鲜枣整果力学特性研究及其有限元分析

为预测鲜枣在收获、贮运过程中的机械损伤，对甘肃靖远产小口大枣进行整果压缩特性研究及仿真分析。通过压缩实验，获得了不同加载速率条件下（10～30 mm/min）整果在横向和纵向上的弹性模量、破裂负载和破裂相对变形量：横向分别为：8.23～9.70 MPa、227.52～305.97 N、16.07%～17.46%；纵向分别为：10.05～11.44 MPa、288.50～383.17 N、16.33%～20.12%。通过观察鲜枣破裂特征，建立鲜枣压缩力学有限元模型，比较鲜枣在横向和纵向受压的模拟值和实验值，最大差异为11.4%。结果表明：鲜枣的抗挤压能力具有各向异性（相同压力下，鲜枣横向放置时的变形量大于纵向放置；相同压缩位移下，纵向承载压力大于横向）。在验证了仿真数值可行的基础上，利用有限元法可分析鲜枣内部应力应变的分布情况。研究结果可为鲜枣的作业装备设计以及减少其机械损伤提供理论依据。

Finite Element Analysis of Mechanical Properties of Whole Fresh Jujubes

The compression characteristics of whole jujube fruits of the Xiaokou variety from Jingyuan county, Gansu were explored and simulation analysis was also carried out in order to predict the mechanical damage of fresh jujube during harvest, storage and transportation. The elastic modulus, fracture force and relative deformation of whole jujube fruits under different loading rates through compression test were obtained as 8.23–9.70 MPa, 227.52–305.97 N, and 16.07%–17.46% in the transverse direction, respectively, and 10.05–11.44 MPa, 288.50–383.17 N, and 16.33%–20.12% in the longitudinal direction, respectively. By observing their fracture characteristics, a finite element model of compression mechanics for fresh jujube was established, and the biggest difference between the simulation and experimental values was 11.4%. The results showed that anti-compression capacity of fresh jujube was anisotropic, that is, the transverse deformation of fresh jujube was greater than their longitudinal deformation under the same pressure, while the transverse bearing pressure was greater than the longitudinal bearing pressure under the same compression displacement. The distribution of internal stress and strain for fresh jujube was analyzed using the finite element model after the simulation numerical solution was verified feasible. The results of this study can provide a theoretical basis for the design of operating equipment for and the reduction of mechanical damage in fresh jujube.