Development of the New Nondestructive Material Degradation Evaluation Method Using the Low Frequency Excitation Magnetic Sensor Under the DC Magnetic Field

在铁基结构材料的疲劳评价中，采用饼状线圈的电感法是有效的。由于涡流不能通过表皮效应渗透到试件内部，因此这种方法不能评价试件的内部疲劳。在这种方法中，疲劳评估的准确性取决于试样的表面状况。在本研究中，我们采用脉动张力疲劳。我们取得了以下成果：低碳钢试样脉动拉伸疲劳的检测最初是采用电感法，激励频率为10kHz。我们尝试使用低频激励的电感法和使用钕磁铁的直流磁化法来提高灵敏度。该方法可以评估试样的脉动拉伸疲劳，而不考虑试样的表面状况。

In the fatigue evaluation of an iron-based structural material, the inductance method that uses a pancake-type coil is reported to be effective. This method cannot evaluate the inside fatigue of a specimen because the eddy current does not penetrate into the inside of a specimen through the skin effect. In this method, the accuracy of the fatigue evaluation depends on the surface condition of a specimen. In this study we applied pulsating tension fatigue. We achieved the following results. The detection of pulsating tension fatigue of specimens made of low carbon steel was originally possible by the inductance method which used 10kHz as a excitation frequency. We attempted the improvement of the sensibility using the inductance method excited in the low frequency together with the dc magnetization method that used Nd magnets. This method could evaluate pulsating tension fatigue of a specimen irrespective of the surface condition.