Microstructure evolution during impact on granular matter

Abstract

We study the impact of an intruder on a dense granular material. The process of impact and interaction between the intruder and the granular particles is modeled using discrete element simulations in two spatial dimensions. In the first part of the paper we discuss how the intruder's dynamics depends on (1) the intruder's properties, including its size, shape and composition, (2) the properties of the grains, including friction, polydispersity, structural order, and elasticity, and (3) the properties of the system, including its size and gravitational field. It is found that polydispersity and related structural order, and frictional properties of the granular particles, play a crucial role in determining impact dynamics. In the second part of the paper we consider the response of the granular system itself. We discuss the force networks that develop, including their topological evolution. The influence of friction and structural order on force propagation, including the transition from hyperbolic-like to elastic-like behavior is discussed, as well as the affine and nonaffine components of the grain dynamics. Several broad observations include the following: tangential forces between granular particles are found to play a crucial role in determining impact dynamics; both force networks and particle dynamics are correlated with the dynamics of the intruder itself.

Granular Impact

“…The discussion given here is focused on the influence of system parameters on the penetration trajectory. More in-depth analysis can be found in [28], and the details about the simulations are given in the Techniques section. We note that simulations using a nonlinear force model (α = 1) are in progress and will allow more detailed comparision to experiments.…”

Conical wave propagation and diffraction in two-dimensional hexagonally packed granular lattices

“…Wave propagation has been studied extensively in one-dimensional (1D) granular crystals where robust highly localized waves and variants thereof have been identified in various configurations, see the reviews [23][24][25][26]. Higher dimensional granular crystals have also been studied [36][37][38][39][40][41][42][43][44][45][46][47][48][49][50][51][52], but to a far lesser extent than in 1D. If the particles are packed so that they are just touching, then the resulting dynamics are purely nonlinear, and hence there is no dispersion.…”

Penetration in bimodal, polydisperse granular material

“…In order to derive the key physical mechanisms and properties governing impact-related phenomena such as crater formation, a number of studies [3][4][5][6] have focused on a simple experiment-namely-the impact of a sphere onto a static granular bed in order to assess the penetration depth of the sphere and size of the resulting crater using model granular materials. In addition, a number of studies focus on the temporal evolution of forces acting within the granular medium and on the impactor [7][8][9][10][11], while others have paid attention to the ejecta formations in various impact experiments [12][13][14][15][16]. For shallow penetrations, where δ = O(D 0 ) [see Fig.…”