基于离散元法的稻麦周年地区土壤仿真物理参数标定

Parameter calibration of soil particles in annual rice-wheat region based on discrete element method

为获得可用于稻麦周年地区土壤流动的离散元仿真模拟参数,该研究利用EDEM中Hertz-Mindlin with EEPA接触模型对稻麦周年地区黏重土壤进行相关参数标定,以土壤材料参数(土壤颗粒间静摩擦系数、恢复系数、动摩擦系数、土壤剪切模量及土壤泊松比)和接触模型参数(黏附力强度、接触黏附能和接触塑性比)为标定对象,以室内试验及不同参数组合下仿真得到的土壤休止角为响应值,基于响应面优化标定土壤离散元仿真参数。研究应用Plackett-Burman试验对8个初始参数进行筛选,发现土壤—土壤静摩擦系数、动摩擦系数以及接触黏附能对颗粒堆休止角影响显著。在通过最陡爬坡试验确定显著性参数最优值区间的基础上,根据Box-Behnken试验结果建立休止角与显著性参数的二阶回归模型并对其进行优化,得到显著性参数的最佳组合为:土壤颗粒间静摩擦系数0.35、动摩擦系数0.23及接触黏附能3.78 J/m 2、土壤剪切模量10 MPa、土壤颗粒间恢复系数0.2、土壤泊松比0.2;黏附力强度-0.001 N、接触塑性比0.5。以最优水平组合进行仿真验证试验,验证结果与室内测试结果进行对比验证,二者相对误差仅为1.9%,标定所得的参数可为稻麦周年地区作业条件下的农业机械触土部件设计与优化提供基础数据。

In order to obtain discrete element simulation parameters that can be used for the soil in the annual rice-wheat area,the study used Hertz-Mindlin with EEPA contact model in EDEM to calibrate the relevant parameters of the clayey soil in the rice-wheat annual area.Taking soil material parameters(static friction coefficient between the soil particles,recovery coefficient,dynamic friction coefficient,shear modulus and poisson s ratio)and contact model parameters(adhesion strength,contact adhesion energy,contact plasticity ratio)as the calibration objects,with the indoor experiment and simulation under different parameter combinations of wheat grain heap in response to the angle of value,the soil discrete element simulation parameters were optimized and calibrated based on response surface.It was applied the Plackett-Burman experiment to screen 8 initial parameters,and found that the soil and soil static friction coefficient,dynamic friction coefficient and contact adhesion energy had significant effects on the angle of repose of the particle pile.On the basis of determining the optimal value interval of the significance parameters through the steepest uphill experiments,a second-order regression model of the angle of repose and the significant parameters was established and optimized according to the Box-Behnken test results.The best combination of the significant parameters was obtained as follows:static friction coefficient between the soil particles was 0.35,dynamic friction coefficient between soil particles was 0.23,contact adhesion energy was 3.78 J/m 2,shear modulus was 10 MPa,recovery coefficient between the soil particles was 0.2,poisson s ratio was 0.2;adhesion strength was-0.001 N and contact plasticity ratio was 0.5.Compared with the indoor test results,the relative error was only 1.9%.The calibration parameters can provide basic data for the design and optimization of agricultural machinery soil touching parts under the working conditions of rice wheat anniversary area.