Abstract
The goal of this PhD work is to develop a numerical modeling approach of the compaction of powders composed of crushable particles in the framework of the Contact Dynamics method in view of application to the manufacture process of nuclear fuel. The particles are modeled as cohesive aggregates of potential fragments (cells) of irregular polyhedral shape. Using this Bonded Cell Method, we performed a parametric investigation of the strength of particles with respect to the geometrical and mechanical model parameters. Our results reveal two regimes and a power-law scaling of the compressive strength as a function of the ratio between tangential adherence and normal adhesion between cells. We optimized the model parameters for the uniaxial compression of packings of a large number of crushable particles. The simulations allow us to identify the mechanisms of compaction and fracture of particles, and to characterize the evolution of texture and the sizes and shapes of fragments. Our simulation results clearly show that the compaction process is strongly nonlinear as a consequence of the evolution of particle size distribution, which controls the texture and stress transmission. We also perform a systematic analysis of the effect of size polydispersity in the case of spherical particles.