Metal Magnetic Memory Testing (MMMT) technique has been extensively used as a qualitative method to test the position of possible damages in ferromagnetic metal structures. The magneto-mechanical effect and the leakage of magnetic field caused by the discontinuity of structure are largely regarded as two of the critical factors influencing the MMMT signals. In this paper, experiments and calculations were carried out to explore the influences of discontinuous structures on the MMMT signals. Two types of specimens fabricated with different defects were stretched by a tensile testing machine. Leakage magnetic field signals above the specimens were measured by a fluxgate-based magnetometer. Magnetic charge distributions around the discontinuous structures were calculated based on a reconstruction algorithm using the measured leakage magnetic field signals. The magnetic charge distribution patterns around two different discontinuous structures were compared and some characteristics are summarized.
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