Aluminium Extrusion Alloy Selection for Crashworthiness Energy Absorption and Failure

The targeted use of aluminium extrusions in automotive crashworthiness applications is a way for a significant weight reduction. Indeed, if the energy absorption is proportional to the mechanical characteristics, it takes important benefits of the thickness increase and of the use of closed sections, advantageously multicellular, allowed by the use of aluminium profiles. But in the case where the material and the geometry of the extruded product are not adapted, some undesirable failures may appear during the crash. Most of the time, these failures remain localised, and have no consequence on the energy absorption levels. Nevertheless, it appears important to predict their apparitions, and to adapt the alloys temper to reduce or eliminate it.

An experimental and numerical program was carried out to relate the behaviour of extrusions submitted to different crash conditions. The results were used to fit a damage mechanics based numerical model. It appears that the model, used with adapted parameters, offers a more accurate failure prediction than the conventional equivalent plastic strain limits.