摘要
为减小荔枝在收获、储运过程中的机械损伤,对荔枝的宏观和微观力学特性进行了研究。试验测定得到荔枝各部分的弹性模量;通过压缩试验,测得荔枝整果垂直受压的力学参数大于水平,垂直与水平受压的破裂力、弹性模量和破裂相对变形分别为101.69N和81.25N、0.37MPa和0.27MPa、30.33%和28.86%,并观察得到荔枝受压的裂壳特征。运用有限元法建立荔枝压缩力学模型,比较荔枝垂直和水平受压的试验值和仿真值,二者比较一致,其相关系数均达到0.999以上;研究荔枝在压载作用下的应力分布规律,分析其垂直与水平受压的抗挤压能力和裂壳特征,验证仿真数值解的可行性。试验结果表明:荔枝的抗挤压能力具有各向异性,相同压力下,垂直方向所能承受的压力和变形均大于水平方向;受压时在果壳拉应力作用下发生破裂,裂纹沿外力方向延伸,且出现的截面与压缩方向一致;采用所建立的荔枝有限元模型可以分析研究荔枝的微观力学性质。研究结果可为荔枝作业装备的设计以及预测和减少其机械损伤提供依据和帮助。
In order to reduce the mechanical damage of litchi in harvesting, storage and transportation, the macro and micro mechanical properties of litchi were studied. Through the compression experiment, elastic modulus of litchi hull, flesh, and core parts were determined. The measured data indicated that the mechanical parameters in the vertical direction were greater than that in the horizontal direction. Additionally, the rupture force in the in the vertical and horizontal direction were 101.691N and 81.253N respectively, while the elastic modulus were 0.37 MPa and 0.27 MPa, and the relative deformation were 30.33 % and 28.86 %. Meanwhile, the cracked hull characteristics also could be observed. A mechanical model of litchi was established by using of finite element method. The simulation values were consistent with the experimental values comparatively. And the correlation coefficient between them was over 0.999. In this paper, the model was used to study the distribution of stress under compressive load, and to analysis its anti-extrusion capacity and cracked hull characteristics, and to verify the feasibility of numerical simulation. The analysis results showed that the anti-extrusion capacity of litchi fruit was anisotropic. The vertical direction of litchi could bear greater pressure and deformation than the horizontal direction under the same pressure. When compressing, the shell would rupture under tensile stress. And the crack would extend along the direction of external force, whose section accorded with the compression direction. By the use of finite element model established, the micro-mechanical properties of litchi can be studied and analyzed. The results can provide basis and help for the design of operation equipments and reduction of mechanical damage of litchi.
出处
《农业工程学报》
EI
CAS
CSCD
北大核心
2011年第12期358-363,F0003,共7页
Transactions of the Chinese Society of Agricultural Engineering
基金
广东省自然科学基金资助项目(S2011010001933,9251064201000009)
国家星火计划(2010GA780049)
国家自然科学基金资助项目(31171457,30900870,31071583)
关键词
力学特性
有限元方法
弹性模量
荔枝
裂壳
mechanical properties
finite element method
elastic moduli
litchi
cracked hull
