An analysis of plastic deformation processes for twist-assisted upset forging of cylindrical billets

Abstract

An investigation has been performed into the effect of the die and deformation pattern on twist-assisted upset forging. Rotation of the lower flat die accompanied by axial compression of the punch plays a distinct role in saving axial force. In this study, an upper bound analysis considering bulge formation, finite element method simulations (DEFORM 3D) and experimental research were carried out. A simple kinematically admissible velocity field for three-dimensional deformation is presented for twist-assisted upset forging of a cylindrical billet. An analytical expression for the upset force and torque is obtained from several process parameters. An increase in the friction factor and rotation speed was found to favour decreases in the magnitude of the upset force, dead metal zone and non-homogeneous deformation. Plasticine model experiments were performed where the lower die was rotated against the workpiece using a 5 ton model press.