大豆籽粒的化学-力学特性灰色关联度及本构模拟

为研究大豆籽粒在不同受载情况下的力学特性,探索其化学-力学特性之间的关系,该文选择11种大豆籽粒在含水率为8.65%下对其进行化学组分、针尖压入、剪切、压缩试验,并借助Abaqus软件建立本构模型,对压缩试验过程进行模拟仿真。力学试验和模拟结果表明:所测大豆籽粒硬度为18.39~52.58 N/mm,大豆籽粒破损强度为3.65~15.32 MPa,大豆籽粒极限剪切力为12.70~52.33 N,纵轴的抗剪能力明显高于横轴;不同压缩形式和剪切方向分别对大豆籽粒破损强度和极限剪切力影响极显著;试验与仿真的载荷-变形曲线拟合良好,说明所建立的大豆本构模型能够分析研究其抗挤压特性。灰色关联度分析结果表明:与化学组分含量最为密切的力学指标是硬度与接触刚度,其中硬度与粗蛋白质、粗脂肪、粗淀粉、粗纤维含量的关联度分别为0.309 4、0.327 8、0.171 9、0.191 8,接触刚度与其关联度分别为0.220 6、0.283 7、0.186 9、0.133 4,粗蛋白质和粗脂肪含量对硬度与接触刚度的影响最大,其次是粗纤维素,粗淀粉含量。研究结果可为品质预测和品种鉴别提供新的方法和依据。

Gray relation degree and constitutive modeling of chemo-mechanical properties for soybean seed

Abstract: The chemical composition of soybean seeds has an important effect on the mechanical properties, and there is an inevitable connection between them. In order to study the mechanical properties of soybean seed under different loading types, and to explore the relationship between chemical composition and mechanical properties of soybean seed, 11 kinds of soybeans were selected as research material with the moisture content of 8.65%, and the chemical components test, the needle inserting test, the shear test and the compression test were carried out. Depending on the outline structure of soybean seed, compression types included flat placing, side placing, stand placing, and shear types included horizontal and vertical. The experiment was carried out in Gansu Agricultural University from March to July in 2016. Gray relation degree method was used to study the relationship of the 2 types of indices, chemical indices were set as the reference sequence, mechanical parameters were set as the comparison sequence, and the correlation degree and correlation order were analyzed with DPS software. With the support of Abaqus software, soybean seed constitutive modeling was set up, which defined the structure and properties by using the finite element software, and 3 types of compression test processes were simulated. The validity of the constitutive model was verified by comparing the simulation curve and the testing curve. Through mechanical test and compression simulation of soybean seed, the results indicated that the hardness of soybean seed was between 18.39 and 52.58 N/mm, the crippling strength of soybean seed was between 3.65 and 15.32 MPa, the ultimate shear force of soybean seed was between 12.70 and 52.33 N, and the variety had a highly significant effect on its mechanical properties (P<0.01). The resistance shear capacity of the longitudinal axis was significantly higher than the horizontal axis, and the ability of resisting damage from higher to lower was flat placing, side placing, and stand placing. Different compression types and shear directions had highly significant influence on the crippling strength and ultimate shear force (P<0.01). Force-deformation curves from the test fitted the simulation quite well, and the maximum deviation of flat placing, side placing and stand placing were 12.24%, 6.96%, and 9.55% respectively, which meant that the soybean seed constitutive modeling could reflect the crushing features. Through the chemical composition determination test, the results showed that crude protein and crude fat were the main chemical composition of soybean seed, and the average values of their mass fractions were 40.84% and 20.23% respectively. The contents of chemical components in different varieties were significantly different (P<0.01). The gray relation analysis indicated that in mechanical indices, hardness and contact stiffness were most closely related to the chemical content, the related degree of hardness with crude protein content, crude fat content, crude starch content and crude fiber content was 0.3094, 0.3278, 0.1719 and 0.1918 respectively, and the related degree of contact stiffness with crude protein content, crude fat content, crude starch content and crude fiber content was 0.2206, 0.2837, 0.1869 and 0.1334 respectively. The crude protein content and crude fat content of soybean seed had a significant influence on hardness and contact stiffness, and the influence of crude starch content and crude fiber content was lighter. Therefore the result has a great application potential in soybean seed storage and processing industry, and especially can offer a new method and basic for quality prediction and variety identification.