Probabilistic characterization and simulation of realistic particle shape based on sphere harmonic representation and Nataf transformation

Predicting residual friction angle of lunar regolith based on Chang'e-5 lunar samples

With the rapid development of human lunar exploration projects, the lunar base establishment and resource utilization are on the way, and hence it is urgent and significant to reasonably predict engineering properties of the lunar regolith, which remains to be unclear due to limited lunar samples currently accessible for geotechnical tests. In this contribution, we aim to address this outstanding challenge from the perspective of granular material mechanics. To this end, the 3D multi-aspect geometrical characteristics and mechanical properties of Chang'e-5 lunar samples are for the first time evaluated with a series of non-destructive microscopic tests. Based on the measured particle surface roughness and Young's modulus, the interparticle friction coefficients of lunar regolith particles are well predicted through an experimental fitting approach using previously published data on terrestrial geomaterials or engineering materials. Then the residual friction angle of the lunar regolith under low confining pressure is predicted as 53° to 56° according to the particle overall regularity and interparticle coefficient of Chang'e-5 lunar samples. The presented results provide a novel cross-scale method to predict engineering properties of lunar regolith from particle scale information to serve for the future lunar surface engineering construction.

A Review of Particle Size Analysis with X-ray CT

Particle size and morphology analysis is a problem common to a wide range of applications, including additive manufacturing, geological and agricultural materials' characterisation, food manufacturing and pharmaceuticals. Here, we review the use of microfocus X-ray computed tomography (X-ray CT) for particle analysis. We give an overview of different sample preparation methods, image processing protocols, the morphology parameters that can be determined, and types of materials that are suitable for analysis of particle sizes using X-ray CT. The main conclusion is that size and shape parameters can be determined for particles larger than approximately 2 to 3 μm, given adequate resolution of the X-ray CT setup. Particles composed of high atomic number materials (Z > 40) require careful sample preparation to ensure X-ray transmission. Problems occur when particles with a broad range of sizes are closely packed together, or when particles are fused (sintered or cemented). The use of X-ray CT for particle size analysis promises to become increasingly widespread, offering measurements of size, shape, and porosity of large numbers of particles within one X-ray CT scan.

A Novel Multi-Scale Particle Morphology Descriptor with the Application of SPHERICAL Harmonics

Particle morphology is of great significance to the grain- and macro-scale behaviors of granular soils. Most existing traditional morphology descriptors have three perennial limitations, i.e., dissensus of definition, inter-scale effect, and surface roughness heterogeneity, which limit the accurate representation of particle morphology. The inter-scale effect refers to the inaccurate representation of the morphological features at the target relative length scale (RLS, i.e., length scale with respective to particle size) caused by the inclusion of additional morphological details existing at other RLS. To effectively eliminate the inter-scale effect and reflect surface roughness heterogeneity, a novel spherical harmonic-based multi-scale morphology descriptor R_inc is proposed to depict the incremental morphology variation (IMV) at different RLS. The following conclusions were drawn: (1) the IMV at each RLS decreases with decreasing RLS while the corresponding particle surface is, in general, getting rougher; (2) artificial neural network (ANN)-based mean impact values (MIVs) of R_inc at different RLS are calculated and the results prove the effective elimination of inter-scale effects by using R_inc; (3) R_inc shows a positive correlation with the rate of increase of surface area R_SA at all RLS; (4) R_inc can be utilized to quantify the irregularity and roughness; (5) the surface morphology of a given particle shows different morphology variation in different sections, as well as different variation trends at different RLS. With the capability of eliminating the existing limitations of traditional morphology descriptors, the novel multi-scale descriptor proposed in this paper is very suitable for acting as a morphological gene to represent the multi-scale feature of particle morphology.