摘要
玉米种子的滚动摩擦系数是排种器设计计算和仿真分析的重要依据,但其测量目前尚无成熟的理论与方法。该文基于能量守恒原理,借助高速摄像技术对玉米种子与有机玻璃、镀锌钢板以及玉米种子间的滚动摩擦特性进行了试验研究,得到玉米种子与有机玻璃、镀锌铁板以及玉米种子间的滚动摩擦系数分别为0.0931、0.0531和0.0782。通过玉米种子休止角试验和离散元分析软件EDEM仿真结果的对比,对所得试验数据进行了验证,结果表明所得数据准确性较高,可为排种器的设计计算与仿真分析提供理论依据。
The physical properties of corn seeds, including the dimension feature, density, Poisson’s rate, shear modulus, coefficient of restitution, coefficient of static fraction, and coefficient of rolling fraction are vital to the design of the precision seed-metering device and the simulation of its working process. There have been many relative studies on them, but no mature theory and accurate method to measure the coefficient of rolling friction has been developed. Due to the shape and dimension character limitation, most methods for measuring the coefficient of rolling fraction are not applicable to corn seed. Only one method based on the principle of conservation of energy gave some enlightenment on the way to achieve it. The method and principle used to obtain the coefficient of rolling friction was： A static spherical corn seed rolls from the top of an inclined rail to the end. The gravitational potential energy （U） of the seed on the top is equal to the kinetic energy at the end （Ek ） and the work done by the rolling friction within this distance （Wfr ）. And the ratio of Wfr and U （ Cf= Wfr/U） has a linear relation with cotθ （θ is the angle of the inclined rail）. The equation of linear regression can be fitted by changing θ eight times from 15°to 50°, the slop of the straight line just is the coefficient of rolling friction. U can be calculated by the distance of the inclined rail and θ easily, but E k needs the aid of high-speed photography technology to capture the velocity of the seed at the end. The experimental materials included several selected spherical corn seeds that were used as roll ball, an angle adjustable frame of rail, and three rails which were made of the PMMA （polymethyl methacrylate）, galvanized steel, and corn seeds respectively. The main testing equipment was the Phantom v9.1 high-speed camera, which was produced by Vision Research. The frame rate used in the experiment was 1 000 fps. According to the results of the experiment, the coefficient of rolling friction of corn seeds against PMMA （polymethyl methacrylate）, galvanized steel, and corn seeds are known as 0.0931, 0.0531 and 0.0782 respectively. Although there were some inevitable errors caused by the materials and image processing method for getting the velocity, the results were proved to be truthful by the contrast tests about the angle of repose for corn seeds both by laboratory tests and EDEM simulation. The data measured can be used for design calculation and simulation analysis.
出处
《农业工程学报》
EI
CAS
CSCD
北大核心
2013年第15期34-41,共8页
Transactions of the Chinese Society of Agricultural Engineering
基金
玉米机械化生产工艺与装备系统优化研究与示范项目(200903059)
"十二五"国家科技支撑计划资助项目(2011BAD20B09)
国家现代玉米产业技术体系建设项目(CARS-02)
农业部土壤-机器-植物系统技术重点实验室资助项目
关键词
种子
试验
仿真分析
摩擦
高速摄像
EDEM
玉米
seed
experiments
computer simulation
friction
high-speed photography
EDEM
corn
