Constitutive modelling of extrusion of lead with cyclic torsion

The cyclic rotation of a circular die during the extrusion of lead bars results in a complex load–displacement behaviour. The average load under these conditions is significantly (up to 25%) lower than for simple extrusion with no die rotation. The data was used to successfully develop an empirical constitutive model. The main features include an increase in the extrusion load when the die undergoes a reversal in the twisting direction. This transient behaviour is then followed by a practically constant reduced extrusion force.