New Developments Of Electromagnetoacoustic Transducers (review)

Abstract

проведен анализ информационных источников по вопросам исследований и разработки электромагнитно-акустических преобразователей. Установлено значительное расширение номенклатуры эма преобразователей различного назначения как для портативных, так и для автоматических средств измерений, контроля, диагностики и оценки физико-механических свойств материалов. Библиогр. 14, рис. 9.

Increasing the Efficiency of the Surface-Mounted Ultrasonic Electromagnetic-Acoustic Transducer on Account of the Magnetic Field Source

“…where k is a coefficient that depends on the electrical, magnetic and elastic characteristics of the material tested; I is the strength of the high-frequency current in the EMAT inductance coil, А; В is the value of the normal induction component of a permanent polarizing magnetic field in the surface layer of the object of control (OC), Т; h is the distance from EMAT to surface of OC, mm; R is the average size of the highfrequency inductor of the transducer, mm. Direct combined overhead EMATs are most often used for portable devices that allow exciting and receiving shear ultrasonic pulses, which are characterized by increased sensitivity when detecting defects [7,16]. For these devices, it is necessary to ensure the maximum possible induction of the magnetic field at a considerable distance (5 -60 mm) from the surface of the ferromagnetic OC to the source of the magnetic field.…”

“…An increase in the normal component of magnetic field induction is also possible due to the use of a magnetic (ferromagnetic) screen [7,16]. Consider the EMAT magnetic system with a magnetic shield (position 1 in Fig.…”