A review on non-destructive evaluation of rails: state-of-the-art and future development

Rails are systematically inspected for internal and surface defects using various non-destructive evaluation (NDE) techniques. During the manufacturing process, rails are inspected using automated optical cameras and eddy current sensing systems for any surface damage, while the presence of internal defects is assessed through ultrasonic inspection. Similarly, ultrasonic transducers and magnetic induction sensors have been extensively used by the rail industry for the inspection of rails in-service. More recently, automated vision techniques and hybrid systems based on the simultaneous use of pulsed eddy current probes and conventional ultrasonic probes have been introduced for the high-speed inspection of rail tracks. Other NDE techniques, such as electromagnetic acoustic transducers, laser ultrasonics, guided waves, and alternating current field measurement probes, are also under development for application in the rail industry. This paper comprehensively reviews NDE methodologies in use around Europe and North America for rail defect detection. This includes a detailed overview of the background theory and the techniques used to incorporate condition data into maintenance procedures. It also presents a review of the current state-of-the-art in NDE of railways coupled with a discussion of future developments and novel inspection methodologies in the field.