Pulsed Electromagnetic Thickness Evaluation of a Ferro-magnetic Plate

EMAT (Electro-Magnetic Acoustic Transducer) is a non-contact transducer that generates and detects the ultrasonic waves in electrically conductive materials. EMATs can be designed to generate various wave modes such as a Rayleigh wave, a Lamb wave and a shear horizontal (SH) wave. As the coupling between the EMAT and the sample is electromagnetic, EMAT is relatively insensitive to a surface condition by which a piezoelectric ultrasonic signal can be affected. EMAT uses a combination of static and dynamic magnetic fields to convert electrical energy into acoustic energy. The dynamic magnetic field is produced by an electrical coil and the static magnetic field is induced by a permanent magnet which makes it difficult to inspect the steel material due to an immobility of magnetic interaction. The sample that will be examined within this paper is a ferro-magnetic material such as a carbon steel in order to consider the coupling of Lorenz force, Magnetization force and Magnetostriction force for an effective inspection of a metal loss or a corrosion detection for a nuclear component under a high temperature and radiation environment. The purpose of this study is to investigate the feasibility of a pulsed EMAT technology for an automated inspection of a carbon steel piping with no water