A variable-mode magnetic concentrator Lamb wave electromagnetic-acoustic transducer

Abstract

The invention discloses a variable-mode magnetic concentrator-type Lamb wave electromagnetic acoustic transducer, which comprises a neodymium-iron-boron magnet, a class A magnetic concentrator, a class B magnetic concentrator, and a flexible circuit board. Double layer variable pitch return coil. Place the coil on the surface of the aluminum plate, and the upper surface of the magnetic concentrator and the NdFeB magnet are attracted and fixed directly above the coil. When a class A magnetic concentrator is selected, the lower surface of the magnetic concentrator is controlled to be placed on the center of the coil with a distance of d 1 On the coil, the main mode that can be excited is A 0 Modal guided wave; when the class B magnetic concentrator is selected, the lower surface of the control magnetic concentrator is placed on the center of the coil with a distance of d 2 On the coil, the excitable main mode is S 0 Modal guided waves. Through the frequency characteristic test, it is verified that the developed variable-mode magnetic concentrator Lamb wave electromagnetic acoustic transducer has good frequency response characteristics, and at the same time, the rationality of the transducer design is verified, and the structural health of the plate structure is realized. monitor.

Description

technical field [0001] The invention is a variable-mode magnetic concentrator type Lamb wave electromagnetic acoustic transducer, which belongs to the field of ultrasonic non-destructive testing, and can only replace different magnetic concentrators without changing a series of parameters such as coils, magnets and excitation frequencies. In this case, guided waves of different modes are excited in the plate structure. Background technique [0002] Sheet metal structures are widely used in aerospace, civil engineering, machinery and other fields. In the process of production and use, the metal plate structure will inevitably be damaged, which greatly reduces the service life of the material. In order to ensure the safety of the metal plate structure, it is necessary to carry out non-destructive testing on the metal plate. In the traditional ultrasonic testing technology, the piezoelectric ultrasonic technology is an important part of the traditional ultrasonic testing tech...

AI Technical Summary

Problems solved by technology

S 0 Modal EMAT aspect present, the omnidirectional S 0 The modal EMAT has received more attention and research. Wilcox et al. established the theoretical model of the omnidirectional EMAT in the plate. Based on the Lorentz force mechanism, the annular compactly wound helical coil coil is designed and manufactured to effectively excite the EMAT in the plate. S with the same directivity within 360° 0 Modal EMAT, but the transducer cannot be excited by a single mode

Currently, it is possible to simultaneously excite a single S in the plate 0 Modal vs Single A 0 Rare reports on modal Lamb wave electromagnetic acoustic transducers

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