Multi-Scale Modeling of Anisotropic Polycrystalline

Polycrystalline microstructure often plays an important role in determining the macroscopic behavior of metals. This work is motivated by the case of a spin-formed shaped charge liner. When these liners are compressed and inverted by detonation of an explosive charge, the resulting jet of material exhibits a distinct rotation. There is no asymmetry at the macroscopic level that would suggest a source of this rotation, and it is in fact a result of microstructurally-induced plastic anisotropy. Procedures are outlined for calculating this anisotropy using orientation imaging microscopy (OIM) and multi-scale modeling techniques. OIM observations are used to create a statistical characterization of the shaped charge liner's microstructure consisting of its polycrystalline texture (grain orientations) and neighbor correlation, a construct meant to capture the spatial arrangement of grains and grain boundary character. These statistics are used to generate a 3D representative volume element consisting of many discrete grains and respective orientations. The deformation of this representative aggregate is simulated using crystal plasticity within each grain. The results of these simulations are used to fit the parameters of an anisotropic yield function that can be used in macro-scale continuum simulations employing anisotropic plasticity. Prototypical macro-scale simulations were performed, and the results exhibit the expected rotation. Thesis Supervisor: David M. Parks Title: Professor of Mechanical Engineering