Abstract
A lab-based laser-EMAT (Electromagnetic acoustic transducers) system has been developed to observe the ultrasonic surface wave propagation and interaction with surface breaking defects on the sample rail head surface. The frequency-wavenumber dispersion curves of the dominant surface wave modes were determined using 2D-FFT method based on the measurements of the out-of-plane displacement of the surface wave. A complete picture of the ultrasonic surface wave on the sample surface over time was reconstructed with exceptionally high spatial and temporal resolution. Despite the curvature of the rail head, the ultrasonic surface guided wave propagating down the rail is found to have similar properties to Rayleigh waves by direct comparison to those observed on flat samples using the same technique.