THE INFLUENCE OF ECAP GEOMETRY ON THE EFFECTIVE STRAIN DISTRIBUTION

摘要

Equal channel angular pressing (ECAP) is one of the most well-known severe plastic deformation (SPD) method for formation the UFG (ultrafine-grained) structures. This method provides very high strains leading to the extreme work hardening and microstructural refinement. To increase the efficiency of ECAP method, there is necessary to design the geometry of ECAP die with focus on high degree of plastic deformation homogeneity. The present study deals with the influence of channel angle on the deformation behavior and strain homogeneity in the transverse direction of sample after two ECAP passes. This analysis was carried out through finite element simulations in the Deform program. In the simulation, three main factors such as an intersecting angle of Ф = 90°,100°, 110° a 120°, outer corner angle R (ψ) and inner corner angle (r) were being varied. The equation describing the dependence of R and r on average value of the effective plastic strain for different channel angles was established. Moreover, strain inhomogeneity index (Ci) in the transverse direction of sample was also calculated. The results from simulations have indicated that if the outer corner angle increases, mean effective strain decreases. After two ECAP passes (route C), there was seen the increase in strain homogeneity of the sample's cross section.