Electromagnetic measurements and numerical simulation in order to optimize the performance of an EMAT sensor in magnetic media

Walaszek, Henri; Centre Technique des Industries Mecaniques; France

Clausse, B.; CEA, LIST; France
Walaszek, H.; CETIM; France

ID: ECNDT-0334-2018
Session: EMAT
Room: G2
Date: 2018-06-13
Time: 14:10 - 14:30

CETIM develops EMAT (Electromagnetic Acoustic Transducers) sensors that enable contactless generation and detection of compression and shear waves in electrically conductive or magnetic materials. The ultrasonic radiation sources generated by EMAT exploit the Lorentz force in non-magnetic conductive materials, to which are added magnetization and magnetostriction phenomena when the controlled material exhibits magnetic behavior. A limitation to the use of EMAT sensors lies in the fact that the amplitudes of the ultrasonic echoes transmitted and received are small compared to those of the piezoelectric sensors. CETIM and CEA LIST have therefore pooled their skills to optimize the design of these sensors and improve their signal-to-noise ratio. Modeling and simulation work was carried out by the CEA LIST and experimental validation measurements were undertaken jointly with CETIM on a didactic EMAT probe. Thus, measurements of impulse currents of excitation and of dynamic magnetic flux were carried out on this sensor. The frequency spectra of the excitation current, the magnetic field, and the ultrasonic echoes obtained in different materials are compared and analyzed. These measurements are also compared with simulation results.