A Focusable and Reversible Sh Wave Electromagnetic Ultrasonic Transducer

Abstract

The invention relates to a focusable and commutating SH-wave electromagnetic ultrasonic transducer. The ultrasonic transducer comprises a housing 1, a wear-resistant layer 5, a first periodic permanent magnet 6, a second periodic permanent magnet 8 and a runway type AC coil 7. A focusing operating lever 2 is connected to the housing 1 through a revolute pair. An upper gear of an I-shaped gear 3 is fixedly connected to and meshed with a gear of the focusing operating lever 2. A cone gear 12 is connected to the I-shaped gear 3 through a revolute pair. A lower gear of the I-shaped gear 3 is meshed with a cylindrical gear 9. The cylindrical gear 9 is connected to the cone gear 12 through a revolute pair. The cone gear 12 is connected to the focusing operating lever 2 through a revolute pair. A steering operating lever 4 is connected to the cone gear 12 through a revolute pair. The housing 1 is connected to the steering operating lever 4 through a revolute pair. Through changing an included angle of a PPM pair and two straight leads of a runway-type alternating current coil 7 below the PPM pair, SH-wave focusing is realized. Through integral rotation of the PPM pair and the runway-type alternating current coil 7 below the PPM pair, SH-wave steering is realized so that SH-wave sector-scanning at a certain angle is realized.

Description

technical field [0001] The invention belongs to the technical field of nondestructive testing, and in particular relates to a focusable and reversible SH wave electromagnetic ultrasonic transducer, which is suitable for electromagnetic ultrasonic flaw detection of non-ferromagnetic metals. Background technique [0002] An ultrasonic transducer is a device that can realize energy conversion between mechanical energy and acoustic energy. Based on different excitation and receiving principles, there are currently two main types of ultrasonic transducers in the field of nondestructive testing: one is a piezoelectric transducer (Piezoelectric Transducer, PZT for short) based on the piezoelectric effect, and the other is based on the Lorentz Electromagnetic Acoustic Transducer (EMAT for short) based on the mechanism of force and magnetostrictive force. [0003] Electromagnetic ultrasound is an emerging technology in the field of nondestructive testing. Compared with traditional p...

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Problems solved by technology

[0008] In traditional PPM EMAT that excites SH waves, its PPM pair is usually arranged parallel to the two straight wires of the racetrack-shaped AC coil below it, which has structural symmetry, so that SH waves will be excited in two opposite directions at the same time, namely The two-way excitation of the SH wave is realized, so it is easy to introduce the interference of the end reflection echo; in addition, the PPM pairs are arranged in parallel, which cannot achieve the acoustic energy focusing in a local area, and the two semicircular wire parts of the racetrack AC coil It is also easy to introduce interference from non-SH mode guided waves, resulting in a decrease in the signal-to-noise ratio of the transducer, which affects the identification and interpretation of defect signals

[0009] When the SH wave excited by the traditional PPM EMAT vibrates and propagates along the waveguide in the full thickness of the test specimen, as the propagation distance increases, the energy of the SH wave will continue to attenuate due to scattering, transmission and absorption, making the The energy density is reduced, which affects its defect detection and identification capabilities, and reduces the effective detection range of SH wave single excitation

[0010] The traditional PPM EMAT that excites the SH wave is difficult to change the direction of the PPM pair and the AC coil below it, so it is difficult to realize the sectoral scanning of the SH wave within a certain detection range

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