Mechanical properties test and finite element analysis for litchi

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.