Multivision System for High-Resolution Strain Measurement of Continuously Welded Rail

A continuous welded rail (CWR) is a critical component of modern rail systems, providing increased stability, improved passenger comfort, and reduced maintenance compared with jointed rails. However, the unique mechanical properties of CWR, particularly in the immovable zone where friction restricts longitudinal deformation, require accurate and continuous monitoring to prevent rail buckling or fractures. Despite the availability of various strain-monitoring technologies, including fiber Bragg grating sensors, strain gauges, and vision-based systems, these approaches have significant limitations in full-scale CWR applications. Challenges such as insufficient resolution for detecting minute strains and sensor-adhesion durability reduce the effectiveness of current strain-monitoring solutions. To address these limitations, we propose a high-resolution, vision-based biaxial strain measurement system specifically designed for CWRs. This system utilizes three microscopic cameras strategically positioned to capture detailed displacement data, allowing for accurate computation of biaxial strain through advanced image processing techniques. The proposed system was validated through both laboratory-scale and full-scale experiments and exhibited a minimum detectable strain of 1.5 µε under controlled loading conditions.