DISCRETE ELEMENT SIMULATION CALIBRATION OF CONTACT PARAMETERS FOR MILLET SEEDS

In order to obtain accurate contact parameters for foxtail millet seeds in discrete element method (DEM) simulations, this study selected the Jinmiao K10 variety as the research object. Physical experiments and DEM simulations were integrated to calibrate the contact parameters. First, the restitution coefficient, static friction coefficient, and rolling friction coefficient between foxtail millet seeds and polylactic acid (PLA) material were measured using methods such as free-fall and inclined plane tests. Subsequently, based on the experimentally measured repose angle of 21.93°, a Plackett–Burman design was employed to screen the key parameters significantly influencing the repose angle. These included the inter-seed static friction coefficient, rolling friction coefficient, and restitution coefficient. The steepest ascent test was then conducted to determine the direction of parameter optimisation. A quadratic regression model was established using the Box–Behnken response surface methodology to determine the optimal combination of contact parameters: restitution coefficient of 0.512, static friction coefficient of 0.22, and rolling friction coefficient of 0.041. These parameters were imported into EDEM software for simulation validation. The simulated repose angle is 22.2°, with a relative error of 1.23%, demonstrating high accuracy and practical applicability of the calibrated parameters. This study provides reliable simulation parameter support for the design and optimization of critical components in foxtail millet seeding machinery.