Energy Absorption Research Of High-speed Train Collision

Collision accidents of rail vehicles in service have not been completely avoided with the improvement of active safety warning technology,it is necessary to investigate passive safety design.Different from collision accidents of other transportation,there appears typical characteristics of multi-body interaction in collision of high-speed train.Each vehicle interface participates in collision energy absorption.Reasonable distribution of energy absorption at each interface of train is the key to reduce occupant damage caused by longitudinal collision load.Therefore,the research in this paper mainly improves the energy absorption of train from the aspects of the simplified model of longitudinal collision,the dynamic loading limitation of carbody structure and the design of new energy-absorbing structure at the end of train.The detailed research contents are as follows:(1)Establishment of Johnson-Cook constitutive model.The static tensile and dynamic compression experiments of aluminum alloy materials from high-speed carbody,6005A-T6 and 6082A-T6,were carried out using universal material testing machine and split Hopkinson pressure bar to study the law of the flow stress at different strain rates(0.0001s-1-3000s-1),and the strain rate sensitivity of the two aluminum alloy materials at medium and low strain rates is determined,and then the Johnson-Cook constitutive model is established.The results show that the two aluminum alloys have weak strain rate sensitivity,and the strain rate effect can be neglected in the numerical analysis of rail vehicle impact.(2)Investigation on the determination of the loading limitation for aluminum alloy carbody of high-speed train under impact.The dynamic response of a single carbody under impact load is analyzed by LS-DYNA,and the weak stiffness region of the carbody is identified.The variation law of deformation,impact force and key position stress for the car body are studied,and Dynamic load limitation at specified position of the car body is determined.The research shows that it is feasible way to analyze numerically the dynamic strength limit of carbody,the results can provide reference for the parameter design of energy absorption structure fixed at the end of the vehicle body.(3)Establishment of one-dimensional train collision analysis model based on nonlinear bar element.The three-dimensional collision model of aluminum alloy car body for high-speed train is established,and the simulation analysis of rigid wall impact carbody condition is carried out to obtain the collision response between the carbody and rigid wall.The parameters of the bar element are corrected and the equivalent parameters are obtained.The effectiveness of the equivalent parameters is validated by individual collision response from simplified model and 3D model.Finally,the simplified bar element is adopted to form the train collision model,and the collision analysis by one-dimensional simplified model and three-dimensional model of train organized by four vehicles,are respectively carried out,and the velocity and interface force of each vehicle are obtained.The analysis shows that the simplified collision model has better prediction accuracy for the main collision response,and can be used for the design and optimization of energy configuration parameters during train collision.(4)A gradient function-controlled train cross-section energy distribution model is proposed,which effectively improves the low energy absorption efficiency of existing train energy configurations.By introducing the gradient control function,the train collision energy distribution is parameterized,and the radial basis function neural network model is used to establish the mapping relationship between the gradient parameters and the vehicle acceleration and the peak force response index of the continuous interface during the train collision.The influence law of gradient change parameters on the response of trains is studied,It is found that the optimal gradient parameters can optimize the train response.Based on the one-dimensional collision model,the multi-objective optimization problem of minimizing the collision force at the end face of the vehicle is established.The optimal gradient parameters of the train energy allocation scheme are obtained by genetic algorithm.It is effective to verify that the collision energy configuration system of the train is combined with the one-dimensional simplified model and the optimization method.(5)Based on the gradient parameter design method,a wall thickness gradient honeycomb structure is proposed.Through the simulation analysis of the axial crushing energy absorption process of the wall thickness gradient honeycomb,the peak of the structure specific energy absorption and crushing load is obtained.The optimal Latin hypercube sampling method is used to sample the spatial parameters of the gradient parameters,and the approximate model between the specific energy absorption and crushing load peak and wall thickness gradient parameters is constructed.With the gradient parameter as the design variable,the crushing load peak is the smallest,and the specific energy absorption is the objective function.The multi-objective optimization model of the wall thickness gradient honeycomb structure is established,and the improved non-dominated sorting genetic algorithm is used to solve the wall thickness gradient.Optimal gradient parameters for the cell.Finally,the wall thickness gradient honeycomb structure is applied to the design of the end energy absorbing device of the high-speed train.Compared with the equal wall thickness honeycomb structure,the crashworthiness of the vehicle body is obviously improved.