Göran Frenning

Over the years, a significant amount of work has been devoted to understanding and predicting the mechanics of discontinuous matter, i.e., powders and granular materials. Depending on the rate and magnitude of the applied stresses, this ubiquitous state of matter can exhibit behaviours that resemble gases, liquids and solids. Our focus here is the (solid-like) behaviour of granular matter when subjected to pressures. The response may be slow, as for consolidation of soil and gravel in a civil engineering context, or rapid, as for confined compression of powders to form tablets in the pharmaceutical industry. Likewise, a large range of pressures may be encountered, ranging from consolidation of a powder under its own weight to the application of high pressures, typically in the MPa range, but sometimes even larger.

Ultimately, the mechanics of powders and granular materials of course stem from the characteristics of the constituent particles. The response of a single particle to an applied stress is typically investigated by subjecting the particle in question to uniaxial loading, using a texture analyser or a similar instrument, and observing the deformation and fracture characteristics. However, this loading condition does not mimic the ones encountered during confined compression, since the typical particle then is surrounded by a number of neighbours which provide mechanical support. For this reason, it is of interest to investigate the mechanics of single particles subjected to complex compressive loading conditions.

Our purpose with this presentation is to survey the current knowledge about the mechanics of single particles subjected to such complex loadings, as obtained from experiments and simulations, and how this knowledge can be used to formulate models for discrete element simulations of confined compression.

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Göran Frenning