(139b) Numerical Determination of Contact Laws for Compressible Particles

In the study of particulate matter, numerical simulation can play a role in efforts to gain insight into the influence of intermolecular forces, crystal structure, surface topology, particle material properties and surface chemistry on powder bulk properties by enabling controlled investigation of the effects of small-scale mechanisms on large-scale behaviour. The accuracy of discrete approaches to modelling the static and dynamic behaviour of granular media is dependent on their accuracy in representing particle-particle interactions, which may include plastic, viscoelastic, viscoplastic, adhesive and large deformation effects (see, for example, Tomas (1993)). Parameters for contact laws including these features may be found experimentally (see, for example, Pasha et al (2014)). However, normal contact relations for particles exhibiting compressible plastic behaviour derived from underlying smaller-scale mechanics are not found in the literature. We present work aimed at developing such relations based on parametric finite element (FE) studies of spherical particles in contact. This includes (1) A description of the finite element model and compressible plasticity models employed for the simulations, (2) nondimensionalisation of the problem, (3) derivation of an explicit normal force-displacement relation for contact of compressible spheres and its dependence on material parameters, (4) qualitative mapping of the spatial development of plastic and compression zones, (5) investigation of the sensitivity of the resulting contact law to the compression plasticity model used, and (6) introduction of adhesive effects in the FE contact law and a study on its effects on the resulting inter-particle contact law. It is intended that the results from this work will help improve the accuracy of discrete element and similar tools by providing normal contact laws dependent on properties that can be determined from experiment.

References

Tomas, P., 2003, Mechanics of Particle Adhesion, In Particles on Surfaces 8: Detection, Adhesion and Removal, pp. 183-229.

Pasha, M., Dogbe, S., Hare, C., Hassanpour, A., Ghadiri, M., 2014, A linear model of elasto-plastic and adhesive contact deformation, Granular Matter 16, pp. 151-162.