Presetting for improving spur gear teeth bending fatigue life

Compressive residual stresses are widely accepted as a prime deterrent to fatigue failure. The use of presetting was explored as a means of inducing compressive residual stresses in the spur gear tooth fillet region to increase resistance to bending fatigue. A single tooth gear bending fatigue test fixture was constructed and calibrated. Residual stress and permanent gear tooth tip deflection were predicted using an elastic-plastic finite element analysis. Compressive residual stresses 58% of the yield strength and permanent tooth tip deflection within that allowed by the AGMA quality number of 12 were predicted. High cycle fatigue tests were conducted and fatigue lives were increased by an average of 673% for a low cyclic stress case and 97% for a high cyclic stress case.