ANALYSIS OF CENTER-SHIFTED BACKWARD EXTRUSION OF ECCENTRIC TUBES USING ROUND PUNCHES

Abstract

An analytical method is proposed for analyzing center-shifted backward extrusion (or piercing) of eccentric tubes from circular billets. A kinematically admissible velocity field is derived to formulate an upper-bound solution using the velocity-transformed central-flow model. The configuration of the deforming boundary surfaces is determined by minimizing the extrusion power with respect to some chosen parameters. Two kinds of functions describing the deformation boundary are compared and discussed. Aluminum is used as the working material in the experiments and the work-hardening effect is taken into consideration. The computed results are compared with the experimental results for different center-shift values (eccentricity) of the punch. It is shown that the theoretical predictions for extrusion load give good upper-bounds when compared with the experimental results.