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

Abstract

Particles slide and roll on each other when a granular medium is sheared. Consequently, the tribological properties, such as inter-particle friction and adhesion, play a major role in influencing their bulk failure and rheology. Although the influence of roughness on adhesion and friction of contacting surfaces is known, the incorporation of the surface roughness in the numerical modelling of granular materials has received little attention. In this study, the boundary element method (BEM), which is widely used for simulating the mechanics of interacting surfaces, is coupled with discrete element method (DEM) and the bulk deformation of granular materials is analysed. A BEM code, developed in-house, is employed to calculate the normal force-displacement behaviour for rough contact deformations, based on which a contact model is proposed. This is an efficient and relatively fast method of calculating the contact mechanics of rough surfaces. The resulting model is then implemented in the simulations by DEM to determine the effect of micro-scale surface roughness on the bulk compression of granular materials. This study highlights the importance of the effect of surface characteristics on contact behaviour of particles for the case of shallow footing and provides an efficient approach for modelling the flow behaviour of a large number of rough particles. Keywords Contact mechanics • Numerical modelling • Discrete element method • Boundary element method List of symbols A c Area of contact E Elastic modulus E * Effective contact elastic modulus H Hardness N Total number of nodes in the domain φ Coefficient of friction p s 1 , s 2 Applied contact pressure r Rigid body movement of two rough surfaces in normal direction R Radius of sphere s 1 , s 2 Coordinate of area that pressure is applied S q Root mean squared height u z (x,y) Material deformation F N Load in the normal direction (x, y) Coordinate in which surface deformation is obtained Z 1 , Z 2 The surface profiles of the two rough particles α, β Roughness parameters ν Poisson's ratio

Influence of Loading History and Soil Type on the Normal Contact Behavior of Natural Sand Grain-Elastomer Composite Interfaces

“…The SEM images in Figure 1 can provide some qualitative inferences on the surface texture at the meso-scale of the different types of aggregates, whose textural characteristics may have an important influence on their tribological behavior, for example, the presence of debris [ 78 , 79 ] or meso-scale morphology [ 80 ]. However, the surface roughness at the micro-scale (expressed with an RMS value in the present study) is itself an important characteristic that controls the frictional and constitutive behavior of interfaces [ 70 , 81 , 82 ] and also the bulk behavior of granular materials [ 46 , 60 , 61 , 62 , 83 , 84 , 85 ]. For quantitative evaluation of surface roughness, an optical surface profiler (Wyko NT9100 Surface Profiler, Veeco Instruments Inc., Tucson, AZ, USA) was used, and the surface roughness values were calculated from the standard deviation of the asperity peaks from the mean height ( S q as shown in Equation (1)) for a given area.…”

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

“…Smooth joint logic (SJL) accounts for the movements along fracture surface. A modified contact relation proposed by Greenwood and Tripp [14] and extended by Nadimi et al [35] is introduced to estimate the normal force-displacement from rough contact .…”

“…When two rough fracture surfaces pressed against one another, the effective stiffness of the interfaces are known to be affected by surface roughness [30]. 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 latter regards rocks as an assembly of microstructural elements that interact with each other by microstructural forces [33]. For the numerical simulation of naturally-fractured reservoirs, it mainly raises two main issues [35]. The first issue is still the intrinsic complexity of fracture networks [2,9].…”

On the contact problem of soft-rigid interfaces: incorporation of Mindlin-Deresiewicz and self-deformation concepts

“…The importance of the contact and frictional behavior of interfaces as well as grain morphological and elastic characteristics on the bulk constitutive response of granular materials has been acknowledged by many researchers through experimental works [15,[29][30][31] and theoretical/numerical studies [32][33][34][35][36][37][38][39][40][41], or combining advanced testing with computer simulations [42,43]. The coefficient of interparticle friction (μ), which, in turn, is affected by material type and morphology, influences the dilation behavior, the bulk strength and the energy dissipation of particulate materials.…”