Velocity field is a vector to measure the flow of material in the process of plastic deformation. Through the observation of material flow direction and velocity, the flow law of material can be found and the filling effect of material can be predicted.
The figure shows the distribution of velocity field at different times in the final forging process. The direction of the arrow indicates the direction of metal flow, and the size of flow velocity is represented by different colors, as shown in figures (a) and (b). At the initial stage of deformation, the upper end face of the blank contacts the upper die and flows downward along the moving direction of the upper die under the pressure of the upper die. At the same time, the outer contour part of the lower end face of the blank contacts the tooth top of the lower die and flows along the tooth profile of the die to gradually form the tooth root of the forging, as shown in figure (c). As the upper die moves down, the inner contour part of the lower end face of the blank gradually contacts with the tooth shape of the lower die and is extruded by the die. Axial upsetting deformation occurs in the cavity, so that the radial dimension of the part is gradually consistent with the cavity. At the same time, under the action of the die tooth shape, the material gradually fills the tooth cavity, This process continues until the material basically fills the cavity, as shown in figure (d). In the final stage of forming, the material flow is mainly concentrated in the tooth top and inner and outer flash of the tooth shape. The flow velocity at the tooth top and outer flash of the small end of the tooth shape is large, which can quickly fill the tooth shape and form flash. These positions of the forging are filled and formed at the end. In the whole forming process, the material has both axial flow and radial flow, and the material in the tooth shape also has tangential flow under the influence of the tooth shape direction of.