軸承修正額定壽命 L_nm 計算器

ISO 281 expresses modified rating life as L_nm = a₁ × a_ISO × L₁₀. The subscript n is failure probability in percent.

It is a statistical fatigue rating under the standard’s conditions, not a guarantee of service life.

L10 is basic rating life at 90% reliability under the conventional conditions stated by ISO 281. L_nm applies the reliability factor a₁ and the condition-dependent a_ISO factor.

Wear, corrosion and electrical erosion are outside ISO 281 rating-life scope.

Use the ISO 281:2007 factor for the required reliability:

• 90%: 1.00
• 95%: 0.64
• 96%: 0.55
• 97%: 0.47
• 98%: 0.37
• 99%: 0.25

Higher required reliability gives a lower rating life.

The life exponent p is 3 for ball bearings and 10/3 for roller bearings. It appears in the basic rating life formula L₁₀ = (C/P)^p and reflects the different contact geometry: point contact for balls, line contact for rollers.

Do not choose a_ISO from a generic clean or dirty label. Determine it with the ISO 281 method or verified bearing-manufacturer software or diagrams for the exact bearing and operating conditions.

The determination uses bearing-specific and operating inputs such as viscosity ratio, contamination factor, fatigue load limit and equivalent load. This calculator only applies the supplied value.