Influence of a variable friction coefficient on the thermo-mechanical behavior of railway wheel treads under different operating conditions

Excessive thermal loads generated during freight wagon braking can lead to severe thermo-mechanical damage of railway wheel treads, including hot spotting, shelling, and thermal cracking. Accurate prediction of frictional heat generation at the wheel–brake shoe interface is therefore critical for assessing the thermo-mechanical response of railway wheels. However, most existing numerical models are based on the frictional power approach and assume a constant friction coefficient, thereby neglecting its dependence on temperature and sliding velocity, which may introduce significant deviations in the predicted results. In this study, a coupled thermo-mechanical numerical framework is developed to investigate the influence of friction coefficient modeling on the thermal and stress responses of wheel treads. Two friction coefficient representations are considered: a constant friction coefficient and a temperature- and time-dependent friction coefficient. The effects of these two models on the evolution of maximum temperature and thermal stress under different braking conditions are systematically analyzed. The results show that incorporating a temperature- and time-dependent friction coefficient has a pronounced influence on the predicted thermo-mechanical behavior. Under high-load conditions, a temperature-dependent friction coefficient reduces the growth rates of peak temperature and thermal stress by 48.8% and 30.6%, respectively. Under high-speed braking conditions, the predicted peak temperature and thermal stress decrease by about 16.4% and 15.4%, respectively. In addition, the temporal evolution of thermal stress exhibits a characteristic response, consisting of a rapid increase, a gradual decrease, and eventual stabilization. These findings highlight the importance of considering friction coefficient variability in thermo-mechanical analyses and provide improved insight into the prediction of thermal loads in railway wheel braking systems.