| Metal magnetic memory testing is a new method of nondestructive testing, which can overcome the shortcomings of the other traditional nondestructive testing, so that the stress concentration zone in the steels can be quickly detected. This paper mainly studied on the evolution of residual magnetic field in the steels subjected to tensile stress by analyzing the experimental data.Firstly, the influence of earth magnetic field on metal magnetic memory technology was discussed. According to detecting the sample with different orientations, the measured results were compared. Then reverse loading test was carried out to investigate the reversal point on magnetic polarity of steel, and judge zero magnetic field on the specimen by the experiment phenomena, which laid the foundation for the follow-up study. Secondly, tensile tests of three different steels were carried out to measure the evolutions of the residual magnetic signals to investigate the relationship between magnetic field and stress in the tension test, and compare with each other. Additionally, the correlation between two components of magnetic signal was also studied. Based on previous study, the further research was carried out that the effect of loading process on magnetic signal. There were three kinds of loading programs, which were divided into repeated loading, cyclic loading and single loading, utilized to observe the magnetic variation and compare with that in tension test. Finally, experiments were carried out to study the magnetic field variation under the effect of stress history. The steels were stretched to the different strengthening degrees, then loaded step by step after demagnetization and measured the relationship between magnetic field and stress to discovered specific rules, which was explained by corresponding theory. Thus, this paper can be possible for the better application of metal magnetic memory technology in practical engineering to provide a theoretical and experimental basis. |
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