Study On The Wagon-cargo Coupling Relationship For Railway Freight Under Conventional Track Conditions

Promoting the running velocity and loading capacity of wagons is the main goal for the development of Chinese railway freight.Although the allowed load and design speed of wagons have been increased in recent years,China's current“Railway Freight Loading and Securement Rules”has adopted relatively conservative empirical data and calculation methods in the setting of some regulations and standards.Such universal rules may restrict the transportation capacity of wagons in some cases so as to dissatisfy the requirement of current railway freight transportation.Therefore,it is necessary to study the wagon-cargo coupling relationship and demonstrate the impact of the loading and restraint of the cargo on the vehicle's running performance,so as to design the scheme of loading and restraint for each cargo.The coupling effect between the wagon and the cargo has a significant impact on the car body vibration and the wheel-rail contact force,which is directly related to the safety of freight transportation.The connotations of the wagon-cargo coupling relationship under the conditions of fixed restraint and flexible restraint are different from each other.This article takes the open-top wagon of C_70H as an example.The method of multibody dynamics simulations,accompanied with quasi-static analysis and dynamic analysis methods,are used to study the wagon-cargo coupling relationship under different restraint styles.The research contents are as follows:The relevant standards of various countries are compared comprehensively to use the derailment coefficient and wheel unloading ratio as the safety indicators in this article,whose limit values are 1.0 and 0.9 respectively.Based on the structural characteristics of C_70H,the methods of quasi-static analysis and dynamic analysis are adopted to reveal the wagon-cargo coupling relationship under fixed restraint.Then VI-Rail is used to establish the dynamics simulation model of wagon-cargo coupling system and verify the reliability of the model.According to the relevant standards of various countries and the characteristic parameters of the given cargo,the loading and running conditions of the MBS model are determined.The process of MBS model passing through the section under different conditions is simulated and the safety indicators are monitored.Based on the collected data,the safe distribution of the wagon gravity center under each running condition can be obtained.Then the"absolutely safe area"for the given cargo with the track spectrum of AAR5 is figured out and the algorithm is designed to generate the non-inferior solution space.According to the data collected during the curve negotiation,the influence of the location of wagon gravity center on the maximum derailment coefficient and wheel unloading ratio is analyzed under the condition of fixed restraint.The restraint strength of the cargo under flexible restraint conditions is designed based on the domestic and foreign calculation methods respectively and then the restraint material is selected in accordance with the existing standards.Based on the dynamics equation of the cargo,VI-Rail is used to build the cargo-wagon contact model,the restraint assembly model and the derived dynamics simulation model of wagon-cargo coupling system under the condition of flexible restraint.Subsequently,the dynamics indicators to be collected are determined as well as the vehicle running conditions and the restraint conditions.The running process of the MBS model with flexible restraint under different simulation conditions is simulated.The lateral vibration equation of the cargo is derived according to the force condition and lateral movement of the cargo in the coordinate system of car body during the curve negotiation.The dynamics indicators of the wagon are collected to analyze the respective wagon-cargo coupling relationship of different cargo locations and then the general conclusions are obtained.Based on the simulation results,the restraint strength for the given cargo is designed and compared with the reinforcement strength,which is obtained by conventional calculation methods,to verify the superiority of the method proposed in this paper.