A Hysteretic Nonlinear Elastoplastic Contact Model for Discrete Element Modeling of Milled Woody Biomass

Abstract: Milled woody biomass, such as pine residuals, features irregular-shaped flexible particles. According to the axial loading-unloading experimental tests, milled pine particles manifest a strong nonlinearity in their bulk stress-strain behavior, which is challenging to simulate with discrete element methods (DEM) with simple contact models. This work presents the development of a hysteretic nonlinear elastoplastic contact model for spherical DEM. The formulation of the contact model is conceptualized with the bulk stress-strain relations measured in the physical tests. In particular, a hysteresis of plasticity between each two DEM particles in contact is proposed to capture the plastic deformation of a bulk of milled pine particles subjected to repeated compression. The contact model is implemented to an open-source DEM package, LIGGGHTS, and calibrated through simulations of a cyclic loading-unloading test to match the equivalent physical test results.