Crashworthiness Analysis Of Thin-walled Multi-cell Structures

Thin-walled metal energy-absorbing structures are widely used as automotive energy absorbers because of their good energy absorption effect. To design light and efficient thin-walled metal energy-absorbing structures with good crashworthiness is very significant for improving vehicle passive safety & saving energy. In this paper, research is carried out in order to improve the structural crashworthiness of thin-walled metal absorbing structures. In order to improve the crashworthiness of thin-walled metal energy-absorbing structures, four types of new energy-absorbing structures with good performance are proposed, then they are deeply studied about crashworthiness.Firstly, In order to derive theoretical expressions of the mean force of new energy-absorbing structures under axial load, and research their crashworthiness by Finite Element Simulation Method, This paper focuses on the Super Folding Element Theory and Simplified Super Folding Element Theory, introduce briefly the theory of explicit nonlinear finite element theory.Then, based on Simplified Super Folding Element Theory, theoretical expressions of the mean force of new energy-absorbing structures are derived respectively under axial load. In order to improve the crashworthiness of thin-walled metal energy-absorbing structures, a series of new energy-absorbing structures are proposed:double-hexagon multi-cell tube. Based on Simplified Super Folding Element Theory, four types of double-hexagon multi-cell sections are divided into three basic angle elements:"2-shape", "3-shape", "T-shape"angle elements. In addition, the energy dissipation of angle elements is estimated respectively. Based on this result, theoretical expressions of the mean force of double-hexagon multi-cell tubes are derived respectively under axial quasi-static load. Taking into account the structural inertia effect, theoretical expressions of the mean force of double-hexagon multi-cell tubes are derived respectively under axial dynamic load.Secondly, crashworthiness of thin-walled multi-cell tubes is studied based on Finite Element Simulation Method, the reliability of theoretical expressions of the mean force is verified by using simulation results. Perform Experimental Design for double-hexagon multi-cell tubes by Full Factorial Experimental Design Method,16 sets of experimental sample points are selected in this study. Furthermore, finite element models are established respectively,64 simulation models are calculated under axial dynamic load. To carry out comparative analysis between theoretical results with numerical results, the accuracy of theoretical expressions of the mean force of double-hexagon multi-cell tubes is verified.To carry out comparative analysis about simulation results, the results show that the "Type-2" multi-cell tube has the highest Specific Energy Absorption and Force Efficiency, thus it has the best crashworthiness.Finally, engineering application of "Type-2" double-hexagon multi-cell tube is studied. Because "Type-2" double-hexagon multi-cell tube has the best crashworthiness, so a new energy-absorbing box is proposed:"Type-2" energy-absorbing box. Original and"Type-2" energy-absorbing box are used separately in front bumper structure of a certain type of car, their finite element models are established. The models are executed simulation calculation about frontal low-speed collision(16km/h)and high-speed collision(50km/h).The simulation results are analyzed, the results show that crashworthiness of "Type-2" energy-absorbing box is better than original energy-absorbing box, meanwhile the quality of "Type-2" energy-absorbing box decrease 35.54 percent than original energy-absorbing box, so it is beneficial for the lightweight design of vehicle body.