Crashworthiness Design Of Multi-Tube Combined Structure Based On The Concept Of Configuration Misalignment Superposition

The current research of rail vehicles is mostly carried out from two aspects: the optimal design of single tube and the application of multitube combinations.The former has defects such as complex structure,complicated process flow,and energy absorption upgrade bottleneck.In comparison,the application of multi-tube combination is a more efficient and convenient way to improve energy absorption.However,due to the lack of a systematic combination design method,the overlapping load curves of each tube tend to result in significant amplification of the initial peak and subsequent load fluctuations of the combined structure,which prevents the smooth dissipation of collision kinetic energy.In order to overcome the above-mentioned shortcomings,the influence law of load curve formation timing is explored,the control method to achieve effective separation of load curves of each tube is proposed,the design method of configuration differentiation suitable for multi-tube combination structure is summarized,and the design framework of nested multi-tube combination structure with high energy absorption,low initial peak and small load fluctuation is constructed.Initially,the evolution law between the time series of macroscopic deformation and the time series of load curve formation is analyzed with a typical thin-walled energy-absorbing structure as the research object.A unitary theoretical model for the time series of peak load formation is established,which reveals that the position of plastic hinge formation is the key influencing factor on the time series of fold deformation.Further,three constitutive parameters that can be used to control the time series of load curve formation are determined,and the accuracy and reliability of the finite element models are verified based on experimental means.Secondly,the optimal combination of structural size and number of the three configuration parameters is determined,and a theoretical model of mechanical performance is constructed to serve the subsequent collaborative design of multi-tube structures.The influence of local/global height difference on the timing of load curve formation is analyzed,and the influence of the configuration moving distance on the timing of load curve formation is quantified,which leads to an accurate method of controlling the timing of load curve formation.Then,the application method of variable configuration distribution design in multi-tube combination conditions is proposed,and the influence of the tube number on the energy absorption characteristics of three variable configuration distribution multi-tube combination structures is quantified.On this basis,a universal multi-tube load curve misalignment superposition mechanism is established to guide the multi-tube collaborative design.Finally,based on the idea of nested combination,the energyabsorbing characteristics improvement and application research of the height difference-variable configuration distribution multi-tube structure is carried out.The nested combination mode with optimal energy absorption characteristics and suitable for multi-tube collaborative design is determined.Through comparative analysis with typical energy-absorbing structures and vehicle crash simulation analysis,the energy-absorbing advantages and practical application value of the configurationdifferentiated multi-tube structure are further verified.The results show that the initial peak value and load fluctuation of the nested multi-tube structure with configuration differentiation are 47.33% and 22.31% lower than those of the multi-cell thin-walled structure under similar macroscopic size and energy absorption.In addition,the configuration of the differentiated multi-tube structure can reduce the initial peak load and load fluctuation by 56.74% and 69.69%,respectively.In summary,the configuration differentiation design method based on the concept of multi-tube load-displacement curve misalignment superposition can effectively solve the technical bottleneck that are difficult to be compatible with excellent energy-absorbing characteristics such as high energy absorption,low initial peak value,and small load fluctuations,and can provide sufficient data and theoretical support for the application of multi-tube combined devices in railway vehicles.