An investigation into the plastic deformation behavior within a conical die during composite rod extrusion

This paper proposes a set of stream functions to investigate the plastic deformation behavior of the rods during the axisymmetric extrusion of composite rods through a conical die. The velocity field and the rigid–plastic boundaries can be obtained immediately from the proposed stream functions. Relative slip at the interface of the rods is allowed. The friction factor between the rod and the die is determined by a ring compression test. By using the upper-bound approach, the radius ratio of the core layer at the exit of the die and the plastic region within the die are determined by the minimization of the total power. Experiments on the extrusion of composite rods composed of aluminum (the core layer) and copper (the sleeve layer) are also carried out. The predicted force, final radius ratio and flow pattern of the rods within the die are compared with the experimental results.