Authors

Abstract

The millet threshing mixture is the primary material processed during post-combine cleaning operations and mainly comprises components such as seeds, millet panicle clusters, and short stalks. These components exhibit significant differences in material properties, which consequently affect cleaning efficiency. In this study, the morphological dimensions and mechanical parameters of each component in Longgu 31 millet threshing mixtures were systematically measured, including Poisson’s ratio, elastic modulus, shear modulus, angle of repose, static and dynamic friction coefficients, and the coefficient of restitution. The discrete element method (DEM) was employed to establish particle models for millet seeds, millet panicle clusters, and short stalks. Key contact parameters—namely static and dynamic friction coefficients and the coefficient of restitution—were calibrated using the Plackett–Burman design, the steepest ascent method, and the Box–Behnken response surface methodology. The results reveal substantial differences in the physical parameters among the components. The calibrated simulation values of the angle of repose show high consistency with experimental results, with an average error of less than 5%, thereby validating the reliability of the model and parameter system. The robust model and key parameters obtained in this study provide a solid data foundation for elucidating the mechanism of material motion during millet cleaning and for optimizing the design of cleaning and screening equipment. The findings also provide valuable references for simulation studies on the cleaning of small-particle-size minor grains.

Abstract in Chinese

谷子脱出物是联合收获后清选环节的主要研究对象，主要包含籽粒、谷码、短茎秆等成分，这些成分的物料特性差异显著，进而影响清选效率。本研究针对龙谷31号谷子脱出物，系统测定了各组分颗粒的形态尺寸和力学参数，包括泊松比、弹性模量、剪切模量、堆积角、静/动摩擦系数和碰撞恢复系数等。采用离散元方法建立谷子籽粒、谷码和短茎秆颗粒模型，并结合Plackett–Burman设计、最陡爬坡法与Box–Behnken响应面法对关键接触参数（静/动摩擦系数和碰撞恢复系数）进行反演标定。结果表明，各组分的物理参数存在明显差异；标定后的仿真堆积角与物理试验结果高度一致（平均误差<5%），验证了模型及参数体系的可靠性。本研究所获得的关键参数和可靠模型为揭示谷子清选过程物料运动机理和清选筛分装置的优化设计提供了坚实的数据基础，对小粒径杂粮清选仿真研究具有重要参考价值。