On the axial crushing and failure of aluminum alloy tubes : experiments and numerical simulations

The use of aluminum alloys for light-weighting purposes in energy absorbing components of automobiles is hindered by the relatively low ductility and more complicated constitutive behavior of these alloys. This study presents results from series of quasi-static and dynamic axial crushing experiments on extruded Al-6061-T6 circular tubes of varying D/t ratios. A custom drop-weight testing facility was used to perform the dynamic experiments. Crushing led to axisymmetric, mode-2, and mode-3 concertina folding. In the quasi-static experiments, the folding was monitored using time-lapse photography; dynamic crushing was monitored using high-speed photography. The crushing responses and energy absorption capacities are evaluated and failures were recorded. Failure was observed in most of the experiments with the severity depending on the D/t and mode of folding. The experiments are simulated with three-dimensional, nonlinear finite element analysis using the von Mises, the non-quadratic Hosford, and the calibrated anisotropic Yld04-3D models. The Yld04-3D model was found to most accurately reproduce the structural response under both quasi-static and dynamic loadings. This model was used to the monitor the strains induced in two example cases: axisymmetric folding under quasi-static loading, and mode-2 folding under dynamic loading. The analysis predicted maximum strains to develop at locations on the model tube where failure is observed on the specimen in the experiments. It is concluded that the Yld04-3D constitutive model is most suitable for the prediction of the structural response and failure in tube crushing of this aluminum alloy.