The Influence Of The Initial States Of The Train On The Collision Responses

In order to further improve the crashworthiness of rolling stock structure,eight typical initial states are selected based on multi-body dynamics simulation and related standards to form several collision analysis scenarios.For the commuter train,the influence of different initial states on the collision responses is studied.Based on analysing the collision responses,the idea and scheme of improving collision stability are proposed from the aspects of reducing the steady-state force of the coupler-buffer and balancing the working position,and making some suggestions for evaluating the risk of collision.These working have great practical and theoretical value.Firstly,the multi-body dynamics simulation model of the commuter train is established,and four typical geometric poses are extracted as the single-vehicle-level initial states,Including pitch,bounce,yaw and swing.At the same time,combined with relevant standards,the four train-level initial states are supplemented,thereby forming the complete collision analysis scenarios.In order to simulate the dynamic mechanical response of the coupler-buffer more accurately,the finite element model of the drawbar compression simulation is established.Based on the model,the response process and dynamic mechanical characteristics of the drawbar from compression to instability are calculated and analyzed,and the critical unstable load is about 2220kN.On this basis,a finite element model of train collision is established,including rigid-flexible coupled vehicle body,wheel-rail elastic contact and equivalent spring element.Then,the dynamic equation of the vehicle collision is established.The positive feedback mechanism of the pitch and yaw movement in train collision is analyzed and summarized.A normalized processing method is proposed to analyze the average level of a type of collision responses.On this basis,the train collision models under different initial states are calculated.Combined with the simulation results,the influence law of each initial state on collision responses is studied,and the mechanism of typical collision responses is analyzed.Analysis found:(1)The positive feedback mechanism of the collision responses is dominated by the coupler-buffer and is an important factor causing the unstable responses.(2)The train-level initial states have different effects on the collision responses,but different types of collision responses have their own dominant factors,among which the effect of external input is universal.(3)The single-vehicle-level vertical initial states only affect the adjacent positions,but the lateral initial states affect the entire train,and the response of the train is increased by about 500%.The degree of influence on the response from serious to slight is initial yaw,initial swing,initial bounce and initial pitch.(4)In the collision,the second wheelset of the second bogie of the first vehicle generally has the greatest risk of derailment.The risk of derailment mainly comes from the wheelset being lifted by the vehicle body that was overly moving in the vertical.In addition to this,there is also the wheelset that climbs up the track due to excessive lateral movement of the vehicle body.In the scenario of(z=-40),the wheelset was lifted by the vehicle body by 37.912mm,and the track could not restrain it.In the scenario of(?'=+0.003),the height of the wheelset climbing the track was 22.285mm,which is about to derailed.Finally,it is proposed to improve the collision stability by increasing the anti-climbing and anti-biasing energy-absorbing device and reducing the steady-state force of the coupler-buffer.The simulation results show that the vertical height difference and lateral displacement of the interface S_A2 are reduced by 41.006%and 78.524%,respectively.This scheme effectively suppresses the climbing trend and lateral response of the train.In order to reduce the risk of collision,it is proposed to evaluate the train derailment in combination with the vehicle body poses,and it is suggested to limit the difference between vehicles,including vertical height difference and lateral displacement,and the asymmetry of collision interfaces.