Offset impact in railway vehicles: A study on energy absorbers

In response to the growing regulatory emphasis on evaluating non-axial impact conditions in crash safety assessments, this study investigates the crashworthiness of thin-walled tubular energy absorbers under offset impact using Finite Element simulations, performed with LS-DYNA. Four typologies were analysed: Simple Tubes (ST), Tapered Tubes (TT), Multi-Cell Tubes (MCT) and Bi-Tubular Tubes (BTT). Larger cross-sectional dimensions (above 225 mm) significantly improved energy absorption and promoted progressive folding, while wall thickness had minimal effect on stability. While BTT and MCT achieved the highest absolute energy absorption, they also exhibited the greatest performance decline under offset conditions. Conversely, ST and TT showed the lowest change in performance. Cross-sectional shape critically influenced deformation: narrow corner angles (e.g., triangles, squares) enhanced folding and stability, while wider shapes (e.g., octagons) increased buckling risk. These findings inform optimal design strategies for energy absorbers under realistic off-axis impact conditions.