Research On Collision Characteristics Of The Metro Train Based On The Similarity Theory

The collision of trains is a transient process of nonlinear large deformation.Collision tests are one of the best methods to check the passive safety performance of vehicles.However,due to the limitations of the test sites,testing method and funds,It is difficult to carry out multiple repetitive real vehicle collision tests.Therefore,based on the pressure and limitations of the train test in engineering practice,this paper proposes a small-scale equivalent train model,which can effectively analyze the energy absorption characteristics of the main energy-absorbing region of the train during the collision,and provide the technical support for the full-size train.The main research content is as follows:Firstly,according to the deformation mode of the train during the collision,the energy-absorbing interval was divided,and the dimensional information was used to describe the parameter information in the collision process.The similarity theory and E.Buckingham theorem were used to derive the similarity rule,basic physical quantity and derived physical quantity of the metro vehicles.Choosing different scale factors to scale the model of the vehicle equivalently,and provide theoretical support for the subsequent vehicle collision performance analysis.Secondly,four scale of full-size,1/2,1/4,and 1/5 were established with the collision scenario of collisions of the thin-walled energy structures and rigid wall.In the simulation scenario,the intrinsic causes of the deviation of the energy absorption characteristics of the material are explained by comparing the simulation characteristics of thin-walled energy structures of different scales.The flow stress of the material will change with the strain rate,there is an inverse relationship between the dimensional expression value and the scale factor.Therefore,the smaller the model scale,the worse the accuracy of the predicted full-size real energy absorption characteristics.This proves that the material parameters of the structural model with the same material and different scales are not completely consistent.In this regard,using the Cowper-Symonds and Johnson-Cook formulas to establish two constitutive models to modify the strain rate characteristics of the material,under the premise of ensuring the same material,the prediction error range of the small-scale model is improved,Within that,the accuracy of full-scale energy-absorbing characteristics prediction based on the small-scale model is greatly improved.Afterwards,this correction method was used to establish collision scenarios for single-vehicle with rigid obstacles and single-vehicles,combined with collision characteristics of fractional energy absorption intervals of coupler device,anti-climbing devices,and the body structure.The full-size vehicle collision characteristics and structural deformation patterns will be improved based on the prediction of small-scale models,with maximum error control within 10% and can effectively explain the collision characteristics of full-size metro vehicles.Finally,summarizing the properties of different size models,different material constitutive relations and the comparison results of the different collision scenarios,this paper proposes a designing method to react characteristics of full-size model structure,based on the energy absorption characteristics and deformation pattern of the small size model structures,the design method can guide collision resistance design of the train vehicles.The research can be applied to the design of the main energy-absorbing regions of trains,saving a large amount of research costs and time costs.In addition,this research exist certain theoretical and engineering values.