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Article

Variation of Magnetic Memory Signals in Fatigue Crack Initiation and Propagation Behavior

1
College of Mechanical and Transportation Engineering, China University of Petroleum-Beijing, Beijing 102200; China
2
CNOOC Research Institute, Beijing 100029, China
*
Author to whom correspondence should be addressed.
Metals 2019, 9(1), 89; https://doi.org/10.3390/met9010089
Received: 13 December 2018 / Revised: 9 January 2019 / Accepted: 11 January 2019 / Published: 16 January 2019
To monitor fatigue crack initiation and propagation, and to judge the fatigue damage status of ferromagnetic material, fatigue bending tests of four-point single edge notch bend (SENB4) specimens were carried out. Metal magnetic memory signals were measured during the whole fatigue process. The results showed that the fatigue process could be divided into four stages by observing the morphology of the fracture surface. With the increase of fatigue loading cycles, the tangential component of the magnetic field (Hx) and the normal component of the magnetic field (Hy) increased. At the notch Hx presented a “trough” shape and had a maximum value at the midpoint, while Hy at the notch rotated clockwise around the midpoint. Compared with the tangential characteristic parameters, the variation of normal characteristic parameters (i.e., maximum gradient value of Hy (Ky-max) and the variation range of Hy at the notch (∆Hyn), with the fatigue loading cycles are more similar to the variation of fatigue crack length with loading cycles), both Ky-max and ∆Hyn had a good linear relationship with fatigue crack length. Plastic deformation accumulated on both sides of the fatigue crack, and metal magnetic memory (MMM) signals measured from the specimens were able to indicate the location of the fatigue crack and the variation of the fatigue crack length. Furthermore, the distribution of magnetic signals was analyzed according to the theories of stress magnetization and magnetic flux leakage. View Full-Text
Keywords: X80 steel; metal magnetic memory testing; fatigue crack; stress magnetization; plastic deformation X80 steel; metal magnetic memory testing; fatigue crack; stress magnetization; plastic deformation
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MDPI and ACS Style

Zhou, W.; Fan, J.; Ni, J.; Liu, S. Variation of Magnetic Memory Signals in Fatigue Crack Initiation and Propagation Behavior. Metals 2019, 9, 89. https://doi.org/10.3390/met9010089

AMA Style

Zhou W, Fan J, Ni J, Liu S. Variation of Magnetic Memory Signals in Fatigue Crack Initiation and Propagation Behavior. Metals. 2019; 9(1):89. https://doi.org/10.3390/met9010089

Chicago/Turabian Style

Zhou, Wei, Jianchun Fan, Jinlu Ni, and Shujie Liu. 2019. "Variation of Magnetic Memory Signals in Fatigue Crack Initiation and Propagation Behavior" Metals 9, no. 1: 89. https://doi.org/10.3390/met9010089

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