The bending fatigue life of tractor gear is closely related to the selection of gear modulus, which can be selected according to the special empirical formula or the accumulated experience. For shift gears, bending fatigue damage will cause serious failure, so generally in the design, bending fatigue life is designed according to infinite life. There are specific design methods in American Standard ANSI / agma2001-d04 and international standard ISO / TS 6336-2, which will not be repeated here. This paper focuses on contact fatigue life.

The contact fatigue strength has a great relationship with the selection of center distance. According to the experience, a gear of a 150 HP gearbox is selected as the analysis object. The basic application conditions of tractor transmission gear are selected according to the conventional method, the temperature is 70 ℃, the lubricating oil is iso-vg220, and the lubrication method is splash lubrication.

The working condition of the tractor is complex, but the 150HP tractor is mainly ploughing. It needs to be designed according to the maximum load, and the influence of the limit load is considered, so the design load spectrum of the gear is selected.