Compaction of highly deformable cohesive granular powders

Compaction of granular powders underpins many engineering and industrial processes. The physics underlying the compaction process of highly deformable, cohesive granular powders remains poorly understood. A Multi -Particle Finite-Element Method (MPFEM) is presented to examine the mechanical responses of cohesive gran-ular powders under compaction and decompaction. Each powder grain is assumed to be plastically deformable and is discretized by finite elements. Intergranular cohesion and its breakage are described by a cohesive inter -grain contact model. The proposed MPFEM is first validated and verified by powder grain contact problems. It is further employed for systematic simulations of the compaction of cohesive powder assembly under different loading paths, including unconfined compression, triaxial compression, and cycling loading. The simulation results are systematically analyzed and discussed pertaining to the elastic, yielding, damage, and hysteresis re-sponses of the compacted powder assembly in relation with the constituent powder grains. Quantitative corre-lations are identified between the elastic recovery and Young's modulus of the compacted powder assembly with the relative density and the Young's modulus of individual powder grains. Maximum relative density under the compaction is found positively correlated with both unconfined and triaxial compression strengths of the as-sembly. Inter-particle bond strength is found to play an important role in shaping the yield surface and enhancing the strain hardening behavior of the powder assembly. While the unconfined compressive strength of the powder assembly shows an exponential increase with bond strength, the Young's modulus is found to increase to a saturated value with bond strength. The study provides an effective numerical approach to simulate the mechanical responses on dense compaction of cohesive, plastically deformable granular materials and helps shed lights into the understanding of powder compaction.