A kinematically admissible velocity field for three-dimensional extrusion is proposed and upper-bound solutions for the extrusion pressure in hydrofilm condition are predicted in order to compare with the experimental results.
The variables like axial velocity or effective strain derived from the velocity field are assumed to vary with not only axial direction but also circumferential direction.
It is found that the obtained velocity field is applicable in predicting extrusion pressures and in designing die profiles of arbitrary exit shapes.
A CAD/CAM system is used for manufacturing the complex three-dimensional extrusion dies. Experiment are carried out for rectangular shapes with lead and for twisted elliptic shapes with aluminum and steel. The experimental results are in good agreement with the theoretically predicted extrusion pressures for rectangular shapes, but a little difference is found in the case of twisted elliptic shapes.
