Bending-mode magnetostriction sensor

Abstract

The invention discloses a bending-mode magnetostriction sensor. The bending-mode magnetostriction sensor comprises a ferromagnet cylinder shell, a flexible printed coil, a permanent magnet circuit and the like. The ferromagnet cylinder shell sleeves a micro round tube, epoxy resin is adhered to the surface of the micro round tube, and the ferromagnet cylinder shell is magnetized by specific magnetic fields provided by the permanent magnet circuit to form static magnetic field distribution beneficial to bending mode excitation. Alternating-current signals are transmitted into the flexible printed coil to generate dynamic magnetic fields, section displacement distribution of the ferromagnet cylinder shell is in conformity to a section vibration form of a bending mode, and finally, bending-mode ultrasonic guided waves are formed in the micro round tube. Through adjustment of a mounting mode of a permanent magnet in the permanent magnet circuit, the bending-mode ultrasonic guided waves with different orders can be excited by the sensor.

Description

technical field [0001] The invention relates to a bending mode magnetostrictive sensor, which belongs to the technical field of electromagnetic acoustic sensors, and can excite and receive bending mode ultrasonic guided waves in a fine round tube. Background technique [0002] There are axisymmetric and non-axisymmetric guided wave types in circular tubes. The former is divided into longitudinal and torsional modes, and the latter has only bending modes. In the field of ultrasonic non-destructive testing, reports on the application of torsional and longitudinal modes for defect detection and location have been common. Due to the complexity of the bending mode wave structure, it is difficult to design a dedicated sensor to excite pure bending mode ultrasonic guided waves. Therefore, there are few studies on the application of bending mode ultrasonic guided waves for nondestructive testing in engineering practice. In "Guided waves by axissymmetric and non-axissymmetric surfa...

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Problems solved by technology

In "Guided waves by axissymmetric and non-axissymmetric surface loading on hollow cylinders", J.L.Rose and other scholars used comb transducers to excite bending mode guided waves to detect pipes, which proved the possibility of bending mode detection defects. And it is proposed that the bending mode signal reflected from the defect may contain the circumferential position information and defect size information of the defect; Y.Y.Kim et al. used topology optimization algorithm in "The optimal design and experimental verification of the bias magnet" to design a The magnetic circuit of the sensor that can excite relatively pure F(1,2) mode ultrasonic guided waves, but the structure is relatively complicated and not suitable for practical applications

The above studies are limited to large-diameter pipes, and cannot be directly transplanted into micro-tube structures

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