Three dimensional shape analysis of JSC-1A simulated lunar regolith particles

The 3D shape of a fairly broad size range of the particles of the lunar regolith simulant JSC-1A was characterized. After wet screening with water, the size classes that were kept and investigated were: those retained on a 300 μm ASTM screen, those passing the 300 μm screen but retained on a 75 μm screen, those passing the 75 μm screen but retained on a 38 μm screen, and those passing the 38 μm screen but retained on a 20 μm screen. Samples of all four size fractions were embedded in epoxy and formed into cylindrical specimens. These specimens were scanned with X-ray computed tomography (X-ray CT). The resulting two dimensional (2D) slices were stacked into 3D microstructures. Particles were segmented and removed computationally. A total of 131 034 particles were found and used. Spherical harmonic coefficient expansions were then created for each particle, and the volume, surface area, dimensions (length L, width W and thickness T), integrated mean curvature, and principal moments of inertia were computed for each particle in 3D as well as a 3D VRML image of each particle analyzed. A projection algorithm was used to compute the apparent aspect ratio as would be seen by a 2D optical system. This report presents the 3D particle size and shape distributions for the various size classes using various 3D measures of particle size and shape and a comparison of 2D and 3D shape parameters. The data generated were also used to critique the shape of a model JSC-1A particle used in a discrete element modeling study.