The service life of rolling bearing is the operation time for the rolling bearing to maintain normal function. Under normal conditions, the service life of the bearing is consistent with the calculated life. Its termination is plastic deformation for static load bearing and fatigue and wear for dynamic load bearing. Early damage of bearings means abnormal termination of service life.
1. Normal service life
The following assumptions are assumed when considering the fatigue life of bearings:
● correct installation;
● the lubrication is in good condition and remains unchanged throughout the operation period;
● the load and speed used for calculation conform to the actual working conditions;
● the bearing will not be polluted during the whole operation period;
● use the actual working temperature when determining the working viscosity;
● the service life limited by wear shall not be shorter than the fatigue life.
In this case, the calculated life can be consistent with the actual service life.
Fatigue life is the upper limit of normal service life. Wear often leads to failure to reach this limit. If the wear life is longer than fatigue life, the service life is equal to fatigue life; On the contrary, the service life is equal to the wear life
2. Early damage
Early damage means the abnormal termination of bearing service life. Early damage mainly includes plastic deformation, early wear, corrosion, fragmentation and vibration caused by improper installation, maintenance, use or poor service conditions.
Plastic deformation: if the load of the bearing is too large in the state of static or slow rotary motion, such as bearing too large constant load, impact load or impact, the raceway surface will produce too large plastic deformation.
Early fatigue: bearing manufacturing or material defects, improper installation and maintenance, poor support and the actual load is greater than the calculated load may lead to the overload of the bearing raceway surface, so that the actual fatigue life is far lower than the calculated life.
Early wear: the early wear of bearing is mainly due to the entry of foreign matters into the bearing or the failure of lubricant. In some In the transmission device, metal chips may enter the bearing with the circulating oil, and foreign matters such as dust and sand may enter the bearing through the loose seal or damaged seal ring. Due to the grinding effect of foreign matters such as dust, sand and wear debris, the rolling surface of the bearing will become rough and gray. When the wear is serious, the clearance of the bearing will increase significantly, and the profile of the raceway will also change.
Corrosion: harmful substances such as water, acid and alkali enter the bearing, improper selection of lubricant or excessive air humidity during storage are the main reasons for bearing corrosion and damage. If there is serious corrosion on the raceway surface, it will directly affect the smooth operation of the bearing and produce large noise. The grinding effect of rust will lead to rapid wear of the bearing, and the rusted part may become the starting point of fatigue spalling.
Fragmentation: in the bearing installation, the impact force of hammering will cause the fragmentation of the bearing ring due to the failure to use the correct installation tools. The plastic deformation during installation may also lead to the fragmentation of bearing rings in use, or become the starting point of fatigue spalling.
Vibration marks: when the bearing bears high static load, vibration under static state or current passes through, the vibration marks regularly distributed on the whole circumference may appear in its raceway, which will affect the smooth operation of the bearing and produce large noise.