Prediction of Deformation Mode of Bi-Metallic Rod Extrusion through Arbitrarily Curved Dies

The modes of deformation of bi-metal rods during forward extrusion through arbitrarily curved dies are studied in this paper. An analytical solution is developed to predict the mode of deformation by using the upper bound method. The effects of the yield stress ratio, shape and length of the die, extrusion ratio and frictional shear factors at the interface and the die surface are considered in the analysis. It is found that frictional shear factor at the interface, the ratio of flow stresses and die length are important parameters that can change mode of deformation from uniform deformation to cladding-type. Shape of the die, reduction in area and frictional shear factor at the die surface have not effect on the mode of deformation, although the effects are great on the extrusion pressure. The extrusion process is also simulated by using the finite element code, ABAQUS. The theoretical results show good agreement with the FEM results.