Plane Stress Measurement Using Three Angles Magnetic Barkhausen Noise Method

Magnetic Barkhausen noise stress measurement method has the outstanding advantages of high sensitivity, high repeatability, in-situ nondestructive, convenient and efficient, low cost and so on. It has great application prospects in residual stress, structure load stress, concentration stress and damage risk evaluation. The traditional magnetic Barkhausen stress measurement is the unidirectional method, which can only obtain the normal stress in the measured direction. The circumferential measurement method developed in recent years realizes the measurement of the direction and amplitude of principal stress of plane stress state, but it needs to scan the magnetic Barkhausen distribution on 360°, causing a low testing efficiency. In order to improve the measurement efficiency, a method of measuring plane stress by triangulation magnetic Barkhausen is proposed, and the influence of angle selection on accuracy is analyzed. Moreover, a Bayes-calibration method based on multi-dimensional features reconstruction of uncertainty metric space is proposed in order to reduce the calibration uncertainty. The experimental results reveal that, when the stress is greater than 50 MPa, using three testing angles with an interval of 60°, the amplitude error of principal stress is less than ±10 MPa and the direction error is within ±5°. Using the Bayes-calibration model, the amplitude error can be further reduced to less than ±5 MPa, and the ±5° error band of direction measurement can be extended to the low stress area of 40 MPa. This method lays a foundation for using the magnetic Barkhausen to efficiently and accurately measure stress in engineering.