An improved design of lamb wave EMAT for A0 wave generation and enhancement

Abstract

Abstract A new structure of Lamb wave electromagnetic ultrasonic transducer (EMAT) is proposed in this work to suppress S0 mode Lamb wave (S0 wave) and enhance A0 mode lamb wave (A0 wave). The new EMAT consists of periodic magnet and meander-coil. Finite element models are established to analyze the static magnetic field and the excited ultrasonic signal. As a result, the local static magnetic field of the new EMAT is increased. S0 wave is suppressed obviously by new EMAT while A0 wave is enhanced significantly. Besides, the new EMAT structure is optimized. Finally, experiment has been performed on 2 mm thick aluminum. The experiment has verified that the amplitude of the A0 wave signal obtained by using new EMAT is increased by a factor of about 9.33. Besides, the experiment results have shown that the S0 wave obtained by using new EMAT is suppressed to be almost submerged in noise.