Development of SH Wave Electromagnetic Acoustic Transducer (EMAT)

Yang, X.; Tagawa, Akihiro ; Ueda, Masashi ; Yamashita, Takuya; Otsuka, Yusuke*; Osafune, Kazunori*; Nishikawa, Masahiro*

This paper describes a new structure of horizontally polarized shear(SH) wave electromagnetic acoustic transducer(EMAT). The EMAT with a Halbach magnet structure shows a stronger magnetic flux density as well as ultrasonic sound pressure than that of an EMAT with a general periodic permanent magnet(PPM) structure. The measured magnetic flux density and the ultrasound directivity distributions for both the Halbach and the PPM structure EMATs are in excellent agreement with those expected form a simulation calculation. The above EMATs were also used for inspection tests of many artificial slits; and it is found that the Halbach one performs a better detectability than the PPM one.