摘要
为更好地模拟小麦籽粒(麦粒)振动筛分过程,该文在现有离散元接触模型基础上,通过EDEM软件应用程序编程接口,构建了一种麦粒黏弹塑性接触模型。该接触模型法向方向通过将Kuwabara and Kono非线性黏弹性接触模型中的黏性耗散项引入Thornton滞回接触模型进行构建;切向方向采用简化Thornton切向接触模型;滚动摩擦力矩计算同Hertz-Mindlin(no slip)接触模型。法向模型参数标定采用单轴加载-卸载试验、碰撞试验,分别构建了模拟-试验接触力误差平方和与麦粒屈服重叠量、恢复系数与法向阻尼系数的二阶回归方程,得到麦粒屈服重叠量为7.63×10-6 m,麦粒-麦粒/钢板法向阻尼系数分别为190.68和306.65。切向模型参数利用旋转鼓试验进行标定,得到最佳麦粒-麦粒/钢板静摩擦系数组合为0.40和0.44。最后利用振动筛分试验对所标定参数进行验证,模拟与试验所得筛下麦粒质量分数最大误差为8.97%,模拟中筛下物分布规律与试验结果无显著性差异,表明所建立的接触模型及标定的参数能够很好地模拟麦粒振动筛分过程。该文也可为其他农业物料黏弹塑性接触模型构建及其参数标定提供参考。
In order to better simulate the screening process of wheat,a visco-elasto-plasticity contact model was constructed based on the existing discrete element method(DEM)contact model.The modelling process was based on the application programming interface(API)of the EDEM 2.7 software,which allowed users to create customized contact model,particle factory and coupling interface by the C++programming language.The normal contact model was created by adding the viscous dissipation term of the Kuwabara and Kono non-linear viscoelasticity model to the Thornton hysteretic model.The simplified Thornton tangential model was used to calculate the tangential force and the calculation of rolling friction was the same as that used in the Hertz-Mindlin(no slip)model.The calibration of the parameters of the visco-elasto-plasticity contact model was based on a uniaxial loading-unloading test,collision test and rotating drum test.Specifically,the uniaxial loading-unloading test was conducted to determine the yield overlap of wheat as the loading rate was slow(1 mm/min)and it could be regarded as a quasi-static process in which the viscous dissipation term can be neglected.In this work,the sum of squared errors of the contact force at all sampling points was calculated and the regression equation was developed,representing the relationship between the sum of squared errors of the contact force and the yield overlap of wheat.The result showed that the difference between the experimental and simulated values was the least when the yield overlap was 7.63×10-6 m.Then the wheat-wheat/steel collision tests were respectively conducted to calibrate the wheat-wheat/steel coefficients of viscidity as the coefficient of restitution measured in these collision tests can reflect the energy dispassion of collision.Specifically,the double-pendulum test was used to calibrate wheat-wheat coefficient of viscosity and the inclined plate test was used to calibrate wheat-steel coefficient of viscosity.The regression equations describing the relationship
作者
刘凡一
张舰
陈军
Liu Fanyi;Zhang Jian;Chen Jun(College of Mechanical and Electronic Engineering,Northwest A&F University,Yangling 712100,China)
出处
《农业工程学报》
EI
CAS
CSCD
北大核心
2018年第15期37-43,共7页
Transactions of the Chinese Society of Agricultural Engineering
基金
高等学校博士学科点专项科研基金(20130204110020)
关键词
计算机仿真
模型
农作物
离散元
小麦籽粒
黏弹塑性
接触模型
参数标定
computer simulation
models
crops
discrete element method
wheat
visco-elasto-plasticity
contact model
parameters calibration
