Characterization of energy absorption in tapered thin-walled S-rails

Safety is a key design priority in the automotive industry. In a car crash, the higher level of energy absorption in the frontal structures leads to less transferred energy to the passengers and hence a safer car. S-shaped front rails, also known as S-rails, are one of the main structural elements and energy absorbers in a car body. Energy absorption in the S-rails happens through local buckling. In order to improve the passenger safety in a frontal crash, S-rails design should be optimised to absorb higher level of energy while crushing. In this study, a series of thin-walled tapered S-rails with square cross-sections were subjected to quasi-static and dynamic loading. A one meter steel S-rail with a thickness of 2.0mm was subjected to 20 different tapering ratios (from %110 to %300) with %10 increments which resulted in generation of 20 models. All models were subjected to both quasi-static and dynamic loading conditions. Finite Element models were developed and analysed using Altair HyperWorks and LS-DYNA software. The effectiveness of tapering S-rails was assessed through investigating the Specific Energy Absorption (SEA) variations in different models. Based on the numerical analysis, an ascending trend in SEA figures was observed as the tapering ratio was increased. In both quasi-static and dynamic loading conditions, the trend slop was further increased for the models with tapering ratios of more than %250. The results showed an improvement in SEA up to %21.55 and %33.1 respectively in quasi-static and dynamic loading conditions.