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Séminaire GEOMAS (comodal : en ligne & présentiel - INSA) : Realistic particle shapes in DEM: polyhedra and Level Set approaches

Le 18 mai 2022

INSA : Bât. Charlotte Perriand, 3ème étage
en visioconférence :https://insa-lyon-fr.zoom.us/j/98004581144
ID de réunion : 980 0458 1144

Langue / language: the presentation will be in English

Jérôme Duriez, INRAE, Aix-Marseille Univ, Unité RECOVER

Jérôme Duriez
INRAE, Aix-Marseille Univ, Unité RECOVER

Lien Zoom : https://insa-lyon-fr.zoom.us/j/98004581144

Résumé au format pdf

The mechanical behavior of granular materials stems from micro-scale mechanisms such as interparticle friction and relative displacements, as well as particles rotations. These phenomena may be directly captured through the particle-scale point of view of Discrete Element Methods (DEM), provided that the microstructure is properly described. In particular, particle shape is a key feature controlling for instance the possibility for static equilibrium under given loads.
Aiming thus for a realistic description of particle shapes in DEM, the capabilities offered by polyhedral shape descriptors are first presented for a quantitative DEM model of Toyoura sand [1]. Polyhedral Discrete Elements are simply but efficiently defined in 3D from a 2D micrograph of Toyoura sand. In addition to show satisfactory predictive abilities for a wide range of loading conditions (drained and undrained triaxial compression and extension for various initial void ratios and confining pressures), the model also serves to illustrate once more the importance for a proper calibration in DEM of initial fabric, in addition to shape or contact parameters.
A second shape descriptor is also considered, adopting after [2] a "Level Set" approach (LS-DEM) by considering, for each particle, the distance function to its surface (Fig. 1). Being implemented into the YADE open-source code, the LS approach is shown to be logically orders of magnitude heavier than classical spheres [3] but possibly lighter than polyhedra [4]. Furthermore, adopting a parallel OpenMP execution as well as possible algorithmic optimizations allows to maintain LS computational costs to tractable quantities [3,4]. The versatility of the LS approach is illustrated on superellipsoids or rock aggregates characterized by 3D scanner (Fig. 1).

[1] T. Mohamed, J. Duriez, G. Veylon and L. Peyras, DEM models using direct and indirect shape descriptions for Toyoura sand along monotonous loading paths, Computers and Geotechnics, vol. 142, p. 104551, 2022.
[2] R. Kawamoto, E. Andò, G. Viggiani and J. E. Andrade, Level set discrete element method for three-dimensional computations with triaxial case study, Journal of the Mechanics and Physics of Solids, vol. 91, pp. 1–13, 2016.
[3] J. Duriez and S. Bonelli, Precision and computational costs of Level Set-Discrete Element Method (LS-DEM) with respect to DEM, Computers and Geotechnics, vol. 134, p. 104033, 2021.
[4] J. Duriez and C. Galusinski, A Level Set-Discrete Element Method in YADE for numerical, microscale, geomechanics with refined grain shapes, Computers and Geosciences, vol. 157, p. 104936, 2021.