Ultrasonic Guided Wave Testing System using Electromagnetic Acoustic Transducers and the Application in Steel Pipes with Inner Corrosion

The aim of this work presented here is to demonstrate that the ultrasonic guided wave testing system using electromagnetic acoustic transducers (EMAT) is able to detect the inner corrosion of steel pipes. Both excitation and reception of the guided wave is carried out with EMAT in this system, promising the practical guided wave testing system. First of all, theoretical background of the guided wave and EMAT are reviewed. Dispersion curve of the group velocity are calculated from a set of characteristic equation. Principle of the guided wave excitation and reception with EMAT is also discussed. Second, three dimensional guided wave testing simulator is developed and details of the guided wave testing system is delivered. Finally, simulation and experimental results are compared and discussed. Steel pipes with artificial inner corrosion are tested with torsional guided wave mode and the sensitivity to the corrosion is evaluated.