Research on the constitutive model of low-damage corn threshing based on DEM

Abstract

The constitutive model of corn has an intense influence on the mechanical structure design and machine performance. In this paper, a creep property formula of corn-based on the Burgers model was proposed, which described the change process of the stress–strain trait of corn grain with time. Then, the mathematical model of the “corn-mechanical” interaction system was then established based on the Hertz-Mindlin no-slip model. The kinematic and dynamic formulas of corn ear under the action of threshers were deduced, and the “corn-corn” contact characteristics based on Hertz-Mindlin with bonding model were analyzed. Moreover, a new discrete element model construction method of the corn ear was proposed through particle filling and splicing methods. The simulation experiment was carried out in EDEM to verify the constitutive model and discrete element model of corn ear. The results showed that the particle filling model could better explain the mechanism of corn ear threshing and obtain the force of each corn grain during threshing. The average velocity of corn ear was 55.2 m/s, the maximum value was 216.7 m/s, and the minimum value was 16.2 m/s, while the average normal force was 201.7 N, the maximum force was 342.0 N, and the minimum force was 104.2 N respectively, it verified the feasibility and accuracy of models. Finally, the field experiment was carried out to verify the simulation results, and the corn grain broken rate was 2.16%. These results fill the blank of fundamental theoretical research on the design of corn ear threshing devices and provide a reference for the optimal design of other crop production equipment.