玉米根系离散元模型建立及仿真参数标定研究

Study on Establishment of Discrete Element Model of Maize Root System and Calibration of Simulation Parameters

为研究秸秆饲料收获机工作时玉米根土复合体受力变化情况,利用离散元法建立了整根玉米根系颗粒粘结模型。根据玉米根系物理特性,选取Hertz-Mindlin with Bonding颗粒接触模型;为准确获取离散元仿真参数,采用根系剪切试验与离散元仿真相结合的方法,对离散元参数进行标定。以根系峰值剪切力为响应值,采用Design Expert软件依次设计Plackett-Burman试验、最陡爬坡试验与Box-Behnken试验,得到最优仿真参数,即颗粒间剪切模量为6.6MPa、粘结刚度为1.139×10^(6)N/m^(3)、极限应力为1.1885MPa。结果表明:仿真值与实际值相对误差为2.12%,仿真标定结果真实可信。最终,根据根系实际尺寸,采用颗粒快速填充方法建立整根玉米根系模型,旨在为后续秸秆饲料收获机械离散元仿真提供参考依据。

In order to study the force change of the corn root-soil complex when the straw forage harvester is working,a discrete element method was used to establish the whole corn root particle adhesion model.According to the physical characteristics of the corn root system,the Hertz-Mindlin with Bonding particle contact model was selected.In order to accurately obtain the discrete element simulation parameters,the method of combining the root shear test and the discrete element simulation was used to calibrate the discrete element parameters.Taking the root peak shear force as the response value,the Plackett-Burman test,the steepest climbing test and the Box-Behnken test were sequentially designed using Design Expert software to obtain the optimal simulation parameters:the inter-particle shear modulus is 6.6 MPa,and the bonding stiffness is 1.139×10^(6)N/m^(3),and the ultimate stress is 1.1885 MPa.After experimental verification,the relative error between the simulated value and the actual value is 2.12%,which indicates the feasibility of simulation calibration.Finally,according to the actual size of the root system,a rapid particle filling method was used to establish the whole root corn root system model,which provides a reference for the subsequent discrete element simulation of the straw and feed harvesting machinery.