基于离散元法的椰糠颗粒建模及仿真参数标定

为确定椰糠在离散元模拟过程中合理的仿真参数,本文基于离散元法Hertz-Mindlin（no slip）接触模型在仿真软件EDEM 2018中建立椰糠颗粒模型并生成颗粒工厂,通过测量比对物理试验和仿真试验椰糠堆积角的方法对其仿真参数进行标定。首先通过物理试验测得椰糠堆积角、堆积密度等本征参数,利用EDEM 2018内嵌GEMM数据库以及相关文献,综合分析得到椰糠待标定因素的高低水平;然后进行Plackett-Burman试验设计筛选出对椰糠堆积角影响显著的因素依次为：椰糠-椰糠静摩擦系数、椰糠-椰糠滚动摩擦系数和椰糠剪切模量;再进行Box-Behnken试验设计建立堆积角与3个显著性影响因素的回归模型,运用Design expert软件优化功能,以堆积角物理试验45.69°为目标,对回归方程寻优求解,得到显著性影响因素最佳组合：椰糠剪切模量为1.44 MPa,椰糠-椰糠静摩擦系数为1.11,椰糠-椰糠滚动摩擦系数为0.15;最后通过试验验证表明此组合参数可用于椰糠物料的离散元仿真,能为椰糠输送、混合等机械装备的设计研发提供理论参考。

Modeling and Simulation Parameters Calibration of Coconut Coir Particles Based on DEM

In order to determine the reasonable simulation parameters of coconut coir in the DEM process, based on the DEM Mindlin (no slip) contact model, a coconut coir model is established in the simulation software EDEM 2018 and the particle factory is generated. The simulation parameters were calibrated by comparing the physical test and virtual test of coconut coir repose angle. Firstly, the intrinsic parameters of coconut coir such as repose angle and bulk density were measured by physical tests, and the level of factors to be calibrated were obtained by comprehensive analysis using the GEMM database embedded in EDEM 2018 and relevant literature. A Plackett-Burman test design was carried out to screen out the factors that have significant influence on the repose angle of coconut coir: static friction coefficient of coconut coir with coconut coir, rolling friction coefficient of coconut coir with coconut coir, shear modulus of coconut coir. Through Box-Behnken experimental design, a regression model of repose angle and three significant influencing factors were established, using the optimization function of design expert software, taking the physical test of stacking angle of 45.69° as the objective, the regression equation was optimized and solved, and the best combination of significant influencing factors were obtained. Coconut coir shear modulus was 1.44 MPa, static friction coefficient of coconut coir with coconut coir was 1.11, and rolling friction coefficient of coconut coir with coconut coir was 0.15. The experimental results showed that the combined parameters could be used in the discrete element simulation of coconut coir materials, and provide theoretical references for the design of coconut coir conveying, mixing and other mechanical equipment.