Stress concentration of the gear tooth root fillet is an important factor to affect the bending fatigue strength of the gear.In order to improve the bending fatigue strength

the stress relief hole in the tooth surface is established to make root stress redistributing to reduce root bending tensile stress.The two-dimensional finite element is used to calculate the best radius and location of the circular hole.The three-dimensional finite element model is established to validate the result and to calculate contact stress

and the bending fatigue limit is also analyzed.The results show that

for selected parameters gear

tooth surface with hole can make the tooth root stress redistributing to reduce tooth root bending tensile stress

the bending fatigue life of the gear is greatly improved and the weight of the gear is reduced.The reduction of the stress has agreat relationship with the location and size of the hole and there is a best size and position.Different gear parameters can also cause the hole best location and size changed

and the tooth root stress decreases a little can greatly improve the bending fatigue life a lot.