Authors

Abstract

The rolling friction coefficient is a fundamental parameter for particle modeling, but it is challenging to quantify for unevenly shaped maize seeds. If the rolling friction coefficients of maize with different guiding seeds and different shapes are not believed to be significantly different, direct simulation in EDEM will produce simulation distortion. This paper began by selecting three models with a relatively high proportion from five corn samples with various shapes (such as horse-tooth shape, spherical shape, oblate shape, and irregular shape, etc.) and modeling them according to the actual seeds. Due to the large disparity between seed models with different shapes, the study adopted the method of combining physical experiment and discrete element simulation, took the rolling friction coefficient as the independent variable and the angle of repose in the simulation test as the target value, and calibrated the rolling friction of various shapes of corn seed particles separately. Coated corn seeds' rolling friction coefficients were accurately predicted (0.0047 for horse tooth, 0.0058 for pyramid, and 0.049 for spherical shape). During the validation test, the calibrated simulation parameters are entered into EDEM for simulation, and the distribution of seeds on the seed platter was compared between the actual test and the simulation test. The results demonstrated that the difference in the sizes of key features was less than 5.60 percent, and the population boundary in the seed platter after calibration was closer to the actual situation, which improved the simulation's accuracy.

Abstract in Chinese

滚动摩擦系数是进行颗粒模拟的基础参数，但对于形状不规则的玉米种子，滚动摩擦系数难以测量。如果不考虑模型形状的不同导种不同形状玉米之间的滚动摩擦系数有较大差异，直接在EDEM中进行仿真，会出现仿真失真的情况。针对此问题，本文首先从五种不同形状的玉米样品（如马齿形、球形、扁球形和不规则形状等）选出三种较为典型且占比较高的模型，根据实际种子进行建模。由于不同形状种子模型的差距较大，本文采用物理实验和离散元仿真结合的方法，以滚动摩擦系数为自变量，以仿真试验的休止角为目标值，将几种不同形状玉米种子颗粒的滚动摩擦进行了单独标定，详细预测包衣玉米种子的滚动摩擦系数(马齿形为0.0047、棱锥形为0.0058、类球形为0.049）。同时研究了包衣玉米种子滚动摩擦系数和颗粒形状对休止角形成过程的影响，提取了种群势能和平均速度，结果表明滚动摩擦系数可以改变种群流动性，增加玉米种子休止角形成的时间；玉米形状不同对休止角形成过程的作用不同，流动性较差马齿状可以很好的增加种子堆的高度和休止角，流动性较好的类球形则会增大堆积范围。在验证试验中，将标定的仿真参数输入EDEM中进行仿真，对比实际试验与仿真试验排种器内种子的分布情况，结果表明：关键特征尺寸数值差异在 5.6%以内标定后的排种器内种群的边界与实际情况更接近，提高了仿真的可靠性，为气力式玉米排种器离散元研究提供了理论依据。