3D Shape Characterization and Image-Based DEM Simulation of the Lunar Soil Simulant FJS-1

Abstract

This paper describes a procedure used to characterize the three-dimensional ͑3D͒ grain shape of lunar soil and undertake simulations of lunar soil by image-based discrete element method ͑DEM͒. Given that detailed 3D grain-shape information is unavailable for real lunar soil, a simulant material, FJS-1, is used in this study. We use the high-resolution micro X-ray CT system at SPring-8, a synchrotron radiation facility in Japan, to visualize precise 3D images of the granular assembly of FJS-1. A newly developed imageanalysis procedure is then applied to identify individual grains. Using the obtained grain-shape data, a sufficient number of FJS-1 grains are directly modeled for DEM simulation using an efficient modeling scheme. A series of particle flow simulations are then performed with the modeled grains. The resulting slope angles are in good agreement with experimental results. We discuss the effect on the slope angle of grain parameters such as contact stiffness, restitution coefficient, and interparticle friction.

Microstructure-based modeling of snow mechanics: a discrete element approach

“…We chose the former approach, namely, the sphere clumping approach, because it is much simpler in terms of numerical implementation. In particular, the clumping approach is free of the singularity issues involved in the definition of contacts between faces, edges and points, which are difficult to handle and computationally demanding in terms of calculation (Matsushima et al, 2009). In the present study, a very simple technique based on nonoverlapping spheres was used to describe (or mesh) the snow grains into discrete elements.…”

Numerical Simulation of Tire-Ground System Considering Soft Ground Characteristics

“…5. This rotational constraint increases the shear strength and the stability of the soft ground (8)- (10) . To take this into account, we simulated non-round grains as clusters of round grains.…”

“…In the field of geotechnical engineering, it is widely recognized that an assembly of non-round (non-spherical) grains exhibits higher shear strength and stability than that of round (spherical) ones (8)- (10) . In general, soft ground is subject to weight loading every time a vehicle passes over it, and the process of loading, unloading and reloading is repeated.…”

“…Thus, improvement of the previous model by the addition of additional ground characteristics is needed. The soil grains that make up soft ground often have complex irregular shapes, which greatly affects the dynamic characteristics and behavior of an assembly of such grains (8)- (10) .…”

A micro finite-element model for soil behaviour

“…Efforts to overcome this limitation include the use of clusters or agglomerates of spheres/discs (e.g. Lu & McDowell, 2007;Wang et al, 2007;Matsushima et al, 2009;Cil & Alshibli, 2014;Katagiri et al, 2014;Yang et al, 2016). The outcomes from these studies have highlighted the effect of overall particle shape on the rolling resistance mobilised by the multiple contact points between two particles.…”