In order to study the effect of crack length on stress intensity factor and J-integral, the above semi elliptical initial crack was used to study. Only the length of three-dimensional initial crack was changed, taking 0.5 mm, 0.75 mm, 1 mm and 1.25 mm respectively, and the depth was 1 mm. Four groups of helical gear models with different three-dimensional initial crack were obtained. A torque of 500 N · m is applied to the driving wheel of the gear pair, and the stress intensity factor and J-integral value are calculated respectively.
It can be seen from Fig. 1 (a) and Fig. 1 (b) that with the increase of the crack length, the distribution of K1 and K2 at the crack front edge increases obviously in the middle region of the normalized crack front length; the curve still maintains the change trend of high middle low at both ends; and the middle of the curve is more and more stable. As shown in Fig. 1 (c), the distribution of K3 at the crack leading edge increases with the increase of the crack length at both ends, but decreases in the middle.
It can be seen from Figure 2 that the J-integral distribution law of the crack front edge, with the increase of the crack length, the crack increases obviously in the middle region of the normalized crack front length; the curve still keeps the change trend of high middle low at both ends; the middle of the curve is more and more stable. J-integral and K1 stress intensity factor have the same change rule.