Soybean Seed Characterization and Discrete Element Parameter Calibration for Harvesting Simulation

Mulched drip irrigation is an important water-saving production system for soybean cultivation in arid and semi-arid regions. However, soybean materials harvested from this system exhibit specific physical characteristics, including relatively dry pods and seeds and high stem moisture content. This study characterized the physical and mechanical properties of soybean seeds at the harvest stage and established a discrete element method (DEM) parameter system for harvesting simulation. Key properties and contact behaviors were experimentally measured, and DEM parameters were calibrated and validated through physical tests and virtual simulations. The results showed that the calibrated parameters accurately reproduced the macroscopic stacking behavior of soybean seeds, with the angle of repose validation showing a relative error of only 0.545%. The proposed parameter system considers the geometric and mechanical characteristics of harvest-stage soybean seeds and improves the applicability of DEM simulations for harvesting process analysis. This study provides digital support for optimizing soybean harvesting machinery, reducing seed damage, and improving harvest quality in water-efficient production systems.