Bionic Design And Research On Energy Absorption Capability Of Thin-walled Tube Inspired By Bamboo Structure

The thin-walled tube is not only the main component of the vehicles, spacecraft and weapons, but also an important energy absorbing component. With the improvement of lightweight design and security requirements, improving the energy absorption efficiency of the thin-walled tube faced with theories, methods and technical challenges, under the condition of guaranteeing the strength and stiffness of the thin wall tube. In this study, the structure of bamboo is applied to the structure design of the thin-walled tube through the structure bionic principle, which can improve the energy absorption characteristics.According to the structural characteristics of bamboo jiont which is gradient distribution along the growth direction, the artist designs energy-absorbing structure with bionic section and bamboo jiont. Axial impact simulation show that the specific energy absorption of the bionic energy absorbing structure 10 B with no jiont is 34.35kJ/kg, which is improved by 61.4% compared with circular tube’s; the specific energy absorption of the bionic energy absorbing structure 11 YP with single jiont is 32.5kJ/kg, which is improved by 52.7% compared with circular tube’s; the specific energy absorption of the bionic energy absorbing structure 12 YP with double jiont is 28.55kJ/kg, which is improved by 23.68% compared with circular tube’s. Lateral impact simulation show that the specific energy absorption of the bionic energy absorbing structure 10 B with no jiont is 3.37kJ/kg, which is 1.26 times more than circular tube’s; the specific energy absorption of the bionic energy absorbing structure 11 YP with single jiont is 3.72kJ/kg, which is 1.49 times more than circular tube’s; the specific energy absorption of the bionic energy absorbing structure 12 YP with double jiont is 6.82kJ/kg, which is 2.69 times more than circular tube’s. Through the analysis, it is concluded that bionic structure with jiont can not improve energy absorption of thin-walled metal structures in the axial impact due to the difference between the metal material and bamboo material, but the structure with joint can improve the stability under axial impact load, and can significantly improve the lateral load and energy absorption.According to the structure characteristic of the bamboo which gradully become thinner along the growth direction, the artist designs a variable diameter thin-walled tube structure. The results of finite element simulation analysis show that the specific energy absorption and average load of first-order thin-walled structure VD2-5 in the axial impact are the highest, which are 30.32kJ/kg and 42.32 kN, respectively; The specific absorption energy of the two-order thin-walled structure VD3-1 is 25.4kJ/kg, which is increased by 17.6% than the circular tube’s. Analysis shows that the thinner tube will be stuck in the thicker tube, friction、extrusion and other action occured between the thinner and thicker tube when the variable diameter structures is subjected to the axial impact, and this stucture can not only change the order of its deformation, but also can increase energy absorption.According to the microscopic structure of bamboo which vascular bundle exhibit a density gradient variation characteristics from outboard bamboo skin to inboard bamboo inner place, the artist designs the combination tube whose material is variable in the radial direction. Axial impact simulation show that the specific energy absorption of steel tube, aluminum tube and steel-aluminum combination tube are 10.5kJ/kg, 27.6kJ/kg and 12.38kJ/kg, the specific energy absorption of steel-aluminium combination tube is between steel tube’s and aluminum tube’s. Using foamed aluminum to fill the thin-walled structure with the section 2, the simulation results show that the average load of thin-walled structure with foam aluminum 20B-AF is 80 kN, which is improved by 25% compared with 20 B without foam aluminum. The energy absorption of 20B-AF is 6.25 kJ, which is improved by 26% compared with 20 B.According to the results of finite element simulation, the artist processes eight thin-walled tubes, measures the energy absorption characteristicstest under the axial impact by the drop weight test. Experimental result is consistent with simulation result. The test of bionic sample with jiont show that the initial peak load of 3D-1 series with section 1、3D-2 with section 2 and 3D-03 with circular section are 190kN、145.36 kN and 44.98 kN respectively. The maximum absorption energy of 3D-03 is 1.5kJ, which is decreased by 2.7kJ than 3D-21. The energy absorption characteristic of 3D-21 is highest, and the cost can be saved considering the deformation and energy absorption. The sample tests of variable diameter show that the variables of thickness have greatly impact on energy absorption characteristics, the variable of length have little impact on energy absorption characteristics. And the fracture occurs when the variable diameter structure were subjected to axial impact.