Authors

Abstract

The key challenge in Brassica napus combine harvesting is achieving a balance between threshing rate and impurity rate, both of which are strongly influenced by stem breakage. This study investigated the breakage characteristics and static mechanical properties of Brassica napus stems from the middle and lower reaches of the Yangtze River using axial tensile tests combined with digital image correlation (DIC). The results showed that the fiber layer area of rapeseed stems increased with stem diameter, and stem breaking force was significantly positively correlated with stem diameter. For stem diameters ranging from 7 to 16 mm, the breaking force ranged from 166.82 to 970.82 N and was described by the relationship Fb=42.064dx1-92.894. The tensile strength of rapeseed stems ranged from 25.1 to 64.6 MPa, and a quadratic response surface model relating tensile strength to stem diameter and moisture content was established. DIC measurements of strain in the radial and axial orthogonal directions showed that axial deformation was substantially smaller than radial deformation, with an average axial strain of εy=4.22±2.23×10-3 and an average radial strain of εx=3.84±2.17×10-2. These findings improve the understanding of the mechanical response of rapeseed stems under tensile loading and provide a theoretical basis for optimizing threshing devices for efficient, low-damage rapeseed harvesting.

Abstract in English

油菜联合收割中的核心挑战是平衡物料的脱净率与破碎率，而这直接受到茎秆破碎程度的影响。本研究针对长江中下游地区的油菜植株，通过轴向拉伸试验配合数字图像相关技术，深入探讨茎秆的破碎条件和静态特性。研究结果显示，茎秆的屈服强度和抗拉强度与茎秆直径呈显著正相关，而水分含量对这些力学特性无明显影响。在直径为7至16 mm的茎秆中，屈服力介于166.82 N到619.92 N之间，其与直径的关系表达为：Fb=42.064dx1-92.894。抗拉强度范围为2.51 MPa至6.46 MPa，直径与抗拉强度的关系为：σb=0.0407dx12-1.2411dx1+12.566。使用数字图像技术对径向和轴向两个正交方向的应变进行测量，结果表明轴向变形显著小于径向变形，平均轴向应变为εy=4.22±2.23×10-3，径向应变为εx=3.84±2.17×10-2。这些结果不仅揭示了茎秆在受力过程中的机械响应规律，还为优化脱粒装置以实现高效低损伤的油菜籽收割提供了重要的理论依据。