# Study on crack propagation law of heavy duty gear under different initial crack positions

Study the crack propagation law when the initial crack position H0 is 60mm, 62mm, 64mm, 66mm, 68mm and 70mm respectively, and set the initial crack angle α It is 30 °, and the initial crack length is 6mm.

As shown in the figure, when the propagation trajectory curves are 5 and 6, H0 is 68mm and 70mm. The propagation trajectories of the two cases are relatively similar. The initial cracks appear closer to the tooth root. The propagation trend of the crack in the early stage is towards the gear rim, and the change trend of the crack propagation in the later stage is similar, which is that the propagation trajectory of the crack is relatively smooth, Gradually level. The propagation trajectory curves of 60mm, 62mm, 64mm and 66mm are 1, 2, 3 and 4 respectively. Their propagation trajectories are similar. The crack propagation trend in the early stage is towards the gear rim, while the crack propagation trend in the later stage is towards the root.

Based on the above situation, the early change law of crack propagation in the six cases is the same, as shown in the figure, both show the trend of extending towards the rim, and the six cases are different in the later stage. Therefore, the initial position of the crack is the most significant factor affecting the crack propagation trajectory. It can be seen from the figure that the smaller the crack is, the closer the initial position of the crack is to the tooth top, and in the later stage, the direction of the crack propagation trajectory gradually faces the tip of the tooth.

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