Simulation Study On Amplitude Safety Limits Of Track Complex Irregularity Based On The Most Unfavorable Loading Conditions Of NX₇₀ Flat Car

Safety is the eternal theme of railway transportation.Railway lines will have various forms of track irregularities in daily operations.When there is irregularities in different directions at the same position in the track,it constitutes a complex track irregularity that is more detrimental to the safety of vehicle operation than a single form of irregularity.In China,the current rail irregularity amplitude management standards are based on the actual vehicle test data set in a single form of track irregularity,and the test loading conditions and operating conditions are relatively simple.In order to ensure the safe operation of China's railways,it is necessary to carry out simulation experiments under unfavorable conditions to study the safety limits of track complex irregularity.This paper uses computer simulation experiments to analyze the effect of four forms of track irregularity on the operational safety of railway wagons,and considers factors such as cargo loading conditions and running conditions.By simulation experiment under unfavorable conditions,it is found that the current management standards can not meet the requirements for the safe operation of railway wagons.Based on the simulation experiments under the most unfavorable conditions,the amplitude safety limit of track irregularity is proposed,which provides a theoretical basis for the development of the orbital composite irregularity amplitude management standards.This paper has mainly done the following aspects of the work:(1)The types of track irregularity,waveform fitting function,and track irregularity power density spectrum of each country are introduced.The evaluation indicators of railway safety at home and abroad are analyzed.The first limit of the derailment coefficient and wheel load reduction rate specified in China's "Railway Vehicle Dynamic Performance Evaluation and Test Appraisal Code(GB5599-1985)”is taken as the evaluation standard for the operation safety of railway wagons.(2)According to the relevant principles of vehicle dynamics,a multi-body dynamics software SIMPACK was used to establish the simulation model of the NX70 flat car and the track irregularity incentive was established.Based on real vehicle test data,the reliability of the model was verified.(3)Analyze the results of simulation experiments,study four kinds of track complex irregularities and four kinds of single-track irregularities on vehicle operation safety evaluation index Influencing the law and summing up the sensitivity of derailment coefficient and wheel unloading rate to different types of track irregularities.(4)Design unfavorable cargo loading conditions and operating conditions.Through simulation experiments under unfavorable loading conditions,it is verified that China's current rail irregularity management standards can not meet the requirements for railway wagons safety.(5)Simulation experiments were conducted under the most unfavorable loading conditions and multiple rail irregularity amplitude conditions,and the proposed values for emergency management standards for track irregularities were proposed to provide theoretical basis for the formulation of relevant standards.