Enhancement of plastic flow in lateral direction by torsional oscillation in upsetting and lateral extrusion

Abstract

Plastic flow of hollow cylinders under combining axial compression with torsion was examined in upsetting and in lateral extrusion. The hollow cylinders with initial height/outer diameter of 0.5–2.5 and initial inner/outer diameter of 0.3–0.9 were compressed/extruded and simultaneously twisted with respect to the axisymmetric forging axis in one-way or cyclic alternating. Due to superposition of torsional shear stress, the lateral metal flow was found to be assisted. Barreling of the workpiece was reduced by approximately 10 % in upsetting with torsion/compression speed of 6 °/mm. The enhancement of the plastic flow in upsetting was applied to fill up tooth cavity in lateral extrusion. The extruded tooth depth of the workpiece was approximately 5–7% larger in lateral extrusion with torsion/extrusion speed of 30°/mm. In addition, cyclic alternating torsion was effective to extrude evenly in the tooth thickness direction due to the periodic reversal of die rotation in peripheral direction.