Torsional mode guided wave magnetostrictive sensor based on double-ring permanent magnet array

Abstract

The invention provides a torsional mode guided-wave magnetostrictive sensor based on a double-ring permanent magnet array. The sensor mainly comprises two symmetrical semi-ring sensor components which are connected and coated on the pipeline surface through an elastic fastener. Each semi-ring sensor component mainly comprises a double-row permanent magnet array, two ferrocobalt strips, detection coils, a rubber shell and an epoxy resin layer; the two ferrocobalt strips are pre-bent into an arc to adapt to an outer diameter of a tested pipeline, and two sides are fixed by a molding base; the detection coil is wound on the two ferrocobalt strips in a fixed spacing manner, and alternating current is introduced to form an alternating magnetic field along the length direction of the ferrocobalt strips; rectangular permanent magnets in the double-row permanent magnet array are adsorbed on the outer sides of the ferrocobalt strips in the same direction, and a static magnetic field along the width direction of the ferrocobalt strips is provided. Alternating current signals with a phase difference of 90 degrees are introduced into two groups of detection coils in the sensors, and direction controllable torsional mode guided-waves are generated to be used for pipeline defect detection.

Description

technical field [0001] The torsional mode guided wave magnetostrictive sensor based on the double-ring permanent magnet array belongs to the field of ultrasonic guided wave nondestructive testing technology. Its function is to excite and receive the torsional mode ultrasonic guided wave in a circular tube with a specific diameter. The sensing component can not only be disassembled and assembled on site, but also has the function of controlling the propagation direction of the torsional mode guided wave. Background technique [0002] Torsional mode ultrasonic guided waves are widely used in long-distance pipeline defect detection. Magnetostrictive sensors based on iron-cobalt alloy strips are the main sensor form for excitation and reception of torsional mode ultrasonic guided waves. The iron-cobalt alloy strip used in the traditional magnetostrictive sensor is biased and magnetized along its length direction, and the alternating magnetic field formed by the detection coil i...

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Problems solved by technology

However, this design cannot realize the control of the propagation direction of the guided wave. Although the bias magnetic field strength can be adjusted by the electromagnet, the current is easily fluctuated by the interference of the circuit, resulting in the instability of the bias magnetic field strength.

In addition, due to the heating problem of the coil, the current of the electromagnet should not be too large, and the strength of the bias magnetic field is limited, which will affect the excitation efficiency of the guided wave

In addition, the winding of the orthogonal winding coil on the iron-cobalt alloy strip is also complicated

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