Analysis of Mechanical Properties of Whole Apple Using Finite Element Method Based on Three-Dimensional Real Geometry

This study was intended to build 3D FEM geometry models of actual 'Fuji' apples by digitizing their surfaces, and to determine elastic modulus by FEM simulation based on the F-D curves of radial compression test from a point oil apple equator. Also, the general protocol of ASAE S368.4 for predicting the apparent modulus of elasticity and the maximum contact stress for convex-shape food materials was evaluated for its appropriateness. The model apple for FEM analysis was composed of approximately 35,000 geometry elements that closely resemble the surface of an actual apple. Through FEM simulation, the average elastic modulus of 7.732 MPa was obtained at the loading condition of 0.5 BP, which was 8.3% smaller than the average apparent modulus of elasticity predicted by the ASAE standard. The maximum Von Mises stress at the points of initial contact with the compression target plates evaluated by FEM simulation was about 37% smaller than the maximum contact stress determined by the ASAE standard, and a poor correlation was found between the results of the two methods. These results could be explained by that a whole apple, in general, has an anisotropic structure with many complex and small curvatures, has flesh texture bonded biologically, and is covered with more elastic membrane shell which contributes to prevent dehydration during compression.