Majmaah University
Homework Assignment # 4
Tribology , ME 428
Engineering College
Contact of Solid Surfaces
Due: Sunday, 15/5/1435
Mech.& Indus. Eng. Department
Answer all questions:
Q1-A ceramic ball with a diameter of 5mm is pressed into a hemispherical
recess of 10mm in diameter in a steel plate.
(a) What normal load is necessary to initiate yield in the steel plate;
(b) what is the radius of the contact; and
(c) at what depth does yield first occur?
The given parameter are:
Eceramic = 450 GPa; Esteel = 200 GPa, vceramic = vsteel = 0.3; Hceramic = 20GPa;
Hsteel = 5 GPa. Assume that H ~ 2.8Y
Q2- A 30 mm diameter steel ball and a 45 mm diameter copper one are
brought into contact. The mechanical properties of steel and copper as
follows:
Material
steel
copper
E, kg/mm2
20×103
11×103
σ, kg/mm2
32
14
v
0.33
0.33
Plot the radius of the contact area against the applied load up to the elastic
contact limit.