Torque analysis on bionic model of bamboo weevil rostrum based on ANSYS

Abstract: Multi-layered composite cylindrical pipes have been widely used in pipeline transportation engineering field because of its high corrosion resistance and good wearing resistance. However, there is still a lack of theoretic analysis on torsion. The bamboo weevil (Cyrtotrachelus bugueti Guer) lives on bamboo shoots. Its rostrum bears big torque while drilling into bamboo. To reveal the torque-bearing mechanisms of rostrum, in this study, the detailed geometric structural parameters, composite elements and nano-mechanical properties of rostrum were respectively analyzed by electron scanning microscope, X-ray energy spectrometer and nanoindenter. The electronic microscope photographs showed that bamboo weevil rostrum was a hollow pipe mainly composed of 3 parts, i.e. outer layer, inner layers and reinforcing ribs. And the inner layers could be divided into axial layers and circumferential layers based on their morphology. The reinforcing ribs perforated several axial layers and circumferential layers along the radial direction, but its size and distribution were very randomly. From the element spectrum diagrams and nanomechanical tests, it was found that the outer layer of rostrum contained carbon (C), hydrogen (H), nitrogen (N) and oxygen (O), which are essential elements to composite chitin, and furthermore, it also contained inorganic salts like silicon (Si), magnesium (Mg) and potassium (K). And in this layer, the elasticity modulus, hardness and stiffness were 3.074 GPa, 182.254 MPa and 8.12 μN/nm, respectively. The main component of axial layers was saccharides or lipid that was dependent on the chemical union of C, H and O, and its elasticity modulus, hardness and stiffness were 3.152 GPa, 121.392 MPa and 10.283 μN/nm, respectively. The circumferential layers contained C, H, N, O and chlorine (Cl), and its elasticity modulus, hardness and stiffness were the highest, which were 8.645 GPa, 246.620 MPa and 19.695 μN/nm, respectively. From the measurement result, the main characteristics of bamboo weevil rostrum could be found. First, rostrum was a hollow multilayer pipe, which had nice strength and stiffness. Second, the outer layer was chitin, the axial layers consisted of sheet saccharides or lipid, and the circumferential layers contained protein and fibers. Specially, the circumferential layers had excellent mechanical capacity that made the rostrum more powerful. Third, the thickness of each axial layer changed in a certain sequence from outside to inside. In addition, the radial ribs connected several layers, which was conducive to better balance the stress and deformation on different bearing layers. Finally, the bionic multilayer pipes designed by learning the rostrum were modeled after appropriate simplification and majorization, and the torsional deformation was examined. The finite element analysis (FEA) method was applied to analyze the rationality of the cascading order of pipe wall in ANSYS software. In the FEA, SHELL181 and MASS21were employed, and all models were free meshed. The computer simulation results demonstrated that, if the outer layer had low elastic modulus material, and the inner layer had high elastic modulus material, the torsional deformation on the pipe would be the smallest. That is, enhancing the elastic modulus of inner layer material will be beneficial to strengthen the torsion capacity of the multilayer composite pipes. In addition, the simulation proved the reasonability of rostrum wall structure. The results on the torque-bearing mechanisms of bamboo weevil rostrum can provide theoretical references for the design of the multilayer composite pipes, especially for transporting pipe.