Guided Wave Propagation in a Plate Edge and Application to NDI of Rail Base

The analysis of guided wave propagation in a plate edge can be useful for some applications, such as for the inspection of the rail base. Here guided waves generated by a laser beam hitting, on the inclined surface, a solid media with trapezoidal cross-section have been studied. We have found that, for the geometry investigated, two guided waves propagate along both free surfaces of the plate, with same velocity and frequency. The analysis of the trajectories of the two material points, due to waves propagation, shows that the wave packets can be identified as Rayleigh waves. The presence of S₀ Lamb mode, with low frequency and low amplitude, has been revealed too. As an example of a possible application, the detection of pitting corrosion in the rail base was investigated experimentally and numerically. Results prove that even if it is not possible to access the bottom of the rail, a remote NDE setup working on the upper surface may potentially be used to identify pitting. The numerical method was useful for a better understanding of the phenomenon, thus allowing the optimization of the experimental setup.