Under a certain load, the number of cycles or hours the bearing undergoes before pitting is called bearing life.
The life of a rolling bearing is defined by the number of revolutions (or hours of work at a certain speed): bearings within this life span shall have initial fatigue damage (spalling or defect) occurring on any bearing ring or rolling body. However, both in laboratory experiments and in practical use, it is obvious that in the same working conditions the appearance of the same bearing, the actual life expectancy is very different. In addition there are several different definitions of bearing "life", one of which is called "Working Life", which indicates that the actual life expectancy of a bearing before the damage is caused by wear, damage, usually not by fatigue, but by wear, corrosion, seal damage and so on.
In order to determine the standard of bearing life, the bearing life and reliability are connected.
Because of the manufacturing accuracy, the material uniformity degree difference, even if is the same material, the same size of the same batch of bearings, in the same working conditions used, the length of the life is not the same. If the statistical life of 1 units, the longest relative life of 4 units, the shortest is 0.1-0.2 units, the longest and the shortest life ratio of 20-40 times. 90% bearings do not produce pitting, the number of cycles or hours experienced is referred to as bearing rating life