(261g) A Nonlinear Elasto-Plastic Bonded-Sphere Model for the Discrete Element Simulation of Biomass Particle Breakage

To enhance the current understanding of biomass fracturing mechanism so as to optimize the mechanical preprocessing techniques for biomass size reduction, a discrete element method (DEM) model has been proposed and developed with customized bonding laws designed specifically for biomass materials. The customized bonding laws are able to capture the elasto-plastic deformation within a single biomass particle under compression, bending, and twisting. To better match the experimental observations, two additional nonlinear force-displacement form for normal force contact freedom are proposed as well, i.e., quadratic form and square root form. The fracturing of biomass particles is simulated by allowing the bond to break based on the normal and shear strength criteria. Simulation cases of fracturing tests of loblolly pine cube have been developed and further validated by comparing to the physical experiments. It is shown the elasto-plastic DEM model with a square root force-displacement form can replicate the mechanical failure of pine cubes under shearing with a higher fidelity comparing to the linear elastic bonded-sphere model. By assigning different bonding strengths across the growth ring, the DEM model is able to simulate the anisotropic behavior of pine cubes with different fiber orientations, which is a key factor that should be considered in the biomass processing modeling. Future research will focus on understanding the grinding process of biomass particles for equipment optimization and energy consumption minimization.