Characterization of Work Hardened Layers in Rails Available to Purchase

As part of an infrastructure subject to increased magnitude and frequency of loads, railroad track systems require regular inspection to assure high reliability for the safety of the public and passengers and the safe and efficient movement of goods. Unattended work hardened layers on the surface of the rails are operational hazards due to the inevitability of rolling contact fatigue cracks. A novel method utilizing the higher order surface waves, also called as Sezawa waves, has been used to detect and characterize the work hardened layer in rails. The technique involves generating Sezawa waves using contact ultrasonic transducers and monitoring the cut-off frequency of these waves. Results from hardness tests and metallographic analyses on the work hardened layers are also reported. The tests using the Sezawa wave technology demonstrated the ability to interrogate and resolve traffic-hardened layers in the depth ranges of 0–1 mm, 1–3 mm, and 4–7 mm. The minimum Brinell Hardness (HB) gradient, between the hardened layer and underlying rail, required to support Sezawa wave generation was also investigated and determined to be greater than 20 HB.