The energy absorption of rectangular and slotted windowed tubes under axial crushing

In this paper, rectangular and slotted windows were introduced to thin-walled square tubes to improve the crash worthiness of tubular structures. Four one-windowed tubes, twelve three-windowed tubes and two conventional tubes were studied by quasi-static axial crushing tests and numerical simulations. Optical measurement system MatchID was employed to achieve full-field strain measurement. The results showed that the collapse modes of conventional tubes belonged to symmetric mode, while the others were irregular mode. In addition, the introduction of windows could effectively reduce the initial peak load and increase the crush force efficiency (CFE) over conventional tube. However, the SEAs of windowed tubes did not necessarily improve even though large mass reduction for windowed tubes. The initial peak load is inclined to decrease with the increase in area ratio (eta, defined as the ratio between the windowed area and the surface area of conventional tube). Furthermore, it was found that cracks appeared in numerous specimens in the tests due to welding. And with the increase in length ratio (lambda, defined as the ratio between the length of all cracks in one tube and the tube height), CFE and SEA had a decreasing trend, while length ratio had little effect on initial peak load.