Abstract
This PhD thesis investigates various deformation phenomena within granular materials.
The study uses numerical and experimental approaches to analyse swelling of grains due
to fluid absorption, pharmaceutical tablets disintegration and viscous sintering in food
grains.
In the first part of this thesis, a Discrete Element Method (DEM) model is developed to
simulate the expansion, during water absorption, of several type of grains, including
superabsorbent polymer (SAP), rice and microcrystalline cellulose (MCC). After
validation, the model is employed to explore swelling-induced percolation phenomena in
expanding granular systems. The results show that during swelling, fine particles
experience percolation, which subsequently enhances segregation or mixing of the system
based on its initial configuration. The size ratio between particles plays a key role and
higher size ratios result in more percolation. On the other hand, the swelling kinetic does
not significantly impact the percolation rate.
(This paragraph has been removed due to confidential information).
In the third part, the dynamics of viscous sintering in chocolate grains are investigated
through experiments and theoretical models. The experimental method developed in this
study allows to capture the grain coalescence and surface temperature which permit to
investigate the effect of grain size and heating conditions on the viscous sintering. Results
showed that larger grains sintered more slowly due to their reduced surface area to volume
ratio. Higher air flow temperatures and velocity accelerated the temperature increase and
bridge growth, with a kinetic parameter that exponentially increases with air temperature.
Moreover, a theoretical model is successfully adapted to predict the grains coalescence
based on surface temperature measurements.
Overall, the findings from the numerical simulations and experimental studies contribute
to a better understanding of deformation phenomena in granular systems and offer
valuable insights in various fields, ranging from food science to pharmaceuticals