Sensitivity to Axial Stress and Temperature of Local Resonances in Rails

Abstract

Measuring rail thermal stresses or rail neutral temperature (RNT) in continuous welded rails (CWRs) is a challenging task for the railroad industry, especially in a nondestructive and nondisruptive manner. This paper examines the potential of local resonances for thermal stress measurement in rails. Local resonances associated with zero-group velocity (ZGV) and cutoff frequency points usually demonstrate sharp resonances in amplitude spectra, which can be utilized for Nondestructive Evaluation (NDE) and Structural Health Monitoring (SHM), and we previously reported their existence in rails. In this study, we promote local resonances by bonded piezoelectric elements on a short rail sample. Two tests were performed: (i) the sample is subjected to stepwise increasing uniaxial compressive loads in a constant temperature environment, and (ii) the same sample is free to expand and subjected to rising temperatures in an oven. By measuring local resonant frequencies, we quantified the sensitivity of the resonant frequencies to axial stress and temperature. The results show that appreciable sensitivities of the local resonances are found under varying stress and temperature levels and can be utilized for in-situ rail thermal stress determination.