Research On Multi-scale Model And Mechanical Properties Of Branching System Of The Family Palmae

During millions of years’ evolution, plants have developed their unique structure whichcan maximize their ability to adapt external environment. Thanks to years of wind torture,inshore Palmae naturally evolved into a powerful wind-resisted structure. Considering thesimilarity between the working condition of wind turbines and living condition of the palmtrees, and Roystonea regia as a typical plant of Palmae, The study aiming at the tissuestructure of Roystonea regia will help us unveiling the secrets of its wind-resist ability andprovide advices for the bionic design of wind turbines.The first step of the study was to achieve the material properties of the petiole. Thepetiole was assumed to be transversely isotropic material with five independent elasticconstants, which can be obtained by carrying out tensile experiment in three differentdirections with different tensile angles(the angle between tensile direction and fiberorientation) of0°,45°,90°. Secondly, finite element model of single petiole was createdand used in mode analysis and gravity-only strain analysis.SEM images of Roystonea regia samples give a detailed view of micro-structures fromdifferent functional organs. Tissues with mechanical function have a micro-structure which ismuch denser than that from ones with duty of transporting nutrients. From this discrepancy,we can conclude that there is a close “relationship” between the function andmicro-arrangement of plant tissue. In order to go further with the “relationship”, voronoifunction was employed in the transformation of the original image to available vector imagewhich can be used in finite element analysis software. In order to evaluate the quality of thetransformation, area ratio methods and area contour match criteria were created andprogrammed in MATLAB. The return data give us a perfect match between voronoitessellation and original image. Thus, the reconstructed voronoi tessellation is reliable forfurther modeling. Finite element analysis starts with a marco-scale model and each modelcontains a smaller sub-model inside. Each sub-model is subject to the boundary conditionsobtained from analysis of the coordinate up-scale model. By proper selection of sub-models,we can reach the scale of single vascular bundle. The result shows that the unique structure ofvascular bundle can lower the stress in petiole. Also the discrepancy of the analytic resultsbetween macro-model and micro-model indicates that the analytic results of macro-modelcannot fit the description of micro-model.