Discrete element modelling of citrus fruit stalks and its verification

A discrete element model of citrus fruit stalk with a diameter of 3 mm was established using the discrete element method (DEM). The intrinsic parameters and contact parameters of citrus fruit stalk were obtained through measurement. The bonding parameters of the discrete element model of citrus fruit stalk were calibrated through a three-point bending test and shear tests. Based on these parameters, the optimal bonding parameter combination was determined. This included: normal stiffness per unit area 4.6362×1011N m−3, shear resistance 1.2549×1011N m−3, bonded disc radius 0.222 mm, critical normal stress 9.5742×107Pa and maximum shear stress 7.4007×107Pa. These optimal parameters were applied to simulate the bending and shearing of a citrus fruit stalk using the established citrus fruit stalk model. Compared to experimental results, the deviation of bending strength and shear peak force were 1.25% and 1.78%, respectively. The results show that a DEM of citrus fruit stalk established can be used to properly simulate the bending and shearing of citrus fruit stalks and that the method of calibrating the parameters for accuracy is reasonable. The results are significant for the study of the mechanical properties of citrus fruit stalks and the optimisation of end-effectors of harvesting robots.