Local resonances for rail neutral temperature estimation

In-situ thermal stress determination in structures is a challenging experimental mechanics task, especially if it requires a nondestructive approach. Thermal stress measurement and management of continuous welded rail (CWR) have become more important for railroad maintenance. Local resonances formed by zero-group velocity (ZGV) and cutoff frequency points usually demonstrate sharp resonance peaks in frequency spectra, which can be utilized for nondestructive evaluation (NDE) and Structural Health Monitoring (SHM). This paper examines the potential of the local resonances to provide an estimation of axial stress in rail structures. The local resonances are generated by bonding a piezoelectric element on the rail samples. A 610-mm rail sample was tested, and different axial stress levels were applied by an MTS tensile-compression machine and by measuring the local resonance signature in selected frequency bands to study sensitivity to axial stress of local resonances. The results show that appreciable sensitivities of the local resonances are found under varying stress levels and can be further utilized for in-situ thermal stress determination for rails.