Comparison of the load/displacement and energy absorption performance of round and square AA6061-T6 extrusions under a cutting deformation mode

Quasi-static compressive testing of extruded aluminum alloy AA6061-T6 round and square cross-sectional tubular specimens was completed to investigate the crush characteristics of these structural members under a cutting deformation mode by using a specially designed cutting tool. Results from the experimental tests showed that the cutting deformation mode of the round and square tubes exhibited high crush force efficiencies (CFE) of 0.95 and 0.81 respectively. In comparison, CFE of round specimens that experienced progressive folding and global bending deformation modes were observed to be 0.66 and 0.20 respectively and CFE of square specimens that underwent global bending were found to be 0.22. An almost constant cutting force was observed for the round tubes in the cutting deformation mode, while a slight increase in the cutting force was observed for the square tubes under the same deformation mode. The increase in cutting force for the square tubes was observed to occur primarily due to contact arising between the cutting tool and tube sidewalls and to a lesser extent due to bending of the petalled side walls. For the round tubes, contact between the cutting tool and sidewalls as well as bending of the petalled side walls was not as significant and resulted in a more consistent cutting force. For both the 200 mm and 300 mm length tubes the total energy absorption for the round and square tubes was observed to be 6.11 kJ and 4.31 kJ respectively. The energy absorption was observed to be independent of tube length.