Gear-tooth Stresses at High Speed

By W. A. Tuplin, D.Sc., hU.Mech.E.*
If the maximum stress in a gear tooth is less than the fatigue limit for the material, the tooth should
not fail even after indefinitely prolonged running. Fatigue data collected in the conventional way
suggest that the number of stress cycles required to cause failure of a given material under any
particular stress is independent of the time-rate of repetition of stress. It should therefore be permissible
to stress any gear, regardless of its speed, up to the fatigue limit for its material, although
this suggestion may need modification because of the difference between the impulsive nature of the
application of load to a gear, and the more gradual fluctuation of stress in a fatigue-test specimen of
the Wohler type.