Authors

Abstract

The shear mechanical properties of corn stubble are fundamental to the design of high-efficiency crushing and stubble management equipment. However, the combined effects of moisture content and loading speed on these properties remain insufficiently characterized. In this study, maize root stubble (cv. ‘Heyu 23’) samples were collected and subjected to shear tests using a DDL 300 electronic universal testing machine under three moisture content levels (50–80%) and four loading speeds (5–50 mm/min), with 10 replicates per condition (total n = 120). The coefficient of variation (CV) ranged from 17.6% to 42.3%, indicating moderate to high variability depending on the test conditions. The shear stress exhibited a nonlinear, moisture-dependent response. The maximum shear stress (2.17 MPa) occurred at high moisture content (70–80%) and a medium loading speed (20 mm/min), while the minimum value (1.26 MPa) was observed at moderate moisture content (60–70%) and a low loading speed (10 mm/min). A critical moisture threshold of approximately 65% (fiber saturation point) was identified, below which brittle behavior dominates, and above which viscoelastic and lubricating effects prevail. These findings provide quantitative support for the design and operational parameter optimization of maize root stubble crushing equipment, particularly for cutting–kneading combined mechanisms and bionic stubble cutters.

Abstract in Chinese

玉米秸秆的剪切力学性能是高效粉碎和秸秆处理设备设计的基础。然而，含水率和加载速度对这些性能的综合影响仍缺乏充分的研究。在本研究中，采集了玉米秸秆（品种为和玉23）样本，并使用DDL - 300电子万能试验机进行了剪切试验。研究了三个含水率组（50% - 60%、60% - 70%和70% - 80%）和四种加载速度（5、10、20和50毫米/分钟），每个条件重复10次（共计120个样本）。变异系数（CV）范围为17.6%至42.3%，其中在含水率为70% - 80%、加载速度为10毫米/分钟时变异系数最小（17.6%），表明重复性最高；在含水率为60% - 70%、加载速度为50毫米/分钟时变异系数最大（42.3%），表明稳定性最差。剪切应力呈现出与含水率相关的非线性响应。最大剪切应力（2.17兆帕）出现在含水率为70% - 80%、加载速度为20毫米/分钟时，而最小剪切应力（1.26兆帕）出现在含水率为60% - 70%、加载速度为10毫米/分钟时。研究确定了一个临界含水率阈值，约为65%（纤维饱和点），低于该阈值时，秸秆表现出脆性特征；高于该阈值时，粘弹性和润滑效应占主导。这些研究结果为玉米秸秆粉碎设备的设计和运行参数优化提供了定量基准，特别是对于切割揉搓组合机构和仿生秸秆切割器。