CYCLIC BENDING RESPONSE AND FAILURE OF 6063-T5 ALUMINUM ALLOY OVAL SQUARE TUBES

This paper investigates the response and failure of 6063-T5 aluminum alloy oval square tubes with four different long/short axis ratios (1.5, 2.0, 2.5, and 3.0) under cyclic bending. The wall thickness is 0.7 mm for all oval square tubes, and cyclic bending loads are applied until fracture failure occurs. The experimental moment-curvature relationships exhibit stable loops for all long/short axis ratios. The experimental relationships between short axis variation and curvature (where short axis variation represents the change in the length of the short axis divided by the original length of the short axis) demonstrate symmetry, serrations, and a growth pattern as cycles progress. Moreover, a larger long/short axis ratio corresponds to a greater short axis variation. Regarding the curvature-number of cycles required to initiate fracture relationships, it can be observed that the four long/short axis ratios correspond to four straight lines when plotted on double logarithmic coordinates. Lastly, this study proposes theoretical equations to describe the aforementioned relationships. The theoretical analysis is compared with experimental data, revealing a close alignment between the two approaches. This indicates that the theory can reasonably describe the experimental results. Keywords - 6063-T5 Aluminum Alloy Oval Square Tubes, Long/Short Axis Ratios, Moment, Curvature, Short Axis Variation, Cyclic Bending, Failure.