Majmaah University
Tribology , ME 428
Homework Assignment # 3
Engineering College
Due: Sunday, 23/11/1434
Surface roghness
Mech.& Indus. Eng. Department
Answer all questions:
1- A rectilinear pen recording of a diamond turned surface is shown in figure
below. The sampling length (L) was 0.8 mm and the H/V magnification
ratio was 5000/100. Calculate the center-line-average value Ra if the area
(in square millimeters) enclosed above and below the mean line are as
follows:
A
60
B
115
C
96
D
92
E
109
F
70
2- A series of waves takes the form of equilateral triangles of length of side 40
mm. Taking five waves as representing a sampling length, determine Ra value
when the vertical magnification is × 5000.
3- A sample of a surface consists of a surface profile of 100 triangular
asperities having a constant flank angle α and maximum peak valley height of
1, 2, 3, etc. µm. Assuming that all valleys lie at the same level; find the
position of the centre-line and calculate C.L.A. values of the profile. Plot the
all-ordinate distribution of this profile and hence determine the R.M.S. and
C.L.A. value. Does the order in which the peaks occur affect your answer?
4A surface is represented by a series of sine waves. The sine wave is
represented by: 𝑧 = 𝐴𝑠𝑖𝑛Ө. Take one wave Ө = 0~2𝜋 as representing a
sample length and determine CLA and RMS value of this surface.
With my best wishes
Prof Dr. Shemy M. Ahmed