Analysis of surface defects using the ultrasonic Rayleigh surface wave

Surface defects, such as gauge corner cracking on the railway track can be a difficult class of defects for existing on-line non-destructive testing techniques to detect and size accurately at high speed. There are economic and safety benefits to have an accurate, fast and reliable NDT technique to detect such defects. The EMAT pitch-catch ultrasonic testing technique, using the Rayleigh surface wave, has been shown to be able to detect and size surface defects. The pitch-catch geometry also allows this technique to be used at high speed on-line NDT applications. This research has also identified a number of ultrasonic signal features that arise from the interaction between the surface wave and surface defects, such as: the non-linear laser generation effect, the signal enhancement effect, and the Rayleigh wave recovery effects. They can have potential NDT applications for detecting and sizing surface defects. The ferrite enhanced EMAT is able to generate similar ultrasonic surface waves to the conventional EMATs, in some cases, with higher generation efficiency and better stand-off performance. This research should be of interest to those in ultrasonic NDT community.... Mehr