Authors

Abstract

Buckwheat crops are subjected to complex stress during harvest. And there are problems such as large deformation, severe brokenness, and high energy consumption of stems during the mechanical harvesting, such as cutting, transporting, threshing, separating and cleaning. In this study, the mechanical properties of buckwheat stem during mechanical harvesting were tested, including tensile, bending, shearing and dynamic cutting, and the effects of moisture content, stem position and working parameter on their mechanical properties were analyzed. The test results showed that the tensile strength, elastic modulus, cutting stress and unit area cutting energy of stem with higher moisture content were significantly greater than those of stem with lower moisture content (P<0.05). The flexural modulus and bending strength of stem with higher moisture content were significantly lower than those of stem with lower moisture content (P < 0.05). The flexural modulus, bending strength, shear strength, cutting stress and unit area cutting energy decreased gradually with the stem height increasing. The cutting parameters had significant effects on the mechanical properties of stem (P<0.05), and the cutting mechanical properties first decreased and then changed steadily with the average cutting speed increasing. The cutting stress gradually decreased with the blade oblique angle increasing, but the unit area cutting energy decreased first and then increased. The average cutting speed and blade oblique angle of buckwheat stem are recommended to be 0.75-1.0 m/s and 30o, respectively. This research can provide basic data for the design of the buckwheat harvesting machinery.

Abstract in Chinese

荞麦作物在机械收获拨禾、扶禾、切割、输运、脱粒分离、清选和秸秆回收等作业环节，其茎秆会受到复杂应力作用，存在茎秆受力变形大、破碎严重、耗能大等问题。本文测试了荞麦茎秆在机械收获过程中的力学性质，包括拉伸、弯曲、剪切和动态切割力学性质，并分析了含水率、茎秆部位和相关工作参数对其力学性质的影响。试验结果表明：较高含水率的荞麦茎秆拉伸强度、弹性模量、切割应力和单位面积切割功耗均显著大于较低含水率的荞麦茎秆（P＜0.05）；但较高含水率的荞麦茎秆弯曲模量和抗弯强度显著小于较低含水率的荞麦茎秆（P＜0.05）。随着茎秆离地高度的增大，其弯曲模量、抗弯强度、剪切强度、切割应力和单位面积切割功耗均逐渐减小。切割工作参数（平均切割速度和刀片斜角）对荞麦茎秆的切割应力、单位面积切割功耗影响显著（P＜0.05），随着平均切割速度的增大，切割力学性质参数呈现先减小后平稳变化的规律，而随着刀片斜角的增大，切割应力逐渐减小，而单位面积切割功耗先减小后增大，荞麦茎秆的平均切割速度和刀片斜角建议分别选取0.75-1.0 m/s和30°。本研究不仅为荞麦机械收获茎秆-机械耦合作用规律提供了测试手段，也为荞麦低损高质收获机械关键部件设计提供了基础数据。