Predicting the dynamic behavior of train collisions using similitude theory is a valuable design tool. However, several limitations and difficulties persist when designing a similar train model. This study proposes a mechanical equivalence similitude method when a train crashes into a rigid obstacle longitudinally, which can be used to establish similitude laws and predict the dynamic responses of a full-scale high-speed train middle vehicle. This method includes impact force equivalence (IFE) and finite-element stiffness equivalence (FESE). The aim is to overcome the insufficient accuracy of establishing a similar train model using traditional similitude methods. First, the similitude laws of the end energy absorber and the vehicle body were deduced. Subsequently, the 1/8th equivalent similar middle vehicle model of the high-speed train was established. The IFE method was employed to design a 1/8th equivalent similar model of the end energy absorber. Based on the FESE method, a 1/8th equivalent similar model of the middle vehicle body was built. Finally, the accuracy and effectiveness of a similar train model were validated through numerical simulations and tests. Comparing the results of the prototype, the errors of the dynamic responses were less than 4%, indicating that the mechanical response equivalence similitude method is effective for constructing a similar train model.
Hexagonal honeycomb is widely used in structural passive safety protection because of its low density, high specific strength and stable deformation process. The effects of cell wall thickness, initial impact velocity and impact direction on the deformation modes and crush characteristic of the hexagonal honeycomb are investigated with an impact finite element model (FEM), in which the cell wall thickness and out-of-plane thickness of the hexagonal honeycomb are variable. The results showed that, when the hexagonal honeycomb was impacted in the transverse plane and longitudinal plane, the impact end of the structure always shrank inward until the middle of the hexagonal honeycomb was compacted, and finally the whole structure was compressed. When it was impacted in the 60∘ oblique plane, there was no inward shrinkage, and the whole structure was compressed and deformed from the impact end toward the fixed end. Under the same initial impact velocity in different impact directions, the initial peak force (IPF) and specific energy absorption (SEA) of the hexagonal honeycomb increased with the cell wall thickness. When the cell wall thickness was constant, the IPF and SEA of the hexagonal honeycomb increased with the initial impact velocity. Then empirical formulas for IPF and SEA of the hexagonal honeycomb crushing were obtained and verified by simulation. It was found that the errors of proposed empirical formulas for IPF and SEA of the hexagonal honeycomb both were within 10%, which means the empirical formulas can be used to predict the crashworthiness of the hexagonal honeycomb.
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