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, using Finite Element Methods, the crashworthiness impact of tapering S-shaped rails is studied through investigating the energy absorption and Specific Energy Absorption of 42 tapered square cross section steel S-rail models subjecting to quasi-static and dynamic loading. The results are verified using analytical analysis. To develop the models, two S-rails, one without (type A) and one with (type B) internal diagonal reinforcement are tapered with 20 different tapering ratios ranging from 110% to 300% with 10% increments. All models are subjected to quasi-static and dynamic loading conditions. The effectiveness of tapering S-rails is assessed through investigating the Specific Energy Absorption (SEA) variations. In quasi-static loading conditions, tapering type A models showed 144% increase in energy absorption and 22% improvement in specific energy absorption. In type B models under quasi-static loading, the energy absorption increased by 118% and a maximum of 6% improvement in specific energy absorption was achieved as a result of tapering the S-rails. Reinforcing type A0 model to B0 model also increased the energy absorption by 412% and specific energy absorption by 279%. In quasi-static loading, the maximum specific energy absorption was observed in model B14 with 275% improvement in SEA comparing to model A0. In dynamic loading condition, an increase of 167% was observed in type A models as well as 33% increase in specific energy absorption. Type B models subjected to dynamic loading showed 101% increase in energy absorption and a maximum of 25% improvement in specific energy absorption as a result of tapering S-rail. Reinforcing type A0 model to B0 model also increased the energy absorption by 307% and specific energy absorption by 201%. In this loading condition, the maximum SEA achieved by reinforcing and tapering model A0 to model B11 which increased the specific energy absorption by 301%.
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