Effects of Addendum Modification on Bending Fatigue Strength of Spur Gears : 1st Report, Normalized Steel Gears

Abstract

This paper presents a study into the effect of addendum modification on bending fatigue strength of spur gears made of normalized steel. Theoretical analysis is made regarding the effect of addendum modification on the true stresses at the root fillet of gear tooth in the case of tip loading. Bending fatigue tests are performed on gears with various amounts of addendum modification, using a pulsator of hydraulic type. The value of root stress factor for calculating true stresses at root fillet increases with an increasing value of addendum modification coefficient and the bending fatigue strength of normalized steel gears can be improved significantly by selecting the proper amount of addendum modification. Furthermore, addendum modification factor B_x for bending strength is derived on the basis of the analytical and experimental results.