Effect of cyclic low-temperature changes on crashworthiness of thin-walled structure made of aluminum alloy 6063-T6

This study investigates the influence of cyclic low-temperature exposure on the crashworthiness response of embossed thin-walled structures made of AA6063-T6 aluminum alloy. The experimental program included static tensile tests on standardized dog-bone specimens and dynamic axial crushing tests on square, thin-walled columns equipped with spherical, concave crush initiators. The specimens were subjected to cyclic thermal exposure in the temperature range of 0–30 °C, corresponding to long-term operating conditions of roadside energy absorbers. Optical microscopy observations and X-ray diffraction (XRD) analysis revealed local microstructural changes in the embossed regions, including partial alignment and redistribution of Mg 2 Si precipitates, as well as changes in diffraction peak intensities associated with residual stress relaxation and recovery. Static tensile tests demonstrated a reduction in the yield strength and ultimate tensile strength after cyclic thermal exposure, whereas the largest decrease was observed for specimens subjected to the longest exposure period (T3 and T4). Dynamic crushing tests revealed a gradual reduction in the peak crushing force (Pmax) of 10%, whereas the mean crushing force remained nearly constant throughout the investigated thermal exposure conditions. Consequently, the Crush Load Efficiency (CLE) and Total Efficiency (TE) increased by up to 10%, while the progressive crushing mechanism remained stable. The results indicate that long-term cyclic thermal exposure may affect the local material response and crashworthiness of embossed aluminum thin-walled structures, despite the relatively low temperature range used during the conditioning process.