Static Load Rating C0
The static load rating is calculated according to DIN ISO 76. The static load rating C0 represents the load at which the Hertz pressure between rolling elements and raceways at the point of maximum load reaches the following values:
- For roller bearings: 4,000 MPa
- For ball bearings: 4,200 MPa
For rolling bearings, this is the material's load limit that results in permanent deformation of 0.0001 times (0.01%) the rolling element diameter. If the load exceeds the static load rating, the function, noise level, and accuracy of the bearing arrangement will be adversely affected.
Static Load Safety Factor S0
The calculation of the static load safety factor must be performed separately for the radial and axial bearing components. To avoid permanent plastic deformation of the bearing, the static load safety factor S0 for machine tool applications should be as follows:
S0 = Static load safety factor
C0 = Static load rating [N]
P0 = Static equivalent bearing load [N]
- S0 ≥ 4: For applications with high precision requirements and high demands on bearing smoothness
- S0 ≥ 3: For applications with normal demands on bearing smoothness
- S0 ≥ 2.5: For applications with lower demands on bearing smoothness and running accuracy
Calculation of static equivalent bearing load P0:
When loads Fr and Fa act simultaneously:
P0,rad = Fr + 0.26 · Fa (for Fa / Fr ≤ 4.2)
P0,ax = Fa + 3.8 · Fr
Static Limiting Load Diagrams
Static limiting load diagrams are used to:
- Verify the selected bearing size under predominantly static loading conditions
- Determine the maximum tilting moment MK the bearing can support alongside the axial load
The static limiting load diagrams incorporate the static load safety factor S0 ≥ 4 as well as the strength of the screws and bearing rings.
| Example: Static limiting load diagram legend | |
|---|---|
| 1 | Bearing / Size |
| 2 | Permitted range |
| 3 | Non-permitted range |
| Fa | Axial load [kN] |
| MK | Maximum tilting moment [kNm] |
(Note: This is a general example. Please refer to the corresponding product section for specific limiting load diagrams and values for each bearing type.)
Dynamic Load Rating C
The dynamic load rating is calculated according to DIN ISO 281. The dynamic load rating C represents a load of invariable magnitude and direction at which a sufficiently large quantity of identical bearings achieves a nominal life time of one million revolutions.
Life Time
Life time calculations use the following procedures:
- Nominal life L10 according to ISO 281 (million revolutions)
- Nominal life L10h according to ISO 281 (operating hours)
Where:
L10 = Nominal life (million revolutions)
L10h = Nominal life (hours)
C = Dynamic load rating [N]
P = Dynamic equivalent bearing load [N]
p = Life exponent (for roller bearings p = 10/3)
n = Operating speed [min-1]
The extended modified life Lnm is calculated according to DIN ISO 281 Supplement 4 (ISO/TS 16281).
Where a1 = 1 (90% survival probability), and aISO is the life factor considering operating conditions.
myonic is happy to perform these calculations for you. The following information is required:
- Application details (drawings, sketches, specifications)
- Workpiece dimensions and weight
- Load cycle details (cutting forces, speeds, operating duration)
Service Life
The service life is the actual life achieved by the bearing. It may deviate significantly from the calculated life. Possible factors affecting service life include wear or fatigue caused by:
- Deviating operating data
- Misalignment between shaft and housing
- Operating clearance too small or too large
- Contamination
- Insufficient lubrication
- Excessive operating temperature
- Oscillating bearing movement with very small oscillation angles (brinelling)
- Vibration stress and brinelling
- Very high impact loads (static overload)
- Pre-damage during assembly
The service life cannot be accurately determined by mathematical methods. The most reliable estimation is achieved by comparison with similar installation cases.