Studying the collective behavior of adhesive particles with discrete element method (DEM) requires well-founded force–displacement relations (force models). While Johnson–Kendall–Roberts (JKR) theory reliably predicts dependence contact radius a on force F, it has remained challenge in this framework to obtain straightforward relation F(δ) physically meaningful parameters calculate F from displacement δ. We derive novel JKR as composition functions F(δ)=(F∘a∘λ)(δ), intermediate a(λ) and...

Recent studies of two-dimensional poly-disperse disc systems revealed a coordinated self-organisation cell stresses and shapes, with certain distributions collapsing onto master form for many processes, size distributions, friction coefficients, orders. Here we examine the effects grain angularity on indicators self-organisation, using simulations bi-disperse regular $N$-polygons varying $N$ systematically. We find that: strong correlation between local orientations, as well collapses...

Abstract Clay minerals are non-spherical nano-particles interacting through ranged van der Waals forces. Discrete Element Simulations usually use coarse numerical integration based on sphere clusters, as available analytical formalisms limited. In this paper, we discuss the implementation of a force for cuboid particles derived in previous research. particular, describe some corrections necessary its extension to pairs finite-sized particles.

This paper shows that negative coefficients of normal restitution occur inevitably when the interaction force between colliding particles is finite. We derive an explicit criterion showing for any set material properties there always a collision geometry leading to coefficients. While from phenomenological point view, appear rather artificial, this phenomenon generic and implies important overlooked limitation widely used hard sphere model. The explicitly applied two paradigmatic situations:...

We investigate the packing densities of non-elongated regular polyhedra and spheres via discrete element simulations. It turns out that limit many (hundred) corners does not correspond to with same Young's modulus. However, if modulus is simultaneously decreased, density approaches (harder) spheres. conclude mechanism for higher mobility particles, in case round particles due rolling. While rolling can occur at vanishing energetic costs perfect spheres, packings determined by height...

We report our experiences for the development of a neighborhood algorithm implemented via tree-codes to optimize performance discrete element method (DEM) convex polytopes. Our implementation two-dimensional tree code needs $N\log N$, as does sort and sweep approach. For choice boundary conditions (a rotating drum) system sizes (up several thousand particles), tree-code is slightly better, but considerably more complicated than

Shapes of constituent particles have a prominent effect on the macroscopic responses granular assemblies. Clayey minerals often possess plate-shaped geometry with large surface-to-volume ratio. It is difficult to model such spheres or clusters in conventional discrete element method (DEM). In this study, we present new DEM for focus particle and kinematics. The moment inertia general convex plate given unit quaternions are adopted represent angular degrees freedom. addition, equation motion...

While most granular materials in nature and technology consist of non-convex particles, the majority discrete element (DEM) codes are still only able to cope with convex due complexity computational geometry occurrence multiple contacts. We have reengineered a code for polygonal particles model as rigidly connected clusters. Constricting along symmetry axes by 30% leads an increase strength up 50%.

We present a novel formalism which allows to compute static friction forces in many body system of non-rigid particles for given normal and coefficients based on an exact constraint forces. derive criteria discriminate between dynamic at the contacts phase flow evaluate friction. Further, we compare results this with other approaches. several problems accuracy method discuss implement approaches numerical stabilization against creep.

We investigate the avalanches of spherical and non-spherical granular particles inside half-filled rotating drums. The time series center gravity particle assemblies are obtained via image analysis their single-sided amplitude (SSA) spectra analyzed. features this new indicator turn out to be characteristic for avalanches, in terms existence peaks low-frequency range decay rate high frequency components. SSA spectrum has a peak packings but not particles. part is characterized by power law...

Currently there exists no mechanically consistent "numerically exact" implementation of static and dynamic Coulomb friction for general soft particle simulations with arbitrary contact situations in two or three dimension, but only along one dimension.We outline a differential-algebraic equation approach computation dimensions compare its application to the Cundall-Strack model some test cases.

The effects of rock shape and initial orientation on the rockfall phenomena are studied using a two-dimensional polygonal discrete element method (DEM). In simulation, particles with same mass but different shapes dropped from height onto straight slope to investigate variations in both translational rotational kinetic energies runout distance. Parametric studies under varied angularity aspect ratio revealed significant effect

Grains in most technically relevant granular materials are non-convex, while discreteelement-simulations, convex particle shapes dominate. While differences the physical behavior can be expected, actual observables where these effects manifest far from clear. In this research, we investigate how a rotating two-dimensional drum, for rounded, irregular as well non-convex differs.

As a follow-up of an earlier work on the numerically exact Coulomb friction in two-dimensional simulations, we present here relations and implementation for three-dimensional discrete element particles.