Detection of rail stress-free temperature via thermally induced micro-g vibrations for structural health monitoring and buckling risk mitigation

ÇEÇEN F., SALTAN M.

Measurement: Journal of the International Measurement Confederation, cilt.269, 2026 (SCI-Expanded, Scopus)

Özet

Rail Thermal Buckling (RTB) is an escalating safety concern as climate change drives extreme rail temperatures, making accurate determination of the rail stress-free temperature (SFT) essential. This study introduces a novel, non-destructive approach that determines SFT from thermoelastic micro-g vibrations measured by low-noise seismic accelerometers. Unlike existing methods that require rail cutting, finite-element modelling (FEM), or site-specific calibration, the technique integrates synchronized acceleration and temperature data with two complementary analyses: (i) frequency-domain spectrogram and cross-power spectral density (CPSD) to track the onset of global lateral resonance (GLR), and (ii) amplitude-domain band-pass filtering with block-RMS evaluation to identify the corresponding thermal transition. Pilot field measurements on continuously welded rail (CWR) revealed a stable GLR frequency of about 5.87 ± 0.08 Hz while rail temperatures increased from roughly 12 °C to 40 °C. The appearance of coherent GLR peaks coincided with the shift from tensile to compressive thermal forces, providing a physically interpretable cue for SFT. Consistent estimates were obtained at two independent sensor sites, differing by only 0.4 °C (≈2.4 %), with SFT values of 16.6 °C and 17.0 °C. This study also introduces the first documented observation of thermally induced GLR excitation in railways without service-load input, thereby establishing a new Operational Modal Analysis (OMA) excitation mechanism. The results demonstrate that micro-g vibration cues can serve as practical, non-destructive indicators for real-time, remote structural health monitoring (SHM) and proactive RTB-risk mitigation.