
Scale 4.055
N
101
14
12
Frequency
10
8
6
4
2
0
3.750
3.825
3.900
3.975
C1
4.050
4.125
4.200
Mean=4.01
Variance=.000911
Sk=-1184.3
K=-58986.3
Autocorrelation Function for C1
(with 5% significance limits for the autocorrelations)
1.0
0.8
Autocorrelation
0.6
0.4
0.2
0.0
-0.2
-0.4
-0.6
-0.8
-1.0
1
d.
2
3
4
5
6
7
8
9
10
Lag
4. Compute the statistical data from the given values: See file HW1_4.xlsx
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