Hybrid Bearings: L₁₀ Life

The Adjusted Bearing Life Calculation
L_na = a¹a²a³ (C/P)^p

Where:

a1 is a Reliability Adjustment Factor a2 is a Material Adjustment Factor a3 Operating Condition Adjustment Factor C is Basic Dynamic Load Rating P is the Equivalent Dynamic Load p = 3 for STEEL Ball bearings

The Traditional L₁₀ Calculation May NOT Apply to Hybrid Bearings

Theoretical L₁₀ Life calculations are fundamentally based on statistical Weibull plots of steel bearings. Applying this empirically derived equation to hybrid bearings can result in misleading analysis because the equation does not account for the effects of dissimilar material and lower operating temperature on bearing life. While the traditional L₁₀ equation will predict a decreased life for hybrid ceramic bearings, application case studies show that hybrid bearings tend to significantly out last steel bearing in field operations.

Given that silicon nitride balls are 50% stiffer than steel, the contact stresses are increased in the raceway. Due to this condition, the theoretical L₁₀ life of a hybrid bearing must be re-calculated and is typically ~20% lower than steel. Howerver, changing the race curvatures is often designed into hybrid bearings to compensate for the increased ball stiffness and increased the load capacity. Additionally, changing the number of balls in the bearing can also effect the overall load capability of the bearing. Finally, the performance of a hybrid ceramic bearing will vary with the quality of material and finishing used to make the ball. Like all materials, higher quality and robustness tends to improve the end product and its capabilities.