Study on the early fatigue damage evaluation of high strength steel by using three components of metal magnetic memory signal

Abstract

In this paper, the early fatigue damage evaluation of high strength steel was discussed. By using CH-3600 Gauss meter and three channel metal magnetic memory probe, the three components of MMM signal, including Bx, By and Bz signals, were collected, and a non-ferromagnetic three-dimensional platform was employed. Based on the high cycle fatigue test, the Bx, By and Bz signals, corresponding to different fatigue cycles, were collected. The results show that the lift-off of probe is important for the characteristic parameter of Bx, By and Bz signals (defining Bxave, Byave and Kz, respectively), as lift-off of probe increases, the characteristic parameter decreases fast and tends to be stable gradually. As fatigue cycle increases, the changes on Bxave, Byave and Kz are very similar, but compared with Byave, the Bxave and Kz change more smoothly and are more suitable for evaluating the early fatigue damage. As fatigue stress increases gradually, the values of Bxave-2 and Kz-2 increases linearly. At last, the experimental results are explained on the base of grain slip and magnetostriction effect, and the interaction of magnetic domain, dislocation and the internal stress is considered to be as the main reason for the change of Bxave and Kz.