Page 203 - Tribology in Machine Design

188 Tribology in machine desigr

and the pressure equation becomes

2
2
For the maximum value of/? write x=x' = Be/(2h), i.e. 1 = (h — e )/h.
Equation (5.33) then becomes

where a = e/h denotes the attitude of the bearing or pad surface.

5.4.3. Equilibrium conditions

Referring to Fig. 5.11, P is the load on the slider (per unit length measured
perpendicular to the direction of motion) and F' is the pulling force equal
and opposite to the tangential drag F. Similarly Q and F r are the reaction
forces on the oil film due to the bearing, so that the system is in equilibrium
(a necessary condition is that the pad has sufficient freedom to adjust its
slope so that equilibrium conditions are satisfied) under the action of the
four forces, P,Q,F' and F r. Again, P and F' are equal and opposite to the
resultant effects of the oil film on the slider, so that

For the former, eqn (5.33) gives

and writing a = e/h this reduces to

Similarly, for the tangential pulling force, eqns (5.31) and (5.36) give

and integrating between the limits ± B/2, this reduces to

5.4.4. The coefficient of friction and critical slope
If/ is the virtual coefficient of friction for the slider we may write