Sammendrag
In the present study the focus was to investigate the transition from progressive to global buckling (mixed mode) of square aluminium extrusions in alloy AA6060-T6 with at thickness of 2.5 mm and an outer width of 80 mm. Profiles with free lengths of 1300, 1600 and 1900 mm were tested in a pendulum accelerator. The profiles were clamped at a rigid wall and impacted by a trolley with a mass of 1400 kg at an initial velocity of 13 m/s. Fifteen samples were tested for each length. For all the profiles the buckling initiated at the clamped end and propagated towards the impacted end. One, five and seven profiles experienced a mixed mode for a free length of 1300, 1600 and 1900 mm, respectively. The rest of the profiles experienced a progressive buckling mode. Hence, the length interval for mode change seemed to be quite large. The video recordings during testing showed that how the first lobes developed was important with respect to the buckling mode.
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