Energy-absorption behavior of metallic hollow sphere structures under impact loading

An integrated experimental and computation study is presented of the energy-absorption behavior of metallic hollow sphere structures (MHSS) as an innovative anti-collision material to protect bridge piers from vehicle impact loading. Quasi-static compression and dynamic split Hopkinson pressure bar impact testing were first conducted to compare different deformation and energy-absorption characteristics of MHSS subjected to different loading modes, followed by more realistic laboratory downscaled model impact testing and finite element modeling (FEM) of collisions between real-scale bridge piers and vehicle to further examine the energy-absorption capability of MHSS under dynamic loading. Results show that the MHSS exhibits an increased structural stiffness (e.g., by ~20 times), yield strength (by 4–5 times), and toughness (by 200%) with increasing loading rate (i.e., from static to impact loading). When used as a protective layer on bridge piers, the downscaled model tests and FEM simulations validated the MHSS can provide remarkable anti-collision function to concrete structures: MHSS can substantially reduce the horizontal accelerations (by 63–68%), displacements (by 56.6%), and surface strains of bridge piers, and there reductions further increases with impact velocity. The high energy-absorption capability of MHSS may originates from the exceptionally high, multiscale porosity as well as the excellent mechanical properties of the MHSS material. The findings suggest that MHSS can be an effective energy-absorptive material for anti-collision protection of bridge structures.