American Standard ANSI / agma2001 is adopted to calculate the required contact strength, and the calculation formula is as follows:

Because the contact stress of the gear under the load spectrum is calculated, SH = 1 and Zn = 1 are selected. According to the standard S-N curve, the modified S-N curve of the gear can be obtained, as shown in Figure 1.

Because the temperature coefficient, reliability coefficient and tooth surface condition coefficient are all 1, the S-N curve obtained is consistent with the standard S-N curve.

ANSI / AGMA 2001-d04 tooth contact stress calculation formula is as follows:

The contact stress and life under various working conditions can be obtained by calculation. The S-N curve of life under various working conditions is shown in Figure 2.

From the calculation of American Standard gear life, the same conclusion can be drawn that the instantaneous peak load will cause a great reduction of contact life.