关键词: 应力谱, 非线性累积损伤, 扩展因子法, Levenberg-Marquardt优化算法, 等效损伤, 疲劳寿命

Abstract: In order to evaluate the fatigue reliability of a high-speed train bogie frame, based on the results of correlation analysis, some key measuring points on the frame were selected for line test. After collecting the measured dynamic stress of the line, the one-dimensional stress spectrum was compiled through the rain-flow counting process. The establishment process of Corten-Dolan and Manson-Halford nonlinear damage theoretical models is introduced respectively, and the models are modified by considering the interaction between loads and loading order. Based on the extended factor method, the measured extreme stress value is inferred, and the probability density distribution function of each measuring point is fitted based on the measured stress spectrum. The stress spectrum of all measuring points is extended to the whole life period. On this basis, the Corten-Dolan nonlinear model with high evaluation accuracy is screened out. Levenberg-Marquardt optimization regression algorithm was used to optimize the parameters. Based on the equivalent damage theory, the equivalent stress calculation formula under the nonlinear theory is derived, and the measured stress spectrum is substituted into the corresponding formula to analyze and calculate the equivalent stress at each measuring point. Combined with the S-N curves under three survival rates, the fatigue life of two kinds of frame materials is analyzed and compared. The results show that the fatigue life of the bogie frame can be prolonged by using SMA material at the weakest point of the frame.

Key words: stress spectrum, nonlinear cumulative damage, extended factor, Levenberg-Marquardt optimization algorithm, equivalent stress, fatigue life