Three dimensional granular material study numerically with discrete element method and experimentally with magnetic resonance imaging

Two new tools were developed in this dissertation. The first tool is the experimental method using the magnetic resonance imaging (MRI) to obtain non-invasively microscopic information of a suitable granular material. The second tool is an improved computer program named ELLIPSE3J.; Simulations of random arrays of spheres and ellipsoids using the discrete element method (DEM) have shown certain macroscopic behavior of granular materials. It is the ultimate goal to obtain microscopic information of these granular materials to aid the development of a micromechanical basis constitutive model. The abundant fabric information produced by DEM can accomplish this goal. However, there is no 3-D experimental data to compare the numerical microscopic observation. It is here to develop a tool that can provide fabric information using MRI technology.; The comparison was conducted under the same conditions. Spherical pharmaceutical pills were selected as the granular material. Tests were conducted to obtain the material properties of these pharmaceutical pills that required for the numerical simulation. The macroscopic and microscopic characteristics were experimentally observed by conducting simple shear tests inside the MRI equipment. The experimental result was simulated by a 3-D DEM program ELLIPSE3. Good agreement was found between the result of the numerical simulation and that of the simple shear test with MRI at both macroscopic and microscopic levels. It reveals that ELLIPSE3 can be used as a reliable tool to study the behavior of granular materials.; In addition, great effort was made to rewrite the 3-D DEM code, ELLIPSE3, written in FORTRAN 77, to ELLIPSE3J, which was written in Java. Although both codes produced identical results, many new options were incorporated in ELLIPSE3J. The new code ELLIPSE3J is user-friendly, easy to maintain, and easy to extend. The new program is menu-driven in lieu of the command driven in ELLIPSE3. One of the advantages is any data can be retrieved at any moment during execution. Also particle visualization, micro- and macro-data analyses, and graphic display are included in this new program that does not require other commercial software.