The Effects of Hydroforming on the Mechanical Properties and Crush Behaviors of Aluminum Tubes

The effect of hydroforming on the mechanical properties and dynamic crush behaviors of tapered aluminum 6063-T4 tubes with octagonal cross section are investigated by experiments. First, the thickness profile of the hydroformed tube is measured by non-destructive examination technique using ultrasonic thickness gauge. The effect of hydroforming on the mechanical properties of the tube is investigated by quasi-static tensile tests of specimens prepared from different regions of the tube based on the thickness profile. The effect of hydroforming on the dynamic crush behaviors of the tube is investigated by axial crush tests under dynamic loads. Specimens and tubes are tested in two different heat treatment conditions: hydroformed-T4 (as-received) and T6. The results of the quasi-static tensile tests for the specimens in hydroformed-T4 condition show different amounts of work hardening depending on the regions, which the specimens are prepared from. As expected, the specimens from the region which experienced the largest amount of plastic deformation during hydroforming process show the largest amount of work hardening. The results of the quasi-static tensile tests for the specimens in T6 condition show that the precipitation hardening imposed on the specimens removes the work hardening induced by hydroforming and uniformly harden the specimens. The results of the dynamic crush tests show that the crush behaviors of the tubes in hydroformed-T4 condition are somewhat different from those of the tubes in T6 condition.