Direct Monitoring of In-situ Rail Fastener Vibrations from a Moving Train with Laser Doppler Vibrometer*

Monitoring the vast number of rail fasteners across a rail network necessitates efficient monitoring technologies and autonomous data analytics. To fill the gap in direct monitoring of degraded yet unbroken rail fasteners, this paper develops a novel train-borne laser Doppler vibrometer (LDV) technology that can contactlessly measure the vibration of rail fasteners under the excitation of a moving train. Utilizing short-duration and high-sampling-rate signals measured on each fastener, a data-driven method combining clustering and statistics is developed to assess the overall behavior of fastener groups within each track section and to detect abnormal individuals. The practicality and effectiveness of this technology are demonstrated through real-world testing on an operational rail line in the Netherlands, where hundreds of rail fasteners are measured at train speeds up to 75 km/h. The train-borne LDV technology enables efficient and informative monitoring of transportation infrastructures. The developed method allows for early defect detection and both global and detailed assessments, thus facilitating condition-based maintenance.