Shun Yi Jin

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

Abstract 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.

Experimental observations of AA6061-T6 round extrusions under a cutting deformation mode with a deflector

A cutting deformation mode of AA6061-T6 round extrusions initiated by a heat-treated 4140 steel alloy cutter incorporating a deflector was investigated experimentally considering the load/displacement and energy absorption characteristics. Two different geometries of the cone-shaped deflectors, namely, straight and curved profiles, were considered in this research. The tubular specimens utilised in this experimental investigation were round AA6061-T6 tubes of lengths 200 mm with a nominal wall thickness of 3.175 mm and an external diameter of 50.8 mm. In addition to these specimens, additional extrusions were tested such that a progressive folding and global bending deformation mode was observed. Specimens which experienced global bending were of identical cross-sectional geometry as the extrusions which experienced cutting; however, the lengths of these extrusions were 300 mm. Results from the experimental tests showed that the cutter penetrated through the extrusion and formed petalled sidewalls which contacted the deflector and initiated bending in the petalled sidewalls. An almost constant cutting force, of magnitude 45 kN, was observed for the cutting deformation mode without the deflector. The presence of the straight or curved deflectors generated fluctuations in the cutting force which were significantly less than the variations in load for the specimens which experienced progressive folding, resulting in an increase in the crush force efficiency. As a result of the bending imposed on the petalled sidewalls from the deflector, a reduction in the steady state cutting force, to approximately 37 kN, was observed.