ISO 281 Bearing Life Calculation Reference Guide
International standard for rolling element bearings rating life and dynamic fatigue capacity sizing.
Standard Scope
Defines the dynamic load ratings and calculation methods for the nominal rating life of rolling bearings. It provides formulas to estimate the L10 fatigue life, representing the number of revolutions 90% of a large group of identical bearings can achieve before fatigue spalling begins.
Typical Applications
- •Rotating machinery component selection.
- •Electric motor shaft support design.
- •Automotive axle and transmission bearing sizing.
- •Industrial gearbox spindle sizing.
Key Engineering Concepts
Dynamic Load Rating (C)
Constant radial (or axial) load that a bearing can endure for a nominal life of 1 million revolutions.
Equivalent Dynamic Load (P)
Single load vector that represents the combined radial and axial loading forces.
Fatigue Exponent (p)
non-linear scaling factor (p = 3 for ball bearings, p = 3.33 for roller bearings).
Reliability Adjustment
Scaling factors to calculate bearing life at reliabilities higher than 90%.
Engineering Notes & Best Practices
- •Standard fatigue life equations assume clean lubrication conditions and rigid housings.
- •Dents from hard particles can reduce actual service life to a fraction of the L10 estimate.
- •Fits must be checked to prevent reducing internal clearance, causing thermal locking.
Official Standards Reference
Rolling bearings - Dynamic load ratings and rating life
The primary international standard for bearing dynamic ratings and fatigue life calculations.