Dynamics And Fatigue Analysis Of C₈₀ Heavy Haul Freight Car

The total annual transportation volume of the Daqin Railway has exceeded 450 million tons,successfully creating a world record for the total annual transportation volume of a single track,and China’s railway transportation industry has entered a new era.In order to meet the needs of high-quality economic development,China’s railway freight car heavy-duty fast and lightweight technology has also made great progress,which puts forward higher requirements for the dynamic performance of heavy haul freight cars and the anti-fatigue design of car bodies.In this paper,the C₈₀ heavy haul freight car body is taken as the research object,and the actual structure of the car body is discretized based on the finite element method.Because the local stress concentration of the welded structure will affect the fatigue analysis results,it is necessary to establish a finite element model of C₈₀ freight car with weld details.Based on the"Craig-Bampton"modal synthesis method,the flexible body of C₈₀ gondola car is made.According to the detailed parameters of the components of the K6 bogie,the multi-rigid body dynamics model of the bogie is established,and the connection relationship with the flexible body is established,and the rigid-flexible coupling dynamics model of the C₈₀ heavy haul freight car is established.In order to simulate the vibration of C₈₀ car body under the condition of line operation,the vehicle running stability under the straight line and the curve passing performance under different track radius are calculated by using the five-level track irregularity spectrum of the United States as the excitation.The results show that the stability and safety of the vehicle meet the design requirements.The fatigue strength of C₈₀ heavy haul freight car is evaluated according to the relevant load conditions and standards of quasi-static method.Firstly,based on the"TB/T 1335-1996"standard,the static conditions are applied to the car body,and the"Goodman"curve is drawn according to the fatigue parameters of the car body material to calculate the fatigue safety factor of the high stress level of the car body under quasi-static load.Then,according to the environmental load spectrum given in the AAR standard,the load spectrum is converted into a stress spectrum,and the fatigue life of the key welds of the car body is calculated based on the Miner fatigue damage accumulation criterion.Considering the impact of elastic vibration of C₈₀ gondola car body under track irregularity excitation on the fatigue life of welded structure,this paper combines rigid-flexible coupling dynamics simulation with related fatigue analysis method to calculate the fatigue life of key welds of car body.Firstly,the maximum principal stress time history of the weak part of the weld after dynamic simulation is extracted,and the cyclic load spectrum is compiled by rain flow counting method.The fatigue life of the weld is calculated by IIW standard and BS7608standard respectively.According to the vibration response of the car body structure after the dynamic simulation,the master S-N curve is used to evaluate the fatigue life of the weld based on the modal structural stress method.According to the fatigue analysis results under quasi-static load and dynamic simulation,the fatigue life of the weld between the large beam and the middle beam of the chassis of the weld 1 is relatively low.The evaluation results of modal structural stress method show that the equivalent fatigue life of the weld is 4.28 million kilometers,which does not meet the design requirements.Since the modal structural stress method takes into account the influence of local stress concentration and structural vibration on the fatigue life of the weld,the calculation results are closer to the real situation.Two improvement plans were proposed and verified based on the characteristics of the welding structure.The results show that the life of the improved scheme is 78%and 215%higher than that of the original scheme,and the fatigue life of the improved car body structure meets the design requirements.