Calibration of Contact Parameters for Ruminant Protein Supplement Feed Pellets Based on the Discrete Element Method

To address the limited research on the material properties of ruminant protein supplement feed pellets and the lack of an accurate calibration framework for discrete element method (DEM) contact parameters, which constrained the optimization of related mechanical equipment, this study investigated the fundamental physical and contact characteristics of protein supplement pellets. A DEM-based particle model was established, and the angle of repose was selected as the evaluation index. The Plackett–Burman design was employed to identify the primary influencing factors, followed by a Steepest Ascent test and a Box–Behnken design to develop a regression model for parameter optimization and calibration. The results indicated that when the static friction coefficient, rolling friction coefficient, and restitution coefficient between particles were set to 0.52, 0.03, and 0.37, respectively, the restitution coefficient between particles and materials, as well as the static and rolling friction coefficients between particles, had significant effects on the angle of repose. The optimal parameter values were determined to be 0.45, 0.55, and 0.05, achieving the theoretical optimum. Validation experiments showed that the average deviation between the calibrated and measured angles of repose was 0.92%, demonstrating a high level of agreement between the simulated and experimental results. These findings provided a reliable theoretical reference and parameter basis for the optimization of processing, conveying, and key component design in ruminant protein supplement feed machinery.