Guided waves are now used extensively in industrial NDT, mainly for long range testing of pipelines for general wall loss and cracks. EMATs are well suited to generating guided waves in the form of both Lamb and Shear Horizontal waves and have been applied in defect detection in the past. Here the intention is to better understand the propagation of guided waves generated by EMATs that travel circumferentially around a pipe and their interaction with defects. This will enable the current ultrasonic pipe screening tools of pipe scanners with limited circumferential access to move from a simple positive or negative test for corrosion towards a more quantitative measure of the radial extent and depth of corrosion patches. Such defects are not uncommon in difficult to access regions such as below pipe supports and in subsea applications. This is achieved by analysing the theoretical operation of the probes and modelling the transducer to obtain an accurate representation of the force distributions developed on the surface of the sample by the generation EMAT. Finite Element modelling of the ultrasonic waves propagating in the sample is then undertaken to develop an understanding of how the waves propagate and interact with defects of varying size and depth.
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