Predicting fatigue crack growth life for cold-worked holes based on existing closed-form residual stress models

The failure of hardened, high performance gearing normally occurs through a process of fatigue and is usually attributed to a combination of the material properties along with gear design and mechanical misalignment. Recent work has shown that a very effective method of controlling fatigue performance is through the careful use of residual stresses. This paper concentrates on how residual stress variations can greatly influence the bending fatigue performance measured on carburised gears. The results from the work show that careful control of residual stress, through shot peening, can give up to a 75% increase in fatigue strength through the introduction of high compressive residual stresses.