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基于微CT建模的小麦籽粒力学特性有限元分析

Finite element analysis of wheat grain mechanical properties based on micro-CT modeling

  • 摘要: 为探究不同粒型小麦在挤压破碎过程中的力学行为,探索粒型对小麦力学特性、应力、应变及总变形规律的影响,该研究以含水率为16%的小麦籽粒为研究对象,采用微CT(X-ray micro-computed tomography)扫描建模与有限元分析相结合的方法,精确构建小麦籽粒的三维模型,系统分析了不同粒型小麦在挤压破碎过程中的力学特性、应力、应变及总变形分布规律。结果表明,小麦粒型与力学响应行为密切相关,较大小麦籽粒具有更高的抗压强度和弹性模量,且应力集中主要发生在籽粒腹沟区域。整体挤压分析表明,不同粒型的小麦裂纹生成规律相似;在腹式和侧式压缩下,裂纹均沿腹沟处产生,并延腹沟向内部延伸,这一结果通过微CT扫描模型的精确建模与有限元模拟得到了验证,同时将小麦颗粒受挤压时的应力应变及总变形分布情况可视化,以表征小麦颗粒在挤压过程中的力学行为。通过微CT扫描小麦压缩后的裂纹与有限元模拟后腹沟处应力集中的现象进行对比,从试验与仿真双重角度验证了腹沟区域其特有的结构特征。本研究通过微CT扫描与有限元分析的结合,揭示了小麦腹沟作为力学薄弱区域的结构特性,构建了精准的挤压模型,为优化制粉工艺参数、实现小麦精准低损加工提供了理论模型与设计依据。

     

    Abstract: Wheat is one of the most vital staple crops in the world. Its milling process is one type of physical operation using extrusion-induced fragmentation. This study aims to explore the influence of the kernel morphological structure on its mechanical behavior under compressive loads using X-ray micro-computed tomography (micro-CT) modeling and finite element analysis (FEA). The research subjects were selected as wheat kernels with a moisture content of 16%. Accurate three-dimensional (3D) models were constructed for the simulation. The milling parameters were optimized for highly precise and low-loss wheat processing. A texture analyzer was employed to capture the stress-strain curves of the wheat kernels. Different morphological types were utilized under the ventral and lateral compression modes. These curves were used to determine the relationships among kernel morphology, elastic modulus, compressive strength, and ultimate load. The results show that the minimum elastic modulus and compressive strength were calculated as 35.15 and 5.57 MPa, respectively in the largest kernel type (A1). Large-grained wheat also exhibited a higher limit load during extrusion, indicating a stronger resistance to deformation. In contrast, the small-grained wheat shared the lower limit load more prone to rupture under relatively lower loads. Furthermore, the ultimate load reached 59.62 N under ventral compression, which was significantly higher than the 50.44 N observed under lateral compression. Therefore, the minimum extrusion load of 59.62 N was recommended for the full fragmentation of the wheat kernel in industrial milling. Three-dimensional geometric models of the wheat kernels were reconstructed using micro-CT scan data and reverse engineering techniques. Subsequently, the optimal models were imported into the FEA software. The distribution of the stress and strain fields was then simulated to clarify the total deformation behavior under compression. Simulation results indicated that the ventral groove region exhibited the most significant concentration of stress and strain, indicating the primary structural vulnerability during loading. In contrast, the equatorial plane was identified as the key governing region for the propagation of deformation throughout the kernel. Furthermore, the crack propagation paths in micro-CT images demonstrated that the high degree of spatial consistency with the high-stress regions was predicted by FEA simulation. In the ventral and lateral compression modes, the cracks were consistently extended inward along the longitudinal axis of the ventral groove. The initiation and propagation areas of these cracks closely matched the simulated regions of the maximum stress concentration. The high alignment between experimental observations and simulation validated the reliability and effectiveness of the model with micro-CT imaging. The mechanical behavior of the wheat kernels was also obtained to integrate the micro-CT imaging and FEA simulation. A robust model was also provided to accurately simulate the internal stress. The deformation mechanisms of wheat kernels under compression offered valuable theoretical insights for the milling industry. The grain morphology was highlighted to determine the structural role of the ventral groove and equatorial plane, particularly the mechanical response of the kernels. Such insights were crucial to refine the milling strategies, in order to minimize the structural damage for the high yield and nutritional integrity. Ultimately, the findings can greatly contribute to the theoretical models and engineering design for the optimal parameters of wheat milling. The key areas of the stress concentration were identified as the mechanical response of the kernels under various loading. The finding can also provide the scientific foundation to improve the milling efficiency, energy saving, and nutritional quality of wheat products.

     

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