Finite Element-Based Fatigue Analysis of Medium-Speed Train Car Structure

Medium-speed trains operating at 160 km/h experience substantial aerodynamic drag that contributes to the structural loading of the car body. Within the train set, the locomotive section receives the highest tensile forces, making its structural integrity crucial. This study presents a fatigue analysis of the locomotive car structure to estimate its service life under realistic operational loading conditions. The loading scenarios were derived from typical train operations, including acceleration (0.5 m/s2), service braking (1.25 m/s2), emergency braking (1.52 m/s2), cruising at 110 km/h, and a maximum speed of 160 km/h. A surface-based finite element model with longitudinal symmetry was developed to reduce computational effort, and fatigue assessment was performed using the Modified Goodman diagram based on the major principal stress responses. The results indicate that the structure generally satisfies the infinite-life criterion, except when the train is fully loaded and subjected to service or emergency braking, where the welded regions fall below the allowable fatigue threshold. To address this issue, reinforcement was added to the underframe, effectively reducing the principal stress levels and thereby increasing both the fatigue safety factor and the predicted fatigue life.