Die design for homogeneous plastic deformation during equal channel angular pressing

It is well known that deformation during equal channel angular pressing (ECAP) is not as perfectly homogeneous as simple shear, although the inhomogeneity is not as distinct as the other metal forming processes. The sources of this inhomogeneity are (i) external conditions such as die geometries, loading modes, temperature, ram speed and die frictions and (ii) internal conditions such as material's strain hardenability and strain rate sensitivity. In spite of a lot of recent research results, factors and mechanisms of the inhomogeneous deformation were not elucidated systematically. In this paper, the effects of external and internal factors on the deformation inhomogeneity during ECAP are investigated. The finite element analyses of plastic deformation are employed for this purpose in conjunction with die corner angle and strain hardenability of metallic workpieces. Optimum die corner angles with strain hardening exponent are presented.