A Contactless Approach to Monitor Rail Vibrations

This article presents a numerical formulation and the experimental validation of a noninvasive method to determine the axial load in continuous welded rail. A general finite element model of unrestrained rail segments under varying boundary conditions and axial stresses was formulated to predict the natural frequencies of vibration. The model was then validated experimentally by testing a 2.4 m-long rail under compressive loading. During the experiment, the rail was subjected to the impact of an instrumented hammer and the triggered vibrations were recorded with conventional accelerometers and a high-speed camera. The videos recorded with the camera were processed using the phase-based motion magnification technique to extract the frequency as well as the mode-shapes of the test specimen. The results proved that the information extracted from the video match well with those obtained with the conventional accelerometers. The findings presented in this article demonstrate the robustness of image processing techniques to identify modal characteristics of the tested rail. This enables the determination of the stress based on the numerical simulation.