桑园土壤非等径颗粒离散元仿真模型参数标定与试验  

Calibration Method of Contact Characteristic Parameters of Soil in Mulberry Field Based on Unequal-diameter Particles DEM Theory

作　　者：宋占华[1,2] 李浩 闫银发 田富洋[1,3] 李玉道 李法德[1,2] SONG Zhanhua;LI Hao;YAN Yinfa;TIAN Fuyang;LI Yudao;LI Fade(College of Mechanical and Electronic Engineering,Shandong Agricultural University,Taian 271018,China;Shandong Province Key Laboratory of Horticultural Machineries and Equipments,Taian 271018,China;Shandong Engineering Laboratory of Agricultural Equipment Intelligence,Taian 271018,China;National Engineering Research Center for Agricultural Production Machinery and Equipment,Taian 271018,China)

机构地区：[1]山东农业大学机械与电子工程学院,泰安271018 [2]山东省园艺机械与装备重点实验室,泰安271018 [3]山东省农业装备智能化工程实验室,泰安271018 [4]农业生产机械装备国家工程研究中心,泰安271018

出　　处：《农业机械学报》2022年第6期21-33,共13页Transactions of the Chinese Society for Agricultural Machinery

基　　金：财政部和农业农村部:国家现代农业产业技术体系项目(CARS18ZJ0402);山东省现代农业产业技术体系建设项目(SDAIT1806)。

摘　　要：为获取土壤离散元仿真模型的土壤颗粒物理参数和接触参数,本文采用试验与仿真相结合的方法,以桑园土壤为例,对土壤颗粒的接触参数进行了仿真标定。首先利用粉体仪、斜面仪、等应变直剪仪等,分析了试验地不同深度土壤的粒径分布,测量了试验地不同深度土壤休止角、滑动摩擦角、剪应力、内聚力、内摩擦角;然后,根据实测土壤粒径分布,利用EDEM软件建立了非等直径土壤球形颗粒模型。在此基础上,以土壤颗粒间及土壤与65Mn钢间的静摩擦因数、滚动摩擦因数、恢复系数为试验因素,土壤休止角、土壤65Mn钢滑动摩擦角为目标值,建立了基于中心组合试验设计(CCD)方案,并利用Design-Expert软件对仿真试验结果进行了分析,得到了仿真标定的土壤土壤间静摩擦因数、滚动摩擦因数和恢复系数的最优值分别为0.89、0.45和0.43;标定的土壤65Mn钢间静摩擦因数、滚动摩擦因数和恢复系数的最优值分别为1.15、0.05和0.4。利用以上标定的最优参数对桑园土壤进行了休止角与滑动摩擦角仿真试验,试验结果表明,休止角仿真值与试验值相对误差为1.69%,土壤65Mn钢的滑动摩擦角仿真值与试验值相对误差为2.88%。在此基础上,依据实测的土壤剪应力,采用试错法,以实测土壤内摩擦角为目标值,优化标定了土壤土壤颗粒HertzMindlin with Bonding接触模型中的粘结参数,标定法向粘结刚度、切向粘结刚度分别为1×10^(8)、5×10^(7) N/m^(3),临界法向应力和临界切向应力均为10 kPa,接触半径为1.1倍颗粒半径,直剪仿真得到内摩擦角为30.24°,仿真值与直剪试验内摩擦角平均值相对误差为5.53%。本文提出的土壤颗粒建模方法、标定方法及其所标定的参数值,可用于砂质壤土桑园耕作机械触土部件与土壤相互作用的离散元仿真分析及其结构优化。To obtain the physical parameters and contact parameters of discrete element modelling(DEM)for simulating soil and interaction between soil and soil-engaging components in mulberry field,a method combining the experiments and the DEM simulations for calibrating the contact parameters of soil particles in mulberry field was proposed.Firstly,the particle size distribution and physical parameters of soil,such as the angle of repose of soil,sliding friction angle of soil and 65Mn steel,shear stress of soil,cohesion and angle of internal friction of the soils sampled at different depths in the mulberry field,were measured respectively with the powder instrument,inclinometer and equal strain direct shear apparatus.Then an unequal-diameter sphere particles model was built according to the measured particle size distribution by using the EDEM.On this basis,the coefficient of the static friction,coefficient of rolling friction and coefficient of restitution between soil particles and between soil and 65Mn steel were used as test factors,and the angle of repose of soil and the sliding friction angle between the soil and 65Mn steel were used as target values to construct a central combined experimental design(CCD)scheme(three factors and five levels).Subsequently,by analyzing with the Design-Expert software,the simulated optimum values of the coefficient of static friction,coefficient of rolling friction and coefficient of restitution between soils were calibrated to be 0.89,0.45 and 0.43,respectively;the simulated optimum values of coefficient of static friction,coefficient of rolling friction and coefficient of restitution between soil and 65Mn steel were calibrated to be 1.15,0.05 and 0.4,respectively.The simulation experiments for verifying the values of the angle of repose of mulberry field soil and the sliding friction angle between the mulberry field soil and 65Mn steel were performed with the simulated parameters such as the coefficient of static friction,coefficient of rolling friction as well as coefficient of res

关 键 词：桑园土壤 仿真模型 离散元法 参数标定 非等直径球形颗粒 

分 类 号：S223.92[农业科学—农业机械化工程]