Calibration and Experimental Validation of DEM Rolling Friction Parameters for Peanut Seeds Classified by Pod Position

A single rolling friction coefficient in discrete element method (DEM) simulations cannot represent differences in rolling resistance among morphology-based peanut seed classes. After shelling, Silihong peanut seeds were classified as upper, middle, or lower based on seed-shape features associated with compression by neighboring seeds. Physical and contact properties were measured, and multi-sphere models were constructed using class-specific geometries and a common geometry based on dimensions weighted by a prescribed 1:2:1 seed-number ratio. Calibration against the measured static angle of repose of 22.280° yielded a baseline seed–seed rolling friction coefficient of 0.02552; rerunning the simulation with this coefficient reproduced the calibration target with a relative error of 0.485%. Shape corrections derived from aspect ratios and single-seed critical angles were 1.1046, 0.9687, and 0.9579, giving class-specific coefficients of 0.02819, 0.02472, and 0.02445 while preserving their weighted mean. At a drum speed of 15 r/min, the three particle models produced similar overall dynamic angles of repose. Coupled simulations yielded qualified, multiple, and missed seeding indices of 92.2%, 6.7%, and 1.1%, respectively, close to the bench-test values; all three mean indices met the cited technical requirements. The parameter set and calibration procedure provide a case-specific reference for the tested Silihong seed batch, particle representation, moisture content, and metering conditions.