Temperature and Thermal Stress Behavior of Freight Wagon Wheel Tread Under Emergency Brake Conditions for Long Downhill Ramps

Abstract:

A two-dimensional tread braking thermo-mechanical coupled finite-element mathematical model is established that balances computational accuracy and efficiency， integrating the high accuracy of strong thermo-mechanical coupling with the high efficiency of weak coupling. The effects of track gradient， vehicle load and axle load， initial emergency-braking speed， emergency-braking deceleration， and ambient temperature on the maximum tread temperature and peak thermal stress of the wheel are investigated. The results show that for every 3 ‰ increase in track gradient， the maximum wheel-tread temperature increases linearly by approximately 4.15 °C， while the maximum thermal stress increases linearly by about 8.18 MPa. For each 1 t increase in axle load， the maximum temperature increases linearly by approximately 7.19 °C and the maximum thermal stress by about 14.29 MPa. For every 10 km·h?1 increase in initial braking speed， the maximum temperature increases approximately linearly by about 31.21 °C and the maximum thermal stress by about 59.77 MPa； meanwhile， the time required to reach the maximum temperature and stress increases nonlinearly with speed. When the deceleration increases by 0.2 m·s?2， the maximum temperature increases approximately linearly by about 16.12 °C and the maximum thermal stress by about 31.67 MPa， while the time to reach the maximum temperature decreases nonlinearly. As ambient temperature decreases， the maximum tread temperature shows a downward trend， whereas its influence on the maximum thermal stress is relatively small. These findings provide quantitative data support and technical reference for thermal safety evaluation and optimized design of train operations on long and steep gradients.