Railway turnouts undergo repeated switching operations during service, and their connections are subjected to complex stress states resulting from the combined effects of operating temperature and switching loads. In particular, the large diurnal temperature variations in the cold regions of western China can induce considerable thermal stress in turnout rails, making fatigue safety an important indicator for evaluating the long-term service reliability of railway turnouts. To investigate the cyclic stress and fatigue risk at turnout connections, a coupled thermal–structural finite element model is established, and the rated switching force obtained from field measurements is applied to evaluate the fatigue behavior in both the closing and opening directions. The critical location is selected as the evaluation position, and the initial equivalent stress under the common reference state and the maximum equivalent stress at each operating temperature are extracted. Fatigue assessment is then performed using the U75V rail S–N relationship and Miner’s linear damage accumulation rule. The results show that the equivalent stress at the critical location is lowest under zero temperature difference, corresponding to an operating temperature of 20 °C. The equivalent stress results at the critical location are essentially consistent between the closing and opening directions, and the effect of operating temperature on the peak equivalent stress is substantially greater than that of the switching direction. At operating temperatures of 0–40 °C, the maximum equivalent stress remains below the yield strength of U75V rail steel, allowing elastic fatigue engineering estimation. At operating temperatures of 50 °C and above, the maximum equivalent stress exceeds the yield strength, while at 70 °C it further exceeds the ultimate tensile strength. These results provide a data basis for safety classification assessment of turnout connections under different temperature conditions, identification of critical temperature ranges, and long-term service condition monitoring.

Railway turnout, thermal-structural coupling, equivalent stress, fatigue life, temperature conditions