包衣棉种物性参数测定与离散元仿真参数标定

Measurement of the physical parameters and calibration of discrete element simulation parameter of coated cotton seed

关键词:  包衣棉种  物性参数  离散元  参数标定

Key words:  coated cotton seed  physical parameters  discrete element  parameter calibration

摘要:

针对目前在EDEM(离散元法)中直接建立的棉种颗粒模型与实际棉种在外形上存在一定差异，且缺乏准确的包衣棉种仿真参数的问题，采用物理试验方法测定‘新陆中67号’棉种的基本物理力学参数，研究包衣对棉种与有机玻璃板间的接触参数(碰撞恢复系数、静摩擦因数和滚动摩擦因数)的影响，基于逆向工程技术建立棉种离散元颗粒模型，运用响应曲面分析法建立包衣棉种种间接触参数与休止角相对误差的二阶回归模型，结合物理试验和仿真试验对仿真参数进行标定，确定包衣棉种种间碰撞恢复系数、静摩擦因数和滚动摩擦因数的最优参数组合，并利用棉花精密排种器排种试验对仿真参数进行验证。结果表明:‘新陆中67号’棉种的泊松比为0.27，剪切模量为14 MPa，包衣剂对棉种表面摩擦特性有一定影响，包衣棉种与有机玻璃之间的碰撞恢复系数、静摩擦因数和滚动摩擦因数分别为0.25、0.49和0.21，包衣棉种种间碰撞恢复系数、静摩擦因数和滚动摩擦因数分别为0.19、0.23和0.13，此最优参数组合下排种仿真试验与台架试验的合格率和漏播率相对误差均小于5%，包衣棉种离散元颗粒模型和仿真参数可用于离散元仿真模拟试验。

Abstract:

In view of the differences between the cotton seed particle model directly based on EDEM and the actual cotton seed shape and the lacking of the simulation parameters, the basic physical parameters of Xinluzhong No. 67 cotton seed and contact parameters between cotton seed and plexiglass plate were determined by physical test methods. Reverse engineering technology was used to establish the discrete element model of cotton seed. The quadratic regression model of repose angle relative error and contact parameters between coated cotton seeds was established by response surface analysis method. Combined with physical experiment and simulation experiment, the contact parameters between coated cotton seeds were calibrated to determine the optimal contact parameters of simulation experiment in EDEM software. Verification tests with calibrated contact parameters were carried out by the cotton precision seeding device. The results showed that: The Poisson's ratio and the shear modulus of Xinluzhong No. 67 cotton seed were 0. 27 and 14 MPa, respectively. The surface friction characteristics of cotton seed were affected by seed coating agent. The static friction coefficient, rolling friction coefficient and restitution coefficient between coated cotton seed and plexiglass plate were 0. 49, 0. 21 and 0. 25, respectively. The restitution coefficient, static friction coefficient and rolling friction coefficient between coated cotton seeds were 0. 19, 0. 23 and 0. 13, respectively. Under the optimal simulation parameters combination, the relative error of qualified index and missing index were both less than 5%. The model and contact parameters of coated cotton seed explored in this study could provide a reference for the discrete element simulation experiment.