Dynamic behaviour of polycrystalline tantalum

• Published in: International journal of plasticity Vol. 14; no. 9; pp. 871 - 890
• Main Author: Schoenfeld, Scott E.
• Format: Journal Article
• Language: English
• Published: Elsevier Ltd 01.01.1998
• ISSN: 0749-6419; 1879-2154
• DOI: 10.1016/S0749-6419(98)00034-5

A description for the strain-rate and temperature-dependent behavior of pure tantalum (Ta) at large strains is developed. An integral part of the model incorporates the kinematics of crystallographic slip, and thus, the rotation of single crystals within the material, so as to reflect the evolution of anisotropy resulting from applied mechanical deformation. Such deformation is accommodated via bulk dislocation motion and governed by interactions that may or may not be thermally assisted. The model represents each discrete slip system as a single facet in a multisurface plasticity theory which is well suited to high-rate numerical methods (explicit integration schemes). A formulation of this type allows for the complete kinematic decomposition of macroscopic material rotations and the rotations of single crystals due to motion through the lattice. Applications to high-rate deformation in polycrystals is conducted within a finite element implementation by invoking a Taylor criterion for interaction between the macroscopic and the mesoscopic (single-crystal) length scales. The model behavior is examined in application to high-rate problems with increasingly complex geometries (homogeneous uniaxial compression, the impact of a textured cylindrical bar into a rigid anvil, and the explosive deep-drawing of a Ta disk). The final example compares through-thickness deformation in the Ta disk as a function of initial texture and, therefore, emphasizes the profound effects of plastic anisotropy during finite deformation.