Bitubular square tubes with different arrangements under quasi-static axial compression loading

This paper attempts to present new methods for improving the crashworthiness parameters of square thin-walled energy absorber components. Experimental and finite element analyses were performed on bitubular square thin-walled tubes with different arrangements under quasi-static axial compression loading. 15 tests were conducted on single and bitubular square aluminum tubes. To investigate the energy absorption capacity of bitubular tubes and assess the effect of different parameters on crashworthiness characteristics of these tubes, finite element code LS-DYNA was utilized. At first, single tubes were investigated, and then bitubular tubes with two different arrangements including Parallel and Diamond arrangements were studied. Results show that absorbed energy by bitubular tubes is more than the sum of the energy absorbed by inner and outer tubes loaded separately which is due to the interaction effects between inner and outer tubes. Diamond arrangement was used to highlight the role of interaction effect in energy absorbing as progressive buckling modes of the tubes change because of the interaction. Also, the effect of length difference in inner and outer tubes was inspected and the main advantage of bitubular tubes is introduced when the inner tube is shorter than the outer. In this case, the peak load remains the same as that of the outer tube while mean load increases considerably.