Energy Absorption Due to Quasi-Static, Low-Speed and Impact Oblique Crushing of Thin-Walled Tube Structure

From the viewpoint of improving both the crash safety and the fuel efficiency, various shaped thin-walled structures have been utilized as energy absorbers of automobiles such as front side members and crash boxes. In this study, quasi-static (≅0.03mm/s), low-speed (6.67mm/s) and impact (3~4m/s) crushing tests of some thin-walled regular polygonal tubes were performed by the testing devices of Amsler, Instron and the dropping-weight types respectively for the crush angle φ = 0, 10, 20, and 30° to investigate the effects of strain rate, crush angle and number of corners on the crushing behavior. The material is annealed S25C that shows high strain rate dependence. The transition from the axial collapse mode to the bending one occurred at certain crush angle between 10° and 20° for all the polygonal tubes and the testing-speed conditions treated in this paper. Once the transition occurs, the mean buckling load abruptly decreases and is not so sensitive to the crush angle under the bending collapse mode. The mean buckling load under the axial collapse mode greatly increases with the strain rate, while that under the bending one hardly grows.