Axi-symmetric tube extrusion/piercing using die-mandrel combinations: someexperiments and a generalised upper bound analysis

A generalised upper bound technique is applied to the solution of working p ressures in extrusion-piercing of hollow tubes starting from either solid c ircular or initially hollow billets by using axi-symmetric die-mandrel comb inations of different shapes. Characteristic deformation modes during proce ssing of these tubes made of tellurium lead and commercially pure aluminium were studied experimentally and the results presented. Estimates of workin g pressures based on the generalised upper bound analysis are compared with the experimental and with those estimated earlier from the slab method of analysis given in Chitkara and Aleem (International Journal of Mechanical S ciences, submitted for publication). These show good co-relations with each other and with the experiments. (C) 2001 Elsevier Science Ltd. All rights reserved.