Model cohesive powders : assembling process and plastic consolidation

Discrete element simulations are used to investigate the assembling and the plastic consolidation behavior of model cohesive powders which consist of two-dimensional aggregates of disks. The material state varies with a reduced pressure P∗ comparing the confining pressure to the maximum tensile contact force, and sensitively depends on the assembling process. If initially a continuous structure has formed before the confining stress is applied, loose configurations are obtained, with the fractal dimension of ballistic aggregation clusters characterizing density correlations on scales between the grain size and a certain blob size ξ. The coordination number varies with the initial agitation velocity and with the resistance to rolling in contacts. Under growing P∗, the system undergoes an irreversible collapse similar to the plastic consolidation of clays and powders in which the characteristic size ∼ ξ of the larger pores decreases and the microstructure of cohesionless granular assemblies is gradually recovered