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

Abstract

Abstract 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 Perez 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, e ¯ p , and temperature along the workpiece and also to validate the proposed analytical solutions. By using Drucker's criterion, theoretical analyses showed that the decreasing of the sample temperature increment, Δ T , was primarily affected by higher values of die channels intersection angle, Φ , and moderately for its initial temperature and the tooling outer fillet radius, R outer . Also, the increasing of Δ T was more sensible for greater die inner fillet radii, R inner , and superior velocities, V 0 . In addition, the force dropped for elevated sample initial temperatures. For Φ = 90°, the finite-element models confirmed the decreasing of Δ T and P for 0 mm ≤ R outer ≤ 5 mm and their increasing for 10 mm/s ≤ V 0 ≤ 20 mm/s. Lastly, by comparing the numerical and theoretical results of P , e ¯ p and Δ T , the proposed solutions could be validated.