Crushing Performance of AA5754 and AA6082 Shells Fabricated by Warm Redrawing Process

Thin-walled end-capped shells of cylindrical cross-sections fabricated using aluminum alloys can be used as impact energy absorbers in automobiles. Deep drawing is a well-established method adopted to manufacture such end-capped shells. However, manufacturing aluminum shells with a high aspect ratio is technically challenging due to poor formability. In this work, the two-stage warm redrawing method was used to fabricate end-capped shells from automotive-grade AA5754 and AA6082 sheets. An improved part depth from each stage was ensured by maintaining nonisothermal conditions with heated die and binder at 200 & DEG;C and cold punch near to 30 & DEG;C. The thermomechanical FE model developed incorporating Barlat-89 and Cowper-Symonds parameters reasonably predicted the nonisothermal redrawing behavior. The FE-predicted thickness and strain distribution patterns were validated with experimental data. The shells thus fabricated were used to perform quasi-static crushing experiments. Both shells collapsed in an axisymmetric concertina mode with three outward folds. The load progression increased gradually at the beginning, followed by a cyclical pattern. The FE crushing simulations incorporated material flow behavior at room temperature according to Barlat-89 and Hollomon power law. Both thickness-mapped and constant thickness simulations predicted asymmetric crushing behavior, but the former predicted only two outward folds. The crushing simulations reasonably predicted the crushing load progression and collapse behavior only when all the forming histories were considered. The AA5754 shells were found to be a better choice due to superior post-warm redrawn strength properties. These shells showed 33.32% higher total energy and 17% higher specific energy absorption capacity compared to AA6082 shells.

Automated summary

In this study, thin-walled end-capped shells of cylindrical cross-sections made from automotive-grade AA5754 and AA6082 aluminum alloys were fabricated using a two-stage warm redrawing method. The AA5754 shells exhibited higher total energy and specific energy absorption capacity compared to the AA6082 shells.