Fatigue Life Analysis Of Random Vibration For High-Speed Vehicle Car-Body

By the growing traffic demand of high-speed, convenience, safe and comfort, high-speed railway came into being, and trains travelled faster and faster. But the increase in speed would aggravate the vibration of the train. A large number of experimental data and numerical simulations showed that the vibration of high-speed train had a strong randomness. The long-term vibration might cause fatigue damage of car-body structure, affecting the service life of the car-body. In severe cases, it might endanger people’s lives and property safety. Under complex loads, currently managing to use test methods to analysis fatigue life of high-speed vehicle car-body’s structure was not perfect. Therefore, the article was based on the random vibration theory, in the track irregularity case, using finite element simulation method to predict high-speed car-body’s fatigue life.Firstly, from the perspective of the time domain and the frequency domain, the article respectively discussed random vibration fatigue analysis process, and in detail described several frequency domain methods. Comparison found that for large and complex structure, because of its low efficiency, time-domain method had not been adopted. If the structure was large, complex and its stress obeyed the Gaussian distribution, using Steinberg’s three-interval method to predict the structural fatigue life was simple and easy to implement.Secondly, the article analyzed and compared the fatigue properties of nominal stress, hot spot stress, notch stress. Hot spot stress needed to experiment with a relatively small number; and with the finite element method, stress concentration caused by geometry can be more easily calculated. Therefore, many experts and scholars respected more and more attention in the use of the hot spot stress S-N curve.Thirdly, currently due to predicting high-speed vehicle car-body’s fatigue life didn’t consider the track irregularity random excitation, so the article based on the CIT400high-speed vehicle, established the finite element model for the random vibration fatigue analysis, which included the detailed car-body finite element model, the wheel and bogie equivalent simplified model. By modal analysis to verify the equivalent simplified model was reasonable.Finally, by analyzing different countries’ track spectrum, found that all countries were given space track spectrum, so it needed to use a certain formula to convert them to the time track spectrum. Thus they can be the rail irregularity excitation of high-speed vehicle. The article used the three interval method and Palmgren-Miner linear cumulative damage theory to predict the car-body structural fatigue life which was used German low interference track spectrum. The results showed that the service life of the car-body met the needs of the actual running mileage. The article also analyzed the influence of speed,the track irregularity grade and welding standards.