A root bending stress and surface stress comparison between Coniflex Pro cut and forged gears was performed with the ANSYS Finite Element Method. The Coniflex Pro differential gear set was designed to replace the originally forged version. Also, a model of the side gear spline was created, and the input torque was transmitted from the splined shaft via the internal spline in the side gear bore to the side gear teeth. A torque of 1,000 Nm, which reflects the duty cycle peaks of a midsize EV, was applied. The bending stress results to the left in Figure 8 show a considerable advantage of the cut side gear (i.e., the cut pair). It is noticeable by the red patch inside of the web area at the toe that the web restricts the necessary tooth deflection in this critical area, resulting in twice the bending stress of the cut gear. The high load contact area in the right-side graphics (red) fades out smoothly on the Coniflex Pro cut gear but extends to tip and root on the forged version. This proves the advantageous function of the Coniflex Pro tip relief. Also, the contact stress magnitudes in Figure 8 show up to 65 percent higher values of the forged gear. The especially the high value of 3,753N/mm2 in connection with the high bending stress in the same area will result in high sub surface stresses which can cause case crushing. Case crushing often leads to flank fracture.

Also, an interesting result is the lower load sharing with neighboring tooth pairs of the forged gear set which reduces the effective contact ratio. In Figure 9, a comparison of the load sharing for the Coniflex Pro cut differential gear set (bottom graphic) with its forged predecessor (top graphic) is presented. The green graphs in Figure 9 have their maximum at the center of three consecutive tooth pairs. The periodic shape of the graphs represents in the ordinate direction the contribution of load transmission of this particular pair of teeth in the current roll position (pitch position). The blue and the red graphs represent the two tooth pairs neighboring the tooth pair represented by the green graph. A vertical line in the upper diagram (at the center of the graphic) intersects the green graph at 80 percent and the red and blue graphs at 10 percent. This means that 80 percent of the input torque is transmitted by one pair of teeth. In the current example, the forged gear set has an effective contact ratio of 1:1 which means that on average 1:1 tooth pairs transmit the input torque at all times. A vertical line at the center of the lower diagram in Figure 9 (Coniflex Pro) intersects with the red and blue graphs at the 20 percent mark and with the green graph at the 60 percent mark. This means the maximal load the teeth have to transmit is 60 percent of the input torque because of the higher contribution of the neighboring tooth pairs. The effective contact ratio of the Coniflex Pro differential gear set in this example is 1:6.