Magnetic test method

Please refer to the figure for the method’s principle of operation. The magnetic field source, with its function performed by a permanent magnet, creates a magnetic flux in the tested object. Should there be no defects, magnetic field appears inside the tested ferromagnetic object almost entirely, and the magnetic field sensor, it is depicted as a Hall sensor in the figure, detects the absence of magnetic field. Where there is a defect, the magnetic properties of the tested object change locally, and the magnetic field that strives to bypass the area of low magnetic permeability, surfaces partially and creates stray fields in the process. These fields are detected by the magnetic field sensor. Thus, data of magnetic field in the area where the sensor is located indicate the presence of a defect thereunder.