Orthogonal differential flexible electromagnetic sensor for residual stress detection

Abstract

The invention discloses an orthogonal differential flexible electromagnetic sensor for residual stress detection. The sensor comprises a flexible substrate with a multi-layer structure; an excitation coil is arranged on a first specified layer of the flexible substrate; the excitation coil comprises one or more square-wave-shaped repeating units; detection units in one-to-one correspondence with the repetitive units are arranged on a second specified layer of the flexible substrate; and each detection unit comprises two orthogonally placed TMR elements. According to the orthogonal differential flexible electromagnetic sensor for residual stress detection, the TMR elements are used for replacing detection coils to serve as the detection units; the magnitude of a magnetic field is directly measured instead of the change rate of the magnetic field, and therefore when the internal stress of a material is detected, the sensitivity of the sensor will not be reduced along with reduction of the frequency; the excitation coil comprises one or more square-wave-shaped repetitive units, so that the horizontal part and the vertical part of the excitation coil are perpendicular to each other; and TMR signal changes on horizontal excitation and vertical excitation are opposite, the influence of the background magnetic field can be eliminated when the TMR signals are differentiated, and useful signals are increased.

Description

technical field [0001] The invention relates to the fields of stress detection and electromagnetic sensors, in particular to an orthogonal differential flexible electromagnetic sensor based on a TMR (Tunnel Magneto Resistance, tunneling magnetoresistance effect) element for residual stress detection. Background technique [0002] Residual stress occurs in the whole life cycle of metal components, and it is difficult to predict. Its size and state vary greatly with different processing and working conditions. The residual stress in the material will seriously affect its strength, hardness, fatigue and stability, reduce the service life, and cause brittle fracture and stress corrosion cracking in extreme cases; It can improve its tensile and anti-fatigue properties to prolong its service life. Therefore, on the one hand, the fatigue state of the material can be understood by detecting the residual stress and help prevent accidents; on the other hand, the effect of stress cont...

AI Technical Summary

Problems solved by technology

[0006] The technical problem to be solved by the present invention: Aiming at the problem that the detection sensitivity of the traditional electromagnetic sensor with the coil as the detection unit is greatly affected by the operating frequency and the background magnetic field leads to a low signal-to-noise ratio, an orthogonal differential flexible sensor for residual stress detection is provided. Electromagnetic sensor, the present invention uses TMR element instead of detection coil as detection unit, directly measures the magnitude of the magnetic field instead of measuring the rate of change of the magnetic field, so when detecting the internal stress of the material, the sensitivity of the sensor will not decline with the reduction of the frequency; the present invention encourages The coil includes one or more square-wave repeating units, so that the horizontal part of the excitation coil is vertical to the vertical part, and the TMR signal changes on the horizontal excitation and vertical excitation are opposite. The difference between the two can eliminate the influence of the background magnetic field and increase useful signal

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