The estimation approach of rail thermal stress based on vehicle-track dynamic responses

On account of the difficulty in measuring the true rail thermal stress, a new method is proposed to rapidly evaluate rail thermal stress based on the dynamic responses of vehicle-track coupling system. A vertical slab-track model with the rail longitudinal thermal stress is established. The natural vibration characteristic of the track under the influences of the rail longitudinal stress distribution has been calculated individually. The changed vibration modal function and frequency of track are used in calculating the dynamic response of vehicle-track coupling model. It can be seen from the dynamic responses that vibration frequency is shifted and amplitude peak is enhanced by thermal stress. In this paper, the digital features are extracted from the responses of wheelset and rail in time and frequent domain, which are used as training samples in SVM. Then, the rail longitudinal stress can be estimated with the prediction model. The numerical simulation results indicate that, by utilizing the train as the excitation source of the dynamic system, the rail longitudinal stress can be estimated with measurable response of wheel and rail at an acceptable accuracy.