Swing rolling of spiral bevel gear is a processing method in which the blank is continuously and locally loaded by the conical upper die. Figure 1 shows the cloud diagram of equivalent stress and equivalent strain distribution of forgings at 40%, 70% and 100% reduction. The machining surface of the workpiece in the swing rolling process of spiral bevel gear can be divided into two parts: contact area active deformation area and non-contact area passive deformation area. As can be seen from Fig. 1, the contact area directly bears the pressure of the cone die to produce plastic deformation, the equal effect force and equal effect become larger, and the non-contact area also deforms to a certain extent due to the action of the active deformation area. When the reduction is 40%, the metal begins to fill the upper tooth cavity, while the lower blank has not been deformed. When the metal fills the tooth cavity, the friction between the die and the blank surface hinders the metal filling, and the stress and strain at the tooth root circle are large. The equivalent stress value is 250Mpa and the equivalent effect variation value is 1.20. When the reduction is 70%, the metal at the lower end of the blank begins to fill the tooth cavity. When the reduction is 100%, the tooth profile is completely filled, and the tooth top and the corner of the upper and lower teeth are filled. The maximum stress and strain values are about 320MPa and 2.0. The metal at the upper end of the blank deforms first and fills the tooth cavity. Because the conical pendulum head locally loads the blank along the axial direction, the metal at the contact surface first meets the yield condition and produces plastic deformation. With the gradual expansion of the stress area in the height direction, the absolute value of the axial stress gradually decreases. Therefore, the deformation area is mainly concentrated at the upper end of the blank, and the deformation area gradually shrinks downward along the axial direction.
Figure 2 shows the speed field distribution of spiral bevel gear swing rolling. Fig. (a) is the velocity field distribution of 15% reduction, and the tooth cavity has not been filled at this time; Figure (b) is the velocity field distribution diagram of 70% reduction. At this time, the upper tooth cavity has been filled, and the lower tooth cavity is only partially filled; Figure (c) shows the distribution of 95% reduction velocity field. At this time, most of the lower tooth cavity is also filled. The billet metal flow is mainly in the contact area, and the billet metal flow velocity in the non-contact area is very small and can be ignored. In addition to the axial downward flow, the metal in the contact area also flows radially and tangentially Under the action of axial downward stress, radial stress and tangential stress, the metal in the contact area fills the tooth cavity from top to bottom along the helix of the tooth. In the non-contact area, the metal flows upward in the axial direction. The blank velocity field is distributed along the helix of the gear teeth and will not intersect with each other, and the tooth top at the lower end of the final filling area is also completely filled. It can be seen that under the condition of reasonable parameter setting, the tooth cavity of spiral bevel gear can be completely filled, and the metal fiber is evenly distributed without metal folding defects.
Figure 3 shows the load stroke curve of swing rolling. With the progress of swing rolling, the tooth shape part is gradually formed, the load curve is gradually increased, the load is gradually increased, and the maximum load is 550kn. The amplitude of the load curve is very small, which shows that the swing rolling forming process of the spiral bevel gear can be realized.
Fig. 4 is the load stroke curve comparison diagram of spiral bevel gear swing rolling and die forging, and Fig. 4 is the load stroke curve comparison diagram of spiral bevel gear swing rolling and die forging. The process parameters and gear geometric dimensions of die forging are the same as those of swing rolling, and the final load of die forging is 4500kN. It can be seen that the load required for swing rolling is only 1 / 9 of that of die forging.
Fig. 5 shows the torque stroke curve of swing rolling. It can be seen from the figure that in the swing rolling of spiral bevel gear, its torque increases with the increase of stroke. At the beginning of the contact stage between the upper die and the blank, the torque increases rapidly, then the torque increases slowly, and at the last stage, the torque increases sharply. In the initial stage, the torque amplitude is large because the die is just in contact with the blank. In the second half of swing rolling of spiral bevel gear, its torque is relatively stable and its amplitude is small.