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 × 10 11 N m−3, shear resistance 1.2549 × 10 11 N m−3, bonded disc radius 0.222 mm, critical normal stress 9.5742 × 10 7 Pa and maximum shear stress 7.4007 × 10 7 Pa. 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.

中文翻译：

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柑桔茎秆离散元建模及其验证

采用离散元法(DEM)建立了直径为3 mm的柑桔茎秆离散元模型。通过测量得到柑桔茎秆的内在参数和接触参数。通过三点弯曲试验和剪切试验对柑桔茎秆离散元模型的粘结参数进行标定。基于这些参数，确定了最佳粘合参数组合。这包括：单位面积法向刚度 4.6362 × 10 11 N m-3，抗剪强度 1.2549 × 10 11 N m-3，粘合盘半径 0.222 mm，临界法向应力 9.5742 × 10 7 Pa 和最大剪应力 7.4007 × 10 7 Pa. 使用已建立的柑橘类水果茎模型，应用这些最佳参数来模拟柑桔类水果茎的弯曲和剪切。与实验结果相比，弯曲强度和剪切峰值力的偏差分别为1.25%和1.78%。结果表明，建立的柑桔茎秆DEM可以较好地模拟柑桔茎秆的弯曲和剪切，参数标定方法的准确性是合理的。研究结果对柑桔茎秆力学特性研究及采摘机器人末端执行器优化具有重要意义。