Axial Deformation Behaviour of Mild Steel and 7075-T651 Aluminium Tubes Subjected to Drop Weight Impact

The present study has described the axial deformation behaviour of mild steel and 7075 -T651 aluminium against 350 kg drop weight falling from different heights (0.67-4.78 m). Three different cross-sections of the circular (55, 70- and 85-mm diameter) and the square tubes (43.41, 55.19- and 66.97-mm edge length) have been considered to ascertain their effect on the axial compression, deformation mode and energy absorption. In addition, the experiments have been performed on a circular (82 mm diameter) mild steel tubes subjected to 350 kg drop weight impact falling from different heights (0.25-1.76 m).

Numerical simulations have been carried out using ABAQUS/Explicit finite element code. The Johnson-Cook material model has been used to simulate the material behaviour of 7075 -T651 aluminium and mild steel tubes. Besides, numerical simulations have also been carried out for reproducing the experimental findings.

The predicted results of axial compression are found to have a deviation from the actual results in the range of 4-10%, showing the accuracy of the numerical approach. For both the metallic tubes, the axial compression of the circular and square tubes has been found to be decreased with an increase in the cross-sectional size of the tube, while the energy absorption has been found to be increased with an increase in the cross-sectional size of the tubes. For a given drop weight impact, the axial compression in square tubes has been found to be higher than the circular tubes of equivalent cross-sections. For both the metallic tubes, the energy absorption in the circular tube has been found to be higher than the square tubes of equivalent cross-sections. In addition, the axial compression in 7075-T651 aluminium tubes has been found to be higher than the mild steel tubes while the energy absorption in mild steel tubes have been found to be higher than the 7075-T651 aluminium tubes.

Based on the findings, the mild steel tube has been found to be a better energy absorber than the 7075-T651 aluminium tubes and the circular tube describes higher crashworthiness than the square tube. Besides, the higher cross-sectional area tubes illustrate better energy absorption characteristics.