Experimental investigations on the crush behaviour of AA6061-T6 aluminum square tubes with different types of through-hole discontinuities

An experimental investigation was conducted to compare the crush characteristics and energy absorption capacity of AA6061-T6 aluminum alloy extrusions with centrally located through-hole discontinuities. Three different types of geometrical discontinuities, namely, circular, slotted and elliptical holes were fabricated into AA6061-T6 extrusions which had a length of 200 mm, nominal side width of 38.1 mm and wall thickness of 3.15 mm. Furthermore, three different major axis lengths (7.14, 10.72, and 14.29 mm) and three different aspect ratios (1.33, 2.0, and 3.0) of the slotted and elliptical discontinuities were considered. It was found that by introducing crush initiators into the structural members, a splitting and cutting deformation mode was generated rather than global bending deformation which was observed for specimens without any discontinuities. The peak crush load was reduced by incorporating the through-hole crush initiators within a range of 5.2–18.7%, and total energy absorption was increased within a range of 26.6–74.6%. The most significant improvement was noted in the crush force efficiency, which was increased within the range of 54.5–95.8%. For specimens with discontinuities which had a major axis length of 7.14 mm the peak crush load and total energy absorption was independent of initiator geometry and aspect ratio. However, for specimens which had discontinuities with a major axis length of 10.72 and 14.29 mm and an aspect ratio of 3, a geometrical influence on the peak crush load and total energy absorption was apparent.