When the gear rotates in the forward direction, the concave surface of the small wheel drives the convex surface of the big wheel to rotate, and the two surfaces contact. The big end and small end of the big wheel are meshed in, and the small end is meshed out. The contact stress nephogram of the convex surface of the big wheel is obtained as shown in Fig. 1; when the gear rotates in reverse direction, the convex surface of the small wheel drives the concave surface of the big wheel to rotate, and the contact stress nephogram of the concave surface of the big wheel is obtained, as shown in Fig. 2 The stress unit in the figure is kPa. As can be seen from the figure, this is the same direction and similar shape as the result obtained in MATLAB before.

In TCA calculation, two kinds of tooth contact simulation analysis methods based on numerical iteration are put forward successively. The instantaneous contact ellipse can be searched without complicated curvature calculation, and the contact ellipse boundary, instantaneous contact line and contact mark of the whole tooth surface can be obtained accurately. The method is verified by ABAQUS software.