Research on fatigue characteristics and service life assessment of the end-underframe of high-speed train’s carbody

The carbody is the core structure of a high-speed train for carrying passengers and installing equipment. The end-underframe area is a crucial part that directly bears various types of loads, and its structural strength directly affects the service life of the entire carbody. Given that conducting fatigue tests on the whole carbody is costly and time-consuming, this study explores the feasibility of using the end-underframe structure to evaluate the service life of the carbody’s end-underframe area. Firstly, a rigid-flexible coupling dynamics model of a certain type of high-speed train was established. According to the statistical data of the railway line, combined with the operation history of the vehicle and the variation law of wheel wear, working conditions such as straight-line operation, curve negotiation, traction, and braking were divided, and the characteristics of the end-underframe interface load of the carbody under different wheel wear and operation conditions were analyzed. Then, based on the cumulative damage method, the damage value of each weld node in the end-underframe area under different operation conditions was calculated. The positions with larger damage values were identified as areas of concern, and a test load spectrum for each operation condition was compiled according to the principle of equal damage in the dangerous area. Finally, combining the train operation record with the cutting principle, a comprehensive life cycle test load spectrum for the carbody’s end-underframe was compiled, and the life prediction of the carbody’s end-underframe was conducted. A service life test plan for the end-underframe of the high-speed train was then designed.