Evaluation of Stress and Stress Concentration Degree Based on the Online Piezomagnetic Measurement

The goal of this research is to correlate the piezomagnetic field with the stress and the stress concentration degree of ferromagnetic steels. Specimens of X80 steels were machined into smooth plates with circular holes in the center and tensile tests were carried out to detect the online piezomagnetic field on the surface of defective specimens. The relationship between the distribution of the stress and the distribution of the piezomagnetic field components was systematically investigated. Compared with the normal component and its gradient, the tangential component showed a better correlation with the distribution of the stress. A piezomagnetic parameter was defined to characterize the abnormal changes of the tangential component around the defect. Quantitative algorithms were established to evaluate the stress concentration degree on the basis of piezomagnetic parameters. This research will be a supplement of stress evaluation methods based on magnetic measurement technologies.