AN ANALYSIS OF BACKWARD EXTRUSION OF INTERNALLY CIRCULAR-SHAPED TUBES FROM ARBITRARILY-SHAPED BILLETS BY THE UPPER-BOUND METHOD

Abstract

A simple kinematically admissible velocity field for the backward extrusion of internally circular-shaped tubes from arbitrarily-shaped billets is proposed. From the proposed velocity field, the upper-bound extrusion load and the-average extruded height for regular polygonal-shaped billets and rounded rectangular-shaped billets are determined with respect to chosen parameters. Experiments are carried out with full-annealed commercial aluminum alloy billets at room temperature using four circular-shaped punches. The theoretical predictions of extrusion load are in good agreement with the experimental results. There is also reasonable agreement in average extruded height between theory and experiment.