Contact models for DEM simulations of non-spherical particles

The discrete element method (DEM) is a simulation tool originally developed in the 1970s. DEM allows complex systems of particles to be modelled, enabling analysis of the particle-scale mechanisms that underlie the complexity of the overall material response. The insights obtainable from DEM simulations have led to a huge increase in the popularity of the method in recent years. This growth has also been driven by constant increases in computational power and the availability of more user-friendly software. In the most common implementation of DEM, particles are modelled as rigid bodies. Deformations of particles at the contact points are captured by permitting overlaps between the interacting bodies. Within the algorithm, forces are generated between overlapping particles. The interparticle forces at the contact points are evaluated using suitable force–displacement relations termed ‘contact models’.

Spheres have generally been used to model particles in 3D DEM simulations for computational simplicity. However, because particle shape is often an important factor, there has been a major increase in scientific interest in DEM modelling of non-spherical particle systems: between 2012 and 2015, the number of publications on the topic has doubled. A major limitation of DEM simulations using non-spherical particles is the lack of appropriate mathematical relationships between the contact force and interparticle overlap. Contact models suitable for spheres are usually adopted which is not physically justifiable. This has been identified as a barrier to the use of DEM for industrial applications.

This PhD project will address this problem in several stages. Existing contact models will be critically assessed in terms of physical realism and computational tractability. More realistic models will be proposed based on the results of finite element analyses and laboratory testing of non-spherical particles. The proposed contact models will be implemented in an open-source DEM code. Simple test cases, e.g., uniaxial compression, will be simulated to quantify the effect of the contact model on the bulk behaviour of the material.