Crashworthiness Simulation Analysis Of High-Speed Train Bodies Based On Welding Residual Stress Model

With the outstanding achievements in the construction of rail transit,the safety of high-speed trains has attracted more and more attention.Although the operation of railway lies in a relatively independent and closed space and the probability of an accident is small,such an accident occurred will lead to the destruction of the train bodies,resulting in passenger casualties and economic losses.In this paper,the high-speed train body is taken as the research object to achieve the passive safety prediction of the car body structures.The influence of actual factors,such as the welding residual stress generated by the car body manufacturing and the strain rate effect of the car body materials,on the structural deformation and energy change of the high-speed train structure in the collision is also considered.This is of great significance to improve the efficiency of crashworthiness analysis and the accuracy of safety prediction.Relying on the scientific research project "Research Technology and Application of Passive Safety Prediction of High-speed Train Based on Controllable Stress Field",this paper mainly completed the following work:(1)Firstly,through theoretical analysis,the differences of different initial conditions in explicit calculation in the theory of finite element were obtained and the impact of different implicit-explicit data transfer methods on the collision were compared through simulation.According to the literature examples,the initial welding data of the local side wall structure could be obtained.Several different initial data transfer methods were used to introduce the welding simulation results into the collision simulation model.The effects of three different methods of introducing only initial deformation,only initial stress and both initial deformation and stress on the response of collision simulation were compared.Results showed that compared with the initial deformation,the initial stress has a greater influence on the deformation mode and energy absorption of the structure collision.Therefore,when considering the influence of welding factors on the crash resistance,the introduction of the residual stress can be mainly considered.(2)The number and structure types of welded joints at each position on the car bodies were investigated by relevant literature.Welding numerical simulation calculations for three typical welded joints--lap joint,butt joint and T-shaped weld joint were conducted.The residual stress distribution of different welded joints was compared and analyzed,and then a two-dimensional aluminum alloy MIG welding residual stress model is simplified and fitted to achieve the initial stress field loading of the target structure by calling the functions.In addition,aiming at the problem that the mesh size of the vehicle body collision model does not match to that of the welded joint,an engineering method suitable for the loading residual stress field model was proposed.(3)Through the split Hopkinson pressure bar(SHPB)dynamic test,the mechanical behavior of the aluminum alloy material of the car body at different strain rates were studied,and the test samples were prepared according to the standard.The two-wave method was used to obtain the variation law of aluminum alloy materials under different strain rates,and the stress-strain curves under different strain rates obtained by the experiment were fitted according to the Johnson-Cook model.The SHPB finite element simulation model was established,and the experimental data and simulation waveforms at three different strain rates were analyzed by combining finite element and experiment to verify that the fitted model can effectively characterize the dynamic mechanical behavior of aluminum alloy.(4)The evaluation parameters were established according to EN15227,and the simplified residual welding stress model based on typical welding joint simulation and the Johnson-Cook dynamic constitutive model based on test-simulation were imported into the established collision scene.By analyzing the longitudinal response,vertical response,the speed and impact force change with energy dissipation process of high-speed train during collision,it was found that the deformation energy absorption of vehicle body after considering strain rate effect of material is more reasonable and closer to the actual situation.The results showed that the welding residual stress reduced the crashworthiness performance of the vehicle body,and caused significant changes in the stress,vertical displacement and occupant acceleration of the vehicle bodies.There are 49 figures,7 tables and 60 references in total.