Ultrasonic detection of surface-breaking railhead defects

On the UK rail network, changing usage patterns have led to rolling contact fatigue (RCF) on the railhead being an increasing problem, andfirequent testing for such defects is essential. Existing systeinsfior detecting defects are limited in speed (<30 mph) and accuracy (> 5 mm). We are currently working on novel ultrasonic methods qf detecting RCF, designed to lift many of the speed limitations andl or significantly improve accuracy and resolution. A noncontact pitch-catch pulsed ultrasonic system comprising two electromagnetic acoustic transducers (EMATs) generating and detecting Rayleigh-like waves has the potential to operate at high speed, thus improving network inspection coverage. Phased array ultrasonic techniques arc being, signed to improve imaging and characterisation of the dc,fects on sections of rail have defects. A set of simulated de been machined, including half-face slots machined normal to the railhead surface, clusters of angled slots, and pocket defects more typical of real deftcts. The techniques have been tested on these rails and their potentialjbr use on the rail network is discussed.