A set of hysteretic nonlinear contact models for DEM: Theory, formulation, and application for lignocellulosic biomass

Abstract

A monosphere discrete element method (DEM) model is introduced for elucidating the bulk mechanical behavior of granular biomass. This model considers each sphere as a representative elementary volume in bulk particles and is highly scalable in computation. To compensate for the simplification of particle shapes, we propose a set of hysteretic nonlinear contact models for approximating the bulk strain-hardening phenomena of granular biomass in handling and storage conditions. These contact models comprise of simple polynomial and/or exponential functions to allow for easy calibration. To ensure numerical stability, we have derived unconditionally stabilized viscous damping force models. The resultant DEM model is implemented in LIGGGHTS-INL and applied to simulate an axial compressibility test for milled pine chips. Results show that the DEM model can reproduce the bulk stress–strain profiles of the physical samples and that the predicted bulk compressibility and constrained modulus under repeated compression agree reasonably with the experimental data.