GEORGIA INSTITUTE OF TECHNOLOGY

Under the provisions of the regulations for the degree

DOCTOR OF PHILOSOPHY

on Wednesday, February 14, 2018

11:00 AM

in MaRC (Callaway) 201

will be held the

DISSERTATION PROPOSAL DEFENSE

for

Travis J. Voorhees

"Investigating the Dynamic Compaction Behavior of Brittle Powders"

Committee Members:

Prof. Naresh Thadhani, Advisor, MSE

Dr. D. Anthony Fredenburg, Los Alamos National Laboratory

Prof. Min Zhou, ME

Prof. Kimberly Kurtis, CEE

Prof. Preet Singh, MSE

Abstract:

The compression of porous materials to full density is a complex physical and mechanical process.  Modeling efforts to capture the compaction behavior of distended solids (e.g., porous materials or powders) have produced a variety of compaction models, each functionalized to address specific compaction mechanisms.  Of the available models, those suited for high-strain-rate deformation associated with shock loading have generally been developed for ductile materials. Compaction models for brittle materials have only been developed for quasistatic loading conditions.  No predictive models currently exist that successfully capture the physical processes and mechanics for shock compaction of brittle distended materials, such as sand and oxide powders.

The primary hindrance in producing a dynamic compaction model for brittle distended materials is the lack of availability of high-fidelity, high-precision shock compaction data for validation. The proposed work is aimed at alleviating this issue by developing a high-precision testing method in combination with high-fidelity analysis methods to accurately and precisely determine the shocked state of an ideal test material, ceria powder, under uniaxial strain dynamic compaction.  The measured shock compaction data from these brittle powder experiments is then used in initial computations to design a cylindrically converging shock compaction experiment with in situ time-resolved shocked density measurements, employing proton radiography.  The preliminary experimental and computational results obtained from these uniaxial strain dynamic compaction and cylindrically converging shock compaction experiments are presented.  An experimental and computational path forwards to predictive model development is then proposed.