Impact responses of circular steel tubes at elevated temperatures: Experimental and numerical studies

The impact responses of circular steel tubes at elevated temperatures were experimentally and numerically explored in this paper. A drop weight impact loading system was employed to apply the impact forces to the specimens after they were heated to the target temperature by employing an assembled furnace. All specimens presented a failure mode of three plastic hinges. The impact resistance of specimens exhibited an initial decrease, later increase and eventual decrease as the temperature increased. This phenomenon was caused by the negative temperature sensitivity of steel strength (i.e., strength increases with temperature) induced by dynamic strain aging (DSA). Moreover, the impact force and displacement of specimens significantly increased with impact velocity. Corresponding finite element (FE) models were established and verified with experimental results. The model was employed to investigate the bending moment distribution and energy absorption of the steel tubes subjected to impact at elevated temperatures. The FE results showed that steel tubes first experienced a bending-dominated phase, followed by a tensile-dominated phase during impact. In addition, the majority of impact energy was absorbed by the steel tubes at the plastic hinge zones when the temperature was less than 400 ℃. However, the energy dissipation became more uniform across the specimen at higher temperatures, especially at 700 ℃. These findings firstly provided the comprehensive demonstration of the influence of the temperature on impact responses of steel tubes, particularly clarifying the anomalous behavior characteristics caused by DSA effect.