Elastic-Viscoplastic an Isotropic Modeling of Textured Metals and Validation using the Taylor Cylinder Impact Text
AIR FORCE RESEARCH LAB EGLIN AFB FL MUNITIONS DIRECTORATE
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An elastic-viscoplastic model for describing the anisotropic high-strain rate behavior of both low-symmetry and high symmetry textured materials is proposed. Yielding is described using a recently developed criterion which can capture simultaneously anisotropy and compression-tension asymmetry associated with deformation twinning. The anisotropy coefficients as well as the size of the elastic domain are considered to be functions of the accumulated plastic strain. The specific expressions for the evolution laws are determined using a multi-scale methodology, i.e. experimental measurements of crystallographic texture and uniaxial stressstrain curves, poly-crystalline calculations, and macroscopic scale interpolation techniques. An over stress approach is used to incorporate rate effects in the formulation. Applications of the model to the description of the high strain-rate response of low-symmetry hexagonal-close-packed zirconium and high-symmetry body-centered-cubic tantalum pre-textured metals are presented. The very good agreement between the simulated and experimental post-test geometries of the Taylor impact specimens in terms of major and minor side profiles and impact interface foot prints shows the ability of the model to describe with fidelity the differences in the evolution of an isotropy between zirconium and tantalum.
- Metallurgy and Metallography