A sliding bearing’s lifetime is a complex story, which results from the sum of the many parameters’effect. In our section: Parameters for bearing selection, we discuss the most important.These are:
- Bearing housing
- Bearing play
- Operating environment
- Opposing rotational partner
There are many more factors that affect a slide bearing’s lifetime, however, with the help ofthose mentioned above, it is possible to determine approximately how long a slide bearing willfunction as it ought. The reason for using the phrase ”as it ought” is that the slide bearing’slifetime is wholly dependent on how much wear or abrasion the design can allow. The slidebearing and its opposing rotational partner function quite simple as a closed tribological system.When the sliding surface of the bearing has worn down to the level that can be allowed,before the clearence is adventured, the bearing is worn out. Below, the wear factor k is shownas a function of some normal lubrication conditions.
The wear factor is dependent on the lubricant condition and the materialcombination. It is normally determined by laboratory testing and is basedon Archard’s wear equation.
Where V is the volume of material worn away, S the total sliding length.F the normal force i.e. the load, and H is the hardness of the worn material.
Below is presented a summary of the factors influencing the rate of wear and in consequence to be considered during design.
The values should be viewed as a rule of thumb and not exact data.
In contrast to ball bearings, lifetime calculations for slide bearings are very approximate. Theexception is fully lubricated slide bearings, where a numerical calculation can be performed, asthere is good theory as a base. However, since for the most slide bearings interface lubricationprevails, the lifetime calculations are difficult to perform based on just theoretical formulae. Forinterface lubricated slide bearings, laboratory experiment often forms the base.