Theoretical prediction of dynamic axial crushing on a square tube with eight holes used as a crush initiator

Thin-walled square steel tubes are part of automobile structures, used as impact energy absorbers on crush boxes. Under axial crushing, such tubes sometimes produces unpredictable folding forms. There are three modes of dynamic axial crushing folding forms: the symmetric collapse mode; the asymmetric mixed collapse mode A; and the asymmetric mixed collapse mode B. The objective of this paper is to develop a theoretical prediction for the three modes on a thin-walled square steel tube with eight holes used as crush initiator. The basic folding mechanism is used to predict the dynamic axial crushing analysis on the tube. These theoretical analyses can also can be implemented in different crush initiator positions. Two types of cross section (c/h) were used in this study: specimen A (c/h = 60.42) and specimen B (c/h = 45.69). Thirty-six experimental drop test studies were conducted on the thin wall square tube. In addition, the results of a previous drop test were compared to the results of the theoretical prediction. The results show that the theoretical analysis has good agreement with the experimental drop test study. This study proposes nine formulas to predict average force, peak force and energy absorption of the dynamic axial crushing on the thin-walled square steel tube with eight holes of crush initiator. The limitation of these formulas, however, is that they are unable to show the relationship between force and time in a graph.