Gear tooth modification can reduce the stress concentration at the edges of the gear tooth and improve the fatigue life of gear.The logarithmical modification curve is first applied on helical gears

and the contact analysis mechanical model of helical gear is established.The distributions of contact stress and Mises stress field inside subsurface layer at single and double meshing state are obtained.The results show that the level of stress concentration changes with the meshing position of the gear tooth

and that the stress concentration of the contact stress and the Mises stress inside subsurface at the tooth ends are improved through the logarithmical modification

and that the modification amount of different contact lines varies with meshing positions to achieve the same modification effect.