Study of an Omnidirectional Guide Wave Sensor Using an EMAT

Abstract

Nondestructive inspection of structures is important for ensuring the safety of the social infrastructure. Among them, the ultrasonic inspection method plays a role as a major technology. However, when examining a huge structure, the inspection time tends to be very long. Therefore, a system for transmitting and receiving ultrasonic waves in all directions from the ultrasonic sensor has been constructed. Several types of ultrasonic sensors using this concept have already been devised, but since the ultrasonic energy is dispersed in all directions, there is a problem that a sufficient detection performance cannot be ensured, especially when the thickness of the material to be inspected becomes thick. Therefore, we developed a highly sensitive omnidirectional ultrasonic sensor utilizing the resonance phenomenon of the ultrasonic wave propagating in the thickness direction. The omnidirectional ultrasonic system also consists of an electromagnetic ultrasonic transducer (EMAT) using a circular magnet. It is possible to inspect the plate thickness from 0.3 mm to 10 mm and the inspection range of the diameter of 300 mm around the sensor by the developed system. It is indicated that the developed system allows the highspeed inspection of huge structures.

Development of a novel omnidirectional magnetostrictive transducer for plate applications

“…Several different research groups have investigated multiple omnidirectional sensor system designs. The majority of them have reported that the probes are based on a sparse array of omnidirectional piezoelectric or electromagnetic acoustic transducer (EMAT) probes utilizing a shear horizontal or Lamb wave modes of guided waves [1][2][3][4][5][6][7]. Every sensor in these arrays is designed to send and receive guided waves in all directions.…”