Upper-bound and finite-element analyses of non-isothermal ECAP

In this paper, the thermomechanical properties of pure tantalum described by Liang and Khan [Int. J. Plast. 15 (1999) 963] through Johnson–Cook hardening law were used to propose a non-isothermal solution for estimating the temperature increasing during single-pass equal channel angular pressed metallic materials. The pressing force was determined with the upper-bound models developed by Pérez and Luri [Mech. Mater. 40 (2008) 617] extended for elastic-plastic materials with the isotropic criteria of von Mises and Drucker. The von Mises plane-strain finite-element models were done with the program ABAQUS/Explicit to provide the pressing force, P, effective plastic strain, ε ¯ p , and temperature along the workpiece and also to validate the proposed analytical solutions. By using Druckerʹs criterion, theoretical analyses showed that the decreasing of the sample temperature increment, ΔT, was primarily affected by higher values of die channels intersection angle, Φ, and moderately for its initial temperature and the tooling outer fillet radius, Router. Also, the increasing of ΔT was more sensible for greater die inner fillet radii, Rinner, and superior velocities, V0. In addition, the force dropped for elevated sample initial temperatures. For Φ = 90°, the finite-element models confirmed the decreasing of ΔT and P for 0 mm ≤ Router ≤ 5 mm and their increasing for 10 mm/s ≤ V0 ≤ 20 mm/s. Lastly, by comparing the numerical and theoretical results of P, ε ¯ p and ΔT, the proposed solutions could be validated.