Design And Dynamic Response Of Self-locked Energy Absorption Structure Under Impact Loadings

Metal thin-walled tubes are widely used in energy absorption devices due to the light weight and high energy absorption efficiency.The round tubes combination system is a typical configuration.However,the simple circular tubes stacking energy absorption system is prone to lateral splashing under impact loadings,resulting in the attenuation of energy absorption.The splash kinetic energy will also cause secondary damage.Therefore,the structural design that takes into account the self-locking characteristics and efficient energy absorption is an important research content for safety protection.A self-locking structure formed by stacking dumbbell-shaped thin-walled tubes achieves good energy absorption improvement through confinement between tubes.In this paper,the energy absorption characteristics of the selflocked structure under impact load were studied in depth from the aspects of self-locking effect,geometric parameter influence and performance enhancement.The main contents are as follows:(1)The finite element model of the self-locked structure was constructed,and the FE source codes LS-DYNA was used to carry out the numerical simulation of the in-plane impact on the self-locked structure and the ordinary cylindrical honeycomb.The key datas of the deformation mode,crushing force and energy absorption of the structure were obtained,and the energy absorption characteristics of the structure were analyzed.The geometric parameters of the dumbbell-shaped thin-walled tube,such as wall thickness,transverse width,and tube diameter,as well as the influence of the reinforcement in the tube on the crashworthiness were studied.The results showed that: increasing the wall thickness,reducing the tube diameter and reinforcing the pipe can improve the bearing capacity of the structure and strengthen the energy absorption of the system;the lateral width has a significant impact on the contact between the tubes of the self-locked structure,and the more contact points,the better the energy absorption performance.(2)In order to improve the crashworthiness of the self-locked structure,the topology optimization of the stiffeners of the structure was carried out to achieve energy absorption enhancement.Based on Opti Struct software,with the goal of minimizing the structural strain energy and the element density as the design variable,the topology optimization of the dumbbell-shaped thin-walled tube was carried out under static compression conditions.Referring to the optimization results of the optimal distribution of materials in the tube,a new type of reinforced section configuration was established.Simulation results showed that the specific energy absorption of the new reinforced self-locked structure is 508.3% higher than that of the original structure,the energy absorption performance is significantly improved.(3)According to the characteristics of the stacked arrangement of the self-locked structure,the influence of the wall thickness gradient distribution of the tube layer on the impact performance of the self-locked structure was studied.The results showed that: at different impact velocities,reducing the wall thickness of the impact end of the tube fittings and making the wall thickness of the tube layer a positive gradient distribution can effectively reduce the crushing force.At high-speed impacting,the negative gradient distribution of wall thickness can effectively improve the structure’s energy absorption efficiency in early stage of deformation.The wall thickness gradient arrangement had a great control effect on the energy absorption.