SUBJECT: Ph.D. Dissertation Defense
BY: Jeffrey Lloyd
TIME: Tuesday, March 18, 2014, 1:00 p.m.
PLACE: MRDC Building, 4211
TITLE: Microstructure-sensitive Simulation of Shock Loading in Metals
COMMITTEE: Dr. David L. McDowell, Chair (ME)
Dr. Min Zhou (ME)
Dr. Naresh N. Thadhani (MSE)
Dr. Julian J. Rimoli (AE)
Dr. Shuman Xia (ME)
Dr. John D. Clayton (ARL)


A constitutive model has been developed to model the shock response of single crystal aluminum from peak pressures ranging from $2-110$~GPa. This model couples a description of higher-order thermoelasticity with a dislocation-based viscoplastic formulation, both of which are formulated for single crystals. The constitutive model has been implemented using two numerical methods: a plane wave method that tracks the propagating wave front; and an extended one-dimensional, finite-difference method that can be used to model spatio-temporal evolution of wave propagation in anisotropic materials. The constitutive model, as well as these numerical methods, are used to simulate shock wave propagation in single crystals, polycrystals, and pre-textured polycrystals. Model predictions are compared with extensive existing experimental data and are then used to quantify the influence of the initial material state on the subsequent shock response. A coarse-grained model is then proposed to capture orientation-dependent deformation heterogeneity, and is shown to replicate salient features predicted by direct finite-difference simulation of polycrystals in the weak shock regime. The work in this thesis establishes a general framework that can be used to quantify the influence of initial material state on subsequent shock behavior not only for aluminum single crystals, but for other face-centered cubic and lower symmetry crystalline metals as well.