Development of a Longitudinal Rail Stress Measurement Device

The continuous welded rails used in most of the United States lack expansion joints of any sort. This leads to a much smoother ride and a longer service life for rails and wheels, but also causes extreme temperatures to induce high stresses in these rails. In very warm conditions these stresses can incite sudden buckling of the rails, which is dangerous and difficult to predict. To alleviate these risks rail stresses need to be regularly monitored, but current practices are slow and labor intensive. This research develops a non-contact prototype apparatus designed to quickly measure longitudinal stress in rails. The measurement is performed by generating a Rayleigh wave along the surface of the web of the rail and analyzing the polarization of the Rayleigh wave some distance further down the rail. An evaluation of this measurement technique is performed on rails of varying age and surface condition in a lab environment. A set of guidelines is then established to ensure the successful recreation of these results in a field environment. From these guidelines, a 3D model is developed to aid in the construction process. Finally, a prototype is manufactured based on this design