Fundamentals of Shaft and Bearing Design
Designing a power transmission shaft requires ensuring that the mechanical component can safely transmit torque while supporting transverse loads (such as those from gears, pulleys, or sprockets) without experiencing permanent deformation, excessive vibration, or fatigue failure.
Equivalent Stress and Failure Theories
Shafts are typically subjected to multiaxial loading states: torsion from power transmission and bending from transverse loads. To evaluate the safety of the shaft, engineers use the Von Mises Equivalent Stress, which combines normal and shear stresses into a single value that can be directly compared against the material's yield strength to find the Safety Factor (FS).
Deflection and Bearing Life
Even if a shaft is structurally safe against yielding, excessive Deflection can cause gear misalignment and rapid bearing wear. Simultaneously, the bearings supporting the shaft must be evaluated for fatigue. L10 Bearing Life predicts the operational hours before 10% of a sample group of bearings show signs of fatigue spalling, heavily dependent on the operational RPM and the ratio of the dynamic load rating to the applied equivalent load.