Short- and Long-Term Behaviour of Solid-Like Granular Materials

Granular materials conglomerations of discrete macroscopic solid particles are often found in na- ture. Processes like landslides, avalanches, erosion or plate tectonics are highly influenced by the static and dynamic behaviour of such materials. Granular materials also play an important role in many technical applications, like the production pro- cess of pills consisting of compressed granular materials including several additives. Sand brought into the wheel-rail contact for improving the traction and braking behaviour of railway vehicles is a further example for a technical application of granular materials as well as ballast of railway tracks. These kind of granular materials behave mainly like solids because the average energy of the individual par- ticles is low and the particles are fairly stationary relative to each other. The proposed project is focussing on granular materials under such conditions. The goal is to develop advanced particle based prediction models (Discrete Element Method (DEM) models) for the static and dynamic short- and long-term behaviour of solid-like granular materials. With respect to the short-term behaviour the modelling of friction between the particles and their con- tacts with their environment plays an important role. Currently Coulomb law of friction is mainly ap- plied where a constant coefficient of friction is assumed for the whole system. This approach is often insufficient to bring the models in accordance with experimental results. It is known from tribology that friction is influenced for example by loading conditions, surface-roughness and liquids within the contact and cannot be described by a constant coefficient of friction. For this reason one goal of the proposed project is to account for such effects by consideration of tribological effects within friction laws of DEM models. Together with an appropriate modelling of particle plasticity and particle break- ing due to exceeding the strength limit of the particles a significant improvement of the prediction quality for the short-term behaviour is expected. With respect to the long-term behaviour of granular materials under cyclic loading particle wear and breaking due to fatigue is of high relevance. Sufficient models for description of these effects are still not available. Thus, the development of physical fatigue models on a particle base taking into account the interaction with wear is a further goal of the proposed project. In this way a significant improve- ment of the prediction quality with respect to the long-term behaviour can be expected. For parameterisation of the developed advanced DEM models a method based on principal experi- ments will be developed. Thereby the kind of granular material and loading conditions will be taken into account. Finally the validity of the developed models and methods will be approved by applica- tion to examples of granular materials. Therefore several principal experiments will be performed within the proposed project.

No additional funding sources recorded.