Page 99 - Tribology in Machine Design

Elements of contact mechanics 85

Numerical example

Now consider a circular contact 20mm in diameter with one surface
1
stationary and one moving at F = 0.5ms" . The bodies are both of plain
carbon steel (C%0.5%) and at 24 °C bulk temperature. We recall that the
assumption in the Archard model implies that the stationary surface is
essentially a cylindrical body of diameter 20 mm and length 10 mm with one
end maintained at the bulk temperature of 24 °C. The coefficient of friction
is 0.1 and the load is W = 3000 N (average contact pressure of 10 MPa). The
properties of contacting bodies are (see Table 3.3 or ESDU-84041 for a
more comprehensive list of data)

Therefore

If we assume that all the frictional energy is conducted into the moving
surface (L m = 169>5), we can then use eqn (3.24)

and if all the frictional energy went into the stationary surface (L s =0), then
we use eqn (3.21)

The true temperature rise for the two surfaces is then obtained from eqn
(3.28) and is

3.7.7. Contacts for which size is determined by load
There are special cases where the contact size is determined by either elastic
or plastic contact deformation.
If the contact is plastic, the contact radius, a, is

where H^is the load and p m is the flow pressure or hardness of the weaker
material in contact.
If the contact is elastic