Investigation of force transmission, critical breakage force and relationship between micro-macroscopic behaviors of agricultural granular material in a uniaxial compaction test using discrete element method

In this paper, numerical DEM simulations are presented that were used to study the response of agricultural granular materials, such as dry soybeans, in a uniaxial compaction test. To this aim, the microscopic parameters of soybeans (i.e., input parameters for DEM simulations) were taken from our previous published work through a calibration between experiments and DEM simulations. The response of the granular medium to the uniaxial compaction stresses, ranging from 0 to 200 kPa with a step of 50 kPa, was investigated locally using various variables, such as displacement field, force chain network, number of particles in contact, and distribution of force acting on particles. The macroscopic responses, such as porosity and axial shortening, were also investigated as a function of applied normal stress. Such investigations allowed for exploring the arrangement of the material microstructure as well as its mechanical response under applied loading. A comparison between DEM simulations and the experiment of particle breakage showed that 200 kPa should be considered as critical normal stress for soybeans. Finally, parametric studies were conducted to highlight the variation in the local and macroscopic properties of the particulate system as a function of inter-microscopic parameters of soybeans.