Direct upper bound solution to rectangular-to-polygonal extrusion through square die

This paper is concerned with an attempt to find an upper bound solution for the problems of steady-state extrusion of asymmetric polygonal section bar s through rough square dies. A class of kinematically admissible velocity f ields is examined, reformulating the SERR technique, to get the velocity fi eld that gives the lowest upper bound. This velocity field is utilized to c ompute the non-dimensional average extrusion pressure at various area reduc tions for different biller aspect ratios.