Hollow Plant With Septate Internodes Stalk, Numerical Analysis Of Stability

If be the same weight, hollow plant stalks will be harder to be bent than solid ones. But such hollow stalks will be easily local buckled. The plants will lodge if their stalks buckled, and will influence output of plants such as wheat, paddy, and corn. So it is very necessary to research on the mechanical characteristics of hollow stalk plants.The thesis takes hollow stalk plants as research object. Anisotropic mechanical methods were used to build models. And use Ansys to study non-linear bending characteristics on those models. Take account of hollow stalk plants' section change under their curvature change, how the geometry and material parameters will influence the stalks' bending, transformation, and carrying capacity was discussed. Major work done by the thesis includes:1. Takes hollow stalk plants as transverse isotropic material. Use orthotropic material and shell elements to build finite-element models in Ansys, use the characteristics of transverse isotropic material to deduce parameters of orthotropic material;2. Takes non-linear buckling analysis. During calculation, use different geometry and material parameters to simulate different buckling status. Include the important Brazier buckling, which occurs during the ovalization. Analyzed how the geometry and material parameters will influence the stalks' bending, transformation, and carrying capacity: keeping other parameters unchanged, wall thickness has most significant influence, then ratios of the Young's modulus in the tangential and longitudinal directions, while Poisson's ratios and stalk length have no significant influence. After calculation, the author found that Brazier effect is the main cause of bending of hollow stalk plants. The more anisotropic the plant stalk is, the more obvious the Brazier effect is. If Brazier effect occurs on a stalk, it will bend after 25% to 30% of flexion. The author suggests take 25% of flexion as a warning line of calculation. If Poisson's ratio decreases, the ability of anti bend decreases.3. Occurrences of septate internodes can improve the ability of resist bending, while this improvement depends on the internodes' position and distance. If there are some septate internodes right up the basal stalk, especially if these internodes are near to each other, this plant will be much harder to be bended.4. The author drew a conclusion that: Brazier effect is the main cause of bending of hollow stalk plants. Its effect varies while wall thickness and ratios of the Young's modulus in the tangential and longitudinal directions changes. The author defines degree of bending of section in danger as an important index of stability of such plants.