Page 204 - Tribology in Machine Design
P. 204
Sliding-element bearings 189
so that
Referring again to the equilibrium conditions, suppose a to be the angle in
radians between the slider and the bearing pad surface, then for equilibrium
we must have
Since a is very small we may write sin a « a and cos a = 1. Further, F r is very
small compared with Q, and so
A critical value of a occurs when F r =0, i.e.
where </> is the angle of friction for the slider. When a > </>, F r becomes
negative. This is caused by a reversal in the direction of flow of the oil film
adjacent to the surface of the pad. The critical value of a is given by eqn
(5.39). Thus
therefore
and so
5.5. Journal bearings 5.5.1. Geometrical configuration and pressure generation
In a simple plain journal bearing, the position of the journal is directly
related to the external load. When the bearing is sufficiently supplied with
oil and the external load is zero, the journal will rotate concentrically within
the bearing. However, as the load is increased the journal moves to an
