收获期菊芋根-块茎离散元柔性模型研究

目前，菊芋机械化收获过程中的清选及输送等环节作业参数设定缺乏适用的理论依据，以收获期菊芋根-块茎为研究对象，基于离散元方法建立了一种能反映根须柔性和块茎脱落力学特性的粘结模型并对其相关参数进行了标定。首先通过物理试验确定了菊芋根-块茎本征参数、基本接触参数及相关力学参数，然后在此基础上利用Hertz-Mindlin with bonding V2接触模型构建了菊芋根-块茎粘结模型，并通过单因素试验和响应曲面试验，分别标定了菊芋根颗粒之间和根与块茎颗粒之间法向粘结刚度、切向粘结刚度、临界法向应力、临界切向应力等粘结模型参数。菊芋根须三点弯曲及根-块茎拉伸试验结果表明，根须弯曲弹性模量仿真结果与实际测量值相对误差为4.29%;菊芋根-块茎抗拉力仿真结果与实际测量值相对误差为7.72%;菊芋块茎脱落试验结果表明，仿真试验与菊芋收获机实际田间作业相比，滚筒筛转速对菊芋块茎脱落率影响趋势一致，筛内物料筛分规律相符。所构建的菊芋根-块茎模型可用于菊芋机械化收获相关环节的分析研究。

Construction of Discrete Element Flexible Model for Jerusalem Artichoke Root-Tuber at Harvest Stage

Currently, there is a lack of theoretical basis for setting operational parameters such as cleaning and conveying Jerusalem artichoke tubers during mechanical harvesting. A bonding model that reflected the root flexibility and tuber detachment mechanical characteristics was established by using the discrete element method, and its relevant parameters were calibrated. In the first step, the intrinsic, basic contact and associated mechanical parameters were determined through laboratory experiments. Next, based on these parameters, Hertz-Mindlin with bonding V2 contact model and Meta particle function was used to establish the flexible model for Jerusalem artichoke root-tuber. Single-factor experiment and response surface methodology were used to determine the bonding parameters such as normal stiffness, tangential stiffness, normal strength, and tangential strength between Jerusalem artichoke root particles and between root and tuber particles. Subsequently, the three-point bending and root-tuber tensile simulation experiments were carried out on the determined parameters. The error between the simulation results and the physical experiment values of the root flexural modulus was 4.29%. The error between the simulation results and the physical experiment values of the maximum allowable tensile resistance between the root and tuber was 7.72%. Finally, the calibrated model was used to simulate the Jerusalem artichoke tuber harvesting operation. The effect of drum screen rotary speed on the tuber shedding rate in the simulation and field experiments had a similar trend. The research demonstrated that the method used to establish the model was correct, and the calibration parameters were deemed reliable. As a result, the established Jerusalem artichoke root-tuber flexible model can be effectively employed for further simulation research pertaining to the mechanized harvesting process of Jerusalem artichokes.