A modified kinematically admissible velocity field for the backward extrusion of internally circular-shaped tubes from arbitrarily shaped billets is proposed. The original velocity fields appearing in the literature did not satisfy the condition that the normal velocity on the die and material interface must be zero, and material rotation under the punch was neglected. Therefore, in this work the former is corrected and the latter is improved by a new velocity field. From the proposed velocity field, the upper-bound extrusion load and average extruded height for regular polygonal-shaped billets are determined with respect to the chosen parameters. The theoretical predictions of extrusion load in this paper are lower and closer to the experimental results than those in the previous literature. The average extruded height and the grid distortion of theory and experiment agree well when using the proposed velocity field.
All Science Journal Classification (ASJC) codes
- Ceramics and Composites
- Computer Science Applications
- Metals and Alloys
- Industrial and Manufacturing Engineering