| 摘要 |
PURPOSE:To simplify an electric processing circuit while achieving a relatively high measuring accuracy in a curved surface and rugged surface, by a method wherein a low frequency alternating magnetic field is applied to a material to be measured to detect with a disturbance of a magnetic flux by a Barkhausen effect with a detection coil and a high frequency component of the detection signal thereof is used as a detection signal. CONSTITUTION:When a magnetic field is applied to a ferromagnetic body to be magnetized, the movement of a magnetic wall is caused in a magnetic domain of the magnetic body. But this movement is not necessarily even and continuous and hence, the magnetization proceeds by stages. So, an alternating magnetic field is applied to an material to be measured with a detection head 6 to detect changes in the magnetic flux associated with variations in the magnetization with a detection core 4 and a detection coil 5, whereby a quick fluctuation of a fine magnetic flux can be detected. The voltage detected with the detection coil 5 is of a wide band (audible frequency - several hundred Hz). In this case, as the component of a high range is easy to detect, only a component exceeding 100kHz is picked up with a filter 8 to be amplified. With the excited magnetic field set at about 100Hz, the magnetization can proceed so deep as to detect a stress at a substantial depth (about 1mm). |
