The Basic Concept of Bearing Fatigue Life
Bearing fatigue life is the most important characteristics used to measure the relative degree of “wear” experienced by a bearing from a given operating condition. The ball and roller bearings used in machines and systems typically experience some degree of “wear” from moving parts that induce vibration and heat. This wear can cause damage to the bearings and result in premature failure due to bearing fatigue.
A bearing’s fatigue life is determined by its load rating (or load capacity), its operating environment, as well as its operating temperature. The higher the load rating on the bearings, the greater the stress applied to its components. A bearing that is subject to greater loads will likely have a lower fatigue life than one with a lower load rating. Additionally, a bearing that is subject to a harsher operating environment will have a shorter fatigue life due to the greater challenges to its performance and durability. Operating temperature also affects bearing fatigue life, as higher temperatures can cause accelerated fatigue in the components due to increased friction and vibration.
The most important factor to consider when considering the fatigue life of a bearing is the level of stress being applied to the bearing. If a bearing is subject to higher levels of stress, it will likely have a shorter fatigue life. The stress can be applied in the form of a radial force, axial force, or vibration. Radial forces cause a bearing to roll or spin along its axis of rotation, whereas axial forces cause a bearing to move in up-and-down or side-to-side motions. Vibrations cause a bearing to move in a combination of both racking and axial motions, resulting in higher levels of stress being applied to the bearing.
The fatigue life of a bearing can also be affected by its lubrication. Bearings that are well lubricated will experience fewer defects due to the lubrication reducing friction between the moving parts. This reduced friction helps to lower the stress on the bearing and therefore increases its expected fatigue life. Additionally, the more frequent the lubrication, the longer the bearing’s fatigue life will be.
Finally, bearing fatigue life is also affected by the bearing’s design. Bearings with higher load-carrying capacity and higher wear resistance will have longer fatigue lives than those with lower load-carrying capacity and wear resistance. Furthermore, bearings with specialized lubrication systems, such as those that utilize oilier, anti-corrosive, or higher-temperature lubricants will often experience longer fatigue lives.
In summation, bearing fatigue life is affected by the bearing’s load rating, its environment, operating temperature, the applied stress, lubrication frequency, and its design. Therefore, it is important to select the right bearing for an application in order to maximize its fatigue life and minimize potential damage.
