Key Performance Indicators(kPIs) Of Energy Absorption Of Materials And Structures

In order to protect people and major structures in cases of traffic accidents for land vehicles and emergent landing for aircrafts and spacecraft, various energy absorbing devices have been investigated and applied, among which tubular structures are widely adopted. Circular and square tubes perform particularly well under axial compression/impact because their excellent energy absorption capacity during large plastic deformation and stable deformation mechanisms. In the last 20 years, the investigations have been extended to polygonal tubes, conical tubes, foam-filled tubes, pressurized tubes, pre-patterned tubes and honeycomb cellular materials, and so forth. Therefore, there is an urgent need to propose a set of Key Performance Indicators(KPIs) to assess and compare the energy absorbing performance of tubular structures with various configurations, so as to guide the design of energy absorbers whilst to archive a certain degree of optimization.Based on the deformation efficiency and the general role of energy absorbing devices, this paper proposes a comprehensive set of Key Performance Indicators(KPIs) which has five factors: Effective Stoke Ratio(ESR), Non-dimensional Load-carrying Capacity(NLC), Specific Energy Absorption(SEA), Effectiveness of Energy Absorption(EEA), Undulation of Load-carrying Capacity(ULC). Next in order to verify the feasibility of the set of Key Performance Indicators(KPIs), the energy absorption capacity of circular and square tubes has been studied in the five KPIs, and the results are compared with the theoretical results. Then considering that many factors may affect the energy absorption behavior of tubular structures, the influence of material properties and various geometrical parameters on tubular energy absorption is studied and analyzed. And the influence of foam fillings is also studied by modifying and extending the five key performance indicators to foam-filled tubes. Finally, with the wide application of the KPIs, the energy absorption capacity of circular and square multi-cell tubes is compared, as well as the circularcelled honeycombs and hexagonal-celled honeycombs under out-of-plane impact.Our study has made an extensive review on the experimental, theoretical and numerical results on various tubes under axial compression/impact, and the paper presents a series of diagrams to compare the energy absorbing performance of various tubes in terms of the five KPIs as described above. The work is valuable to engineering designs/applications, as well as to the further studies of the topic.