Development of an Axial Strain Measurement System for Rails

Abstract

Train derailments caused by buckled or broken rail continue to be both a safety and economic concern for North America’s railway industry. These track failures are often attributed to excessive axial stresses in continuous welded rail (CWR) caused by thermal stresses under daily or seasonal variations in temperature. Improved monitoring systems, with the capability of detecting axial stress in CWR, are needed. The distributed nature and long-distance measurement ranges offered by fiber-optic sensors (FOS) may offer a potentially optimal solution for rail stress monitoring. This paper investigates the ability of two FOS systems (based on Rayleigh and Brillouin backscatter) to measure axial strain in rails under various boundary and environmental conditions. The performance of three alternative fiber types, differing based on ruggedness and installation effort, were also tested in the interest of creating an optimized field monitoring system. The effect of temperature on strain measurements led to the development of thermal correction factors for each analyzer/fiber combination. The application of this monitoring system in the field was then explored using both systems on a CWR track in Ottawa, Canada.