The effect of dead metal zone formation on strain and extrusion force during equal channel angular extrusion

In this research, deformation of material during equal channel angular extrusion (ECAE) is analyzed using an upper bound model. The model considers the effect of die angle and friction between the sample and the die walls on the geometry of dead metal zone and total strain. The relationship between the friction coefficient, the extent of dead metal zone and total strain is derived. It is found that strain decreases with increasing die angle and friction coefficient. Moreover, a critical value for friction coefficient is determined that when the friction coefficient is more than the critical, deformation zone and therefore, the dead metal zone forms which consequently total strain decreases. The theoretical results are compared with previously published theoretical and experimental calculations by the same authors. It is concluded that considering the effect of friction coefficient on total strain and extrusion force results in closer accord between the theoretical and experimental results. Using this method, the difference between the theoretical and experimental results has decreased from 8.9% to 5.6% when compared with the previous study. (C) 2007 Elsevier B.V. All rights reserved.