Multiscale ‘tomography-to-simulation’ framework for granular matter: the road ahead

Abstract

A roadmap is presented to transition seamlessly from an image to a predictive computational model for granular materials. So far, constitutive modelling in granular materials has been based on macroscopic experimental observations. Here, the point of departure is the basic granular scale where kinematics, contact forces and fabric control the macroscopic mechanical behaviour of the material. New computational and analytical tools are presented that allow for more accurate measurement of kinematics and inference of contact forces, directly from imaging tools (e.g. highenergy tomography). These grain-scale data are then used to construct powerful multiscale models that can predict the emergent behaviour of granular materials, without resorting to phenomenology, but can rather directly unravel the micro-mechanical origin of macroscopic behaviour. The aim of these tools is to furnish a 'tomography-to-simulation' framework, where experimental techniques, imaging procedures, and computational models are seamlessly integrated. These integrated techniques will help define a new physics-based approach for modelling and characterisation of granular soils in the near future.

Network flow model of force transmission in unbonded and bonded granular media

“…Indeed, structural proxy measures for force and energy dissipation are helpful in advancing the state of knowledge on the transmission of force in 3D systems since contact forces have proven to be difficult to reliably capture, especially over many stages of a test under combined compression and shear [27,28,32]. Multiple advanced experimental techniques such as confocal microscopy [30], micro-CT scanning [31,34], refractive index-matching tomography [21], and neutron imaging [33] have been applied to overcome this challenge. While promising, these approaches are limited in the systems they can be applied to.…”

“…[11,[21][22][23][24][25][26]). This gap in knowledge has become one of the most pressing issues in the science of granular materials, no doubt pushed to the forefront by the rapid advances in imaging techniques [21,[27][28][29][30][31][32][33][34]. With unprecedented access to the grain scale and the ability to "see" inside a deforming granular material, we are now witnessing prodigious and complex data being generated on microstructural fabric (i.e., arrangement of grains and pores) for a wide range of spatial scales (e.g., Refs.…”

Multiscale characterization and modeling of granular materials through a computational mechanics avatar: a case study with experiment

“…In particular, we focus on the relevant algorithmic improvements. Earlier, these components have been briefly discussed in [7] and developed independently [6,40]. In this paper, we integrate these two components for the first time to enable the application of the avatar to a real problem.…”

“…This is problematic for two reasons. The first is that binary images introduce artificial roughness to grain surfaces, complicating a direct tomography-to-simulation paradigm [7]. The second, and more critical, drawback is the removal of details about the location and orientation of interparticle contact, which impedes our understanding of the physical sources of mechanical strength.…”

On the contact treatment of non-convex particles in the granular element method

“…A contact algorithm capable of dealing with general non-convex NURBS particles, to be described in this paper, would eliminate the above two limitations. As a result, a more faithful representation on the contact force distributions over particle boundaries is obtained and the image data-to-analysis pipeline (see for e.g., [24]) is significantly streamlined.…”