The effect of deformations passes on the extrusion pressure in axi-symmetric equal channel angular extrusion

The most applicable configuration of the equal channel angular extrusion (ECAE) dies is the axi-symmetric one. However, most of the previous analytical solutions are focused on the plane strain conditions. In this research, an upper bound model is used to investigate the deformation of the material during axi-symmetric ECAE. The analysis considers the effect of die angle, friction between the sample and the die walls, and the angle of the outer curved corner of the die, on the extrusion pressure. It is found that increasing the die angle and outer curved corner angle and decreasing the friction coefficient results in decreasing extrusion pressure. The proposed model is verified using two dies of the same die angle and different outer curved corner angles. The applicability of the solution in the ECAE process with more than one pass is investigated and the difference between the theoretical and experimental results are discussed.