Fig. 1 shows the blank flow velocity field under different pressing amounts. The velocity field of helical gear die forging reflects the law of metal flow in the whole deformation process. Figure 1 (a) to (c) reflect the velocity field under different reduction.
Fig. 1 (a) shows the blank speed field when the reduction is 50%. At this time, the tooth shape begins to appear on the surface around the blank. The punch goes down, contacts with the blank and is in the upsetting stage to prepare for the next stress deformation. The punch contacts the upper surface of the blank and extrudes the blank downward, so that the blank metal flows downward, so the upper end of the blank has a certain velocity field; The lower end of the blank is limited by the female die, the metal flows into the tooth groove under the extrusion of the male die, and the tooth shape begins to appear. Since the blank does not produce much deformation at the tooth root circle, the velocity field is very small (8mm / s). The maximum speed is at the upper end face (15.2mm / s).
Fig. 1 (b) shows the blank speed field when the reduction is 75%. At this time, the basic profile of helical gear tooth profile has been forged. With the increasing reduction, the blank height decreases gradually, the radial size increases gradually, and the metal flowing into the cogging increases continuously. The downward flow of metal at the upper end of the blank is obvious, and the velocity field increases than at the beginning; The forming of the tooth profile is obvious, the deformation is large, and the velocity field increases. The speed at the tooth root reaches 18mm / s and the speed at the tooth top reaches 8mm / s.
Fig. 1 (c) shows the blank speed field when the reduction is 100%. At this time, the cylindrical helical gear is forged. The blank is no longer deformed, the metal flow everywhere stops, and the gear teeth are well formed. The metal flow into the cogging becomes slower, the deformation is smaller, the velocity field decreases, and the downward flow velocity of the metal at the upper end of the blank begins to slow down.
The strain distribution of the blank is a macroscopic characterization of the cumulative process of plastic deformation and the development process of plastic deformation. At the same time, it also represents the deformation of the cylindrical blank in the forging process of helical gear.
Fig. 2 shows the strain distribution of blank under different forging pressure.
Fig. 2 (a) shows the equivalent strain of the blank when the reduction is 50%. At this time, the blank has just begun to fill the tooth groove, the blank is in the upsetting stage, the blank is extruded by the punch, the strain is relatively small, there is no contact with the tooth shape of the die, and the strain changes little, which is 0.035; The strain at the root circle is relatively large, which is 0.6, because the metal begins to fill the tooth slot; The upper metal of the blank has not entered the die, so the strain is not very large, which is 0.08; The strain at the tooth top circle is also very small because the tooth shape just appears and the metal does not enter the tooth groove of the die.
Fig. 2 (b) shows the equal effect variation distribution of blank when the reduction is 75%. At this time, the tooth profile is basically formed. Except that a part of the blank has not entered the die and the strain is still very small, the other blanks in the die have been deformed to a certain extent. A small part of the blank at the tooth root circle has large deformation due to metal flowing into the tooth groove, which is 0.8; The strain value of the blank at the other tooth root circle and the tooth top circle is almost the same, which is 0.5; The deformation of the upper surface of the blank is relatively small and the strain value is relatively small due to contact with the punch. The deformation of the upper surface of the blank in contact with the punch is very small, forming a special circular low strain region.
Fig. 2 (c) shows the equal effect variation distribution of blank when the reduction is 100%. At this time, the tooth shape is completely filled, there is basically no deformation, and the strain value decreases slowly. However, there are longitudinal flying spikes on the upper surface of the formed helical gear forging, so there is still visible strain at the upper end of the helical gear forging, the strain value is larger than the rest of the helical gear forging, and there is a circular low strain area on the upper surface of the helical gear forging in contact with the punch.