Date of Award

Spring 1-1-2012

Document Type

Thesis

Degree Name

Master of Engineering (ME)

First Advisor

Richard A. Regueiro

Second Advisor

Franck Vernerey

Third Advisor

Ronald Pak

Abstract

In this comparative study of RVEs, a DEM code ELLIP3D is utilized to simulate quartz sand in triaxial compression tests with particle assemblies attained from an in situ fabric generated by synchrotron X-ray microcomputed tomography. In order to attain meaningful results for engineered systems at the macroscopic scale using DEM, RVE volume sizes play a significant role in the accuracy of simulating physical experiments. Simulation time or the number of particles limits the capacity of DEM to simulate large-scale granular systems, which is why it is crucial to determine an efficient quantity and quality of RVEs.

ELLIP3D simulations have been carried out to evaluate a minimum threshold for RVE size for which a comparison of results from various sized boxed particle assemblies provides valuable information on the quantitative behavior of RVEs. The mid-progress and final results of the ELLIP3D simulations are compared to experimental data from synchrotron micro-computed tomography (SMT) scans. These data containing the initial numerical packing from the scans provide us with the particles' radii, positions, and orientations which are approximated as ellipsoids, which is a current limitation of ELLIP3D, but extension to poly-ellipsoids is being planned. Additionally, a comparison between simulations of triaxial compression on in situ fabric versus a slightly displaced fabric due to gravity deposition on an assembly of ellipsoidal particles is explored.

Furthermore, a bilinear elasto-plasticity constitutive model is implemented into ELLIP3D to explore a more realistic phenomenon within the interparticle interaction for materials that exhibit such behavior. Elasto-plastic deformation is appropriate in studies involving metallic powders. The results of a two-particle compaction simulation using DE modeling are compared to finite element (FE) simulations.

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