When considering load, a distinction is made between:
- load direction
type of load
- dynamic load, i.e. there is relative sliding movement in the loaded bearing
- static load, i.e. there is no relative movement in the loaded bearing
- constant load (fig. 4), i.e. the direction in which the load is applied does not change and the same part of the bearing (loaded zone) is always subjected to the load
alternating load (fig. 5), i.e. change of load direction so that zones at opposite positions in the bearing are alternately loaded and unloaded
Loads of constant direction (fig 4) are loads where the direction in which the load is applied does not change, i.e. the same part of the bearing (loaded zone) is always subjected to the load. Alternating loads (fig 5) change direction so that loaded zones at opposite positions in the bearing are continuously loaded and unloaded.
A load is dynamic (fig 6) when sliding movement takes place in the loaded bearing. This causes wear in the bearing. A bearing is statically loaded (fig 7) when no movement takes place in the bearing even though the load need not be constant in magnitude and/or direction. Under static load it is the strength of the material of the bearing or rod end which is the limiting factor. Vibrations, or loads which alternate at high frequency, are considered as special cases of dynamic load where material fatigue may be an additional failure criterium.