Crashworthiness enhancement of mild steel and aluminium crash boxes: Influence of Notch geometry through experimental and numerical evaluation

Crash boxes are essential for dissipating impact energy during frontal collisions through controlled progressive deformation. This study examines the crashworthiness of mild steel and aluminium 6063 square tubes (80 mm × 80 mm × 150 mm, 6 mm thickness) integrating five different notch geometries: square, rectangular, circular, elliptical, and corner notches. Numerical simulations using LS-DYNA were validated against full-scale compression experiments performed on a Universal Testing Machine. The results showed that notched specimens exhibit an increase in specific energy absorption (SEA) of 10%–25% for mild steel and 12%–28% for aluminium compared to plane tubes. The highest SEA was observed in rectangular-notched aluminium tubes (34.03 kJ/kg), followed by square-notched mild steel tubes (12.00 kJ/kg). Deformation modes obtained from experiments closely matched simulation predictions, confirming the reliability of the numerical model. The findings demonstrate that properly engineered notch geometries significantly enhance crash performance while reducing structural mass, making the proposed designs suitable for lightweight automotive applications. The study highlights the effectiveness of notch-induced deformation control as a practical approach for improving crashworthiness in lightweight automotive structures.