The study is concerned with an analysis on the forward extrusion of composite tubes through curved dies with generlized elastic-plastic boundaries.
A kinematically admissible velosity field is derived by assuming proper stream lines and applying the flow function concept to each material region of plastic deformation. In the analysis, the elastic-plastic boundaries are permitted to be of generlized shape so that better upper-bound is obtained. The effect of work-hardening is incorporated approximately by calculating the strains at the exits of both materials. The flat elastic-plastic boundaries of Prakash and Juneja is found to be a special case of the present analysis.
The upper-bound extrusion pressures are computed, for various process variables such as reduction of area, semi-cone angle, ratio of thickness.
The experiments are carried out with commercially pure aluminum and copper billets for some chosen process variables at the room temperature. Then the experimental observations are compared with the theoretical calculations. The comparison shows that the theoretical predictions both in extrusion load and in flow pattern are in reasonably good agreement with the experimental observation.