Extended Greenwood–Williamson Models for Rough Spheres

Abstract

The current work aims to develop two extended Greenwood–Williamson (GW) models for spherical particles with surface roughness which can be incorporated into the discrete element modeling (DEM) framework. The defects of the classic GW model when directly adopted in DEM are fully addressed and illustrated by both theoretical and numerical results. The first model, the extended elastic GW (E-GW) model, which evaluates the elastic deformation of the asperities and the bulk substrate separately is developed to consider the positive overlap involved in the contact problem. The capability of incorporating the extended elastic model into the DEM is illustrated by the comparison between the classic and extended models. The second model, the extended elasto–plastic GW (EP-GW) model, is further developed to consider the plastic deformation of the asperities which reduces the pressure increased by the surface roughness. Numerical comparisons between the E-GW and EP-GW models are also conducted to demonstrate the effect of the plastic deformation on the pressure and deformation distributions in the contact region.

Towards data-driven constitutive modelling for granular materials via micromechanics-informed deep learning

“…to understand how to train a reliable model with the least data specimens. Besides, under the conditions that more advanced particlescale contact rules are developed to reproduce the realistic granular interactions (Feng et al, 2017;Feng, 2021a,b;Zhao and Feng, 2018) and that the DEM parameters are well-calibrated for representing realistic granular behaviour (Qu et al, 2020a,b), experiments-based granular testing is possible to be replaced with a large number of DEM modelling to reduce costs. The other application is to advance hierarchical multiscale modelling techniques where the constitutive laws are provided by the microscopic modelling (e.g.…”

Elastic characteristics for naturally-fractured reservoirs using an integrated LSM-DFN scheme with rough contact deformation

“…However, there are few attempts to consider the particle surface roughness in DEM [35], not to mention this LSM. The similar works so far can be categorized into two groups: Refining the geometry, or improve the contact model [38,5,15,45,48]. The former methodology is computationally expensive and restricted to meshing resolution [15,45].…”

“…For the latter, recently, researchers develop a micromechanical methodology for determining the effective interface stiffness, incorporating the surface roughness effects [35]. Specifically, Cavarretta et al [5], Otsubo et al [37], and T. Zhao and Feng [48] conduct the development of normal force-displacement relationships for rough surfaces based on the Hertz contact model. These models use the statistical approach of Greenwood and Tripp [14] with a particle-scale roughness index.…”

Effect of particle roughness on the bulk deformation using coupled boundary element and discrete element methods

“…However, there have been few attempts to include particle surface roughness in DEM. The works so far can be categorised into two groups: direct geometry refinement, and contact model enhancement [1,12,23,31,32]. In the former case, direct inclusion of roughness in DEM modelling has been carried out by assuming that asperities are small spheres, which are bonded to the main particles.…”

“…This methodology is computationally expensive and restricted to surface roughness with a spherical shape [12,31]. For the latter, development of normal force-displacement relationships for rough surfaces has been conducted by Cavarretta et al [1], Otsubo et al [23], and Zhao and Feng [32] using the statistical approach of Greenwood and Tripp [10]. In these models, a particle-scale roughness index proposed by Greenwood et al [11] has been used.…”