الفهرس 
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Abstract
Equal channel angular pressing (ECAP) is one of the promising severe plastic
deformation (SPD) techniques which produce ultra-fine grains in bulk materials. The ECAP deformation process induces high plastic strain in bulk material by uniform simple shear thus developing ultra-fine grained materials which have been widely investigated due to their improved mechanical properties such as high strength and
ductility. In ECAP, a billet is pressed through a die that consists of two equal cross sectional channels intersecting at an angle of (q;) and with an outer corner angle of
(1fJ).
In order to design the die and choose optimal parameters for the process, it is important to understand the effect of die geometry and processing variables. In this
regard different analytical models have been developed. To overcome the limitations of these models and to get more detailed information about the process, finite element method (FEM) has been used which can serve as a guide for analytical models. In this
study, commercial [mite element code AbaquslExplicit was used to study the
influence of channel angle, corner angle and friction on the deformation behavior, strain homogeneity, punch load and damage or fracture tendency. The simulations were carried out with channel angles range from 75° to 150°, corner angles range from 0° to 90° and friction coefficients range from 0 to 0.3.
from the analysis of deformation behavior, it was found that the acute and right channel angles are preferred than the other obtuse angles. Smaller corner angles maximize the homogeneous portion of the billet and friction reduces the corner gap significantly. The results showed that the optimal parameters to satisfy the maximum
homogeneity and minimum damage level corresponds to channel angle tp = 90°,
corner angle ljJ = 15° and friction coefficient f1 = 0.3. Punch load is greatly affected by friction in which the load is doubled in case of friction coefficient equal to 0.2 with
respect to frictionless case.