Plane strain extrusion by sequential limit analysis

In this paper, the analysis of plane strain forward extrusion through wedge shaped dies is implemented by using a finite element procedure based on a dual (upper bound) formulation. Since the von Mises yield criterion is employed and expressed in an inequality form, stresses do not appear in this upper bound formulation. As a result, neither complicated stress updating nor rigid zone treatment is needed in this approach. The effect of material strain hardening can be incorporated in the analysis by updating local yield stresses stepwise with deformation history. The computed results are first compared with existing analytical solutions in good agreement. Effects of friction, die semiangle, height reduction ratio and material strain hardening on the extrusion load of aluminum are then investigated.