Constitutive Modeling of Polycrystalline Metals at Large Strains

In polycrystalline metals the major cause of the anisotropic plastic response is crystallographic texture resulting from the reorientation of the crystal lattices of grains during deformation. There have been considerable recent advances in the understanding of anisotropy due to crystallographic texturing, and a reasonably successful, physically-based elasto-viscoplasticity theory for the deformation of face- and bodycentered-cubic polycrystals deforming by crystallographic slip is now at hand. The constitutive equations in the theory are reviewed, and the implementation of these equations in a finite element program is described. The theory is able to predict the macroscopic anisotropic stress-strain response, shape changes and the evolution of crystallographic texture in complex deformation modes. Also, it is beginning to be applied to the analysis of deformation-processing problems. Applications to (i) the prediction of earing defects during quasi-static cup-drawing of an f.c.c. aluminum alloy, and (ii) the ovalization of pre-textured b.c.c. tantalum cylinders during dynamic Taylor cylinder-impact experiments are described.

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