## Rotating Drum with single particle

A rotating drum with a single particle. You can find more information in this publications.

## Rotation and Reptation

In order to understand the peculiar behavior of granular matter, it is often elucidating to observe the physics of only a few grains. We present two setups whi ch fall into this class: The motion of a single part icle in a rotating drum, and the collective behavior of a few particles under the influence of a swirling motion.

## Rotation and Reptation

In order to understand the peculiar behavior of granular matter, it is oftenelucidating to observe the physics of only a few grains. We present twosetups which fall into this class: The motion of a single particle in arotating drum, and the collective behavior of a few particles under theinfluence of a swirling motion.

## Schwingungen bei trockener Reibung

A short talk on oscillations with dry friction.

## Shared Memory Parallelization for Molecular Dynamics Simulations of Non-spherical Granular Materials

The problem of granular materials is not alone a problem of material properties, but also a problem of structures. To examine these interesting systems, one uses molecular dynamics simulations. The objective of the work presented here was to have a program which can run on cheap high-end shared memory workstations. Therefore we have developed a fast thread-based simulation of polygonal particles.

## Shared Memory Parallelization for Molecular Dynamics Simulations of Non-spherical Granular Materials

The problem of granular materials is not alone a problem of material properties, but also a problem of structures. To examine these interesting systems, one uses molecular dynamics simulations. The objective of the work presented here was to have a program which can run on cheap high-end shared memory workstations. Therefore we have developed a fast thread-based simulation of polygonal particles.

## Simulation of cohesive granular materials

We present two-dimensional molecular dynamics simulations of cohesive regular polygons. We investigate the dependence of the angle of respose from the cohesion, which is in good agreement with experiments. Using this as validation, we investigate microscopic parameters which are not accessible to the experiment. This includes contact length, raggedness of the surface and correlation time.

## Spannungsverteilung in Sandhaufen

We are interested in the stress distribution in static granular matter. Experiments have found a **minimum** of the vertical normal stress beneath the apex of a sandpile. Because of the indeterminacy of static friction force even in the simplest sandpile and the ensuing absence of a constitutive relation between stress and strain (Hooke's law) there is no closed set of equations.

## Static friction, differential algebraic systems and numerical stability

We show how Differential Algebraic Systems (Ordinary Differential Equations with algebraic constraints) in mechanics are affected by stability issues and we implement Lubich’s projection method to reduce the error to practically zero. Then, we explain how the “numerically exact” implementation for static friction by Differential Algebraic Systems can be stabilized. We conclude by comparing the corresponding steps in the “Contact mechanics” introduced by Moreau.

## Statik und Dynamik von Aufschüttungen

Granular matter hides a very complex behaviour behind its apparent simplicity ("... is just sand"). Typical properties of granulates are, for example, the discrete structure and the inhomogeneity. This leads to the fact that backfills far away from thermal equilibrium can be very "stable" after all. The question now arises as to what consequences this has for the behaviour of sand accumulations.

## Statik und Dynamik von Aufschüttungen

Granular media conceal a very complex behaviour behind their apparent simplicity ("... is just sand"). Typical properties of granulates are, for example, the discrete structure and the inhomogeneity. This leads to the fact that backfills far away from thermal equilibrium can be very "stable" after all. The question now arises as to what consequences this has for the behaviour of sand accumulations.

## Steep Funnel

The slopes of this hopper are much steeper than in the other examples. We see here the mass flow regime, where the particles pour through the outlet like a liquid.

## Stress in Static Sandpiles

We are interested in the stress distribution in static granular matter. Experiments have found a **minimum** of the vertical normal stress beneath the apex of a sandpile.

Because of the indeterminacy of static friction force even in the simplest sandpile and the ensuing absence of a constitutive relation between stress and strain (Hooke's law) there is no closed set of equations. Continuum theories, trying to describe the "dip", have to make assumptions on the existence of constitutive relations among the components of the stress tensor itself.

## Stress in Static Sandpiles

We are interested in the stress distribution in static granular matter. Experiments have found a **minimum** of the vertical normal stress beneath the apex of a sandpile. Because of the indeterminacy of static friction force even in the simplest sandpile and the ensuing absence of a constitutive relation between stress and strain (Hooke's law) there is no closed set of equations. Continuum theories, trying to describe the dip, have to make assumptions on the existence of constitutive relations among the components of the stress tensor itself.

## Stress in Static Sandpiles

- What is the pressure distribution below sandpiles? → DIP
- How can I get information from the inside ?
- What can be stated about continuum theories now ?

## Stress Propagation in Sand Beds

A Poster on stress propagation in sand beds.

## Towards a micromechanic understanding of the pressure distribution under heaps

The pressure distribution under heaps has found to be dependent on the builing hostory of the heap both in experiments and simulations. Up to now, theoretical models and analysis assume that the packing of the heap is homogeneous. We show new experimental and simulational results which indicate that the packing is inhomogeneous and that this packing property is likley causing the pressure minimum under the heap.