Effects of Addendum Modification on Bending Fatigue Strength of Spur Gears : 3rd Report, Cast Iron and Cast Steel Gears

Abstract

This paper presents a study on the effects of addendum modification on bending fatigue strength of spur gears of cast iron and cast steel. Analysis is made regarding the effects of addendum modification on the true stresses at the fillet in connection with the worst loading point and also on the bending fatigue strength of gear teeth. Bending fatigue strength of cast iron and cast steel gears can be improved by selecting the proper amount of addendum modification. Addendum modification factor B_χ for bending strength is derived from the analytical and experimental results, and the bending fatigue strength of profile shifted gears can be estimated with fairly high accuracy by introducing this factor into the strength design of gears. Furthermore the effects of addendum modification on both the contact ratio and the contact ratio factor are also discussed.