PhD Defence Max Winkelmann | Micropolar Fields in Granular Materials: Theory and Simulations

Micropolar Fields in Granular Materials: Theory and Simulations

Max Winkelmann is a PhD student in the Department of Multiscale Mechanics. Promotors are prof.dr. S. Luding and prof.dr. V. Magnanimo from the Faculty of Engineering Technology and dr. S. Papanicolopulos from the University of Edinburgh.

Granular materials such as sand, grains, powders, and pharmaceutical particles are encountered in many natural phenomena and industrial processes. Despite their everyday presence, predicting their mechanical behaviour remains a major scientific challenge. Traditional continuum models describe how these materials deform and flow but generally neglect rotational motion of individual particles, even though such rotations can strongly influence the overall material behaviour.

This thesis investigates how microscopic particle rotations and torques can be systematically incorporated into continuum descriptions of granular materials. Starting from discrete particle interactions, a consistent theoretical framework is developed that connects particle-scale mechanics to enriched continuum models through homogenisation techniques.

The research demonstrates that micropolar continuum theory provides a natural and physically consistent way to capture rotational effects in granular materials. New homogenisation procedures are developed for rotational continuum quantities, including relative spins and curvature rates, and their physical meaning is analysed in relation to microscopic particle interactions.

In addition, the influence of particle friction and particle shape on rotational behaviour is studied in detail. The results show that sliding friction, rolling resistance, torsion resistance, and particle geometry strongly affect the emergence of rotational fields and are closely related to localisation phenomena such as shear bands.

By establishing a systematic link between discrete particle mechanics and rotational continuum descriptions, this thesis contributes to a better mechanical understanding of granular materials and provides a foundation for improved predictive modelling of granular flows and deformation processes.