Extrusion of axi-symmetric bi-metallic tubes from solid circular billets: application of a generalised upper bound analysis and some experiments

The generalised upper bound technique previously applied to the determinati on of working pressures in extrusion-piercing of solid billets (Chitkara NR , Aleem A. Int J Mech Sci 2001;43:1685-709.) to form hollow monometallic tu bes is extended to analyse the problem of bi-metallic tube extrusions throu gh profile shaped dies and mandrel combinations. Theoretical results of mea n extrusion pressures obtained from the generalised upper bound analysis ar e compared with those obtained earlier by the generalised slab method of an alysis (Chitkara NR, Aleem A. Int J Mech Sci 2001,43:2857-82.) and some exp eriments. A few salient observations made during the experimental investiga tions carried out into forward extrusion of bi-metallic tubes made of h.c. copper and c.p. aluminium are also given and the results commented upon. (C ) 2001 Elsevier Science Ltd. All rights reserved.