Observation of magnetic flux density around fatigue crack tips in bearing steel using an SHPM with a three-dimensional small-gap probe

• Published in: International journal of fatigue 2012-06, Vol.39, p.38-43
• Main Authors: Kida, Katsuyuki, Santos, Edson Costa, Honda, Takashi, Koike, Hitonobu, Rozwadowska, Justyna
• Format: Article
• Language: English
• Subjects: Applied sciences; Crack propagation; Cracks; Density; Exact sciences and technology; Fatigue; Fatigue crack growth; Fatigue failure; Gallium arsenide; Magnetic fields; Magnetic flux; Magnetic flux density; Mechanical properties and methods of testing. Rheology. Fracture mechanics. Tribology; Metals. Metallurgy; Non-destructive method; Scanning Hall-probe microscope; Steels; Stress intensity factor
• ISSN: 0142-1123; 1879-3452
• DOI: 10.1016/j.ijfatigue.2011.05.013

► We developed a scanning Hall probe microscope (SHPM) equipped with a GaAs film sensor. ► We succeeded to observe fatigue cracks at room temperature in air while they were growing. ► One of the important findings regarding the magnetic fields is that the magnetic flux density decreases during crack growth. ► The other is that polarization of the magnetic field occurs ahead of the fatigue cracks. Fatigue failure of steel occurs when cracks form in a component and continue to grow to a size large enough to cause failure. In order to understand the strength of a steel component it is important to locate these cracks. We developed a scanning Hall probe microscope (SHPM) equipped with a GaAs film sensor and observed fatigue cracks at room temperature in air while they were growing. In this paper we report two important findings regarding the magnetic field properties: a decrease in the magnetic flux density at the early fatigue stage and the polarization of the magnetic field ahead of the fatigue cracks occurring during crack growth.