CALIBRATION OF THE DISCRETE ELEMENT PARAMETERS AND EXPERIMENTAL VERIFICATION OF THE OIL SUNFLOWER PLUG SEEDLING POTS

Abstract

The movement of plug seedlings and the pots damage mechanism are deeply studied during the planting process, and the planting components are optimized. The Tekscan pressure distribution measurement system was used to measure the mechanical characteristics of the drop impact between the whole plug seedlings and the pots. The relative error between the collision impact force of the plug seedlings and the collision impact force of the pot is less than 20%. Therefore, a drop impact test using the pot allows the whole plug seedling to be characterized. The Hertz-Mindlin with bonding model was used to build a simulation model of the pot based on essential physical parameters. The Plackett-Burman test and the steepest climbing test determined the significant parameters and optimal intervals affecting the collision impact force: the rolling friction coefficient between the pot and pot was 0.35~0.38, the bond stiffness was 0.2~0.6 MN·m-3, and the bond radius was 1.56~1.98 mm. Finally, the Box-Behnken test was performed and the quadratic regression model of the collision impact force was developed. Taking the collision impact force with a drop height of 350 mm as the target, the optimal solution is obtained: the rolling friction coefficient between the pot and pot was 0.35, the bond stiffness was 0.53 MN·m-3, and bond radius 1.97 mm. The average value was used for other insignificant influence parameters. The simulation results are compared with the physical test, and the relative error is 3.65%. Therefore, the pot model established by this simulation parameter can represent the actual drop impact of the pots.