Take the following values for relevant parameters: Z H, and take 2 according to the tooth profile angle and helix angle of the normal surface 125； Ze, both spiral bevel gears are made of steel, taking 189 8； ZK, when the modification of tooth top and root is appropriate, take 0 85； Ka, according to the working characteristics of prime mover and working machine, it is slight impact, uniform and stable, and it is speed-up transmission, taking 1 21； K H β， In this paper, both wheels are supported at both ends and are used for aircraft and vehicles, taking 1 5； K H α， The accuracy grade of spiral bevel gear is 6, and the hard tooth surface is curved, take 1 1。 Because there are one random variable and two interval variables in the geometric parameters, the above six parameters in the calculation of contact stress change accordingly.
According to the stress interference model, the limit state function of spiral bevel gear can be simplified as:
