EMAT based on Halbach magnet configuration for detecting faraway defects in long metal plates

ハルバッハ磁石構造の電磁超音波による長尺金属板の遠方探傷技術

山口 智彦 ; Mihalache, O. 

Yamaguchi, Toshihiko; Mihalache, O.

The paper reports on the development of a new EMAT sensor using a configuration based on Halbach magnet to detect defects in long metallic plates, up to 3.5 meters. Optimizations of the EMAT sensor, related to Halbach magnet configuration and others, enable greatly increase the signal-to-noise ratio of the defects. The defects are located on the opposite side of the surface from the EMAT sensor position, with depths up to 20% of plate thickness and at much greater distances (meters) from the sensor, in a frequency range below 1 MHz. Experimental measurements confirm the feasibility of the method, and the new EMAT opens up the possibility of faraway detection of defects in the meter range, as compared with the standard EMAT method until now limited to a 0.10.4 m applicability in metallic plates.