Representative Elementary Volume Analysis of Sands Using X-Ray Computed Tomography

Abstract

The concept of a representative elementary volume (REV) provides an effective means of developing macroscopic measures in the description of granular materials. However, due to the difficulties associated with the measurement and characterization of granular microstructure the existence and size of an REV has remained largely conjectural. This study presents a systematic method to examine the characteristics of the REV using X-ray computed tomography images. The 3-D images of spherical glass beads, Silica sand, and Ottawa sand have been characterized using advanced image processing techniques. An interactive computer program is developed to study porosity variation within a sphere with increasing radius from the images of these materials. The porosity variation of Silica sand and Ottawa sand showed three characteristic regions: an initial fluctuation region due to microscopic variations, a constant plateau region, and a region with a monotonic increase/decrease due to heterogeneity. The homogenous medium of glass beads did not show the last region. The results show that for a random packing of spherical glass beads the REV is about two to three times of the identical average diameter. The radius for Silica sand composed mainly of elongated particles is between 5 to 11 times of d50 and for Ottawa sand composed mainly of subrounded particles is between 9 to 16 times of d50.

Evolution of deformation and breakage in sand studied using X-ray tomography

“…The REV chosen in this work has a size of 2·9D 50 , which is consistent with the literature for spherical/sub-spherical uniform assemblies (e.g. Razavi et al, 2006). It should be mentioned that the limited amount of breakage did not cause the D 50 to change (as can be seen in the following sections), and so in this paper D 50 will refer to both initial and final mean particle size.…”

Understanding the Influence of State/Phase Transitions on Ice Recrystallization in Atlantic Salmon (Salmo salar) During Frozen Storage

“…This study used the 225-keV micro-focused source to achieve enhanced resolution. 18,19 The CT scanning involved several steps: placing the specimen on the rotary stage, initiating the data acquisition from the work station, recording X-ray intensities before and after penetrating the specimen while rotating the specimen at small angles, collecting CT numbers over a full revolution, and analyzing CT numbers 19 to return sinograms of each slice.…”

Determination of the size of representative volume element for viscous sintering

“…This result agrees with the values reported for granular materials. 14) However, this normalization is done with respect to the initial microstructure, which completely disappears during sintering.…”

“…Recent advances in X-ray microtomography 12) and focused ion beam-scanning electron microscopy 13) have opened the door for observation of detailed microstructural evolution during sintering, and provides an opportunity to analyze the RVE from the knowledge of microstructure experimentally. In the field of particle packing, for example, Razavi and coworkers 14) reported that the concept of RVE provides an effective means of developing macroscopic measures in the description of granular materials. The RVE size has been determined for electrodes of a Li-ion battery 15) and solid oxide fuel cell.…”