Structural Vibration And Fatigue Analysis Of Rail Freight Car Body

Heavy haul transportation is an important direction of railway transportation development in China,which has a good development prospect.The ore vehicle weight is large,the load of the vehicle body is complex on the line,and the structure of the vehicle body is related to the stability and safety of cargo transportation.Therefore,the vibration and fatigue analysis of the ore car body structure provides theoretical basis and technical support for the design and improvement of the ore car structure.This article takes the 40 t axle load ore car body structure as the research object.The vehicle has a heavy weight and is mainly manufactured by welding steel plates.Considering the effect of weld details on stress concentration in mesh discretization,the finite element model of car body with weld details is established.First,calculate and evaluate the strength of the car body structure based on the design load of the car body structure of the AAR standard.Then,according to AAR fatigue load spectrum,the corresponding stress spectrum is calculated.Combined with the S-N curve of the corresponding welded joint,the fatigue damage of the welded seam of car body structure is calculated based on Miner linear damage accumulation rule.In order to investigate the vibration fatigue of the car body structure under the line load condition,this paper adopts the method of rigid-flexible coupling simulation to study.Firstly,Craig-Bampton fixed interface modal synthesis method was used to establish the flexible body of the car body structure.Other test bench tooling structure adopts rigid body simulation.Considering the elastic support and displacement driving device of the vehicle body,the rigidflexible coupling bench model of the ore vehicle body was established by using MSC.Adams software to simulate the vibration fatigue test.In order to verify the validity of the established rigid-flexible coupling simulation model.In order to verify the validity of the established rigidflexible coupling simulation model,the vibration acceleration of the key parts of the ore car body structure was compared with the measured data.The amplitude and frequency distribution of the vibration are basically consistent with the test results.Based on the calculation results of the BS7608 standard and the maximum principal stress in the rigid-flexible coupling model,the fatigue life of the key welds of the car body is evaluated.The evaluation results based on BS7608 standard and AAR standard cannot explain the fatigue failure phenomenon of weld seam during fatigue test.In order to reproduce the fatigue failure process,this paper combines the modal structure stress method with the rigid-flexible coupling dynamics simulation and proposes a new technology for the simulated vibration fatigue test of the rail freight car body.This technology solves the difficulty that the S-N curve data of welded joints can not meet the engineering application requirements in the traditional evaluation method,and at the same time,it can consider the influence of the vibration of vehicle structure on the fatigue life.Based on the rigid-flexible coupling dynamics simulation model,the modal vibration response results of the car body structure are obtained.Calculate the modal structure stress corresponding to each mode by using the modal structure stress method.Superposition to obtain the equivalent structural stress time history at the weld.Using the main S-N curve to evaluate the fatigue life of the key welds of the car body structure.Judging from the evaluation results,the method accurately identified the fatigue weak location in the car body welds,and the calculated fatigue failure time was also consistent with the test results.According to the change trend of the equivalent structural stress at the weld toe,the causes of fatigue failure are analyzed,and an improvement plan is proposed.The calculation verifies that the improved scheme meets the design requirements.This technology provides technical support for the design of the welded structure of rail freight cars in my country,and can also be applied to other industries.