Research on the Evolution Behaviors of Rail Surface Temperature during Train Acceleration/Deceleration Processes

This study investigated the transient thermal response of rail surfaces during train acceleration and deceleration processes through an integrated approach combining experimental simulation and computational modeling. The results showed that, during both acceleration and deceleration, the peak rail-surface temperature generally increased rapidly and then decreases. For a fixed circumferential acceleration, higher tractive resistance led to a higher peak temperature during acceleration. During braking, both the initial braking speed and the contact stress influenced the transient thermal response. Increasing the initial speed from 23.6 km/h to 70.8 km/h increased the predicted peak temperature from 730 °C to 895 °C, while different contact-stress levels altered the limiting deceleration before wheel lock-up and changed the temperature evolution. Under these transient conditions, temperature did not exhibit a simple one-to-one relationship with slip ratio or relative sliding speed alone. Within the present framework, the composite quantity P = slip ratio · relative sliding speed showed a strong empirical correlation with temperature evolution (|Pearson r| = 0.97–1.00) and could be used as a kinematic surrogate for thermal-risk tracking. The results further indicated that the isotherm distribution in the displacement-speed/circumferential-speed plane is insensitive to tractive resistance during acceleration, but shifts with the initial braking speed during deceleration, implying a higher thermal risk at higher braking entry speeds.