基于工业CT的适收期水稻秸秆精细建模与失效机理分析

Fine Modeling and Failure Mechanism Analysis of Harvest-ready Rice Straw Based on Industrial CT

摘要:

针对传统几何模型难以准确反映水稻秸秆复杂结构、导致力学仿真精度不足的问题,本文提出基于工业CT扫描的真实结构有限元建模方法,用于精确分析适收期水稻秸秆的力学特性与失效机理。通过高分辨率CT获取茎节断层图像,三维重建并结合材料属性建立高保真有限元模型。经轴向拉伸、三点弯曲和剪切实验验证,模拟结果与实验高度吻合(拉伸实验R2≥0.985,弯曲实验R2≥0.988,剪切实验R2≥0.988)。应力云图揭示失效机制:拉伸时裂纹在茎节节间过渡区萌生并沿纤维方向扩展,呈脆性断裂;弯曲破坏由拉伸应力主导,裂纹同样沿纤维方向扩展;剪切失效为刃口前缘应力集中引发的脆性断裂。为研究结构非均匀性的影响,将秸秆按直径分为粗段(A1)、中段(A2)和细段(A3),发现中段(A2)抗弯强度最高,粗段(A1)抗剪强度最大,细段(A3)抗拉强度最高。分段研究揭示了力学特性的结构性根源,为农机部件针对性优化提供精细化的数据支撑。该方法显著提升了水稻秸秆力学分析的准确性与机理揭示能力,为收获机、打捆机等关键部件优化设计提供了可靠仿真平台与理论依据。

Abstract:

Aiming to address the low accuracy of traditional geometric models in simulating rice straw mechanics, a finite element modeling method was proposed based on industrial CT scanning of the actual structure. A high-fidelity model was reconstructed from CT images and validated through physical experiments including axial tension, three-point bending, and shear tests. The simulation results were in good agreement with the experimental results ( tensile test R2≥0.985, bending test R2≥0.988, shear test R2≥0.988). Stress nephograms revealed the failure mechanisms under different loading conditions: tensile failure initiated at the transition region between the node and internode, bending failure was dominated by tensile stress, and shear failure resulted from stress concentration at the cutting edge. Based on diameter variation, the straw was divided into three typical segments, namely the coarse segment (A1), the intermediate segment (A2), and the thin segment (A3). Significant differences in mechanical properties were observed among these segments: the intermediate segment exhibited the highest bending strength, the coarse segment demonstrated the greatest shear strength, while the thin segment showed the highest tensile strength. This method effectively enhanced the accuracy of mechanical analysis and provided a reliable simulation foundation for optimizing key agricultural machinery components such as harvesters and balers.