Fundamental Concepts and Terminology of Rolling Bearings

1) Service life: The service life of an individual rolling bearing refers to the number of revolutions one bearing ring (or washer) makes relative to another bearing ring (or washer) before the first signs of fatigue propagation appear on the material of either bearing ring (or washer) or rolling element.

2) Reliability (falling within the scope of bearing life) denotes the percentage of a set of nearly identical rolling bearings operating under identical conditions that are expected to achieve or exceed the specified life.

The reliability of an individual rolling bearing represents the probability that the bearing will achieve or exceed its specified life.

3) Static load: The load acting on a bearing when the relative rotational speed between the bearing rings or washers is zero (for radial or thrust bearings) or when the rolling elements exhibit no movement along the rolling direction (for linear bearings).

4) Dynamic load: The load acting on the bearing when the bearing rings or washers rotate relative to each other (for radial or thrust bearings) or when the rolling elements move along the rolling direction (for linear bearings).

5) Rating life: The expected life based on the basic dynamic rating for radial or axial load.

6) Basic rated life: For bearings manufactured from contemporary high-quality materials with good machining quality and operating under conventional conditions, the basic rated life denotes the rated life associated with a 90% reliability level.

7) Radial basic rated dynamic load: Refers to the constant radial load a set of rolling bearings can theoretically withstand. Under this load, the basic rated life of the bearing is one million revolutions. For single-row angular contact bearings, this load denotes the radial component of the force inducing pure radial displacement between the bearing rings.

8) Axial basic rated dynamic load: Denotes the constant axial load a rolling bearing set can theoretically withstand, under which the bearing's basic rated life is one million revolutions.

9) Radial (or axial) equivalent dynamic load: Refers to a constant radial load (or central axial load) under which the rolling bearing exhibits the same service life as under actual load conditions.

10) Radial (or axial) basic static load rating: The radial static load (or axial static load) corresponding to the calculated contact stress generated at the centre of contact between the rolling elements and raceway under maximum load: 4600 MPa for self-aligning ball bearings (radial); 4200 MPa for other types of radial ball bearings (radial) and thrust ball bearings (axial); 4000 MPa for radial (radial) and thrust roller bearings (axial).

Notes: 

1. For single-row angular contact ball bearings, the radial rated static load refers to the radial component of the load causing pure radial displacement between the bearing rings.

2. Under static load conditions, these contact stresses refer to the stresses causing total permanent deformation of the rolling elements and raceways equivalent to approximately 0.0001 times the rolling element diameter.

11) Radial (or axial) equivalent static load refers to the radial

(or central axial) static load that produces equivalent contact stresses at the centre of contact between the load-bearing rolling element and raceway.Translated with DeepL.com (free version)