Research On Influence Factors And Optimization For Structure Crashworthiness Of Railway Vehicles

The frequent occurrence of railway vehicle collision accidents both in domestic and foreign countries have caused serious casualties and property loss, which brings heavy and painful lessons to people. How to reduce the accident rate of train collision, improve the operation safety of train and finally realize the personnel and property protection has become a key technology in the design and development of modern rail train. In this paper, the railway vehicle passive safety protection problems which draw more and more attentions recently were studied on the basis of the rapid development of China's rail transit as well as the increasing concerns on the security of vehicle transport from the whole society. The main research contents are as follows:Firstly, the energy-absorbing influence factors (such as structural cross-section shape, structure dimensions, material property parameters, structural pre-deformation, loading mode, initial collision kinetic energy and structural mesh size in numerical simulation) of typical thin-walled structure used for railway vehicle energy-absorbing structure were studied, and the influence laws of different factors on the structural energy-absorbing characteristics were researched in order to provide basis for the choice of appropriate influence factors and the improvement of vehicle crashworthiness. Then the more general rule was obtained through the summary and conclusion of the research results above, and the influence-factors&laws database system for energy-absorbing structure was developed. The system covers literature database, structure shape database, geometric parameter database, material parameter database, loading condition database, testing and calculation condition database, etc. And as a reference, the crashworthiness design of energy-absorbing structure can be carried out conveniently and quickly, which accelerated its application in the field of vehicle safety design in collision.In order to obtain the ideal crashworthy energy-absorbing structure, special energy-absorbing structure and load-bearing energy-absorbing structure of railway vehicle were optimized respectively based on Kriging surrogate optimization model. In the optimization process of specific energy absorption (SEA) and ratio of SEA to initial peak force (REAF) of special energy-absorbing structure, the Kriging surrogate models of SEA and REAF with regard to the design parameters were respectively constructed. The Kriging model has higher fitting accuracy compared with the traditional response surface model. Finally, the structure optimal values were obtained respectively through visual analysis and overall optimization of genetic algorithm (GA). In the optimization process of load-bearing energy-absorbing structure of railway vehicle, the Kriging surrogate models of SEA and REAF with regard to the design parameters were also constructed, and the SEA and REAF optimal results of the structure were obtained by genetic algorithm(GA). Results show that the models can obtain ideal target response values and it indicates that the optimized vehicle body has better crashworthiness through the collision analysis of the vehicle bodies before and after optimization,.In this paper, research of occupant secondary impact was carried out under different conditions based on the analysis of multi-car coupling collision:multi-car coupling collision model was firstly built up, and motion curves of speed and acceleration of every car and curves of occupant second impact velocity (SIV) were obtained through the analysis of multi-car coupling collision. Then the car body-passenger compartment-dummy coupling model was set up in Madymo software, the research of occupant secondary impact was carried out under the conditions when occupant face to desk, occupant face to chair and occupant face to occupant respectively according to the traditional passenger compartment arrangement in China. The results provide the basis for passenger compartment arrangement and compartment structure optimization.Influence factors of occupant injury severity during secondary impact were researched:through comparative analysis of two type accelerations, it showed that the occupant injury parameters calculated by the AV/ST9001upper limit acceleration were lager than that by the Volpe testing acceleration; the effects of acceleration pulse peak value and pulse duration on occupant injury were researched; Besides, the effects of compartment space dimension and structure contact stiffness on occupant injury and the sensitivity of each occupant injury parameters on the spatial structure parameters were respectively studied; finally, the response surfaces between occupant injury parameters and influence parameters were set up based on Kriging model, and the optimal configuration of the compartment space dimension and inner parts contact stiffness were obtained through the overall optimization analysis, so the purpose of occupant protection could be realized by improving the passenger compartment structure. The results can be helpful to guide the structure design of railway vehicle compartment.In short, the contents of this paper are specific and enriched, research programs and technical approaches focus on innovation combined with previous work basis, and the research results lay a solid foundation for railway vehicle passive safety research, being of theoretical significance and practical value.