Fatigue damage assessment of bogie frame based on an improved nonlinear cumulative damage model

The structural damage of rail vehicle bogie frames is mostly caused by fatigue cumulative damage under the action of multi-level complex loads. Under complex loads, the sequence effect and coupling effect between loads have a significant impact on structural fatigue damage. Meanwhile, the performance degradation of components during service also affects the damage accumulation and the remaining life of the structure. Traditional linear cumulative damage models and the Manson-Halford model ignore the influences of load sequence effect, load interaction, and structural degradation on fatigue life, leading to inaccurate remaining life predictions. By introducing degradation parameters to modify the Manson-Halford model, an improved nonlinear cumulative damage model is proposed, and its accuracy is verified by combining standard specimen fatigue test data. Finally, the improved cumulative damage model was applied to engineering practice in engineering to predict and evaluate the fatigue life of bogie frames.