DEM modelling of surface indentations caused by granular materials: application to wheel-rail sanding.

The presented surface indentation model is one step towards building a DEM model for wheel-rail sanding. In railways, so-called low-adhesion conditions can cause problems in traction and braking, and sanding is used to overcome this problem. Sand grains are blasted towards wheel-rail contact, fracture repeatedly as they enter the nip and are drawn into the contact and then increase adhesion.

Efficient DEM simulations of railway ballast using simple particle shapes.

For complex shaped materials, computational efficiency and accuracy of DEM models are usually opposing requirements. In the literature, DEM models of railway ballast often use very complex and computationally demanding particle shapes in combination with very simple contact laws. In contrast, this study suggests efficient DEM models for railway ballast using simple particle shapes together with a contact law including more physical effects.

DEM modelling of railway ballast using the Conical Damage Model: a comprehensive parametrisation strategy.

Despite ongoing research, the parametrisation of a DEM model is a challenging task, as it depends strongly on the particle shape representation used, particle-particle contact law and the simulated applications: for railway ballast e.g. lab tests or track conditions.

Shape analysis of railway ballast stones: curvature-based calculation of particle angularity.

Particle shape analysis is conducted, to compare two types of railway ballast: Calcite and Kieselkalk. Focus lies on the characterisation of particle angularity using 3D scanner data. In the literature, angularity is often characterised using 2D data, as these types of data are easier to collect.

Simple particle shapes for DEM simulations of railway ballast: influence of shape descriptors on packing behaviour.

Abstract: In any DEM simulation, the chosen particle shape will greatly influence the simulated material behaviour. For a specific material, e.g.

Micro-mechanical investigation of railway ballast behavior under cyclic loading in a box test using DEM: effects of elastic layers and ballast types.

Abstract: Ballasted tracks are the commonly used railway track systems with constant demands for reducing maintenance cost and improved performance. Elastic layers are increasingly used for improving ballasted tracks. In order to better understand the effects of elastic layers, physical understanding at the ballast particle level is crucial.

Comparison of two different types of railway ballast in compression and direct shear tests: experimental results and DEM model validation.

Railway ballast is an angular and coarse material, which demands careful DEM modelling and validation. Particle shape is often modelled in high accuracy, thus leading to computational expensive DEM models. Whether this effort will increase the DEM model's overall prediction quality will also vitally depend on the used contact law and the validation process.

Parametrisation of a DEM model for railway ballast under different load cases.

The prediction quality of discrete element method (DEM) models for railway ballast can be expected to depend on three points: the geometry representation of the single particles, the used contact models and the parametrisation using principal experiments. This works aims at a balanced approach, where none of the points is addressed with excessive depth. In a first step, a simple geometry representation is chosen and the simplified Hertz-Mindlin contact model is used.

Friction phenomena and their impact on the shear behaviour of granular material.

In the discrete element simulation of granular materials, the modelling of contacts is crucial for the prediction of the macroscopic material behaviour. From the tribological point of view, friction at contacts needs to be modelled carefully, as it depends on several factors, e.g.