Calibration of discrete element contact parameters for white radish seed particles

Feature parameters between the white radish seed particles and planting machinery were still lacking, particularly on the contact parameters between the white radish seed particles and mechanized planting machinery. Discrete element method（DEM） is widely used to simulate the key work process and provides a powerful theoretical reference for parameter calibration of solid particles and agricultural materials. Taking white radish seed particles as the research object, this study is aimed to establish a discrete element model using three-dimensional scanning reverse simulation in the EDEM software, and then to calibrate parameters of white radish seed particles through physical experiments and virtual simulation experiments. The collision restitution coefficient, static friction coefficient and rolling friction coefficient between the white radish seed particles and 4 different materials of ABS plastic, stainless steel plate, plexiglass and aluminum alloy were determined by collision bounce test, inclined plane slip test and inclined plane rolling test, respectively. These coefficients of restitution were 0.48, 0.62, 0.51, and 0.44, respectively. The coefficients of static friction were 0.50, 0.42, 0.45, and 0.48, respectively. The coefficients of rolling friction were 0.014, 0.025, 0.007, and 0.006, respectively. The multivariate quadratic equation was optimized with multiple objectives. The optimal combination of contact parameters of the discrete element model between white radish seeds was obtained. The collision recovery coefficient, the static friction coefficient and the rolling friction coefficient were 0.19, 0.54 and 0.02, respectively. The accumulation test of the physical angle of repose of white radish seed particles was carried out by the cylinder lifting method. MATLAB was used to carry out a gray-scale and binarization processing on these accumulation images of stacking angle, and these angles of repose of white radish seed particles and ABS plastic, stainless steel plate, plexiglass and aluminum alloy were 33.48°, 32.72°, 33.81°, and 29.88°, respectively. The angle of repose errors obtained by the simulation test and the physical test were 1.4%, 3.2%, 2.6% and 2.8%, respectively. These results showed that the discrete element simulation parameters obtained from the modeling and calibration of white radish seed particles were accurate and reliable, which could provide a theoretical reference for the discrete element simulation research of white radish seed particles.