PREDICTING AXIAL STRESS STATE IN CONTINUOUSLY WELDED RAIL USING IMPULSE-GENERATED VIBRATION MEASUREMENTS

Continuously welded rails are connected without stress relief joints and, thus, thermally induced rail movement is constrained, which can result in the development of excessive axial stress and risk of rail failure. Nondestructive testing (NDT) methods that estimate in-place rail stress state or rail neutral temperature are desired. Some methods have been developed, but none satisfy the requirements for ideal monitoring in practice. We propose an NDT technique based on impulse-generated vibration, seeking high-frequency rail vibration resonances whose frequency maintains a consistent correlation with rail axial stress/strain across different temperatures, stress states, and rail support conditions. Rail temperature, axial strain, and vibration data were collected from an active Class 1 commercial rail line over a period of nearly two years. The frequencies of four consistent and clear resonance modes of the rail were monitored. One of the identified modes demonstrates a unique linear relation with axial strain across a range of temperatures and stress states at each of the two measurement locations. The developed linear relations were used to predict in-place strain and rail neutral temperature with acceptable accuracy across all the measurement data, although each test location exhibits a unique relation.