Guangjun Gao

Crashworthiness analysis and structural optimisation of multi-cell square tubes under axial and oblique loads

ABSTRACT Square tubes have been widely used as energy absorption components. To investigate the influences of multi-cell configuration and loading arrangement on the crashworthiness of square tubes, eight kinds of multi-cell square tubes were numerically analysed under axial and oblique loads. Validation was performed against experimental data. According to the complex proportional assessment method, the T5-1 tube is found to have the best crashworthiness performance. Next, a parameter study was performed to analyse the effect of geometric parameters of the T5-1 tube on the crashworthiness. It was found that the s/b ratio and thickness have a significant influence on the energy absorption. The critical loading angle lies in the range of 10°–11°. Finally, a structural improvement design, with the straight tube changed to the taper tube, was implemented and the taper T5-1 tube was proposed. The results show that the taper T5-1 tube has better crashworthiness performance, compared with the original T5-1 tube.

Anti-snow performance of snow shields designed for brake calipers of a high-speed train

When high-speed trains run on a snowy railway line in cold weather, a large amount of snow and ice will accumulate on the brake calipers, which can lead to huge safety problems. In this paper, to solve this issue, a numerical method based on the detached eddy simulation was used to explore the flow features of a high-speed train running in cold weather. The accuracy of mesh resolution and methodology of Computational Fluid Dynamics (CFD) was validated against the wind tunnel tests. A discrete phase model was used to investigate the process of snow accumulation on the brake calipers by analysing the movement characteristics of snow particles. Based on this analysis, three kinds of anti-snow packing shields for the brake calipers were designed, and the shielding effects were compared via numerical simulations. The results show that a large amount of snow particles below the bogie directly impact the brake calipers causing massive snow packing on the bottom surfaces; some snow particles reflected from the rear equipment cabin cover return to the bogie region and accumulates on the upper surfaces. With the application of anti-snow packing shields with trapezoidal-, triangular- and cambered-shaped openings, the rates of snow accumulation on the brake calipers were reduced by 18.53, 26.68 and 38.81%, respectively. The cambered type provides the best anti-snow packing performance for the brake calipers.

Scale similitude rules with acceleration consistency for trains collision

This paper presents the scaled similitude rule for train collision, which follows the principle of acceleration consistency. If the similarity ratios of mass and initial impact speed of cars, crushing force, and initial length of the energy absorbing structures of trains with different proportions meet the requirements of the scaled similitude rule, the impact accelerations of each are considered to be consistent. The accuracy of the scaled similitude rule was analyzed by MATLAB simulation, which is based on the multibody dynamics theory. Before the analysis, the validation of the MATLAB model was verified based on the experimental model. Then the train-to-train collisions for two eight-car train sets with different similarity ratios were tested. Finally, the scaled similitude rule presented in this paper was found to be effective when the impact characteristics of the two models were compared.

Numerical study on the anti-snow performance of deflectors in the bogie region of a high-speed train using the discrete phase model

In this paper, the three-dimensional unsteady Reynolds-averaged Navier-Stokes equations with an RNG double-equation turbulence model and a discrete phase model were used for the investigation of snow accumulation on the bogie of a high-speed train. Two kinds of deflector plates, one installed at the front end and the other at the rear end of the bogie, were proposed to reduce snow accumulation. The accuracy of the CFD methodology was validated against wind tunnel tests. The results showed that high-speed air will impact the plates where snow particles get accumulated. The snow covering on the bogie rarely drifts back into the bogie region with air. The amount of accumulating snow in the optimum models is reduced by 50.58% on average as compared to those in the original models. At the rear end of the bogie, the inclined deflector plate reduced snow accumulation by up to 10.91% compared to the vertical deflector plate.

Effect of Cutting Slope Angle on Aerodynamic Performance of High-speed Trains

Research on aerodynamic performance of high-speed trains in cutting with different slope angles would complement the operation safety management under strong winds. This study was conducted to investigate the flow structure around train using computational fluid dynamics (CFD). The accuracy of the numerical method was validated, combined with wind tunnel test. This work shows that the surroundings of cutting along the railway line have great effect on the crosswind stability of train. With the increase of slope angle , the coefficients of aerodynamic forces tend to reduce. Comparing the angle 0° with 90°, the Cs, Cl and Cm of head car fall by 96.7%, 108%, and 96.8% to the maximum respectively, while those of middle car by 108%, 98.8%, and 105%. For the shield of applicable cutting, the whole body is in a minor positive pressure environment. Thus, an appropriate slope angle for the cutting can largely improve its windbreak performance.