ELASTOVISCOPLASTIC CONSTITUTIVE-EQUATIONS FOR POLYCRYSTALLINE METALS - APPLICATIONS TO TANTALUM

Strain-rate and temperature-dependent constitutive equations for polyc rystalline metals which are capable of modeling the initial and evolvi ng anisotropy in ductile metallic materials owing to the evolution of crystallographic texture are reviewed and then specialized to reproduc e the recently published stress-strain response of commercially pure b .c.c. tantalum for strains up to 60%, al strain rates from quasi-stati c to 30,000 s(-1), and temperatures from -200 to 525 degrees C (Hoge a nd Mukherjee, 1977; Vecchio, 1994; Nemat-Nasser and Isaacs, 1996). The constitutive equations have been implemented in a finite element prog ram, and the computational capability is used to simulate the evolutio n of crystallographic texture in simple compression, plane-strain comp ression, and torsion under quasi-static conditions. A comparison of th e predictions against corresponding experiments shows that the crystal plasticity-based model predicts the texture evolution and the macrosc opic stress-strain curves satisfactorily. The computational capability is also used to simulate the dynamic Taylor rod-impact tests performe d by Ting (1992) on pre-textured tantalum cylinders. The numerical sim ulations reasonably reproduce the final length and the ovalized macros copic shape of the impact end of the cylinders observed in the experim ents. (C) 1997 Elsevier Science Ltd. All rights reserved.